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Studies on the crystallinity of wood cellulose fibres by X-ray methods. Lee, Chi-Long 1960

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STUDIES ON THE CRYSTALLINITY OF WOOD CELLULOSE FIBRES BY X-RAY METHODS by CHI-LONG LEE B.S.F. Taiwan Prov. C o l l . of Agr., China, 1955 A THESIS SUBMITTED IF PARTIAL FULFILMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF FORESTRY i n the Faculty of Forestry We accept t h i s thesis as conforming to the required standard THE UNIVERSITY OF BRITISH COLUMBIA A p r i l , i 9 6 0 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 th e r e q u i r e m e n t s f o r an advanced degree a t the U n i v e r s i t y o f B r i t i s h Columbia, I agree t h a t the L i b r a r y s h a l l make i t f r e e l y a v a i l a b l e f o r r e f e r e n c e and s t u d y . I f u r t h e r agree t h a t p e r m i s s i o n f o r e x t e n s i v e c o p y i n g o f t h i s t h e s i s f o r s c h o l a r l y purposes.may be g r a n t e d by t h e Head o f my Department 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 or p u b l i c a t i o n o f t h i s t h e s i s f o r f i n a n c i a l g a i n s h a l l not be a l l o w e d w i t h o u t my w r i t t e n p e r m i s s i o n . Department o f Forestry  The U n i v e r s i t y of B r i t i s h Columbia, Vancouver 3, Canada. Date March 25. 1960  j i ABSTRACT I t was the purpose of t h i s study to compare pulps prepared from normal, sound wood w i t h those prepared from j u v e n i l e wood, compression wood, t e n s i o n wood and decayed wood w i t h regard to t h e i r apparent degree of c r y s t a l l i n i t y . The c r y s t a l l i n i t y index and c r y s t a l l i n i t y r a t i o of the pulps prepared from these woods ?;ere determined by two d i f f e r e n t X-ray methods. In method A, the p r i n c i p l e of the Debye-Scherrer powder technique was a p p l i e d and the c r y s t a l l i n i t y index of the pulp was evaluated from the 002 peak of the X-ray d i f f r a c t i o n p a t t e r n . In method B a Geiger-counter X-ray spectrometer was used and the c r y s t a l l i n i t y r a t i o of h o l o c e l l u l o s e was evaluated from the (101 +101) combination peak. I t was found that the apparent c r y s t a l l i n i t y of wood pulp and h o l o c e l l u l o s e prepared from normal western hemlock wood increased s i g n i f i c a n t l y through successive growth r i n g s from the p i t h to about 15 years, a f t e r which i t reached a more or l e s s constant value. The c r y s t a l l i n i t y of wood pulp and h o l o c e l l u l o s e of summerwood was s i g n i f i c a n t l y higher than that of springwood. The c r y s t a l l i n i t y of wood pulp and h o l o c e l l u l o s e of compression wood from Douglas f i r was considerably lower than that of normal wood, whereas the c r y s t a l l i n i t y of t e n s i o n wood from cottonwood was i l s i g n i f i c a n t l y higher than that of normal wood. The c r y s t a l l i n i t y of cottonwood and Douglas f i r h o l o c e l l u l o s e increased s i g n i f i c a n t l y during the i n c i p i e n t stage of decay. The r a t e of increase i n c r y s t a l l i n i t y was very r a p i d during the i n c i p i e n t stage of decay represented by a s i x percent weight l o s s , but became very slow and showed an almost constant value t h e r e a f t e r . The r e l a t i v e value of c r y s t a l l i n i t y a f t e r decay depends mainly on the i n i t i a l c r y s t a l l i n i t y r a t h e r than the h i s t o r y of decay. i l l ACKNOWLEDGEMENT The author wishes to express h i s sincere gratitude to the Faculty of Forestry of the University of B r i t i s h Columbia, and to Dr. R.W. Wellwood under whose d i r e c t i o n t h i s study was c a r r i e d out; to Mr. R.W. Kennedy for his careful review and c r i t i c i s m of the manuscript and for providing some experimental material; to Dr. J.H.G. Smith for suggesting a s t a t i s t i c a l design; to Dr. L.D. Hayward for discussions i n the planning stage; to Dr. J.A.F. Gardner and Mr. W.V. Hancock of the Vancouver Laboratory, Forest Products Laboratories of Canadaj Dr. V.G. G r i f f i t h s , Dr. E. Teghtsonian, and Mr. Y.I. Ssu of the Department of Mining and Metallurgy at the University of B r i t i s h Columbia and Mr. G.E. Breeze and Mr. R.H. M l b e r g of the Department of Physics, B r i t i s h Columbia Research Council f o r permission to use th e i r . equipment and for t h e i r kind assistance and cooperation i n many ways; and to the National Research Council of Canada for the studentship grant under which th i s work was completed. i v TABLE OF CONTENTS PAGE I. INTRODUCTION 1 I I . CRYSTALLINE STRUCTURE AND CRYSTALLINITY OF CELLULOSE 4 A. Chain structure and formation of the c r y s t a l l i n e region 5 B. L a t t i c e structure 7 C. C r y s t a l l i n i t y of c e l l u l o s e 11 1. Concept , 11 2 . Determination of c r y s t a l l i n i t y . . . . . 14 (a) Chemical methods 15 i ) Acid hydrolysis method . . . 15 i i ) Deuteration method 17 i i i ) Cellulose derivative method 18 iv) Oxidation method 19 v) Iodine sorption method . . . 20 (b) Physical methods . 21 i ) X-ray method 21 i i ) Moisture regain method . . . 25 i i i ) Infra-red absorption spectroscopy method . . . . 26 iv) Density method 28 3 . Treatments a f f e c t i n g c r y s t a l l i n i t y . . . 29 (a) Hydrolysis 29 (b) Heat 30 V PAGE (c) Mechanical d e e r y s t a l l i z a t i o n . . . . 31 (d) Degradation by microorganisms . . . 32 (e) L a t t i c e t r a n s i t i o n 33 i ) T r a n s i t i o n from c e l l u l o s e I to c e l l u l o s e I I 33 i i ) T r a n s i t i o n from c e l l u l o s e I to c e l l u l o s e I I I 34 i l l ) T r a n s i t i o n from c e l l u l o s e I I and I I I t o c e l l u l o s e IV . 35 ( f ) P u l p i n g 35 (g) S t r e t c h i n g 36 4 . R e l a t i o n s h i p between c r y s t a l l i n i t y and p r o p e r t i e s of c e l l u l o s e 36 (a) Young's modulus 37 (b) T e n s i l e strength 38 (c) E l o n g a t i o n 39 (d) Alpha c e l l u l o s e content 39 (e) S w e l l i n g and dimensional s t a b i l i t y . 40 I I I . EXPERIMENTAL METHOD 42 A. M a t e r i a l s 42 B. S t a t i s t i c a l design 43 C. P r e p a r a t i o n of samples 44 1. Wood pulp sample . 45 2 . H o l l o c e l l u l o s e 46 D. X-ray c o l l i m a t i n g system and procedure . . . 47 v i PAGE 1. Method A 47 2. Method B . . . . 50 E. Evaluation of c r y s t a l l i n i t y 52 1. C r y s t a l l i n i t y index 52 2 . C r y s t a l l i n i t y r a t i o 53 IV. RESULTS AND DISCUSSION 54 A. Part I: The degree of c r y s t a l l i n i t y of pulp and holocellulose of normal wood . . . 54 1. Results 54 (a) Tensile strength 59 (b) Alpha-cellulose content 59 (c) Moisture regain 60 2. Probable mechanism of v a r i a b i l i t y of c r y s t a l l i n i t y i n wood 62 B. Part I I : The degree of c r y s t a l l i n i t y of pulp and holocellulose of reaction wood as compared to normal wood 63 1. Results 63 2 . Compression wood 65 3 . Tension wood 66 C. Part I I I : The degree of c r y s t a l l i n i t y of holocellulose of decayed wood 69 1. Results 69 2. Biochemical transformation of c e l l u l o s e . 73 3 . Preference of enzymic attack 75 v i i PAGE 4. Relationship between l a t e r a l order and rate of enzymic attack 77 V. CONCLUSIONS 82 VI. BIBLIOGRAPHY 84 v i i i LIST OF TABLES TABLE PAGE 1. The unit c e l l structure of c e l l u l o s e 11 2. Relationship between alpha-cellulose content and c r y s t a l l i n i t y . 40 3» Va r i a t i o n i n c e l l u l o s e properties as c r y s t a l l i n i t y increases . 41 4 . E f f e c t of age and season on c r y s t a l l i n i t y of wood pulp and holocellulose 55 5. Analysis of variance of c r y s t a l l i n i t y i n Table 4 57 6. C r y s t a l l i n i t y of reaction wood 64 7. Analysis of variance of c r y s t a l l i n i t y i n Table $ 64 8. C r y s t a l l i n i t y r a t i o of holocellulose of decayed wood 70 9 . Analysis of variance of c r y s t a l l i n i t y r a t i o i n Table 8 70 10. Stepwise biochemical transformation of c e l l u l o s e 74 i x LIST OF FIGURES FIGURE PAGE 1. Unit c e l l of c e l l u l o s e I 9 2. Camera arrangement for the Debye-Scherrer powder technique . 48 3' E f f e c t of X-ray exposure time on c r y s t a l l i n i t y index 48 4. Wood pulp X-ray diagram 49 5. Spectrometer geometry 51 6 . X-ray d i f f r a c t i o n spectrum 51 7. V a r i a t i o n of c r y s t a l l i n i t y with age and season 5& 8. X-ray d i f f r a c t i o n spectra of Douglas f i r holocellulose 71 9 . E f f e c t of decay and type of wood on c r y s t a l l i n i t y r a t i o of holocellulose . . . 