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Decay resistance of slurry erominated wet-process high-density hardboard Hong, Hon-Min 1978

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SLOBBY DECAY RESISTANCE OF EROMINATED WET-PROCESS HIGH-DENSITY HARDBOABD b y HON-MIN jjaONG B.Sc., N a t i o n a l Chung-Hsing U n i v e r s i t y , 1972 A THESIS SUBMITTED IN PAfiTIAL FULFILLMENT OF THE REQUIREMENTS FOB THE DEGBEE OF MASTER OF FOBESTBY i n THE FACULTY OF GRJ*3>UATE STUDIES. (FORESTRY) ' we accept t h i s t h e s i s as c o n f i r m i n g t o the r e g u i r e d standard THE UNIVERSITY OF BRITISH COLUMBIA September, 1978 @ H-M. Hong, 1978 In p r e s e n t i n g t h i s t h e s i s in p a r t i a l f u l f i l m e n t o f the r e q u i r e m e n t s f o r an advanced degree at the U n i v e r s i t y o f B r i t i s h C o l u m b i a , I a g r e e that the L i b r a r y s h a l l make i t f r e e l y a v a i l a b l e f o r r e f e r e n c e and s t u d y . I f u r t h e r ag ree t h a t p e r m i s s i o n f o r e x t e n s i v e c o p y i n g o f t h i s t h e s i s f o r s c h o l a r l y p u r p o s e s may be g r a n t e d by the Head o f my Department or by h i s r e p r e s e n t a t i v e s . It i s u n d e r s t o o d that c o p y i n g o r p u b l i c a t i o n o f t h i s t h e s i s f o r f i n a n c i a l g a i n s h a l l not be a l l o w e d w i t h o u t my w r i t t e n p e r m i s s i o n . Department o f FORESTRY  The U n i v e r s i t y o f B r i t i s h Co lumbia 2075 Wesbrook P l a c e Vancouver, Canada V6T 1WS Date October 5, 1978 i i A8STBACT B i o d e t e r i o r a t i o n t e s t s w e r e done t o i n v e s t i g a t e t h e d e c a y r e s i s t a n c e p r o p e r t y o f s l u r r y b r o m i n a t e d w e t - p r o c e s s h i g h -d e n s i t y h a r d b o a r d . T h e a d v a n t a g e o f r e s i s t a n c e a g a i n s t d e c a y w i l l i n c r e a s e t h e m a r g i n a l e c o n o m i c s o f t h e b r o m i n a t e d b o a r d w h i c h was d e v e l o p e d i n i t i a l l y a s a f i r e - r e s i s t a n t m a t e r i a l s o n l y . N o n - b r o m i n a t e d and b r o m i n a t e d h a r d b o a r d s were e x a m i n e d , u s i n g a s o i l - j a r m e t h o d , f o r t h e i r r e s i s t a n c e t o d e c a y by f o u r b r c w n - r o t a n d two w h i t e - r o t f u n g i . S i x t y p e s o f h a r d b o a r d were u s e d ; f i b e r o n l y , f i b e r p l u s p h e n o l i c r e s i n , and f i b e r p l u s p o l y e t h y l e n i f f l i n e r e s i n , a s w e l l a s t h r e e b r o m i n a t e d c o u n t e r p a r t s f o r t h e s e t h r e e c o n t r o l t r e a t m e n t s . A l t h o u g h t h e i n f l u e n c e o f t h e a d h e s i v e on t h e r a t e s o f d e c a y was s m a l l , t h e p o l y e t h y l e n i m i n e r e s i n , w h i c h c o n t a i n e d h i g h amount o f n i t r o g e n c o m p o u n d , showed some s t i m u l a t o r y e f f e c t . B r o m i n a t i o n s i g n i f i c a n t l y i n c r e a s e d t h e r e s i s t a n c e o f h a r d b o a r d t o d e c a y by b r o w n - r o t f u n g i , a l t h o u g h t h i s r e s i s t a n c e c o u l d be r e d u c e d by l e a c h i n g t h e b r c m i n a t e d b o a r d i n c o l d w a t e r b e f o r e a t t a c k b y t h e f u n g i . I t i s p r o b a b l e t h a t t h e f o r m a t i o n o f b r o m h y d r i n s o f l i g n i n by b r o m i n a t i o n o f t h e h a r d b o a r d p r e v e n t e d t h e a t t a c k o f t h e h a r d b o a r d s by two w h i t e - r o t f u n g i . Among t h e b r o w n - r o t f u n g i , L e n z i t e s t r a b e a P e r s . e x F r , was t h e most s e n s i t i v e t o g r o w i n g on b r o m i n a t e d b o a r d . I t was a l s o f o u n d t h a t b r o w n - r o t f u n g i w e r e more a c t i v e i n d e c a y i n g b o t h n o n - b r o m i n a t e d a n d b r o m i n a t e d h a r d b o a r d w h i c h were i n i t i a l l y a t a m o i s t u r e c o n t e n t o f 8% c o m p a r e d w i t h 20%, U s i n g e i t h e r wet h e a t o r e t h y l e n e o x i d e , as s t e r i l i z a t i o n t r e a t m e n t s o f t h e b o a r d s , g a v e no i i i d i f f e r e n c e i n t h e s u b s e q u e n t d e c a y r a t e s o f n o n - b r o m i n a t e d b o a r d s by t h e b r o w n - r o t f u n g i . W i t h b r o m i n a t e d b o a r d s , t h e e t h y l e n e o x i d e t r e a t m e n t a p p e a r e d t o i n c r e a s e t h e i r s u s c e p t i b i l i t y t o d e c a y b y t h e s e f u n g i . T h e s o i l - j a r m e t h o d , m o d i f i e d f r o m &STM D 1 4 1 3 - 7 6 , p r o v e d t o be a s u i t a b l e t e c h n i q u e f o r e v a l u a t i n g t h e d e c a y r e s i s t a n c e o f h a r d b o a r d . T A B L E OF CONTENTS Page T I T L E PAGE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . i A B S T E A C T . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . i i T A B L E OF CONTENTS i v L I S T OF T A B L E S . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . v i i L I S T OF FIGURES v i i i ACKNOWLEDGEMENTS . . . . . . . . . . . . . . . . . . . . . , . . . . . . . . . . . . . . . . . . . . > X C h a p t e r I . INTRODUCTION 1 I I . L I T E R A T U R E SURVEY 4 1 . D e f i n i t i o n o f H a r d b o a r d . . . . . . . . . . . . . . . . . . . . . 4 2 . C h e m i c a l C h a n g e s D u r i n g H a r d b o a r d M a n u f a c t u r i n g . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 3 . F i r e - R e t a r d a n t T r e a t m e n t s . . . . . . . . . . . . . . . . . . . 8 A . G e n e r a l . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 B . P a r t i c l e b o a r d s . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 C . F i b e r b o a r d s 10 4 . C h e m i s t r y o f B r o m i n a t i o n . . . . . . . . . . . . . . . . . . . . 12 5 . L o s s e s i n D e c a y . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16 6 . M e c h a n i s m o f Hood D e t e r i o r a t i o n . . . . . . . . . . . . . 17 7 . D e c a y i n B u i l d i n g s i n R e l a t i o n t o w e t t i n g . . . 20 8. B o a r d D u r a b i l i t y a n d D e c a y . . . . . . . . . . . . . . . . . . 22 V C h a p t e r P a g e 9 . D e c a y i n C o m p o s i t i o n B o a r d M a t e r i a l s . . . . . . . . 25 A . , P a r t i c l e b o a r d s . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25 B. P i b e r b o a r d s . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27 10. P r o t e c t i o n A g a i n s t D e c a y . . . . . . . . . . . . . . . . . . . . 3 0 A . G e n e r a l 30 (a) . J J a t e r - s o l u f c l e i n o r g a n i c s a l t s . . . . . . . . 30 (b) . O r g a n i c - s o l v e n t s u b s t a n c e s . . . . . . . . . . . 31 B . T r e a t m e n t o f C o m p o s i t i o n M a t e r i a l s . . . . . . . . . 32 11 . L a b o r a t o r y T e s t M e t h o d s f o r D e c a y R e s i s t a n c e . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .34 A. G e n e r a l . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34 (a) . F u n g a l g r o w t h m e t h o d s . . . . . . . . . . . . . . . . ,34 (b) . H e i g h t - l o s s m e t h o d s . . . . . . . . . . . . . . . . . . 34 (c) . S t r e n g t h - l e s s m e t h o d s . . . . . . . . . . . . . . . . 36 (d) . B e s p i r o m e t r y m e t h o d s . . . . . . . . . . . . . . . . . 37 B . T e s t s o f C o m p o s i t i o n B o a r d s . . . . . . . . . . . . . . . . . 3 7 C . , F a c t o r s To Be C o n s i d e r e d . . . . . . . . . . . . . . . . . . . 40 (a) . L e a c h i n g . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40 (b) . I n i t i a l m o i s t u r e c o n t e n t . . . . . . . . . . . . . 41 (c) . S t e r i l i z a t i o n m e t h o d s . . . . . . . . . . . . . . . . 43 I I I . M A T E R I A L S AND METHODS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46 1. M a t e r i a l s 46 •••(••• A . A s p l u n d P u l p 46 E . P u l p B r o m i n a t i o n . . . . . . . . . . . . . . . . . . . . . . . . . . . 46 C . B o a r d s 47 2 . , M e t h o d s 48 A . C o m p o s i t i o n a n d S i z e o f t h e H a r d b o a r d T e s t B l o c k s . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49 B. W o o d - D e s t r o y i n g F u n g i U s e d . . . . . . . . . . . . . . . . . 50 C . P r e p a r a t i o n o f S o i l J a r s . . . . . . . . . . . . . . . . . . . 50 D. P r e p a r a t i o n o f T e s t S a m p l e s . . . . . . . . . . . . . . . . 51 (a) . L e a c h i n g . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51 (b) . S e t t i n g o f i n i t i a l m o i s t u r e c o n t e n t a n d m e t h o d o f s t e r i l i z a t i o n . . . . . . . . . . 52 E . E v a l u a t i o n o f R e s u l t s . . . . . . . . . . . . . . . . . . . . . . 53 v i C h a p t e r P a g e I V . R E S U L T S AND D I S C U S S I O N . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 54 1. C o m p o s i t i o n o f t h e H a r d b o a r d . . . . . . . . . . . . . . . . 55 2 . B r o m i n a t i o n . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 58 3 . L e a c h i n g . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 60 4 . M o i s t u r e C o n t e n t . . . . . . . . . . . . . . . . . . . . . . . . . . . . 63 5 . S t e r i l i z a t i o n M e t h o d . . . . . . . . . . . . . . . . . . . . . . . . 65 V . CONCLUSIONS 67 L I T E R A T U R E C I T E D 69 T A B L E S . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . , . . . 80 FIGURES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 86 v i i L I S T OF T A B L E S T a b l e P a g e 1. w e i g h t l o s s e s o f t e s t b l o c k s d u r i n g t h e p r e p a r a t i o n p e r i o d a n d u n d e r c o m p a r a t i v e c o n t r o l s i t u a t i o n i n s o i l j a r s d u r i n g i n c u b a t i o n . , W e i g h t l o s s e s i n p e r c e n t 80 2 . E f f e c t o f l e a c h i n g on t h e r e s i s t a n c e t o d e c a y o f n o n - b r o m i n a t e d a n d b r o m i n a t e d h a r d b o a r d . D e c a y w e i g h t l o s s e s i n p e r c e n t 81 3 . E f f e c t o f t h e i n i t i a l m o i s t u r e c o n t e n t o f l e a c h e d , n c n - b r o m i n a t e d and b r o m i n a t e d h a r d b o a r d on i t s r e s i s t a n c e to d e c a y . D e c a y w e i g h t l o s s e s i n p e r c e n t . . . . . . . . . . . . . . . 82 4 . E f f e c t o f m e t h o d o f s t e r i l i z a t i o n o f l e a c h e d , n o n - b r o m i n a t e d and b r o m i n a t e d h a r d b o a r d on i t s r e s i s t a n c e t o d e c a y . D e c a y w e i g h t l o s s e s i n p e r c e n t . . . . . . . . . . . . . . . 83 5 . S t a t i s t i c a l e v a l u a t i o n o f t h e d e c a y r e s u l t s f o r n o n - b r o m i n a t e d h a r d b o a r d . . . . . . . . . . . . . . . . . . . . . 84 6 . S t a t i s t i c a l e v a l u a t i o n o f t h e d e c a y r e s u l t s f o r b r o m i n a t e d h a r d b o a r d . . . . . . . . . . . . . . . . . . . . . . . . . 85 v i i i L I S T OF FIGURES F i g u r e Page 1. P r o d u c t i o n o f t h e r m o m e c h a n i c a l p u l p f o r h a r d b o a r d a c c o r d i n g t o t h e A s p l u n d m e t h o d . . . . . . . . . . . . . . 86 2 . S a m p l e p r e c o n d i t i o n i n g p r o c e d u r e f o r i n c u b a t i o n . . . . 87 3 . B a r d i a g r a m s h o w i n g d e c a y a f f e c t e d b y d i f f e r e n t f a c t o r s . . . . . . . . . . . . . . . . . . . . . . . . . . . . 89 4 . C o m p a r i s o n t o show t h e e f f e c t s o f b r o m i n a t i o n a n d l e a c h i n g o n d e c a y by P o r i a i n c r a s s a t a . . . . . . . . 90 5 . C o m p a r i s o n t o show e f f e c t o f b o a r d c o m p o s i t i o n o n d e c a y by P o r i a i n c r a s s a t a g r o w i n g o n n o n - b r o m i n a t e d a n d n o n - l e a c h e d b o a r d s . . . . . . . . 91 6. C o m p a r i s o n t o show e f f e c t o f b o a r d c o m p o s i t i o n o n d e c a y by P o r i a i n c r a s s a t a g r o w i n g o n b r o m i n a t e d a n d n o n - l e a c h e d b o a r d s . . . . . . . . . . . . 91 7. C o m p a r i s o n t o show e f f e c t s o f b o a r d c o m p o s i t i o n a n d l e a c h i n g o n d e c a y by P o r i a i n c r a s s a t a g r o w i n g on n o n - b r o m i n a t e d b o a r d s . . . . . . . . . . . . . 92 8. C o m p a r i s o n t o show e f f e c t s o f b o a r d c o m p o s i t i o n a n d l e a c h i n g o n d e c a y by P o r i a i n c r a s s a t a g r o w i n g on b r o m i n a t e d b o a r d s . . . . . . . . . . . . . . . . . 92 9 . C o m p a r i s o n t o show e f f e c t o f b r o m i n a t i o n o n d e c a y by P o l y p o r u s v e r s i c o l o r g r o w i n g o n n o n - l e a c h e d b o a r d s . . . . . . . . . . . . . . . . . . . . . . . . . . . 93 10. C o m p a r i s o n t o show e f f e c t o f b r o m i n a t i o n o n d e c a y by L e n z i t e s t r a b e a g r o w i n g on l e a c h e d b o a r d s . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 94 11 . C o m p a r i s o n t o show e f f e c t o f b r o m i n a t i o n o n d e c a y by P o l j j o o r u s a d u s t us g r o w i n g o n l e a c h e d b o a r d s . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 94 ix F i g u r e P a g e 12. C o m p a r i s o n t o show e f f e c t o f l e a c h i n g o n d e c a y by C o n i o p h o r a £ S £ e a n a g r o w i n g on b r o m i n a t e d b o a r d s . . . . . . . . . . . . . . . . . . . . . . . . . . . . 95 13. C o m p a r i s o n t o show e f f e c t o f s t e r i l i z a t i o n m e t h o d o n d e c a y by P o l y _ £ o r u s v e r s i c o l o r g r o w i n g o n l e a c h e d a n d n o n - b r o m i n a t e d b o a r d s . . . . . . . . . . . . 9 6 14. C o m p a r i s o n t o show e f f e c t o f i n i t i a l m o i s t u r e c o n t e n t o f b l o c k s c n d e c a y by P o r i a montji.cg3.a g r o w i n g on l e a c h e d a n d b r o m i n a t e d b o a r d s . . . . . 97 X ACKNOWLEDGEMENTS The a u t h e r a c k n o w l e d g e s w i t h g r a t i t u d e h i s a p p r e c i a t i o n t o D r . L . P a s z n e r , A s s o c i a t e P r o f e s s o r , F a c u l t y o f F o r e s t r y , f o r h i s v a l u a b l e a s s i s t a n c e i n s u g g e s t i n g t h e e x p e r i m e n t a l s u b j e c t a n d p r e p a r i n g t h e t h e s i s , a s w e l l a s f o r h i s c o n s c i e n t i o u s a n d u n d e r s t a n d i n g g u i d a n c e o v e r t h e p a s t t h r e e y e a r s a t t h i s U n i v e r s i t y ; t o D r . R. S . S m i t h , h e a d o f Wood P r o t e c t i o n s e c t i o n a t W e s t e r n F o r e s t P r o d u c t s L a b o r a t o r y , f o r h i s p r o f e s s i o n a l a s s i s t a n c e i n s u p e r v i s i n g t h e e x p e r i m e n t a l p h a s e s a n d p r o v i d i n g t h e n e c e s s a r y f a c i l i t i e s a t h i s L a b o r a t o r y ; t o M r . P . E . , J u r a z s , S e n i o r Wood T e c h n o l o g i s t , C a n a d i a n F o r e s t P r o d . L t d . , f o r t h e e x p e r i m e n t a l p u l p m a t e r i a l a n d p r o v i d i n g t e c h n i c a l g u i d a n c e and f a c i l i t i e s f o r b o a r d p r e p a r a t i o n ; t o M r . L , V a l g , A s s i s t a n t P r o f e s s o r , F a c u l t y o f F o r e s t r y , f o r h i s r e v i e w o f t h e m a n u s c r i p t ; t o D r . M . G . W a r r e n , R e s e a r c h S c i e n t i s t o f W F P I , f o r t h e s t a t i s t i c a l a n a l y s i s ; t o Ms . J . E . C l a r k , t e c h n i c i a n o f S F P L , f o r a s s i s t a n c e i n b i o l o g i c a l t e s t s ; t o M r . B . E . F o x , t e c h n i c i a n o f H F P L , f o r p r o d u c i n g t h e p h o t o p r i n t s f o r t h i s t e x t ; t o M r . G . Bohnenkamp S M r . E . H . B u r k e , b o t h t e c h n i c i a n s i n F a c u l t y o f F o r e s t r y , U . B . - C . , f o r t h e i r a s s i s t a n c e i n b o a r d m a k i n g a n d s a m p l e b l o c k s p r e p a r a t i o n ; t o M r . R . Y a n g , g r a d u a t e s t u d e n t i n F o r e s t r y , f o r h i s a s s i s t a n c e i n c o m p u t e r t e c h n i g u e w h i c h h e l p s c o n s t r u c t i n g t h e f o r m a t o f t h i s t e x t . A c k n o w l e d g e m e n t i s a l s o g i v e n t o t h e U n i v e r s i t y o f B r i t i s h C o l u m b i a f o r r e p e a t e d f i n a n c i a l s u p p o r t d u r i n g t h e a c a d e m i c p r o g r a m m e . 1 CHAPTER I . INTRODUCTION H a r d b o a r d s h a v e b e e n i n u s e f o r many y e a r s a n d h a v e f o u n d u s e s i n c o n s t r u c t i o n o f c o m m e r c i a l b u i l d i n g s and d o m e s t i c d w e l l i n g s . A l t h o u g h n o t p r i m a r i l y r e c o g n i z e d a s a c o m m o d i t y t o be u s e d o p e n l y e x p o s e d t o t h e e x t e r n a l e n v i r o n m e n t , u n d e r c e r t a i n c i r c u m s t a n c e s , e v e n when u s e d i n t e r n a l l y ( e . g . , i n b a t h r o o m s a n d k i t c h e n s ) , t h e r i s k o f b i o d e t e r i o r a t i o n may be g u i t e s i g n i f i c a n t . As a r e s u l t o f t h e r e c e n t f u e l c r i s i s , d o m e s t i c d w e l l i n g s a r e b e i n g more c l o s e l y s e a l e d t o p r e v e n t h e a t l o s s e s . S u c h e f f o r t s f r e g u e n t l y r e s u l t i n h i g h e r h u m i d i t i e s w i t h i n t h e d w e l l i n g s a n d , t h e r e f o r e , c r e a t e a g r e a t e r r i s k o f c o n d e n s a t i o n w i t h i n o r on t h e b u i l d i n g m a t e r i a l s , Wooden b u i l d i n g c o m p o n e n t s a r e f r e g u e n t l y p r o t e c t e d a g a i n s t b i o d e t e r i o r a t i o n by t r e a t m e n t w i t h c h e m i c a l wood p r e s e r v a t i v e s , o r p r e f e r a b l y , t h e wood may p o s s e s s a n i n h e r e n t n a t u r a l r e s i s t a n c e t o a t t a c k by m i c r o o r g a n i s m s c a p a b l e o f c a u s i n g b i o d e t e r i o r a t i o n . T h e b r o m i n a t i o n o f wood was d e v e l o p e d i n i t i a l l y a s a p o t e n t i a l f i r e r e t a r d a n t t r e a t m e n t o f l i g n i f i e d m a t e r i a l s ( 6 3 ) . But i n c i d e n t a l l y , b e c a u s e o f t h e m o l e c u l a r i n c l u s i o n o f t h e b r o m i n e , i t was s u g g e s t e d t h a t t h e p r o d u c t would be more r e s i s t a n t t o a t t a c k b y f u n g i w h i c h may c a u s e b i o d e t e r i o r a t i o n . , S u b s e g u e n t l y , u n p u b l i s h e d s t u d i e s i n I s r a e l (31) c l e a r l y showed t h a t b r o m i n a t e d s p r u c e wood and b r o m i n a t e d v e n e e r s o f Okume ( i a c o u m e a k l e i n e a n a P i e r r e ) , ' a n A f r i c a n h a r d w o o d , w e r e s i g n i f i c a n t l y p r o t e c t e d f r o m a t t a c k by s e v e r a l w o o d - d e s t r o y i n g 2 f u n g i u s e d i n l a b o r a t o r y t e s t s . H o w e v e r , more work i s n e e d e d t o c l a r i f y t h e e f f e c t i v e n e s s o f b r o m i n e a s a p r e s e r v a t i v e a g a i n s t w o o d - d e s t r o y i n g f u n g i . P a r t i c u l a r l y l i t t l e i s known a b o u t c o m p o s i t e m a t e r i a l s w h i c h g a i n i n c r e a s i n g a c c e p t a n c e a s b u i l d i n g m a t e r i a l s . The d u a l a d v a n t a g e s o f f i r e r e t a r d a n c e a n d r e s i s t a n c e a g a i n s t b i o d e t e r i o r a t i o n , i f p r o v e n t o be s u c c e s s f u l , w i l l i n c r e a s e t h e m a r g i n a l e c o n o m i c s o f t h e b r o m i n a t i o n t r e a t m e n t , w h e r e b y f i b e r b o a r d s c o u l d h a v e g r e a t l y i m p r o v e d u s e f u l n e s s and w i d e r a p p l i c a t i o n i n b u i l d i n g c o n s t r u c t i o n as c l a d d i n g m a t e r i a l . I n v e s t i g a t i o n i n t o t h e b i o d e t e r i o r a t i o n p r o b l e m o f h a r d b o a r d s i s i n t e r e s t i n g s i n c e t h e p r o c e s s o f h a r d b o a r d m a n u f a c t u r i n g , u n l i k e t h a t o f p a r t i c l e b o a r d p r o d u c t i o n , i n v o l v e s some d r a s t i c c h e m i c a l m o d i f i c a t i o n s o f t h e wood c o m p o n e n t s . R e a l i s t i c t e s t m e t h o d s a r e r e q u i r e d t o e v a l u a t e t h e p e r f o r m a n c e o f new b u i l d i n g m a t e r i a l s . , T e s t m e t h o d s u s e d f o r f i b e r b o a r d d e c a y s t u d i e s h a v e n o t b e e n s t a n d a r d i z e d h e r e t o f o r e . H o w e v e r , t h e s o i l - b l o c k m e t h o d r e c o m m e n d e d by ASTH f o r s o l i d wood may p r o v e b e t t e r t h a n o t h e r m e t h o d s w i t h r e s p e c t t o c o n t r o l o f m o i s t u r e c o n t e n t a s t h e p r o c e d u r e i s a p p l i c a b l e a t v a r i o u s m o i s t u r e c o n t e n t l e v e l s o f t h e s o i l . F o l l o w i n g c o m p a r i s o n t c o t h e r m e t h o d s S a v o r y (91) o b t a i n e d s a t i s f a c t o r y r e s u l t s i n t e s t i n g p l y w o o d b y t h e s o i l - b l o c k m e t h o d . F u r t h e r a c o m p a r i s o n o f l e a c h e d and u n l e a c h e d t e s t b l o c k s i n d i c a t e d t h a t t h e l e a c h i n g p r o c e d u r e h a d r e m o v e d a f a c t o r w h i c h was i n h i b i t o r y t o g r o w t h o f some t e s t f u n g i . The f a c t o r he i d e n t i f i e d was f r e e p h e n o l -f o r m a l d e h y d e (PF) r e s i n . PF was u s e d i n h i s t e s t m a t e r i a l s . I n g e n e r a l , i t seemed t h a t t h e s o i l — b l o c k method c o u l d be more 3 s u i t a b l e t h a n t h e a g a r - b l o c k m e t h o d f o r t e s t i n g p l y w o o d a n d o t h e r b o a r d m a t e r i a l s b o n d e d w i t h v a r i o u s t y p e s o f p h e n o l i c r e s i n s . Some p a n e l s u s e d i n t h i s s t u d y a l s o h a d p h e n o l i c r e s i n as b i n d e r a n d , t h e r e f o r e , s p e c i a l t r e a t m e n t was n e e d e d t o r e m o v e i t s e f f e c t on t h e t e s t r e s u l t s . L e a c h i n g o f t h e t e s t m a t e r i a l i n w a t e r p r i o r t o t h e d e c a y t e s t was i n c l u d e d a n d i n v e s t i g a t e d . T h e e f f e c t o f i n i t i a l m o i s t u r e c o n t e n t o f t e s t b l o c k s h a s b e e n a n o t h e r s u b j e c t c f c o n c e r n i n s e v e r a l s t u d i e s . T h e r e s u l t s o f t e s t s r e p o r t e d by H e d l e y a n d F o s t e r (42) a n d H i g h l e y a n d S c h e f f e r (45) , d e m o n s t r a t e d t h e p o s i t i v e e f f e c t o f s a m p l e * s m o i s t u r e c o n t e n t on t h e d e c a y t e s t r e s u l t s . A c c o r d i n g l y , two d i f f e r e n t l e v e l s o f m o i s t u r e c o n t e n t , r e p r e s e n t i n g h i g h a n d low m o i s t u r e s i t u a t i o n s , w e r e i n c l u d e d i n t h i s s t u d y t o t e s t t h e e f f e c t . Two s t e r i l i z a t i o n m e t h o d s , w e t - h e a t(121 C) and e t h y l e n e o x i d e t r e a t m e n t u n d e r v a c u u m , w e r e u s e d t o f i n d o u t t h e i r p o s s i b l e e f f e c t on d e c a y p e r f o r m a n c e o f h a r d b o a r d s . T h u s t h e p u r p o s e o f t h i s s t u d y was t o i n v e s t i g a t e t h e e f f e c t i v e n e s s o f a r e l a t i v e l y u n k n o w n c o m p o u n d , b r o m i n e l i n k e d t o l i g n i n s , a s a p r e s e r v a t i v e a g a i n s t w o o d — d e s t r o y i n g f u n g i . E f f e c t s o f l e a c h i n g t r e a t m e n t a n d i n i t i a l s a m p l e m o i s t u r e c o n t e n t , a s w e l l a s t h e d i f f e r e n t s t e r i l i z a t i o n m e t h o d s , on d e c a y were e v a l u a t e d f o r t h i s r a t h e r new s p e c i a l t y b u i l d i n g m a t e r i a l . T h i s a t t e m p t was a l s o t a k e n a s a s o r t i n g m e c h a n i s m t o f i n d a more r e l i a b l e d e c a y t e s t p r o c e d u r e f o r b o a r d m a t e r i a l s . T h e r e b y , i t was t r i e d t o s e e i f t h e o r i g i n a l s o i l - b l o c k m e t h o d c o u l d be m o d i f i e d t o p r o v i d e a b i o d e t e r i o r a t i o n t e s t f o r h a r d b o a r d s . 