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Microwave drying of resin impregnated paper Minami, Shusuke 1970

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MICROWAVE DRYING OF RESIN IMPREGNATED PAPER by SHUSUKE MINAMI B. Eng., Hiroshima U n i v e r s i t y , 1961 A THESIS SUBMITTED IN PARTIAL FULFILMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF APPLIED SCIENCE i n the Department of CHEMICAL ENGINEERING We accept t h i s t h e s i s as conforming t o the r e q u i r e d standard THE UNIVERSITY OF BRITISH COLUMBIA February., 1970 In p r e s e n t i n g t h i s t h e s i s i n p a r t i a l f u l f i l m e n t o f t h e r e q u i r e m e n t s f o r an a d v a n c e d d e g r e e a t 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 , I a g r e e t h a t t h e 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 a g r e e t h a ^ 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 Depar tment o r by h i s r e p r e s e n t a t i v e s . I t i s u n d e r s t o o d t h a t 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 . Depar tment o f 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 V a n c o u v e r 8, Canada Date fif*/3, i ABSTRACT. A p i l o t s c a l e machine was designed and c o n s t r u c t e d to allow study of the continuous microwave d r y i n g at 2 .45 GHz of paper impregnated with water or with phenol formaldehyde r e s i n . T h i s equipment c o u l d d e l i v e r microwave power at l e v e l s up 2 . 9 0 KW. Resin impregnated paper d r i e d by microwaves showed b e t t e r r e s i n d i s t r i b u t i o n , a b r a s i o n r e s i s t a n c e , and i n t e r n a l bond s t r e n g t h when compared to s i m i l a r papers d r i e d i n a hot a i r n a t u r a l con-v e c t i o n oven. No s i g n i f i c a n t d i f f e r e n c e s i n t e n s i l e s t r e n g t h , s t r e t c h , Young's modulus, or bending s t r e n g t h were observed. A q u a n t i t a t i v e method f o r the d e t e r m i n a t i o n of r e s i n d i s -t r i b u t i o n was d e v i s e d . O v e r a l l e f f i c i e n c i e s f o r the microwave d r y i n g based on power input to the microwave power supply were of the order of 50 to 70%. i i TABLE OF CONTENTS Page ABSTRACT • i LIST OF TABLES. . v LIST OF FIGURES • ••• • v i l ACKNOWLEDGEMENTS '. l x I - INTRODUCTION. . ... 1 I I - REVIEW OF PREVIOUS WORK 4 1 . . D rying Mechanism ^ q 2 . B a s i c s of Microwave D r y i n g ? ~\ f. 3 . R e s i n D i s t r i b u t i p n Measurement I I I - APPARATUS 2 0 20 1 . Process 2 . Paper D r i v i n g System.... 2 0 3 . R e s i n Impregnator 4 . V e n t i l a t i o n System .... 2 6 5 . Surface Thermocouples 2 6 6 . Microwave Generator and Power Supply System 2 8 7 . Microwave A p p l i c a t o r . . . " . . . . . . . 3 0 8 . D i r e c t i o n a l Power Meter.. 3 1 9 . Water Load 3 1 1 0 . S h i e l d i n g and R a d i a t i o n Leakage 3 2 IV - EXPERIMENTAL.. ,. 3 4 1 . Base Paper and Resin 3 4 2 . Start-Up. and Shut-Down of the Microwave Power Supply System 3 4 3 . Procedure f o r Drying Experiments 3 5 i i i Page 4. T e n s i l e S trength Measurement.. 37 5. Paper Bending Test 39 6. I n t e r n a l Bond Test . .. 1 | 1 7. Surface Abrasion T e s t . . . . . . . . . ^3 8. Q u a n t i t a t i v e Resin D i s t r i b u t i o n Measurement ^ a) Pretreatment of Samples..... ^ b) Resin Content A n a l y s i s - S u l f u r i c A c i d Method . 1 + 8 c) Resin Content A n a l y s i s - H y d r o f l u o r i c A c i d Method . 51 V - RESULTS AND DISCUSSION 5^ 1. D r y i n g Experiments 5 4 a) Drying of Paper Wetted with Water 54 b) Drying o f Resin Impregnated Paper 6 l c) Convective D r y i n g E f f e c t 67 2. Product Q u a l i t y Tests '.. 67 - a) Tension Tests 67 b) I n t e r n a l Bond Test . 6 9 c) Surface Abrasion Test 72 d) Paper Bending Test 75 3. R e s i n D i s t r i b u t i o n . . 75 k. Product Appearance , 8 0 VI - CONCLUSIONS...: 8 5 VII - REFERENCES...'. -.- 8 6 V I I I - NOMENCLATURE 8 9 i v Page APPENDIX A Power Meter C a l i b r a t i o n . .. A - 1 APPENDIX B Rotameter C a l i b r a t i o n B - l APPENDIX C Thermocouple C a l i b r a t i o n C" 1 APPENDIX D O r i f i c e Meter D - 1 APPENDIX E Sample C a l c u l a t i o n f o r Heat Balance... E - l L I S T OF TABLES TABLE Page I S u l f u r i c a c i d T r e a t m e n t D a t a f o r Base P a p e r , P u r e R e s i n , and R e s i n I m p r e g n a t e d P a p e r ^ I I H y d r o f l u o r i c A c i d T r e a t m e n t D a t a f o r Base P a p e r , P u r e R e s i n , and R e s i n I m p r e g n a t e d P a p e r 5 2 I I I D r y i n g D a t a f o r Wet P a p e r 5 5 IV A p p l i c a t o r E f f i c i e n c y f o r Wet P a p e r D r y i n g 5 6 V D r y i n g D a t a f o r R e s i n I m p r e g n a t e d P a p e r 6 2 VI A p p l i c a t o r E f f i c i e n c y f o r R e s i n I m p r e g n a t e d P a p e r D r y i n g 6 3 V I I C o n v e c t i v e E f f e c t o f V e n t i l a t i o n A i r 6 8 V I I I T e n s i o n T e s t D a t a ( T e n s i l e B r e a k i n g S t r e n g t h ) 7 0 IX T e n s i o n T e s t D a t a ( S t r e t c h ) 7 0 X T e n s i o n T e s t D a t a (Young's M o d u l u s ) 7 1 XI I n t e r n a l Bond T e s t D a t a 7 3 X I I S u r f a c e A b r a s i o n T e s t D a t a 7 3 X I I I P a p e r B e n d i n g T e s t D a t a 7 6 XIV R e s i n C o n t e n t D i s t r i b u t i o n 7 7 XV R e s i n P i c k - u p o f M i c r o w a v e D r i e d P r o d u c t s 7 8 APPENDIX A - l a Power M e t e r C a l i b r a t i o n D a t a (Low Range) A - 8 A - l b Power M e t e r C a l i b r a t i o n D a t a ( H i g h Range) A - 9 A - 2 a S t a r t - u p Time f o r Microwave G e n e r a t o r ( V a r i a c S e t t i n g i n H i g h Range : 7 5 ) A - 1 0 A - 2 b S t a r t - u p Time f o r M i c r o w a v e G e n e r a t o r ( V a r i a c S e t t i n g i n H i g h Range : 1 3 0 ) A - 1 0 A - 2 c S t a r t - u p Time f o r M i c r o w a v e G e n e r a t o r ( V a r i a c S e t t i n g i n Low Range : 7 0 ) A - l l V I Page B - l Rotameter C a l i b r a t i o n Data B_2 C - l S u r f a c e Thermocouple C a l i b r a t i o n Data C-2 C-2 Thermocouple C a l i b r a t i o n Data C-2 v i i LIST OF FIGURES F i g u r e Page 1 Plane-wave T r a n s m i s s i o n i n t o L o s s y M a t e r i a l 12 2 Flow Sheet o f Apparatus 21 3 Assembly Drawing o f Apparatus 22 4 Photographs o f Apparatus 23&24 5 S u r f a c e Thermocouple 27 6 A s s e m b l i n g o f S u r f a c e Thermocouples 27 7 W i r i n g Diagram o f Power Supply System 29 8 Load - E l o n g a t i o n Curve . 38 9 Paper Bending T e s t e r ' 40 10 M e t a l B l o c k s f o r I n t e r n a l Bond Test 42 11 Aluminium D i s c f o r S e c t i o n i n g 45 12 E x p e r i m e n t a l Set-up o f S e c t i o n i n g 45 13 D r y i n g Curves f o r Base Paper 47 14 D r y i n g Curves f o r R e s i n 49 15 D r y i n g Curves f o r R e s i n Impregnated Paper 50 16 M o i s t u r e Content v e r s u s Power G e n e r a t i o n ( D r y i n g o f Water Wetted Paper) 58 17 R e l a t i v e M o i s t u r e Content v e r s u s Power G e n e r a t i o n ( D r y i n g o f Water Wetted Paper) 59 18 Absorbed Energy v e r s u s P o s i t i o n ( D r y i n g o f Water Wetted Paper) 60 19 R e l a t i v e M o i s t u r e Content v e r s u s Power G e n e r a t i o n ( D r y i n g o f R e s i n Impregnated Paper) 64 20 Absorbed Energy v e r s u s P o s i t i o n ( D r y i n g o f R e s i n Impregnated Paper) 65 21 S u r f a c e A b r a s i o n Rate v e r s u s A b r a s i o n C y c l e s 74 22 R e s i n Content D i s t r i b u t i o n 79 23 Photographs o f R e s i n Impregnated Papers 82 V I 1 1 APPENDIX . Page A - l Power G e n e r a t i o n v e r s u s Power M e t e r R e a d i n g k-2 Power G e n e r a t i o n v e r s u s S u p p l y C u r r e n t A - 3 Power G e n e r a t i o n v e r s u s V a r i a c S e t t i n g . A - 4 Power S u p p l y E f f i c i e n c y v e r s u s Power A _ g G e n e r a t i o n A -5 S t a r t - u p Time f o r M i c r o w a v e G e n e r a t o r A - 7 B - l R o t a m e t e r C a l i b r a t i o n C u r v e B _2 i x ACKNOWLEDGMENT I w i s h t o t h a n k Dr. R. B r a n i o n , u n d e r whose d i r e c t i o n t h i s s t u d y was c o n d u c t e d , f o r h i s g u i d a n c e and encoura g e m e n t t h r o u g h -out t h i s work. I a l s o w i s h t o t h a n k Dr. W.A.G. Vo s s ( D e p a r t m e n t o f E l e c t r i -c a l E n g i n e e r i n g , t h e U n i v e r s i t y o f A l b e r t a ) f o r h i s c o n s u l t a t i o n and g u i d a n c e i n t h e c o n s t r u c t i o n and o p e r a t i o n o f t h e a p p a r a t u s . S i n c e r e a p p r e c i a t i o n i s due t o R e i c h h o l d C h e m i c a l s (Canada) L i m i t e d , and Dr. R.C. V a s i s h t h , i t s R e s e a r c h D i r e c t o r , f o r t h e i r h e l p i n many p h a s e s o f t h i s work. P a r t i c u l a r l y , I w i s h t o t h a n k Mr. K. T a k a h a s h i , n o t o n l y f o r h i s t e c h n i c a l a d v i c e , b u t a l s o f o r h i s encoura g e m e n t i n p r i v a t e l i f e . T hanks a r e a l s o due t o t h e F a c u l t y o f F o r e s t r y o f 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 use o f t h e i r f a c i l i t i e s , and t h e work shop o f t h e C h e m i c a l E n g i n e e r i n g Department f o r t h e i r c o n s t r u c t i o n o f t h e a p p a r a t u s . P a r t i c u l a r l y , I w i s h t o t h a n k Mr. E. Szabo who was i n c h a r g e o f t h e e l e c t r i c a l p a r t o f t h i s a p p a r a t u s . I am i n d e b t e d t o t h e N a t i o n a l R e s e a r c h C o u n c i l o f Canada and t h e C h e m i c a l E n g i n e e r i n g Department o f 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 f i n a n c i a l s u p p o r t . 1 I - INTRODUCTION Recently the application of microwave power to I n d u s t r i a l heating and drying processes has become economically feasible i n certain industries and i s approaching economic f e a s i b i l i t y i n others. This r e s u l t s from the development of high e f f i c i e n c y and high power microwave generators of improved s t a b i l i t y . These generators are available at much lower unit costs re-l a t i v e to e a r l i e r designs. The advantages that microwave heating and drying have over conventional heating and drying arise from the fact that micro-waves penetrate i n s t a n t l y to a s i g n i f i c a n t depth i n the material being heated and generate heat i n t h i s material throughout the volume which has been penetrated. In conventional heating and drying methods heat i s transferred into the material being dried from the suface into the bulk of the material. Heat i s f i r s t transferred to the surface by conduction, convection or radiation. In such a process the highest temperatures are at the surface and a temperature gradient within the material i s unavoidable. The conduction process which transfers heat into the material i s r e l a t i v e l y slow. To speed up t h i s process more severe conditions may be applied to the surface, e.g. increased a i r temperatures i n hot a i r drying, increased platen temperatures i n conduction heating, or increased radiation in t e n s i t y i n radiant heating. These more severe conditions may damage the surface and cause product defects such as surface cracks. In microwave heating the heat i s generated i n t e r n a l l y , thus the surface conditions are no more severe than those i n -side the bulk of the material. In fact the surface temperature 2 i s u s u a l l y the lowest. Depending on the a b s o r p t i v e c h a r a c t e r -i s t i c s of the m a t e r i a l being heated a l e s s steep temperature grad i e n t may be e s t a b l i s h e d . Another f e a t u r e of microwave h e a t i n g which i s p a r t i c u l a r l y important i n d r y i n g i s s e l e c t i v e h e a t i n g of water. Water mole-c u l e s because of t h e i r h i g h l y p o l a r s t r u c t u r e are able to s t r o n g l y absorb microwave energy. Thus i n the d r y i n g of paper, water' absorbs microwave energy and i s heated but c e l l u l o s e i s more or l e s s t r a n s p a r e n t to microwaves and thus does not absorb much energy from them. In an i n d u s t r i a l l a m i n a t i n g o p e r a t i o n such as plywood manufacture the glue l a y e r s c o u l d be heated up w i t h -out having to heat up the bulk of the wood because the wood can transmit. much of the microwave r a d i a t i o n . T h i s s e l e c t i v e h e a t i n g e f f e c t a l s o c o n t r i b u t e s to a s o r t of s e l f r e g u l a t i o n of h e a t i n g which i s e s p e c i a l l y important i n a c h i e v i n g a uniform and l e v e l moisture p r o f i l e . Thus micro-waves act upon the wet areas and ignore the dry areas. T h i s c o u l d be of great s i g n i f i c a n c e i n paper manufacture where the l e v e l moisture p r o f i l e s across paper machines, which are necessary to give uniform r e e l s of paper, are achieved by over-d r y i n g most of the sheet to remove the wettest s t r e a k s . T h i s study i s concerned with u s i n g microwave energy i n an attempt to improve the p r o p e r t i e s of p h e n o l i c r e s i n impregnated paper by microwave d r y i n g . At present t h i s m a t e r i a l i s d r i e d i n a c onventionalyhot gas,forced c o n v e c t i o n oven. Convention-, a l l y d r i e d r e s i n impregnated paper has a tendency to be r a t h e r b r i t t l e . When these papers are used as;,overlays f o r plywood, p a r t i c l e board e t c . e x c e s s i v e f l e x i n g of the underlay m a t e r i a l may cause cracks i n the o v e r l a y . T h i s has been a t t r i b u t e d to an uneven r e s i n d i s t r i b u t i o n which i s b e l i e v e d to be caused by r e s i n m i g r a t i o n d u r i n g d r y i n g i n the f o r c e d c o n v e c t i o n d r y i n g process. Heat i s applied, to the s u r f a c e causing the water suspending the r e s i n emulsion to evaporate. . To leave the sheet t h i s water migrates to the s u r f a c e and c a r r i e s with i t r e s i n molecules which polymerize f a s t e r at the s u r f a c e than i n the i n t e r i o r due to the higher temperature. T h i s h i g h l y polymerized r e s i n cannot d i f f u s e back i n t o the sheet and hence the i n t e r i o r of the sheet tends t o have a lower r e s i n r content than the s u r f a c e . In microwave d r i e d paper the h o t t e s t l o c a t i o n i s at the centre o f the sheet and thus p o l y m e r i z a t i o n would be most r a p i d t h e r e . T h i s would counteract the tendency to move toward the s u r f a c e with the e v a p o r a t i n g water because the r e s i n molecules would, on a t t a i n i n g a c e r t a i n degree of p o l y m e r i z a t i o n , drop out of suspension. T h i s a n a l y s i s would seem to be v a l i d d u r i n g the constant r a t e p e r i o d of d r y i n g and the f i r s t f a l l i n g r a t e p e r i o d . There i s a l s o a certain advantage i n microwave d r y i n g d u r i n g the f a l l i n g r a t e p e r i o d s i n that the c e l l u l o s e does not have to be heated up i n order to evaporate the water because the heat i s s e l e c t i v e l y generated i n the water. In t h i s study phenol-formaldehyde impregnated paper i s d r i e d u s i n g a 2.5 kw meanderline, microwave d r i e r under v a r i o u s c o n d i t i o n s . The q u a l i t y of t h i s product i s compared with the q u a l i t y of f o r c e d c o n v e c t i o n d r i e d papers produced commercially and i n the l a b o r a t o r y . Some u s e f u l data f o r the microwave d r y i n g process i s a l s o obtained. 4 I I - REVIEW OF PREVIOUS. WORK . 