72 10. Schematic l a t e r a l order d i s t r i b u t i o n curve and sequence of enzymic attack on the c r y s t a l l i n e region 8 l INTRODUCTION The e f f e c t of c r y s t a l l i n i t y on physical and chemical properties of c e l l u l o s e and i t s derivatives has been studied extensively during the past few years, p a r t i c u l a r l y during the l a s t decade. Rapid developments i n equipment, as well as improvement i n precise techniques, have made such kinds of studies f r u i t f u l i n adding valuable information to knowledge of c e l l u l o s e chemistry. Most of these works deal with pulp or cotton c e l l u l o s e , but only a l i m i t e d number of papers deal with the c r y s t a l l i n i t y of wood i n the l i g h t of the re s u l t s with cotton c e l l u l o s e , yet i t may be one of the important factors which w i l l d i r e c t l y or i n d i r e c t l y a f f e c t wood properties and q u a l i t y . The main d i f f i c u l t i e s i n studying c r y s t a l l i n i t y of wood are caused by the complicated chemical composition of wood i t s e l f . I t i s well known that wood contains only about 50 to 60 percent of c e l l u l o s e . In order to determine the c r y s t a l l i n i t y q u a n t i t a t i v e l y , the chemical constituents other than c e l l u l o s e should be removed. Since there i s no method which can extract components other than c e l l u l o s e without degrading c e l l u l o s e molecular chains, the experimental value of c r y s t a l l i n i t y determined from such c e l l u l o s e can hardly be considered the same as that which a c t u a l l y existed i n the o r i g i n a l wood. However, i f the same chemical treatment i s applied to d i f f e r e n t types of wood assuming a uniform degree of degradation of the 2 ce l l u l o s e molecular chains during the treatment, i t may be possible to compare the r e l a t i v e degree of c r y s t a l l i n i t y among wood samples. Based on t h i s premise, studies on c r y s t a l l i n i t y of wood f i b r e s have been made by various workers. The c r y s t a l l i n i t y of Cross and Bevan c e l l u l o s e prepared from wood of d i f f e r e n t ages was studied by Preston, Hermans, and Weidinger (113) by means of an X-ray method. Results showed that the c r y s t a l l i n i t y decreased with age. An opposite r e s u l t was obtained by Taniguchi (142), who found that absolute c r y s t a l l i n e c e l l u l o s e content of Pinus d e n s i f l o r a , as determined by an acid hydrolysis method, increased with age slowly i n the early stage of growth. Because of these d i f f e r e n t r e s u l t s observed, further study was deemed necessary i n order to ascertain the v a r i a b i l i t y of c r y s t a l l i n i t y with age of wood. Lindgren (77) has pointed out that the summerwood gives a sharper X-ray diagram, which indicates a higher degree of c r y s t a l l i n i t y as compared with the corresponding springwood. A similar r e s u l t was observed by Holzer and Lewis (57)» who claimed that the summerwood f i b r e s exhibited an unusually high degree of preferred orie n t a t i o n among the c r y s t a l l i t e s , whereas springwood f i b r e s were found to be much more amorphous. Numerical data were not given by these workers. The c r y s t a l l i n i t y of tension wood has been studied thoroughly by Wardrop and Dadswell (154,157)• A s i g n i f i c a n t l y 3 high degree of c r y s t a l l i n i t y of tension wood, as compared with that of normal wood, was found to be due to the existence of an ad d i t i o n a l layer inside the inner layer of the secondary c e l l w a l l . To the writer's knowledge, the c r y s t a l l i n i t y of the other type of reaction wood, compression wood,.has not been studied. The r e l a t i o n s h i p between c r y s t a l l i n i t y and micro-b i o l o g i c a l degradation of c e l l u l o s e has been studied by various workers. Most of these works are confined to pure c e l l u l o s e which has been treated with enzymes, but l i t t l e i s known about the r e l a t i o n s h i p between c r y s t a l l i n i t y and wood decay. C r y s t a l l i n i t y of decayed wood was f i r s t studied by Kohara and Okamoto ( 7 1 ) . They found a higher degree of c r y s t a l l i n i t y i n the old timbers taken from ten old Buddhist temples ( i n use about 300 to 13OO years) as compared with that of new timbers. But the v a r i a t i o n i n c r y s t a l l i n i t y of decayed wood as related to the stage of decay s t i l l remains unknown. The purposes of t h i s thesis are to quantit a t i v e l y study (1) the v a r i a t i o n i n c r y s t a l l i n i t y of wood from a young tree with age, (2) the degree of c r y s t a l l i n i t y of summerwood as compared with that of springwood, (3) the c r y s t a l l i n i t y of reaction wood as compared with that of normal wood, and (4) the rela t i o n s h i p between c r y s t a l l i n i t y and wood decay. CRYSTALLINE STRUCTURE AND CRYSTALLINITY OF CELLULOSE As early as 1913> Nishikawa and Ono (104) showed that the X-ray diagram of c e l l u l o s e consisted of d e f i n i t e d i f f r a c t i o n r i n g s . This discovery led to the concept of c r y s t a l l i n i t y of f i b r e s . Nishikawa (105) l a t e r pointed out that the c r y s t a l l i z e d areas were not continuous, but separated by more or less disordered material. Extensive research, both physical and chemical, has been car r i e d out since then, but the concept remains the same. Today, i t i s s t i l l considered that c e l l u l o s e , l i k e other high polymers, w i l l c r y s t a l l i z e under proper conditions to form an imperfectly ordered s o l i d , having c e r t a i n regions possessing a high degree of i n t e r n a l geometrical order known as c r y s t a l l i t e s . The remainder w i l l possess disordered entangled chain molecules known as amorphous regions. As the s i z e , shape, arid degree of perfection i n the c r y s t a l l i n e region, or the degree of randomness In the amorphous region, are never constant from sample to sample, the physical and chemical properties of c e l l u l o s e and i t s derivatives are correspondingly v a r i a b l e . In order to understand the c r y s t a l l i n i t y relationships of c e l l u l o s e , a b r i e f review i s necessary of the c r y s t a l l i n e structure and c r y s t a l l i n i t y of c e l l u l o s e . 5 A. Chain structure and formation of the c r y s t a l l i n e region To est a b l i s h the chain structure of c e l l u l o s e , studies on quantitative y i e l d s of glucose units from c e l l u l o s e were i n i t i a t e d , followed by inv e s t i g a t i o n of the nature of hydroxyl groups and p o s i t i o n of hydroxyl groups i n c e l l u l o s e . From these works i t was concluded that pure c e l l u l o s e consisted exclusively of glucose residues (66,93) which contained three hydroxyl groups at the second, t h i r d , and s i x t h carbon atom (27,67)» and the basic unit was found to be the anhydroglucose unit ( 110) . Nature of the linkage between these anhydroglucose units was studied by various physical and chemical methods, and f i n a l l y a s p a t i a l model of c e l l u l o s e was constructed by Meyer and Mark (110). This model had the beta form of o Haworth's cellobiose (110) with unit length of 10.3 A. o Distance between carbon atoms was found to be 1.54- A, whereas o that between carbon and oxygen atoms was 1.35 A. .One ha l f of the unit i s turned through 180 degrees to f u l f i l l the screw axis requirement which allows the 1 , 4-linkage. The molecular chain thus formed by anhydroglucose units i s nearly s t r a i g h t , with a degree of polymerization of several thousand glucosidic r i n g s . These extend l o n g i t u d i n a l l y i n the d i r e c t i o n of the f i b r e a x i s , with a small angle of i n c l i n a t i o n . When a l l molecular chains extend i n thi s manner, a cross-wise secondary force w i l l be formed. Because of t h i s 6 interchain force, the molecular chains w i l l a t t r a c t one another to form a well-ordered region or a c r y s t a l l i n e region. Such c r y s t a l l i z a t i o n cannot take place completely throughout the whole chain. It occurs at the p a r t i c u l a r region where the intermolecular a t t r a c t i o n i s strongest, and chain molecules are f i t t e d l a t e r a l l y into a c r y s t a l l a t t i c e . The other region w i l l remain i n a disordered state even though weak secondary a t t r a c t i o n forces exist among them. This region i s referred to as the amorphous region. I t must be pointed out that not only the length of such c r y s t a l l i z e d portions i s variable, but also the i n t e r v a l distance between them i s changeable from one type of c e l l u l o s e to another. The molecular chains i n wood c e l l u l o s e , which may have a degree of polymerization of more than 3»000 glucose o O units (145)» are approximately l 5 x l 0 - ) A i n length, whereas a c r y s t a l l i t e has an order of magnitude of 1.4x10° A (145). l f the amorphous region, on the average, i s assumed to be shorter than the c r y s t a l l i n e region, then each molecular chain must pass through about ten microphases or, i n other words, consists of several c r y s t a l l i n e and amorphous regions. This concept was postulated f i r s t by Frey-lAfyssling (35) and Kratky (74), and led to the fringe micellar theory. As f a r as the crystalline-amorphous multiple structure i s concerned, t h i s theory i s considered preferable to the micellar theory, which was accepted before 1930 i n order to explain the properties of c e l l u l o s e . 7 The micellar theory assumed that molecular chains can never exceed the length of m i c e l l e s , 1 and amorphous material exists between micelles as a cementing medium which i s responsible for swelling of f i b r e s (55)• However, the existence of a separate cementing material f a i l e d to explain the structure of regenerated c e l l u l o s e (110). In addition c e l l u l o s e chains have been shown to be longer than the length of a micelle, by electron microscopic studies and ultracentrifuge and v i s c o s i t y methods (44,112). For these reasons, the fringe micellar theory i s more acceptable. According to the fringe micellar theory, the c r y s t a l l i n e regions alternate with the amorphous regions, with gradual t r a n s i t i o n from the former to the l a t t e r . No clear border exists between two phases, nor c o r r e l a t i o n between molecular chain length and size of c r y s t a l l i t e . B. L a t t i c e Structure I t follows that c e l l u l o s i c material has a p o l y c r y s t a l l i n e structure i n which the c e l l u l o s e molecules may traverse several c r y s t a l l i n e and amorphous regions. In the c r y s t a l l i n e region, the molecular chains form an ordered l a t t i c e structure i n which l a t e r a l intermolecular distance i s xThe terms "micelle" and " c r y s t a l l i t e , " although generally used interchangeably i n s c i e n t i f i c papers, are s l i g h t l y d i f f e r e n t i n nature. The terra "micelle" i s used to designate a d e f i n i t e concept of a region having d i s t i n c t boundaries, whereas the term " c r y s t a l l i t e " i s used without specifying any p a r t i c u l a r s i z e , shape or nature of the boundary between c r y s t a l l i n e regions (110). 