4 CHAPTER I I . L I T E R A T U R E SURVEY 1. D e f i n i t i o n o f H a r d b o a r d M a n u f a c t u r e d w o o d - b a s e d b u i l d i n g b o a r d s c a n be c l a s s i f i e d i n t o two m a j o r c a t e g o r i e s : (a) f i b e r b o a r d s , a n d (b) p a r t i c l e b o a r d s , l a r g e l y o n t h e b a s i s o f t y p e o f b o n d a n d s i z e o f t h e c o m p o n e n t wood p a r t i c l e s . T h e f o r m e r a r e made f r o m s e p a r a t e wood f i b e r s , b o n d e d t o g e t h e r w i t h t h e i n h e r e n t c o m p l e x o f l i g n i n a n d o t h e r c e l l w a l l c o m p o u n d s , P a r t i c l e b o a r d s , o n t h e o t h e r h a n d , a r e f o r m e d f r o m l a r g e r c h i p s o r s h a v i n g s o f w o o d , b o n d e d t o g e t h e r w i t h s y n t h e t i c a d h e s i v e s s u c h as u r e a - f o r m a l d e h y d e ( U F ) o r p h e n o l - f o r m a l d e h y d e ( P F ) , a n d p o l y i s o c y a n a t e r e s i n s . B o t h t y p e s o f b o a r d s a r e f u r t h e r s u b d i v i d e d on t h e b a s i s o f d e n s i t y , t h i c k n e s s , a n d a d d i t i v e s ; h a r d b o a r d b e i n g t h e most h i g h l y c o m p r e s s e d t y p e o f f i b e r b o a r d ( 6 6 ) , A c c o r d i n g t o t h e d e f i n i t i o n s s e t f o r t h i n t h e A m e r i c a n S o c i e t y f o r T e s t i n g a n d M a t e r i a l s ( 3 ) , S t a n d a r d D 1 5 5 4 - 6 7 , h a r d b o a r d i s a g e n e r i c t e r m f o r a p a n e l m a n u f a c t u r e d p r i m a r i l y f r o m i n t e r f e l t e d l i g n o c e l l u l o s i c f i b e r s ( u s u a l l y w o o d ) , c o n s o l i d a t e d u n d e r h e a t a n d p r e s s u r e i n a h o t p r e s s t o a s p . g r . o f 0 . 5 0 { d e n s i t y o f 31 l b s ' / f t 3 ) o r g r e a t e r , a n d t o w h i c h o t h e r m a t e r i a l s may h a v e b e e n a d d e d d u r i n g m a n u f a c t u r e t o i m p r o v e c e r t a i n b o a r d p r o p e r t i e s . A h a r d b o a r d o f a s p . g r . b e t w e e n 0 . 5 0 a n d 0 . 8 0 ( d e n s i t y b e t w e e n 31 a n d 50 l b s / f t 3 ) i s c a l l e d m e d i u m - d e n s i t y h a r d b o a r d w h i l e i t i s c a l l e d h i g h — d e n s i t y h a r d b o a r d i f t h e s p . g r , i s g r e a t e r t h a n 0 . 8 0 . 5 2 . C h e m i c a l C h a n g e s D u r i n g H a r d b o a r d M a n u f a c t u r i n g H o s t v i r g i n w o o d p u l p u s e d i n f i b e r b o a r d m a n u f a c t u r e t o d a y i s g e n e r a t e d by some means o f t h e r m o m e c h a n i c a l p u l p i n g p r o c e s s e s . A s p l u n d p r o c e s s , w h i c h i s u s e d t o g e n e r a t e t h e p u l p s f o r h a r d b o a r d u s e d i n t h i s s t u d y , was d e v e l o p e d i n t h e e a r l y 1 9 3 0 » s . I t u s e s m e c h a n i c a l f o r c e s f o r f i b e r i z i n g c h i p s t h a t h a d been s o f t e n e d w i t h t h e a i d o f s t e a m ( 8 8 ) . A f l o w s h e e t o f t h e A s p l u n d t h e r m o - m e c h a n i c a l p u l p i n g p r o c e s s f o r h a r d b o a r d i s shown i n F i g . 1. T h e r m o m e c h a n i c a l p u l p i n g h a s p r o g r e s s e d r a p i d l y s i n c e t h e a d v e n t o f t h e p r e s s u r i z e d r e f i n e r . D e t a i l e d d i s c u s s i o n s on t h e c h e m i c a l c h a n g e s o f wood d u r i n g t h e m e c h a n i c a l p u l p m a n u f a c t u r i n g p r o c e s s e s were g i v e n by P a s z n e r a n d W i l s o n ( 8 2 ) , a n d S p a l t ( 1 0 8 ) . S a t u r a t e d s t e a m a b o v e 130 C w i l l s o f t e n t h e l i g n i n - r i c h m i d d l e l a m e l l a a s i t p e n e t r a t e s t h e wood c h i p s . T h e p r e s s u r i z e d r e f i n e r a p p l i e s s h e a r t o wood c h i p s a t t h e same t i m e t h a t t h e m i d d l e l a m e l l a i s s o f t e n e d by s a t u r a t e d s t e a m . V e r y f i n e w h o l e f i b e r c a n be p r o d u c e d w i t h low m e c h a n i c a l e n e r g y c o n s u m p t i o n . A l s o , l o w c o o k i n g s t e a m p r e s s u r e s m i n i m i z e f o r m a t i o n o f s o l u b l e s a n d t h e p u l p y i e l d i s h i g h . From a n a t o m i c a l e x a m i n a t i o n s on r e f i n e r p u l p i t i s f o u n d t h a t t h e r m o m e c h a n i c a l p u l p i n g e x p l o i t s t h e t h e r m o p l a s t i c n a t u r e o f l i g n i n t o p r o d u c e l i g n i n - r i c h f i b e r s h i g h l y s u i t a b l e f o r b o a r d p r o d u c t i n . T h r o u g h a c h e m i c a l a n a l y s i s o f t h e l i g u o r p r o d u c e d d u r i n g h a r d b o a r d m a n u f a c t u r e i t c a n be u n d e r s t o o d w h i c h c h e m i c a l c h a n g e s i n wood a r e a f f e c t e d by f u r n i s h p r e p a r a t i o n p r o c e s s e s . T h e i n c r e a s e i n h o t - w a t e r s o l u b l e s d e v e l o p e d d u r i n g t h e 6 i n c r e a s i n g s t e a m p r e s s u r e s i s b e l i e v e d t o be c a u s e d b y c l e a v a g e o f a c e t y l g r o u p s f r o m t h e h e m i c e l l u l o s e s . T h i s p r o c e s s g i v e s r i s e t o a c i d - c a t a l y z e d h y d r o l y s i s o f o t h e r c e l l w a l l c o m p o n e n t s , e s p e c i a l l y t h e c a r b o h y d r a t e s . , The l i q u o r c a n be d i v i d e d i n t o c a r b o h y d r a t e and a n a r o m a t i c f r a c t i o n : t h e f o r m e r o f h o l o c e l l u l o s e o r i g i n a n d t h e l a t t e r o f l i g n i n o r i g i n . G a s - l i q u i d c h r o m a t o g r a p h y o f t h e h y d r o l y z a t e s o f l i g u o r e x t r a c t s , a f t e r h y d r o g e n a t i o n w i t h b o r o h y d r i d e a n d a c e t y l a t i o n w i t h a c e t i c a n h y d r i d e , c a n p r o d u c e c h r o m a t o g r a m s w i t h a t l e a s t f i v e d i s t i n c t p e a k s , r e p r e s e n t i n g a l d i t o l a c e t a t e s o f t h e f i v e s u g a r s c o m m o n l y f o u n d i n wood. T h e s e a r e t h e p e n t o s e s : L - a r a b i n o s e a n d D - x y l o s e a n d t h e h e x o s e s : D—mannose, D — g a l a c t o s e , a n d D — g l u c o s e . T h e o c c u r r e n c e o f r e l a t i v e p r o p o r t i o n s o f s u g a r s i n t h e h y d r o l y z a t e l i q u o r s w i t h s i m i l a r h e m i c e l l u l o s e c o m p o s i t i o n a s i n wood r e v e a l s t h a t t h e t h e r r a o m e c h a n i c a l p u l p i n g p r o c e s s l i b e r a t e s o n l y t h e h e m i c e l l u l o s e p o l y s a c c h a r i d e s a n d d o e s n o t a f f e c t t h e c e l l u l o s e f r a c t i o n t o any m e a s u r a b l e d e g r e e . T h e n o n - c a r b o h y d r a t e f r a c t i o n c a n i n d e e d be t r a c e d t o l i g n i n s o u r c e . G a s - l i q u i d c h r o m a t o g r a p h y o f e t h e r e x t r a c t s o f t h e wash l i q u o r s i n d i c a t e d t h e p r e s e n c e o f g u a i a c o l - a n d s y r i n g y l - a l d e h y d e , v a n i l l i n , v a n i l l i c a c i d , s y r i n g i c a c i d , and h y d r o x y b e n z o i c a c i d . T h e e v i d e n c e i n d i c a t e s t h a t t r e a t i n g wood c h i p s w i t h s a t u r a t e d s t e a m a b o v e 130 C c a u s e s t h e l i g n i n - r i c h m i d d l e l a m e l l a t o f a i l when s u b j e c t e d t o s h e a r i n g a c t i o n o f r e f i n e r p l a t e s . P a r a l l e l w i t h t h e t h e r m o p l a s t i c s e p a r a t i o n o f f i b e r s 7 h y d r o l y t i c d e g r a d a t i o n o f h e m i c e l l u l o s e s a n d l i g n i n a l s o o c c u r , a n d w a t e r — s o l u b l e o l i g o s a c c h a r i d e s , a r o m a t i c and a l i p h a t i c l i g n i n f r a g m e n t s a r e g e n e r a t e d . C o n v e r s i o n o f p u l p f u r n i s h t o b o a r d b e g i n s w i t h t h e f e l t i n g o p e r a t i o n . F i b e r s s u s p e n d e d i n w a t e r a r e d e p o s i t e d on a w i r e a n d c o n c e n t r a t e d i n t o a n i n t e r f e l t e d mat by r e m o v i n g t h e s u s p e n d i n g w a t e r . C o l d - p r e s s o p e r a t i o n r e d u c e s i n t e r f i b e r v o i d s p a c e a n d e x p e l s most o f t h e w a t e r . H a r d b o a r d p r o c e s s e s r e q u i r e f u r t h e r h o t p r e s s i n g t o d e n s i f y and c o n s o l i d a t e t h e mat t o t h e d e s i g n a t e d s p e c i f i c g r a v i t y . L i t t l e c h e m i c a l c h a n g e i s e f f e c t e d a t t h e t e m p e r a t u r e s u s e d ( b e l o w 100 C) i n c o l d p r e s s i n g . M a j o r c h a n g e s i n b o a r d p r o p e r t i e s and some c h a n g e s i n c h e m i c a l c o m p o s i t i o n o c c u r d u r i n g h o t p r e s s i n g a s h i g h e r d e n s i t i e s a r e d e v e l o p e d b y h e a t and p r e s s u r e . L i g n o c e l l u l o s i c f i b e r s , when i n t e r f e l t e d a n d d e n s i f i e d u n d e r h e a t a n d p r e s s u r e , d e v e l o p i m p r e s s i v e w e t - s t r e n g t h . T h e m e c h a n i s m o f w e t — s t r e n g t h d e v e l o p m e n t was d e s c r i b e d by s e v e r a l s c h o o l s o f t h e o r y , i n c l u d i n g p o l y c o n d e n s a t i o n o f c e l l w a l l s u b s t a n c e s t o f o r m a w a t e r — i n s o l u b l e b o n d i n g s u b s t a n c e , o r v i e w i n g l i g n i n a s a t h e r m o p l a s t i c a d h e s i v e . H o w e v e r , t h e s t u d i e s c o n d u c t e d b y S p a l t (108) a t H a s o n i t e C o r p o r a t i o n c o n f i r m e d t h a t t h e s o u r c e o f w e t - s t r e n g t h i n h a r d b o a r d s i s t h e r m o p l a s t i c — f u s i o n o f l i g n i n c o n c e n t r a t e d o n t h e s u r f a c e s o f t h e f i b e r s . The same r e p o r t a l s o c o n c l u d e d t h a t b o a r d c o n v e r s i o n a n d c o n s o l i d a t i o n by h e a t t r e a t m e n t i s a t t e n d e d by p y r o l y t i c r e a c t i o n s w h i c h f u r t h e r b r e a k d o w n a n d g a s s i f y l o w — m o l e c u l a r — w e i g h t p r o d u c t s g e n e r a t e d d u r i n g d e f i b r a t i o n h y d r o l y s i s . 8 3 . F i r e - R e t a r d a n t T r e a t m e n t s A . G e n e r a l W i t h t h e i n c r e a s e d c o n c e r n o v e r f i r e s a f e t y e f f o r t s t o d e v e l o p b e t t e r f i r e r e t a r d a n t s f o r wood a n d wood p r o d u c t s h a v e b e e n i n t e n s i f i e d t o meet t h e r e s t r i c t i o n s i m p o s e d b y b u i l d i n g c o d e s , J u n e j a (56) r e v i e w e d e x t e n s i v e l y t h e p r o c e s e s s o f i g n i t i o n a n d c o m b u s t i o n , a n d t h e s y n e r g i s m i n f i r e r e t a r d a n c y t o e x p l a i n t h e m u l t i d i s c i p l i n a r y n a t u r e o f c o m b u s t i o n r e s e a r c h . The p r i n c i p a l a d v a n t a g e o f f i r e — r e t a r d a n t t r e a t m e n t o f wood i s t h a t t h e s u r f a c e — f l a m m a b i l i t y c h a r a c t e r i s t i c s a r e d e c r e a s e d . A s e c o n d a d v a n t a g e i s t h a t t h e t r e a t e d wood c o n t r i b u t e s l e s s h e a t , e s p e c i a l l y t h e v o l a t i l e p r o d u c t s , d u r i n g t h e i n i t i a l p a r t o f f i r e s . T h e f i r e - r e t a r d a n t t r e a t m e n t o f wood i n v o l v e s i m p r e g n a t i n g w a t e r s o l u t i o n s o f t h e c h e m i c a l s i n t o t h e wood u n d e r p r e s s u r e . , B r u s h , d i p , o r i m m e r s i o n t r e a t m e n t s do n o t u s u a l l y g i v e t h e n e c e s s a r y r e t e n t i o n s . G e n e r a l p r a c t i c e s i n t h e f i r e — r e t a r d a n t t r e a t m e n t o f wood p r o d u c t s a r e d e s c r i b e d i n v a r i o u s s t a n d a r d s o f AWPA. H o l m e s (47) made a d e t a i l e d r e v i e w o f t h e e f f e c t o f f i r e -r e t a r d a n t t r e a t m e n t s on p e r f o r m a n c e p r o p e r t i e s o f w o o d . , F i r e - r e t a r d a n t c h e m i c a l s u s e d b y t h e c o m m e r c i a l w o o d - t r e a t i n g i n d u s t r y h a v e b e e n known f o r a h a l f c e n t u r y a n d a r e l i m i t e d a l m o s t e x c l u s i v e l y t o mono— a n d di—ammonium p h o s p h a t e , ammonium s u l f a t e , z i n c c h l o r i d e , b o r a x , and b o r i c a c i d ( 3 4 ) . T h e f o r m u l a t i o n s f o r some o t h e r c u r r e n t c o m m e r c i a l t r e a t m e n t s a r e b e l i e v e d t o be b a s e d p r i n c i p a l l y on t h e same s a l t s . T h e s e f o r m u l a t i o n s a r e u s u a l l y d i s s o l v e d i n w a t e r a t 12 9 t o 15 p e r c e n t c o n c e n t r a t i o n t o be u s e d i n t h e p r e s s u r e i m p r e g n a t i o n o f w o o d . , B e s i d e s w a t e r — s o l u b l e s a l t s , f i r e — r e t a r d a n t a d d i t i v e s c a n be u s e d i n c o m b i n a t i o n w i t h o i l - b o r n e p r e s e r v a t i v e s t o i n c r e a s e t h e f i r e — r e t a r d a n c y o f t r e a t e d members ( 3 5 ) . H o w e v e r , p r o d u c t s t r e a t e d w i t h i n o r g a n i c s a l t s a r e s u b j e c t t o l e a c h i n g a n d s u r f a c e b l o o m i n g , a n d a r e u n s u i t a b l e f o r e i t h e r i n t e r i o r d e c o r a t i v e o r e x t e r i o r u s e . F o r l e a c h - r e s i s t a n t t y p e t r e a t m e n t s , t h e l i t e r a t u r e s h o w s t h a t some o r a l l o f t h e f o l l o w i n g a r e u s e d : u r e a , m e l a m i n e , d i c y a n d i a m i d e , p h o s p h o r i c a c i d , a n d f o r m a l d e h y d e ( 5 3 , 5 5 , 5 8 ) . D e c a y r e s i s t a n c e i s a l s o shown f o r a u r e a — b a s e d t r e a t m e n t s ( 5 4 ) . B. P a r t i c l e b o a r d s I n - p r o c e s s f l a m e - r e t a r d a n t t r e a t m e n t i s w e l l a d a p t e d t o p a r t i c l e b o a r d w h e r e a d r y f o r m a t i o n p r o c e s s i s e m p l o y e d . A b i t i b i P a p e r Company m a n u f a c t u r e s a f l a m e - r e t a r d a n t f l a k e b o a r d made by a p p l y i n g an a q u e o u s b o r a t e s o l u t i o n t o t h e g r e e n f l a k e s p r i o r t o t h e d r y i n g o p e r a t i o n . D r y c h e m i c a l s c a n a l s o be a d d e d t o t h e p a r t i c l e s , o r m i x e d w i t h t h e b i n d e r r e s i n , b u t a d d i n g t h e f l a m e - r e t a r d a n t c h e m i c a l s i n s o l u t i o n f o r m i s n o r m a l l y t h e most e f f e c t i v e p r o c e d u r e ( 5 9 ) . S y s k a (111) r e p o r t e d on f i r e - r e t a r d a n t t r e a t m e n t s f o r p a r t i c l e b o a r d a n d f o u n d t h a t a c h e m i c a l t r e a t m e n t l e v e l o f 10 t o 15 p e r c e n t o f b o a r d w e i g h t was r e g u i r e d f o r a d e q u a t e f i r e p e r f o r m a n c e . T h e most c r i t i c a l p r o b l e m p o i n t e d o u t was t h e a d v e r s e e f f e c t o f t h e t r e a t m e n t c h e m i c a l s o n t h e r e s i n b i n d e r s . 10 S u c h e f f e c t s l e a d t o l o w e r b o a r d s t r e n g t h . He c o n c l u d e d t h a t t h e r e s i n s were b e i n g c a t a l y z e d by t h e f i r e - r e t a r d a n t c h e m i c a l s a n d s e t b e f o r e t h e p r e s s was c l o s e d . B a l o n e y (68) d i s c u s s e d r e c e n t l y t h e i n d u s t r i a l a p p l i c a t i o n s o f f i r e - r e t a r d a n t t r e a t m e n t s t o p a r t i c l e b o a r d s . C . F i b e r b o a r d s Hood f i b e r - b a s e s t r u c t u r a l p r o d u c t s h a v e b e e n l i m i t e d i n some a p p l i c a t i o n s a s b u i l d i n g m a t e r i a l s b e c a u s e o f t h e i r f l a m m a b i l i t y . F i r e p r o t e c t i o n a n d c o d e o f f i c i a l s a r e i n c r e a s i n g t h e l i m i t a t i o n s o n m a t e r i a l s w i t h c o m b u s t i b l e f i n i s h e s . T h i s c a n s e r i o u s l y a f f e c t t h e m a r k e t f o r h a r d b o a r d p r o d u c t s , s i n c e a l a r g e v o l u m e i s u s e d a s d e c o r a t i v e m a t e r i a l i n h o u s e s a n d o f f i c e b u i l d i n g s . T h e s e h a r d b o a r d p r o d u c t s c a n a l s o be u s e d o n TV c a b i n e t s , m o t o r v e h i c l e s , a n d m o b i l e homes where r e d u c e d f l a m m a b i l i t y i s r e c e i v i n g i n c r e a s e d a t t e n t i o n . M y e r s a n d H o l m e s (78) c o n d u c t e d r e s e a r c h t o d e t e r m i n e i f t h e f i b e r s f o r d r y - f o r m e d h a r d b o a r d c o u l d be t r e a t e d w i t h s e l e c t e d f i r e r e t a r d a n t s t o p r o d u c e b o a r d s w i t h s a t i s f a c t o r y s t r e n g t h a n d f i r e p e r f o r m a n c e . T h e p r o c e s s i n v o l v e d d e t e r m i n i n g c o m p a t i b i l i t y b e t w e e n s e l e c t e d f i r e - r e t a r d a n t c h e m i c a l s a n d r e s i n b i n d e r s . T w e n t y - o n e f i r e - r e t a r d a n t s y s t e m s were s e l e c t e d on t h e b a s i s o f p a s t e x p e r i e n c e i n p r o v i d i n g some f i r e r e t a r d a n c y f o r s o l i d wood p r o d u c t s . T h r e e t y p e s o f f i r e r e t a r d a n t s were u s e d : w a t e r - s o l u b l e s a l t s , l i q u i d ammonium p o l y p h o s p h a t e s , a n d c u r i n g — t y p e o r g a n i c p h o s p h a t e s . R e s u l t s i n d i c a t e d t h a t a m o d e r a t e r e d u c t i o n i n f l a m e s p r e a d ( t o 60%) c a n 11 be o b t a i n e d a t t h e 10 p e r c e n t f i r e r e t a r d e n t l e v e l o f t r e a t stent w i t h seme r e d u c t i o n i n m o d u l u s o f r u p t u r e . , I n c r e a s i n g t h e l e v e l t o 20 p e r c e n t g a v e f u r t h e r r e d u c t i o n s i n f l a m e s p r e a d w i t h l i t t l e a d d i t i o n a l r e d u c t i o n i n b e n d i n g s t r e n g t h , p a r t i c u l a r l y w i t h a t r e a t m e n t o f d i s o d i u m o c t a b o r a t e t e t r a h y d r a t e - b o r i c a c i d , a w a t e r - s o l u b l e s a l t . T h e r e s i n s y s t e m f o r use w i t h t h e s e a c i d i c s o l u t i o n s must b e c a r e f u l l y c h o s e n t o a v o i d c o m p a t i b i l i t y p r o b l e m s . P o t e n t i a l c o r r o s i o n p r o b l e m s d u r i n g h a r d b o a r d p r o d u c t i o n a n d d u r i n g u s e must be e v a l u a t e d . Wet—pr ocess h a r d b o a r d , however> i s much more d i f f i c u l t t o r e n d e r f l a m e - r e t a r d a n t . I n t h e e a r l y 1 9 6 0 s , e x p l o r a t o r y a t t e m p t s were made t o i n c o r p o r a t e w a t e r — s o l u b l e s a l t s i n t o wet—formed h a r d b o a r d . T h e s e e f f o r t s were u n s u c c e s s f u l b e c a u s e o f l o w r e t e n t i o n o f c h e m i c a l s ( 7 8 ) . Common f l a m e - r e t a r d a n t c h e m i c a l s c a n be a d d e d t o t h e p u l p s l u r r y o r t o t h e p a r t i a l l y d e w a t e r e d wet mat . H o w e v e r , r e t e n t i o n o f s a l t s i s d i f f i c u l t w i t h w e t - p r e s s e d b o a r d due t o t h e l a r g e v o l u m e o f w a t e r , i n c l u d i n g c h e m i c a l s , e x p e l l e d d u r i n g t h e h o t p r e s s i n g , t h u s m a k i n g t h e p r o c e s s u n e c o n o m i c a l and i m p r a c t i c a l . O t h e r p r o b l e m s i n v o l v e t h e l o s s o f f i r e - r e t a r d a n t c h e m i c a l s w i t h t h e d r a i n a g e w a t e r a n d s u b s e q u e n t w a t e r p o l l u t i o n ( 5 7 ) , C h e m i c a l l i n k i n g o f f i r e - r e t a r d a n t c h e m i c a l s t o t h e i n d i v i d u a l f i b e r s w o u l d seem a l o g i c a l way t o o v e r c o m e t h e r e t e n t i o n p r o b l e m w i t h w e t - p r o c e s s h a r d b o a r d . B r o m i n a t i o n t r e a t m e n t o f wood p u l p , d e v e l o p e d by L e w i n (63) i n I s r a e l seems t o b e a good s o l u t i o n . I n t h i s p r o c e s s b r o m i n e i s c h e m i c a l l y l i n k e d t o t h e l i g n i n p o r t i o n o f t h e f i b e r s ( 1 1 2 ) , a r e a c t i o n c o m p a r a b l e i n many r e s p e c t s t o c h l o r i n a t i o n o f p u l p s a s a p p l i e d 12 d u r i n g t h e b l e a c h i n g p r o c e s s . T h e h a r d b o a r d made f r o m b r o m i n a t e d p u l p s h a d a l o w e r f l a m e - s p r e a d i n d e x t h a n t h a t made f r o m u n t r e a t e d p u l p s . T h e i n f l a m m a b i l i t y t e s t s on b r o m i n a t e d f i b e r p r o d u c t s , r u n by d i f f e r e n t m e t h o d s , p r o d u c e d h i g h r a t i n g s o f n o n - i n f l a m m a b i l i t y p r o v i d e d more t h a n 3 p e r c e n t o f b r o m i n e was p r e s e n t i n t h e p r o d u c t ( 6 4 ) . L a r s e n a n d Yan (59) had some e x p e r i e n c e w i t h t h e b r o m i n a t i o n p r o c e s s a n d p o i n t e d o u t seme o f i t s d r a w b a c k s . T h e work b y J u r a z s and P a s z h e r (57) i s t h e most r e c e n t l y p u b l i s h e d one d e a l i n g w i t h p r o b l e m s e x p e r i e n c e d w i t h b r o m i n a t e d h a r d b o a r d s . The p r o j e c t s had b e e n i n i t i a t e d a t C a n a d i a n F o r e s t P r o d u c t s L i m i t e d g u i t e some t i m e a g o . , 4 . C h e m i s t r y o f B r o m i n a t i o n T h e b r o m i n a t i o n p r o c e s s , a s i t was d e v e l o p e d i n I s r a e l , c o n s i s t e d o f t r e a t i n g a q u e o u s h i g h l i g n i n — c o n t e n t p u l p s u s p e n s i o n , s u c h as t h a t f r o m t h e A s p l u n d p r o c e s s . The b r c m i n a t i n g a g e n t s were a d d e d a t 2 . 0 p e r c e n t c o n s i s t e n c y . T r e a t m e n t i s e f f e c t e d a t 40 t o 50 C w i t h e n o u g h s o d i u m b r o m i d e ( N a B r ) t o p r o v i d e 10 p e r c e n t ( b y w e i g h t ) o f b r o m i n e , b a s e d on t h e o v e n - d r y w e i g h t o f t h e p u l p . The s o d i u m b r o m i d e i s a p p l i e d t o t h e p u l p s u s p e n s i o n w i t h o u t a b u f f e r a t a s o l u t i o n pH o f a b o u t 5 . 0 . B r o m i n e i s l i b e r a t e d f r o m i t s s a l t s o l u t i o n by b u b b l i n g a g u a n t i t y (15$ b a s e d o n OD w e i g h t o f t h e p u l p ) o f c h l o r i n e g a s t h r o u g h t h e s u s p e n s i o n t o i n i t i a t e r a p i d p u l p 13 bromination under the p r e v a i l i n g c o n d i t i o n s . ; T h e average bromine content f o l l o w i n g n e u t r a l i z a t i o n with c a l c i u m hydroxide (Ca (0H)2 ) t o pH 5.5 i s 5 t o 8 percent. During the course of bromination the s l u r r y pH drops to about 1,H due to the f o r m a t i o n of hydrobromic and h y d r o c h l o r i c a c i d s , hence the n e c e s s i t y of n e u t r a l i z a t i o n with Ca(OH>2. The chemical r e a c t i o n o f bromine with wood under these c o n d i t i o n s i s s i m i l a r i n many r e s p e c t s to c h l o r i n a t i o n of woodpulps and has been i n v e s t i g a t e d i n d e t a i l by Zabicky (122, 123). The bromine i s almost g u a n t i t a t i v e l y consumed, s i n c e of every three bromine atoms o r i g i n a l l y present as f r e e bromine i n s o l u t i o n , two are converted i n t o hydrobromic a c i d and one becomes attached to the woodpulp. Most of the bromine t h a t becomes a s s o c i a t e d with the wood should be attached by chemical bonds, formed through an e l e c t r o p h i l i c aromatic s u b s t i t u t i o n of a hydrogen atom on the aromatic l i g n i n b u i l d i n g u n i t s . The bromine gener a t i o n by c h l o r i n e gas i s r e p r e s e n t e d by: H20 Br + c i 2 ~£o"c" B r C 1 * c l £ 1 3 The r e s u l t i n g B r C l r e a c t s with l i g n i n (represented by Lig:H) i n two ways: A. Bromination BrCl + Lig:H • • I i g : B r *• HCl [ 2 ] 14 B . O x i d a t i o n B r C l + L i g : H + H 2 0 L i g : O H • HBr • H C l £ 3 ] T h e b r o a i d e f o r m e d i n t h e o x i d a t i o n r e a c t i o n f 3 J c a n be r e g e n e r a t e d i n r e a c t i o n [ 1 ] . T h e r e a r e t h r e e p o s s i b l e p o s i t i o n s o f b r o m i n e s u b s t i t u t i o n on t h e l i g n i n b u i l d i n g u n i t s , d e p e n d i n g on t h e a c c e s s i b i l i t y o f t h e s e r e a c t i v e s i t e s , . T h e e x a c t p o s i t i o n o f t h e b r o m i n e on t h e a r o m a t i c r i n g s i n l i g n i n i s d i f f i c u l t t o a s c e r t a i n , b u t p r e v i o u s e x p e r i m e n t s b y Z a b i c k y (122) s h o w e d t h a t 0 . 4 8 t o 0 . 