1. D r y i n g Mechanism ( 1 2 ) E a r l y w o r k e r s 5 i n t h e f i e l d o f d r y i n g d i v i d e d t h e d r y i n g p r o c e s s i n t o two s t a g e s , t h e c o n s t a n t r a t e s t a g e , w h e r e i n t h e r a t e o f e v a p o r a t i o n i s c o n s t a n t , and t h e f a l l i n g r a t e s t a g e i n w h i c h t h e r a t e o f e v a p o r a t i o n d e c r e a s e s w i t h d e c r e a s i n g m o i s t u r e c o n t e n t . The c o n s t a n t r a t e p e r i o d was, and i s s t i l l , b e l i e v e d t o be e v a p o r a t i o n f r o m a c o n t i n u o u s , u n b r o k e n f i l m o f w a t e r on t h e s u r f a c e o f t h e m a t e r i a l b e i n g d r i e d . When s u f f i c i e n t w a t e r has been e v a p o r a t e d d r y s o l i d b r e a k s t h r o u g h t h i s s u r f a c e f i l m ; t h e r a t e o f d r y i n g d e c r e a s e s ; t h i s i s t h e f a l l -i n g r a t e p e r i o d . . I n t h i s e a r l y work i t was p r o p o s e d t h a t w a t e r moves by d i f f u s i o n f r o m t h e i n t e r i o r o f t h e s o l i d t o t h e s u r f a c e and t h a t as more and more w a t e r i s e v a p o r a t e d t h i s d i f f u s i o n e n c o u n t e r s more and more r e s i s t a n c e . • (3) I n 1937 C e a g l s k e and Hougen v ' f o u n d t h a t t h e m o i s t u r e p r o f i l e w h i c h t h e y measured d i d n o t f i t t h e p r o f i l e t h a t t h e y c a l c u l a t e d on t h e b a s i s o f a d i f f u s i o n mechanism when d r y i n g beds o f s a n d . They e x p l a i n e d t h e s e r e s u l t s by i n t r o d u c i n g a c a p i l l a r y f l o w mechanism as o p p o s e d t o a d i f f u s i o n mechanism f o r t h e movement o f w a t e r . Thus w a t e r was assumed t o move f r o m t h e i n t e r i o r o f t h e s o l i d t o t h e s u r f a c e u n d e r t h e i n f l u e n c e o f s u r f a c e t e n s i o n f o r c e s i n the c a p i l l a r i e s . (4) C o r b e n and N e w i t t p r o p o s e d i n 1955 a t h e o r y o f d r y i n g b a s e d on a s e r i e s o f s t u d i e s on p o r o u s and n o n - p o r o u s m a t e r i a l s . U s i n g t h e c a p i l l a r y t h e o r y , mechanisms were p u t f o r w a r d f o r t h e c o n s t a n t r a t e p e r i o d and t h e f i r s t and s e c o n d f a l l i n g r a t e p e r i o d s . D u r i n g t h e c o n s t a n t r a t e p e r i o d s u r f a c e w a t e r i s e v a p o r a t e d ; 5 t h i s i s t h e f i r s t w a t e r t o be removed i n most d r y i n g p r o c e s s e s . F u r t h e r d r y i n g e x p o s e s t h e p o r e s i n t h e m a t e r i a l . T hese p o r e s l e a d i n t o t h e i n t e r i o r o f t h e s o l i d . At t h e i r mouths p e n d u l a r r i n g s o f w a t e r a r e p r e s e n t . When a l l t h e s e e x t e r n a l p o r e s a r e e x p o s e d and o n l y p e n d u l a r w a t e r r i n g s r e m a i n on t h e s u r f a c e t h e r i n g s s t a r t t o c o n t r a c t c a u s i n g more o f t h e p o r e s t o be opened. As t h e p e n d u l a r r i n g s c o n t r a c t i n c r e a s i n g l y n a r r o w p o r e s a r e e x p o s e d l e a d i n g t o g r e a t e r c a p i l l a r y s u c t i o n s . E v e n - " t u a l l y a s t a g e w i l l be r e a c h e d when t h e p e n d u l a r r i n g s a r e i n -c a p a b l e o f t r a n s f e r r i n g s u f f i c i e n t w a t e r t o t h e s u r f a c e f r o m t h e i n t e r i o r t o r e p l a c e t h a t w h i c h has been e v a p o r a t e d . Here t h e c o n s t a n t r a t e p e r i o d ends and t h e f a l l i n g r a t e p e r i o d b e g i n s . When w a t e r c a n no l o n g e r be removed by t h e m e n i s c u s r e c e d i n g i n t o s m a l l e r p o r e s f u r t h e r e v a p o r a t i o n o c c u r s by d i f f u s i o n o f w a t e r out o f t h e s o l i d . T h i s i s t h e s e c o n d f a l l -i n g r a t e p e r i o d . B o t h c a p i l l a r y and d i f f u s i o n mechanisms may o c c u r s i m u l t a n e o u s l y i n some m a t e r i a l s . The k i n d o f m a t e r i a l d e t e r m i n e s w h e t h e r c a p i l l a r y e f f e c t s o r d i f f u s i o n c o n t r o l t h e r a t e o f m o i s t u r e e v a p o r a t i o n . I n p o r o u s m a t e r i a l s c a p i l l a r y s u c t i o n i s most i m p o r t a n t ( e . g . beds o f s a n d ) , whereas i n n o n - p o r o u s m a t e r i a l s ( e . g . g e l a t i n e and o t h e r f o o d s ) d i f f u s i o n c o n t r o l s . I n o t h e r s i t u a t i o n s t h e d r y i n g e quipment has an i n f l u e n c e on t h e mechanism by w h i c h w a t e r i s moved f r o m t h e i n t e r i o r o f t h e s o l i d t o t h e s u r f a c e . I n t h e c o n v e n t i o n a l p a p e r d r y i n g p r o c e s s t h e wet s h e e t i s p r e s s e d a g a i n s t steam h e a t e d c y l i n d e r s . D r e s h f i e l d and H a n w / have r e p o r t e d an e v a p o r a t i o n - c o n d e n s a t i o n mechanism f o r t h i s k i n d o f d r y i n g . I n t h i s mechanism w a t e r i s b e l i e v e d t o e v a p o r a t e a t 6* o r n e a r t h e s u r f a c e where t h e h e a t i s b e i n g s u p p l i e d ; t h a t i s a t t h e s h e e t c y l i n d e r i n t e r f a c e . However, t h i s w a t e r c a n n o t e s c a p e t h r o u g h t h i s s u r f a c e w h i c h i s e f f e c t i v e l y s e a l e d by t h e m e t a l c y l i n d e r . The w a t e r v a p o u r t h e n moves t o t h e o p p o s i t e , c o o l e r s i d e o f t h e s h e e t where i t c o n d e n s e s . The e n e r g y r e -l e a s e d i n c o n d e n s a t i o n t h e n c o n t r i b u t e s t o t h e e n e r g y r e q u i r e d t o v a p o u r i z e w a t e r a t t h e s u r f a c e away f r o m t h e c y l i n d e r . The w a t e r i s s u p p o s e d t o m i g r a t e e i t h e r by d i f f u s i o n o r c a p i l l a r i t y . T h i s e v a p o r a t i o n - c o n d e n s a t i o n mechanism i s most p r o b a b l e when t h e s y s t e m i s s u b j e c t t o l a r g e t e m p e r a t u r e g r a d i e n t s s u c h a s . o c c u r i n d r y i n g by c o n t a c t w i t h a h o t s u r f a c e . A p p l y i n g * (6) t h i s mechanism Harmathy t h e o r e t i c a l l y s i m u l a t e d v a r i o u s d r y i n g p r o c e s s e s and showed t h a t t h e e v a p o r a t i o n - c o n d e n s a t i o n mechanism was t h e g o v e r n i n g mechanism o f d r y i n g d u r i n g t h e f a l l i n g r a t e p e r i o d . (6) Harmathy's p a p e r i s one o f a number o f p a p e r s w h i c h have a p p e a r e d r e c e n t l y and w h i c h a r e m a i n l y c o n c e r n e d w i t h computer (7 V s i m u l a t i o n o f d r y i n g p r o c e s s e s . Kauh has u s e d a n u m e r i c a l s o l u t i o n o f t h e d i f f u s i o n e q u a t i o n i n an a t t e m p t t o p r e d i c t a d r y i n g c u r v e u s i n g a d i f f u s i o n m o i s t u r e movement mechanism. A l t h o u g h a s u c c e s s f u l p r e d i c t i o n was c l a i m e d and good agreement between e x p e r i m e n t a l and c a l c u l a t e d r e s u l t s r e p o r t e d , t h e a p p l i -c a b i l i t y o f . t h i s k i n d o f s o l u t i o n w i l l be l i m i t e d s i n c e t h e d i f f u s i o n mechanism i s n o t a l w a y s t h e g o v e r n i n g one. F o r h o t s u r f a c e d r y i n g , s u c h as i s u s e d i n t h e s t e a m c y l i n d e r d r y i n g o f p a p e r , N i s s a n e t a l i ^ ' ^ ' ' ^ have n u m e r i c -a l l y s o l v e d t h e F o u r i e r h e a t c o n d u c t i o n e q u a t i o n t o g e t t h e t e m p e r a t u r e p r o f i l e i n p a p e r and i t s d r y i n g r a t e c u r v e . They assumed c o n d u c t i v e h e a t t r a n s f e r t h r o u g h t h e s h e e t and e v a p o r a t i o n 7 from the s i d e of the paper o p p o s i t e the c y l i n d e r - The tem-pe r a t u r e p r o f i l e was c a l c u l a t e d assuming a u n i f o r m m o i s t u r e content p r o f i l e . In Nissan's work the o p e r a t i o n of the d r y e r was d i v i d e d i n t o f o u r phases; 1) where the paper sheet f i r s t c o n t a c t s the c y l i n d e r ; 2) where the paper i s c o n t a c t i n g the c y l i n d e r and i s covered by the f e l t ; 3) where the sheet i s a g a i n exposed on one s i d e and 4) where the paper sheet i s between c y l i n d e r s . The f o l l o w i n g e q u a t i o n was s o l v e d 3 2T 1 3T 3x z a 30 D i f f e r e n t boundary c o n d i t i o n s a p p r o p r i a t e to t h e . v a r i o u s r e g i o n s were used. These were I n i t i a l c o n d i t i o n T = f ( x ) f o r 0 = 0 Phase 1 and 3 I *1) =;,_ HiX ( T _ T j V 3r ) r = 0 k \ 1 c xr=o' /3T \ = _ H2X ( - T ) - 4 - 6 5 H 2 X ( Y l - y )T, V 3 r / _ k 1 r=i a ; k K y 1 y a ; i b r= 1 Phase 2 /3T\ = _ H i X ( _ v V3r ) k v c 1 r = o J \ ' r = 0 dvJ k ^ r = i f' k v y i y f ; b r= 1 8 Phase 4 (f) HiX k (T - T ) a r = o H'.65HiX k r=o H 2X (T - T ) r=i a 4.65H 2X k k Comparing t h e i r n u m e r i c a l s o l u t i o n s w i t h e x p e r i m e n t a l measurements they concluded t h a t heat was indeed t r a n s f e r r e d through the sheet by c o n d u c t i o n alone i f the c y l i n d e r temperature was below the b o i l i n g p o i n t of water. They noted t h a t c o n v e c t i v e heat t r a n s f e r became of i n c r e a s i n g importance as the temperature r o s e . T h i s suggested the presence of an evaporation-conden-s a t i o n mechanism^''"^. (12) Snowv improved upon t h i s k i n d of a n a l y s i s by n u m e r i c a l l y solving the heat and mass t r a n s f e r equations s i m u l t a n e o u s l y . In h i s work he added a term to the heat c o n d u c t i o n e q u a t i o n to a l l o w f o r the e v a p o r a t i o n - c o n d e n s a t i o n mechanism. He s o l v e d The f i r s t term on the r i g h t hand s i d e r e p r e s e n t s conductive heat t r a n s f e r and the second r e p r e s e n t s e v a p o r a t i o n - c o n d e n s a t i o n heat t r a n s f e r . The a p p r o p r i a t e mass t r a n s f e r e q u a t i o n used was In t h i s e q u a t i o n the f i r s t term on the r i g h t hand s i d e r e -p r e s e n t s the r a t e of flow of l i q u i d water by c a p i l l a r y a c t i o n . Ps(M) i s the c a p i l l a r y s u c t i o n e x e r t e d on l i q u i d water by the 9 capi l laries in the paper having moisture content M. kq(M) represents the conductance of the paper for l iquid water. This term was determined empirically. The second -te'ra on the right hand side represents the rate of flow of water vapour which contributes to the evaporation-condensation heat and mass transfer. K r is calculated from the theory of molecular diffusion of water in a i r . Although the solutions of these equations rely on empirically determined coefficients which no doubt vary from material to material, Snows* analysis seems to give good results and his method should be tested on a wider range of materials. 2. Basics of Microwave Drying There have not been many papers published on the subject of microwave drying and even fewer on the microwave drying of paper. Most of the latter are concerned with the economic feas ib i l i ty of introducing microwave drying into papermaking. A number of papers have appeared which are concerned with the experimental determination of the die lectr ic properties of the material to be dried. Because of the.internal heat generation in the material being dried by microwave techniques the drying mechanism may be different than that found in conventional drying. However, as far as is known no research has been done on the mechanism . of moisture removal in microwave drying. (13) Goerz and Jol ly have done an economic feas ib i l i ty analy-sis on the use of a meanderline waveguide drier for instal lat ion on a conventional paper machine. They predicted significant (14)" savings but this conclusion has been cr i t i c i zed by Gardner 10 who q u e s t i o n s t h e c o s t f i g u r e s t h e y a s s i g n e d t o c o n v e n t i o n a l d r y i n g . T h e a d v a n t a g e s c i t e d b y G o e r z a n d J o l l y i n c l u d e a m o r e u n i f o r m m o i s t u r e p r o f i l e , a h i g h e r o v e r a l l m o i s t u r e c o n t e n t , a n d a s u b s t a n t i a l l y r e d u c e d d r i e r l e n g t h . D a m s k e y , H a n k i n a n d S t e p h a n s e n v J ' h a v e p r e s e n t e d a n o t h e r e c o n o m i c a n a l y s i s o f m i c r o w a v e a p p l i c a t i o n t o c o n v e n t i o n a l p a p e r -m a k i n g b y u s i n g c o m p u t e r s i m u l a t i o n t e c h n i q u e s . I n t h e i r w o r k t h e y c o m p u t e d t h e r e l a t i v e p r o f i t a b i l i t y o f u s i n g m i c r o w a v e e q u i p m e n t o v e r c o n v e n t i o n a l e q u i p m e n t i n p a p e r m a k i n g a n d p a p e r c o a t i n g . T h e f o l l o w i n g a s s u m p t i o n s w e r e m a d e : - 1 ) m i c r o w a v e d r y i n g p r o d u c e s a l e v e l m o i s t u r e p r o f i l e w i t h a h i g h e r a v e r a g e m o i s t u r e c o n t e n t ; 2 ) t h e i n c r e a s e d d r y i n g c a p a c i t y p r o v i d e d b y m i c r o w a v e m e t h o d s p e r m i t s h i g h e r p a p e r m a c h i n e o r c o a t i n g m a c h i n e s p e e d s . T h e i r e c o n o m i c m o d e l i n d i c a t e s a b e t t e r r e t u r n o n i n v e s t e d c a p i t a l f o r m i c r o w a v e d r y i n g o v e r c o n v e n t i o n a l d r y -i n g . M o r e e x p e r i m e n t a l d a t a i s n e c e s s a r y i n a n a c c e s s i b l e f o r m b e f o r e o n e c o u l d c o m p e t e n t l y d e s i g n o r s e l e c t a m i c r o w a v e d r i e r f o r p a p e r m a n u f a c t u r e . ~ M i c r o w a v e d r i e r s o r h e a t e r s e m p l o y h i g h f r e q u e n c y e n e r g y i n t h e r a n g e 3 0 0 MHz t o 30GHz ( 3 0 0 x 1 0 6 c y c l e s / s e c . t o 30 x 1 0 ^ c y c l e s / s e c ) . I n o r d e r t o p r e v e n t i n t e r f e r e n c e w i t h m i c r o w a v e c o m m u n i c a t i o n s s y s t e m s t h e f o l l o w i n g f r e q u e n c i e s h a v e b e e n a s s i g n e d : f o r i n d u s t r i a l , m e d i c a l , a n d s c i e n t i f i c u s e . F r e q u e n c y Wave L e n g t h MHz i n c h e s 8 9 0 - 9^0 . 1 3 . 0 2 4 0 0 - 2500 4.9 5 7 2 5 - 5 8 7 5 •: 2.0 2 2 , 0 0 0 - 2 2 , 2 5 0 0.24 I I The choice of frequency depends on s e v e r a l f a c t o r s . I n -d u s t r i a l equipment f o r d r y i n g i s only a v a i l a b l e f o r 915 MHz and 2450 MHz. High f r e q u e n c i e s promote hig h e r power d i s s i p a t i o n but the depth of p e n e t r a t i o n i n t o the m a t e r i a l i s g r e a t e r f o r low f r e q u e n c i e s . In the present work a 2450 MHz generator was used. At microwave frequencies, e l e c t r o m a g n e t i c energy i s ab-sorbed by means of a r e l a x a t i o n phenomenon or d i e l e c t r i c a f t e r e f f e c t . T h i s i s caused by the motion of the d i e l e c t r i c mole-cul e s i n response to an a p p l i e d a l t e r n a t i n g f i e l d . The motion c o n s i s t s of a d i s t o r t i o n of the molecular s t r u c t u r e . Thus the bond angles and i n t e r a t o m i c d i s t a n c e s i n the molecule are d i s -t o r t e d from t h e i r e q u i l i b r i u m p o s i t i o n by the f i e l d . The p o l a r molecules a l s o t r y to a l i g n themselves wi t h the f i e l d . But as the f i e l d d i r e c t i o n i s c o n t i n u a l l y changing the molecules are c o n t i n u a l l y d i s t o r t i n g and r e a l i g n i n g r e s u l t i n g i n energy d i s s i p a t i o n and p r o d u c t i o n of heat. When a microwave i s t r a n s m i t t e d i n t o a d i e l e c t r i c m a t e r i a l the i n c i d e n t power d e n s i t y (Pj_) c a r r i e d by the wave i s r e l a t e d to the e l e c t r i c f i e l d d e n s i t y by P i = — — 2 V where n 0 i s the i n t r i n s i c impedance of f r e e space. At the s u r f a c e . o f a d i e l e c t r i c m a t e r i a l i n a microwave f i e l d some of the i n c i d e n t energy i s r e f l e c t e d back towards the source and the remainder (P^.) Is t r a n s m i t t e d i n t o the m a t e r i a l . A t t e n u a t i o n theory, d e s c r i b e s how the e l e c t r i c f i e l d d e n s i t y i s attenuated i n the d i e l e c t r i c m a t e r i a l . Prom t h i s theory i t can be shown t h a t the power c a r r i e d by the microwaves i s decreased 12 Figure 1. Plane-wave Transmission into Lossy Material 1 3 to — of i t s surface, value i n a distance d where e v d = 1_ 2a = 1.5x10 10 (Trf/Ptana) -1 (cm ) a = attenuation constant of the material e'= d i e l e c t r i c constant f = frequency tan 6 = loss factor e = e' - j e " = e'(1 - j t a n S ) e = complex p e r m i t t i v i t y e"= d i e l e c t r i c loss factor The equation-sdes:cribing the amounts of power absorbed, re-f l e c t e d and transmitted for lossy d i e l e c t r i c s are generally com-plex and d i f f i c u l t to apply because the c h a r a c t e r i s t i c constants e' and tan 6 are temperature dependent. For materials which are th i n enough that the e l e c t r i c f i e l d density (Et) can be assumed to be constant i n them the absorbed power i s obtained from In order to evaluate the power dissipated i n microwave heat-ing or drying processes the d i e l e c t r i c constants' and the loss factor tan6 of the p a r t i c u l a r material at the p a r t i c u l a r frequency being used must be known. These values as well as being temperature dependent are also composition dependent. In P = 5 5 . 6 xlO _ l i |E. 2fe'tan<5 (watts/cm ) 14 d r y i n g one- o f t h e components i s w a t e r w h i c h has a r e l a t i v e l y l a r g e l o s s f a c t o r , t h u s the e' and t a n 6 f a c t o r s o f the wet m a t e r i a l depend on t h e m o i s t u r e c o n t e n t . Some e m p i r i c a l r e l a t i o n s f o r t h e s e p a r a m e t e r s have,been (16) r e p o r t e d . Voss a f t e r p r o c e s s i n g t h e e x p e r i m e n t a l d a t a o f s e v e r a l w o r k e r s has s u g g e s t e d t h e f o l l o w i n g e q u a t i o n s r e l a t i n g t h e d i e l e c t r i c c o n s t a n t and t h e l o s s f a c t o r f o r w a t e r t o tem-p e r a t u r e and f r e q u e n c y TtanS = 1 . 