8 kept at a minimum so that an equilibrium i s maintained at a minimum pot e n t i a l energy. Mark (85) suggested that the amorphous region should have a higher energy content than the c r y s t a l l i n e region. Thus, the i n t e r c r y s t a l l i n e area may be considered as highly disordered c r y s t a l l a t t i c e s i n which single atoms are sh i f t e d considerably from t h e i r normal equilibrium positions ( 1 0 0 ) . The analysis of l a t t i c e structure has been r a p i d l y advanced by X-ray d i f f r a c t i o n techniques. In the case of the c e l l u l o s e l a t t i c e , the transparent d i f f r a c t i o n diagram i s generally used for a n a l y t i c a l purposes. Since the angle of r e f l e c t i o n (20) can be calculated from the X-ray diagram and the X-ray system constructed, the interplane spacings can be e a s i l y determined by Bragg's Law. The unit c e l l l a t t i c e has been studied on t h i s p r i n c i p l e . The f i r s t unit c e l l was proposed by Polanyi ( 110) , who suggested a rhombic unit c e l l with dimensions of o 7*9x8.45x10.2 A. A few years l a t e r , an orthorhombic unit c e l l with axis a* = 6 . 1 , b* = 1 0 . 2 5 , c* = 5 .4 A, and B* = 88 degrees was suggested by Sponsler ( 1 3 4 ) . Sponsler's suggestion was followed by Meyer and h i s co-workers (89>90), and f i n a l l y led to the postulation of a monoclinic unit c e l l with axis a = 8 . 3 5 , b = 1 0 . 3 , and c = 7 .9 A, and B = 84 degrees. The planes of the anhydroglucose unit l i e i n the a-b plane and the •The d e f i n i t i o n of a, b, c, and B are given i n Figure 1, page 9 . 9 molecular chains are p a r a l l e l to the b-axis of the unit c e l l . A few years l a t e r , Meyer (89) suggested a revised model i n which the center chain and corner drains were running i n opposite d i r e c t i o n s , but the dimension of the unit c e l l remained the same. A model of the unit c e l l i s shown i n Figure 1. This structure was supported by Gross and Clark (42) i n 1938, and i t i s s t i l l generally accepted. 1. a»8-35A—*\ Figure 1. Unit c e l l of c e l l u l o s e I (Meyer and co-workers (110)) As mentioned previously, the formation of the unit c e l l i s a t t r i b u t e d to c r y s t a l l i z a t i o n , which i s caused primarily by intermolecular a t t r a c t i o n . I t has been shown that there are three d i f f e r e n t types of intermolecular a t t r a c t i n g forces acting i n three d i f f e r e n t d irections (110,145). Along the 10 b-axis, 1,4-glucosidic bonds between carbon and oxygen are connected by primary valence bonding which has a d i s s o c i a t i o n energy of about 50 k c a l . per mole. In the d i r e c t i o n of the a-axis, where the distance between the glucosidic r i n g i s o approximately 2 . 5 A, a strong intermolecular force i s present i n the form of hydrogen bonds a t t r a c t i n g each chain transversely i n the a-b plane. The hydrogen bond has an average bond energy of 5 k c a l . per mole. In the c-axis, the minimum distance i s about 3 .1 A. The only existing a t t r a c t i o n i s due to van der Waal's forces between the anhydroglucose rings which can be calculated to be 2 to 3 k c a l . per mole ( 110) . The c r y s t a l l i n e structure so far discussed belongs to c e l l u l o s e I or native c e l l u l o s e . There are three other d i f f e r e n t c r y s t a l l i n e modifications, depending on the type of chemical reagent used to modify the native structure, i . e . , c e l l u l o s e II (hydrate c e l l u l o s e or mercerized c e l l u l o s e ) , c e l l u l o s e III (ammonia cell u l o s e ) and c e l l u l o s e IV (cellulose T or high-temperature c e l l u l o s e ) . Each has a c h a r a c t e r i s t i c structure which has been studied by various investigators. The unit c e l l structure of these four types of c e l l u l o s e are summarized i n Table 1, page 11. 11 Table 1. The unit c e l l structure of c e l l u l o s e (110) c e l l u l o s e I c e l l u l o s e II c e l l u l o s e I I I c e l l u l o s e IV a* 8.35 8.1 7.74 8.11 b* 10.3 10.3 10.3 10.3 c* 7.9 9.1 9 .9 7 .9 84 62 58 90 o •unit: A **unit: degrees C. C r y s t a l l i n i t y of c e l l u l o s e 1. Concept Although a great number of investigations have been made regarding the c r y s t a l l i n i t y of c e l l u l o s e , and valuable data have been published, a proper d e f i n i t i o n of c r y s t a l l i n i t y has not yet been established. One of the most d i f f i c u l t problems i s that there i s no borderline which can be drawn between c r y s t a l l i n e and amorphous regions. Once th i s problem i s solved, the c r y s t a l l i n i t y of c e l l u l o s e can be defined simply as the f r a c t i o n of c e l l u l o s e contained i n the region i n which highly geometric order p r e v a i l s , with the distance between neighboring molecules governed by s t r i c t laws. The amorphous region, accordingly, must be considered to contain a l l possible intermediate degrees of packing between the l i q u i d and the c r y s t a l l i n e state ( 110) . 12 Various investigators have approached t h i s problem from d i f f e r e n t points of view by using d i f f e r e n t d e f i n i t i o n s of the " c r y s t a l l i n e region," which has led to a marked disagreement i n absolute values of c r y s t a l l i n i t y . For instance, those who treat t h i s problem from the physical point of view, define the " c r y s t a l l i n e region" as the portion which i s i n the state of perfect, three dimensional order and which gives r i s e to selec t i v e X-ray d i f f r a c t i o n patterns (44). Any portion which f a i l s to produce such d i f f r a c t i o n would be defined as an "amorphous region." On the other hand, those who approach th i s problem by chemical means consider the c r y s t a l l i n e region as the portion having extreme resistance to chemical attack, as compared with the rest of the region which i s accessible. On treatment with c e r t a i n chemical reagents under proper conditions, the residue i s considered as the c r y s t a l l i n e region while the rest i s the amorphous region. Because of t h e i r d i f f e r e n t approaches, the res u l t s have never coincided. The physical method always gives lower absolute c r y s t a l l i n i t y than the chemical method. A detailed discussion of the difference, i n res u l t s between these methods w i l l be given l a t e r . i n t h i s t h e s i s . Since the physical method and the chemical method always give considerably d i f f e r e n t values of c r y s t a l l i n i t y , some investigators prefer to use the term "degree of l a t e r a l order" (55,84,110) rather than "degree of c r y s t a l l i n i t y . " The concept of degree of l a t e r a l order i s based on the fringe 13 micellar theory as described above. That i s , the c r y s t a l l i n e region i n a given c e l l u l o s e may vary i n s i z e , shape and degree of perfection, and i s heterogenous rather than homogeneous as fa r as the order l e v e l i s concerned. Therefore a complete s t a t i s t i c a l d i s t r i b u t i o n of degree of perfection of the c r y s t a l l i n e region i s of greater importance than merely specifying absolute c r y s t a l l i n i t y . Howsman and Sisson, as c i t e d i n Ott et a l (110), defined the degree of order by the following equation: 0 = ( 0H C) / ( 0H t ) where 0 i s a degree of order, (0H C) i s the t o t a l number of hydrogen bonds a c t u a l l y present i n the region, and ( OH^ . ) i s the t o t a l possible number of hydrogen bonds i f a l l molecules are p e r f e c t l y c r y s t a l l i z e d . I f i t i s considered that d e f i n i t e quantities of c e l l u l o s e q^, q 2 , q^, q n can be associated with the order 0^, 02> 0^, 0 n, then a l a t e r a l - o r d e r d i s t r i b u t i o n curve can be obtained by d i f f e r e n t i a t i n g the summative mass-order curve i n which corresponding values o f q are plotted against 0. A high l a t e r a l order i n t h i s case corresponds to a high c r y s t a l l i n i t y . This idea has p r a c t i c a l experimental d i f f i c u l t i e s as fa r as the r e s o l u t i o n i s concerned, since i t i s dependent on the choice of the o r i g i n a l volume element. From the t h e o r e t i c a l point of view, sooner or l a t e r the d i s t r i b u t i o n curve evaluation w i l l be commonly adopted i n the f i e l d of structure studies of c e l l u l o s e . 