5 4 m o l e o f b r o m i n e p e r l i g n i n m e t h o x y l c o r r e s p o n d s t o a p p r o x i m a t e l y o n e b r o m i n e a t c m p e r a r o m a t i c r i n g o f t h e wood l i g n i n . O t h e r s i t e s o f a t t a c k were c o n s i d e r e d u n i m p o r t a n t . T h u s t h e b r o m i n e c o n s u m p t i o n f r o m t h e i n i t i a l s l u r r y i s a l m o s t e x c l u s i v e l y d u e t o two r e a c t i o n s i n w h i c h o n e b r o m i n e atom p a r t i c i p a t e s i n t h e f o r m a t i o n o f b r o m h y d r i n s o f l i g n i n , a s d e s c r i b e d a b o v e i n a r o m a t i c s u b s t i t u t i o n . T h e o t h e r e n g a g e s i n o x i d a t i o n r e a c t i o n s . A p p r o x i m a t e l y o n e - t h i r d o f t h e a v a i l a b l e b r o m i n e a t o m s p a r t i c i p a t e s i n t h e l i g n i n o x i d a t i o n r e a c t i o n w h i c h l e a d s t o d e m e t h y l a t i c n o r s i d e - c h a i n a n d h y p o b r o m i t e e s t e r f o r m a t i o n . T h e r e a c t i o n s a r e e x t r e m e l y r a p i d and c a n be c a r r i e d o u t i n 60 s e c o n d s . C h l o r i n e a l s o r e a c t s w i t h l i g n i n i n t h e f o l l o w i n g w a y s : * L i g : H L i g : C l + H C l 1*1 * L i g : H • H 2 0 L i g : 0 H • 2HC1 C5] 15 A b o u t 50% o f t h e c o n s u m e d c h l o r i n e r e a c t s a c c o r d i n g t o r e a c t i o n s [ 1 ] a n d [ 2 1 a n d a f f e c t b r o m i n a t i o n ; a b o u t 8 p e r c e n t i s u s e d i n c h l o r i n a t i o n ( r e a c t i o n [ 4 ] ) a n d a b o u t 42 p e r c e n t i s c o n s u m e d i n o x i d a t i o n r e a c t i o n [ 3 ] a n d [ 5 ] , a c c o r d i n g t o a r e p o r t by I n s t i t u t e f o r F i b e r s and F o r e s t P r o d u c t s B e s e a r c h i n I s r a e l ( 5 ) . T h e b r o m i n a t i o n a n d o x i d a t i o n o f t h e p u l p s t o c k y i e l d h y d r o c h l o r i c a c i d a n d c o n s e q u e n t l y t h e pH o f t h e s l u r r y d r o p s t o pH 1 . 4 t o 2 . 0 . T o a v o i d d e t r i m e n t a l e f f e c t s o f t h e l o w p H , t h e h y d r o c h l o r i c a c i d i s n e u t r a l i z e d w i t h c a l c i u m h y d r o x i d e ; 2HC1 C a ( 0 H ) 2 C a C l 2 • 2H.20 . 16J I t s h o u l d b e p o i n t e d o u t t h a t u n d e r t h e p r e v a i l i n g r e a c t i o n c o n d i t i o n s t h e wood p o l y s a c c h a r i d e s a r e n o t e x p e c t e d t o r e a c t w i t h b r o m i n e by e i t h e r o f t h e two r e a c t i o n m e c h a n i s m s shown to be o p e r a t i v e w i t h t h e l i g n i n f r a c t i o n , i . e . , s u b s t i t u t i o n a n d o x i d a t i o n , a n d t h e r e f o r e , no c e l l u l o s e d e g r a d a t i o n w o u l d be e x p e c t e d . The f i r e - r e t a r d a n t a c t i o n o f b r o m i n e - c o n t a i n i n g wood i s r e a l i z e d t h r o u g h t h e f l a m e - i n h i b i t o r y a c t i o n o f b r o m i n e . B r o m i n e r e a d i l y f o r m s r e l a t i v e l y s t a b l e f r e e r a d i c a l s w h i c h c a n e f f e c t i v e l y i n h i b i t t h e p r o g r e s s o f b r a n c h i n g c h a i n r e a c t i o n s t h o u g h t t o b e i n v o l v e d i n p y r o l y t i c a n d c o m b u s t i o n p r o c e s s e s l e a d i n g t o b u r n i n g o f wood ( 1 6 ) . 16 5 . L o s s e s i n D e c a y D e t e r i o r a t i o n o f wood a n d w o o d - b a s e d m a t e r i a l c a n be b r o u g h t a b o u t by a c t i o n o f f o r e i g n b i o l o g i c a l a g e n c i e s , s u c h a s f u n g i , b a c t e r i a , i n s e c t s , a n d m a r i n e b o r e r s . F u n g i a r e t h e most i m p o r t a n t o r g a n i s m s r e s p o n s i b l e f o r wood d e t e r i o r a t i o n a n d t h e a t t a c k by t r u e w o o d - d e s t r o y i n g f u n g i c a n be v e r y r a p i d u n d e r o p t i m u m c o n d i t i o n s , a n d r e s u l t i n d r a m a t i c wood w e i g h t a n d s t r e n g t h l o s s e s . H o o d - b a s e d m a t e r i a l s , i . e . , p l y w o o d , p a r t i c l e b o a r d s , a s w e l l a s h a r d b o a r d s , g a i n i n c r e a s i n g i m p o r t a n c e a s b u i l d i n g m a t e r i a l s , i n c l u d i n g p r e f a b r i c a t e d p a r t s a s a r e s u l t o f p r e s s u r e f r o m s h o r t a g e s o f raw m a t e r i a l and a d v a n c e m e n t o f t e c h n o l o g y i n wood i n d u s t r i e s . T h e p r o t e c t i o n a g a n i s t f u n g i , w h i c h i s i n d i s p e n s a b l e u n d e r c i r c u m s t a n c e s where a t t a c k c a n be e x p e c t e d , r e g u i r e s more a t t e n t i o n a n d f u r t h e r s t u d i e s . T h e t o t a l c o s t b e c a u s e o f o u r i n a b i l i t y o r u n w i l l i n g n e s s t o p r o t e c t wood m a t e r i a l s i n s e r v i c e f r o m b i o d e t e r i o r a t i o n c a n be v e r y l a r g e . B a s e d o n c o n s t r u c t i o n s t a t i s t i c s o f C a n a d a , S m i t h (105) e s t i m a t e d a more t h a n $90 m i l l i o n a n n u a l l o s s d u e t o t h e d e c a y o f wood i n d o m e s t i c d w e l l i n g s e r v i c e . A c o m p a r a b l e f i g u r e f o r t h e U . S . A w o u l d amount t o a b o u t $500 m i l l i o n . S t r a n k s (110) r e p o r t e d , u s i n g t h e s t a t i s t i c s c o m p i l e d b y t h e A m e r i c a n Hood P r e s e r v e r s A s s o c i a t i o n f o r 1 9 7 1 , t h a t a b o u t 2 6 , 8 9 6 m i l l i o n c u b i c f e e t o f t i m b e r p e r y e a r was p r e s e r v e d i n some 390 t r e a t i n g p l a n t s i n U . S . A . T o t a l p r e s e r v a t i v e u s a g e i s s a i d t o i n c r e a s e 3% a y e a r . A l t h o u g h b a c t e r i a a n d m o u l d s w i l l o f t e n a f f e c t t h e e n d - u s e 17 o f wood p r o d u c t s and w o o d - d e s t r o y i n g i n s e c t s l i k e C o l e o p t e r a g r o u p ( b e e t l e s ) a n d I s o p t e r a g r o u p ( t e r m i t e s ) a r e i m p o r t a n t i n some t r o p i c a l a r e a s p a r t i c u l a r l y , no a t t e m p t was made t o i n v e s t i g a t e t h e i r e f f e c t cn h a r d b o a r d s i n t h i s s t u d y . 6. M e c h a n i s m o f Wood D e t e r i o r a t i o n F u n g i w h i c h d e c a y wood p o s s e s s some u n i q u e c h a r a c t e r i s t i c s e n a b l i n g them t o u s e wood a s a s o u r c e o f r e q u i r e d n u t r i e n t s . I l l f u n g i a r e h e t e r o t r o p h i c o r g a n i s m s . T h i s means t h a t t h e y must o b t a i n o r g a n i c f o c d s u b s t a n c e s f r o m t h e i r e n v i r o n m e n t i n o r d e r t o s y n t h e s i z e most o f t h e i r own o r g a n i c c o n s t i t u e n t s a n d t o s a t i s f y t h e i r e n e r g y r e g u i r e m e n t s . Two m a j o r n u t r i e n t s o u r c e s a r e a s f o l l o w s : (a) . C a r b o n s o u r c e . A l m o s t a l l f u n g i h a v e t h e c a p a c i t y t o u s e g l u c o s e a s a c a r b o n s o u r c e . O t h e r s u p p l i e r s o f c a r b o n u t i l i z a b l e by many f u n g i i n c l u d e s u c r o s e , m a l t o s e , s t a r c h , a n d c e l l u l o s e w h i c h i s t h e m a i n c o m p o n e n t o f w o o d . (b) . N i t r o g e n s o u r c e . F u n g a l n i t r o g e n s o u r c e s a r e q u i t e v a r i e d a n d may b e o r g a n i c o r i n o r g a n i c i n n a t u r e . A l l f u n g i c a n u s e one o r more o r g a n i c s u p p l i e r s o f n i t r o g e n , f o r e x a m p l e , p e p t o n e s , a m i n o a c i d s , o r a m i d e s . I n some i n s t a n c e s , c a r b o n my a l s o be s u p p l i e d by t h e s e c o m p o u n d s . . N u m e r o u s f u n g i a r e c a p a b l e o f u t i l i z i n g i n o r g a n i c s a l t s c o n t a i n i n g n i t r o g e n . T h e s e s a l t s may c o n t a i n n i t r a t e (NO3) , n i t r i t e (NO2 ) o r ammonium (NH^) . A few f u n g i may b e a b l e t o o b t a i n n i t r o g e n v i a t h e d i r e c t u t i l i z a t i o n 18 o f m o l e c u l a r n i t r o g e n ( 1 0 7 ) . H o o d - d e s t r o y i n g f u n g i a r e c a p a b l e o f s y n t h e s i z i n g e n z y m e s t h a t e n a b l e them t o u t i l i z e p o l y m e r i c o r g a n i c wood m a t e r i a l s . T h e s e e n z y m e s h a v e t h e c a p a c i t y t c d e p o l y m e r i z e o r c l e a v e t h e l a r g e c a r b o n - c o n t a i n i n g ( c e l l u l o s e ) m o l e c u l e s i n t o s m a l l e r , r e a d i l y a s s i m i l a t e d u n i t s . E n z y m e s a r e r e l e a s e d f r o m h y p h a l f i l a m e n t s g r o w i n g i n s i d e t h e w o o d . T h e y r e a d i l y move t h r o u g h t h e wood by d i f f u s i o n a n d c a t a l y z e t h e b r e a k d o w n o f c e l l w a l l s . T h e r e i s e v i d e n c e t o s u g g e s t t h a t t h i s e n z y m a t i c a c t i o n o c c u r s i n a d v a n c e o f t h e g r o w i n g h y p h a e . The p r o c e s s by w h i c h w o o d - d e s t r o y i n g f u n g i grow o n a n i t r o g e n d e f i c i e n t s u b s t r a t e , i . e . , t h e wood o f w h i c h t h e c a r b o n / n i t r o g e n r a t i o may v a r y f r o m a p p r o x i m a t e l y 3 5 0 / 1 t o 1250 /1 ( 2 4 ) , i s s t i l l u n c l e a r a l t h o u g h h y p o t h e s e s h a v e b e e n p r o p o s e d . , B e c a u s e w o o d - d e s t r o y i n g f u n g i must e x c r e t e c e l l u l o l y t i c e n z y m e s t o d i g e s t t h e s u b s t r a t e s , i t i s e a s y t o p o s t u l a t e t h a t s u b s t a n c e s t h a t i n h i b i t e n z y m a t i c a c t i v i t y c o u l d s t a r v e t h e f u n g u s a n d i n h i b i t t h e d e c a y d e v e l o p m e n t . I n a c t i v a t i o n o f e n z y m e s by p h e n o l s h a s b e e n r e p o r t e d e x t e n s i v e l y ( 4 6 , 67 , 6 9 ) , B a s e d o n t h e a b i l i t y o f t h e m i c r o o r g a n i s m s t o m e t a b o l i z e s p e c i f i c wood c o m p o n e n t s t h e y a r e d i v i d e d i n t o d i f f e r e n t c a t e g o r i e s . B a c t e r i a f r e q u e n t l y o c c u r i n b o t h l i v i n g t r e e s a n d i n wood p r o d u c t s ( 1 0 2 ) . N o r m a l l y t h e y c a u s e no s i g n i f i c a n t p r o b l e m s and t h e r e i s h a r d l y a n y c o m p l a i n t r e p o r t e d a b o u t t h e i r damage o n a n y c o m p o s i t i o n m a t e r i a l . T h e m o u l d a n d s a p s t a i n f u n g i m e t a b o l i z e m a i n l y s i m p l e 19 s u g a r s a v a i l a b l e w i t h i n c e l l s , p a r t i c u l a r l y i n t h e s a p w o o d . G e n e r a l l y s p e a k i n g , t h e y do n o t d e g r a d e t h e s t r u c t u r a l c e l l u l o s e o r l i g n i n a n d , t h e r e f o r e , c a u s e no m e c h a n i c a l i n j u r y t o t h e wood. The " c l a s s i c a l " w o o d — d e s t r y o i n g f u n g i w h i c h b e l o n g t o t h e flasidiomycetes h a v e b e e n s t u d i e d f o r a l o n g t i m e . M o s t B a s i d i c m y c e t e s , o n c e e s t a b l i s h e d i n w o o d , grow g u i c k l y t h r o u g h i t a n d d e s t r o y i t f a s t e r t h a n t h e s o f t — r o t f u n g i . S o f t - r o t f u n g i b e l o n g t o t h e l o w e r f u n g i , t h e A s c o m y c e t e s and F u n g i i m p e r f e c t i (30, 90) . The o r g a n i s m s m a i n l y a t t a c k t h e p o l y s a c c h a r i d e c o n s t i t u e n t s o f t h e s e c o n d a r y c e l l w a l l s , w h i l e t h e l i g n i n i s l e f t r e l a t i v e l y u n a f f e c t e d . T h e s e f u n g i c h a r a c t e r i s t i c a l l y move t h r o u g h t h e s e c o n d a r y w a l l s o f t h e e l e m e n t s o f w o o d , l e a v i n g e l o n g a t e d and s p i n d l e - s h a p e d c a v i t i e s f o l l o w i n g t h e a n g l e o f t h e c e l l u l o s e f i b r i l s (23), I n c o n t r a s t t o t h e s o f t — r o t f u n g i , o r g a n i s m s w h i c h c a u s e w h i t e and brown r o t s g e n e r a l l y move t h r o u g h a n d b e t w e e n , a s w e l l a s w i t h i n , wood c e l l w a l l s . T h e f u n g i w h i c h c a u s e w h i t e r o t s a r e g e n e r a l l y a s s u m e d t o be c a p a b l e o f m e t a b o l i z i n g b o t h wood c a r b o h y d r a t e s a n d l i g n i n , a n d t h e r e s u l t i n g wood l o s e s c o l o r . B r o w n - r o t f u n g i a r e r e s t r i c t e d t o u t i l i z a t i o n o f c a r b o h y d r a t e s , , T h e wood t e n d s t o a c g u i r e a brown c o l o r . I n g e n e r a l , f u n g i c a u s i n g b r o w n r o t s t e n d t o i n f e c t g y m n o s p e r m s , w h i l e t h o s e c a u s i n g w h i t e r o t s a r e t y p i c a l l y a s s o c i a t e d w i t h a n g i o s p e r m s . D e t a i l e d d i s c u s s i o n s on f u n g a l a c t i v i t y and i t s r e l a t i o n s h i p w i t h wood h a v e b e e n o f f e r e d i n s e v e r a l w o r k s (14, 19, 49, 93, 101, 119) b e f o r e . 20 7 . D e c a y i n B u i l d i n g s i n R e l a t i o n t o S e t t i n g H o o d - b a s e d m a t e r i a l s a r e m o s t l y u s e d i n b u i l d i n g s a s w a l l c l a d d i n g , u n d e r f l o o r c o v e r i n g , a n d f u r n i t u r e p a r t s . Some a r e u s e d i n t h e c o n s t r u c t i o n o f f a r m b u i l d i n g s where c o n t a c t w i t h a n i m a l s , w a s t e m a t e r i a l s , a n d d i f f e r e n t f o r m s o f w a t e r may r a i s e b o t h t h e m o i s t u r e c o n t e n t and n u t r i e n t l e v e l i n t h e m a t e r i a l s , m a k i n g them s u s c e p t i b l e t o f u n g a l a t t a c k . T h e g r o w t h o f a w o o d - i n h a b i t i n g f u n g i d e p e n d s o n : (1) t h e p r e s e n c e o f f o o d s u p p l y , (2) a d e g u a t e amount o f m o i s t u r e , (3) s u p p l y o f o x y g e n , a n d (4) f a v o r a b l e t e m p e r a t u r e . To p r o t e c t wood o r w o o d - b a s e d m a t e r i a l s i n b u i l d i n g s o r c o n s t r u c t i o n s f r o m d e c a y , t h e f i r s t c o n c e r n i s f o r p r a c t i c a l m e a s u r e s t o e n s u r e u s e o f d r y wood a n d t o k e e p i t d r y a f t e r i t i s i n c l u d e d i n t h e s t r u c t u r e . T h e r e f o r e , an a w a r e n e s s a s t o t h e p o s s i b i l i t i e s a n d c i r c u m s t a n c e s u n d e r w h i c h wood i n b u i l d i n g s becomes s u f f i c i e n t l y wet f o r d e c a y t o t a k e h o l d , s h o u l d be i n c r e a s e d . H a t e r t o s u p p o r t d e c a y c a n a r i s e f r o m f i v e m a i n s o u r c e s ( 9 2 ) : A . O r i g i n a l m o i s t u r e i n u n s e a s o n e d w o o d , B . G r o u n d m o i s t u r e , C . R a i n w a t e r , D. C o n d e n s a t e , a n d E . P i p e d w a t e r . 21 A . I n s t a l l a t i o n o f wet o r i n c o m p l e t e l y d r i e d l u m b e r c a n c a u s e t r o u b l e by p r o v i d i n g m o i s t u r e t o s u p p o r t a t t a c k b y d e c a y f u n g i , o r by e x p o s i n g p l a c e s , t h r o u g h s p l i t t i n g , w a r p i n g o r l o o s e n i n g o f j o i n t s b e c a u s e o f s h r i n k a g e , t o p r o m o t e r a i n s e e p a g e and d e c a y i n f e c t i o n . Wood—based p a n e l m a t e r i a l s a r e u s u a l l y l e s s p r o n e t o s u c h m o i s t u r e e f f e c t s . B . C o n t a c t w i t h damp s o i l c a n b r i n g g r o u n d m o i s t u r e t o wood p a r t s o f b u i l d i n g s . T h e r e a r e a l s o t h e f u n g i ( w a t e r - c o n d u c t i n g f u n g i l i k e P o r i a i n c r a s s a t a [ ( B e r k . & C u r t . ) B u r t ] ) w h i c h t h r o u g h c o n d u c t i n g s t r a n d s c a n c r e a t e c i r c u m s t a n c e s f o r f u n g i t o d e v e l o p e v e n t h o u g h t h e b u i l d i n g s a r e w e l l i s o l a t e d i n t h e i r f o u n d a t i o n s f r o m g r o u n d m o i s t u r e . C . R a i n w a t e r e n t e r s wood l a r g e l y b y c a p i l l a r y movement a n d i s t r a p p e d i n t h e i n t e r f a c i a l s p a c e s b e t w e e n j o i n t members . I t c a n be c a r r i e d i n t o w a l l j o i n t s b y w i n d p r e s s u r e a n d g r a v i t y f l o w . A l s o r a i n s p l a s h i n g o n m a s o n a r y w a l l s w i t h p e r m e a b l e j o i n t s w i l l o c c a s i o n a l l y l e a d t o d e c a y o f t h e wooden j o i n t s o r beams e m b e d d e d i n w a l l s . I t i s v e r y i m p o r t a n t t h a t l o c a l a c c u m u l a t i o n s o f w a t e r n e a r j o i n t s may r a i s e t h e h u m i d i t y o f t h e a i r b e t w e e n s i d i n g a n d s h e a t h i n g . C o o l i n g a t n i g h t r e s u l t s i n c o n d e n s a t i o n on t h e b a c k o f t h e s i d i n g . D. C o n d e n s a t i o n r e s u l t s f r o m c o o l i n g o f m o i s t warm a i r on c o n t a c t w i t h a c o l d s u r f a c e . T h e warmer t h e a i r , t h e more w a t e r v a p o r i t w i l l h o l d . T h e movement o f w a t e r v a p o r t h r o u g h a s t r u c t u r e i n b u i l d i n g s i s g o v e r n e d b y p r e s s u r e g r a d i e n t s w h i c h a r e c r e a t e d by t e m p e r a t u r e d i f f e r e n c e s . Where a d e w p o i n t t e m p e r a t u r e e x i s t s , a n d u n l e s s e n t r y o f v a p o r i n t o w a l l s , c e i l i n g , a n d f l o o r s i s r e s t r i c t e d , d a m a g i n g c o n d e n s a t i o n w i l l 22 o c c u r w i t h i n p e r m e a b l e s t r u c t u r e s s u c h a s w o o d , p l y w o o d , p a r t i c l e b o a r d , h a r d b o a r d , p l a s t e r , a n d c o n c r e t e . I t s h o u l d be n o t e d t h a t when c o n d i t i o n s p r o m o t i n g c o n d e n s a t i o n e x i s t w i t h i n a s t r u c t u r e , t h e u s e o f t h e r m a l i n s u l a t i o n w i t h o u t a v a p o r b a r r i e r w i l l n o t p r e v e n t c o n d e n s a t i o n b u t m e r e l y c h a n g e t h e l o c a t i o n o f t h e p o i n t where t h e d e w p o i n t t e m p e r a t u r e o c c u r s . W e t t i n g by c o n d e n s a t i o n may o c c u r a t l e a s t i n f o u r a r e a s : a . n e a r t h e p e r i m e t e r o f c r a w l s p a c e s i n c o l d w e a t h e r ; b . i n f l o o r s , w a l l s , and c e i l i n g s o f c o l d s t o r a g e r o o m s ; c . i n a r e a s where s i z a b l e a m o u n t s o f s t e a m a r e r e l e a s e d o r u n i n t e n t i o n a l l y a l l o w e d t o e s c a p e ; d . i n t h e f l o o r b e l o w a i r - c o n d i t i o n e d r o o m s o v e r a damp c r a w l s p a c e . E . C e r t a i n c o m p o n e n t s o f a b u i l d i n g may g e t s u f f i c i e n t l y wet t o d e c a y b e c a u s e p l u m b i n g l e a k s a r e n e g l e c t e d . F r e q u e n t l a w n s p r i n k l i n g a n d e x c e s s i v e w a s h i n g may a l s o c a u s e h e a v y w e t t i n g i n wood s i d i n g a n d wood f l o o r s , a n d l e a d t o s u f f i c i e n t m o i s t u r e a c c u m u l a t i o n t o s u p p o r t d e c a y . M e t a b o l i c w a t e r , p r o d u c e d by f u n g u s i t s e l f a s i t b r e a k s down t h e w o o d , w i l l a l s o p r o m o t e d e c a y . T h i s w a t e r w e i g h s a b o u t h a l f a s much a s t h e d e s t r o y e d w o o d ; t h e r e f o r e , i t may b e s u f f i c i e n t t o s u p p o r t d e c a y i n p o o r l y v e n t i l a t e d s p a c e s . 8 . B e a r d D u r a b i l i t y a n d D e c a y V e r y l i t t l e work h a s b e e n d o n e i n t h e p a s t on d e c a y 23 r e s i s t a n c e p r o p e r t i e s o f c o m p o s i t i o n b o a r d s . I n f o r m a t i o n i s p a r t i c u l a r l y s c a r c e on h a r d b o a r d s , t h o u g h t h e d e v e l o p m e n t a n d a p p l i c a t i o n o f t h i s new p r o d u c t h a s b e e n g r o w i n g v e r y f a s t . R e a s o n s f o r t h e l a c k o f i n f o r m a t i o n a r e t w o f o l d : (a) v e r y s h o r t h i s t o r y o f t h e s e new p r o d u c t s c o m p a r e d t o t h a t o f s o l i d wood p r o d u c t s , a n d (b) t h e f a c t t h a t t h e s e p r o d u c t s a r e b e s t s u i t e d f o r i n t e r i o r u s e s where d e c a y i s n o t t h e m a i n c o n c e r n . I g n o r a n c e o f t h i s i m p o r t a n t p r o p e r t y m i g h t i m p e d e f u r t h e r d e v e l o p m e n t b e c a u s e o f u n c e r t a i n t i e s , a n d l a c k o f c o n f i d e n c e . T h e r e f o r e r e s e a r c h work on d e c a y r e s i s t a n c e o f h a r d b o a r d s h o u l d k e e p p a c e w i t h t h e i n d u s t r y ' s e x p a n s i o n t o e n s u r e t h e c o n f i d e n c e t o w a r d t h i s new v e r s a t i l e p r o d u c t . T h e w i d e r a n g e o f wood—based c o m p o s i t i o n m a t e r i a l s a l s o makes t h e i n v e s t i g a t i o n d i f f i c u l t . The v a r i a b l e s i n v o l v e d i n m a n u f a c t u r i n g , e . g . , s p e c i e s o f w o o d , b o n d i n g a g e n t s , d e n s i t y , s u r f a c e t r e a t m e n t s , k i n d and a m o u n t o f a d d i t i v e s , c a n be a l t e r e d t o s u i t a l a r g e number o f e n d - u s e s . S t a n d a r d t e s t m e t h o d s n e e d t o be e s t a b l i s h e d s o t h a t t h e t e s t r e s u l t s i n d i f f e r e n t l a b o r a t o r i e s c a n be c o m p a r a t i v e l y e v a l u a t e d . T h e n e c e s s i t y f o r t h e p r o d u c t i o n o f d u r a b l e b o a r d s o r p r o t e c t i o n o f n o n - d u r a b l e b o a r d s h a s b e e n d i s c u s s e d on s e v e r a l o c c a s i o n s <32, 3 3 , 3 7 , 3 8 , 4 1 , 5 2 , 6 0 , 6 1 ) . T h i s l e d t o a b r o a d f i e l d o f s t u d y , i n c l u d i n g i n v e s t i g a t i o n s i n t o e x t e r i o r d u r a b i l i t y , d e c a y r e s i s t a n c e a n d p r e s e r v a t i v e t r e a t m e n t , b u t m o s t l y r e s t r i c t e d t o t h e e x t e r i o r d u r a b i l i t y s t u d i e s . T h e i n v e s t i g a t i o n i n t o e x t e r i o r d u r a b i l i t y i s i m p o r t a n t i n some c a s e s due t o i t s r e l a t i o n s h i p w i t h t h e d e c a y r e s i s t a n c e p r o p e r t y o f b o a r d s . T h e r e s u l t i n g damage d u r i n g e x t e r i o r s e r v i c e 24 may c r e a t e b e t t e r c o n d i t i o n s f o r f u n g a l a t t a c k ; and f a c t o r s f o u n d i m p o r t a n t i n d e t e r m i n i n g t h e e x t e r i o r d u r a b i l i t y may be s i m i l a r o r c l o s e l y r e l a t e d i n t h e i n v e s t i g a t i o n o f d e c a y r e s i s t a n c e p r o p e r t y . E x t e r i o r t e s t s a r e u s e f u l i n t h a t t h e c o n d i t i o n s o f t h e t e s t s r e f l e c t more c l o s e l y t h o s e e n c o u n t e r e d i n t h e p r a c t i c a l u s a g e o f t h e b o a r d t h a n t h e l a b o r a t o r y t e s t s d o . A l t h o u g h f u n g a l a t t a c k i s n o t t h e p r i m e c o n s i d e r a t i o n i n s u c h t e s t s a n d i n o c u l a t i o n i s n o t d e l i b e r a t e l y c a r r i e d o u t , t h e r e s u l t s a r e i m p o r t a n t i n t h a t t h e y a l s o p r o v i d e i n f o r m a t i o n a b o u t t h e e f f e c t s o f m o i s t u r e . W e a t h e r p r o o f i n g i s j u s t a s n e c e s s a r y a s t r e a t i n g w i t h f u n g i c i d e when t h e b o a r d i s t o be u s e d o u t d o o r s . Damage i s u s u a l l y e s t i m a t e d v i s u a l l y a n d / o r b y s t r e n g t h l o s s m e a s u r e m e n t s . C y c l i c a l c h a n g e s i n t e m p e r a t u r e a n d h u m i d i t y b e s i d e s t h e b o n d i n g a g e n t t y p e , were f o u n d t o be t h e m a i n f a c t o r s i n d u r a b i l i t y o f p a r t i c l e b o a r d s ( 3 8 ) . R e s i s t a n c e t o s w e l l i n g and o t h e r d i m e n s i o n a l c h a n g e s i s t h e most u s e f u l c r i t e r i a f o r a s s e s s i n g e x t e r i o r d u r a b i l i t y . R e s i n c o n t e n t was f o u n d t o be t h e most i m p o r t a n t s i n g l e v a r i a b l e c o n t r i b u t i n g t o h i g h r e s i s t a n c e v a l u e s ( 3 2 ) . P a r t i c l e b o a r d i s i n t e r m e d i a t e b e t w e e n e x t e r i o r p l y w o o d a n d h i g h d e n s i t y h a r d b o a r d w i t h r e s p e c t t o t h e c h a n g e s i n t h i c k n e s s a n d l i n e a r d i m e n s i o n s ( 4 1 ) . R u f f i n ( 8 7 ) , i n a r e p o r t c o n c e r n e d m a i n l y w i t h t h e e f f e c t o f wood s p e c i e s a n d d e g r e e o f h y d r o l y s i s d u r i n g m a n u f a c t u r e , l i s t e d s e v e r a l f a c t o r s w h i c h m i g h t a f f e c t t h e d u r a b i l i t y o f h a r d b o a r d . F a c t o r s s u c h a s wood s p e c i e s , s e v e r i t y o f h y d r o l y s i s o r h e a t t r e a t m e n t on f i b e r s , t y p e a n d a m o u n t o f b i n d e r , w a t e r 25 r e p e l l e n c y a n d o t h e r a d d i t i v e s , d e g r e e and u n i f o r m i t y o f f i b e r r e f i n i n g a n d s h e e t f o r m a t i o n , d e n s i t y a n d s e v e r i t y o f e x p o s u r e a r e m a i n l y r e s p o n s i b l e f o r t h e v a r i a t i o n s i n t h e h a r d b o a r d q u a l i t y . I n f o r m a t i o n on i n d i v i d u a l v a r i a b l e e f f e c t s o n d u r a b i l i t y ( d e c a y r e s i s t a n c e ) o f h a r d b o a r d a r e l a r g e l y l a c k i n g . 