8 2 x l 0 " 9 f - 1.2 w £^ = 55 ± 10 % a t 9 - 10 GHz £ ' = 8 7 - 0.36T a t 2 - 3 GHz (T=temperature °K) (17) L e w i n has p r e s e n t e d t h e f o l l o w i n g e q u a t i o n t o d e s c r i b e t h e d i e l e c t r i c b e h a v i o u r o f a compound m a t e r i a l . T h i s e q u a t i o n r e s t s on a s e m i - t h e o r e t i c a l b a s i s e = e' - je" = ei-[ 1 + ?L £2 + 2 e i _ p £2 - e i £ i = complex p e r m i t t i v i t y o f component 1 ( d r y s o l i d ) £2 = complex p e r m i t t i v i t y o f component 2 ( w a t e r ) p = _-w P l P2 P i w = d e n s i t y o f component 2 = d e n s i t y o f component 1 = mass r a t i o o f component 2 t o component 1 15 S u b s t i t u t i n g G i = e i - J e " and , r e a r r a n g i n g and c o l l e c t i n g r e a l and I m a g i n a r y p a r t s g i v e s t h e d i e l e c t r i c c o n s t a n t e 1 and the l o s s f a c t o r e" o f the wet m a t e r i a l as e » = (1-F)(1+2F)( e ^ 2 + £ ^ 2 ) + ( 4 + F + 4 F 2 ) e k i + 2 ( l - F ) ( 2 + F ) £ l 2 {eHl-F)+e 1(2+F)} i^-(F-l)2 e»2 „ = 9Fe 2e' 2'  { e ^ ( l - F ) + £ l ( 2 + F ) } ^ _ ( P _ i ) ^ e ^ 2 e"= The a p p l i c a t i o n o f Lewin's e q u a t i o n s t o m i x t u r e s has not been (l8) c o m p l e t e l y s u c c e s s f u l . I n Lewin's a n a l y s i s i t was assumed t h a t the two components were s i m p l y mixed w i t h o u t i n t e r a c t i o n . But i n many m a t e r i a l s such as c e l l u l o s e , w ater m o l e c u l e s are a c t u a l l y bonded t o t h e s o l i d s by f o r example, hydrogen bonds. These b i n d i n g f o r c e s a f f e c t the d i e l e c t r i c l o s s b e h a v i o u r . (19) Asami has d e v e l o p e d an e m p i r i c a l e x p r e s s i o n f o r the d i e l e c t r i c p e r m i t t i v i t y o f m i x t u r e s when bondi n g a f f e c t s a r e pre-s e n t . I n h i s e q u a t i o n s an e m p i r i c a l c o n s t a n t n i s i n t r o d u c e d which r e p r e s e n t s t h e m i x i n g c o n d i t i o n . H i s e q u a t i o n i s e 16 Voss tasted this equation with some experimental data obtained for wet wood and found good agreement. Although only certain frequencies are allowed for industrial microwave use by law these may not necessarily be the optimum frequencies for a particular drying or heating process since the die lectr ic behavour of materials is frequency dependent. De Loor^2(^V studied frequency effects on the die lectr ic behaviours of heterogeneous systems containing water and related the mechanism of microwave absorption to frequency. It is only recently that experimental data for use in designing pract ical microwave drying and heating processes have become available. For the microwave drying of wood Voss ; measured the die lectr ic constant and loss factor at 9-21 GHz. (21) Similar work at 2.45 GHz was done by Tinga . In the latter work the die lectr ic constants of several kinds of wood were measured as functions of temperature at various moisture contents. (22) Leidigh, Stephansen, and Stolte v A investigated the microwave absorption properties of paper at 2.45 GHz. They presented values of the die lectr ic constant and loss factor as functions of temperature and moisture content. More data is necessary before confident design or assessment of large scale industrial systems is feasible for the non equipment manufacturer. 3. Resin Distribution Measurement It has been postulated that non uniform resin distribution is a contributing factor to some of the defects found in resin im-pregnated papers. : Thus some method of observing or, preferably, • measuring the uniformity of resin distribution is necessary to confirm the postulate. 17 In order to study the resin distribution through the thick-ness of the sheet i t Is necessary to section the sheet somehow. After sectioning the resin distribution may be considered by (24 V one of four methods . . 1) microscopy 2) extraction and analysis 3) auto radiographic analysis 4 ) direct chemical analysis There are several possible ways of sectioning a sheet of paper into layers. These include using a microtome, scotch tape, a sheet sp l i t t er , sandpaper, or a lathe. " The microtome gives too l i t t l e sample; scotch tape w i l l not work on resin im-pregnated paper,neither w i l l the Beloit sheet sp l i t t er ; sand-paper contains phenolic resin which might affect subsequent analysis so we chose to use a lathe. So far the microscopic method for observing resin d i s t r i -(25) bution has not been made quantitative. Crosby and Marton ' have studied the mechanism of resin penetration into laminating papers. They dyed phenolic resins prior to impregnation and then observed the resin distribution after drying the sheet,under a light microscope;embedding i t in a polyamide mounting medium and sectioning by microtome. Dyes should be chosen so that they exert minimal effects on the properties or behaviour of the res in. (23) Takahashi, Vasishth, and Cote v J / have developed a method for ob-serving the resin distribution in a sheet of resin impregnated paper. Their technique involves soaking the dried and cured paper in hydrofluoric acid which dissolves a l l the cellulose leaving 18 behind the r e s i n s k e l e t o n . I t a l s o would leave behind l i g n i n but as the base papers were made from bleached k r a f t pulp the amount of l i g n i n would be s m a l l . T h i s r e s i n s k e l e t o n was then c a r e f u l l y washed, embedded i n a mounting medium and s e c t i o n e d on a microtome. Microphotographs showed the r e s i n d i s t r i b u t i o n and a more uniform d i s t r i b u t i o n was observed with microwave d r i e d papers. E x t r a c t i o n of the r e s i n f o l l o w e d by chemical or p h y s i c a l a n a l y s i s of the r e s i d u e or of the e x t r a c t has been used as a method f o r d e t e r m i n i n g the t o t a l r e s i n content of paper s h e e t s . These c o u l d be adapted to the d e t e r m i n a t i o n of a' r e s i n d i s t r i -b u t i o n i n a sheet a f t e r i t has.been s e c t i o n e d but does not seem t o have been so a p p l i e d p r e v i o u s l y . For p h e n o l i c r e s i n s a v a r i e t y o f s o l v e n t s have been proposed-cyclohexane, n - b u t a n o l , (26) dimethyl-formamide, acetone, or molten naphthol . The samples are weighed be f o r e and a f t e r e x t r a c t i o n and the r e s i n content determined by d i f f e r e n c e g r a v i m e t r i c a l l y . C o l o r i m e t r i c a n a l y s i s of the e x t r a c t c o u l d a l s o be u s e f u l . However, one i s not c e r t a i n of the s o l u b i l i t y of the r e s i n s a f t e r a v a r i e t y of c u r i n g p r o c e s s e s . Another s o r t of e x t r a c t i o n process i s d i s s o l u t i o n of the c e l l u l o s e a f t e r h y d r o l y s i s w i t h a c i d , f i l t e r i n g and weighing the (27) r e s i d u e . S e i f e r t used t h i s approach, m o d i f y i n g the Klason ( 2 8 ) l i g n i n d e t e r m i n a t i o n method '. In h i s method the c e l l u l o s e was d i s s o l v e d i n s u l f u r i c a c i d , and the l i g n i n removed with sodium c h l o r i t e . The r e s i n i s the r e s i d u e which was weighed to g i v e the r e s i n content. T h i s method was confirmed as being reasonably a c c u r a t e i n the present study. 19 Hydrolysis of c e l l u l o s e i n s u l f u r i c acid i s rather slow, the whole' analysis required about two days. E t t l i n g and (29) Adams reported that t h i s kind of analysis could be speeded up using chlorosulfohic acid instead of s u l f u r i c acid. They reported successful r e s u l t s i n measuring the r e s i n content of p a r t i c l e board. However, Berkeley^ 0^ t r i e d this.method and found i t impossible to use for r e s i n impregnated papers as he could not f i l t e r , or centrifuge o f f the residue. In the present work chlorosulfonic acid was t r i e d and abandoned because of i t s violent reaction with the r e s i n . In the present work acid hydrolysis of c e l l u l o s e was brought about, using hydrofluoric acid. In the auto radiographic method radioactive labels are i n -troduced into the r e s i n before impregnation. After drying and curing the sheet i s sectioned and the r e s i n content determined by a Geiger counter or by auto radiography. The method requires some elaborate equipment. The direct chemical method depends on the chemical analysis of a p a r t i c u l a r chemical component of the r e s i n . For example Kjeldahl analysis to get the nitrogen content allows c a l c u l a t i o n of the urea formaldehyde ormelamine formaldehyde r e s i n content. However, as phenolic resins contain only carbon, hydrogen, and oxygen which are pr e c i s e l y the components of c e l l u l o s e t h i s method cannot be used for determining the d i s t r i b u t i o n of t h i s r e s i n . 20 III - APPARATUS For this work a 2-. 5 kw microwave drier-res in impregnator was constructed. A schematic diagram of the equipment is pre-sented in figure 2; an assembly drawing is presented in figure 3 . Figures 4 a to 4 d are photographs of the equipment. 1 . Process Figure 2 provides a flow sheet or outline of the process. Base paper is f i r s t dipped into the resin solution and then drawn through the squeeze ro l lers into the microwave applicator. The paper passes through slots in the waveguide wall into the interior of the waveguide where the microwave energy is absorbed. It then passes out of the f i r s t waveguide and into the second one etc. After the f ina l waveguide the paper passes through the drive ro l l s and either is ripped ..off or is wound on a winder. The waveguides are ventilated to fac i l i ta te the removal of water. The microwave system consists of a microwave generator (magnetron), a meander line (series of U bends) waveguide, a power meter and a water load. The antenna of the magnetron is coupled to the waveguide at the dry paper end of the machine. The water load is coupled to the wet end. Thus the microwaves propagate from the dry end to the wet end. However, the micro-wave-paper flow is not truly counter current but is in a sort of counter current-cross flow combination. 2. Paper Driving System As shown in the assembly drawing (figure. 3 ) the paper driving system consists of a 1 / 4 HP electric motor driving a paper driving ro l l er through a reduction gear and a chain drive. Guide rol lers VENT SYMBOL Figure 2. Flow Sheet of Apparatus AIR DUCT MAGNETRON NO. QUANT. NAME AND REQ'D SPECIFICATION 1 4 MICROWAVE APPLICATOR EW3-WGSC 2 1 POWER METER EW3-DPM3 3 1 WATER LOAD EW3-WL25 4 1 RAW PAPER ROLL 5 1 PRODUCT PAPER ROLL 6 1 DRIVE ROLL 4"0D. Cr PLATED 7 1 PRESS ROLL Z"OD. MS-8 2 SQUEEZE ROLL 3"0D. Cr PLATED 9 3 GUIDE ROLL 4n0D. Cr PLATED 10 18 PILLOW BLOCK 3/4" SHAFT 1 1 1 MOTOR 115V I/4HP 1725 RPM 12 1 REDUCTION GEAR DIMENSIONS— INCHES Figure 3 Assembly Drawing of Apparatus 23 Figure 4 b Back View of Apparatus Figure 4 c S h i e l d i n g of Apparatus Figure 4d Control Panel • • • 25 c a r r y t h e -paper f r o m t h e f e e d r o l l t h r o u g h t h e r e s i n p a n and sq u e e z e r o l l s t o t h e w a v e g u i d e . T h e r e a r e t h r e e s p e e d s a t w h i c h t h e p a p e r c a n p a s s t h r o u g h t h e m a c h i n e . The s p e e d c an be v a r i e d by means o f 3 s p e e d p u l l e y s on t h e motor and on t h e g e a r box. The a v a i l a b l e s p e e d s are'0.354, 0.812, and I.67 m e t e r s / m i n . I n o r d e r t o m a i n t a i n a c o n s t a n t t e n s i o n on t h e p a p e r a s i m p l e s l i p t y p e c l u t c h i s . i n s t a l l e d on t h e p a p e r w i n d i n g r o l l . T h e r e i s a l s o ' p r o v i s i o n f o r a f r i c t i o n b r a k e on t h e f e e d r o l l but i n t h i s work i t was n e v e r n e c e s s a r y t o use i t . A l l t h e g u i d e r o l l e r s were c o n s t r u c t e d o f chromium p l a t e d c o p p e r p i p e (4" O.D. S t a n d a r d Copper P i p e ) ; t h e s q u e e z e r o l l e r s were a l s o c o n s t r u c t e d o f chromium p l a t e d c o p p e r p i p e (3" O.D. S t a n d a r d Copper P i p e ) . 3. R e s i n I m p r e g n a t o r The r e s i n i m p r e g n a t i o n s y s t e m c o n s i s t s o f a r e s i n pan, a d i p p i n g box and two s q u e e z e r o l l s . The r e s i n pan i s 22" x 15" x 10" h i g h ; a n d i s made o f p o l y -v i n y l c h l o r i d e . I t c a n h o l d up t o 4 g a l l o n s ' o f r e s i n s o l u t i o n and has a d r a i n i n t h e b o t t o m f o r r e m o v i n g t h e r e s i n . The d i p p i n g box i s 21" x 13" x 6" h i g h , a g a i n i t i s o f p o l y v i n y l c h l o r i d e . Two 2" p o l y v i n y l c h l o r i d e p i p e s ( c u t i n h a l f ) a r e w e l d e d t o t h e b o t t o m o f t h i s d i p p i n g box. Thus t h e p a p e r i s d r a g g e d u n d e r t h e s u r f a c e o f t h e r e s i n i n t h e r e s i n p a n , o v e r t h e two p i p e s on t h e d i p p i n g box and out o f t h e r e s i n . The d e p t h o f i m m e r s i o n o f t h e p a p e r c a n be a d j u s t e d by l o n g , t h r e a d e d r o d s w h i c h a r e a t t a c h e d t o t h e d i p p i n g box. The d e p t h o f p e n e t r a t i o n a l l o w s some v a r i a t i o n o f t h e i m p r e g n a t i o n t i m e . The i m p r e g n a t e d p a p e r t h e n goes t h r o u g h t h e s q u e e z e r o l l s . These two squeeze r o l l s are c o n s t r u c t e d of 3" o u t s i d e diameter, chrome p l a t e d , copper p i p e s . The pressure a p p l i e d t o the r e s i n impregnated sheet can be v a r i e d by moving weights along l e v e r arms a t t a c h e d t o the movable r o l l . Passage through the squeeze r o l l s makes the r e s i n d i s -t r i b u t i o n more uniform and squeezes excess r e s i n from the paper. The amount of r e s i n p i c k up can be c o n t r o l l e d by a d j u s t i n g the pressure between the squeeze r o l l s . 4. V e n t i l a t i o n System In order to t r a n s f e r mass i n the form of water from the paper being d r i e d i t i s of course necessary to v e n t i l a t e the waveguide.. A l s o i f the water content of the a i r i n the wave-guide i s too high water condenses i n s i d e the waveguide and d r i p s c a using a r c i n g which c o u l d l e a d t o f i r e s . A i r e nters through the s l o t s i n the waveguides and i s sucked out through the v e n t i l a t i o n p o r t s on the waveguide bends by a t u r b i n e type f a n . The flow r a t e of a i r ' i n the exhaust duct can be measured by an o r i f i c e p l a t e i n s t a l l e d i n the duct on the d e l i v e r y s i d e of the f a n . Wet and dry bulb temperatures of the a i r l e a v i n g the waveguide were a l s o measured by a psychro-meter mounted i n the duct on the s u c t i o n s i d e of the fan. 5. Surface Thermocouples A set of thermocouples was c o n s t r u c t e d t o measure the s u r -face temperature of the paper. For such s u r f a c e temperature measurements the thermocouple should be i n good contact with the s u r f a c e and heat l o s s e s from the thermocouple j u n c t i o n should be minimized.- Therefore the thermocouples (40 gauge copper-constantan) were embedded i n 3/4" x 2" x 1/16" s t r i p s of p o l y e t h y l e n e as shown i n f i g u r e 5. Thus the thermocouple j u n c t i o n 27 1/6 <|>x3 BRASS ROD =5s mm -\ao ALUMINIUM BAR lj-xi--22 t n. ij i l l ACRYLIC RESIN BLOCK 30 GAGE COPPER-CONSTANTAN PAPER POLYETHYLENE * SHEET V t -—' t ro|<fr 2 DETAIL (A) DIMENSIONS INCHES F i g u r e 5. Surface Thermocouple (3) ® APPLICATOR © A •p^WET END F i g u r e 6. Assembling of Surface Thermocouples 28 i s i n s u l a t e d and maintained i n good contact with the sheet surface. Five of these thermocouples were mounted on a bar which could be moved from one side of the paper web to the other g i v i n g temperature p r o f i l e s across the sheet. The p o s i t i o n s of the thermocouples were such that temperature measurements on each side of each waveguide could be obtained. D e t a i l s of the thermo-couple mounting are shown i n f i g u r e 6 . 6 . Microwave Generator and Power Supply System A w i r i n g diagram of the power supply i s provided i n f i g u r e 7. Figure 4d i s a photograph of the power supply con-t r o l panel. The heart of the microwave generator i s a 2 . 5 kw magnetron (Microtron L3858 manufactured by L i t t o n I n d u s t r i e s L t d . E l e c t r o n Tube Div.Williamsport Penna.). The power supply has two ranges, a low power one ( 0 - 1 kw) and a high power one ( 1 - 2 . 