1 14 2. Determination of c r y s t a l l i n i t y I t has been stated that methods for determination of c r y s t a l l i n i t y of c e l l u l o s e can be c l a s s i f i e d into two groups, chemical and ph y s i c a l . Generally speaking, the chemical methods assume that chemical reagents are unable to penetrate into the c r y s t a l l i n e region, thus the reaction takes place very r a p i d l y i n the i n i t i a l stage and f i n a l l y becomes very slow. The rate of reaction and percentage of c e l l u l o s e reacted are used as the measure of the a c c e s s i b i l i t y . The physical methods, on the other hand, measure c r y s t a l l i n i t y on the basis that the c r y s t a l l i n e region i s assumed to give high X-ray d i f f r a c t i o n , high density, or low moisture regain. In the usual case, the chemical method primarily measures the accessible or amorphous f r a c t i o n , whereas the physical method, i n general, measures the c r y s t a l l i n e region. I t should be noted that the accessible c e l l u l o s e i s not necessary equivalent to non-crystalline c e l l u l o s e . This can be demonstrated by the following equation ( 3 6 ) : A = o-d< + ( 100 - <*) where A i s the percentage of accessible c e l l u l o s e i n the sample, 0- i s the f r a c t i o n of the c e l l u l o s e occurring i n the surface of the c r y s t a l l i n e region, and c * i s the percentage of c r y s t a l l i n e c e l l u l o s e i n the sample. From the above equation, i t immediately follows that A i s dependent upon the size of c r y s t a l l i t e as well as the f r a c t i o n of c r y s t a l l i n e c e l l u l o s e . Since cr- i s not e a s i l y determined, most chemical methods do 15 not make adequate d i s t i n c t i o n between accessible and non-c r y s t a l l i n e c e l l u l o s e . I f an accurate r e s u l t i s required, t h i s equation should be taken into account. Both chemical and physical methods give the c r y s t a l l i n i t y i n either absolute or r e l a t i v e values. The absolute values do not agree with one another because of the d i f f e r e n t assumptions involved i n the in t e r p r e t a t i o n as noted. The difference i s p a r t i c u l a r l y d i s t i n c t between the acid hydrolysis method and the X-ray method, which w i l l be described i n d e t a i l i n a l a t e r section. The r e l a t i v e order of c r y s t a l l i n i t y for various c e l l u l o s e preparations as determined by both methods i s the same. The order of increasing c r y s t a l l i n i t y i s as follows: high-tenacity rayon, t e x t i l e rayons, Fortisan, mercerized cotton, wood pulp, and cotton. The methods for determining c r y s t a l l i n i t y so far published i n the technical l i t e r a t u r e are described below. (a) Chemical methods i ) Acid hydrolysis method The basis of the acid hydrolysis method i s that the i n t e r c r y s t a l l i n e chain network i s chemically more reactive than i s the Inaccessible c e l l u l o s e i n the c r y s t a l l i n e region. Thus the disordered chain segments are more ra p i d l y attacked by the ac i d , and the amount of non-crystalline c e l l u l o s e i s estimated from the rate of hydrolysis. 16 Nickerson was the f i r s t to apply the rate of hydrolysis i n H CI - FeCl^ reagent to evaluate the a c c e s s i b i l i t y of c e l l u l o s i c materials ( 9 6 , 9 7 , 9 8 , 1 0 1 , 1 0 2 , 1 0 3 ) . The c e l l u l o s e i s f i r s t hydrolyzed to glucose, which i s then oxidized to C0 2. By comparing the rate of CO2 evolution with that of glucose oxidized under s i m i l a r conditions, the rate of hydrolysis i s calculated and plotted against the time of hydrolysis. The hydrolysis rate curve thus obtained gives two d i f f e r e n t rates, being rapid during the f i r s t two or three hours of reaction period and then slowing at a l a t e r stage. A c c e s s i b i l i t y i s determined by extrapolating the slow rate period to zero time. The r e p r o d u c i b i l i t y of t h i s technique was greatly improved by Conrad and Scroggie ( 2 2 ) . Two more independent investigations (80,95) were undertaken i n which the r e s i s t a n t residue was used as a means of following the course of hydrolysis. Other hydrolyzing agents, such as s u l f u r i c a c i d , have also been used instead of hydrochloric acid, but i t was found that s u l f u r i c acid was less active as a hydrolyzing agent than hydrochloric acid of equivalent concentration ( 1 0 3 ) . In general, a c i d hydrolysis gives considerably lower values of the amorphous f r a c t i o n as compared with other methods. This i s p a r t i c u l a r l y true as compared with the X-ray method. The probable reason for t h i s f a c t i s that the cutting of i n t e r c r y s t a l l i n e chain segments removes r e s t r a i n t s and allows the loose chain ends freedom to undergo r e c r y s t a l l i z a t i o n . 17 i i ) Deuteration method Bpnhoeffer (12) was the f i r s t to observe the reaction of heavy water with the OH group of c e l l u l o s e . Later Champetier and V i a l l a r d (15) claimed that f i l t e r paper and l i n t c e l l u l o s e were completely accessible to D 2 0 and that exchange was completed i n 36 hours at 30°C. F r i l e t t e , Hanle and Mark (36) devised a method of digesting pulp i n water of high deuterium content. Exchange of H 2 0 and D 2 0 was permitted to occur and the rate of absorption of D 2 0 was determined as a function of time. By using a sim i l a r method with improved technique, these investigators obtained a rate curve i n which the i n i t i a l rapid reaction gradually slowed down and became v i r t u a l l y complete i n four hours. The f r a c t i o n which had not reacted a f t e r four hours was i d e n t i f i e d as highly ordered material. This conclusion was further confirmed by Rowen and P l y l e r ' s studies by means of in f r a - r e d spectroscopy (121) . Quantitative study.of deuteration by inf r a - r e d spectroscopy was extended by Almin (1), and followed by Mann and Marrinan ( 8 3 , 8 7 ) . The l a t t e r demonstrated the p o s s i b i l i t y of distinguishing between the deuteration of the c r y s t a l l i n e and that of the amorphous region from the shape of the absorption band i n the 3600 to 3000 cm."1 range. They also found that the isotopic exchange reaction between the OH group of c e l l u l o s e and l i q u i d D 2 0 gave a measure of a c c e s s i b i l i t y and not the c r y s t a l l i n i t y of c e l l u l o s e . By deuteration i n the vapor phase i t was possible to avoid 18 deuterating c r y s t a l l i n e regions, thus an estimate of the percentage of c r y s t a l l i n i t y was obtained. In thi s case, the c r y s t a l l i n i t y of c e l l u l o s e was defined as the f r a c t i o n of OH groups which were hydrogen-bonded i n a regular c r y s t a l l i n e manner. The r e l a t i v e value of c r y s t a l l i n i t y determined by t h i s method agreed reasonably well with values found by Hermans ( 8 3 ) . Since no c r y s t a l i z a t i o n takes place during the determination, the value of a c c e s s i b i l i t y i s , therefore, much higher than that evaluated by. an acid hydrolysis method. i i i ) C ellulose derivative method Determination of a c c e s s i b i l i t y by e t h e r i f i c a t i o n was i l l u s t r a t e d by Assaf, Hass and Purves ( 7 ) . Cellulose was treated with thallous ethylate to form a thallous de r i v a t i v e , which reacts with methyl iodide to y i e l d thallous iodide and methyl c e l l u l o s e . Analysis of methyl c e l l u l o s e f o r methoxyl content yi e l d s a measure of the accessible OH groups. This method can be carr i e d out i n a non-aqueous system as well as an aqueous system. The l a t t e r system usually gives higher a c c e s s i b i l i t y value than the former one because of swelling due to the medium. The r e s u l t a c t u a l l y obtained by these workers i n a non-aqueous system was the lowest a c c e s s i b i l i t y value ever reported for the chemical method (110). Tarkow (144) and Nickerson ( 9 9 ) have demonstrated a formic acid e s t e r i f i c a t i o n procedure for evaluation of a c c e s s i b i l i t y of c e l l u l o s e . This method i s based on the 19 assumption that the e s t e r i f i c a t i o n of white d e x t r i n and c e l l u l o s e are i d e n t i c a l chemical processes. The r a t i o of combined formic a c i d f o r c e l l u l o s e to that of d e x t r i n , under i d e n t i c a l c o n d i t i o n s , provides an estimate of the a c c e s s i b l e f r a c t i o n of c e l l u l o s e . i v ) O x i d a t i o n method The o x i d a t i o n of c e l l u l o s e w i t h sodium periodate i n aqueous s o l u t i o n was st u d i e d by G o l d f i n g e r , Mark and S i g g i a (40). The periodate i o n i s known to at t a c k the second and t h i r d p o s i t i o n of the glucose anhydride u n i t by s p l i t t i n g the g l y c o l c o n f i g u r a t i o n and converting i t t o two carbonyl groups. A r e a c t i o n r a t e curve s i m i l a r to that of a c i d h y d r o l y s i s was obtained. By e x t r a p o l a t i o n of the extremely slow r a t e curve, the amount of amorphous component was evaluated. R e c r y s t a l l i -z a t i o n probably takes place during the o x i d a t i o n (110). Roseveare and Spaulding (120) demonstrated another o x i d a t i o n method by t r e a t i n g c e l l u l o s e w i t h n i t r o g e n d i o x i d e i n carbon t e t r a c h l o r i d e . I t has been shown (37>120) t h a t chromic a c i d acts very l a r g e l y on the amorphous r e g i o n w h i l e p e r i o d i c a c i d acts on the c r y s t a l l i n e r e g i o n as w e l l . Thus Glegg (38) o x i d i z e d c e l l u l o s e w i t h chromium t r i o x i d e i n a c e t i c a c i d - a c e t i c anhydride s o l u t i o n and evaluated the a c c e s s i b i l i t y . This method showed a f a i r l y good c o r r e l a t i o n w i t h the t h a l l o u s e t h y l a t e method over a 200-fold range of a c c e s s i b i l i t y ( 7 ) . 