9 , D e c a y i n C o m p o s i t i o n B o a r d M a t e r i a l s Some s t u d i e s h a v e b e e n made on t h e d e c a y r e s i s t a n c e o f w o o d - b a s e d c o m p o s i t e b o a r d s , p a r t i c u l a r l y p a r t i c l e b o a r d s . B u t t h e r e s u l t s a r e o f t e n d i f f i c u l t t o e v a l u a t e d u e t o t h e l a r g e number o f d i f f e r e n t b o a r d t y p e s a n d t h e c o r r e s p o n d i n g v a r i a b l e s . &. P a r t i c l e b o a r d s D u r i n g t h e p a s t d e c a d e , r e s e a r c h i n v e s t i g a t i n g p a r t i c l e b o a r d d u r a b i l i t y h a s d e t e r m i n e d t h a t wood s p e c i e s , p a r t i c l e g e o m e t r y , b o a r d s t r u c t u r e a n d d e n s i t y a s w e l l a s t y p e and amount o f a d h e s i v e a r e a l l i n v o l v e d i n s u s c e p t i b i l i t y o f p a r t i c l e b o a r d t o f u n g i ( 1 0 1 , 1 2 0 ) . I n a n i n v e s t i g a t i o n i n t o t h e e f f e c t o f v a r i a b l e s o f p a r t i c l e b o a r d o n s o i l - b l o c k t e s t r e s u l t s w i t h P o r i a m o n t i c o ^ a M u r r . a n d L e n z i t e s t r a b e a P e r s . e x F r . , C l a r k (20) i n d i c a t e d t h a t i n c r e a s e d d e c a y r e s i s t a n c e m i g h t be a t t a i n e d b y u s i n g n a t u r a l l y r e s i s t a n t wood ( e . g . , w e s t e r n r e d c e d a r ) o r i n c r e a s i n g t h e amount o f t h e u r e a - f o r m a l d e h y d e b i n d e r . I n c r e a s i n g t h e 26 amount o f PF r e s i n s ( f r o m 3 t o 6 p e r c e n t ) o r a d d i n g wax d i d n o t a p p r e c i a b l y i n c r e a s e r e s i s t a n c e o f t h e b o a r d s . H o w e v e r , o t h e r i n v e s t i g a t i o n s o f r e s i n a n d r e s i n — w o o d b o n d d u r a b i l i t y h a v e g e n e r a l l y shown t h a t P F r e s i n s w e r e more r e s i s t a n t t o f u n g a l a t t a c k t h a n UF r e s i n s { 1 3 ) . T h e P F - b o n d e d b o a r d i s c o n s i d e r e d w e l l p r o t e c t e d a g a i n s t t h e a c t i v i t i e s o f f u n g i due t o i t s h i g h pH and a b u n d a n c e o f n o n c o n d e n s e d p h e n o l s ( 2 8 ) . I n a s e r v i c e s i t u a t i o n where l e a c h i n g may o c c u r , t h e d e c a y s u s c e p t i b i l i t y o f p a r t i c l e b o a r d i s g r e a t l y i n c r e a s e d , s o t h a t f u n g i c i d e p r o t e c t i o n was c o n s i d e r e d n e c e s s a r y ( 6 , 8 1 , 1 1 6 ) , T h e r e c o m m e n d a t i o n was made t h a t u r e a - b o n d e d p a r t i c l e b o a r d s h o u l d n o t b e u s e d i n s i t u a t i o n s w h e r e t h e m o i s t u r e c o n t e n t may e x c e e d 18 p e r c e n t ( 8 1 ) . F a c t o r s a f f e c t i n g b i o l o g i c a l a n d p h y s i c a l d e g r a d a t i o n o f p a r t i c l e b o a r d a r e t h u s c l o s e l y r e l a t e d : u p t a k e o f m o i s t u r e w i l l p r o m o t e b o t h r e d u c t i o n i n s t r e n g t h c a u s e d b y s w e l l i n g o f t h e wood p a r t i c l e s a n d c o n s e g u e n t g l u e f a i l u r e , and d e s t r u c t i o n by d e c a y f u n g i . U s i n g w e i g h t - l o s s m e a s u r e m e n t s on P F - a n d U F ~ b o n d e d b o a r d s a t t a c k e d by B a s i d i o m y c e t e s , S t o l l e y (109) f o u n d t h a t a l t h o u g h p a r t i c l e b o a r d s a r e l e s s s u s c e p t i b l e t h a n t i m b e r t h e y were d e f i n i t e l y n o t f u l l y r e s i s t a n t t o d e c a y . T e s t b l o c k s a l s o s h o w e d g u i t e h i g h l o s s e s i n m e c h a n i c a l s t r e n g t h a f t e r e x p o s u r e t o f u n g a l a t t a c k . S t r e n g t h t e s t i n g h a s bjsen h i g h l y r e c o m m e n d e d f o r u s e i n c o n j u n c t i o n w i t h w e i g h t - l o s s d e t e r m i n a t i o n s t o show t h e e x t e n t o f d e c a y . I n p r a c t i c e t h i s i s p r o b a b l y a r a t h e r s u b j e c t i v e p r o c e d u r e . I t h a s b e e n f o u n d t h a t b o a r d s c o n t a i n i n g m i x e d h a r d w o o d a n d s o f t w o o d c h i p s a r e d e c a y e d more t h a n t h o s e made o f s o f t w o o d 27 c h i p s a l o n e (121) . As c o m p o s i t i o n b o a r d s , i n c l u d i n g p a r t i c l e b o a r d s a n d f i b e r b o a r d s , have h i g h s u r f a c e - t o - v o l u m e r a t i o s , t h e y a r e r a p i d l y a f f e c t e d by w e a t h e r c o n d i t i o n s a n d w i l l be w e t t e d a n d d r i e d o u t e a s i l y , t h u s o f t e n p r o v i d i n g m o i s t u r e c o n d i t i o n s i n t e r m i t t e n l y s u i t a b l e f o r f u n g a l g r o w t h , c o n d i t i o n s i n w h i c h m i c r o f u n g i r a t h e r t h a n w o o d - d e s t r o y i n g B a s i d i o m y c e t e s a r e l i k e l y t o e f f e c t c o l o n i z a t i o n ( 5 0 ) , I n l a b o r a t o r y t e s t s t o d e t e r m i n e t h e e f f e c t o f f u n g a l a t t a c k a n d w a t e r s o a k i n g o n t h e i n t e r n a l b o n d (IB) s t r e n g t h a n d s t a t i c b e n d i n g p r o p e r t i e s ( M O B a n d MOE) o f a v a r i e t y o f c o m m e r c i a l l y p r o d u c e d p h e n o l — a n d u r e a — b o n d e d , g r a d e d — d e n s i t y p a r t i c l e b o a r d s , S c h m i d t e t a l , (94) f o u n d t h a t s t r e n g t h l o s s e s on b o a r d s a m p l e s i n c u b a t e d w i t h f u n g i were c o n s i d e r a b l y g r e a t e r t h a n l o s s e s i n s a m p l e s s u b m e r g e d f o r e x t e n d e d p e r i o d s i n w a t e r , B, F i b e r b o a r d s I n s u l a t i n g b o a r d s a n d h a r d b o a r d s a s w e l l as p a r t i c l e b o a r d s a r e l i a b l e t o a t t a c k by a v e r y w i d e r a n g e o f f u n g i , f r o m w o o d — r o t t i n g B a s i d i o m y c e t e s t o m o u l d s p e c i e s ( 7 1 ) . A k a i a n d Oeyama ( 1 ) , u s i n g common w o o d — d e s t r o y i n g B a s i d i o m y c e t e s i n t e s t s o n h a r d b o a r d and o t h e r c o m p o s i t e b o a r d s , f o u n d t h a t a f t e r 100 d a y s i n c u b a t i o n w i t h P o r i a v a p o r a r i a F r . s e n s u B r e s , , h a r d b o a r d l o s t 50 p e r c e n t w e i g h t w h i l e p a r t i c l e b o a r d showed a l o s s o f o n l y 10 p e r c e n t . I t was a l s o d e m o n s t r a t e d t h a t t e m p e r e d a n d n o n - t e m p e r e d h a r d b o a r d s u f f e r e d s i m i l a r w e i g h t l o s s e s . . A l t h o u g h k n o w l e d g e i n t h i s r e g a r d i s n o t c o m p l e t e t h e r e i s 2 8 b a s i c a g r e e m e n t t h a t s u b s t a n t i a l c h e m i c a l c h a n g e s t a k e p l a c e d u r i n g t h e b o a r d m a n u f a c t u r i n g p r o c e s s , e . g . , a l t e r a t i o n o f l i g n i n a n d h y d r o l y s i s o f c e l l u l o s e . H y d r o l y s i s a n d r e m o v a l o f h e m i c e l l u l o s e i s more p r o n o u n c e d w i t h M a s o n i t e t y p e h a r d b o a r d ( 6 5 ) . P u l p w a s h i n g r e m o v e s m i n e r a l s a l t s a n d s o l u b l e c a r b o h y d r a t e m a t e r i a l a l s o , f r o m f i b e r s u s e d f o r b o a r d p r o d u c t i o n by t h e A s p l u n d p r o c e s s . Much i n t e r e s t h a s i n f a c t b e e n c e n t e r e d on t h e r o l e o f m o u l d s i n t h e a t t a c k and d e c a y o f f i b e r b o a r d s (72 , 7 6 ) . I t was s u g g e s t e d t h a t t h e y c o u l d p r o b a b l y a t t a c k wood a t a l o w e r m o i s t u r e c o n t e n t t h a n c o u l d B a s i d i c m y c e t e f u n g i ( 7 4 ) . By means o f s t r e n g t h l o s s , w e i g h t l o s s a n d c h e m i c a l c o m p o s i t i o n t e s t s i t was f o u n d t h a t m o s t o f t h e m o u l d s were s i m i l a r i n t h e i r a c t i o n t o t h e b r o w n - r o t t i n g t r a b e a e x c e p t f o r a s l o w e r r a t e o f a t t a c k , A p o s s i b l e e x p l a n a t i o n f o r t h i s s u s c e p t i b i l i t y t o m o u l d a t t a c k was a d v a n c e d i n t h a t t h e l i g n i n i s a l t e r e d o r r e p o s i t i o n e d i n some way d u r i n g t h e m a n u f a c t u r i n g p r o c e s s , t h u s p e r m i t t i n g e a s i e r a c c e s s t o t h e c e l l u l o s e m a t e r i a l . On b a s i s o f m i c r o s c o p i c e x a m i n a t i o n o f d e c a y e d f i b e r b o a r d s , M e r r i l l (76) a n d M e r r i l l a n d F r e n c h (72) s u g g e s t e d t h a t , s i n c e t h e b o a r d s were c o m p o s e d o f i n d i v i d u a l f i b e r s , t h e S2 l a y e r o f t h e c e l l w a l l w o u l d be e x p o s e d a t t h e b r o k e n e n d s , t h u s m a k i n g n u t r i e n t s a v a i l a b l e w i t h o u t t h e n e e d f o r p e n e t r a t i o n t h r o u g h t h e w a l l f r o m t h e l u m e n . T h i s e x p l a n a t i o n may n o t h o l d t r u e i n t h e c a s e o f p a r t i c l e b o a r d s . W i t h e x p a n s i o n o f m a r k e t s f o r p a n e l p r o d u c t s p a r t l y d e p e n d e n t on c o n s t r u c t i o n a n d e x t e r i o r a p p l i c a t i o n s , s u c h b o a r d s a r e e x p e c t e d t o be r e s i s t a n t t o b i o d e t e r i o r a t i o n , e i t h e r b y 29 a d d i t i o n o f p r e s e r v a t i v e s (8) o r by s e l e c t i o n o f raw m a t e r i a l . . n a t u r a l r e s i s t a n c e i m p a r t e d by t h e wood s o u r c e i s one c f t h e p o s s i b l e ways t o o b t a i n more d u r a b l e b o a r d s . C o m p a r i n g t h e d e c a y r e s i s t a n c e o f f i b e r b o a r d s made f r o m n o r t h e r n w h i t e c e d a r I ? . h y j § g c c i d e n t a l i s L . ) , m i x e d n o r t h e r n h a r d w o o d p l a n i n g m i l l r e s i d u e s and d e b a r k e r s c r a p s , h a r d w o o d s a w d u s t , o r m i x e d h a r d w o o d t r e e - t o p s , B e h r (10) r e p o r t e d t h a t b o a r d s o f a w h i t e c e d a r h e a r t w o o d - s a p w o c d m i x t u r e w e r e more r e s i s t a n t t o t e r m i t e s t h a n t h e c o n t r o l s o f c e d a r o r s o u t h e r n p i n e ( p i n u s L . ) s a p w o o d . T h e f o r m e r w e r e a l s o more r e s i s t a n t t h a n b o a r d s made o f 50 p e r c e n t c e d a r o r a l l h a r d w o o d r e s i d u e . A l l s u c h b o a r d s were more r e s i s t a n t t o d e c a y c a u s e d by L t % ; r a b e a o r P . m o n t i c o l a t h a n a s p e n o r t h e s o u t h e r n p i n e s a p w o o d c o n t r o l s , b u t l e s s r e s i s t a n t t h a n t h e n o r t h e r n w h i t e c e d a r h e a r t w o o d c o n t r o l . B o t h e x t r a c t i v e c o n t e n t a n d h a r d n e s s a p p e a r t o h a v e c o n t r i b u t e d t o t e r m i t e r e s i s t a n c e o f s a m p l e s u s e d i n t h i s e x p e r i m e n t . T h e h i g h t e m p e r a t u r e s a n d s t e a m e n c o u n t e r e d i n t h e m a n u f a c t u r e o f t h e m e d i u m - d e n s i t y f i b e r b o a r d s may h a v e c a u s e d a l o s s o f seme o f t h e e x t r a c t i v e s r e s p o n s i b l e f o r d e c a y r e s i s t a n c e o f i n t a c t h e a r t w o o d . H e a r t w o o d e x t r a c t i v e s c f w e s t e r n r e d c e d a r ( fJ^jaJS p l i c a t a Dcnn) , f o r e x a m p l e , i s a b l e t o i n h i b i t t h e g r o w t h o f w o o d - d e s t r o y i n g f u n g i a n d , t h e r e f o r e , makes t h i s wood f a m o u s f o r i t s h i g h d e c a y r e s i s t a n c e p r o p e r t y . A n o t h e r r e a s o n f o r g r e a t e r d e c a y s u s c e p t i b i l i t y i n t h e f i b e r b o a r d s , c o m p a r e d t o s o l i d wood o r p a r t i c l e b o a r d s o f s i m i l a r c o m p o s i t i o n , i s t h e i n t e r n a l s t r u c t u r e o f t h e b o a r d s . T h e wood f i b e r i s i n s u c h a f i n e s t a t e o f d i v i s i o n w i t h i n f i b e r b o a r d s t h a t more s u r f a c e i s e x p o s e d t o a t t a c k / u n d e r s w o l l e n c o n d i t i o n s 30 t h a n i n t h e c a s e o f p a r t i c l e b o a r d s . I t has b e e n s u g g e s t e d t h a t f i b e r b o a r d s h a v e i n c r e a s e d s u s c e p t i b i l i t y t o m o u l d a t t a c k b e c a u s e t h e s e m i c r o o r g a n i s m s have e a s i e r a c c e s s t o t h e c e l l u l o s e . T h e same may be t r u e i n r e l a t i o n t o d e c a y f u n g i ( 7 5 ) . 10 . P r o t e c t i o n A g a i n s t D e c a y A . G e n e r a l Wood p r o d u c t s w i t h o u t n a t u r a l r e s i s t a n c e a g a i n s t o r g a n i s m s n e e d t o be p r o t e c t e d i f t h e e n v i r o n m e n t a l c o n d i t i o n s u n d e r w h i c h t h e y a r e i n s e r v i c e make a t t a c k p o s s i b l e . Wood p r e s e r v a t i v e s i m p a r t good r e s i s t a n c e a g a i n s t d e t e r i o r a t i n g a g e n t s , b u t must n o t be d a n g e r o u s t o h u m a n s . M o s t tiood p r e s e r v a t i v e s a r e i m p r e g n a t e d i n t o t h e wood c e l l s u s i n g e i t h e r v a c u u m , p r e s s u r e , o r a c o m b i n a t i o n o f b o t h . T h e p r o c e s s e s a r e d e s i g n e d t o m a x i m i z e t h e p e n e t r a t i o n o f p r e s e r v a t i v e i n t o wood w h i l e k e e p i n g any d e t r i m e n t a l e f f e c t on s t r e n g t h t o a m i n i m u m . O t h e r m e t h o d s c f a p p l y i n g wood p r e s e r v a t i v e s i n v o l v e s u r f a c e t r e a t m e n t by b r u s h i n g , s p r a y i n g o r d i p p i n g , a n d t h e s a p r e p l a c e m e n t method ( 8 6 ) . Hood p r e s e r v a t i v e s c a n be a r r a n g e d i n t o two b r o a d g r o u p s o f ( a ) . i f a t e r - s o l u b l e i n o r g a n i c s a l t s a n d (b) , o r g a n i c — s o l v e n t s u b s t a n c e s . ( a ) . H a t e r - s o l u b l e i n o r g a n i c s a l t s T h e s e i n v o l v e c h e m i c a l s w h i c h a r e s o l u b l e i n w a t e r , t o x i c 31 t o f u n g i , a n d p r e f e r a b l y show some a b i l i t y f o r f i x a t i o n i n t h e w o o d , t h e r e b y p r e v e n t i n g t h e i r s u b s e q u e n t l e a c h i n g f r o m wood when i n c o n t a c t w i t h w a t e r . C o m p o u n d s o f c o p p e r , z i n c , a r s e n i c , t i n , f l u o r i n e and b o r o n h a v e l o n g h i s t o r i e s a s wood p r e s e r v a t i v e s . T h e a d d i t i o n o f c h r o m i u m c o m p o u n d s f o r r e n d e r i n g t h e e t h e r s a l t s more o r l e s s s t a b l e a g a i n s t l e a c h i n g i s s t i l l t h e o n l y s o l u t i o n f o r s u c c e s s f u l p e r f o r m a n c e o f w a t e r - s o l u b l e p r e s e r v a t i v e s i n wood e x p o s e d t o r a i n o r wet s o i l ( 7 ) . A p p r o v e d f o r m u l a t i o n s o f p r e s e r v a t i v e s u s e d i n C a n a d a a r e c o v e r e d by S t a n d a r d C S A - 0 8 0 Hood P r e s e r v a t i o n ( 1 8 ) . Good e x a m p l e s o f s u c h f o r m u l a t i o n s a r e C C A ( c h r o m a t e d c o p p e r a r s e n a t e ) , A C A ( a m m o n i a c a l c o p p e r a r s e n a t e ) , CAA ( c o p p e r a r s e n i c a d d i t i v e ) , t h e f i r s t two o f w h i c h f o r m t h e b u l k o f w a t e r - b o r n e p r e s e r v a t i v e s c u r r e n t l y u s e d i n C a n a d a ( 1 0 5 ) . ( b ) . O r g a n i c - s o l v e n t s u b s t a n c e s C r e o s o t e , p e n t a c h l o r o p h e n o l a n d c o p p e r n a p h t h e n a t e a r e p r o b a b l y t h e t h r e e b e s t known e x a m p l e s o f t h e s e c h e m i c a l s i n C a n a d a . P r e p a r a t i o n o f p r e s e r v a t i v e s i n o i l c a r r i e r h a s t h e a d v a n t a g e o f b e i n g r e a s o n a b l y r e s i s t a n t t o l e a c h i n g . T h e s e p r e s e r v a t i v e s a r e most s u i t a b l e f o r e x t e r i o r a p p l i c a t i o n s . T h e d e v e l o p m e n t o f o r g a n i c s o l v e n t - t y p e wood p r e s e r v a t i v e s i n c l u d e s c o m b i n a t i o n s o f s p e c i a l f r a c t i o n s o f c r e o s o t e a n d v a r i o u s o t h e r o r g a n i c s u b s t a n c e s w i t h d i f f e r e n t c a r r i e r s a n d a d d i t i o n s f o r s p e c i a l p u r p o s e s (70 , 4 4 ) . Deep p e n e t r a t i o n , l a c k o f c o l o r , l i t t l e o d o u r , e a s y g l u i n g and p a i n t i n g o f t h e t r e a t e d wood were d e s i r e d p r o p e r t i e s i n a d d i t i o n t o t h e e f f e c t i v e n e s s o f t h e s e p r o d u c t s . 32 E x t e n s i v e c o v e r a g e o f a l l t h e p r e s e r v a t i v e s t h a t h a v e been t e s t e d a n d u s e d a s w e l l a s t h e d e s c r i p t i o n c f t h e p r e s e r v a t i o n p r o c e s s e s c a n be f o u n d i n t h e l i t e r a t u r e ( 1 9 , 3 9 , 4 9 ) . Some n o n - c o n v e n t i o n a l wood p r e s e r v a t i o n m e t h o d s h a v e b e e n r e v i e w e d by B o w e l l ( 8 6 ) ; t h e s e i n c l u d e : (1) i r r a d i a t i o n , (2) t h i a m i n e d e s t r u c t i o n , (3) h e a t t r e a t m e n t , (4) p l a s t i c c o m p o s i t e s , (5) r e p e l l e n t s , (6) b o u n d t o x i n s , (7) m e t a b o l i c d i f f e r e n c e , and (8) c h e m i c a l m o d i f i c a t i o n . fin i m p o r t a n t p a r t o f t h e c o n c l u s i o n s i s t h a t t o x i c c h e m i c a l s w h i c h a r e p e r m a n e n t l y b c u n d t o wood c o m p o n e n t s may be c o n s i d e r e d as e n v i r o n m e n t a l l y p r e f e r a b l e p r e s e r v a t i o n m e t h o d s . B . T r e a t m e n t o f C o m p o s i t i o n M a t e r i a l s T h e c h o i c e o f p r o p e r p r e s e r v a t i v e s a n d m e t h o d s o f t h e i r a p p l i c a t i o n i n t r e a t i n g p a r t i c l e b o a r d a n d f i b e r b o a r d i s v e r y d i f f i c u l t . P r e s e r v a t i v e s u s e d f o r t h a t p u r p o s e a r e v e r y o f t e n i n c o m p a t i b l e w i t h t h e t e c h n o l o g i c a l p r o c e s s e s u s e d i n t h e m a n u f a c t u r e o f s u c h b o a r d m a t e r i a l s . I n m o s t c a s e s , p r e s e r v a t i v e s d e t r i m e n t a l l y a f f e c t p h y s i c a l a n d m e c h a n i c a l p r o p e r t i e s o f m a n u f a c t u r e d b o a r d m a t e r i a l s . among f i v e m e t h o d s o f p r e s e r v a t i v e t r e a t m e n t i n p a r t i c l e b o a r d s m e n t i o n e d by Deppe a n d G e r s o n d e ( 2 8 ) , o n l y two 33 m e t h o d s a r e b e i n g u s e d o n a l a r g e s c a l e : (1) i r i x i n g c f t h e p r e s e r v a t i v e w i t h t h e r e s i n a n d common o r s i m u l t a n e o u s ( b u t s e p a r a t e ) s p r a y i n g o f b o t h f l u i d s i n t h e b l e n d e r , a n d (2) a p p l i c a t i o n o f t h e p r e s e r v a t i v e as powder b e f o r e , d u r i n g , o r a f t e r g l u i n g . A t r e a t m e n t o f t h e f i n i s h e d b o a r d may n o t y i e l d t h e e x p e c t e d p r e s e r v a t i v e e f f e c t s i f t h e p e n e t r a t i o n o f t h e c h e m i c a l s t h r o u g h t h e h i g h l y c o m p r e s s e d s u r f a c e was i n s u f f i c i e n t . T r e a t i n g t h e p a n e l s a f t e r p r o d u c t i o n a l s o c a l l s f o r e x p e n s i v e p r e s s u r e t r e a t i n g f a c i l i t i e s w h i l e l i t t l e i s a d d e d t o t h e p r o d u c t i o n c o s t e x c l u d i n g t h e p r e s e r v a t i v e c o s t i f t h e b o a r d i s t r e a t e d d u r i n g t h e s t a g e s o f m a n u f a c t u r e . S e v e r a l k i n d s o f p r e s e r v a t i v e h a v e b e e n u s e d a n d e v a l u a t e d by many r e s e a r c h e r s . I t i s w i d e l y a c c e p t e d t h a t p e n t a c h l o r o p h e n o l and i t s s a l t s , i n c l u d i n g N a - P C P a n d C o p p e r - P C P , a r e e f f e c t i v e f o r p r o t e c t i n g b u i l d i n g b o a r d s a g a i n s t f u n g a l a t t a c k ( 8 , 4 3 , 4 8 , 7 1 , 7 9 , 8 0 , 1 1 8 ) . O t h e r c h e m i c a l s t e s t e d were B H C ( B e n z e n e h e x a c h l o r i d e ) , " X y l a m o n " , c o p p e r n a p h t h e n a t e , C C A . 3<i 1-1. L a b o r a t o r y T e s t M e t h o d s f o r D e c a y R e s i s t a n c e A . G e n e r a l D e v e l o p m e n t o f e f f e c t i v e p r e s e r v a t i v e s demand an e x p l a n a t i o n o f how a n d t o what e x t e n t t h e s e c h e m i c a l s a r e a b l e t o p r o t e c t wood f r o m f u n g i . N u m e r o u s l a b o r a t o r y m e t h o d s h a v e b e e n d e v e l o p e d f o r e v a l u a t i o n o f p o t e n t i a l wood p r e s e r v a t i v e s o v e r t h e l a s t 80 y e a r s . T h e s e t e s t s c a n a l s o s e r v e t h e p u r p o s e o f c o m p a r a t i v e e v a l u a t i o n o f e x i s t i n g p r e s e r v a t i v e s , s t u d y c f r e l a t i v e p e r f o r m a n c e s u n d e r l a b o r a t o r y c o n d i t i o n s , e v a l u a t i o n o f a l t e r e d f o r m u l a t i o n s , q u a l i t y c o n t r o l , and o t h e r s (11, 6 2 ) . (a) . F u n g a l g r o w t h m e t h o d s F u n g a l g r o w t h m e t h o d s w h i c h m e a s u r e t h e r a t e o f g r o w t h c f f u n g i on a g a r m e d i a c o n t a i n i n g p r e s e r v a t i v e s a m p l e s h a v e been u s e d w i d e l y f o r t h e p r e l i m i n a r y s c r e e n i n g o f p o t e n t i a l p r e s e r v a t i v e s . H o w e v e r , t h i s t y p e o f t e s t d o e s n o t e v a l u a t e t h e e f f e c t i v e n e s s o f t h e p r e s e r v a t i v e i n wood p r o d u c t s . A m o d i f i e d method w h i c h p r o v i d e s r a p i d s c r e e n i n g h a s b e e n p r o p o s e d r e c e n t l y and u s e s a c e l l u l o s i c s u b s t r a t e i n s t e a d o f a g a r ( 2 9 ) . (b) . H e i g h t - l o s s m e t h o d s D e t e r m i n a t i o n o f w e i g h t l o s s due t o d e c o m p o s i t i o n by f u n g i i n wood h a s become t h e s t a n d a r d method f o r p r e s e r v a t i v e e v a l u a t i o n . T h i s t y p e o f t e s t i s e s p e c i a l l y w e l l s u i t e d f o r d e t e r m i n i n g p r e s e r v a t i v e t h r e s h o l d s a s t h e wood f o r t h i s t e s t 35 c a n be t r e a t e d w i t h d i f f e r e n t c o n c e n t r a t i o n s o f c h e m i c a l s . M o s t n a t i o n a l s t a n d a r d s p r e f e r t h e w e i g h t - l o s s m e t h o d , e . g . , ASTM D 1 4 1 3 , BS 838 , DIN 5 2 1 7 6 , e t c . I n E u r o p e most s t a n d a r d t e s t s u s e a g a r - b l o c k m e t h o d . , B a s i c a l l y , t h e t e s t f u n g u s i s g r o w n on s t e r i l e m a l t — a g a r i n a K o l l e f l a s k u n t i l t h e medium i s w e l l c o v e r e d w i t h m y c e l i u m . . T h e n a s t e r i l e g l a s s s u p p o r t r o d i s p l a c e d o n t h e f u n g u s m a t , a n d b l o c k s o f w o o d , t r e a t e d o r u n t r e a t e d , a r e s e t on t h e s u p p o r t r o d so t h a t t h e b l o c k s do n o t t o u c h t h e m a l t - a g a r b u t t h e f u n g u s i s a b l e t o r e a c h t h e b l o c k s . D e g r e e o f a t t a c k i s m e a s u r e d by t h e d i f f e r e n c e i n o v e n - d r y w e i g h t b e f o r e e x p o s u r e t o t h e f u n g u s and t h e o v e n - d r y w e i g h t a f t e r 3 t o 4 months e x p o s e d t o t h e c u l t u r e . R e c o r d e d v i s u a l e x a m i n a t i o n i s a s u p p l e m e n t t o t h e w e i g h t - l e s s p e r c e n t a g e s . M o d i f i e d m e t h o d s a r e a v a i l a b l e t o s h o r t e n t h e t e s t o r l e s s e n t h e c o s t o f e g u i p m e n t , C o c k c r . o f t (22) h a s r e v i e w e d r e s u l t s o b t a i n e d by s e v e r a l r e s e a r c h e r s u s i n g t h e a g a r - b l o c k m e t h o d . I n N o r t h A m e r i c a t h e s o i l - b l o c k m e t h o d a s o u t l i n e d i n AHPA S t a n d a r