6 kw). Both ranges can be spanned continuously by ad-j u s t i n g the Variac transformer T 2 . To change from the low to high s e t t i n g one must change the high voltage transformer tap, the_ filament voltage and the f i e l d c u r r e n t . These changes are accomplished by switch S 2 . . The fun c t i o n s of i n d i v i d u a l com-ponents of the power supply are described below:-SI - turns c o n t r o l c i r c u i t power on - s t a r t s fan FI - S F 1 - temperature sensor f o r magnet c o o l i n g - S F 1 - flow sensor f o r magnetron coolant - R l - turns on filament time delay, r e l a y TDR(Rl-l) and f i e l d current c i r c u i t s R l - 2 and R l - 3 - L l - panel d i a l l i g h t i n d i c a t i n g preheat c y c l e SFI COOLANT FLOW SWITCH 220V. 3WIRE 30A HIGH VOLTAGE SUPPLY CIRCUIT Figure 7 Wiring Diagram c f Power Supply System - R 7 - 1 i n the f i e l d s u p p l y c l o s e s , i n d i c a t i n g t h a t t h e f i e l d i s on. R 6 - l , 2 c l o s e s when the time d e l a y i s o v e r t h r o u g h R5 s w i t c h i n g i n R6 and the TDR out. L l t h e n goes o f f . The c o n t r o l power now re a c h e s t h e s e l e c t o r s w i t c h S2 i f the f i l a m e n t has been p r e h e a t e d and the f i e l d i s on 52 - S e l e c t o r s w i t c h - s h o u l d n o r m a l l y be l e f t a t low - r e l a y R2 s e l e c t s t h e c o r r e c t f i l a m e n t , v o l t a g e p r e -heat ( R 2 - 1 ) , f i e l d c u r r e n t range (R2 - 2 ) and power t r a n s f o r m e r t a p R2 - 3 - p a n e l l i g h t s L2 and L3 i n d i c a t e low o r h i g h range r e s p e c t i v e l y - do not change from low t o h i g h or v i c e v e r s a when S3 i s on 53 - Microwave o n - o f f s w i t c h - a c t i v a t e s p a n e l l i g h t s L 4 o r L5 - a c t u a t e s magnetron 7 . Microwave A p p l i c a t o r The microwave a p p l i c a t o r i s a m e a n d e r l i n e ' t y p e h a v i n g f o u r passes t h r o u g h t h e s l o t t e d waveguides (EIMAC WR-340). The d i -mensions o f t h e waveguides are 24" l e n g t h , c r o s s s e c t i o n 3" x 1 .3/4". Each waveguide has s l o t s 3 / 1 6 " wide and 2 0 " l o n g on th e 3 " x 24" f a c e s . These s t r a i g h t s e c t i o n s o f waveguide are conn e c t e d by 1 8 0 ° E bends (EIMAC EW3-EUA). Each waveguide bend has a 2 " n o z z l e which i s s h i e l d e d w i t h p e r f o r a t e d p l a t e . These n o z z l e s can be open, plugged w i t h r u b b e r c o r k s or con-31 nected to the fan depending on the air flow pattern desired. 8. Directional Power Meter A directional power meter (EIMAC EW3-DPH3),which indicates both forward and reverse power transmitted in the waveguide is coupled between the applicator and the water load. The power level is detected by one of two microwave sensitive crystals which are located so that one measures the forward power, that is the power transmitted away from the magnetron and-the other measures the reverse power, i . e . the power reflected back towards the magnetron. Perhaps the simplest and best way to measure the power absorbed by the die lectr ic material (in this case resin or water soaked paper) would be to put directional power meters between the generator and the applicator and between the applicator and the water load. The f i r s t meter would indicate power directed towards the load from the generator and power reflected back toward the generator from the load. The second meter would indicate the unabsorbed power moving from the applicator toward the water load and any power reflected back from the water load. In this apparatus.only one power meter was used. Thus only unabsorbed forward power is measured by the power meter. The total power generated was measured before the load ( i . e . the paper) was in the waveguide. The procedures for evaluating the absorption of power and the calibration of the power meter are given in Appendix A. 9. Water Load A water load (EIMAC EW3-WL) is instal led at the end of the waveguide remote from the generator to absorb any excess power not absorbed by the load or to absorb a l l the power when there i s no other load. Thermocouples at the water i n l e t and out-l e t and a rotameter allow the use of the water load as a ca l o r i m e t e r . This r e q u i r e s that the water load be w e l l i n -s u l a t e d to d i m i n i s h any heat l o s s e s . 10. S h i e l d i n g and Rad i a t i o n Leakage I t i s known that microwave r a d i a t i o n i s hazardous f o r (31) humans. Recently Birenbaum et a l . have shown how s u f f i c i e n t l y high l e v e l s of microwave r a d i a t i o n can lead to lens i n j u r i e s i n the eye of a r a b b i t . S i m i l a r lens defects could be induced i n the human eye because of a s i m i l a r i t y i n anatomy and f u n c t i o n to that of the r a b b i t . In order to guard against t h i s hazard and any others which might r e s u l t from microwave, r a d i a t i o n s a f e t y l i m i t s have been p r e s c r i b e d by various agencies. The U.S. Rad i a t i o n C o n t r o l f o r Health and Safety Act suggests a maximum p e r m i s s i b l e exposure of p 10 m i l l i w a t t s per cm . However, there i s considerable d i s -s a t i s f a c t i o n with t h i s l e v e l , and recent trends are towards - 2 adopting the U.S.S.R. standard of .01 mw/cm f o r a l l day exposure. In t h i s work the microwave a p p l i c a t o r was almost completely surrounded by aluminium sheet s h i e l d i n g to minimize r a d i a t i o n le a k s . Figure 4c shows the s h i e l d i n g i n place over the a p p l i c a t o r . Checks f o r leaks were made with a neon bulb ( P h i l l i p s 4662) which was supposed to: t u r n blue i f the r a d i a t i o n i n t e n s i t y i s 2 greater than 10 mw/cm . Later i n the work a Ramcor densio-meter (model 1270) was purchased. This instrument reads r a d i a t i o n i n t e n s i t y q u a n t i t a t i v e l y from Omw/cm to 20mw/cm • t o w i t h i n 0.5 mw/cm . These instruments are c a l i b r a t e d i n f i e l d s emanating from d i s t a n t source so they' (32 may be i n a c c u r a t e when readings are taken c l o s e to c o n d u c t o r s V J I t should a l s o be kept i n mind t h a t the r a d i a t i o n i n t e n s i t y de-creases w i t h the i n c r e a s e of the d i s t a n c e from the source squared- Thus a remote c o n t r o l p a n e l was c o n s t r u c t e d so the operator d i d not have to stand c l o s e t c the machine. During the work the neon bulb was used around the apparatus to d e f e c t any l e a k s . Prom time to time a check w i t h the densiometer was made. IV - EXPERIMENTAL 1. Base Paper and Resin T,he base paper used i n these experiments was 130 l b . bleached k r a f t paper. T h i s was s u p p l i e d by R e i c h h o l d Chemicals (Canada) L i m i t e d i n r o l l form. The long r o l l s were cut to g i v e a r o l l width of 18". The r e s i n used was a phenol-formaldehyde type s u p p l i e d by Reichhold Chemicals (Canada) L i m i t e d and c a l l e d s o l u b l e , modi-f i e d p h e n o l i c r e s i n . The r e s i n s o l u t i o n as s u p p l i e d c o n t a i n s about 50% (by weight) of n o n v o l a t i l e s o l i d s . T h i s r e s i n was slowly d i l u t e d with water to a f i n a l s o l i d s content of around 25%. T h i s l a t t e r r e s i n s o l u t i o n was used i n the impregnating and d r y i n g experiments. Before each group of d r y i n g ex-periments 1-2 grams of r e s i n s o l u t i o n were a c c u r a t e l y weighed i n a g l a s s d i s h and d r i e d at 120°C f o r 2 hours. A f t e r c o o l i n g the r e s i d u e (non v o l a t i l e s o l i d s ) was weighed. The r e s i n content then i s d e f i n e d as the percentage of n o n v o l a t i l e m a t e r i a l i n t h e . r e s i n s o l u t i o n . 2. Start-Up and Shut-Down of the Microwave Power Supply System The microwave power supply system was turned on at l e a s t two hours before the d r y i n g experiment to ensure steady power g e n e r a t i o n . D e t a i l s of the power measuring methods are g i v e n i n Appendix A. The s t a r t up and shut down procedures are as f o l l o w s : -S t a r t up. 1) 'Connect the power meter leads to the waveguide out-l e t s . 35 . 2) Turn on the cooling water and set the flow so that the water pressure i s at least 30 psig. 3) Plug i n the r a d i a t i o n detector lamp 4 ) Switch on the "main power" switch. The two f i e l d supply l i g h t s and the two high voltage supply l i g h t s should turn on 5) Turn on the "system" switch. The control p i l o t l i g h t , the filament l i g h t and the pre-heat l i g h t should turn on. After about 20 seconds the preheat l i g h t should go o f f and the high range l i g h t and the microwave l i g h t should r go on 6) Set the range control switch 7) Turn on the "microwave" switch 8) Adjust the power l e v e l with the Variac 9) Turn on the v e n t i l a t i o n fan 10) Check for r a d i a t i o n leaks with the neon lamp detector or with the Ramcor densiometer Shut down 1) Turn the "microwave" switch o f f 2) Turn the "system" switch o f f 3) Turn the "main power" switch o f f 4 ) Turn o f f the water 5) Turn o f f t h e . v e n t i l a t i o n fan 3. Procedure for Drying Experiments After the microwave power generation has reached steady state the power i s adjusted to the l e v e l at which the ex-periment i s to be performed. The power meter output, t o t a l supply c u r r e n t , water flow r a t e and temperature are r e -corded. F o l l o w i n g these measurements the "microwave" switch i s turned o f f and the paper web threaded through the waveguide s l o t s . The paper d r i v e i s turned on and s h i e l d i n g p l a c e d over the microwave a p p l i c a t o r . A f t e r the wet paper has reached the dry end waveguide the "microwave" switch i s turned on and readings of the paper surface, temperature at the dry end are begun. The s u r f a c e temperature here rose r a p i d l y and reached a steady s t a t e i n a few minutes, however, at l e a s t 5 minutes was allowed to pass a f t e r the microwave a p p l i c a t i o n was s t a r t e d before readings were taken. The product paper was marked to d i s -t i n g u i s h the presteady s t a t e m a t e r i a l from the steady s t a t e m a t e r i a l . Steady s t a t e o p e r a t i o n was normally continued f o r about 5 to 10 minutes i n order to get enough product f o r q u a l i t y a n a l y s i s . During the steady s t a t e o p e r a t i n g p e r i o d power meter r e a d i n g s , water flow r a t e s , i n l e t and o u t l e t temperatures of water l o a d c o o l a n t , h i g h . v o l t a g e supply c u r r e n t , a i r temperature and humidity and paper s u r f a c e temperatures were recorded. , A f t e r c o l l e c t i n g enough product the "microwave" switch, the paper d r i v e , and the v e n t i l a t i o n f a n were turned o f f at the same time. The s h i e l d i n g was q u i c k l y removed and paper samples taken. About 5 - 1 0 grams of paper were t o r n o f f from before the wet end waveguide,between.each waveguide and a f t e r the dry .end waveguide, g i v i n g 5 samples. These samples were immediately wrapped i n preweighed p o l y e t h y l e n e sheets and weighed. A f t e r weighing the sheets were unwrapped and d r i e d i n an a i r oven at 120°C f o r 2.hours. The d r i e d paper'was then weighed and the moisture or r e s i n content of the o r i g i n a l sheets determined. . T o t a l r e s i n p i c k up was obtained from these measurements on the sample taken'from the wet end assuming no moisture-was l o s t before e n t e r i n g the waveguide. The paper was then removed from the waveguide and the microwave switch and v e n t i l a t i o n a i r turned on again-. A f t e r w a i t i n g about 5 minutes the o p e r a t i n g c o n d i t i o n s were r e -corded, and compared with the data obtained p r i o r t o i n s e r t i o n of the paper. The microwave power system was then shut down or r e a d j u s t e d t o another l e v e l f o r the next experiment. 4. T e n s i l e S t rength Measurement The t e n s i l e s t r e n g t h s of the papers used i n t h i s study (33) were t e s t e d by a standard m e t h o d X J J . Ten samples i n the machine d i r e c t i o n and ten samples i n the cross machine d i r e c t i o n were t e s t e d to get average values f o r each sample. The measurements were made on an I n s t r o n t e s t i n g machine which p r o -duced l o a d e l o n g a t i o n curves f o r each sample t e s t e d . Thus i n a d d i t i o n to the t e n s i l e b r e a k i n g s t r e s s , the s t r e t c h to r u p t u r e , and Young's modulus: could.be determined from the l o a d - e l o n g a t i o n curve. Paper t h i c k n e s s was measured at three p o i n t s along the t e n s i l e sample s t r i p u s i n g a micrometer. These t h i c k n e s s measurements were averaged to give the paper t h i c k n e s s . F i g u r e 8 i s a t y p i c a l load e l o n g a t i o n curve obtained with r e s i n impregnated paper. As the lower clamp of the t e s t i n g machine moves away from the f i x e d upper clamp the paper i s ex-tended at a constant r a t e . Up to p o i n t A the l o a d i s pro-0 s 2 ELONGATION Figure 8. Load-Elongation Curve 39 p o r t i o n a l t o t h e e l o n g a t i o n . P o i n t A i s c a l l e d t h e p r o -p o r t i o n a l l i m i t a n d b e y o n d t h i s t h e l o a d d e v e l o p e d p e r u n i t i n c r e a s e i n e x t e n s i o n i s l e s s a n d l e s s : t h e p a p e r s a m p l e b r o k e a t p o i n t B. T h e t e n s i l e s t r e n g t h i s t h e s t r e s s a t p o i n t B. T h i s s t r e s s i s t h e l o a d a t p o i n t B d i v i d e d b y t h e c r o s s s e c t i o n a l p a r e a o f t h e s h e e t a n d i s r e p o r t e d i n k g / c m . T h e " t o t a l e l o n g a t i o n i s t h e d i s t a n c e O S i t h i s i s u s u a l l y e x p r e s s e d a s a p e r c e n t a g e . T h u s s t r a i n i s t h e e x t e n s i o n d i v i d e d b y t h e o r i g i n a l s a m p l e l e n g t h b e t w e e n t h e c l a m p s . T h i s ' i s m u l t i p l i e d b y a h u n d r e d a n d r e p o r t e d a s s t r e t c h . Y o u n g ' s m o d u l u s i s t h e r a t i o o f s t r e s s t o s t r a i n i n t h e r e g i o n OA. T h e t e n s i l e s a m p l e s w e r e 4" l o n g , 1.5 cm w i d e a n d w e r e t e s t e d a t a r a t e o f e x t e n s i o n o f 0 . 0 5 " / m i n . ( r e c o r d e r c h a r t s p e e d .= l " / m i n . ) a f t e r c o n d i t i o n i n g a t l e a s t 24 h o u r s i n a r o o m m a i n t a i n e d a t 23°C a n d 50% r e l a t i v e h u m i d i t y . 5. P a p e r B e n d i n g T e s t B r i t t l e n e s s a n d f l e x i b i l i t y a r e t w o i m p o r t a n t c r i t e r i a u s e d i n a s s e s s i n g t h e q u a l i t y o f r e s i n t r e a t e d p a p e r . H o w e v e r , t h e s e c r i t e r i a a r e d i f f i c u l t t o e v a l u a t e q u a n t i t a t i v e l y . T h e r e do n o t s e e m t o b e a n y s t a n d a r d t e s t s f o r . t h e s e p r o p e r t i e s . I t w a s f e l t t h a t some i n d i c a t i o n o f b r i t t l e n e s s a n d / o r f l e x i b i l i t y m i g h t b e p r o v i d e d b y a b e n d i n g t e s t . S o a n i n -s t r u m e n t w a s d e s i g n e d a n d b u i l t ( s e e f i g u r e 9) t o m e a s u r e t h e a n g l e a t w h i c h a s t r i p o f p a p e r b r e a k s w h e n b e n t a s s h o w n i n t h e f i g u r e . T h i s b r e a k i n g a n g l e i s p r o b a b l y d e p e n d e n t o n s a m p l e w i d t h , s a m p l e l e n g t h , a n d t h e a n g u l a r v e l o c i t y o f b e n d i n g , t h e r e -f o r e a l l t h e s e v a l u e s w e r e k e p t c o n s t a n t i n t h e t e s t s . T h e s a m p l e d i m e n s i o n s u s e d w e r e w i d t h 1.5 cm a n d l e n g t h 10 cm. T h e 40 Pigure 9. Paper Bending Tester a n g u l a r v e l o c i t y w a s 180 d e g r e e s p e r m i n u t e . T e n s a m p l e s w e r e t e s t e d a n d a v e r a g e d f o r e a c h p a r t i c u l a r p a p e r t e s t e d . A g a i n t h i s m e a s u r e m e n t w a s d o n e u n d e r c o n t r o l l e d e n v i r o n m e n t c o n d i t i o n s o f 23°C a n d 50% r e l a t i v e h u m i d i t y . 6. I n f e r n a l B o n d T e s t T h e i n t e r n a l b o n d o f a r e s i n i m p r e g n a t e d s h e e t i s a m e a s u r e o f i t s r e s i s t a n c e t o b e i n g p u l l e d a p a r t b y f o r c e s a p p l i e d t o i t ' s t o p a n d b o t t o m s u r f a c e s . T h i s w o u l d s e e m t o b e a p r o -p e r t y w h i c h s h o u l d b e q u i t e s e n s i t i v e t o r e s i n d i s t r i b u t i o n . A C S A ^ ^ ) s t a n d a r d t e s t f o r i n t e r n a l b o n d w a s f o l l o w e d . T h e t e s t s p e c i m e n w a s 2 . 