20 v) Iodine sorption- method In order to know the mercerization effects on ce l l u l o s e and the degree of mercerization, Schwertassek developed a technique for determination of iodine sorption (124 , 125»126,127). On the basis of his series of experiments, he concluded that iodine sorption could be used as a measure of the amorphous f r a c t i o n of c e l l u l o s e . A decrease i n iodine sorption i s an i n d i c a t i o n of an increase i n c r y s t a l l i n i t y . The method was applied by He.ssler. and Power (59) i n the study of various treatment effects on cotton c e l l u l o s e . A r a t i o of the weight of I 2 absorbed by c e l l u l o s e to that absorbed by methocel gave a value for the amorphous f r a c t i o n . The c r y s t a l l i n i t y was obtained by subtracting the percent of amorphous material from 100. Results were i n good agreement with the value obtained by.other chemical methods. To apply t h i s method, the temperature at which the adsorption i s ca r r i e d out should be sp e c i f i e d , since the adsorption i s greatly dependent upon the temperature, as claimed by Chitale (1(5). This method was also c r i t i c i s e d by Majury ( 8 2 ) , who showed that the sorption of iodine by c e l l u l o s e acetate could not be interpreted s o l e l y i n terms of sorption by amorphous materials. Thus quantitative a p p l i c a t i o n of t h i s method to c e l l u l o s e f i b r e may need to be reviewed. 21 (b) Physical methods i ) X-ray method Among the physical methods, the X-ray method i s the most widely used quantitative method for c r y s t a l l i n i t y evaluation. Since i t i s applied i n t h i s study, a more detailed description of i t s p r i n c i p l e and procedure i s given i n t h i s section. When a f i b r e sample i s exposed to a narrow X-ray beam, the interference corresponding to the crystallographic plane gives r i s e to selec t i v e d i f f r a c t i o n which appears on an X-ray diagram as black spots. Generally speaking, cellulose, produces three intense interference spots arranged symmetrically along the equator of an X-ray diagram. These three interference spots are d i f f r a c t e d from the 101, 101 and 002 plane of the unit c e l l respectively. For wood f i b r e s , the X-ray diagram shows only two interference spots since the interference caused by the 101 and 101 planes are combined. I f the randomly oriented f i b r e specimen i s rotated at constant speed during the X-ray exposure, two d i s t i n c t interference rings appear instead of two interference spots. A densitometer curve along the equator of the X-ray diagram i s usually reproduced from the X-ray diagram. Two interference spots or interference rings w i l l appear as two interference peaks i n the densitometer curve. From th i s curve, the i n t e n s i t y , p o s i t i o n , and r a d i a l width of the interference 22 p e a k s c a n b e m e a s u r e d . T h e s e p a r a m e t e r s a r e u s e d t o c a l c u l a t e d a t a p e r t i n e n t t o f i n e s t r u c t u r e o f c e l l u l o s e , s u c h a s t h e d i m e n s i o n o f a u n i t c e l l , o r i e n t a t i o n o f c e l l u l o s e m o l e c u l a r c h a i n s , s i z e o f m i c e l l e s , a n d d e g r e e o f c r y s t a l l i n i t y . A s f a r a s t h e d e g r e e o f c r y s t a l l i n i t y i s c o n c e r n e d , t h e i n t e n s i t y o f t h e i n t e r f e r e n c e p e a k s a n d t h e d i f f u s e b a c k g r o u n d a r e g e n e r a l l y t a k e n a s a m e a s u r e o f c r y s t a l l i n i t y . T h e c r y s t a l l i n i t y i n t h i s c a s e i s d e f i n e d a s t h e f r a c t i o n o f c e l l u l o s e w h i c h g i v e s r i s e o f s e l e c t i v e d i f f r a c t i o n o f X - r a y s (44) . T h i s d e f i n i t i o n a s s u m e s t h a t t h e c r y s t a l l i n e p o r t i o n o f c e l l u l o s e r e p r e s e n t s a c e r t a i n d e g r e e o f o r d e r i n t h e c h a i n s y s t e m w h i c h w o u l d r e f l e c t i t s e l f a s X - r a y d i f f r a c t i o n i n t e n s i t y o f a d e f i n i t e m a g n i t u d e . T h i s a s s u m p t i o n i s b a s e d o n t h e p r e s u p p o s i t i o n t h a t t h e d e g r e e o f o r d e r o f t h e c r y s t a l l i n e a r e a s o f c e l l u l o s e i s p r a c t i c a l l y c o n s t a n t i n a l l t y p e s a n d c r y s t a l m o d i f i c a t i o n s o f c e l l u l o s e . A c c o r d i n g t o t h e c o n c e p t o f l a t e r a l o r d e r d i s t r i b u t i o n m e n t i o n e d i n t h e p r e v i o u s s e c t i o n , t h i s a s s u m p t i o n I s n o t a l w a y s t r u e . F u r t h e r m o r e , t h e a s s u m p t i o n t h a t d i f f u s e b a c k g r o u n d i s s o l e l y c a u s e d b y t h e a m o r p h o u s f r a c t i o n , i s a l s o d o u b t f u l . T h e s u r f a c e l a y e r o f m i c e l l e s w i l l a l s o c o n t r i b u t e t o s o m e e x t e n t t o t h e X - r a y b a c k g r o u n d s c a t t e r i n g a s n o n - c r y s t a l l i n e m a t e r i a l , b e c a u s e t h e s u r f a c e o f m i c e l l e s r e p r e s e n t s a d i s c o n t i n u i t y c a u s i n g s o m e d i s p l a c e m e n t o f t h e c h a i n s . T h i s m e a n s t h a t d e c r e a s i n g s i z e o f t h e m i c e l l e s w i l l i n c r e a s e t h e b a c k g r o u n d s c a t t e r i n g . T h e s e t w o p o i n t s s h o u l d b e 23 understood before the X-ray method is applied. X-ray methods so far developed can be summarized below. The first quantitative study of crystallinity by the X-ray method was made by Hermans (46). An X-ray photograph was taken by exposing the fibre specimen in the form of a pellet. The total amount of incident radiation received by one specimen during the exposure was measured by a miniature camera to compare with that of other.specimens for the purpose of correction. A radial photometer trace was then taken from one of the exposed quadrants of the X-ray diagram. The integrated intensity of the crystalline interference above the background was considered as a measure of the crystalline fraction, whereas maximum intensity of the background scattering was used as a measure of the fraction of disordered cellulose. A similar assumption was applied later by Kast and Plaschner ( 3 1 , 6 9 ) , and Clark and Terford ( 1 9 ) . This method has been extensively applied by Hermans and his co-workers in establishing absolute value of crystallinity for different types of cellulose ( 4 5 , 4 7 , 4 8 , 4 9 , 5 0 , 5 1 , 5 2 , 5 4 ) . Although Hermans' method gives an absolute value of crystallinity, i t does not necessarily mean that a l l crystalline regions are completely measured, because of the fact that very small crystalline regions will not contribute to the X-ray maxima. Moreover, this method requires a special type of camera and a rotating sample holder, so that in most cases this method is not easily adopted for routine 24 purpose. A simple technique with reasonable r e p r o d u c i b i l i t y may be much more p r a c t i c a l i n the case where only r e l a t i v e v a r i a t i o n of c r y s t a l l i n i t y i s of inter e s t to the investigator. Several techniques have been developed during the l a s t few years. These techniques generally use X-ray equipment which i s available i n most laboratories. The c r y s t a l l i n i t y i s calculated by a simple formula which gives r e l a t i v e rather than absolute c r y s t a l l i n i t y . Wakelin, V i r g i n and Crystal (148) have demonstrated an integrated method and a c o r r e l a t i o n method by using Geiger Counter instrumentation. The r e s u l t was expressed as a c r y s t a l l i n i t y index. Ant-?/uorlnen (5>6) developed another c r y s t a l l i n i t y index using the Debye-Scherrer powder technique. The width and height'of the 002 peak on the photometer i n t e n s i t y curve were used as a measure of c r y s t a l l i n i t y . The technique was l a t e r improved by Kouris, Ruck and Mason (72,73). The a p p l i c a t i o n of an X-ray spectrometer was i l l u s t r a t e d by Anker-Rasch and McCarthy (3>4). The i n t e n s i t y of the 101 peak was taken as a measure of c r y s t a l l i n i t y and r e s u l t s were expressed as a c r y s t a l l i n i t y r a t i o . Ingersoll (65) also used t h i s peak to evaluate the c r y s t a l l i n i t y number. Sobue and Minato (133) simply took the area surrounded by the i n t e n s i t y curve (including 101, 101 and 002 peaks)" and background curve as the c r y s t a l l i n i t y area for comparison of r e l a t i v e order of c r y s t a l l i n i t y . 25 i i ) Moisture regain method Hermans was the f i r s t to establish the relationship between the sorption ratio (SR) 2 of cellulose, and amorphous content as estimated by the density or X-ray method ( 4 3 ) . The regression line gave the equation: SR = 0 .07 + 3 ( 1 - * * ) ' where cK was the fraction of crystalline material. Thus, i f the SR is determined experimentally, then the cry s t a l l i n i t y i s readily calculated from the equation. According to this equation, the sorption ratio of completely amorphous cellulose is 3 . 0 7 . Howsmon (63) also showed that there was an approximately linear relationship between the sorption of cellulose and accessibility to liquid D 2 O - H 2 O mixture. Assuming that the moisture regain was a measure of accessibility, and that Mark's value (35) for the accessibility of cotton (0.44) was correct, Howsmon obtained the accessibility of other cellulose preparations by multiplying their sorption ratio by 0.44. Later, this value was changed to 0.40 (110). The relationship between sorption ratio and the fraction of amorphous materials, as measured by Mann and Marrinan ( 8 3 ) , was also illustrated by Valentine (147) with a regression equation ^Sorption ratio (SR) is the ratio of moisture sorption of a specific cellulose to that of cotton under the same conditions (146). Since the sorption ratio is independent of the temperature and relative humidity over the range of 20 to 70 percent (110), i t is often convenient to use sorption ratio rather than absolute absorption. 