d M i O - 7 7 (4) o r ASTM S t a n d a r d D 1 4 1 3 - 7 6 (2) i s t h e most w i d e l y u s e d . I t i s much l i k e t h e a g a r - b l o c k t e s t , e x c e p t t h a t s o i l i s u s e d a s t h e s u b s t r a t e f o r g r o w i n g t h e f u n g u s . Wood b l o c k s a r e e x p o s e d t o a f u n g u s g r o w i n g on u n t r e a t e d wood f e e d e r s t r i p s on s t e r i l i z e d s o i l . T e s t b l o c k s a r e w e i g h e d b e f o r e and a f t e r 12 w e e k s * e x p o s u r e t o t h e f u n g u s c u l t u r e . T h e a d v a n t a g e s o f u s i n g s o i l a s t h e medium i n s t e a d o f a g a r i n b l o c k t e s t a r e : (1) . h i g h e r w a t e r h o l d i n g c a p a c i t y o v e r a g a r i n t h a t t h e M . C . c a n be b e t t e r c o n t r c l l e d i n l e n g t h y t e s t s , a n d 36 ( i i ) . t h e a b i l i t y t o a b s o r b t o x i c s u b s t a n c e s f r o m t h e s u b s t r a t e , w h i c h w i l l o t h e r w i s e a f f e c t g r o w t h o f f u n g i . T h e s o i l - b l o c k m e t h o d n o r m a l l y g i v e s h i g h e r v a l u e s f o r p r e s e r v a t i v e t h r e s h o l d s t h a n t h e - a g a r - b l o c k , m e t h o d ( 8 4 ) , ( c ) . S t r e n g t h - l o s s m e t h o d s The s t r e n g t h o f d e c a y i n g wood d r o p s much more r a p i d l y t h a n i t s w e i g h t . T h e r e f o r e , i t i s t h e o r e t i c a l l y p o s s i b l e t o u s e s t r e n g t h l o s s f o r r a p i d d e t e r m i n a t i o n o f e f f e c t i v e n e s s o f p r e s e r v a t i v e s . Many k i n d s o f s t r e n g t h c r i t e r i a w e r e e m p l o y e d a n d a l m o s t a n e g u a l number o f t e s t i n g d e v i c e s f o r e v a l u a t i n g t h e s t r e n g t h s h a v e b e e n u s e d . H a r t l e y (40) i n h i s r e v i e w d e s c r i b e s h a r d n e s s , c r u s h i n g , t e n s i l e a n d v a r i o u s b e n d i n g a n d t o u g h n e s s t e s t s . C r u s h i n g s t r e n g t h h a s b e e n u s e d by T o o l e (114) a s a method t o e v a l u a t e p e n t a c h l o r o p h e n c l a s wood p r e s e r v a t i v e . S h a r p a n d E g g i n s (95) e v o l v e d a r a p i d s t r e n g t h method f o r d e t e r m i n i n g t h e b i o d e t e r i o r a t i o n o f w o o d . I n e s s e n c e , t h e t e c h n i g u e c o n s i s t s o f two c l a m p s f o r a t e n s i c m e t e r w h i c h s u p p o r t s h o r i z o n t a l l y a t h i n s t r i p o f v e n e e r , s o t h a t when t h e c l a m p s move a p a r t t h e v e n e e r i s made t o b e n d u n t i l f r a c t u r e o c c u r s . B r a v e r y a n d G r a n t (15) a l s o u s e a t e n s i l e s t r e n g t h t e s t o n t h i n s t r i p s . T h e l a t e s t m e t h o d , d e v e l o p e d by Safo—Sampah a n d Graham (89) t o d e t e r m i n e t h e d e c a y c a p a c i t y o f f u n g i i s o l a t e d f r o m wood i n s e r v i c e , was c a l l e d b r e a k i n g r a d i u s t e s t . The m a j o r d r a w b a c k o f s t r e n g t h - l o s s m e t h o d s i s t h e i n h e r e n t v a r i a b i l i t y i n t h e s t r e n g t h p r o p e r t i e s o f w o o d . I t i s a l s o d i f f i c u l t t o f i n d c o m p a t i b i l i t y i n s p e c i m e n s i z e u s e d i n w e i g h t -37 l o s s a n d s t r e n g t h - l o s s m e t h o d s i f b o t h w e r e a d o p t e d i n s i n g l e t e s t . ( d ) . R e s p i r c m e t r y m e t h o d s a r a t h e r new m e t h o d i n m e a s u r i n g t h e d e c a y c a u s e d by f u n g i i s r e s p i r c m e t r y . T h i s method i s b a s e d o n t h e d e t e c t i o n o f c a r b o n d i o x i d e e v o l u t i o n o r o x y g e n c o n s u m p t i o n d u r i n g t h e d e c a y a c t i v i t y ( 9 , 9 8 , 103 , 1 1 5 , 1 1 7 ) . S m i t h (104) p r o v i d e d an u p - t o - d a t e r e v i e w o n t h i s m e t h o d . T h e a u t o m a t e d g a s - c h r o m a t o g r a p h i c t e c h n i g u e a p p e a r s t o be t h e b e s t f o r g a s d e t e c t i o n a s i t p r o v i d e s g r e a t e s t f l e x i b i l i t y i n l a b o r a t o r y u s e . H o w e v e r , i t i s i m p o s s i b l e t o r e p r o d u c e a l l c o n d i t i o n s i n t h e l a b o r a t o r y i m i t a t i n g t h e v a r i e t y o f s i t u a t i o n s t h a t o c c u r i n n a t u r e . T h e r e f o r e , l a b o r a t o r y t e s t s w i t h any w o o d - d e s t r o y i n g f u n g i c a n be o n l y r e g a r d e d a s t h e i n i t i a l p a r t o f a n y e v a l u a t i o n p r o g r a m o n t h e f u n g i c i d a l a c t i v i t y o f p r e s e r v a t i v e s . T h e y s h o u l d be f o l l o w e d by f i e l d a n d s e r v i c e t e s t s ( 2 1 ) . B . T e s t s o f C o m p o s i t i o n B o a r d s T h e e n t i r e f i e l d o f b i o d e g r a d a t i o n o f c o m p o s i t i o n b o a r d s a n d t h e i r p r e s e r v a t i o n i n s e r v i c e i n N o r t h A m e r i c a r e m a i n s r e l a t i v e l y u n e x p l o r e d c o n s i d e r i n g t h e a c h i e v e m e n t s made i n E u r o p e . C o n s e q u e n t l y , t h e r e i s no r e c o g n i z e d s t a n d a r d m e t h o d f o r t h e l a b o r a t o r y e v a l u a t i o n o f t h e d e c a y r e s i s t a n c e o f f i b e r b o a r d , t h o u g h s t a n d a r d m e t h o d s a c c e p t e d f o r t e s t i n g s o l i d wood a r e w i d e l y u s e d . 38 A c c o r d i n g t o J a c k s o n a n d S a v o r y ( 5 0 ) , FAO h a s recommended t h e u s e o f t h e s o i l - b l o c k t e s t f o r f i b e r b o a r d s i n g e n e r a l . F u r t h e r , t h e n e e d f o r m o u l d r e s i s t a n c e t e s t s w e r e s t r e s s e d . O p i n i o n s were a l s o o f f e r e d t h a t t h e s o i l - b l o c k m e t h o d may be t o o s e v e r e , a n d t h a t t e s t s r e f l e c t i n g more m o d e r a t e e x p o s u r e c o n d i t i o n s may be o f g r e a t e r v a l u e . H u b e r (48) u s e d t h e s o i l - b l o c k t e s t i n e v a l u a t i o n o f N a - P C P on h a r d b o a r d and p a r t i c l e b o a r d . T h e r e p o r t by M e r r i l l and F r e n c h (72) c o m p a r e d t h e s u i t a b i l i t y o f t e s t m e t h o d s a n d c o n c l u d e d t h a t t h e s o i l - b l o c k t e s t was most a p p l i c a b l e t o f i b e r b o a r d s b e c a u s e o f i t s a c c u r a c y a n d p r a c t i c a b i l i t y , B e h r (10) a p p l i e d t h e s t a n d a r d ASTM s o i l - b l o c k method t o t e s t t h e d e c a y r e s i s t a n c e o f m e d i u m — d e n s i t y f i b e r b o a r d s . S a v o r y (91) c o m p a r e d t h e a g a r - b l o c k a n d s o i l - b l o c k m e t h o d s i n h i s p l y w o o d t e s t a n d f o u n d t h a t i n h i b i t o r y e f f e c t s a r e much l e s s p r o n o u n c e d i n t h e s o i l — b l o c k s e r i e s p a r t l y b e c a u s e o f b e t t e r m o i s t u r e c o n t r o l i n t h e t e s t p i e c e s b u t a l s o p e r h a p s b e c a u s e o f a d s o r p t i o n o f v o l a t i l e g l u e c o m p o n e n t s b y t h e s o i l p a r t i c l e s . R e c o m m e n d a t i o n s were t h e r e f o r e made t h a t t h e s o i l - b l o c k m e t h o d c o u l d b e more s u i t a b l e t h a n t h e a g a r - b l o c k m e t h o d f o r t e s t i n g p l y w o o d a n d o t h e r b o a r d m a t e r i a l s b o n d e d w i t h some t y p e o f p h e n o l i c r e s i n . S t u d i e s h a v e a l s o b e e n made by m e a s u r i n g t h e d e c r e a s e i n s t r e n g t h t o e s t i m a t e t h e e x t e n t o f d e c a y . M e r r i l l a n d F r e n c h ( 7 3 , 77) a p p l i e d s u c h m e t h o d s i n t h e i r f i b e r b o a r d s t u d i e s a n d c o n c l u d e d t h a t n a i l h e a d p u l l - t h r o u g h r e s i s t a n c e and l a t e r a l n a i l r e s i s t a n c e c a n be u s e d s a t i s f a c t o r i l y f o r m e a s u r e m e n t s o f d i m i n u t i o n o f s t r e n g t h p r o p e r t i e s o f b o a r d s a s a r e s u l t o f 39 decay. Deppe and Gersonde (28) d e s c r i b e d the t e c h n o l o g i c a l advances i n production and t e s t i n g cf preserved wood-based panel products i n Germany. Cooperative t e s t s revealed t h a t the K o l l e f l a s k method{agar-block method) a c c o r d i n g t o DIN 52176, which i s g e n e r a l l y used f o r e v a l u a t i n g wood p r e s e r v a t i v e s , i s l e s s a p p r o p r i a t e f o r t e s t i n g p a r t i c l e b o a r d s , while the fungus c e l l a r t e s t developed a t the Bundesanstalt f u r M a t e r i a l p r u f u n g , B e r l i n , proved to be s u i t a b l e f o r t e s t i n g the r e s i s t a n c e of preserved p a r t i c l e b o a r d s t o decay f u n g i . Fungus c e l l a r t e s t s c r e a t e a s a t i s f a c t o r y a c c e l e r a t e d t e s t which sim u l a t e s a low or moderate decay environment where the t e s t sample s i z e i s an improvement on the s m a l l block concept of standard decay t e s t s and i s reported t o have some p r e d i c t i v e value (27). Deppe and Gersonde (28) a l s o agreed t h a t s u i t a b l e methods f o r t e s t i n g and e v a l u a t i n g the e f f e c t i v e n e s s of wood p r e s e r v a t i v e s f o r f i b e r b u i l d i n g boards had not progressed f a r enough. However, the comparative f u n g a l t e s t s of f i b e r b o a r d s by K o l l e f l a s k and the fungus c e l l a r methods showed t h a t , u n l i k e plywood and p a r t i c l e b o a r d , f i b e r b u i l d i n g boards may be t e s t e d by bcth methods as t o t h e i r p r e s e r v a t i v e e f f e c t s a g a i n s t wood-destroying Basidiomycetes. A f t e r a l l , wood e x t r a c t i v e s or r e s i n components a f f e c t f i b e r b o a r d s to a l e s s e r degree due to t h e i r very low amounts. Apparently, the s o i l - b l o c k method, i n comparison with a g a r - b l o c k ( o r K o l l e f l a s k ) method, would seem t o be no l e s s s u i t a b l e as i t can provide even higher c a p a c i t y of a b s o r p t i o n as d e s c r i b e d p r e v i o u s l y . 40 C . F a c t o r s To Be C o n s i d e r e d ( a ) . l e a c h i n g S m i t h (101) d o u b t e d t h a t t h e n o r m a l l y a c c e p t e d t e s t s f o r s o l i d wood p r o d u c t s w e r e n e c e s s a r i l y a p p l i c a b l e t o p a r t i c l e b o a r d , where t h e u n t r e a t e d b o a r d m i g h t b e t o x i c t o f u n g i b e c a u s e o f t h e a d h e s i v e s u s e d i n i t s m a n u f a c t u r e . D s i n g 2 4 - h o u r s o a k i n g i n w a t e r a t a m b i e n t t e m p e r a t u r e a s a p r e t r e a t m e n t on p a r t i c l e b o a r d b l o c k s , T o o l e a n d B a r n e s (116) f o u n d t h a t , w i t h t h e p h e n o l i c b o a r d s , s i g n i f i c a n t l y more w e i g h t l o s s o c c u r r e d i n b l o c k s w i t h s o a k i n g p r e t r e a t m e n t t h a n f o r t h o s e t h a t r e c e i v e d no t r e a t m e n t . T h e y c o n c l u d e d t h a t s o a k i n g p a r t i c l e b o a r d a t room t e m p e r a t u r e c a u s e d e x t r a c t i o n o f m a t e r i a l s w h i c h a c t a s b i o c i d e s , p r o b a b l y l o w — m o l e c u l a r - w e i g h t r e s i n f r a c t i o n s o f p h e n o l i c s , a n d h e n c e i n c r e a s e d b i o d e t e r i o r a t i o n . S a v o r y (91) r e p o r t e d t h a t , i n t h e a g a r - b l o c k t e s t s , t h e f u n g i f a i l e d t o o v e r g r o w a n d d i d n o t a p p r e c i a b l y a t t a c k t h e t e s t p i e c e s e x c e p t when t h e b l o c k s had b e e n p r e v i o u s l y s u b j e c t e d t o l e a c h i n g . I t a l s o a p p e a r e d t h a t , when u s i n g t h e s o i l — b l o c k m e t h o d , i n a l l c a s e s t h e v i g o u r o f a t t a c k was i n c r e a s e d a f t e r t h e l e a c h i n g t r e a t m e n t . Deppe a n d G e r s o n d e (27) a r g u e d a g a i n s t t h e s e v e r e l e a c h i n g t e s t o f p a r t i c l e b o a r d t e s t s a m p l e s on t h e b a s i s o f s e r v i c e s i t u a t i o n s s e t i n t h e German b u i l d i n g r e g u l a t i o n s . H o w e v e r , t h e y d i d p o i n t o u t a n d a g r e e d t h a t t h e r e a s o n s f o r i n h i b i t e d f u n g a l g r o w t h i n t h e K o l l e f l a s k s w e r e t h e l i b e r a t i o n o f f o r m a l d e h y d e f r o m t h e r e s i n , i t s a l k a l i c o n t e n t o r t h e p r e s e n c e o f u n b o u n d p h e n o l s . , H o w e v e r , H e d l e y (43) s a i d t h a t l i t t l e d i f f e r e n c e i n e x t e n t 41 o f d e c a y was o b t a i n e d u s i n g l e a c h e d a n d n o n - l e a c h e d s a m p l e s i n h i s own p r e l i m i n a r y i n v e s t i g a t i o n , ( b ) . I n i t i a l m o i s t u r e c o n t e n t T h e most f a v o r a b l e c o n d i t i o n f o r t h e g r o w t h o f f u n g i i n wood seems t o b e when t h e c e l l w a l l s i n a d d i t i o n t o b e i n g f u l l y i m b i b e d a r e c o a t e d w i t h a f i l m o f l i g u i d w a t e r i n w h i c h f r e e d i f f u s i o n o f t h e e n z y m e s a n d o f t h e p r o d u c t s o f t h e i r a c t i o n c a n t a k e p l a c e . In a d d i t i o n some a i r s p a c e s must a l s o r e m a i n i n t h e c a v i t i e s s o t h a t d i f f u s i o n o f g a s e s c a n t a k e p l a c e ( 1 9 ) . T h u s , d e c a y o f wood g e n e r a l l y i s i n h i b i t € d when i t s m o i s t u r e c o n t e n t i s b e l o w i t s f i b e r s a t u r a t i o n p o i n t o r when t h e M . C . i s s o h i g h t h a t l a c k o f o x y g e n p r o b a b l y p r e v e n t s r e s p i r a t i o n b y w o o d — d e s t r o y i n g f u n g i ( 8 3 ) , I t i s i m p o s s i b l e t o e s t a b l i s h a n y e x a c t o p t i m u m m o i s t u r e c o n t e n t f o r any s p e c i e s o f f u n g u s e x c e p t i n r e l a t i o n t o t i m b e r s o f s i m i l a r d e n s i t y a n d s t r u c t u r e . P o r p r a c t i c a l p u r p o s e s , i t c a n be t a k e n t h a t t h e minimum m o i s t u r e i n wood f o r t h e g r o w t h o f most w o o d - d e s t r o y i n g f u n g i i s somewhere i n t h e r e g i o n o f 22 t o 24 p e r c e n t ( 1 9 ) . i n f o r m a t i o n f r o m t h e P r i n c e s R i s b o r o u g h L a b o r a t o r y (17) i n d i c a t e d t h a t 2 6 , 5 p e r c e n t i s t h e d e c a y t h r e s h o l d m o i s t u r e c o n t e n t f o r S c o t s p i n e s a p w o o d w h i l e 1 8 . 0 p e r c e n t i s f o r s t a n d a r d a n d t e m p e r e d h a r d b o a r d . B o t h v a l u e s were h i g h e r t h a n t h e e q u i l i b r i u m m o i s t u r e c o n t e n t r e a c h e d u n d e r 100 p e r c e n t r e l a t i v e h u m i d i t y a t 22 C f o r t h e r e s p e c t i v e m a t e r i a l s , a p p a r e n t l y , a d d i t i o n a l w e t t i n g i s n e e d e d t o p r o m o t e d e c a y u n d e r s u c h t e s t e n v i r o n m e n t s . 42 Deppe a n d S e r s o n d e (28) a l s o r e p o r t e d t h a t a t a m o i s t u r e c o n t e n t o f g r e a t e r t h a n 18 p e r c e n t , w o o d - b a s e d m a t e r i a l s became s u s c e p t i b l e t o d e c a y . H o w e v e r , t h e r e s p o n s e o f d i f f e r e n t m a t e r i a l s t o f u n g a l a t t a c k c o u l d be d i f f e r e n t a n d more i n v e s t i g a t i o n i s n e e d e d t o c l a r i f y t h e n a t u r e o f t h e s u s c e p t i b i l i t y . H e d l e y a n d F o s t e r (42) c l a i m e d t h a t t h e i&STM s t a n d a r d s o i l — b l o c k m e t h o d i s n o t t h e most s u i t a b l e f o r o b t a i n i n g o p t i m u m w e i g h t l o s s e s i n t e s t b l o c k s , p a r t i c u l a r l y when a w h i t e — r o t f u n g u s i s u s e d a s t h e d e c a y o r g a n i s m . T h e y p r o p o s e d t h e " d o u b l e b l o c k " t e c h n i g u e i n w h i c h two b l o c k s w e r e s t a c k e d , w i t h t h e l o w e r one b u r i e d f l u s h w i t h t h e s o i l s u r f a c e . W i t h a l l w h i t e - r o t £ ungdj,ff lower:- blocks'^of.' either"'spee?ies, , Rinu s,,: r ad ia tea D. DonCand, P o p u l u s r o b u s t a , a t t a i n e d a M . C . s u i t a b l e f o r d e c a y more r a p i d l y , and l o s t more w e i g h t , t h a n d i d t h e u p p e r b l o c k s . W i t h b r o w n — r o t f u n g i , w h i c h a r e p r o b a b l y more e f f e c t i v e w a t e r c o n d u c t o r s t h a n w h i t e ^ r o t f u n g i , t h i s same r e l a t i o n s h i p d e v e l o p e d o n l y w i t h P o p u l u s b l o c k s . D e G r o o t (26) t e s t e d d e c a y f u n g u s , l i g h t and m o i s t u r e i n t e r a c t i o n s u s i n g 5 s t a c k e d s o u t h e r n p i n e s a p w o o d b l o c k s o n f e e d e r s t r i p s a n d f o u r f u n g i . He f o u n d t h a t , w i t h e a c h f u n g u s , t h e g r e a t e s t l o s s was i n t h e two l o w e s t b l o c k s , i . e . , t h o s e c l o e s t t o t h e f e e d e r s t r i p , a n d s o was t h e m o i s t u r e c o n t e n t o f d e c a y e d b l o c k s . I t a l s o a p p e a r e d t h a t t h e t w o b r o w n - r o t L e n z i t e s s p e c i e s were a b l e t o t r a n s p o r t m o i s t u r e f r o m t h e s o i l t h r o u g h s e v e r a l t i e r s o f t e s t b l o c k s . I n c o n t r a s t , t h e two w h i t e - r o t f u n g i were v i r t u a l l y d e p e n d e n t u p o n t h e i n t r i n s i c w a t e r c o n t e n t o f t h e w o o d . 43 Peterson and Cowling (83) t e s t e d the i n f l u e n c e of v a r i o u s i n i t i a l moisture contents on decay and reported t h a t , during the f i r s t f o u r weeks of i n c u b a t i o n , t e s t wafers with i n i t i a l moisture of 6 - 4 5 percent a c t u a l l y i n c r e a s e d i n moisture content t o w e l l above the f i b e r s a t u r a t i o n p o i n t r e g a r d l e s s whether or not the t e s t fungus was present. T e s t s i n the f o l l o w i n g f o u r t h to e i g h t h weeks of i n c u b a t i o n a l s o i n d i c a t e d t h at the mycelium of Polyporus v e r s i c o l o r L. ex Fr. caused movement of an a d d i t i o n a l amount of water i n t o the t e s t wafers even though i t caused no decay i n them.,He concluded t h a t i n i t i a l moisture content had no e f f e c t on r a t e of decay. Assuming the l a c k of moisture i n the denser boards as a p o s s i b l e cause f o r low decay weight l o s s e s , Behr (12) c a r r i e d out experiments to add water to t e s t p i e c e s before p l a c i n g them on the fungus c u l t u r e s . I t i s thought t h a t any f u n g i c i d a l compound should not be a p p r e c i a b l y removed by t h i s treatment, n e v e r t h e l e s s decay weight l o s s was i n c r e a s e d as much as twelve times over the unwetted blocks. (c). S t e r i l i z a t i o n methods Test blocks need t o be completely s t e r i l i z e d b e f o r e being incubated with a s i n g l e fungus c u l t u r e to make sure no contamination w i l l i n t e r f e r e with the t e s t r e s u l t s . The two commonly used methods f o r s t e r i l i z i n g wood ar e : (i) wet-heat(121 C), and ( i i ) treatment with gaseous chemicals l i k e e t h y l e n e oxide or propylene oxide. However, heating wood under humid c o n d i t i o n d r i v e s o f f e x t r a c t i v e s already present as w e l l as 44 p r e s e r v a t i v e s t h a t may h a v e b e e n d e l i b e r a t e l y i n t r o d u c e d i n t o t h e wood f o r p u r p o s e o f t o x i c i t y t e s t s t u d i e s ( 1 0 0 ) . I n some c a s e s t h e a p p l i e d s t e a m i n g m i g h t c a u s e c h e m i c a l m o d i f i c a t i o n , l i k e h y d r o l y s i s i n wood c o m p o n e n t s , u n d e r s u i t a b l e a c i d i c c o n d i t i o n s . P r o p y l e n e a n d e t h y l e n e o x i d e s a r e w i d e l y u s e d a s c o l d g a s e o u s s t e r i l i z i n g a g e n t s , t h e i r g e n e r a l u s e b e i n g s u m m a r i z e d by S m i t h ( 9 6 ) . I n a l a t e r r e p o r t (97) S m i t h s t u d i e d t h e e f f e c t o f m o i s t u r e c o n t e n t o n t h e s t e r i l i z a t i o n o f wood u s i n g t h e s e two g a s e s , a n d f o u n d t h a t wood b l o c k s w i t h a m o i s t u r e c o n t e n t b e l o w 10 p e r c e n t were d i f f i c u l t t o s t e r i l i z e . B a s i d i o m y c e t e s were f o u n d t o be l e s s r e s i s t a n t t o p r o p y l e n e o x i d e g a s t h a n were t h e A s c o m y c e t e s . P r o p y l e n e o x i d e c a n a l s o r e a c t w i t h some wood p r e s e r v a t i v e , e . g , , c r e o s o t e , t o f o r m a more t o x i c c o m p o u n d . A l k y l e n e o x i d e s h a v e b e e n u s e d i n c h e m i c a l m o d i f i c a t i o n o f wood t o i m p r o v e r e s i s t a n c e t o r o t and d i m e n s i o n a l s t a b i l i t y ( 8 5 ) . I t i s b a s e d on t h e t h e o r y t h a t e n z y m e s must d i r e c t l y c o n t a c t t h e s u b s t r a t e (wood c e l l u l o s e o r l i g n i n ) a n d t h e s u b s t r a t e must h a v e a s p e c i f i c c o n f i g u r a t i o n . I f t h e s u b s t r a t e i s c h e m i c a l l y c h a n g e d , t h i s h i g h l y s e l e c t i v e r e a c t i o n c a n n o t t a k e p l a c e . C h e m i c a l m o d i f i c a t i o n c a n a l s o c h a n g e t h e h y d r o p h i l i c n a t u r e o f w o o d . T h e a d v a n t a g e s o f u s i n g a l k y l e n e o x i d e s f o r t h e c h e m i c a l m o d i f i c a t i o n o f wood a r e t h e v o l a t i l e n a t u r e w h i c h a l l o w s g o o d p e n e t r a t i o n a n d e a s e o f r e m o v a l a f t e r r e a c t i o n due t o t h e low b e l l i n g p o i n t s . T h e y c a n r e a c t g u i c k l y w i t h t h e h y d r o x y l g r o u p s o f wood c o m p o n e n t s a t l o w t e m p e r a t u r e s . T h e u s e o f e t h y l e n e o x i d e g i v e s a p o l y e t h y l e n e o x i d e p o l y m e r i n t h e wood c e l l w a l l . H o w e v e r , p o l y e t h y l e n e o x i d e p o l y m e r s h a v e 45 t h e d i s a d v a n t a g e o f b e i n g l a r g e l y w a t e r s o l u b l e , e s p e c i a l l y i f t h e m o l e c u l a r w e i g h t i s l o w . T h e same r e p o r t (85) s u m m a r i z e s t h a t , a t l e v e l s o f 23 t o 30 p e r c e n t w e i g h t g a i n s , t h e wood d o e s n o t d e c a y . I n d e c a y t e s t t h e i m p r e g n a t i o n o f t e s t wood b l o c k s w i t h g a s e o u s c h e m i c a l s n e c e s s i t a t e s v e n t i l a t i o n o f t h e b l o c k s a f t e r t r e a t m e n t , t o r e m o v e f r e e r e s i d u e s t h a t may s t i l l r e m a i n i n s u f f i c i e n t q u a n t i t y t o r e t a r d t h e s u b s e q u e n t g r o w t h o f d e c a y i n g f u n g i i n o c u l a t e d o n t o t h e wood. E t h y l e n e o x i d e i s r e a d i l y r e m o v e d f r o m wood b y v e n t i l a t i o n , b u t i t i s s t i l l n o t known i f t h i s p r o c e s s l e a v e s r e s i d u e s t h a t c o u l d r e t a r d g r o w t h o f c e r t a i n f u n g i . S m i t h a n d S h a r m a n (100) i n v e s t i g a t e d t h e e f f e c t o f t h r e e k i n d s o f s t e r i l i z a t i o n o f wood on s u b s e q u e n t d e c a y a n d c o m p a r e d t h e wet—heat method w i t h t r e a t m e n t w i t h e t h y l e n e o x i d e u n d e r v a c u u m . T h e y f o u n d no s i g n i f i c a n t d i f f e r e n c e b e t w e e n t h e p e r c e n t a g e - w e i g h t - l o s s v a l u e s f o r t h e two m e t h o d s a n d c o n c l u d e d t h a t e t h y l e n e o x i d e s t e r i l i z a t i o n o f wood was e f f i c i e n t a n d d i d n o t r e s u l t i n t h e r e t e n t i o n o f a n y t o x i c r e s i d u e s b y t h e w o o d . 