1 / 2 " s q u a r e a n d w a s b o n d e d b e t w e e n t w o l o a d i n g b l o c k s :made o f a s t e e l a l l o y . T h e s e w e r e 2" s q u a r e a n d 1" t h i c k a s c a n b e s e e n i n f i g u r e 10.. T h e s e b l o c k s m u s t b e f r e e o f a n y s u r f a c e c o n t a m i n a t i o n . T h e a d h e s i v e h a d t o b e s e l e c t e d c a r e f u l l y b e c a u s e we d i d n o t w a n t t h e a d h e s i v e w h i c h b o n d s t h e s h e e t t o t h e b l o c k s t o p e n e t r a t e i n t o t h e s h e e t . F o r t h i s p u r p o s e a p o l y e s t e r a d h e s i v e w a s u s e d w h i c h c o n s i s t e d o f 1 0 0 p a r t s o f E p o x y R e s i n ( E p o t u s 3 7 - 1 4 0 ) t o 32 p a r t s o f H a r d e n e r ( E p o t u s 3 7 - 6 0 5 ) . T h e w e l l m i x e d a d h e s i v e w a s a p p l i e d a s u n i f o r m l y a s p o s s i b l e t o t h e s u r f a c e s o f t h e b l o c k s a n d t h e p a p e r a n d t h e n t h e p a p e r was p l a p e d b e t w e e n t h e b l o c k s . T o e n -s u r e c o m p l e t e c o n t a c t b e t w e e n t h e s p e c i m e n : a n d t h e b l o c k s a c i r c u l a r r u b b i n g t e c h n i q u e w,as u s e d . K e e p i n g t h e s t e e l b l o c k s a l i g n e d v e r t i c a l l y , 2 t o 4 h o u r s w e r e a l l o w e d f o r t h e a d h e s i v e t o s e t . T h e i n t e r n a l b o n d was m e a s u r e d i n a t e n s i l e t y p e t e s t e r ( N a t i o n a l F o r g e T e s t e r ) a t c o n s t a n t r a t e o f e x t e n s i o n . T h i s m e a s u r e m e n t s h o u l d b e d o n e i n a c o n t r o l l e d e n v i r o n m e n t b u t b e c a u s e SAMPLE SHEET 2 g X 2 ^ STEEL BLOCKS c:;z DIMENSIONS INCHES F i g u r e 10. Metal B l o c k s f f o r I n t e r n a l Bond Test t h e t e s t s were done i n an i n d u s t r i a l l a b o r a t o r y t h i s was n o t p o s s i b l e . The t e s t r e s u l t i s p s i r e q u i r e d t o p u l l t h e b l o c k s a p a r t . 7. S u r f a c e A b r a s i o n T e s t The s u r f a c e a b r a s i o n t e s t i s a measure o f t h e a b i l i t y o f t h e s u r f a c e o f a r e s i n i m p r e g n a t e d p a p e r t o r e s i s t a b r a s i o n . The d e v i c e u s e d was a T a b e r A b r a s e r M odel 503 u s i n g a b r a s i v e w h e e l s C5-17 and a l o a d o f 750 grams. Once a g a i n a l t h o u g h s t a n d a r d t e m p e r a t u r e and h u m i d i t y c o n d i t i o n s w o u l d have been d e s i r a b l e , t h e s e were n o t a v a i l a b l e . I n t h e t e s t a b r a s i v e w h e e l s u n d e r l o a d a b r a d e t h e s u r f a c e o f t h e s h e e t . The number o f r e v o l u t i o n s i s c o u n t e d and t h e w e i g h t l o s s o r s h e e t t h i c k n e s s i s r e c o r d e d a f t e r v a r i o u s numbers, o f r e v o l u t i o n s . F o r t h e s e t e s t s t h e r e s i n t r e a t e d p a p e r was o v e r l a i d o n t o h a r d b o a r d . The o v e r l a y i n g was done i n a h o t p r e s s a t 300°F u n d e r 2000 p s i l o a d f o r 5 m i n u t e s . The o v e r l a i d b o a r d was c u t i n t o 4" s q u a r e s and p u t i n t h e t e s t e r . The t h i c k n e s s o f t h e sample was measured a t f o u r p o i n t s by m i c r o m e t e r and t h e a v e r a g e d e c r e a s e i n t h i c k n e s s w i t h a b r a s i o n c a l c u l a t e d . The t h i c k n e s s was r e c o r d e d a f t e r e v e r y 500 c y c l e s u n t i l t h e p a p e r - h a r d b o a r d i n t e r f a c e was r e a c h e d . The w e a r i n g f a c t o r i s d e f i n e d as t h e t h i c k n e s s d e c r e a s e i n i n c h e s p e r 10^ a b r a s i o n c y c l e s . The w e a r i n g f a c t o r i s p l o t t e d a g a i n s t t h e t o t a l number o f a b r a s i o n c y c l e s and t h e d i s t a n c e f r o m t h e o r i g i n a l s u r f a c e s 8. Q u a n t i t a t i v e R e s i n D i s t r i b u t i o n M e a s u r e m e n t A s a p a r t o f t h i s w o r k t w o m e t h o d s w e r e t r i e d f o r d e t e r -m i n i n g i n a q u a n t i t a t i v e way t h e r e s i n d i s t r i b u t i o n a c r o s s t h e s h e e t . T h e s e i n v o l v e d t h e r e m o v a l o f c e l l u l o s e b y h y d r o l y s i s w i t h 1 ) s u l f u r i c a c i d o r 2 ) h y d r o f l u o r i c a c i d a f t e r s e c t i o n i n g o f t h e s h e e t ( s e e S e c t i o n I I - 3 ) . T h e s u l f u r i c a c i d m e t h o d i s b a s e d o n t h e T a p p i s t a n d a r d ( 2 8 ) m e t h o d f o r l i g n i n d e t e r m i n a t i o n . T h e h y d r o f l u o r i c a c i d • ( 2 3 ) t e c h n i q u e w a s s u g g e s t e d b y T a k a h a s h i a n d V a s i s h t h •. A s o u t l i n e d i n S e c t i o n I I - 3 t h e d e t e r m i n a t i o n o f a r e s i n c o n c e n t r a t i o n p r o f i l e t h r o u g h t h e t h i c k n e s s o f a d r i e d , a n d c u r e d , r e s i n i m p r e g n a t e d s h e e t r e q u i r e s t h a t t h e s h e e t b e s e c t i o n e d i n t o t h i n l a y e r s . I n o r d e r t o a c h i e v e t h i s s e c t i o n i n g t h e r e s i n i m p r e g n a t e d s h e e t was f i x e d t o a c i r c u l a r a l u m i n i u m d i s c a n d s e c t i o n s o f t h e p a p e r m a c h i n e d ^ o f f f r o m t h e s u r f a c e u s i n g a m a c h i n i s t ' s l a t h e . T h e d u s t a n d s h a v i n g s f r o m e a c h l a y e r w e r e c o l l e c t e d a n d a n a l y z e d f o r r e s i n c o n t e n t . I n d e t a i l t h e n t h e p a p e r s a m p l e was d r i e d a t 170°C f o r 5 m i n u t e s . A 6" d i a m e t e r c i r c l e w a s c u t f r o m t h i s c u r e d s h e e t a n d g l u e d o n t o t h e f a c e o f a 6" d i a m e t e r a l u m i n i u m d i s c w i t h s t a r c h g l u e . S e v e r a l k i n d s o f g l u e w e r e u s e d i n p r e l i m i n a r y e x p e r i m e n t s , h o w e v e r , i t w a s f o u n d t h a t . s t a r c h g l u e g a v e g o o d a d h e s i o n w i t h m i n i m u m p e n e t r a t i o n i n t o t h e s h e e t . I t was f e l t t h a t a l t h o u g h u n l i k e l y , p e n e t r a t i o n o f t h e " g l u e i n t o t h e s h e e t m i g h t i n t e r f e r e w i t h t h e r e s i n d i s t r i b u t i o n d e t e r m i n a t i o n . T o c h e c k t h e p e n e t r a t i o n t h e g l u e w a s d y e d w i t h i n k . S e c t i o n s w e r e c u t u s i n g t h e l a t h e u n t i l t h e i n k w a s v i s i b l e . B y m e a n s o f e x p e r i m e n t s s u c h a s t h i s t h e p e n e t r a t i o n o f s t a r c h g l u e i n t o t h e s h e e t w a s f o u n d t o b e l e s s t h a n 0.1 mm i n a s h e e t w h i c h w a s 45 HOLDER! PAPER SAMPLE MACHINE CENTER CARRIAGE CENTER TOP COMPOUND CUTTING ANGLE Figure 12. Experimental Set-up of Se c t i o n i n g 46 a r o u n d 0.45 mm i n t h i c k n e s s . The a l u m i n i u m d i s c w i t h t h e mounted p a p e r sample was c a r e f u l l y a l i g n e d i n t h e l a t h e so t h a t t h e t i p o f t h e c u t t i n g t o o l was e x a c t l y p a r a l l e l t o t h e p l a n e o f t h e s h e e t . The c u t t e r t i p was a d j u s t e d t o j u s t t o u c h t h e p a p e r s u r f a c e and t h e l o n g i t u d i n a l c a r r i a g e f i x e d . The t o p compound f e e d o f t h e l a t h e was a d j u s t e d t o remove t h e d e s i r e d t h i c k n e s s o f p a p e r . I n t h e e x p e r i m e n t s a t y p e 25-A S o u t h Bend l a t h e " w a s u s e d . T h i s machine had a .001" t o p compound i n d i c a t o r and an a d j u s t a b l e c u t t i n g a n g l e o f f r o m 0 t o 90°. E a c h s l i c e o f p a p e r was r e -moved by m o v i n g t h e t o p compound i n d i c a t o r (and hence t h e c u t t i n g t o o l ) i n . by .002". S i x s e c t i o n s c o u l d be c u t f r o m a t y p i c a l sample f r o m t h e o u t s i d e t o t h e c e n t r e o f t h e s h e e t . The r e s i n d i s t r i b u t i o n was assumed t o be s y m m e t r i c a l about t h e c e n t r e o f t h e s h e e t . F i g u r e 11 shows t h e a l u m i n i u m d i s c and f i g u r e 12 shows t h e e x p e r i m e n t a l s e t up f o r s e c t i o n i n g . a) P r e t r e a t m e n t o f Samples I t was f e l t t h a t t o g e t u n i f o r m r e s u l t s t h e r e s i n im-p r e g n a t e d s h e e t s s h o u l d be f u l l y c u r e d b e f o r e r e s i n a n a l y s i s was done as t h e r e c o v e r a b i l i t y o f r e s i n m i g h t be a f f e c t e d by t h e d e g r e e o f c u r e . The p a p e r samples u s e d i n s e c t i o n i n g were c u r e d a t 170°C-. f o r 5 m i n s . p r i o r t o s e c t i o n i n g w h i c h i s e q u i v a l e n t t o c o m m e r c i a l p r a c t i c e . : I n o r d e r t o f i n d out w h e t h e r t h i s r e p r e s e n t e d a f u l l c u r e some e x p e r i m e n t s were u n d e r t a k e n . F i g u r e 13 i s a p l o t o f un-i m p r e g n a t e d p a p e r sample w e i g h t d i v i d e d by t h e w e i g h t a f t e r a c e r t a i n d r y i n g p e r i o d w e i g h t . T h r e e t e m p e r a t u r e s ' were u s e d 120°, 150°j and 170°C. O n l y . s l i g h t c h a n g e s i n m o i s t u r e c o n -•00 | -90 co 0 SYMBOL O A • 60 120 TIME(min) Figure 13. Drying Curves f o r Base Paper T E M P ( ° C ) 120 150 170 180 -^ 3 t e n t o c c u r r e d a f t e r 1 h o u r . S o 1 h o u r i s s u f f i c i e n t t o d r y t h e u n i m p r e g n a t e d p a p e r . I n f i g u r e 14 a r e p l o t t e d t h e r e s u l t s o f c u r i n g d r i e d r e s i n ( n o p a p e r ) . T h e r e s i n s o l u t i o n w a s d r i e d f o r 2 h o u r s a t 1 2 0 ° C . T h i s d r i e d m a t e r i a l w a s c r u s h e d a n d s c r e e n e d t o p a s s a 60m s c r e e n . T h i s s c r e e n e d m a t e r i a l w a s t h e n c u r e d a t 1 2 0 ° , 1 5 0 ° , a n d 170°C f o r v a r i o u s t i m e s . T h e r a t i o o f w e i g h t t o i n i t i a l w e i g h t i s p l o t t e d v s t i m e . S i g n i f i c a n t w e i g h t l o s s e s w e r e r e -c o r d e d up t o 3 h o u r s . I n f i g u r e 15 t h e e q u i v a l e n t c u r v e s f o r r e s i n i m p r e g n a t e d p a p e r s a r e p r e s e n t e d . P r o m t h e s e f i g u r e s i t c a n b e c o n c l u d e d t h a t t h e r a t e o f c u r i n g o f t h e r e s i n i s a m u c h s l o w e r p r o c e s s t h a n t h e r a t e o f r e m o v a l o f m o i s t u r e ( o r o t h e r v o l a t i l e ) f r o m t h e p a p e r i t s e l f . T h i s r a t e i s a l s o t e m p e r a t u r e d e p e n d e n t . b ) R e s i n C o n t e n t A n a l y s i s - S u l f u r i c A c i d M e t h o d A b o u t 0.5 gm o f t h e l a t h e t u r n i n g s o f t h e r e s i n i m p r e g n a t e d p a p e r w a s a c c u r a t e l y w e i g h e d a n d . d r i e d f o r 2 h o u r s a t 120°C i n a w e i g h i n g b o t t l e . 10 m l o f 75% s u l f u r i c a c i d w e r e t h e n a d d e d t o t h e w e i g h e d . ' m a t e r i a l a n d a g i t a t e d u n t i l t h e s a m p l e w a s c o m -p l e t e l y d i s p e r s e d . T h i s m i x t u r e was m a i n t a i n e d a t 20°C f o r 2 h o u r s , p o u r e d i n t o a 5 0 0 m l f l a s k a n d d i l u t e d w i t h 2 5 0 m l o f w a t e r . T h e d i l u t e d s u s p e n s i o n w a s r e f l u x e d f o r 4 h o u r s . T h i s t r e a t m e n t i s p r e s u m e d t o d i s s o l v e a l l o f t h e c e l l u l o s e . T h e n a n y r e m a i n i n g s o l i d s w e r e r e m o v e d i n a t a r e d , s i n t e r e d g l a s s c r u c i b l e , w a s h e d w i t h 2 0 0 m l o f h o t w a t e r , d r i e d a t 120°C f o r 2 h o u r s a n d t h e w e i g h t o f r e s i d u e d e t e r m i n e d . T h e r e s i d u e i s a s s u m e d t o b e r e s i n p l u s a n y l i g n i n w h i c h c o u l d come f r o m t h e b a s e p a p e r . 49 Figure 15. Drying Curves f o r Resin Impregnated Paper o An i d e n t i c a l t r e a t m e n t o f t h e b a s e p a p e r a l l o w e d c o r r e c t i o n f o r t h e l i g n i n c o n t e n t . R e s i n r e c o v e r a b i l i t y by t h i s t e c h n i q u e was c h e c k e d by u s i n g known amounts o f r e s i n . T a b l e I p r e s e n t s t h e l i g n i n c o n t e n t o f t h e b a s e p a p e r and r e s i n r e c o v e r a b i l i t y f i g u r e s . The l i g n i n c o n t e n t o f t h e base p a p e r i s n e g l i g i b l e . I n t h e r e s i n r e c o v e r a b i l i t y method d r i e d r e s i n was c r u s h e d and s c r e e n e d t o -60 m. Samples o f t h i s m a t e r i a l were d r i e d f o r 2 'hours a t 120°C and a n a l y z e d f o r r e s i n c o n t e n t as o u t l i n e d a bove. About 80% o f t h e r e s i n was r e c o v e r e d a f t e r t h e a n a l y s i s . I t i s . known t h a t s o d i u m h y d r o x i d e i s u s e d as a c a t a l y s t i n t h i s r e s i n f o r m u l a t i o n b u t how much i s n o t known. T h i s may a c c o u n t f o r t h e l o s s e s . To c h e c k t o see i f r e s i n was b e i n g c o n t i n u a l l y d i s s o l v e d . t h e r e s i d u e f r o m one a n a l y s i s was r e a n a l y s e d . The r e c o v e r y o f t h i s p r e t r e a t e d r e s i n was 100%. Thus i f t h i s s u l f u r i c a c i d method i s t o be u s e d t h e r e s i n c o n t e n t must be d e t e r m i n e d as , . ,at\ r e s i d u e w e i g h t x 100 r e s i n c o n t e n t {%) = -3 ^ &—=—r-r- TT—XT d r y sample w e i g h t O.o c) R e s i n C o n t e n t A n a l y s i s - H y d r o f l u o r i c A c i d Method An a c c u r a t e l y w e i g h e d sample o f d r i e d l a t h e s h a v i n g s o f t h e r e s i n i m p r e g n a t e d p a p e r was t r a n s f e r r e d i n t o a p o l y p r o p y l e n e b o t t l e . About 10 gms o f 80% h y d r o f l u o r i c a c i d was t h e n added t o t h e m a t e r i a l i n t h e b o t t l e . T h i s - m i x t u r e was k e p t a t 20°C f o r 1 h o u r w i t h s h a k i n g e v e r y 10 m i n u t e s . A f t e r t h i s t h e m i x t u r e was- d i l u t e d w i t h 100 ml o f w a t e r and n e u t r a l i z e d w i t h 10-20% ammonium h y d r o x i d e s o l u t i o n u n t i l j u s t a l k a l i n e . : P h e n o l p h t h a l e i n was u s e d as an i n d i c a t o r o f a l k a l i n i t y . The n e u t r a l i z e d m i x t u r e was f i l t e r e d t h r o u g h a t a r e d , s i n t e r e d g l a s s c r u c i b l e , a n d washed w i t h w a t e r u n t i l no p h e n o l p h t h a l e i n 52 " T A B L E "'.I S U L F U R I C A C I D TREATMENT DATA FOR B A S E P A P E R , PURE R E S I N , AND R E S I N I M P R E G N A T E D P A P E R S A M P L E WT. R E S I D U E WT. R E S I D U E (grO ( g r ) (%) 1 . 0. ,5186 ^ 0. ,0009 0. .2 B A S E PAPER. •2 . 0, .5054 0. ,0003 0. .1 3 0, • 5415 0. .0024 0. .4 1 1, .1096 0. .8857 80. .0 PURE R E S I N 2 1. .0723 0. .8506 79-.5 3 1. .0341 0. .8283 80. ,0 R E S I N I M P R E G -NATED PAPER. 1 2 3 0. 0. 0. .2117 • 2134 ,1980 . 0. 0. 0. .0633 ,0681 ,0620 29. 31. 31. .9 .9 .3 T A B L E I I H Y D R O F L U O R I C A C I D TREATMENT DATA FOR B A S E P A P E R , PURE R E S I N , . AND R E S I N I M P R E G N A T E D P A P E R S A M P L E T R E A T I N G T I M E ( h r ) . S A M P L E WT, • ( g r ) R E S I D U E WT, ( g r ) R E S I D U E {%) B A S E P A P E R 1 2 4 0.4207 0.7957 1.1708 0 . 0 0 1 2 0 . 0 0 4 2 0 . 0 0 3 6 0.28 0.53 0.33 PURE R E S I N 1 2 4 1.2166 1.6458 2.1084 1 . 0 1 3 5 1 . 4 1 2 4 1 . 8 1 3 6 83.30 85.82 86.02 R E S I N 1 0.6636 0.1690 25.47 I M P R E G N A T E D 2 0.6503 0.1541 23-70 P A P E R 4 0.6511 0.1576 2 4 . 4 1 5 could be seen i n the f i l t r a t e (the wash water was made s l i g h t l y alkaline by addition of ammonia). The washed residue was then dried and weighed. The residue consisted of recovered r e s i n and l i g n i n and so corrections to get the r e s i n content were necessary. Various times were t r i e d for the hydrofluoric acid treatment. The re-sults are given i n Table I I . From these results i t seemed that 1 hour was s u f f i c i e n t . Lignin content again was low but was measured to be somewhat higher than i n the s u l f u r i c acid technique. The r e s i n r e c o v e r a b i l i t y was higher at about 85%. 