26 SR. = 2.6 F m, where F m was the amorphous f r a c t i o n and SR was the sorption r a t i o . Magne, Portas and Wakeham (8l) calculated the r e l a t i v e amount of frozen water ( c a p i l l a r y condensed or solvent water) and unfrozen water (bound water) from calorimetric data. Assuming that three molecules of water were absorbed by each glucose anhydride u n i t , he was able to calculate the degree of c r y s t a l l i n i t y . Recently, Preston and Tawde (114) also determined the bound water i n f i b r e s , and found a direct c o r r e l a t i o n between the bound-water r a t i o ( i . e . , the bound-water r e l a t i v e to that of cotton) and the sorption r a t i o . The bound-water r a t i o of hydrate c e l l u l o s e (123), which they assumed to be completely amorphous, may be calculated from t h e i r data to be 3»2> thus leading to a sorption r a t i o of the same value. Heat of wetting also may be used as a measure of the amorphous f r a c t i o n of cel l u l o s e because highly amorphous cel l u l o s e always gives a high value of heat of wetting (15D. There i s a strong c o r r e l a t i o n between sorption r a t i o and heat of wetting, i . e . , the higher the heat of wetting, the higher w i l l be the sorption r a t i o , so that the appli c a t i o n of heat of wetting for determination of c r y s t a l l i n i t y i s generally replaced by the sorption r a t i o or moisture regain method. 27 i i i ) Infra-red absorption spectroscopy method The d i r e c t a p p l i c a t i o n of in f r a - r e d absorption spectroscopy into the f i e l d of c r y s t a l l i n i t y studies was ignored u n t i l F o r z i a t i and Rowen (33,34) demonstrated the spectra, of cotton before and af t e r grinding i n a vibrating' b a l l m i l l . ~ They found that the spectra of c e l l u l o s e I showed sharp and c l e a r l y defined absorption bands at 7.0> 7*3> 7 '4 and 7 .5 micron wave lengths. When the c e l l u l o s e I i s converted into amorphous material by grinding i n a vi b r a t i n g b a l l m i l l , these maximum absorption bands merged into a single broad band, and the absorption at 1.1;2 microns increased. O'Connor, Dupre and Mitcham (108) made use of t h i s f a c t and took the r e l a t i v e change of o p t i c a l <|ensity of the absorption bands at 6 .9 microns and Il.O microns as measures of c r y s t a l l i n i t y . The absorption bands at 6 .9 microns and 11.0 microns represented c r y s t a l l i n e bands and an amorphous 'band respectively. The r a t i o of the absorbence of the band maximum, at rabout 6 .9 microns, to that at about 11.0 microns, was defined as the c r y s t a l l i n i t y index. The assignment of a c r y s t a l l i n e band to a p a r t i c u l a r wave length i s dependent upon types of c e l l u l o s e under question. Sandeman and K e l l e r (122), f o r example, assigned absorption bands at 10.7 microns i n the spectra of nylon 6 , at 10.67 microns i n the spectra of nylon 6 . 6 , and at 10 .64 microns i n the spectra of nylon 6.10, as c r y s t a l l i n e bands. For the wood-fibre c e l l u l o s e 28 prepared from western hemlock, the writer found that the c r y s t a l l i n e band could be assigned at 7*2 microns and the amorphous band at 11.2 microns.3 Sobue and Fukuhara ( 132) , on the other hand, took the r a t i o of the o p t i c a l density at absorption caused by OH stretching (3315 cm."*-*- for ramie and 3440 cra.""^ for viscose r e s p e c t i v e l y ) , to that caused by CH stretching at 2900 cm.~^, as a measure of c r y s t a l l i n i t y . Iv) Density method For a given weight of f i b r e , the r e s u l t of a density determination w i l l depend on the extent to which the medium penetrates into the amorphous region, which i s the only region allowing the molecules of the medium to penetrate. On t h i s basis, i t i s l o g i c a l to presume that the density of packing of fibrous substance provides a reasonable c r i t e r i o n for the quantitative separation of the c r y s t a l l i n e and the amorphous portion. Hermans and his co-worker (43,53) estimated the absolute quantity of the c r y s t a l l i n e substance by assuming that the difference between the s p e c i f i c volume of the c r y s t a l l i n e substance, and that of the amorphous state, are of the same order for c e l l u l o s e as they are for other organic substances. The r e s u l t s were i n good agreement with other physical methods. It was also suggested that determination of dry density, possibly by the use of a density gradient tube, should ^Unpublished data. 29 provide a convenient method f o r determining an approximate value of the c r y s t a l l i n i t y of c e l l u l o s e f i b r e ( 9 2 ) . 3 . Treatments a f f e c t i n g c r y s t a l l i n i t y F r om.the-foregoing.description, i t f o l l o w s t h a t the c r y s t a l l i n i t i e s of various c e l l u l o s i c m a t e r i a l s are d i f f e r e n t from one another, and the absolute value of c r y s t a l l i n i t y of the same c e l l u l o s e i s a l s o v a r i a b l e depending on the method a p p l i e d . Furthermore, the i n i t i a l c r y s t a l l i n i t y of c e l l u l o s e can be modified to give higher or lower values by various mechanical and chemical, treatments. The purpose of t h i s s e c t i o n i s to discus s some major e f f e c t s of various treatments on c r y s t a l l i n i t y , and a l s o t h e i r s i g n i f i c a n c e from the p o i n t of view of a p p l i c a t i o n t o the study of f i n e s t r u c t u r e of c e l l u l o s i c m a t e r i a l s . (a) H y d r o l y s i s M e l l e r ( 8 8 ) , I n g e r s o l l (65) > and Howsmon (63) have shown that the c r y s t a l l i n i t y of c e l l u l o s e w i l l be c o n s i d e r a b l y increased a f t e r h y d r o l y s i s . Both removal of amorphous m a t e r i a l by a c i d a t t a c k , and r e c r y s t a l l i z a t i o n of c e l l u l o s e molecular chains, are r e s p o n s i b l e f o r such an e f f e c t . The reason i s th a t molecular chains i n the amorphous region,once ruptured by a c i d attack, tend t o increase the m o b i l i t y of the c h a i n end and allow them to rearrange themselves i n a much more compact form. The increase i n c r y s t a l l i n i t y by h y d r o l y s i s can be shown c l e a r l y by X-ray diagrams i n which 30 the i n t e n s i t y of the 002 peak and the 101 + 101 combination peak w i l l increase markedly a f t e r hydrolysis. The f a c t that the rupture of the chain starts from the amorphous region can be observed from the reaction-rate curve of hydrolysis. During the i n i t i a l stage of reaction, the chemical reagents penetrate r a p i d l y into the amorphous region. Most of the rupture of the chains takes place at th i s stage, thus the reaction proceeds at a very rapid rate. As soon as the amorphous region has been destroyed, the reaction w i l l be slowed down because the chemical reagent does not r e a d i l y penetrate into the c r y s t a l l i n e region, but merely attacks the surface of the c r y s t a l l i t e . Consequently, the size of the c r y s t a l l i t e w i l l gradually decrease as the time of hydrolysis i s prolonged (64,11). The percentage of residue recovered w i l l decrease proportionally with time of hydrolysis, but the c r y s t a l l i n i t y of residue w i l l increase s i g n i f i c a n t l y . The rate of increase i n c r y s t a l l i n i t y due to hydrolysis follows a curve si m i l a r to the hydrolysis rate curve. The hydrolysis method i s generally used to prepare a ce l l u l o s e standard of high c r y s t a l l i n i t y (83,87,148). (b) Heat I f the c e l l u l o s e i s dried under heat without a prolonged drying time, i t s c r y s t a l l i n i t y i s affected to a lesser extent. For instance, very l i t t l e change i n chemical nature takes place when c e l l u l o s e i s heated at a temperature 31 of 140°C for less than four hours ( 2 8 ) . It has been shown (32,39,62,119) that at a s u f f i c i e n t l y high temperature, c e l l u l o s e undergoes both chemical and physical modifications and the molecular chains w i l l be disordered due to a thermal e f f e c t . Hessler and Power (59) observed that surface heat was more e f f e c t i v e i n opening the c r y s t a l l i t e than hot a i r . Cotton rotated against a hot surface for a few minutes showed a drop i n c r y s t a l l i n i t y from 89 percent to 79 percent as determined by the iodine sorption method. Taniguchi (143) claimed that c r y s t a l l i n i t y of sulphite pulp decreased on heating with hot a i r f o r 1 to 2 hours at 110 to 245°C. The decrease was p a r t i c u l a r l y remarkable as the temperature was increased. (c) Mechanical d e c r y s t a l l i z a t i o n Grinding and vib r a t i n g i n a b a l l m i l l w i l l cause an appreciable d e c r y s t a l l i z a t i o n ( 3 3 , 3 4 , 4 5 , 5 8 , 7 2 , 9 4 , 1 0 8 , 1 3 6 , 1 3 7 ) . In t h i s case f i b r e s are disintegrated into very fine powder which does not show se l e c t i v e d i f f r a c t i o n on an X-ray diagram, but Increases the background scattering caused by amorphous p a r t i c l e s ( 7 2 , 1 1 0 ) . In the infr a - r e d absorption spectrum, t h i s f i n e powder w i l l show an increased absorption at the amorphous band and decreased absorption at the c r y s t a l l i n e band ( 3 4 , 1 0 8 ) . 