46 CHAPTER I I I . M A T E R I A L S AND METHODS 1. M a t e r i a l s A* A s p l u n d P u l p T h e c o m m e r c i a l A s p l u n d p u l p , u s e d t h r o u g h o u t t h i s s t u d y , was n o r m a l l y c o l l e c t e d a t o n e o f t h e c o n s i s t e n c y r e g u l a t o r s , b e f o r e r e s i n a n d wax e m u l s i o n a d d i t i o n s , i n t h e CANFOR h a r d b o a r d m i l l a t New W e s t m i n s t e r , B . C . . . I t c o n s i s t e d of a mixture_of western s o f t w o o d , i n c l u d i n g D o u g l a s f i r [ P s e u d o t s u g a m e n z i e s i i ( M i r f a . ) F r a n c o ] , s p r u c e { P i c e a s p p . ) , B a l s a m [ A b i e s b a l s a m e a ( L . ) M i l l , J , w e s t e r n r e d c e d a r ( T h u j a p l i c a t a Donn) a n d h e m l o c k ( Tsu<ja s p p . ) . T h e p u l p t h u s o b t a i n e d was u n d r a i n e d a n d h a d a c o n s i s t e n c y , a t w h i c h b r o i t i n a t i o n was t o be c a r r i e d o u t , t h a t a c t u a l l y i s u s e d i n t h e h a r d b o a r d m i l l , i . e . , 2%. B . P u l p B r o m i n a t i o n F o r e a c h e x p e r i m e n t an amount o f p u l p c o r r e s p o n d i n g t o 700 grams o f o v e n - d r y m a t e r i a l was u s e d . T h e p u l p s l u r r y t e m p e r a t u r e was a d j u s t e d t o 40 C by p u r g i n g t h e s l u r r y w i t h l i v e s t e a m i n a b u c k e t . T h e a p p r o p r i a t e amount o f p u l p s l u r r y was t r a n s f e r r e d t o a c o r r o s i o n r e s i s t a n t v e s s e l a n d s o d i u m b r o m i d e was a d d e d , c a l c u l a t e d t o p r o v i d e 10% b r o m i n e , b a s e d o n t h e o v e n - d r y w e i g h t o f t h e p u l p . The s t a r t i n g pH o f t h e s o l u t i o n was 5.6, L i b e r a t i o n o f t h e b r o m i n e o c c u r r e d o n a d d i t i o n ( b u b b l i n g ) o f c h l o r i n e g a s t h r o u g h t h e s l u r r y i n t h e amount o f 12 t o 15% ( c a l c u l a t e d o n t h e 47 b a s i s of oven-dry pulp weight). During a l l phases o f chemical a d d i t i o n s the s l u r r y was s t i r r e d v i g o r o u s l y with a " l i g h t e n i n g " s t i r r e r . S t i r r i n g continued up to 60 seconds f o l l o w i n g completion of the gas a d d i t i o n , whereupon a measured g u a n t i t y of calcium hydroxide <Ca (0H)2 ) was added t o n e u t r a l i z e the a c i d i c by-products and to r a i s e the s l u r r y pH from 1.4 to 5.5. F i n a l pH s t a b i l i z a t i o n was obtained by readjustment of the s l i g h t l y d ecreasing pH (with time) with f u r t h e r a d d i t i o n of Ca (0H)2 . G. Boards The n e u t r a l i z e d s l u r r y was poured i n t o a 16 i n . sguare forming box which c o n t a i n e d enough water t o r e a d j u s t the s l u r r y c o n s i s t e n c y to 1%. To i m i t a t e the commercial f o r m u l a t i o n , 7.0 g c a t i o n i c wax emulsion (Mobilcer 46) was added with s t i r r i n g at 40 C. I f the fo r m u l a t i o n c a l l e d f o r p h e n o l i c or other r e s i n , i t was added at t h i s stage and s t i r r i n g was continued f o r a t o t a l of two minutes. Where necessary pH adjustment to 4.5 was e f f e c t e d by adding s m a l l amounts of s u l p h u r i c a c i d . F i n a l l y , the s l u r r y was g r a v i t y d r a i n e d , f o l l o w e d by s u c t i o n to remove as much water from r e s u l t i n g mat as p o s s s i b l e . / The wet-lap was f i r s t c o l d - p r e s s e d at 170 p s i to remove the excess water. A l l wet-^laps made of brominated f i b e r were sprayed with 240 cc of hot s o l u t i o n of borax (77.3 g/1) and b o r i c a c i d (89.4 g/1) t o prevent s u r f a c e c h a r r i n g during h o t - p r e s s i n g . The wet-laps of the c o n t r o l board thus procured were then hot-pressed ay 175 C p l a t e temperarture i n three stages: 70 sec a t 700 p s i , 110 sec at 40 p s i ( b r e a t h i n g ) , and 7 min a t 350 p s i . 48 The brominated boards were pressed at the same schedule with s l i g h t l y reduced s p e c i f i c pressures (60 0 p s i i n i t i a l and 27 5 p s i f i n a l h o l d ) , and reduced temperature (135 C) t o e l i m i n a t e the occurrence of c h a r r i n g . A l l boards were h u m i d i f i e d at 50 ± 3% r e l a t i v e humidity and 23 ± 2 C u n t i l e q u i l i b r i u m moisture content of the board was reached. 2. Methods Since there i s no r e c o g n i z e d standard method f o r the l a b o r a t o r y e v a l u a t i o n of the decay r e s i s t a n c e of f i b e r b o a r d s , i t was decided to f o l l o w a d v i c e given by some previous workers (50, 72) and t o use a modified s o i l - b l o c k technique ( 2 ) . F o r example, a l l manipulations needinq s t e r i l e c o n d i t i o n s were done i n a h o r i z o n t a l - f l o w , s t e r i l e - a i r bench. Also, the new mite-proof s o i l - j a r l i d s , recommended by Smith (106), were used t o ensure freedom from contamination d u r i n g the i n c u b a t i o n p e r i o d of 10 weeks. For a l l t e s t b l o c k s , f o l l o w i n g i n c u b a t i o n the mycelium adhering to the blocks was c a r e f u l l y scraped away b e f o r e f i n a l weights were measured. Oven-dry weights (105 ± 2 C o v e r n i g h t ) were used throughout t h i s study and these, together with the wet weights measured f o l l o w i n g i n c u b a t i o n , were used t o c a l c u l a t e percentage dry-weight l o s s and f i n a l moisture content values f o r a l l the t e s t blocks. Because of recognized u n c e r t a i n t i e s i n the t e s t t e c h n i q u e . 49 t h e f o l l o w i n g s p e c i f i c v a r i a b l e s were e v a l u a t e d ; i . C o l d - w a t e r l e a c h i n g {AWPA M11-77) o f t h e h a r d b o a r d b l o c k s b e f o r e d e c a y ; i i . C o n d i t i o n i n g o f t h e h a r d b o a r d b l o c k s t o t w o d i f f e r e n t m o i s t u r e c o n t e n t s b e f o r e e x p o s u r e t o w o o d - d e s t r o y i n g f u n g i ; a n d i i i . E t h y l e n e o x i d e a n d w e t - h e a t as a l t e r n a t i v e s t e r i l i z a t i o n m e t h o d s . A . C o m p o s i t i o n a n d S i z e o f t h e H a r d b o a r d T e s t B l o c k s 1 . F i b e r o n l y — f i b e r f o r a l l s i x t y p e s o f h a r d b o a r d was m i l l - r u n A s p l u n d p u l p { C a n a d i a n F o r e s t P r o d u c t s l t d . ) c o n s i s t i n g o f a m i x t u r e o f w e s t e r n s o f t w o o d s : 75% D o u g l a s f i r f P s e u d o t s u g a m e n z i e s i i ( M i r b . ) F r a n c o ] , 10% s p r u c e ( P i c e a s p p . ) , 15% B a l s a m p A b i e s b a l s a a e a ( L . ) H i l l , 1, w e s t e r n r e d c e d a r ( T h u j a p l i c a t a Donn) a n d h e m l o c k ( T s u g a s p p , ) . 2 . F i b e r p l u s 1% p h e n o l i c r e s i n f B B - 1 4 0 F o r a s i d e ( R e i c h h o l d C h e m i c a l s L t d . ) ] and 0.30% c a t i o n i c wax, p r e c i p i t a t e d w i t h a l u m (0.15%) a n d a d j u s t e d t o pH 4 , 7 w i t h s u l p h u r i c a c i d ; 3 . F i b e r p l u s p o l y e t h y l e n i m i n e r e s i n f P E I 600 (Dow C h e m i c a l C o . ) ] a n d 0.30% w a x ; 4 . B r c m i n a t e d f i b e r o n l y — f i b e r s were b r o m i n a t e d f o l l o w i n g t h e m e t h o d o f J u r a z s a n d P a s z n e r (57) u s i n g 10% b r o m i n e , b a s e d o n o v e n - d r y f i b e r w e i g h t ; 50 5 . B r o m i n a t e d f i b e r p l u s 1 $ p h e n o l i c r e s i n a n d 0.30% wax p r e c i p i t a t e d w i t h a l u m (0.J51&) a n d a d j u s t e d t o pH 5 . 0 -5 . 5 u s i n g s u l p h u r i c a c i d ; 6 . B r o m i n a t e d f i b e r p l u s If p o l y e t h y l e n i m i n e r e s i n a n d 0.30SS wax. T o a v o i d t h e e f f e c t s o f n a t u r a l s u r f a c e f i n i s h o f t h e h a r d b o a r d o n t h e r a t e o f f u n g a l a t t a c k , b o t h f a c e s o f t h e h a r d b o a r d were s a n d e d , p r o v i d i n g a f i n a l t h i c k n e s s o f a b o u t 3 mm. B l o c k s 20 mm s q u a r e were c u t a n d f i n e l y s a n d e d t o remove a n y l o o s e f i b e r s . A r e p l i c a t i o n o f f o u r b l o c k s was u s e d f o r e a c h t r e a t m e n t c o m b i n a t i o n . B . H o o d - D e s t r o y i n g F u n g i O s e d : C o n i c £ h o r a j j u t e a n a (Schura. ex F r . ) K a r s t . = WFPL n o . 9H L e n z i t e s t r a b e a P e r s . ex F r . = WFPL n o , 47D P o r i a i n c r a s a t a { B e r k . & C u r t . ) B u r t = WFPL n o . 118D J t o r i a j o n t i c o l a M u r r . = WFPL n o . 120C P o l y p o r u s a d u s t u s W i l l d . ex F r . = WFPL n o . 75C P o l y p g r u s v e r s i c o l o r L . ex F r . = WFPL n o . 105E The f i r s t f o u r f u n g i a r e b r o w n - r o t a n d t h e l a s t two w h i t e -r o t f u n g i ( 5 1 ) . C . P r e p a r a t i o n o f S o i l J a r s 1 6 - o z r o u n d j a r s w e r e f i l l e d w i t h p a c k e d s o i l o f 45-505? m o i s t u r e c o n t e n t t o more t h a n h a l f o f t h e i r c a p a c i t y . T h e s o i l 51 medium was f r e s h g a r d e n c c m p o s t s o i l w i t h 20-40% c o n t e n t o f o r g a n i c m a t t e r a n d was s i f t e d t h r o u g h a 5 mm g a u g e s i e v e , a f e e d e r s t r i p of p o n d e r o s a p i n e s a p w o o d was p r e s s e d on t h e s o i l a n d t h e t o t a l a s s a y was s t e r i l i z e d i n a n a u t o c l a v e f o r one h o u r a t 121 C . A f t e r c o o l i n g t h e s o i l j a r s were i n o c u l a t e d w i t h t h e d e s i r e d f u n g i w h i c h were c u l t u r e d f o r a b o u t s i x d a y s o n -the a g a r p l a t e s , a n d s t e r i l e m i t e - p r o o f l i d s e x c h a n g e d f o r t h o s e u s e d d u r i n g t h e i n i t i a l a u t o c l a v i n g . T h i s work was c a r r i e d o u t o n a l a m i n a r f l o w s t e r i l e a i r b e n c h . T h e i n o c u l a t e d s o i l j a r s were t h e n i n c u b a t e d i n a room w i t h t e m p e r a t u r e s u i t a b l y s e t a t 25 C and a r e l a t i v e h u m i d i t y o f 75 ± 5% f o r two weeks b e f o r e t h e t e s t b l o c k s were p l a n t e d o n t h e f e e d e r s t r i p s , M i t e - p r o o f s o i l - j a r l i d s were u s e d t o e n s u r e f r e e d o m f r o m c o n t a m i n a t i o n d u r i n g t h e i n c u b a t i o n . D . , P r e p a r a t i o n o f T e s t S a m p l e s D i f f e r e n t p r o c e d u r e s i n p r e p a r i n g t h e t e s t s a m p l e s p r i o r t o d e c a y were m e t i c u l o u s l y f o l l o w e d t o a l l o w d i s t i n c t i o n among t h e e f f e c t s o f d i f f e r e n t f a c t o r s i n v o l v e d i n t h i s t e s t . T h e d e t a i l e d m a n i p u l a t i o n s o f p r o c e d u r e s a r e shown i n F i g . 2, (a) . L e a c h i n g C o l d - w a t e r l e a c h i n g o f t h e h a r d b o a r d b l o c k s f o r 14 d a y s was done s i m i l a r l y t o t h e m e t h o d s u g g e s t e d i n ASPA M 1 1 - 7 7 ( 4 ) . F o l l o w i n g l e a c h i n g , t h e b l o c k s were o v e n d r i e d t o o b t a i n t h e i r i n i t i a l d r y w e i g h t s , T h e n a l l b l o c k s , i n c l u d i n g a r e p l i c a t e s a m p l e o f n o n - l e a c h e d b l o c k s , were vacuum i m p r e g n a t e d w i t h w a t e r 52 u s i n g a d e s i c c a t o r and a one-hour vacuum p e r i o d . The b l o c k s were l e f t i n the water overnight and then allowed to a i r dry under s t e r i l e - a i r v e n t i l a t i o n u n t i l the moisture content of the b l o c k s reached an average value cf 20%. E x t r a blocks were used t o check the d e s i r e d moisture-content l e v e l . The b l ocks were then steam s t e r i l i z e d at 15 p s i (121 C) f o r 30 min., c o o l e d on a l a m i n a r - f l o w , s t e r i l e - a i r bench and p l a n t e d i n t o s o i l j a r s (ASTH B1413-76). (b). S e t t i n g of i n i t i a l moisture content and method o f s t e r i l i z a t i o n F ollowing l e a c h i n g and pre-wetting to 20% M.C., as p r e v i o u s l y d e s c r i b e d , b l o c k s were s t e r i l i z e d and then some had t h e i r moisture content adjusted under v e n t i l a t i o n i n s t e r i l e a i r to 8%. T h i s allowed me to examine the e f f e c t of two i n i t i a l moisture contents (20% and 8%) on the decay r a t e s o f leached, ncn-brcminated and brominated boards. Two s t e r i l i z a t i o n methods were used , e i t h e r wet heat (121 C) , or ethylene oxide under vacuum (100). There was a s u b s t a n t i a l number of r e f e r e n c e b l o c k s a l l o c a t e d f o r each combination of f a c t o r s . These e x t r a b l o c k s were used to check changes i n moisture content d u r i n g a i r - d r y i n g to a s c e r t a i n exact c o n t r o l . They a l s o served as a check t o produce c o r r e c t i o n f a c t o r s f o r changes i n sample weights r e s u l t i n g from soaking and steam s t e r i l i z a t i o n . Some check b l o c k s were a l s o p l a n t e d i n s o i l j a r s f r e e of any b i o l o g i c a l agent to check i f any a d d i t i o n a l l o s s e s were i n v o l v e d . The c o r r e c t i o n f a c t o r s were c a l c u l a t e d as averages of weight changes 53 a n d i n v o l v e d f o u r r e p l i c a t e s . E . E v a l u a t i o n o f R e s u l t s W e i g h t l o s s i n d r y mass due t o f u n g a l a c t i v i t y was t a k e n a s t h e o r i g i n a l d r y m a s s , a f t e r b e i n g c o r r e c t e d f o r w e i g h t c h a n g e s b e f o r e p l a n t i n g , m i n u s t h e f i n a l d r y mass w h i c h was a l s o b e i n g c o r r e c t e d f o r c h a n g e s i n w e i g h t d u e t o l e a c h i n g i n s i d e t h e s o i l j a r . The w e i g h t l o s s p e r c e n t a g e was c a l c u l a t e d a s a p e r c e n t i l e o f t h e a b o v e c o r r e c t e d l o s s o f mass o f t h e c o r r e c t e d o r i g i n a l d r y m a s s . 54 CHAPTER 1 7 . R E S U L T S AND D I S C U S S I O N To e s t a b l i s h w e i g h t l o s s e s a t g r o u n d l e v e l and b l a n k t e s t c o n d i t i o n s f o r t e s t b l o c k s d u r i n g i n i t i a l l e a c h i n g a n d i n c o n t r o l c o n d i t i o n s , i . e . , i n t h e a b s e n c e o f d e c a y i n g f u n g i i n s o i l j a r s , c o r r e c t i o n f a c t o r s a r e c a l c u l a t e d a n d t h e r e s u l t s a r e g i v e n i n T a b l e 1. P e r c e n t w e i g h t l o s s e s due t o d e c a y f o r d i f f e r e n t t e s t c o m b i n a t i o n s a r e t a b u l a t e d i n T a b l e s 2 , 3 , a n d 4 . T a b l e 2 e n u m e r a t e s t h e e f f e c t o f l e a c h i n g . I n T a b l e 3 t h e e f f e c t o f i n i t i a l m o i s t u r e c o n t e n t , a n d i n T a b l e 4 t h e e f f e c t o f s t e r i l i z a t i o n m e t h o d s a r e g i v e n . , , T h e b a s i c a n a l y t i c a l t o o l e m p l o y e d was t h e a n a l y s i s o f v a r i a n c e . A s c a n n i n g o f t h e d a t a r e v e a l s m a j o r d i f f e r e n c e s b e t w e e n t h e w e i g h t l o s s r e s p o n s e o f t h e b o a r d s t o a t t a c k by t h e d i f f e r e n t f u n g i , w i t h w e i g h t l o s s e s r a n g i n g f r o m 5651 u n d e r £s. m o n t i c o l a a n d P , i ? l n c r a s s a t a t o n e a r z e r o f o r P . a d u s t u s . I t i s a l s o c l e a r t h a t t h e w e i g h t l o s s r e s p o n s e o f t h e b r o m i n a t e d m a t e r i a l d i f f e r s f r o m t h a t o f t h e n o n - b r o m i n a t e d n o t o n l y i n t h e g e n e r a l l e v e l o f t h e e x t e n t o f d e c a y b u t a l s o , a p p a r e n t l y , i n t h e i r r e s p e c t i v e t r e a t m e n t - r e s p o n s e p a t t e r n s , i . e . , r e s p o n s e s u n d e r d i f f e r e n t t r e a t m e n t c o n d i t i o n s r e l a t i v e t o d i f f e r e n c e s i n b o a r d m a k e u p . , C o n s e g u e n t l y , t h e a n a l y s e s w e r e c a r r i e d o u t s e p a r a t e l y f o r t h e b r o m i n a t e d a n d n o n - b r o m i n a t e d m a t e r i a l f o r e a c h f u n g u s . T h e e f f e c t s o f b o a r d c o m p o s i t i o n ( C ) ; l e a c h i n g • p r i o r t o p l a n t i n g ( I ) , i n i t i a l m o i s t u r e c o n t e n t o f t h e t e s t b l o c k s (M), 55 a n d s t e r i l i z a t i o n m e t h o d ( S ) , p r e s e n t e d i n a b a r d i a g r a m i n F i g u r e 3 , were a l s o t e s t e d f o r i n t e r a c t i o n s i n a n a n a l y s i s o f v a r i a n c e , R e s u l t s a r e g i v e n i n T a b l e s 5 a n d 6 f o r n o n - b r o m i n a t e d and b r o m i n a t e d g r o u p s , r e s p e c t i v e l y . V i s u a l p r e s e n t a t i o n s o f t h e f u n g a l g r o w t h a r e p r e s e n t e d i n F i g s . 4 t h r o u g h 1 4 , 1, C o m p o s i t i o n o f t h e H a r d b o a r d D e s p i t e t h e i n t e r a c t i o n o b s e r v a b l e b e t w e e n h a r d b o a r d c o m p o s i t i o n a n d m o i s t u r e c o n t e n t a n d l e a c h i n g ( T a b l e 5 ) , w i t h f o u r o f t h e f u n g i t h e n o n - b r o m i n a t e d b o a r d c o n t a i n i n g p o l y e t h y l e n i m i n e r e s i n was d e c a y e d s i g n i f i c a n t l y more t h a n e i t h e r t h e n o n - b r o m i n a t e d b o a r d s w i t h p h e n o l i c r e s i n o r w i t h o u t any r e s i n ( T a b l e s 2 , 5 ) . T h i s was o b s e r v e d w h e t h e r o r n o t t h e b o a r d was l e a c h e d b e f o r e d e c a y by t h e f u n g i ( T a b l e 2 ) . The w h i t e - r o t f u n g u s P a , - v e r s i c o l o r was a c l e a r e x c e p t i o n , s i n c e i n t h i s c a s e t h e n o n - b r o m i n a t e d p o l y e t h y l e n i m i n e - t r e a t e d b o a r d s s h o w e d g r e a t e s t r e s i s t a n c e t o d e c a y . S t o l l e y ( 1 0 9 ) , u s i n g p a r t i c l e b o a r d g l u e d e i t h e r w i t h a p h e n o l i c c r a u r e a r e s i n , o b s e r v e d a s i m i l a r a n o m a l o u s s i t u a t i o n , where w e i g h t l o s s c a u s e d D Y C c n i o B h o r a c e r e b e l l a P e r s . was l a r g e s t f o r t h e u r e a - g l u e d b o a r d , b u t w i t h P A v a j o o r a r i a t h e p h e n o l i c - g l u e d b o a r d r e s u l t e d i n t h e l a r g e s t w e i g h t l o s s . The p r o m o t i n g e f f e c t o f p o l y e t h y l e n i m i n e on t h e r a t e o f d e c a y o f n o n - b r o m i n a t e d b o a r d s by f o u r o f t h e f u n g i c o u l d r e s u l t f r o m t h e n i t r o g e n i n t h e a d h e s i v e (32%) . A s i m i l a r c o n c l u s i o n 56 w o u l d e x p l a i n t h e a p p a r a n t a c c e l e r a t i n g e f f e c t s o b s e r v e d f o r u r e a - f o r o a l d e h y d e r e s i n on t h e d e c a y o f p a r t i c l e b o a r d by s e v e r a l w o o d - d e s t r o y i n g f u n g i (109 , 1 2 0 ) . T h e r e s i d u a l n i t r o g e n l e v e l s i n wood a r e n o r m a l l y low ( e x c l u d i n g t h e sapwood) a n d b e c a u s e o f t h e h i g h l e a c h i n g e f f e c t r e s u l t i n g f r o m t h e ftsplund p u l p p r o d u c t i o n m e t h o d , n i t r o g e n l e v e l s i n t h e s e e x p e r i m e n t a l b o a r d s w o u l d be e x t r e m e l y l o w . C o n s e q u e n t l y , a n y n i t r o g e n a d d e d a s p a r t o f t h e c h e m i c a l e n t i t y o f a n a d h e s i v e w o u l d h a v e a v e r y s i g n i f i c a n t e f f e c t on t h e o v e r a l l n i t r o g e n l e v e l s i n t h e b o a r d s , p r o v i d i n g t h e p o t e n t i a l f o r a c c e l e r a t e d d e c a y . T h e r e was no c o n s i s t e n t d i f f e r e n c e b e t w e e n t h e d e c a y r a t e s o f t h e n c n - b r c a i n a t e d p h e n o l i c - r e s i n b o n d e d a n d t h e f i b e r - o n l y b o a r d s . F i g s . 5 a n d 7 show t h e n o n - l e a c h e d (NL) a n d l e a c h e d (L) g r o u p s o f t h r e e c o m p o s i t i o n s o f a l l n o n - b r o m i n a t e d h a r d b o a r d s , d e c a y e d by P A i n c r a s s a t a , a b r o w n - r o t f u n g u s , a f t e r 10 weeks o f i n c u b a t i o n . T h e o b s e r v a t i o n s p r e s e n t e d h e r e i n w o u l d be c o n s i s t e n t w i t h e f f e c t s o f t h e wet p r o c e s s u s e d f o r h a r d b o a r d p r o d u c t i o n , where l e a c h i n g by w a t e r a n d r e s u l t i n g s t e a m f o r m a t i o n d u r i n g h o t - p r e s s i n g w o u l d r e d u c e a n y f r e e p h e n o l s r e m a i n i n g i n t h e b o a r d s t o l e v e l s u n l i k e l y t o a f f e c t a n y s u b s e q u e n t g r o w t h o f f u n g i o n t h e b o a r d s . T h i s s i t u a t i o n w i t h h a r d b o a r d i s i n c o n t r a s t t o t h a t o b s e r v e d f o r p a r t i c l e b o a r d ( 1 2 0 ) , w h e r e p h e n o l - f o r m a l d e h y d e r e s i n i m p e d e d t h e a t t a c k o f w o o d - d e s t r o y i n g f u n g i a n d a n u r e a - f o r m a l d e h y d e r e s i n p r o m o t e d t h e a t t a c k . T h e s e t o x i c e f f c t s o f p h e n o l - f o r m a l d e h y d e r e s i n i n c o m p o s i t i o n b o a r d m a t e r i a l s w e r e s u g g e s t e d by s e v e r a l w o r k e r s ( 5 0 , 1 1 6 ) , a n d h a v e b e e n p r o p o s e d a s an e x p l a n a t i o n f o r t h e 57 r e s i s t a n c e to decay e x h i b i t e d by f r e s h l y pressed plywood bonded with phenolic glues (91). Since wax was i n c l u d e d among the present hardboard treatments along with the p h e n o l i c adhesive, i t c o u l d be expected t h a t the r e s u l t i n g r e d u c t i o n i n board w e t t a b i l i t y would reduce i t s r a t e of decay r e l a t i v e to board m a t e r i a l s without the wax a d d i t i v e . T h i s e f f e c t , however, was not observed, s i n c e there was no c o n s i s t e n t d i f f e r e n c e i n decay between boards with or without wax. Apparently, under the c o n d i t i o n s adapted i n c o n t r o l l i n g t h i s decay t e s t , untreated hardboard can be regarded as v u l n e r a b l e t o a t t a c k by d e s t r o y i n g f u n g i , e s p e c i a l l y the brown-r o t f u n g i . Hardboard has a high s u r f a c e area/volume r a t i o , as pointed out by L e v i (62), which a l l o w s higher a c c e s s i b i l i t y of the metabolic source to enzymatic a c t i v i t y than i s the case with s o l i d wood. A l s o , the presence o f broken wood f i b e r s makes a v a i l a b l e t o f u n g i , without having to penetrate any p r o t e c t i v e l a y e r s , the m a t e r i a l s o f a l l l a y e r s o f the c e l l w a l l . The a v a i l a b i l i t y of n u t r i e n t s i n hardboard i s important and has a gene r a l bearing on f u n g a l growth. The c o n d i t i o n s under which hardboards are manufactured are g u i t e severe. High temperatures and pressures a r e used, undoubtedly a f f e c t i n g the n a t u r a l bonding agent i n f i b e r b o a r d s . L i g n i n i s probably r e p o s i t i o n e d , i f not a l t e r e d . T h i s might render the l i g n i n u n s u i t a b l e as food m a t e r i a l f o r f u n g i such as w h i t e - r o t s , while at the same t i a e a l l o w i n g e a s i e r access to the carbohydrate m a t e r i a l . T h i s may e x p l a i n the wide discrepancy between the weight l o s s v a l u e s obtained by us i n g brown-rot and whi t e - r o t f u n g i as the decaying 58 a g e n t s ( T a b l e s 2 t o 4 , F i g . 3 ) . 2 . B r o m i n a t i o n B r o m i n a t i o n o f t h e A s p l u n d p u l p p r i o r t o t h e m a n u f a c t u r e o f h a r d b o a r d g r e a t l y i n c r e a s e d i t s r e s i s t a n c e t o d e c a y b y t h e f o u r b r o w n - r o t f u n g i ( F i g . 3 ) , w i t h a v e r a g e d e c a y w e i g h t l o s s e s f o r t h e n o n - l e a c h e d b o a r d s b e i n g r e d u c e d f r o m more t h a n 50% t o j u s t more t h a n 3%. L e a c h i n g of t h e b o a r d s b e f o r e d e c a y h a d l i t t l e e f f e c t on t h e n o n - b r o m i n a t e d m a t e r i a l , b u t s i g n i f i c a n t l y i n c r e a s e d t h e a v e r a g e d e c a y o f t h e b r o m i n a t e d b o a r d s t o a b o u t a n 18% w e i g h t l o s s . C o m p a r i s o n o f F i g s . 6 a n d 8 d e m o n s t r a t e s how l e a c h i n g a f f e c t e d t h e d e c a y a n d m y c e l i a l g r o w t h o n b r o m i n a t e d b o a r d s . R e s i s t a n c e t o d e c a y by C__ p u t e a n a a n d m o n t i c o l a , i m p a r t e d by b r o m i n a t i o n o f h a r d b o a r d , i s l e s s t h a n t h a t o b s e r v e d e a r l i e r f o r s o l i d s p r u c e wood b y F r y d m a n (31) . I n t h e l a t t e r c a s e , a t wood b r o m i n a t i o n l e v e l s s i m i l a r t o t h o s e u s e d f o r t h e A s p l u n d p u l p i n t h e p r e s e n t e x p e r i m e n t , n e g l i g i b l e d e c a y l o s s e s o c c u r r e d e i t h e r b e f o r e o r a f t e r l e a c h i n g . , T h e two w h i t e - r o t f u n g i e m p l o y e d h e r e i n were u n a b l e t o a t t a c k b r c m i n a t e d b o a r d s , e i t h e r l e a c h e d o r n o n - l e a c h e d ( T a b l e 2 ) . , T h i s c a n a l s o be s e e n i n F i g s . 