54 V - RESULTS AND DISCUSSION 1. D r y i n g E x p e r i m e n t s The d r y i n g e x p e r i m e n t s were o f t h r e e k i n d s . T h e s e were t h e d r y i n g o f p a p e r w e t t e d w i t h w a t e r , t h e d r y i n g o f r e s i n i m -p r e g n a t e d p a p e r , and t h e d r y i n g o f p a p e r w e t t e d w i t h w a t e r by c o n -v e c t i o n o n l y . The l a s t c a t e g o r y was m e r e l y a c h e c k on any c o n -t r i b u t i o n w h i c h m i g h t be made t o d r y i n g by t h e movement o f a i r t h r o u g h t h e w a v e g u i d e . a ) D r y i n g o f P a p e r W e t t e d w i t h W a t e r I n t h e s e e x p e r i m e n t s t h e b a s e p a p e r u s e d f o r r e s i n i m -p r e g n a t i o n was w e t t e d i n w a t e r and d r i e d u s i n g m i c r o w a v e s . T h e s e d r y i n g e x p e r i m e n t s were p e r f o r m e d a t f i v e m i c r o w a v e power a p p l i c a t i o n l e v e l s , a t c o n s t a n t p a p e r f e e d r a t e and more o r l e s s c o n s t a n t i n i t i a l m o i s t u r e c o n t e n t . : The r e s u l t s a r e r e p o r t e d i n T a b l e s I I I and IV. I n t h e s e t a b l e s t h e n e t p o w e r . g e n e r a t e d was d e t e r m i n e d f r o m t h e d i f f e r -e n c e between t h e f o r w a r d and r e v e r s e power m e t e r r e a d i n g s and t h e c a l i b r a t i o n c u r v e f o r t h i s m e t e r ( s e e A p p e n d i x A ) . The t o t a l s u p p l y c u r r e n t was m e a s u r e d and u s e d i n c a l c u l a t i n g t h e o v e r a l l e f f i c i e n c y o f t h e d r y e r ( s e e A p p e n d i x E ) . I n o r d e r t o s t u d y c o n v e c t i v e mass t r a n s f e r r a t e s f r o m t h e wet s h e e t one w o u l d have t o t r y t o m a i n t a i n a c o n s t a n t v e l o c i t y o f a i r o v e r t h e s h e e t s u r f a c e a t t h e same m o i s t u r e c o n t e n t . I n t h e s e e x p e r i m e n t s t h i s was p r a c t i c a l l y i m p o s s i b l e t o do. The f a n u s e d t o v e n t i l a t e t h e w a v e g u i d e s u c k e d a i r t h r o u g h t h e s l o t s i n t h e w a v e g u i d e and removed t h i s a i r and any e v a p o r a t e d w a t e r w h i c h d i d n o t c o n d e n s e i n t h e p i p i n g . What c o n t r o l t h e r e was was 55 TABLE I I I DRYING DATA FOR WET PAPER EXPERIMENT NUMBER (WATER) OPERATING CONDITION _ _ _ . „ 1 2 ... 3 H 5 FORWARD POWER (kw) 0-. 50 1. 00 1. 60 2. 10 2. 50 REVERSE POWER (kw) 0. 0 0. 03 0. 05 0, .07. 0. 06 POWER'GENERATION (kw) 0. 70 1. 36 2. 25 2. 70 2. 95 SUPPLY CURRENT (amp) 7. 7 16. 5 22. 6 26. 4 29. 4 WATER FLOW RATE ( k g / h r ) 36. 0 39. 5 36. 5 37. 5 36. 0 INLET TEMP. (°C) 11. 5 11. 5 11. 5 11. 2 11. 2 OUTLET TEMP. (°C) 27. 5 38. 0 61. 5 74. 0 75. 0 WET AIR FLOW R A T E ( k g / h r ) 205. 5 186. 7 172. 3 166. 0 164. 4 DRY AIR FLOW R A T E ( k g / h r ) 200. 5- 184. 0 162. 8 155. 7 153. 4 DRY BULB TEMP.. ( ° c ) 30 . 9 37. 2 43. 0 .. 46 . 3 47. 0 WET BULB TEMP. ( ° c ) 28. 7 34. 3 42 . 2 44. 6 46 . 1 HUMIDITY (kg/kg) 0.024.3 0.0339 0.0551 0.0682 0.0688 ROOM TEMPERATURE (°C) 26. 8 29. 5 25. 3 27. 5 27. 5 REL. HUMIDITY 77. 9 78. 3 62. 1 62. 6 61. 8 ATM. PRESSURE (mmHg) 754. 6 754; 6 756. 3 756. 3 756. 3 SURFACE TEMP. 1 • 56. 6 69. 1 63. 4 50. 1 59. 5 OF PAPER (°C) 2 39. 6 57. 6 85. 2 51. 2 39. 8 3 31. 1 45. 4 67. 1 30. 5 59. 7 4 27. 4 31. 4 31. 8 30. 5 52. 4 5 24 . 9 30. 1 28. 4 28. 7 29. 4 MOISTURE CONTENT 1 136. 8 98.0 51. 9 20.0 12. 0 OF PAPER (%) 2 158. 2 144.7 125. 1 76.2 39. 7 3 171. 5 168.8 176. 6 140.3 119. 8 4 178. 1 176.8 183. 1 180.3 174. 9 5 181. 9 183.1 189. 6 190.1 189. 7 T A B L E I V A P P L I C A T O R E F F I C I E N C Y FOR WET P A P E R D R Y I N G E X P E R I M E N T NUMBER (WATER WETTED) 1 2 3 .4. . . . . .5. POWER I N P U T ( k c a l / h r ) 602 1170 1936 2323 2538 WATER P I C K - U P ( k g / h r ) 6.19 3.20 3.32 3.33 3.31 T O T A L E V A P O R A T I O N ( k g / h r ) 0.79 1.49 2.40 2.97 3.10 ENERGY FOR E V A P O R A T I O N ( k c a l / h r ) 429 832 1408 • . 1773 1883 S E N S I B L E HEAT OF PRODUCT ( k c a l / h r ) 92 87 50 17 22 T O T A L ABSORBED ENERGY ( k c a l / h r ) 521 . 919 1458 1790 1905 E F F I C I E N C Y BASED ON E V A P O R A T I O N {%) 71.2 71.1 72.7 76.3 74.2 E F F I C I E N C Y B A S E D ON A B S O R B E D ENERGY (%) 86.5 78.5 75.3 77.1 75.1 57 a c h i e v e d by s e t t i n g the v a l v e i n the exhaust a i r l i n e so t h a t the manometer r e a d i n g a c r o s s the o r i f i c e i n t h e e x i t l i n e from t h e fa n was c o n s t a n t . However, because the temperature and m o i s t u r e content o f the e x i t a i r changed by d i f f e r e n t amounts depending on the energy l e v e l s u p p l i e d by the magnetron and because the f a n was drawing a more o r l e s s c o n s t a n t volume o f e x i t a i r t h r o u g h i t s e l f , the mass f l o w r a t e o f a i r d e c r e a s e d as the power l e v e l r o s e . R e l a t i v e h u m i d i t i e s were measured i n the o u t l e t . a i r p i p e but because a l o t o f condensate was o b s e r v e d t h e s e were not used ' i n the heat and mass b a l a n c e c a l c u l a t i o n s . I n subsequent work, hot a i r s h o u l d be used and the waveguides and a i r p i p e s i n s u l a t e d . S u r f a c e temperatures were measured at f i v e p o s i t i o n s ( b e f o r e and a f t e r each waveguide) from the wet end t o the dry end. P o s i t i o n 5 i s b e f o r e the f i r s t waveguide the wet paper e n t e r s and p o s i t i o n 1 i s a f t e r the l a s t waveguide the dry paper l e a v e s . I t i s p o s s i b l e t h a t the s u r f a c e thermocouples are a f f e c t e d by the presence o f microwave l e a k a g e from the s l o t s l e a d i n g t o a h i g h e r r e a d i n g t h a n the a c t u a l s u r f a c e t e m p e r a t u r e . T h i s was checked by r e a d i n g the thermocouples w i t h no paper i n the s l o t s and the microwaves o f f . Then the microwaves were t u r n e d on and t h e thermocouples r e a d . T h i s p r o c e d u r e r e s u l t e d i n as much as a 3°C i n c r e a s e i n the thermo-c o u p l e r e a d i n g . The g r e a t e s t e f f e c t was at the dry end waveguide which was n e a r e s t t h e microwave s o u r c e . W i t h a d i e l e c t r i c i n the waveguide, .leakage of r a d i a t i o n would p r o b a b l y be g r e a t e s t where the most energy was b e i n g absorbed. An attempt was made t o . o b s e r v e thermocouple r e a d i n g s w i t h paper i n the s l o t s but not moving but t h i s s t a r t e d the paper on f i r e . The m o i s t u r e c o n t e n t o f the sheet was measured b e f o r e and a f t e r each waveguide o f the system. These r e s u l t s are p l o t t e d i n 58 2 0 0 10 2 0 3 0 POWER GENERATION (kw) Moisture Content versus Power Generation (Drying of Water Wetted Paper) 59 0 10 2 0 3 0 POWER GENERATION (kw) Figure 17 . Relative Moisture Content versus Power Generation (Drying of Water Wetted Paper) 1000 < o 1 -J 1 1 I 2 3 4 (DRY END) POSITION F i g u r e 1 8 . Absorbed. E n e r g y v e r s u s P o s i t i o n ( D r y i n g o f W a t e r W e t t e d P a p e r ) F i g u r e 16 a g a i n s t p o w e r l e v e l . H o w e v e r t h e o r i g i n a l m o i s t u r e c o n -t e n t s w e r e n o t t h e same i n e a c h o f f i v e e x p e r i m e n t s , s o t h e s e c u r v e s w e r e r e p l o t t e d i n F i g u r e 17 b y d i v i d i n g e a c h m o i s t u r e c o n t e n t b y t h e o r i g i n a l m o i s t u r e c o n t e n t . T h e e n e r g y a b s o r b e d i n e a c h w a v e g u i d e i s p l o t t e d i n F i g u r e 18 a s a f u n c t i o n , o f a b s o r b e d p o w e r l e v e l . T h i s f i g u r e s h o w s t h a t a t l o w p o w e r l e v e l s m o s t o f t h e e n e r g y i s a b s o r b e d i n t h e d r y e n d w a v e g u i d e ( N o 1 w a v e g u i d e ) w h i c h i s t h e o n e c o u p l e d t o t h e m a g n e t -r o n . H o w e v e r , ' b e y o n d a c e r t a i n p o w e r l e v e l m o r e e n e r g y i s c o n s u m e d i n w a v e g u i d e No.2. I f s u f f i c i e n t p o w e r w e r e a v a i l a b l e p r e s u m a b l y t h i s p r o g r e s s i o n w o u l d c o n t i n u e u n t i l t h e b u l k o f t h e e n e r g y a b s o r b e d w o u l d b e a b s o r b e d i n t h e w e t w a v e g u i d e . I n t h e 2.9.5kw e x p e r i m e n t m o r e e n e r g y w a s a b s o r b e d i n w a v e g u i d e No.2 e v e n t h o u g h t h e p o w e r i n t e n s i t y w o u l d b e h i g h e r i n w a v e g u i d e No. 1. H o w e v e r , s i n c e t h e m i c r o w a v e e n e r g y i s s e l e c t i v e l y a b s o r b e d b y t h e w a t e r a n d . t h e w a t e r c o n t e n t o f s h e e t was h i g h e r i n w a v e g u i d e No.2 t h a n i n N o . l a n d t h e a b s o l u t e l e v e l o f m o i s t u r e i n t h e s h e e t w a s l o w i n w a v e g u i d e N o . 1 t h i s i s n o t s u r p r i s i n g . N o t e a l s o f r o m T a b l e I I I t h a t t h e s u r f a c e t e m p e r a t u r e a t t h e d r y e n d w a v e g u i d e i s r e l a t i v e l y l o w . T h u s h e a t d a m a g e t o t h e s h e e t i s m i n i m i z e d b y t h i s k i n d o f d r y i n g . b ) D r y i n g o f R e s i n I m p r e g n a t e d P a p e r S i m i l a r e x p e r i m e n t s w e r e p e r f o r m e d u s i n g r e s i n i m p r e g n a t e d p a p e r . T h e r e s u l t s - o f t h e s e a r e g i v e n i n T a b l e s V a n d V I . T h e b a s e p a p e r was i m p r e g n a t e d w i t h a 33-7% p h e n o l - f o r m a l d e -h y d e r e s i n s o l u t i o n a n d d r i e d a t one of 5 m i c r o w a v e p o w e r l e v e l s . T h e p a p e r f e e d r a t e was m a i n t a i n e d c o n s t a n t a t 21.2 m e t e r s p e r j 6 2 T A B L E V D R Y I N G DATA FOR R E S I N I M P R E G N A T E D P A P E R O P E R A T I N G C O N D I T I O N E X P E R I M E N T NUMBER ( R E S I N ) 1 . • . 2 .... 3 . .4 . 5 FORWARD POWER ( k w ) 0. 70 1. 00 1. 20 1. 40 1. 81 R E V E R S E POWER ( k w ) 0. 01 .0. .03. 0. 05 0. 05 0. Oi POWER G E N E R A T I O N ( k w ) 0. 9 6 1. 37 1. 75 2. 02 2. 4' S U P P L Y CURRENT (a m p ) 10. 5 14. 0 19. 6 21. 2 24. 0 WATER FLOW RATE ( k g / h r ) 36. 0 33. 0 34. 0 . 33. 5 37. 5 I N L E T TEMP. (°C) 13. 2 12. 0 12. 0 12. 7 15. 3 O U T L E T TEMP. (°C) 35. 7 46. 0 55. 0 63. 0 6 5 . 9 WET A I R FLOW R A T E ( k g / h r ) 1 8 9 . 6 185- 5 1 7 5 - 4 . 1 6 8 . 4 1 5 6 . 5 DRY A I R FLOW R A T E ( k g / h r ) 1 8 3 . 8 1 7 9 . 0 .167. 9 - 1 5 9 . 4 145. 5 DRY B U L B TEMP. (°C) 36. 2 37. 7 42. 0 45. 3 5 2 . 0 WET B U L B TEMP. (°C) 32. 8 35. 0 38. 4 41. 8 47. 0 H U M I D I T Y ( k g / k g ) 0.0307 0.0354 0.0431 0.0528 0.0708 ROOM T E M P E R A T U R E : (°C) 2 9 . 2 2 9 - 2 2 8 . 4 3 . 1 . 6 3 1 . 8 R E L . H U M I D I T Y (%) 6 1 . 5 6 1 . 5 61. 6 5 8 . 7 •56. 3 ATM. P R E S S U R E (mmHg) 756. 8 756. 7 754. 0 754. 0 754. 0 S U R F A C E TEMP. 1 6 9 . 3 72. 7 72. 3 81. 5 152. 7 OF P A P E R (°C) 2 32. 6 35. 0 57. 4 5 8 . 5 63. 4 3 26. 7 2 7 . 7 30. 9 33. 3 6 9 . 6 4 24 . 5 ' 26. 2 2 5 . 0 27. 7 29. 9 5 2 3 . 5 26. 0 2 3 . 0 2 6 . 9 . 2 7 . 2 M O I S T U R E CONTENT 1 91. 5 71. 0 1 9 . 6 7. 8 2. 0 OF P A P E R •{%) 2 140. 1 131. 5 80. 8 7 8 . 4 11. 9 3 137. 5 146. 4 135- 2 141. 5 9 6 . 3 • 4 138. 7 139. 3 138. 4 1 5 4 . 3 1 3 9 . 5 : 5 142. 5 150. 5 1 4 6 . 0 152. 4 149. 6 TABLE VI APPLICATOR EFFICIENCY FOR RESIN IMPREGNATED PAPER DRYING EXPERIMENT NUMBER (RESIN) 1 2 3 4 5 POWER INPUT (k c a l / h r ) 825 1178 1505 1738 2107 RESIN PICK-UP (kg/hr) 0 .70 0.76 0.74 0.77 0.76 WATER PICK-UP (kg/hr) 2.49 2.82 2.55 2.67 2.57 TOTAL EVAPORATION (kg/hr) 0.73 1.40 2.38 • 2.53 2.56 ENERGY FOR EVAPORATION (k c a l / h r ) 516 787 1261 1471 1566 SENSIBLE HEAT OF PRODUCT (kc a l / h r ) 92 115 59 65 133 TOTAL ABSORBED ENERGY (k c a l / h r ) 608 902 1326 1542 1699 EFFICIENCY BASED ON EVAPORATION (%) 62.5 66.8 83.8 84.9 . 74.3 EFFICIENCY BASED ON ABSORBED ENERGY (%) 73-7 76.5 88.1 88.7 80.6 OA L.O 64 Pigure 19. R e l a t i v e Moisture Content versus Power Generation (Drying of Resin Impregnated Paper) 65 1000 ( D R Y END) POSITION Figure 20. Absorbed Energy versus P o s i t i o n (Drying of Resin Impregnated Paper) 66 hour f o r a l l experiments. The r e s i n p i c k up of the paper r e -mained more or l e s s constant. The r e s i n content was measured as o u t l i n e d i n Se c t i o n IV-3 The moisture content was determined at each sampling position and was used In the energy balances. Pigure 19 i s a p l o t of the r e l a t i v e moisture content i n each waveguide at various a p p l i e d power l e v e l s . Over heating of the paper was observed at the highest power l e v e l a p p l i e d . This r e s u l t e d i n a d i s c o l o u r e d and weaken-ed sheet; t h i s w i l l be commented on i n l a t e r s e c t i o n s . This was not observed when dr y i n g paper wetted only w i t h water at even higher power l e v e l s . This may mean that there i s considerable absorption of microwave energy not only by the water but al s o by the phenol-formaldehyde r e s i n i t s e l f . Note that when d r y i n g the water impregnated sheet the dry end sheet temperature was around 60°C at an a p p l i e d power l e v e l of 2.95 KW but when dr y i n g the r e s i n impregnated sheet the dry end temperature was 153°C at a power l e v e l of only 2.45 KW. In t h i s p a r t i c u l a r r u n , d i s - . coloured (presumably over heated) zones appeared every h a l f wave-leng t h across the width of the sheet. This suggested the presence of a standing wave i n the waveguide wi t h the points of highest i n t e n s i t y causing the over heating. E l i m i n a t i o n of t h i s standing wave would re q u i r e staggered waveguides, angled wave-guides, or some type of mechanical mode mixer. Figure 20 i s a p l o t of the energy absorbed i n each wave-guide which shows s i m i l a r trends to those shown by f i g u r e 18. However, i n the 1.37 KW experiment an apparently f a u l t y moisture content measurement between waveguides No.3 and No.2 has r e -s u l t e d i n erroneous absorbed energy l e v e l s i n these waveguides. 67 So the 1.37 KW curve, i s probably not very r e l i a b l e . c) Convective Drying E f f e c t . To check the e f f e c t s of a i r flow I n the absence of micro-waves s e v e r a l runs were made w i t h water saturated paper passing through the waveguides at 21.2 meter/hr. and a v a r i e t y of a i r flow r a t e s . . Table V I I shows as might be expected, a s l i g h t tendency to increased d r y i n g as the paper passed from the wet to the dry end of the apparatus but no s i g n i f i c a n t e f f e c t of a i r flow r a t e was noted over the range 0 Kg/hr to 300 Kg/hr. In i n d u s t r i a l systems hot air, and higher flow r a t e s would probably be used. Thus i t would be u s e f u l to study mass t r a n s f e r rates as a f u n c t i o n of a i r flow r a t e s i n the presence of micro-waves. However, t h i s would r e q u i r e a d i f f e r e n t design of apparatus i n which temperature, a i r v e l o c i t y , and humidity measurements could be made. This was not p o s s i b l e i n the present equipment. In f a c t i t i s a problem to make measurements i n microwave f i e l d s w ith m e t a l l i c devices and with devices con-s t r u c t e d of m a t e r i a l s which conduct microwaves because of the f i e l d d i s t o r t i o n s they cause. 2. Product Q u a l i t y Tests a) Tension Tests The t e n s i o n or t e n s i l e s t r e n g t h t e s t procedures were out-l i n e d i n Section IV-4. The r e s u l t s of the t e n s i l e breaking s t r e s s t e s t s are presented i n Table V i l l i the r e s u l t s of the s t r e t c h at breaking appear i n Table IX; and the r e s u l t s of the measurement of Young's modulus are given i n Table X. Not s u r p r i s i n g l y the t e n s i l e breaking s t r e n g t h of the r e s i n 68 TABLE VII CONVECTIVE EFFECT OF VENTILATION AIR EXPERIMENT NUMBER (CONVECTION) 1 2 3 4 5 PAPER FEED RATE (m/hr) 21.2 21.2 21.2 21.2 21. 2 AIR FLOW RATE (kg/hr) 0 190 242 .. 256 303 AIR TEMPERATURE (°C) 22.7 21.0 21.8 22.3 22.3 REL. HUMIDITY (58) 82.2 76.9 73.3 72.0 74.3 ATM. PRESSURE (mmHg) 756.8 754.0 754.0 . 756.8 756.8 SURFACE TEMP. OF PAPER 1 21.0 18.5 20.0 19.5 20.0 2 21. 0 19.0 20.0 20.5 20.5 3 21.0 19.0 20.0 20.0 20.5 4 21.0 19. 0 20.0 20.0 20.0 5 21.0 19.5 20.0 20. 0 20.0 MOISTURE CONTENT 1 1.86 1.87 1.81 1.80 1.80 OF PAPER (%) 2 1.96 1.94 2. 