32 The mechanism f o r t h i s type of degradation can be explained from the poin t of view of mechanical impact and s t r e s s c y c l i n g . I f the k i n e t i c energy produced by the impact of the b a l l s on the c e l l u l o s e f i b r e s i s converted d i r e c t l y i n t o molecular v i b r a t i o n a l energy, i t i s s u f f i c i e n t to cause rupture of the primary valence bonds (137)• The impact of the b a l l s on the container evolves a considerable amount of heat. By means of the Congo red t e s t , i t was shown that the rupture of the c e l l u l o s e chain was the r e s u l t of mechanical a c t i o n r a t h e r than a thermal phenomenon (110,137)* Mechanical d e c r y s t a l l i z a t i o n i s commonly used f o r the p r e p a r a t i o n of an amorphous standard i n the X-ray method as w e l l as i n the i n f r a -red a b s o r p t i o n spectroscopy method. (d) Degradation by microorganisms Decay of c e l l u l o s i c m a t e r i a l i s a t t r i b u t e d to the enzymes which are secreted by microorganisms. The amorphous regions are l o o s e l y compacted and r e a d i l y a v a i l a b l e f o r p e n e t r a t i o n of enzymes, which, l i k e other chemical reagents, att a c k the amorphous regions at a r e l a t i v e l y r a p i d r a t e i n the i n i t i a l stage of decay. The r a t e of a t t a c k w i l l slow r a p i d l y when the enzymes s t a r t to a t t a c k the c r y s t a l l i n e r e g i o n s . As a r e s u l t of such a t t a c k , the amorphous m a t e r i a l s are d i s s o l v e d away and the broken chains themselves tend to r e c r y s t a l l i z e . Hence, during the i n c i p i e n t stage of decay, an apprec i a b l e increase i n c r y s t a l l i n i t y could be expected. The 33 rate of increase i n c r y s t a l l i n i t y i s approximately a function of rate of breakdown of c e l l u l o s e chains by enzymes (110, 131) . The rate curve i s similar to that of acid hydrolysis. I t should be noted, however, that the action of microorganisms i s s l i g h t l y d i f f e r e n t from that of acid hydrolysis i n that the former does not decrease the degree of polymerization (110,151) , whereas the l a t t e r markedly depolymerizes the ce l l u l o s e chains ( 2 6 , 1 6 3 ) . Some workers claim that enzymatic hydrolysis w i l l also cause considerable depolymerization (30,41 ,61 ,76 ,106,107,159) . Thus a controversy s t i l l exists on this point. (e) L a t t i c e t r a n s i t i o n 1) T r a n s i t i o n from c e l l u l o s e I to c e l l u l o s e II When native c e l l u l o s e i s treated with a c e r t a i n concentration of sodium hydroxide (mercerization), the l a t t i c e structure i s changed and c e l l u l o s e II i s formed. Treatment with about 6 l percent n i t r i c acid followed by washing also r e s u l t s i n the same t r a n s i t i o n ( 2 ) . This t r a n s i t i o n changes not only the dimensions of the l a t t i c e unit c e l l as revealed on the X-ray d i f f r a c t i o n pattern, but also the degree of c r y s t a l l i n i t y of c e l l u l o s e , which w i l l be decreased due to mercerization (3>54). This i s caused mainly by the disordering of the c e l l u l o s e molecular chains produced by the penetration of sodium hydroxide molecules into the l a t t i c e during the mercerization, with the r e s u l t that the 34 amorphous region increases at the expense of the c r y s t a l l i n e region. Anker-Rasch and McCarthy (3) made use of t h i s c h a r a c t e r i s t i c to study the concentration of sodium hydroxide at which the l a t t i c e t r a n s i t i o n was completed, by following the v a r i a t i o n of c r y s t a l l i n i t y . When the t r a n s i t i o n took place, the c r y s t a l l i n i t y decreased r a p i d l y . Higgins (60) also studied the l a t t i c e t r a n s i t i o n by infra-red absorption spectroscopy and found that when l a t t i c e t r a n s i t i o n took place, the absorbency at 7.0 microns decreased, and that at 11.2 microns increased. Since the c r y s t a l l i n i t y decreases at t h i s point, the r e l a t i v e absorbency at these two wave lengths could be taken as the measure of c r y s t a l l i n i t y . This gives additional evidence that the assignment of a c r y s t a l l i n e band at about 7'0 microns and an amorphous band at about 11.2 4 microns i s acceptable. i i ) T r a n s i t i o n from c e l l u l o s e I to c e l l u l o s e III On treatment of c e l l u l o s e I with ethylamine, c e l l u l o s e III i s obtained. A decrease i n c r y s t a l l i n i t y i s inevit a b l e because of the i n t r a c r y s t a l l i n e swelling due to ethylamine (9,18,78,79,128,129). A highly amorphous c e l l u l o s e , therefore, can be obtained by treating c e l l u l o s e with ethylamine followed by evaporation of the amine at atmospheric 'See page 28. 35 pressure. This i s sometimes done i n order to prepare an amorphous standard for the study of c r y s t a l l i n i t y (108,148). i i i ) T r a n s i t i o n from c e l l u l o s e II and III to  ce l l u l o s e IV When c e l l u l o s e II or c e l l u l o s e III i s heated at temperatures between 140 to 300°C i n water under pressure, i n g l y c e r o l , or i n formamide, c e l l u l o s e IV i s formed (75»9D• The c r y s t a l l i n i t y of c e l l u l o s e IV i s s i g n i f i c a n t l y higher than that of c e l l u l o s e II or c e l l u l o s e I I I . (f) Pulping The e f f e c t of pulping on c r y s t a l l i n i t y of pulp was well demonstrated by Taniguchi's series of experiments. Following the curve of changes i n c r y s t a l l i n e regions during sulphate pulping, he found that the c r y s t a l l i n e region content of bleached pulp and v i s c o s i t y decreased gradually, and the rate of decomposition increased with the length of pulping time (141). The sulphate pulp was bleached by 2- , 3~» 9-nd 5-stage methods and the c r y s t a l l i n i t y as determined by the hydrolysis method was found to be 9l«60, 92.45, and 92.63 percent respectively (138). However, n e g l i g i b l e differences i n c r y s t a l l i n i t y of pulp bleached by NaC102 and Ca(C10) 2 were observed i n his l a t e r works (139,140). He also showed that the c r y s t a l l i n i t y of sulphite pulp increased on heating with water for two hours at 100 to 190°C, but decreased on heating with hot a i r for 1 to 2 hours at 110 to 245°C. The rate of 36 decrease i n c r y s t a l l i n i t y increased with temperature (143). The effect of beating on c r y s t a l l i n i t y was observed by Wijnman ( l 6 o ) . He claimed that when p u r i f i e d cotton f i b r e s were subjected to heavy beating i n a Jokro m i l l , a marked decrease was observed i n the degree of polymerization, together with a moderate reduction i n the average size of c r y s t a l l i t e and a small reduction i n c r y s t a l l i n i t y . Groundwood pulp was found to give high capacity of s u l f u r i c acid sorption (117)» which indicates that the groundwood pulp might have a r e l a t i v e l y high value of a c c e s s i b i l i t y . (g) Stretching Stretching usually causes an increase i n c r y s t a l l i n i t y . For instance, i t was estimated that a normal coagulated viscose filament was about 40 percent c r y s t a l l i n e and 60 percent amorphous, whereas filaments of the same material af t e r being stretched, appeared to be 70 percent c r y s t a l l i n e and 30 percent amorphous (100). 4. Relationship between c r y s t a l l i n i t y and properties  of c e l l u l o s e The r e l a t i o n s h i p between c r y s t a l l i n i t y and chemical r e a c t i v i t y , density, moisture regain, and dye sorption i n terms of iodine sorption have been described i n d e t a i l . The present discussion i s confined to the re l a t i o n s h i p between c r y s t a l l i n i t y and remaining properties of c e l l u l o s e . 37 (a) Young's modulus I t has been pointed out by Mark ( l 6 l ) that u n c r y s t a l l i z e d and poorly organized chains w i l l e x h i b i t e l a s t i c i t y of the type which has been r e c e n t l y i n v e s t i g a t e d i n h i g h l y e l a s t i c long polymers. Measurements and, c a l c u l a t i o n s of various workers ( l 6 l ) a l s o showed that the presence of long f l e x i b l e chains l e d to a r e v e r s i b l e f. 7 e l a s t i c i t y , w i t h modulus of about 10 to 10' dynes per sq. cm. and a r a t h e r h i g h range of e x t e n s i b i l i t y . On the other hand, i f a f o r c e i s a p p l i e d to a homopolar covalent bond and the assumption i s made that the sample under i n v e s t i g a t i o n i s made up of i n f i n i t e l y l o n g , u n i n t e r r u p t e d , p a r a l l e l c h a i n s , a I P modulus of e l a s t i c i t y i s obtained of. about 2 x 10 c dynes per sq. cm. This would correspond to a completely c r y s t a l l i z e d and p e r f e c t l y o r i e n t e d m a t e r i a l . C e l l u l o s e can be considered as a mixture of c r y s t a l l i z e d and amorphous regions i n which the former have an average e l a s t i c modulus of about 1 0 ^ , whereas the l a t t e r have one of about 10^ dynes per sq. cm. ( l 6 l ) . Applying t h i s i d e a , Hermans and co-workers (44), and others ( 8 5 ) , explained the long-range, low-modulus, e l a s t i c behavior of c e l l u l o s e by two moduli. The one which corresponded to the c r y s t a l l i n e p a r t s had the order of magnitude of 1 0 X A to 10^ dynes, and the one which corresponded to the amorphous r e g i o n had an order of 10^ to 10? dynes per sq. cm. I n s h o r t , from the p o i n t of view of a chain model, h i g h modulus i s t h e o r e t i c a l l y 38 understood to be associated with a high degree of c r y s t a l l i n i t y . (b) Tensile strength I f i t i s assumed that a sample consists of uninterrupted p a r a l l e l glucosidic chains, a t h e o r e t i c a l tenacity of about 4 0 0 , 0 0 0 kg. per sq. cm. could be expected (10). In the case of completely p a r a l l e l , overlapping chains, having an average degree of polymerization of $00 glucose units, t h i s value has been calculated to be 12,500 /kg. per sq. cm. (10,90). From the t h e o r e t i c a l point of view, the c r y s t a l l i t e forms the firm r e i n f o r c i n g part of the structure, whereas the amorphous regions are the actual points of weakness (100). It follows that c e l l u l o s e of high c r y s t a l l i n i t y usually has high t e n s i l e strength. On the other hand, both the orientation of micelles and c e l l u l o s e chain length d i s t r i b u t i o n are also found to be important factors a f f e c t i n g t e n s i l e strength (14 , 2 1 , 2 9 , 5 6 , 8 6 , 109,l l8,135»l58). The interactions among these factors are so complicated that one can hardly e s t a b l i s h a r e l a t i o n s h i p between c r y s t a l l i n i t y and t e n s i l e strength alone. Ingersoll (65) has shown by a p a r t i a l l i n e a r c o r r e l a t i o n technique that at a constant wet elongation and orientation, wet tenacity i s no longer s i g n i f i c a n t l y associated with l a t e r a l order. Thus, the degree of c r y s t a l l i n i t y alone might not be a c r i t i c a l factor which a f f e c t s the t e n s i l e strength. 