9 a n d 11 w h e r e b o t h n o n -b r o m i n a t e d b o a r d s a n d t h e i r b r o m i n a t e d c o u n t e r p a r t s a r e s h o u n a f t e r e x p o s u r e t o P . v e r s i c o l o r a n d P. a d u s t u s . r e s p e c t i v e l y . T h i s was e x p e c t e d , s i n c e t h e b r o m i n a t i o n o f wood r e s u l t s i n t h e f o r m a t i o n o f b r o m h y d r i n s o f l i g n i n and a l s o l i g n i n o x i d a t i o n 59 w i t h t h e p r o d u c t i o n o f h y d r o b r o m i c a c i d ( 5 7 ) . T h e r e f o r e , i t was a s s u m e d t h a t t h e s e r e a c t i o n s w o u l d i n t e r f e r e more s e r i o u s l y w i t h t h e d e c a y by w h i t e - r o t t h a n b r o w n - r o t f u n g i , b e c a u s e o f t h e u t i l i z a t i o n o f b o t h l i g n i n a n d c e l l u l o s e by t h e f o r m e r a n d o n l y c e l l u l o s e by t h e l a t t e r f u n g i . The f r e e h y d r o b r o m i c a n d h y d r o c h l o r i c a c i d s , p r o d u c e d d u r i n g t h e o x i d a t i o n o f l i g n i n , a r e s u p p o s e d l y r e m o v e d ( n e u t r a l i z e d ) b y t h e a d d i t i o n o f c a l c i u m h y d r o x i d e f o l l o w i n g b r o m i n a t i o n . H o w e v e r , a n y o f t h e a c i d s g e n e r a t e d a n d r e m a i n i n g a f t e r h o t - p r e s s i n g s h o u l d be l e a c h a b l e a n d p r e s u m a b l y 14 d a y s o f c o l d - w a t e r l e a c h i n g o f t h e s m a l l b l o c k s u s e d i n t h e s e e x p e r i m e n t s s h o u l d r e m o v e m o s t o f t h i s t o x i c m a t e r i a l . The i n c r e a s e i n d e c a y w e i g h t l o s s o f b r o m i n a t e d b o a r d s , a t t a c k e d by t h e b r o w n - r o t f u n g i , f r o m a b o u t 3% t o 18% f o l l o w i n g l e a c h i n g ( F i g . 4) s u g g e s t s t h e r e m o v a l o f t h e s e a c i d s , a l t h o u g h no s i m i l a r r e s p o n s e was o b s e r v e d f o r t h e w h i t e - r o t f u n g i , w h i c h p r e s u m a b l y a r e c o n s i d e r a b l y r e p r e s s e d by t h e b r c m h y d r i n s o f l i g n i n . I t w o u l d seem p o s s i b l e t h a t t h e b r o m h y d r i n s o f l i g n i n a l s o a r e i n t e r f e r i n g w i t h t h e c e l l u l a s e s y s t e m s o f t h e b r o w n - r o t f u n g i a n d , t h e r e f o r e , r e d u c i n g by t w o -t h i r d s t h e r a t e o f d e c a y o f b o a r d s a t t a c k e d by t h e s e f u n g i . The m e c h a n i s m f o r s u c h a r e a c t i o n i s n o t k n o w n , a l t h o u g h t h e t o x i c e f f e c t o f t h e b r o m i n e a t o m i s w e l l r e c o g n i z e d ( 3 1 ) . Of c o u r s e , b r o m i n a t i o n a l s o r e s u l t s i n t h e h y d r o l y s i s o f h e m i c e l l u l o s e s , w h i c h a r e known t o b e e x t r e m e l y l a b i l e t o t h e h y d r o l y s i s c o n d i t i o n s c r e a t e d d u r i n g t h e b r o m i n e l i b e r a t i o n s t e p (57) . T h e r e f o r e , l e a c h i n g d u r i n g h o t - p r e s s i n g o f t h e h a r d b o a r d and a l s o p r i o r t o d e c a y t e s t i n g w o u l d r e s u l t i n l o s s e s o f s u g a r s 60 o t h e r w i s e a v a i l a b l e a s a f o o d s o u r c e f o r t h e f u n g i . T h i s r e m o v a l o f a f o o d s o u r c e a l s o c o u l d h e l p t o e x p l a i n t h e r e s i s t a n c e o f b r o m i n a t e d b o a r d s t o f u n g i c a u s i n g d e c a y . T h e s t r o n g e r i n t e r f e r e n c e o f l i g n i n b r c m h y d r i n s w i t h t h e d e c a y p r o c e s s b y w h i t e - r o t t h a n b r o w n - r o t f u n g i may a l s o s u g g e s t t h a t seme s y n e r g i s t i c e f f e c t e x i s t s b e t w e e n s e p a r a t e e n z y m e s y s t e m s w h i c h s i m u l t a n e o u s l y r e a c t w i t h t h e c e l l u l o s e a n d l i g n i n . T h e n e a r - z e r o w e i g h t l o s s i n w h i t e - r o t d e c a y o n b r c m i n a t e d b o a r d s seems t o i n d i c a t e t h a t t h e a c t i v i t y o f c e l l u l a s e s y s t e m i s a l s o r e t a r d e d i n a d d i t i o n t o i n t e r a c t i o n o f t h e l i g n i n - d e g r a d i n g enzyme w h i c h h a s u n d e r s t a n d a b l y b e e n i n a c t i v a t e d b e c a u s e o f t h e e x t e n s i v e m o d i f i c a t i o n o f t h e l i g n i n s u b s t r a t e b y b r o m i n a t i o n , T h u s , t h e s i m u l t a n e o u s r e m o v a l o f c e l l u l o s e a n d l i g n i n becomes d i f f i c u l t . •|i t r a b e a - , a b r o w n - r o t f u n g u s , was f o u n d t o be s u r p r i s i n g l y s e n s i t i v e t o g r o w i n g o n b r o m i n a t e d b o a r d , w h e r e i t s d e c a y w e i g h t l o s s e s w e r e a l m o s t n e g l i g i b l e c o m p a r e d w i t h t h o s e p r o d u c e d on t h e n o n - b r o m i n a t e d c o u n t e r p a r t . S i m i l a r c o m p a r i s o n s c a n be made a l s o w i t h o t h e r t h r e e b r o w n - r o t f u n g i . F i g . 10 d e p i c t s t h e e f f e c t o f b r o m i n a t i o n on t h e g r o w t h o f L . t r a b e a . 3 . l e a c h i n g L e a c h i n g f o r 14 d a y s o f t h e t h r e e t y p e s o f n o n - b r o m i n a t e d b o a r d s r e s u l t e d i n d r y - w e i g h t l o s s e s b e f o r e d e c a y o f l e s s t h a n 1%. H o w e v e r , i n s i m i l a r l e a c h i n g o f t h e b r o m i n a t e d b o a r d s , t h e 61 f i b e r o n l y , f i b e r p l u s p h e n o l i c r e s i n a n d f i b e r p l u s p o l y e t h y l e n i m i n e r e s i n b o a r d s , g a v e d r y - w e i g h t l o s s e s o f 7.0, 8,7 a n d 8 , 8 1 ( T a b l e 1 ) , r e s p e c t i v e l y . S u c h w e i g h t l o s s e s were e x p e c t e d , f o l l o w i n g t h e work o f F r y d m a n (31) a n d J u r a z s a n d P a s z n e r (57) . H e i g h t l o s s on b r o m i n a t e d b o a r d a l s o o c c u r r e d d u r i n g t h e i n c u b a t i o n p e r i o d e v e n t h o u g h n o b i o l o g i c a l a g e n t was i n v o l v e d . T h e h i g h l y h u m i d c o n d i t i o n s w i t h i n t h e i n c u b a t i o n e n v i r o n m e n t c r e a t e d seme c o n d e n s a t i o n i n t h e s o i l j a r s a n d m i g h t h a v e r e s u l t e d i n a d d i t i o n a l l e a c h i n g . T a b l e 1 t a b u l a t e s t h e w e i g h t l o s s v a l u e s o b t a i n e d d u r i n g t h e v a r i o u s s t a g e s o f t h e t e s t i n g p r o c e s s , b e f o r e a n d a f t e r p l a n t i n g . T h e e f f e c t s o f b o a r d l e a c h i n g on t h e d e g r e e o f b i o d e g r a d a t i o n b y f u n g i e m p l o y e d i s r e a d i l y o b s e r v a b l e i n T a b l e s 2, 5, a n d 6. T h e s e o b s e r v a t i o n s a r e r e a s o n a b l y c o n s i s t e n t w i t h t h e f a c t s t h a t w a t e r , d u r i n g t h e v a r i o u s s t a g e s o f b o a r d m a n u f a c t u r e , w o u l d be e x p e c t e d t o remove r e s i d u a l r e a c t i o n p r o d u c t s as s o l u b l e s a l t s , o r g a n i c a c i d s a n d o t h e r s o l u b l e h i g h - t e m p e r a t u r e d e c o m p o s i t i o n p r o d u c t s r e t a i n e d w i t h i n t h e b o a r d s f o l l o w i n g h o t -p r e s s i n g , W h i l e r e l a t i v e l y s m a l l a m o u n t s o f t h e s e m a t e r i a l s w o u l d be e x p e c t e d t o be g e n e r a t e d i n t h e u n t r e a t e d b o a r d s , c o n s i d e r a b l y l a r g e r amount a n d a d d i t i o n a l s o l u b l e c o m p o u n d s c o u l d be f o r m e d i n p r e s s i n g t h e b o a r d s made o f b r o m i n a t e d f i b e r s . L e a c h i n g o f t h e n o n - b r o m i n a t e d b o a r d s o n l y a f f e c t e d t h e s u b s e g u e n t r a t e o f a t t a c k by Pf- v e r s i c o l o r , where l e a c h i n g r e s u l t e d i n s i g n i f i c a n t l y i n c r e a s e d w e i g h t l o s s . A s i m i l a r r e s u l t was o b t a i n e d by D a C o s t a a n d O s b o r n e (25) , u s i n g D o u g l a s -62 f i r b l o c k s , where l e a c h i n g i n c r e a s e d t h e r e l a t i v e d e c a y w e i g h t l o s s e s by a b o u t 25% f o r JP. v e r s i c o l o r , w h e r e a s w i t h . . t r a b e a ; -t h e i n c r e a s e was o n l y a b o u t 6%. A l t h o u g h t h e w o o d p u l p u s e d i n t h e p r e s e n t e x p e r i m e n t s was c o n s i d e r a b l y w a s h e d d u r i n g t h e A s p l u n d p r o c e s s , t h e s u b s e g u e n t 14 d a y s o f c o l d - w a t e r l e a c h i n g s e e m e d t o r e m o v e some m a t e r i a l s t o x i c t o ^ v e r s i c o l o r , b u t t o w h i c h t h e o t h e r f u n g i were l e s s s e n s i t i v e . T h e s i g n i f i c a n c e o f l e a c h i n g t h e b r o m i n a t e d b o a r d s h a s b e e n d i s c u s s e d u n d e r t h e " B r c m i n a t i o n " . I n t e r e s t i n g l y , h o w e v e r , t h e p r e s e n t d a t a c o n t r a d i c t t h o s e o f F r y d m a n (31) who f o u n d t h a t t h e m a g n i t u d e o f d e c a y w e i g h t -l o s s e s on t h e b r o m i n a t e d wood s a m p l e s r a r e l y e x c e e d e d 3 t o 4%, r e g a r d l e s s w h e t h e r t h e l e a c h a b l e s were r e m o v e d o r n o t . I n t h e p r e s e n t s t u d y d e c a y w e i g h t - l o s s e s o f o v e r 20% were r e c o r d e d f o r t h r e e o u t o f f o u r b r o w n - r o t f u n g i f o l l o w i n g w a t e r l e a c h i n g t h o u g h t h e l o s s e s w i t h t h e w h i t e - r o t f u n g i r e m a i n e d n e g l i g i b l e . R e s u l t s i n d i c a t e t h a t , w h i l e d e c a y r e s i s t a n c e o f t h e n o n -l e a c h e d b r o m i n a t e d b o a r d s i s r e l a t i v e l y h i g h t o b r o w n - r o t f u n g i , a g o o d p a r t o f t h e r e s i s t a n c e w o u l d b e l e a c h e d o u t i f t h e b o a r d s become e x p o s e d t o l e a c h i n g w a t e r s d u r i n g s e r v i c e . F i g . 12 shows a v e r y s i g n i f i c a n t e x a m p l e o f t h e l e a c h i n g e f f e c t . T h e r e f o r e , u n l e s s b r o m i n a t e d b o a r d s a r e s e a l e d o r p r o t e c t e d f r o m w a t e r by some means i n e x t e r i o r s e r v i c e , t h e y s h o u l d b e u s e d p r e f e r a b l y i n d o o r s t o r e t a i n maximum e f f e c t i v e n e s s a g a i n s t p o s s i b l e a t t a c k by w o o d - d e s t r o y i n g f u n g i f o l l o w i n g l i m i t e d w e t t i n g o f t h e b o a r d . , l e a c h i n g a l s o c o n t r i b u t e s t o t h e s w e l l i n g o f h a r d b o a r d , e s p e c i a l l y a f t e r 1 4 - d a y s o a k i n g i n w a t e r . „ S w e l l i n g c a n r e s u l t i n 63 o p e n i n g o f a n y m i n u t e v o i d s i n t h e c e l l w a l l , m a k i n g t h e c e l l u l o s e o r l i g n i n c o m p l e x more a c c e s s i b l e t c e n z y m a t i c a t t a c k a n d , t h u s , r e s u l t i n g i n h i g h e r w e i g h t l o s s e s . T h e p o o r r e s p o n s e o f b r o m i n a t e d f i b e r s t o b o a r d s t r e n g t h i m p r o v e m e n t by r e s i n a d d i t i o n (57) c a n o n l y i n c r e a s e t h e d i s i n t e g r a t i o n o f f i b e r s a n d s u r f a c e a r e a / v o l u m e r a t i o u n d e r s e r i o u s l e a c h i n g . 4. flcisture C o n t e n t E x c e p t f o r t h e d e c a y o f b r o m i n a t e d b o a r d s b y L t t r a b e a , a l m o s t a l l b r o w n - r o t f u n g i , when d e c a y i n g e i t h e r ^ o n - b r o m i n a t e d o r b r o m i n a t e d b o a r d s , g a v e h i g h e r d e c a y r a t e s i f t h e i n i t i a l m o i s t u r e c o n t e n t s o f t h e b o a r d s were 8% t h a n when t h e y were 20% ( F i g . 3, T a b . 3 ) . T h i s i n c r e a s e i n d e c a y r a t e was s i g n i f i c a n t , a t l e a s t a t t h e 5% l e v e l , f o r t h e f o u r b r o w n - r o t f u n g i a n d P . v e r s i c o l o r ( T a b l e s 5 , 6 ) . T h e e f f e c t was c l e a r l y v i s i b l e d u r i n g t h e i n c u b a t i o n p e r i o d , when t h e m y c e l i u m o f t h e f u n g u s o n t h e f e e d e r s t r i p s q u i c k l y f l u f f e d up a n d o v e r g r o w t h o s e b l o c k s h a v i n g a low i n i t i a l m o i s t u r e c o n t e n t c o m p a r e d w i t h t h o s e a t 20% ( F i g . 14). T h i s r e s u l t c o n f l i c t s w i t h t h e r e s u l t s a n d t h e o r i e s p r o p o s e d by G r a n t and S a v o r y (36) who u s e d h a r d b o a r d ( p r e s u m a b l y made f r o m S c o t s p i n e a n d / o r s p r u c e ) a n d s h o w e d l i t t l e a t t a c k by C . p u t e a n a b e l o w 20% i n i t i a l M . C . i n a v e r m i c u l i t e b u r i a l t e s t . T h e s e a u t h o r s s u g g e s t e d f r o m t h e i r f i n d i n g s t h a t , e v e n u n d e r s a t u r a t e d a t m o s p h e r i c c o n d i t i o n s , t h e e q u i l i b r i u m m o i s t u r e c o n t e n t f o r h a r d b o a r d l a y w e l l b e l o w i t s d e c a y t h r e s h o l d . ea O b s e r v a t i o n s f r o m t h e p r e s e n t e x p e r i m e n t i n v o l v i n g f o u r b r o w n -r o t f u n g i , i n c l u d i n g t h e o n e u s e d by G r a n t and S a v o r y ( 3 6 ) , w o u l d s u g g e s t t h a t a t t a c k o f h a r d b o a r d , a t l e a s t u n d e r n o r m a l l a b o r a t o r y d e c a y t e s t c o n d i t i o n s , o c c u r s more r a p i d l y when t h e h a r d b o a r d i n i t i a l l y h a s a M . C . l e s s t h a n i t s e q u i l i b r i u m M . C . a t 100% r e l a t i v e h u m i d i t y . T h e s e r e s u l t s f o r h a r d b o a r d a l s o d i f f e r f r o m o b s e r v a t i o n s made by B e h r (12) c n s p r u c e p a r t i c l e b o a r d , where a p r e - w e t t i n g p r o c e d u r e i n c r e a s e d t h e s u b s e g u e n t d e c a y w e i g h t l o s s e s , u s i n g t h e f u n g u s L t , t r a b e a , b y a s much a s 12 t i m e s o v e r n o n - w e t t e d p a r t i c l e b o a r d . H o w e v e r , t h e r e s p o n s e s o f p a r t i c l e b o a r d , h a r d b o a r d a n d s o l i d wood t o M . C . and d e c a y c o u l d be g u i t e d i f f e r e n t due t o v a r i a t i o n s i n p a r t i c l e s i z e , a m o u n t o f r e s i n b i n d e r s a n d c h e m i c a l m o d i f i c a t i o n o f t h e wood i t s e l f . The d e c a y r a t e s by t h e two w h i t e - r o t f u n g i o f t h e t h r e e t y p e s o f h a r d b o a r d , b o t h n o n - b r o m i n a t e d a n d b r o o i n a t e d , seemed i n c o n s i s t e n t a n d u n r e l a t e d t o d i f f e r e n c e s i n i n i t i a l M . C , T h e e f f e c t o f l o w i n i t i a l m o i s t u r e c o n t e n t l e v e l o n t h e f u n g a l a c t i v i t y may h o l d t r u e o n l y a t t h e e a r l y s t a g e s o f i n c u b a t i o n , , I t may a c t u a l l y s t i m u l a t e t h e g r o w t h f o r a b i g g e r o r more a c t i v e f u n g a l p o p u l a t i o n i n e a r l y s t a g e s t o f a c i l i t a t e t h e f u r t h e r a t t a c k ; o r i t may a f f e c t t h e f u n g u s d e v e l o p m e n t t h r o u g h o u t t h e w h o l e i n c u b a t i o n p e r i o d . T h e e x p e r i m e n t a l d e s i g n f o r t h i s t e s t was u n a b l e t o f i n d c o n c l u s i v e a n s w e r t o s u c h s u p p o s i t i o n s a s o n l y one i n c u b a t i o n p e r i o d was u s e d . A s p o i n t e d o u t e a r l i e r , h a r d b o a r d h a s a h i g h s u r f a c e a r e a / v o l u m e r a t i o , i t w i l l be r a p i d l y a f f e c t e d by v a r y i n g w e a t h e r c o n d i t i o n s a n d w i l l be w e t t e d e a s i l y , e s p e c i a l l y i f t h e g l o s s y p r o t e c t i v e s u r f a c e 65 w e a r s away o r i s r e m o v e d as was t h e c a s e h e r e . T h e r e f o r e , t h e t i m e r e q u i r e d t o r e a c h e q u i l i b r i u m may be w i t h i n f i r s t few d a y s , c r e a t i n g e g u i l i b r i u m c o n d i t i o n s a t t h e e a r l y s t a g e s a n d , t h u s , o f f s e t t i n g t h e d i s p a r i t y o f m o i s t u r e c o n d i t i o n s s u p e r i m p o s e d i n i t i a l l y f o r t h e b l o c k s . I f s o , t h e a n s w e r m i g h t l i e i n t h e f o r m e r h y p o t h e s i s . 5 , S t e r i l i z a t i o n M e t h o d W i t h n o n - b r o m i n a t e d h a r d b o a r d , a l l f u n g i e x c e p t P . y e r s i c c l o r g a v e s i m i l a r d e c a y w e i g h t l o s s e s , w h e t h e r e t h y l e n e o x i d e o r wet h e a t was u s e d f o r s t e r i l i z i n g t h e b l o c k s b e f o r e i n c u b a t i o n ( T a b l e H). O n l y P t v e r s i c o l o r d i f f e r e d i n g i v i n g s i g n i f i c a n t l y g r e a t e r w e i g h t l o s s e s w i t h b l o c k s s t e r i l i z e d u s i n g e t h y l e n e o x i d e c o m p a r e d w i t h t h o s e u s i n g wet h e a t ( T a b l e 5* F i g u r e 1 3 ) . P r e v i o u s s t u d i e s , u s i n g P A v e r s i c o l o r t o d e c a y p o n d e r c s a p i n e wood ( 1 0 0 ) , c o u l d f i n d n o d i f f e r e n c e b e t w e e n t h e e f f e c t s o f e t h y l e n e o x i d e o r w e t - h e a t a s s t e r i l i z i n g a g e n t s , a l t h o u g h i n t h a t s t u d y a d i f f e r e n t s t r a i n o f PM] v e r s i c o l o r was u s e d t o t h a t u s e d i n t h e p r e s e n t t e s t s . W i t h b r o m i n a t e d h a r d b o a r d , e t h y l e n e o x i d e s t e r i l i z a t i o n made t h e m a t e r i a l s i g n i f i c a n t l y more s u s c e p t i b l e t o d e c a y b y t h e f o u r b r o w n - r o t f u n g i c o m p a r e d w i t h s i m i l a r b o a r d s s t e r i l i z e d u s i n g wet h e a t ( T a b l e s 4 , 6 , F i g u r e 3 ) . T h e i n c r e a s e i n d e c a y w e i g h t l o s s was a b o u t o n e - t h i r d more t h a n t h e v a l u e s o b t a i n e d u s i n g wet h e a t . I t w o u l d seem t h a t t h e s t r o n g a l k y l a t i n g e f f e c t 66 o f e t h y l e n e o x i d e i s i n t e r f e r i n g w i t h t h e f u n g i t o x i c i t y g e n e r a t e d by b r o m i n a t i o n o f t h e A s p l u n d p u l p . . C o n s i d e r i n g t h e d e c a y w e i g h t l o s s e s f o r t h e w h i t e - r o t f u n g i , i n s p i t e o f t h e s e d i f f e r e n c e s b e i n g f o r m a l l y s i g n i f i c a n t f o r v e r s i c o l o r t h e mean w e i g h t l o s s v a l u e s f o r b o t h f u n g i a r e a l l l e s s t h a n 2% a n d , t h e r e f o r e , r a t h e r l o w t o f o r m t h e b a s i s f o r a n y s t r o n g c o n c l u s i o n s . 67 CHAPTER V . .. CONCLUSIONS H a r d b o a r d s a r e s o m e t i m e s c o n s i d e r e d h i g h l y r e s i s t a n t t o d e t e r i o r a t i o n by f u n g i a n d b a c t e r i a . I t h a s now b e e n r e c o g n i z e d t h a t some o f t h e c o n t r a d i c t o r y r e s u l t s r e f l e c t d i f f e r e n c e s i n b o a r d c o m p o s i t i o n a s w e l l a s c o n d i t i o n s a d a p t e d i n c o n t r o l l i n g t h e d e c a y t e s t i n g m e t h o d s . T h e c h o i c e o f f u n g i may a l s o b e i m p o r t a n t a s t h e r e were no s p e c i f i c f u n g i r e c o m m e n d e d f o r t e s t i n g t h e b i o d e g r a d a t i o n o f h a r d b o a r d . The s o i l - j a r m e t h o d , m o d i f i e d f r o m ASTH D 1 4 1 3 - 7 6 , p r o v e d t o be a s u i t a b l e t e c h n i g u e f o r e v a l u a t i n g t h e d e c a y r e s i s t a n c e o f h a r d b o a r d . B r o m i n a t i o n o f A s p l u n d p u l p f o r h a r d b o a r d p r o d u c t i o n r e s u l t s i n a b o a r d w h i c h h a s a t l e a s t 16 t i m e s t h e r e s i s t a n c e t o d e c a y by f o u r common b r o w n - r o t f u n g i , a l t h o u g h t h i s r e s i s t a n c e i s r e d u c e d t o a b o u t f o u r t i m e s f o l l o w i n g a 1 4 - d a y p e r i o d o f c o l d - w a t e r l e a c h i n g o f t h e b o a r d . The f u n g u s L«_ t r a b e a was v e r y s e n s i t i v e t o g r o w i n g on b r o m i n a t e d b o a r d , where i t s d e c a y w e i g h t l o s s was n e g l i g i b l e c o m p a r e d w i t h t h a t p r o d u c e d on n o n -b r o m i n a t e d b o a r d . T h e two common w h i t e - r o t f u n g i t e s t e d d e c a y e d n o n - b r o m i n a t e d b o a r d s s l i g h t l y and b r o m i n a t e d b o a r d s n o t a t a l l . T h e b r o m h y d r i n s o f l i g n i n f o r m e d t h r o u g h t h e b r o m i n a t i o n o f p u l p may e x p l a i n t h e h i g h r e s i s t a n c e o f t r e a t e d b o a r d a g a i n s t t h e w h i t e - r o t d e c a y i n g f u n g i a s t h e s u b s t r a t e , i . e . , l i g n i n , w h i c h i s t h e m a i n s o u r c e o f f o o d , has b e e n a l t e r e d , r e n d e r i n g t h e e n z y m e s i n a c t i v e . , L e a c h i n g c a n c a u s e d r a s t i c d e c r e a s e i n r e s i s t a n c e c r e a t e d 68 by bromination. I t seems t h a t , unless the t r e a t e d board i s s e a l e d or protected from water by seme means i n s e r v i c e , i t should be used p r e f e r a b l y i n d o o r s t o r e t a i n maximum e f f e c t i v e n e s s a g a i n s t decay. There was l i t t l e d i f f e r e n c e o f p r a c t i c a l importance i n the decay r e s i s t a n c e cf hardboard made e i t h e r without adhesive or with p h e n o l i c or p o l y e t h y l e n i m i n e adhesive plus wax. However, evidence suggests t h a t a d d i t i o n of p o l y e t h y l e n i m i n e made the boards s l i g h t l y more s u s c e p t i b l e t o decay by s e v e r a l o f the f u n g i , Hardboard samples c o u l d be s t e r i l i z e d with e i t h e r e thylene oxide or wet-heat, although some i n t e r a c t i o n between the bromhydrins of l i g n i n and ethylene oxide was suggested. The most r a p i d decay occ u r r e d when the hardboard samples i n i t i a l l y had low (8%) i n s t e a d of high (20%) M.C. upon being p l a c e d i n the c u l t u r e j a r s . 69 L I T E R A T U R E C I T E D 1. A k a i , S . and U e y a m a , A . 1960 . S t u d i e s on t h e m i c r o b i a l s t a i n a n d d e c a y o f b u i l d i n g b o a r d s a n d t h e i r p r e v e n t i o n . I . F o r c e d - d e c a y t e s t s on b u i l d i n g b o a r d s u s i n g some w o o d - d e s t r o y i n g f u n g i . J . J a p a n Wood R e s c h . S o c . 6 ( 3 ) : 1 2 8 - 1 3 2 . 2. A m e r i c a n S o c i e t y f o r T e s t i n g a n d M a t e r i a l s . 1976. S t a n d a r d m e t h o d f o r t e s t i n g wood p r e s e r v a t i v e s by l a b o r a t o r y s o i l - b l o c k c u l t u r e s . ASTM D e s i g n a t i o n D 1 4 1 3 - 7 6 , P h i l a d e l p h i a , PA* 1976 y e a r b o c k , p p . 4 2 4 - 4 3 3 . , 3.... _ _ _ ._ . _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ . ' • , 1976 . . D e f i n i t i o n s o f t e r m s r e l a t i n g t o wood—based f i b e r a n d p a r t i c l e p a n e l m a t e r i a l s . ASTM D e s i g n a t i o n D 1 5 5 4 - 6 7 , P h i l a d e l p h i a , P A . 1976 y e a r b o o k , p p . ; 4 3 9 - 4 4 2 . 4 . A m e r i c a n Wood P r e s e r v e r s A s s o c i a t i o n . 1977 . M e t h o d t o d e t e r m i n e t h e c o m p a r a t i v e l e a c h a b i l i t y o f wood p r e s e r v a t i v e s . AWPA S t a n d a r d M 1 1 - 7 7 , W a s h i n g t o n , D* C . 5. A n o n y m o u s . 1 9 6 8 . P l a n t f o r f l a m e p r o o f i n g by b r o m i n a t i o n o f f i b e r b o a r d g r a d e p u l p f o r i n s u l a t i o n a n d h a r d b o a r d . R e p o r t b y S t a t e o f I s r e a l , M i n i s t r y o f Commerce a n d I n d u s t r y , I n s t i t u t e f o r F i b e r s a n d F o r e s t P r o d u c t s R e s e a r c h , J e r u s a l e m . 15 p p . ; 6. B e c k e r , G . and D e p p e , H - J . 1970. B e h a v i o r o f u n t r e a t e d p a r t i c l e b o a r d a n d p a r t i c l e b o a r d c h e m i c a l l y t r e a t e d a g a i n s t o r g a n i s m s . H o l z f o r s c h u n g und H o l z v e r w e r t u n g 21 ( 5 ) : 1 0 3 - 1 0 7 ; / 7 . 1974. A s p e c t s , r e s u l t s a n d t r e n d s i n wood p r e s e r v a t i o n , an i n t e r d i s c i p l i n a r y s c i e n c e . Wood S c i . T e c h n o l . 8 : 1 6 3 - 1 8 3 . 8 . B e h r , E . A . a n d H u b e r t J r . , A . J . 