09 1.73 1.87 3 1.93 1.86 1.85 1.88 2 .00 4 1.89 1.84 1.85 2.00 2.03 69 impregnated paper i s greater than that of the base paper. Also as i s w e l l known, the machine d i r e c t i o n s t r i p s are stronger than the cross machine d i r e c t i o n s t r i p s . S t a t i s t i c a l l y about a l l one can say i s that the best micro-wave d r i e d group (2.02. KW) i s stronger than the best oven d r i e d group (120°.C) i n the' machine d i r e c t i o n . But t h i s i s not seen i n the cross machine d i r e c t i o n s t r i p s . So i n general one can conclude that microwave drying has no advantage over'conventional d r y i n g as f a r as t e n s i l e s t r e n g t h i s concerned. • I t should be noted however that both excessive microwave drying (2.45 KW) and excessive oven d r y i n g (170°C) degrade the s t r e n g t h of the paper. The s t r e t c h at breaking t e s t s present no s i g n i f i c a n t evidence that microwave d r y i n g i s b e t t e r or worse than convention-a l d r y i n g . The cross machine s t r e t c h seems to be reduced by the presence of r e s i n and as would be a n t i c i p a t e d f o r conventional papers the cross machine d i r e c t i o n s t r e t c h i s higher than the machine d i r e c t i o n s t r e t c h . The Young's modulus r e s u l t s p a r a l l e l those of the t e n s i l e breaking strength and s t r e t c h . b) I n t e r n a l Bond Test The i n t e r n a l bond t e s t ( s e e S e c t i o n IV-6) r e s u l t s are presented i n Table XI. In these t e s t s 5 r e p l i c a t e samples were t e s t e d i n each group.. However, because of the capacity l i m i t of the t e s t -2 i n g machine a v a i l a b l e (equivalent to 70 Kg/cm ) many of the samples could not be broken. So the number of samples broken and the average breaking s t r e s s are reported. In future work smaller samples or a t e s t i n g machine of greater c a p a c i t y should be used. The r e s u l t s of. Table XI do suggest that the microwave d r i e d 70 TABLE V I I I TENSION TEST DATA (TENSILE BREAKING STRENGTH) TENSILE BREAKING STRENGTH (kg/cm ) DRYING CONDITION MACHINE DIRECTION C-MACHINE DIRECTION AVERAGE STD.DEV. AVERAGE STD.DEV. 0.96 290.3 13.4 224.6 6.2 M.W. POWER 1.37 318.5 12.1 200.0 7.0 LEVEL (kw) 1.75 313-3 15.7 210.7 7.4 2.02 352.0 12.1 207.1 5-7 2.45 266.3 21.2 194.2 • 18.7 OVEN DRYING 120 302.5 8.1 231.1- 5-7 TEMP. (°C) 170 281.6 15.3 213.7 9-9 BASE PAPER 198.2 5.6 113.4 3.3 TABLE IX TENSION TEST DATA (STRETCH) STRETCH {%) DRYING CONDITION MACHINE DIRECTION C-MACHINE DIRECTION AVERAGE STD.DEV. AVERAGE STD.DEV. 0.96 1.45 0.14 1.87 0.09 M.W. POWER 1.37 1.78 0.11 2. 20 0.12 LEVEL (kw) 1.75 1.49 0.11 2.00 0.13 2.02 1.87 0.08 1.81 0.09 2.45 1.41 0.05 •1.08 0.13 OVEN DRYING 120 1.92 0.09 2.07 0.11 TEMP. ( 0 C) 170 1.39 0.11 1.18 0. 08 Base Paper 1.78 0.05 4.69 0.33 TABLE X TENSION TEST DATE (YOUNG'S MODULUS) 71 YOUNG'S MODULUS x 10 4 (kg/cm 2) DRYING CONDITION MACHINE DIRECTION C-MACHINE DIRECTION AVERAGE STD.DEV. AVERAGE STD.DEV. 0.96 1.150 0. 314 0. 743 0.019 M.W. POWER 1.37 0.937 0. 024 0. 678 0.027 LEVEL (kw) 1.75 1. 049 0. 024 0. 682 0.017 2.02 0.902 0. 031 0. 707 . 0.023 2.45 0.909 0. 078 0. 781 0.013 OVEN DRYING 120 0.749 0. 022 0. 653 0.017 TEMP. (° C) 170 0.949 0. 029 0. 800 0.014 BASE PAPER 0.775 0. 022 0. 424 , 0.029 72 sheets have b e t t e r i n t e r n a l bond than do the sheets d r i e d c o n v e n t i o n a l l y at 17Q°C. Note that .17Q°C i s t y p i c a l of i n d u s t r i a l p r a c t i c e . I f one had a more uniform r e s i n d i s -t r i b u t i o n one would expect a higher i n t e r n a l bond because the non uniform r e s i n d i s t r i b u t i o n would leave a weak plane i n the centre of the sheet. This t e s t i s one piece of evidence then that the r e s i n impregnated paper d r i e d by microwaves has a more uniform r e s i n d i s t r i b u t i o n . c) Surface Abrasion Test The surface abrasion t e s t (see Se c t i o n IV-7) r e s u l t s are presented i n Table X I I and f i g u r e 21. The d a t a ' i n Table X I I are the averages of d u p l i c a t e samples. The r e s u l t s i n d i c a t e that the microwave d r i e d sheets have gr e a t e r abrasion r e s i s t a n c e than the c o n v e n t i o n a l l y d r i e d at 170°C sheets. Not only i s the o v e r a l l r e s i s t a n c e b e t t e r but i t i s more uniform; t h a t i s the slope of the curves i s l e s s steep f o r the microwave d r i e d papers suggesting that they have a more uniform r e s i n d i s t r i b u t i o n . The 2.45 KW samples are not as good as the others probably because of over h e a t i n g . The appearance of. t h i s sample suggested over heating. However, the oven d r i e d sample had a normal appearance. These r e s u l t s are another piece of evidence that microwave d r i e d papers have a more uniform r e s i n d i s t r i b u t i o n . They are (23) i n agreement w i t h those of Takahashi et a l . i n that the micro-wave d r i e d sheets show a f l a t a b rasion r a t e vs number of abrasion c y c l e s p l o t . However, our r e s u l t s have a g e n e r a l l y higher wear rat e and do not show a maximum i n the oven d r i e d samples. 73 TABLE XI INTERNAL BOND TEST DATA DRYING CONDITION INTERNAL BOND STRENGTH (kg/cm 2) NUMBER OP FAILED SAMPLES 0.96 45.9 5/5 M.W. POWER 0.96 70.0 1/5 LEVEL (kw) 2.02 57.3 1/5 2.45 57.7 3/5 OVEN DRYING 170 33.2 5/5 TEMP. (°C) TABLE X I I SURFACE ABRASION TEST DATA \ ABRASION. RATE (inches / 1 0 cycles) . CYCLES M.W. POWER LEVEL (kw) 1 OVEN DRYING 0. .96 1. 75 2 ( 02 I 2, • 45 170 °C 500 1. .3 1. 2 1 I \2 1. .3 2 • 9 1000 1. .2 1. 5 1 2 1. • 7 2 • 3 1500 1. .5 1. 4 1 .6 2, .0 2 .5 2000 1. .3 1. 6 1 •15 2. .6 3 .4 2500 1. .8 1. 6 1 .17 2. .6 3 .7 3000 1. • 9 1. 8 1 v7 3. .2 4 .4 . 3500 2. , 1 1. 8 • 2 .'0 3. ,4 4 .4 4000 1. • 9 1. 6 1 .7 2. ,8 _ 4500 2. .1 1. 7 2 .3 3-,8 — 5000 1. • 9 1. 8 1 .7 5500 1. 4 2 .0 i Y 74 5 0 -£40 O o a 3-0 CO < cr < 10 r SYMBOL kw O 096 T I70°C A-A OVEN • • -0 20 4 0 60 ABRASION CYCLES x IO"3 Figure 21. Surface Abrasion Rate versus Abrasion Cycles 75 d) Paper Bending Test The r e s u l t s , of the paper, bending t e s t which was performed as described In S e c t i o n IV-5 are recorded i n Table X I I I . These measurements were done on machine d i r e c t i o n s t r i p s only because of b u c k l i n g which seemed to occur w i t h cross machine d i r e c t i o n s t r i p s . Data comparisons using the student t t e s t showed no advantage of microwave d r i e d paper over c o n v e n t i o n a l l y d r i e d paper. The 170°C c o n v e n t i o n a l l y d r i e d paper and the 2.45 KW microwave d r i e d papers were s i g n i f i c a n t l y weaker i n bending than the other papers implying that they were more b r i t t l e . 3. Resin D i s t r i b u t i o n The resin d i s t r i b u t i o n was determined by s e c t i o n i n g the sheet and removing the c e l l u l o s e i n h y d r o f l u o r i c a c i d . About s i x s l i c e s were shaved, from each sample which amounted to about h a l f the sheet. The shavings were analyzed f o r r e s i n content and the r e s u l t s appear i n Table XIV. L i g n i n content was neglected (see Section IV-8). In Table XIV the r e s u l t s of one commercial pro-duct a n a l y s i s are a l s o reported. This one was done using s u l -f u r i c a c i d i n s t e a d of h y d r o f l u o r i c a c i d . A l l the r e s i n d i s -t r i b u t i o n data are p l o t t e d i n f i g u r e 22 where r e s i n content i s p l o t t e d against distance from the sheet surface. The sheets were around 0.4 mm i n t h i c k n e s s . I t was assumed that the r e s i n d i s t r i b u t i o n was symmetrical about the centre of the sheet. I t i s apparent from f i g u r e 22 that the r e s i n concentration p r o f i l e s are f l a t t e r f o r the microwave d r i e d sheets than f o r the oven d r i e d sheets. The 2.45 KW curve i s not as f l a t as the TABLE ; X I I I PAPER BENDING TEST DATA DRYING CONDITION BREAKING ANGLE (degree) AVERAGE STD.DEV. 0.96 193 4.27 M.W. POWER 1.37 188 6.99 LEVEL (kw) 1.75 181 3.45 2.02 187 2.05 2.45 146 6.01 OVEN DRYING 120 187 3.90 TEMP. (°C) 170 148 5.29 TABLE XIV RESIN CONTENT DISTRIBUTION (RESIN CONTENT %) AVERAGE DISTANCE FROM THE SURFACE (mm) DRYING CONDITION 0.017 Q.051 0.085 0.119 0.153 1.187 0.96 34.9 33.8 33.5 33.9 35.4 36.3 M.W. POWER 1 . 3 7 45.3 41.7 45.5 44.1 39.1 38.2 LEVEL (kw) 1.75 4S.4 45.7 45.8 42.2 42.9 39.9 2 .02 46.8 50.0 45.8 45.1 45.5 39.3 2. 45 51.6 48.8 - 46.7 43.8 39.9 OVEN DRYING 120 43.1 44.9 42.9 38.3 32.5 28.4 TEMP. (°C) 170 45.3 37.0 38.2 31.9 24.6 17.8 COMMERCIAL PRODUCT . 33.4 32.9 25.3 21.4 22.7] 18 .7 (REICHHOLD CHEMICALS) — j 78 TABLE XV RESIN PICK UP OP MICROWAVE DRIED PRODUCTS M.W. POWER RESIN ANALYSIS RESIN PICK UP LEVEL (kw) (SECTIONING EXPT.) (DRYING EXPT.) RESIN CONTENT RESIN PICK UP k g / k S paper (%) kg/kg paper 0.96 34.6 0.529 0 . 7 2 1 1.37 42.3 0.529 0 . 7 2 1 1.75 43.7 0.775 0.740 2.02 45.4 0.831 0.775 2.45 46.1 0.856 ' 0.764 7 9 |0 1 - J ! 0 01 0-2 (SURFACE) (MIDDLE) DISTANCE (mm) Figure 22. Resin Content D i s t r i b u t i o n 80 other, microwave d r i e d sheets.. These r e s u l t s , support those ob-t a i n e d i n the abrasion r e s i s t a n c e and i n t e r n a l bond tests, (see Sections V-2c and V-2d. They are also i n agreement w i t h the (23)" photographs presented by Takahashi et a l . Table XV" compares the t o t a l sheet r e s i n content measured as o u t l i n e d i n S e c t i o n V - l w i t h the t o t a l sheet r e s i n content measured i n the s e c t i o n i n g experiment. In 3 out of 5 of these the agreement between the two methods Is reasonable but at the lowest (0.96 KW) and highest (2.45 KW) l e v e l s there i s s u f f i c i e n t disagreement f o r concern. In the low power l e v e l sample the s e c t i o n i n g a n a l y s i s gives a lower r e s i n content than the t o t a l a n a l y s i s . However, at the high power l e v e l the opposite i s t r u e . One would t h i n k that losses i n the s e c t i o n i n g experiment might lead to lower values of t o t a l r e s i n content but higher r e -s u l t s cannot be immediately explained. Table XIV shows that the r e s i n content of the sheet i n -creases as the a p p l i e d microwave power l e v e l increases but the t o t a l sheet r e s i n content measured at the wet end stays more or l e s s the same. This may i n d i c a t e that the microwave r a d i a t i o n or perhaps merely the higher temperature has something to do w i t h the polymerisation process. More fundamental work should be done i n t h i s area. 4. Product Appearance Resin impregnated papers must be acceptable to the consumers of these products and i n c e r t a i n uses (e.g. p r i n t e d wood g r a i n overlays f o r f u r n i t u r e manufacture) v i s u a l appearance i s important. In t h i s work no systematic s t a t i s t i c a l comparisons of product 8 1 appearance" were made but some noteworthy e f f e c t s were ob-served. When paper i s impregnated w i t h r e s i n i t looks r a t h e r patchy. That i s there are areas which are d i s c e r n a b l y more t r a n s l u c e n t than others. This i s probably due to non uniform impregnation w i t h r e s i n . When such a sheet i s d r i e d In a conventional d r y i n g process t h i s patchiness can s t i l l be observed. But when such a ' sheet was microwave d r i e d i t appeared to be much more uniform. This tendency i s shown i n f i g u r e s 23c ahd 23d. Figures 23a, b, and d are of microwave d r i e d products, photograph c i s an oven d r i e d paper (170°C). One could speculate that In the microwave d r i e d paper, due to the volume hea t i n g ( i n t e r n a l heat generation) e f f e c t , that the temperature r i s e s r a p i d l y throughout the sheet lowering the v i s c o s i t y of the r e s i n emulsion and producing a f a s t e r and more uniform p e n e t r a t i o n of the sheet. In convective d r y i n g the heating up process i s slower and m a t e r i a l at the surface may be polymerised before uniform p e n e t r a t i o n i s achieved. In a waveguide i t i s p o s s i b l e to e s t a b l i s h a standing wave p a t t e r n . I f the m a t e r i a l being d r i e d i s completely transparent to microwaves t h i s need not be a problem provided s u f f i c i e n t energy i s a v a i l a b l e . However, t h i s i s an i d e a l i z a t i o n . Resin impregnated papers c o n t a i n non v o l a t i l e r e s i n and some bound water d i f f i c u l t to remove. In removing these l a s t t r a c e s of water the temperature w i l l rise more at those p a r t s of the wave where the energy a p p l i e d I s most i n t e n s e . This tends to heat up the paper e x c e s s i v e l y at these p o i n t s . The same a p p l i e s apparent-l y to the phenolic r e s i n which heats up co n s i d e r a b l y . 82 PHENOL-FORMALDEHYDE RESIN IMPREGNATED PAPER MICROWAVE DRIED 2 45KW. 34 SEC. RESIN PICK UP 0764 MICROWAVE DRIED 270 KW, 17 SEC. RESIN PICK UP 0721 ELEC. OVEN DRIED I70*C. 5 SEC. RESIN PICK UP 0 684 MICROWAVE DRIED 2 02 KW, 34 SEC. RESIN PICK UP 0775 figure 23 Photocraphs of Resin Impregnated Papers 83 Figure 23a shows a r e s i n Impregnated paper d r i e d at the 2.45 KW power l e v e l . The residence, time of t h i s , paper i n the waveguide was 34 sec. It's f i n a l moisture content was 2.0$.. The over heated zones are obvious. These zones appear every h a l f wavelength suggesting that a standing wave i s the cause. These e f f e c t s were not observed v i s u a l l y i n d r y i n g paper wetted with water or f o r r e s i n Impregnated papers at lower power l e v e l s but equal residence times ( f i g u r e 23d). The sheet shown i n f i g u r e 23d had a f i n a l moisture content of 7.8$. ' These e f f e c t s were also not observed at higher power l e v e l s (2.70 KW) but lower r e t e n t i o n time (16 sec) as evidenced by f i g u r e 23b. One explan-a t i o n i s that at high enough temperatures the r e s i n i s o x i d i z e d . These sheets (2.45 KW) were weaker than the others d r i e d at lower power l e v e l s (see Section V ). In commercial u n i t s mode mixing devices could be t r i e d to eli m i n a t e t h i s problem or the sheet could be d r i e d to a higher moisture content. When t h i s equipment was designed i t was assumed that a l l evaporated water would be c a r r i e d away as vapor by the v e n t i l a t i o n a i r . However, during the experiments condensate was observed i n the waveguides. Some of t h i s water dripped onto the surface of the paper causing a s t a i n . I t was f e l t that a r c i n g could be caused by these drops and t h i s could cause a burn or scorch mark on the paper. This problem could be e l i m i n a t e d by using higher a i r flow r a t e s or by using heated v e n t i l a t i o n a i r . At high power i n t e n s i t i e s s p o t t i n g of the paper "surface was evident ( F i g u r e 23b ' ). These spots;were l u s t r o u s , and r e s i n r i c h . They only occurred at power l e v e l s of over 2.5 KW and only f o r a few inches from the side of the waveguide nearest the power source. No reason f o r t h i s can be advanced. Further study w i t h h i g h speed photographs during d r y i n g might shed some l i g h t on t h i s . The problem could probably be e l i m i n a t e d by using s e v e r a l low power a p p l i c a t o r s i n s t e a d of one high power a p p l i c a t o r . 85 VI - CONCLUSIONS 1) Resin impregnated papers can tie d r i e d by microwave absorption. 2) Over the range of v a r i a b l e s studied the average a p p l i c a t o r e f f i c i e n c y was around 74$. The e f f i c i e n c y of the microwave power generator ranged from 70 to 90%. g i v i n g o v e r a l l e f f i c i e n c i e s of 50 to 70%. 3) C e r t a i n product appearance defects were noted w i t h r e s i n im- • pregnated papers d r i e d w i t h microwaves. The sheets wi t h the worst appearance were considerably weakened by the drying process. This was a t t r i b u t e d to over dr y i n g . However, under l e s s severe d r y i n g c o n d i t i o n s the microwave, papers appeared to be more u n i -form. 4) No s i g n i f i c a n t d i f f e r e n c e s were observed i n the t e n s i l e and bending behaviour of resin'Impregnated papers when compared to s i m i l a r papers d r i e d i n a n a t u r a l convection oven. The micro-wave d r i e d papers were b e t t e r i n terms of abrasion r e s i s t a n c e and i n t e r n a l bond str e n g t h . 5) A r e s i n content d i s t r i b u t i o n a n a l y s i s was performed by e x t r a c t -ing the c e l l u l o s e from the r e s i d u a l r e s i n by h y d r o f l u o r i c a c i d a f t e r s e c t i o n i n g the sheets on a l a t h e . The microwave d r i e d sheets gave a more uniform r e s i n d i s t r i b u t i o n p r o f i l e than the co n v e n t i o n a l l y d r i e d papers. 86 VII - REFERENCES 1. McAdams, ¥.H.Lewis, W. K., and Adams, F. W. , Paper Trade J o u r n a l '8_4(l8), 61 (1927.) 2. Sherwood, T. K., Ind. Eng. Chem. 21, 976 (1929) 3. Ceaglske, N. H., and Hougen, 0. A., Ind. Eng. Chem. 2_9, 805 (1937) 4. Corben, R. W., and Newitt, D. M., Trans. I n s t n . Chem. Engrs. 33, 52 (1955) 5. D r e s h f i e l d , A. C , and Han, S. T., Tappi 39.(7), 499 (1956)' 6. Harmathy, T. Z., Ind. Eng. Chem. Fundamentals 8, 92 (1969) 7. Kauh, J . Y., Ph.D. Thesis, I l l i n o i s I n s t i t u t e of Technology, (1966) 8. Nissan, A. H. , and Hansen, D., Tappi 4_3_(9), 753 (I960) 9. Nissan, A. H., and Hansen, D., A.I.Ch.E. J o u r n a l 6(4), 606 (I960) 10. Nissan, A. H., and Hansen, D. , Tappi ^44(8), 529 (1961) 11. Nissan, A. H., George, H. H., and Hansen, D., Tappi 45.(3), 213 (1962) 12. Snow, R. H., IITRI Report NO. C8081-4, IIT Research I n s t i t u t e (1966) 13. Goerz, D. J . , and J o l l y , J . A., The Jo u r n a l of Microwave Power 2, 87 (1967) 14. Gardner, T. A., P r e p r i n t , Symposium on Water Removal, Canadian Pulp and Paper A s s o c i a t i o n (1968) 15. Damskey, L. R., Hankin, J . W., and Stephansen, E. W., The J o u r n a l of Microwave Power 4, 294 (1969) 16. Voss, W. A. G., IEEE Transactions on Industry and General A p p l i c a t i o n 2(3), 234 (1966) 17. Lewin, L., 'Advanced Theory of Waveguides", I l i f e and Sons, London, (1951): 18. A l l a n , G. B.,. M.Sc. The s i s , The U n i v e r s i t y of A l b e r t a , (1967) 87 19. Asami, :Y., Research I n s t i t u t e , of Applied E l e c t r i c i t y . Report, Hokkaido University., Japan, (1958) 20. de Loor, G. P.,' The' Jo u r n a l of Microwave Power 3, 67 (1968) 21. Tinga, W. R., The Jo u r n a l of Microwave Power 4_, 162 (1969) 22.. L e i d i g h , W. J . ,' Stephansen, E. W. , and S t o l t e , W. J . , I n t e r n a t i o n a l Microwave Power I n s t i t u t e Fourth Symposium, Edmonton, (1969) 23. Takahashi, K., V a s i s h t h , R. C., and Cote', W. A., The Jo u r n a l of Microwave Power 4_, 64 (1969) 24. S e l l e r , C. J . , Tappi 44_(10), 172A (1961) 25. Marton, R., and Crosby, C. M., Tappi 52(4), 68l (1969) 26. S i c o n o l f i , C. A., Tappi 43.(3), 152A (i960) 27. S e i f e r t , K., Holz a l s Roh und Werkstoff 16, 335 (1958) 28. Tappi Standards and Suggested Methods, T 222 os-54 A c i d - i n s o l u b l e L i g n i n i n Wood Pulp 29. E t t l i n g , B. F., and Adams, M. F., Forest Products J o u r n a l 16(6), 26 (1966) 30. Berkeley, D. E., B.A.Sc. Thesis, The U n i v e r s i t y of B r i t i s h Columbia, (1968) 31. Birenbaum, L., Kaplan,I. T., Metlay, W., Rosenthal, S. W., Schmidt, H., and Zaret, M. M., The Jo u r n a l of Microwave Power 4, 232 (1969) 32. Crapuchettes, P. W. , The Jo u r n a l of Microwave Power 4_, 137 (1969) 33. Tappi Standards and Suggested Methods, T 404. ts-66 "Tensile Breaking Strength of Paper and Paperboard" 34. Canadian Standard A s s o c i a t i o n , CSA-0188-6'7 "Measurment of I n t e r n a l Bond Strength" 35. TICO B u l l e t i n NO. 6504-1M "TABER Model 503 Abraser I n s t r u c t i o n Manual" NEMA Standard, NO. 8-2Q-1962 '. "Method of Test f o r Resistance of Surface to Wear" Galloway, L. R.,'Ph.D. The s i s , The U n i v e r s i t y of B r i t i s h Columbia, (I963) 89 V I I I - NOMENCLATURE 1. Drying Theory. Cp H i H 2 K c Kr k M P s P w r T T a T c T f X x y y y a 0 X a f s p e c i f i c heat heat t r a n s f e r c o e f f i c i e n t ( c y l i n d e r - sheet i n t e r f a c e ) heat t r a n s f e r c o e f f i c i e n t (sheet - f e l t i n t e r f a c e ) kcal/(kg)(°C) kcal/(m2)(hr)(°C) k c a l / ( m )(hr)(°C) conductance of pulp f o r l i q u i d water kg/(m)(hr)(atm) c o e f f i c i e n t of evaporation-conden-s a t i o n mechanism kg/(m)(hr)(atm) thermal c o n d u c t i v i t y moisture content c a p i l l a r y pressure vapor pressure of water dimensionless distance temperature a i r temperature c y l i n d e r temperature f e l t temperature sheet thickness distance through thickness mole f r a c t i o n of water i n bulk a i r mole f r a c t i o n of water i n f e l t mole f r a c t i o n of water at sheet surface (r=o) mole f r a c t i o n of water at sheet surface ( r = i ) 2 thermal d i f f u s i v i t y m /hr time hr heat of evaporation kcal/kg-mole kcal/(m)(hr)(°C) kg/nr atm atm °C °c ° c ° c m m p density Microwave Theory d E. l E^ f n P. 1 W a £ e I £2 e' £» w £ > > 1 0 p 1 P2 p e n e t r a t i o n depth i n c i d e n t e l e c t r i c f i e l d d e nsity t r a n s m i t t e d e l e c t r i c f i e l d densuty frequency mixing c o n d i t i o n absorbed power density i n c i d e n t power density t r a n s m i t t e d power density weight r a t i o of component 2 to component 1 a t t e n u a t i o n constant complex p e r m i t t i v i t y complex p e r m i t t i v i t y of component 1 complex p e r m i t t i v i t y of component 2 d i e l e c t r i c constant d i e l e c t r i c constant of water d i e l e c t r i c l o s s f a c t o r i n t r i n s i c wave impedance of free space density of component 1 density of component 2 cm volts/m volts/m Hz • (-) watts/cm watts/cm^ 3 watts/cm -1 m farads/m farads/m farads/m farads/m farads/m farads/m 3 7 7 ohms 3 gr/cm 3 gr/cm A - l APPENDIX A Power Meter C a l i b r a t i o n The c r y s t a l type forward and reverse power meter (EIMAC EW3 - D P M 3 ) was c a l i b r a t e d using the water load as a c a l o r i m e t e r . This power meter was mounted i n the waveguide between the microwave a p p l i c a t o r and the water load. To c a l i b r a t e the power meter the microwave power l e v e l was set a some value and the c o o l i n g water flow rate through the water load and i t s i n l e t and o u t l e t temperatures were recorded. The power consumed was c a l c u l a t e d from the temperature r i s e and correlated with the d i f f e r e n c e between the forward and reverse power meter readings. T o t a l supply current and V a r i a c s e t t i n g were a l s o recorded f o r correlation with the energy absorbed i n the water load. The data obtained are recorded i n Table A-I. In f i g u r e A - l the net power absorbed i s p l o t t e d against the d i f f e r e n c e between forward and reverse power meter reading. Two d i f f e r e n t curves r e s u l t e d one f o r each range of the power supply. Since the behaviour of the water load and the power meter should not depend on the power supply c i r c u i t to the magnetron t h i s was unexpected. The only explanation that comes to mind i s that some mismatching between the magnetron and the waveguide occurs when the range switch i s changed or that the power meter i s some-how a f f e c t e d by t h i s change. The net power-absorbed i s p l o t t e d against t o t a l supply current i n f i g u r e A-2 and against Variac s e t t i n g i n f i g u r e A-3. Thus these parameters can a l s o be used as power generation i n d i c a t o r s as w e l l as the power meter. T o t a l power su p p l i e d was c a l c u l a t e d from the t o t a l supply k-2 current and supply voltage assuming the supply voltage was 115 v. The e f f i c i e n c y of the microwave power generator was then c a l c u l a t e d and p l o t t e d i n f i g u r e A-4. The o v e r a l l e f f i c i e n c y of the complete d r y i n g process i s the product of power supply e f f i c i e n c y and d r y i n g e f f i c i e n c y . Figure A-5 shows the time r e q u i r e d f o r the microwave generator system to achieve steady s t a t e . In c o l l e c t i n g the data f o r these curves the Variac s e t t i n g and the c o o l i n g water flow rate were maintained constant. The f i g u r e shows that about 2 hours are re q u i r e d to reach steady sta t e a f t e r s w i t c h i n g on the magnetron. Curves a and c were obtained when the magnetron was on continuously and curve b was obtained when the magnetron was switched on, a reading taken, and then turned o f f u n t i l the next reading was made. Data f o r the curves of f i g u r e A-5 are given i n Table A - I I . A-3 POWER METER READING (kw) (FORWARD—REVERSE) Figure A - l . Power Generation versus Power Meter Reading A-4 30 •ZL 2-0 o fe o 10 UJ CL 0 0 10 20 30 SUPPLY CURRENT (amp) Figure A-2. Power Generation versus Supply Current B I 8 0 50 100 VARIAC SETTING (-) Figure A-3. Power Generation versus Var i a c S e t t i n g a- 0 10 2 0 3 0 POWER GENERATION (kw) Figure A-4V Power Supply E f f i c i e n c y versus Power Generation A-7 1-5-g < 0 o 0 5 o 0 — O " VARIAC SETTING 75 (H RANGE) b / A VARIAC SETTING 130 A (H RANGE) A J / A —• / n^CT VARIAC SETTING 70 / (L RANGE) 20 0 30 60 90 TIME ( m i n ) Pigure A-5. Start-up Time f o r Microwave Generator TABLE A - l a POWER METER CALIBRATION DATA (LOW RANGE) POWER METER WATER WATER TEMPERATURE POWER VARIAC SUPPLY SUPPLY EFFICI-READING (kw) PLOW RATE (°C) GENERATION SETTING CURRENT POWER ENCY FORWARD REVERSE (kg/hr) INLET OUTLET (kw) (-) (amp) (kw) (%) 0.100 0.000 41.0 12.2 15.0 0.13 99 — — — 0.200 0.002 41.0 12 . 2 18.3 0.26 90 3.0 0.35 75.4 0.300 0.003 41.7 - 12.2 20.8 0.41 80 5.0 0.58 70.7 0.400 0 .005 41.7 12.2 23.5 0.55 72 6.5 0.75 73.5 0.500 0.010 41.2 12.2 26.6 0.71 . 62 7.8 0.90 78.9 0.600 0.010 41.7 12 .2 29-9 0.86 '54 • 9.1 1.05 81.9 o. 700 0.015 42.0 12.2 32.3 0.98 46 10.4 . 1.20 81.7 0.800 0. 020 41.7 12.0 34.5 1.09 38 11.5 1.32 82.6 0.900 0.020 42.0 12.0 37.2 1.23 31 12.6 1.45 84.8 1. 000 0.025 43.0 12.0 39.1 1.35 20 13.8 1.59 84.9 > I co TABLE A-lb POWER METER CALIBRATION (HIGH RANGE) POWER METER WATER WATER TEMPERATURE POWER VARIAC SUPPLY SUPPLY EFFICI-READING (kw) FLOW RATE (°C) GENERATION SETTING CURRENT POWER ENCY FORWARD REVERSE (kg/hr) INLET OUTLET (kw) (-) (amp) (kw) (*) 1. 000 0. 030 40.2 12.2 44.2 1.50 123 16.5 1.90 78.9 1.100 0.040 39.5 12.2 47.0 1.61 118 17.5 2.01 80.1 1. 200 0.45 39-5 12.2 49.9 1.76 113 18.6 2 .14 82.2 1.300 0.050 39-2 12.2 52.9 1.87 108 19.5 2.24 83.5 1.400 0.055 39.2 12.2 56.2 2. 02 101 20.5 2.36 85.6 1. 500 0.060 39.5 12.2 58.5 2.14 • 95 21.5 2.47 86.6 1.600 0.065 40.8 12.2 59.7 2.26 90 22.5 2.59 87.3 1.700 0.070 40.4 12 .2 62 .2 2. 36 85 23.2 2.67 88.4 1. 800 0.070 39.5 12.2 64.5 ' 2.44 80 24.0 2.76 88.4 1.900 0.070 39.5 12 .2 67.7 2.59 75 25.0 2.88 89.9 2.100 0.065 40.2 12.2 70.9 2.69 68 26.6 3.06 87.9 2.200 0.065 41.5 12.5 72.5 2.77 64 27. 2 3-12 88.8 2.300 0.075 40.2 13.2 74.6 2.9o 57 27.6 3.17 91.8 2.400 0.075 40.2 13.2 76.4 2.98 53 28.2 3-24 92.0 A-10 TABLE A-2a START-UP TIME FOR MICROWAVE GENERATOR (VARIAC SETTING IN HIGH RANGE 75) TIME POWER METER READING (kw) SUPPLY CURRENT (min) , FORWARD . REVERSE.. DIFFERENCE. (amp) 0 1.13 0.03 1.10 18.1 10 1.26 0.04 1.22 19.3 20 1.35 0.04 1. 31 20.1 30 1.40 0. 04 1.36 20.6 50 1.49 0.05 1.44 21. 7 70 1.52 0.05 1.47 22.3 100 1.52 0.05 1.47 22.5 120 1.52 0.05 1.47 22.5 TABLE A-2b START-UP TIME FOR MICROWAVE GENERATOR (VARIAC SETTING IN HIGH RANGE 130) TIME POWER METER READING (kw) SUPPLY CURRENT (min) FORWARD REVERSE DIFFERENCE (amp) 0 0.20 0.0 0.20 5.1 5 0.32 0.0 0.32 6.4 10 0.43 0.01 0.42 7-8 20 0.53 0.01 0.52 9-7 30 "0.65 0.02 0.63 11.4 40 0.75 0.02 0.73 12.8 50 0.85 0.02 0.83 14.8 60 0.90 0.03 0.87 14.8 70 0.93 0.03 0 .90 15.0 80 0.96 0.03 0.93 15.5 90 0.98 0.03 0.95 15.9 100 0.99 0.03 O.96 15.9 110 1.02 0.03 0.99 16.5 A - l l TABLE A-2c. START-UP TIME FOR MICROWAVE GENERATOR (VARIAC SETTING IN LOW RANGE 70). TIME POWER METER READING (kw) SUPPLY CURRENT (min) FORWARD REVERSE DIFFERENCE (amp) 0 0.10 0.0 0.10 3.0 10 0.13 0.0 0.13 • 3-5 20 0.24 0.0 0.24 4.5 30 0.26 0.0 0 .26 4.5 40 0. 30 0.0 0.30 5.0 60 0.32 0.01 •' 0.31 • 5-5 70 0.34 0.01 0.33 5-5 80 0.35 0.01 0.34 5-7 90 0.35 0.01 0.34 5.8 110 0.37 0 .02 0.35 6.1 130 0.37 0.02 0.35 6.0 B APPENDIX B Rotameter Calibration Figure B - l and Table B-I are the data collected for calibrating the Brooks Rotameter R-6-15A used in controll ing the cooling water flow rate. This was done for two water tem-peratures 12°C and 1 7 ° C No temperature effect was observed. B -2 TABLE B - l ROTAMETER CALIBRATION DATA ROTAMETER WATER PLOW WATER SETTING RATE (kg/hr) TEMP.(°C) 2 5 . 2 3 . 4 1 7 . 0 3 1 . 5 5 . 3 1 7 . 0 42 . 0 8 . 6 1 7 . 0 5 4 . 0 1 2 . 1 1 7 . 0 61 . 5 14 . 4 1 7 . 0 7 2 . 0 1 7 . 8 1 7 . 0 84 . 0 2 2 . 0 1 7 . 0 9 6 . 0 2 5 - 7 1 7 . 0 1 0 2 . 0 2 8 . 0 1 7 . 0 1 1 3 . 5 3 2 . 6 1 7 . 0 124 . 5 3 6 . 2 1 7 - 0 1 3 4 . 0 3 9 . 6 1 7 . 0 2 2 . 0 2 . 5 1 2 . 0 3 7 - 0 7 . 0 1 2 . 0 5 4 . 2 1 2 . 0 1 2 . 0 6 9 . 7 1 6 . 9 1 2 . 0 8 8 . 5 2 3 - 0 1 2 . 0 1 0 3 . 0 2 8 . 2 1 2 . 0 1 1 5 . 0 3 3 . 1 12 . 0 1 2 5 . 0 3 5 . 4 1 2 . 0 1 3 7 - 0 40 . 2 1 2 . 0 Figure B - l . Rotameter C a l i b r a t i o n Curve APPENDIX C C-l Thermocouple C a l i b r a t i o n The copper constantan thermocouples were c a l i b r a t e d using a quartz thermometer. The c a l i b r a t i o n data i s presented i n Tables C-I and. C-II. The maximum e r r o r due to reading of the recorder chart was estimated to be - 0 . 2°C. C-2 TABLE C - l SURFACE THERMOCOUPLE CALIBRATION DATA (THERMOCOUPLE NO.1 TO NO.5) TEMPERATURE POTENTIAL DIFFERENCE (mV) ( ° c ) . N O . l NO. 2 N0.3 NO. 4 NO. 5 11.1 0.44 0,44 . 0.44 0.44 0.44 19.9 0.78 0.78 . 0.78 0.7.8 0.78 29.8 1.18 1.18 1.18 1.18 1.18 4Q. .5 1.63 1.63 1.63 1.63 1.63 50.7 2.06 2.06 2.06 2.06 . 2.06 60.6 2.49 2.49 2.48 2. 49 2 49 70.4 2.90 2.90 2.90 2.90 2.90 81.2 2.39 2.39 2.38 2.39 2.38 91.1 3.85 3.85 3.83 3.85 3.85 96.0 4.07 4.07 4.07 4.07 4.05 TABLE C-2 THERMOCOUPLE CALIBRATION DATA (THERMOCOUPLE NO. 6 TO NO'. 9 ) TEMPERATURE POTENTIAL DIFFERENCE (mV) (°C) NO. 6 NO. 7 • NO. 8 NO. 9 21.2 0.87 0.86 0.86 0.86 30.0 1.24 1.23 1.23 1.23 40.1 1.67 1.65 1.65 1.65 50.1 2.11 2.10 2.09 2.09 60.0 2.55 2.55 2.54 2.53 70.1 2.99 2.99 2.97 2.97 80.0 . 3.48 3.46 3-45 3.43 90.0 3.95 3.93 3.91 3.88 APPENDIX D O r i f i c e Meter A three i n c h standard o r i f i c e meter was i n s t a l l e d i n the e x i t l i n e from the fan which v e n t i l a t e d the waveguide. This was used to set the a i r flow r a t e . . The a i r flow rates were c a l c u l a t e d from W = KA 0 V 2 S C (Pi - P 2 ) P 0 where K = discharge c o e f f i c i e n t . (-) 2 A 0= cross s e c t i o n a l area of the o r i f i c e ( f t ) p0= density of the f l u i d at the o r i f i c e (gm/cm^) W = mass flow r a t e (lb/sec) P 1 - P 2 = pressure drop"across the o r i f i c e = 2.048Ah op b Q ( l b f / f t 2 ) A h 0 = manometer l e v e l d i f f e r e n c e (cm) P.bo manometer f l u i d density (gm/cm^) The o r i f i c e discharge c o e f f i c i e n t s were taken from the t h e s i s (34) of Galloway who used and c a l i b r a t e d t h i s p a r t i c u l a r o r i f i c APPENDIX E Sample C a l c u l a t i o n f o r Heat Balance Sample c a l c u l a t i o n was done f o r experiment No. 3 of r e s i n impregnated paper d r y i n g t e s t . (1) Power Input C a l c u l a t i o n forward power from power meter = 1.20 kw reverse power from power meter = 0.05-kw d i f f e r e n c e of forward-reverse power = 1.15 kw power generation = 1.75 kw (from f i g u r e A - l) (2) Moisture Content and Resin P i c k up C a l c u l a t i o n paper feed speed = 21.24 m/hr width of paper web = 0.4l m p density of paper = 0.201 kg/m paper feed r a t e = (21.24)(0.4l)(0.201)=1. 75 kg/h moisture content and r e s i n p i c k up at p o s i t i o n 5 (wet end) concentration of r e s i n s o l u t i o n = 33-67$ weight of wet sample = 11.20 gr weight of oven d r i e d sample = 6.09 gr evaporated water = 11.20 - 6.09 = 5-11 gr weight of r e s i n = ( ° j ^ 3 ^ ^ 1 1 ) = 2.59 gr weight of paper = 11.20 - (5-11+2.59) 3.50. gr 2 59 i r e s i n p i c k - u p = 2 5 0 = 0-74 g r / g r - p a p e r 5 11 m o i s t u r e c o n t e n t = i.' nr. x 100 = 146.0 % 3 • 50 . m o i s t u r e c o n t e n t and r e s i n p i c k up at p o s i t i o n 4 weight o f sample = 4.46 gr weight o f oven d r i e d sample = 2.48 gr weight o f water = 4.46-2.48 = 1.98 g r r e s i n p i c k - u p =0.74 (from wet end data) ? 48 weight o f paper = 1 Q ^ = 1.43 gr m o i s t u r e c o n t e n t = J743" x 1 0 0 = 138.4 % S i m i l a r c a l c u l a t i o n was done f o r each p o s i t i o n . R e s u l t s were g i v e n as f o l l o w s : -P o s i t i o n 1 2 3 4 5 sample weight 6.11 5.73 7.54 4.46 11.20 oven d r i e d weight 5.49 3-91 4.24 2.48 6.09 weight o f water 0.62 1.82 3-30 1.98 5.H weight of r e s i n 2.33 1.66 1.80 1.05 2.59 weight o f paper . 3.16 2.25 2.44 1.43 3-50 r e s i n p i c k - u p - ' - - - 0.74 m o i s t u r e c o n t e n t 19.6 80.8 135.2 138.4 • 146.0 E-3 (3) Energy C a l c u l a t i o n f o r Evaporation evaporation at p o s i t i o n 1 (dry end waveguide) moisture content d i f f e r e n c e = O..808 - 0.196 = 0.612 kg-water/kg-paper water evaporation = (0.612)(1.75) = 1.07 kg/hr paper temperature at p o s i t i o n 5 = 23-0°C paper temperature at p o s i t i o n 1 = 72.3°C s p e c i f i c heat of water = 1.0 kcal/(kg)(°C) heat of v a p o r i z a t i o n . o f water = 555 k c a l / k g (at 72.3°C) energy f o r evaporation = (1.07) {(1.0)(72.3 - 59.4) + 555} = 609 k c a l / h r S i m i l a r c a l c u l a t i o n was done f o r each p o s i t i o n . Results were given as f o l l o w i n g : -Waveguide Water Energy f o r No. Evaporation Evaporation (kg/hr) ( k c a l / h r ) • 1 dry 1.071 609 2 0.952 505 3 0.056 53 4 wet 0.133 97 t o t a l 2.212 1261 (4) Energy C a l c u l a t i o n for, Sensible Heat s p e c i f i c heat of paper = 0.30 kcal/(kg)(°C) s p e c i f i c heat of r e s i n = 0.40 kcal/(kg)(°C) (assumed) E-4 paper t e m p e r a t u r e at p o s i t i o n 5 =23.0 °C paper t e m p e r a t u r e at p o s i t i o n 1 = 72.3 °C s e n s i b l e heat o f paper = (1. 7 5 ) ( 0 . 3 0 ) ( 7 2 . 3 - 23.0) = 25.9 k c a l / h r s e n s i b l e heat o f r e s i n = ( 1 . 7 5 ) ( 0 . 7 4 ) ( 0 . 4 0 ) ( 7 2 . 3 - 23.0) = 2 5 -5 k c a l / h r s e n s i b l e heat o f w a t e r i n p r o d u c t = (1.75)(0.196)(1.0)(72.3 - 23.0) 13.5 k c a l / h r t o t a l s e n s i b l e heat 25.9 + 25.5 + 13.5 64.9 k c a l / h r (5) E f f i c i e n c y o f A p p l i c a t o r energy i n p u t = (1.75)(860.5 ) = 1.505 k c a l / h r (1 kw = 860.5 k c a l / h r ) e f f i c i e n c y based on e v a p o r a t i o n 1,261 ' 1,505 x 100 = 83.8 % e f f i c i e n c y based on t o t a l energy a b s o r p t i o n 1,261 + 64.9 1,505 x 100 = 88.0 % 

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