1951 , P r e s e r v a t i o n o f f i b e r i n s u l a t i n g b o a r d w i t h c o p p e r p e n t a c h l o r o p h e n a t e , T a p p i 34 : 5 1 9 - 5 2 3 . 9 . _ . 1972 . D e v e l o p m e n t o f r e s p i r o m e t r y a s a m e t h o d f o r e v a l u a t i n g wood p r e s e r v a t i v e s . F o r e s t P r o d . J . t 22 (4) : 2 6 - 3 1 . 10. 70 11 . B e h r , E . A . 1973 . D e c a y t e s t m e t h o d . I n : Hood D e t e r i o r a t i o n a n d i t s P r e v e n t i o n b y P r e s e r v a t i v e T r e a t m e n t s . N i c h o l a s , D . D . ( E d . ) 1 s t E d . V o l . I . D e g r a d a t i o n a n d P r o t e c t i o n o f H o o d . S y r a c u s e U n i v . P r e s s , S y r a c u s e , N. Y . p p . 2 1 7 - 2 4 6 . 12 . 1977. E f f e c t o f p r e - w e t t i n g o f p a r t i c l e b o a r d i n l a b o r a t o r y d e c a y t e s t . I n t . B i o d e t r n . B u l l . 1 3 ( 1 ) : 9 - 1 1 . 13 . B o s s h a r d , H . fl. a n d F u t o , L . P . 1 9 6 3 . W e a t h e r i n g r e s i s t a n c e o f p l y w o o d b o n d e d a n d c o a t e d w i t h p h e n o l f o r m a l d e h y d e . F o r e s t P r o d . J . 13 ( 1 2 ) : 5 5 7 -5 6 1 . 14. E o y c e , J. S . 1961 . F o r e s t P a t h o l o g y . 3 r d E d . M c G r a w - H i l l Book C o m p a n y , New Y o r k . s 572 p p . 15. B r a v e r y , A . F . a n d G r a n t , C . 1 9 7 1 . , P r e l i m i n a r y i n v e s t i g a t i o n s i n t o t h e u s e o f a t h i n s t r i p t e n s i l e s t r e n g t h f o r r a p i d e v a l u a t i o n o f wood p r e s e r v a t i v e s a g a i n s t B a s i d i o m y c e t e s f u n g i . , I n t . B i o d e t r n . B u l l . 7 ( 4 ) : 1 6 9 - 1 7 3 . 16 . B r o w n e , F . L . 1958 . T h e o r i e s o f c o m b u s t i o n o f wood a n d i t s c o n t r o l . f USDA F o r e s t S e r v . S e p t . N o . 2 1 3 6 . F o r e s t P r o d . L a b . M a d i s o n , W i s . 69 p p . 17 . B u i l d i n g B e s e a r c h E s t a b l i s h m e n t I n f o r m a t i o n . \; 1975. F a c t o r s a f f e c t i n g f i b r e b u i l d i n g b o a r d s i n s e r v i c e . B B E / I S / 2 / 7 5 i P r i n c e s R i s b o r o u g h L a b o r a t o r y , P r i n c e s R i s b o r o u g h , B u c k s . , E n g l a n d . 4 PP . 18. C a n a d i a n S t a n d a r d s A s s o c i a t i o n . 1974. S t a n d a r d 0 8 0 , Wood p r e s e r v a t i o n . C a n a d i a n S t a n d a r d s A s s o c i a t i o n , R e x d a l e , O n t a r i o . 79 p p . 19. C a r t w r i g h t , K . S t . G . a n d F i n d l a y , W. P . K. , 1 9 5 8 . , D e c a y o f t i m b e r a n d i t s p r e v e n t i o n . 2 n d E d . 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Z u r S i t u a t i o n d e s C h e m i s e h e n S c h u t z e s von H o l z w e r k s t o f f e n g e g e n F a u l n i s , H o l z R o h - w e r k s t o f f 33 : 1 2 4 - 1 2 8 . , 2 8 . :_ , _____ . 1 S 7 7 . T e c h n o l o g i c a l a d v a n c e s i n t h e p r o d u c t i o n and t e s t i n g o f p r e s e r v e d wood—based p a n e l p r o d u c t s . J . I n s t . , Hood S c i . 7 ( 5 ) : 2 0 - 2 5 . 2 9 . D i c k i n s o n , D. J . 1 9 7 4 . A new t e c h n i q u e f o r s c r e e n i n g f u n g i c i d e f o r wood p r e s e r v a t i o n . I n t . B i o d e t r n . B u l l . 10 ( 2 ) : 4 9 - 5 1 . , 3 0 . D u n c a n , C . G . a n d E s l y n , H . E , 1966. H o o d - d e c a y i n g A s c o m y c e t e s and F u n g i i m p e r f e c t i . M y c o l o g i a 5 8 : 6 4 2 - 6 4 5 . 3 1 . F r y d r a a n , C . 1968 . D e c a y r e s i s t a n c e o f b r o m i n a t e d wood. U n p u b l i s h e d p r o g r e s s r e p o r t No. 4, I n s t . F i b . F o r , P r o d . 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I n f l u e n c e c f va r i o u s i n i t i a l moisture content on decay o f s i t k a spruce and sweetgum sapwood by Poly_;-orus•-v e r s i c o l o r i n the s o i l - b l o c k t e s t . Phytopathology 63: 235-237. 76 84 . R i c h a r d s , C . A . a n d a d d o n s , B , M. , 1947 . L a b o r a t o r y m e t h o d s f o r e v a l u a t i n g wood p r e s e r v a t i v e s : P r e l i m i n a r y c o m p a r i s o n o f a g a r and s o i l c u l t u r e t e c h n i g u e s u s i n g i m p r e g n a t e d wood b l o c k s . P r o c . Amer , Wood P r e s e r v . A s s o c . 4 3 : 4 1 - 5 8 , 8 5 . B o w e l l , R. M. a n d G u t z m e r , D . I . 1975 . C h e m i c a l m o d i f i c a t i o n o f w o o d : R e a c t i o n s o f a l k y l e n e o x i d e s w i t h s o u t h e r n y e l l o w p i n e . Hood S c i . 7 ( 3 ) : 2 4 0 -246 . 8 6 . 1977 , N o n c o n v e n t i o n a l wood p r e s e r v a t i o n m e t h o d s . I n : H o o d T e c h n o l o g y : C h e m i c a l A s p e c t s , G o l d s t e i n , I!. S . ( E d . ) ACS S y m p o s i u m S e r i e s : 43. A m e r i c a n C h e m i c a l S o c i e t y , W a s h i n g t o n , D . C . p p . 4 7 - 5 6 . 8 7 . R u f f i n , E . T . 1 9 6 0 . E x t e r i o r d u r a b i l i t y o f h a r d b o a r d . F o r e s t P r o d . J . 10 ( 7 ) : 3 3 6 - 3 4 1 . 8 8 . R y d h o l m , S . A . 1965. P u l p i n g P r o c e s s e s . I n t e r s c i e n c e P u b . , J o h n s o n W i l e y & S o n s I n c . New Y o r k -L o n d o n - S y d n e y , p p . 3 9 5 - 3 9 8 . 8 9 . S a f o - S a m p a h , S . a n d G r a h a m , R. D. 1976 . R a p i d a g a r s t i c k b r e a k i n g - r a d i u s t e s t t o d e t e r m i n e t h e a b i l i t y o f f u n g i t o d e g r a d e wood. 7 Hood S c i . , , 9 ( 2 ) : 6 5 - 6 9 . 9 0 . S a v o r y , J . G . 1954 . B r e a k d o w n o f t i m b e r by A s c o m y c e t e s a n d F u n g i i m p e r f e c t i . A n n . A p p l . / B i o l . 4 1 : 3 3 6 -3 4 7 . 9 1 . 1969, T e s t i n g t h e f u n g u s r e s i s t a n c e o f b o a r d m a t e r i a l s . D u n c k e r a n d H u m b l d t , B e r l i n . M a t . u n d O r g , S u p p l . 2 : 4 9 - 5 6 , ; 92 . S c h e f f e r , T . C . a n d V e r a l l , A . ,,Fi, 1973 . >/ P r i n c i p l e s f o r p r o t e c t i n g wood b u i l d i n g s f r o m d e c a y . , OSDA F c r e s t S e r v , R e s , P a p e r F P L 190 . , F o r e s t P r o d . L a b , M a d i s o n , H i s , ; 57 p p . 9 3 . \ _ . 1973 , M i c r o b i o l o g i c a l d e g r a d a t i o n a n d t h e c a u s a l o r g a n i s m s . I n : Hood D e t e r i o r a t i o n and i t s P r e v e n t i o n b y P r e s e r v a t i v e T r e a t m e n t s . N i c h o l a s , D, D. ( E d . ) 1 s t E d . V o l . I . D e g r a d a t i o n a n d P r o t e c t i o n o f Wood. S y r a c u s e U n i v . P r e s s , S y r a c u s e , N . Y . p p . 3 1 - 1 0 6 . 94 . S c h m i d t , E . L , , F r e n c h , D , H . , G e r t j e j a n s e n , R . 0 . , H e r m a n n , J . , a n d H a l l , H . 1978 . S t r e n g t h r e d u c t i o n s i n p a r t i c l e b o a r d c a u s e d by f u n g i . F o r e s t P r o d . J . 2 8 ( 2 ) : 2 6 - 3 1 . 9 5 . S h a r p , R. F . a n d E g g i n s , H , 0 . . / » . , / 1968 . A r a p i d s t r e n g t h method f o r d e t e r m i n i n g t h e b i o d e t e r i o r a t i o n o f w o o d . I n t . B i o d e t r n . B u l l . / 4 ( 1 ) : 6 3 - 6 6 . 77 9 6 . S m i t h , B , S . 1 9 6 5 . S t e r i l i z a t i o n o f wood t e s t b l o c k s b y v o l a t i l e c h e m i c a l s : e f f e c t s o n L e n t i n u s l e p i d e u s , B r i t , M y c o l . S o c . T r a n s . . / 4 8 : 3 4 1 - 3 4 7 . 9 7 . . . 1968 . E f f e c t o f m o i s t u r e c o n t e n t on t h e s t e r i l i z a t i o n o f w o o d , u n d e r v a c u u m , by p r o p y l e n e a n d e t h y l e n e o x i d e s . C a n a d i a n J . o f B o t a n y 46 : 2 9 9 - 3 0 3 . 1 9 6 9 . Hood p r e s e r v a t i v e t o x i c i t y e v a l u a t i o n u s i n g wood w e i g h t l o s s a n d f u n g a l r e s p i r a t i o n m e t h o d s . Hood S c i . 2 ( 1 ) : 4 4 - 5 3 . _ . 1 9 7 0 . R e s p o n s i b i l i t i e s a n d r i s k s i n v o l v e d i n t h e u s e o f w o o d - p r o t e c t i n g c h e m i c a l s . C a n . D e p t . N a t , H e a l t h W e l f a r e . O c c u p . H e a l t h R e v . 21 (3-4) : 1 - 6 . S h a r m a n , C , V . 1 9 7 1 . E f f e c t o f gamma r a d i a t i o n , w e t - h e a t , and e t h y l e n e o x i d e s t e r i l i z a t i o n o f wood on i t s s u b s e q u e n t d e c a y by f o u r w o o d — d e s t r o y i n g f u n g i . Wood a n d F i b e r 2 ( 4 ) : 3 5 6 - 3 6 2 . 1 9 7 4 . D e s t r u c t i v e a g e n c i e s o f wood f u n g i . P r o c , A m e r i c a n Wood P r e s e r v . A s s o c . 7 0 : 8 1 - 8 8 . . 1975 . E c o n o m i c a s p e c t s o f b a c t e r i a i n w o o d . I n : B i o l o g i c a l T r a n s f o r m a t i o n o f Wood by M i c r o o r g a n i s m s . S p r i n g e r - V e r l a g , B e r l i n , p p . 8 9 -102. 103. . 1 9 7 5 . A u t o m a t i c r e s p i r a t i o n a n a l y s i s o f t h e f u n g i t o x i c p o t e n t i a l o f wood p r e s e r v a t i v e s , i n c l u d i n g a n o x a t h i i n . F o r e s t P r o d . «J. 2 5 ( 1 ) : 4 8 - 5 3 . 104. _ _ _ _ 1975 . R e s p i r a t i o n m e t h o d s t o f o l l o w wocd d e c a y a n d e v a l u a t e t o x i m e t r i c p o t e n t i a l o f wood p r e s e r v a t i v e s . M a t . u n d O r g . 1 0 ( 4 ) : 2 4 1 - 2 5 3 . . 1977 . P r o t e c t i o n a n d p r e s e r v a t i o n o f wood a g a i n s t a t t a c k by f u n g i . W e s t . F o r . P r o d . L a b . I n f o r m a t i o n B e p o r t V P - X - 1 7 0 . F i s h . , 5 E n v i r o n . C a n a d a , V a n c o u v e r , B . C . 14 p p . _ _ . 1978, A new l i d c l o s u r e f o r f u n g a l c u l t u r e v e s s e l s g i v i n g c o m p l e t e p r o t e c t i o n a g a i n s t m i t e i n f e s t a t i o n a n d m i c r o b i o l o g i c a l c o n t a m i n a t i o n , M i c o l o g i a 70 (3) : — , 107. S m i t h , S i H . 1 9 7 0 . T r e e P a t h o l o g y : A S h o r t I n t r o d u c t i o n . A c a d e m i c P r e s s , New Y o r k . p p . 150-174. 9 8 . . 9 9 . •_ 100. _ 101. . 102. . 105 . 106. , 78 108 . S p a l t , H , A . 1977* C h e m i c a l c h a n g e s i n wood a s s o c i a t e d w i t h wood f i b e r .board m a n u f a c t u r e . I n : Wood T e c h n o l o g y : C h e m i c a l A s p e c t s , G o l d s t e i n , I . S . , ( E d . ) ACS S y m p o s i u m S e r i e s : 4 3 . A m e r i c a n C h e m i c a l S o c i e t y , W a s h i n g t o n , D. C . p p . 1 9 3 - 2 1 9 . 109 . S t o l l e y , I . 1958 . Some m e t h o d s f o r t r e a t i n g p a r t i c l e b o a r d s t o i n c r e a s e t h e i r r e s i s t a n c e t c f u n g i a n d t e r m i t e s . P r o c . I n t e r n a t i o n a l C o n s u l t a t i o n o n I n s u l a t i n g B o a r d , H a r d b o a r d a n d P a r t i c l e b o a r d . , G e n e v a , 1957 . P a p e r 5 . 3 8 . F A O , Some. 6 p p . 110. S t r a n k s , D . W . 1976 . Wood p r e s e r v a t i v e s : T h e i r d e p l e t i o n a s f u n g i c i d e s a n d f a t e i n t h e e n v i r o n m e n t . F o r e s t r y T e c h . S e p t . N o . 10 . F o r e s t S e r v . D e p t . E n v i r o n . C a n a d a . O t t a w a , O n t a r i o . 35 PP . . 111. S y s k a , A . D, 1969 , E x p l o r a t o r y i n v e s t i g a t i o n o f f i r e - r e t a r d a n t t r e a t m e n t s f o r p a r t i c l e b o a r d . OSDA F o r e s t S e r v . R e s . N o t e F P L - 2 0 1 . F o r e s t P r o d . L a b . M a d i s o n , W i s . 20 p p . 112. T h o m p s o n , W. S, a n d D u s t , J . V . 1971 . P o l l u t i o n c o n t r o l i n t h e wood p r e s e r v i n g i n d u s t r y . P a r t I . N a t u r e a n d s c o p e o f t h e p r o b l e m . , F o r e s t P r o d . J . 21 ( 9 ) : 7 0 - 7 5 . 113. . _ _ . , 1973 . P o l l u t i o n c o n t r o l . I n : Wood D e t e r i o r a t i o n a n d i t s P r e v e n t i o n b y P r e s e r v a t i v e T r e a t m e n t s , N i c h o l a s , D . D , (Ed . ) 1 s t E d . , V o l . I I . P r e s e r v a t i v e s a n d P r e s e r v a t i v e S y s t e m s . S y r a c u s e U n i v . P r e s s , S y r a c u s e , N. Y. p p . 3 4 5 -3 9 5 . 114. T o o l e , E . B . 1 9 7 1 . E v a l u a t i o n o f wood p r e s e r v a t i v e s u s i n g c r u s h i n g s t r e n g t h . P h y t o p a t h o l o g y 6 1 : 1 8 2 -183 . 115 . f ___••,' 1973 . O x y g e n u t i l i z a t i o n a n d w e i g h t l o s s a s s o c i a t e d w i t h d e c a y by w o o d — d e c a y i n g f u n g i . Wood S c i . 6 ( 1 ) : 5 5 - 6 0 , 116. , B a r n e s , H . M. 1974 . B i o d e t e r i o r a t i o n o f p a r t i c l e b o a r d . F o r e s t P r o d . J . 24 ( 1 0 ) : 5 5 - 5 7 . 1 1 7 , , 1 9 7 5 . O x y g e n u t i l i z a t i o n by d e c a y f u n g i f o r t h e e v a l u a t i o n o f wood p r e s e r v a t i v e s . , F o r e s t P r o d . J . 2 5 ( 7 ) : 4 6 - 4 8 . 118. U r b a n i k , E . 1969 . I n v e s t i g a t i o n s on t h e p r e s e r v a t i o n o f p a r t i c l e b o a r d a n d f i b e r b o a r d a g a i n s t f u n g i a n d i n s e c t s . D u n c k e r a n d H u m b l o t , B e r l i n . M a t . und O r g . S u p p l . 2 : 9 5 - 1 0 2 . 79 119. W i l c o x , W. W. 1973. D e g r a d a t i o n i n r e l a t i o n t o wood s t r u c t u r e . I n : Wood D e t e r i o r a t i o n a n d i t s P r e v e n t i o n by P r e s e r v a t i v e T r e a t m e n t s . N i c h o l a s , D . D . ( E d . ) 1 s t E d . V o l . I . D e g r a d a t i o n a n d P r o t e c t i o n o f Wood. S y r a c u s e U n i v . P r e s s , S y r a c u s e , New Y o r k . p p . 1 0 7 - 1 4 8 . 120. H i l l e i t n e r , H . 1965 . , T h e b e h a v i o r o f wood p a r t i c l e b o a r d s u n d e r a t t a c k by B a s i d i o m y c e t e s . P a r t I . D e c o m p o s i t i o n o f p a r t i c l e b o a r d s by B a s i d i o m y c e t e s . H o l z B o h - W e r k s t o f f 23 : 2 6 4 - 2 7 1 . 1 2 1 . • . , „ _ _ _ _ _ . 1966 . U b e r den ftbbau v o n H o l z s p a n p l a t t e n d u r c h M o d e r f a e u l e p i l z e . M a t . und O r g . S u p p l . 1 : 7 7 - 8 8 . 122. Z a b i c k y , J . 1967 . T h e c h e m i s t r y o f b r o m i n a t i o n o f w o o d . I I I . M a i n p a t h s o f b r o m i n e c o n s u m p t i o n . , , I s r a e l J , Chem. 5 : 146. 123. Table 1. Weight losses of test blocks during the preparation period and under comparative control situation in s o i l jars during incubation. HARDBOARD COMPOSITION PROCEDURE1: •.-.-.•V , ' ; -f: 7 FIBER ONLY FIBER & RESIN PHENOLIC & WAX FIBER RESIN & PEI & WAX Non-Brominated Brominated Non-Brominated Brominated Non-Brominated Brominated NL-S-MH 1 0.3 3.2 0.5 3.7 0 4.0 Before L-S-MH 2 0.7 ;/ 7.0 0.9 8.7 0.1 8.8 Planting L-S-ML 3 0.9 7.6 1.2 9.6 0.5 9.3 L-EO-ML 4 0.6 . 6.8 0.7 7.4 0.2 6.6 NL-S-MH .1 0 3.6 0 4.8 0 6.8 After L-S-MH 2 0 1.7 0 2.3 0 4.3 Planting L-S-ML 3 0 0.7 0 2.2 0 3.9 L-EO-ML 4 0 0.3 0 1.5 0 1.6 1 For procedures 1, 2, 3, 4 refer to Figure 2. Table 2. Effect of leaching on the resistance to decay of non-brominated and brominated hardboard. Decay weight losses i n percent. HARDBOARD COMPOSITION HARDBOARD TREATMENT FUNGUS FIBER & PHENOLIC RESIN &.WAX FIBER & PEI RESIN & WAX Non-Leached (NL) Leached (L) NL L NL L NL L NL L NL Coniophora puteana Lenzites trabea Poria incrassata Poria mentiaola Polyporus adustus Polyporus versicolor FIBER ONLY Noh-Brominated Brominated Non-Brominated Brominated Non-Brorainated Brominated 38.2 40.0 58.5 54.6 50.8 54.8 50.1 49.3 0.8 0.3 9.6 15.8 10.0 25.7 2.2 2.4 0 32.4 0 26.5 0 0.3 0 0 39.6 34.6 59.3 56.9 53.2 52.3 55.8 53.7 0.4 0.7 4.2 10.6 6.6 13.6 1.0 1.0 0.1 27.9 1.0 26.2 0.9 1.2 0.6 0.4 37.6 39.4 63.5 63.6 60.9 58.9 58.8 57.8 7.3 10.2 1.2 8.6 7.9 19.3 1.2 0.1 7.4 25.6 0.8 17.3 1.1 1.8 0.3 0.2 OO Table 3. E f f e c t of the i n i t i a l m oisture content of leached, non-brominated and brominated hardboard on i t s r e s i s t a n c e to decay. Decay weight l o s s e s i n percent. HARDBOARD COMPOSITION HARDBOARD TREATMENT FUNGUS FIBER & PHENOLIC RESIN & WAX FIBER & PEI RESIN & WAX I n i t i a l 20 Moisture Content 8 20 8 20 8 20 8 20 8 20 8 FIBER ONLY Non-Brominated Brominated Non-Brominated Brominated Non-Brominated Brominated Coniophora puteana Lenzites trabea Poria incrassata Poria monticola Polyporus actus tus Polyporus versicolor 40.0 41.9 54.6 57.6 54.8 54.6 49.3 56.8 0.3 0.1 15.8 14.0 25.7 28.0 2.4 6.1 32.4 38.6 26.5 39.9 0.3 0.9 0 1.2 34.6 38.3 56.9 62.7 52.3 55.4 53.7 59.3 0.7 0.1 10.6 6.7 13.6 29.2 1.0 0.3 27.9 32.0 26.2 42.4 1.2 0.1 0.4 1.4 39.4 45.6 63.6 63.8 58.9 62.2 57.8 59.5 10.2 6.6 8.6 14.8 19.3 27.4 0.1 0.4 25.6 27.9 17.3 33.9 1.8 1.4 0.2 1.3 OO Table 4. E f f e c t of method of s t e r i l i z a t i o n of leached, non-brominated and brominated hardboard on i t s r e s i s t a n c e to decay. Decay weight l o s s e s i n percent. HARDBOARD COMPOSITION TMATMEOT F U N G U S FIBER ONLY F I B E R & P H E N 0 L I C FIBER & PEI TREATMENT FIBER ONLY RESIN & WAX RESIN & WAX Non-Brominated Brominated Non-Brominated Brominated Non-Brominated Brominated S t e r i l i z a t i o n Method* EO 38.3 38.5 39.7 43.6 42.9 35.9 Coniophora puteana S 41.9 28.0 38.3 29.2 45.6 27.4 EO 57.7 9.7 59.0 5.3 64.3 3.4 Lenzites tvabea S 57.6 6.1 62.7 0.3 63.8 0.4 EO 53.3 46.2 55.2 44.8 60.6 37.6 Porta inorassata •S 54.6 38.6 55.4 32.0 62.2 27.9 EO 57.4 49.3 57.0 50.5 60.2 35.5 Porta montiaola S 56.8 39.9 59.3 42.4 59.5 33.9 EO 0.0 0.8 0.0 0.8 0.4 0.5 Polyporus adustus S 0.1 0.9 0.1 0.1 6.6 1.4 EO 17.3 0 13.9 0.4 20.3 0 Polyporus versicolor 14.0 1.2 6.7 1.4 14.8 1.3 * EO - ethylene oxide under vacuum; S - wet heat (121°C) Table 5. S t a t i s t i c a l evaluation of the decay results for non-brominated hardboard. Source Coniophora Lenzites Poria puteana trabea incrassata DF MS F Sign MS F Sign MS F Sign Composition (C) 2 43.60 2.95 183.66 47.50*** 259.83 231.30*** Sterilization (S) 1 16.17 1.09 6.10 1.58 6.62 5.89* Moisture Content (M) 1 91.65 6.20* 53.10 13.70*** - 26.67 23.70* Leaching (L) 1 1.45 0.10 25.22 6.52*. 0.60 0.59 + C x S 2 14.10 0.95 11.35 2.93 1.01 0.90 C x M 2 9.33 0.63 16.25 4.20* 7.68 6.83** C x L 2 30.83 2.09 8.18 2.12 19.80 17.60*** Residual 36 14.79 3.87 1.12 Source Poria Polyporus Polyporus montioola adustus versicolor DF MS F Sign MS . F Sign MS F Sign Composition (C) 2 127.59 39.70*** 25.96 19.00*** 113.85 24.80*** Sterilization (S) 1 0.63 0.20 39.02 3.84 172.81 • 37.60*** + Moisture content (M) 1 146.52 45.60*** - 13.50 1.33 + 0.09 0.02 Leaching (L) 1 10.27 3.20 5.32 0.52 + 266.00 57.90*** + C x S 2 6.17 1.92 19.73 1.94 7.36 1.60 C x M 2 17.33 5.40* 6.86 0.68 56.00 12.20*** C x L 2 0.91 0.28 6.26 0.62 0.83 0.20 Residual 36 3.21 10.15 4.60 NOTES: * Significant at 5% level ** Significant at 1% level *** Significant at 0.1% level + means weight losses greater with ethylene oxide, higher moisture content and leaching than with wet heat, lower moisture content or non-leaching respectively; - means opposite to +. Table 6. St a t i s t i c a l evaluation of the decay results for brominated hardboard. Source Coniophora puteana Lenzites trabea Poria inorassata DF MS F Sign MS F Sign MS F Sign Composition (C) 2 37.27 1.06 66.65 38.40*** 89.60 8.32*** Sterilization (S) 1 742.59 21.20*** + 88.94 51.20*** + 604.01 56.10*** + Moisture Content (M) 1 453.27 12.90*** - 7.59 4.37* 109.23 10.15** -Leaching (L) 1 771.20 22.00*** + 0.48 0.28 4089.87 379.87*** + C x S 2 18.64 0.53 2.16 1.25 13.79 1.28 C x M 2 89.59 2.55 10.42 6.00** 7.92 0.73 C x L 2 38.51 1.10 1.17 0.67 105.93 9.84*** Residual 36 35.09 1.74 10.77 Source DF Poria montioola Polyporus adustus Polyporus versicolor MS F Sign MS F Sign MS F Sign Composition (C) 2 309.50 14.20*** 2.12 12.40** 1.41 8.18** Sterilization (S) 1 244.48 11.20** + 0.07 0.41 - 14.26 87.70*** -Moisture content (M) 1 1418.34 65.00*** - 0.57 3.33 + 7.48 43.40*** -Leaching (L) 1 3148.75 144.20*** + 1.22 7.10* + 0.00 0.02 C x S 2 35.04 1.61 1.13 6.57** 0.32 1.83 C x M 2 5.83 0.27 1.30 7.60** 0.01 0.06 C x L 2 64.58 2.96 0.09 0.53 0.08 0.49 Residual 36 21.83 0.17 0.17 NOTES: * Significant at 5% level ** Significant at 1% level *** Significant at 0.1% level + means weight losses greater with ethylene oxide, higher moisture content and leaching, than with wet heat, lower moisture content or non-leaching respectively; - means opposite to +. Sofedutf from chip icretn CHI OTTJ rjJTJ fTTD LTJIJ LLLD LLUJ tTTn Bffl B l M BH Sowtfusf ond borh ^T~~, Bolttr plant Pulp KreenfA F^Z7> J i Wood chipper Oisinttgrofor for over»iz« chip* | t JIv 5|y §ld Pylp chvtlt I 1 fc r » «ntd pulp j . igc3__J__l RottMMtor- f Pulp jthicktner DischOfQing rock Trun—mg towt Sler>9< Figure 1. Production of thermomechanical pulp.for hardboard according to the Asplund method (Defibrator Bulletin) (88). 1 2 3 "87 4 ovendrying ovendrying ovendrying N o - l e a c h i n g l e a c h i n g 2 weeks l e a c h i n g 2 weeks l e a c h i n g 2 weeks ovendrying ovendrying ovendrying ovendrying vacuum, 1 h r ; soak,overnight vacuum, 1 h r ; soak,overnight vacuum, 1 h r ; soak,overnight vacuum, 1 h r ; soak, o v e r n i g h t v e n t i l a t e t o 20% M . C . a u t o c l a v e 1 2 1 ° C 30 m i n . v e n t i l a t e to 20% M . C . autoc lave 1 2 1 ° C 30 m i n . v e n t i l a t e to 20% M . C . a u t o c l a v e 121°C 30 min. v e n t i l a t e to 20% M . C . e t h y l e n e o x i d e 2 5 ° C p l a n t i n g p l a n t i n g v e n t i l a t e to 8% M . C . v e n t i l a t e to 8% M . C . p l a n t i n g p l a n t i n g Note: Double frame i n d i c a t e s p o i n t s of no t a b l e d i f f e r e n c e s among trea t m e n t s . F i g u r e 2. Sample p r e c o n d i t i o n i n g procedure f o r i n c u b a t i o n . 88 CAPTIONS F i g , 3 Bar diagram o f average weight l o s s values showing the e f f e c t s of l e a c h i n g , i n i t i a l moisture c o n t e n t , and method of s t e r i l i z a t i o n on the decay of non-brominated and brominated hardboard by brown-rot and white-ret f u n g i . (NB = non-brominated, B = brominated, NL = non-leached, L = leached, S = wet-heat s t e r i l i z a t i o n , EO = et h y l e n e oxide s t e r i l i z a t i o n , MH = i n i t i a l moisture content 20%, HL = i n i t i a l moisture content 8% ). F i g s . 4 through 14 : Decay by v a r i o u s f u n g i of hardboard b l o c k s made o f : f i b e r o nly, non-brominated (1) and i t s brominated c o u n t e r p a r t (4) ; f i b e r p l u s 1% p h e n o l i c r e s i n and 0.30% wax, ncn-brcminated (2) and i t s brominated c o u n t e r p a r t (5); f i b e r plus 1% po l y e t h y l e n i m i n e r e s i n and 0.3031 wax, non-brominated (3) and i t s brominated c o u n t e r p a r t (6); non-leached (NI) and leached (L) ; s t e r i l i z a t i o n by wet-heat (S) and e t h y l e n e oxide (EO); i n i t i a l moisture content 20% (H) and 8% (L) , using the s o i l - j a r technique and mite-proof l i d s . 89 • BROWN -ROT FUNGI, WHITE -ROT FUNGI BROWN -ROT FUNGI WHITE -ROT FUNGI NB B NB B NB B NB BROWN — ROT FUNGI WHITE -ROT FUNGI NB B NB B 1 1 NL—S—MH L-S-MH N L-S-MH L-S-MH EFFECT OF LEACHING NL-S-MH ] L-S-MH NL-S-MH L-S-MH L-S-MH L-S-ML L-S-MH| L-S-ML 1 EFFECT OF MOISTURE CONTENT ? L-S-MH L-S-ML L-S-MH L-S-ML L-EO-ML L-S-ML L-EO-ML L-S-ML EFFECT OF STERILIZATION METHOD ?L-EO-ML L-S-ML L-EO-ML L-S-ML 1 0 2 0 3 0 4 0 5 0 W E I G H T L O S S ( % ) 6 0 7 0 F i g u r e 3. Bar diagram shewing decay a f f e c t e d by d i f f e r e n t f a c t o r s . F i g . 4. Comparison to show the e f f e c t s of bromination and l e a c h i n g on decay by Poria incrassata . F i g . 5. Comparison to show e f f e c t of board composition on decay by Poria incrassata growing on non-brominated and non-leached boards. Fig. 6. Comparison to show effect of board composition on decay by Poria incrassata growing on brominated and non-leached boards. F i g . 7. Comparison to show e f f e c t of board composition and l e a c h i n g on decay by Poria incrassata growing on non-brominated boards. F i g . 8. Comparison to show e f f e c t of board composition and l e a c h i n g on decay by Poria incrassata growing on brominated boards. F i g . 9. Comparison to show e f f e c t of bromination on decay by Polyporus v e r s i c o l o r growing on non-leached boards. F i g . 10. Comparison to show e f f e c t of bromination on decay by Lenzites trabea growing on leached boards. F i g . 11. Comparison to show e f f e c t of bromination on decay by Polyporus adustus growing on leached boards. 95 F i g . 12. Comparison to show e f f e c t of l e a c h i n g on decay by Coniophora puteara growing on brominated boards. 9 6 Comparison to show e f f e c t of i n i t i a l m oisture content of blocks on decay by Poria montioola growing on leached and brominated boards. 

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