39 (c) Elongation Mark (85) has proposed that f l e x i b i l i t y and r e a c t i v i t y of c e l l u l o s e are dependent upon the disordered region of c e l l u l o s e , whereas the tenacity and e l a s t i c modulus are related to the amount of ordered materials. This i s confirmed by various experimental data. For example, Ward (151) demonstrated that yarns from cottons of decreased c r y s t a l l i n i t y did have increased elongation as compared with that of the o r i g i n a l cotton. Conrad and Scroggie also found that elongation increased with a c c e s s i b i l i t y (22). Similar r e s u l t s were obtained by Ingersoll ( 6 5 ) , who claimed that when orientation and wet tenacity were kept constant by the method of p a r t i a l l i n e a r c o r r e l a t i o n , the r e l a t i o n s h i p between wet elongation and l a t e r a l order remained s t a t i s t i c a l l y s i g n i f i c a n t . (d) Alpha-cellulose content Conrad and Scroggie (22) demonstrated that a decrease i n a c c e s s i b i l i t y or an increase i n c r y s t a l l i n i t y , i n general, was p a r a l l e l e d by an increase i n alpha-cellulose content of the raw material. The decrease i n a c c e s s i b i l i t y may a r i s e from somewhat smaller amounts of r e l a t i v e l y low-molecular-weight materials such as beta and gamma ce l l u l o s e i n the high-alpha-cellulose material. Actual experimental r e s u l t s (22) showed that xylose and pentosan evolved C0 2 at a r,ate higher than c e l l u l o s e or even glucose. An increase i n 40 a c c e s s i b i l i t y should therefore occur when materials of t h i s type are present. The general r e l a t i o n between alpha-c e l l u l o s e content and c r y s t a l l i n i t y i s shown i n Table 2. Table 2. Relationship between alpha-cellulose content and c r y s t a l l i n i t y of c e l l u l o s e (22) Alpha-cellulose A c c e s s i b i l i t y * Source content (%) (%) Wood pulp from beech 8 8 . 5 - 8 9 . 0 H . 5 Wood pulp from southern pine 93.P 10.0 Wood pulp from western hemlock 91.5 9.0 High-alpha wood pulp from southern pine 9 4 . 5 - 95.0 7.5 Cotton l i n t e r s 9 8 . 5 5.3 •Determined by acid hydrolysis method (e) Swelling and dimensional s t a b i l i t y As f a r as swelling due to water i s concerned, i t can be considered as the f i n a l r e s u l t of penetration of water molecules into the c e l l u l o s e inter-molecular chain region, which, i n turn, causes an expansion i n volume. In order to penetrate between two c e l l u l o s e molecular chains, a water molecule should have enough energy to overcome the l a t t i c e energy or to break the secondary bonds between c e l l u l o s e molecular chains. This can be done e a s i l y i n amorphous regions or on the surface of c r y s t a l l i t e s .where the i n t e r -molecular chain bondings are weak, but not i n the c r y s t a l l i n e region. Therefore, i t i s reasonable to expect that swelling 41 w i l l decrease as the c r y s t a l l i n i t y i s increased. This i s confirmed by the f a c t that swelling decreases as f i b r e density increases. For example, a rayon which swells 160 percent of i t s i n i t i a l volume has a density of 1 .503, whereas cotton which swells only 50 percent has a density of 1.534 ( 1 0 0 ) . I t should be reemphasized that both degree of c r y s t a l l i n i t y and size of c r y s t a l l i t e play an equally important r o l e i n the absorption of moisture and swelling of c e l l u l o s e . Based on the c h a r a c t e r i s t i c nature of the amorphous and the c r y s t a l l i n e region so f a r discussed, the results shown i n Table 3 be expected i f the degree of c r y s t a l l i n i t y of c e l l u l o s e i s increased. Table 3• V a r i a t i o n i n c e l l u l o s e properties as c r y s t a l l i n i t y increases (110) Increase Decrease density moisture regain Young's modulus dye sorption t e n s i l e strength chemical r e a c t i v i t y alpha-cellulose content swelling dimensional s t a b i l i t y elongation hardness f l e x i b i l i t y toughness EXPERIMENTAL METHOD A. Materials The study consists of three parts, as follows: Part I: C r y s t a l l i n i t y of normal wood of various ages and seasons, i . e . , summerwood and springwood. Part I I . C r y s t a l l i n i t y of reaction wood (compression wood and tension wood. Part I I I : C r y s t a l l i n i t y of decayed wood. For part I, a cross-section disc was taken from a 33-year old tree of western hemlock (Tsuga heterophylla (Raf.) Sarg.) at.a height ten feet above ground. Several small sample blocks were prepared from the 3 r d , 9 t h , 15th and 21st growth ring from the p i t h at. randomized positions within the r i n g , and separated with a c h i s e l into springwood and summerwood. The innermost portion (about 1 mm. thick) of each ri n g was taken as the springwood sample and the outmost portion (about 1 mm. thick) of each r i n g was taken to represent summerwood. Microscopic examination showed that the summer-wood sample contained about 50 percent of springwood trachelds. A f i b r e was considered as a springwood tracheid i f the r a d i a l width of i t s c e l l lumen exceeded twice the c e l l wall thickness. The compression wood used i n part II was obtained from an ^0-year old Douglas f i r (Pseudotsuga menzeisii (Mirb.) 43 Franco). The compression wood sample included the 15th to 18th growth ring s , whereas the normal wood sample taken from the diametrically opposed p o s i t i o n , included from the 13th to 21st growth rings from the. p i t h , which gave the same average age i n both cases. For the tension wood sample, a leaning 28-year old northern black cottonwood (Populus  trichocarpa Torr. and Gray) was sampled. Tension and normal wood samples taken at breast height on opposite sides were of the same age, i . e . , 20th to 24th years from the p i t h . The decayed wood specimens used i n Part III were obtained by treating sample blocks matched to those used i n Part II with two brown-rot organisms, Poria incrassata and Poria monticola. Treatment which caused about 6 percent weight loss due to Poria incrassata was designated as stage A, whereas that which resulted i n 15 percent weight loss due to Poria monticola was designated as stage B. B. S t a t i s t i c a l design In part I, two factors were involved. Factor A: Four d i f f e r e n t ages, i . e . , the 3 r d , 9 t h , 15th and 21st growth r i n g from the p i t h . Factor B: springwood vs, summerwood. Since the summerwood sample contained about 50 percent of springwood tracheids, which might have obscured the differences e x i s t i n g i n c r y s t a l l i n i t y between springwood and summerwood, the comparison of differences within factor B 44 r e q u i r e d h i g h e f f i c i e n c y . Therefore, a s p l i t p l o t design was a p p l i e d i n which f a c t o r A was assigned as the u n i t , w h i l e f a c t o r B was assigned as the sub-.urii.t w i t h three r e p l i c a t i o n s f o r X-ray system A (wood pulp) and two r e p l i c a t i o n s f o r X-ray system B ( h o l o c e l l u l o s e ) . I n p a r t I I , both X-ray method A (wood pulp) and X-ray method B ( h o l o c e l l u l o s e ) were used as a randomized block d e s i g n , w i t h three r e p l i c a t i o n s f o r the former and two. f o r the l a t t e r , r e s p e c t i v e l y . A s p l i t p l o t design was a l s o a p p l i e d i n part I I I , i n order to increase the e f f i c i e n c y f o r comparison of d i f f e r e n c e s w i t h i n treatment e f f e c t s . Thus: U n i t : Four types of wood, i . e . , cottonwood t e n s i o n wood, cottonwood normal wood, Douglas f i r compression wood and Douglas f i r normal wood. Sub-unit: Degree of decay, i . e . , stage A (approximately 6 percent weight l o s s ) , stage B (approximately 15 percent weight l o s s ) and c o n t r o l . Two r e p l i c a t i o n s were found to be s u f f i c i e n t to show d i f f e r e n c e s e x i s t i n g among types of wood and degree of decay. C. P r e p a r a t i o n of samples Wood pulp and h o l o c e l l u l o s e samples were prepared f o r parts I and I I of t h i s study, whereas only h o l o c e l l u l o s e was used f o r part I I I . The former was used to prepare a c y l i n d e r - t y p e specimen f o r X-ray method A, w h i l e h o l o c e l l u l o s e 45 was used to prepare a d i s c - t y p e specimen f o r X-ray method B. Procedures f o r p r e p a r a t i o n of these samples are given below. 1. Wood pulp sample The sample blocks were s p l i t along the g r a i n i n t o s m a l l p i e c e s , placed i n t e s t tubes and b o i l e d i n water f o r eig h t hours. The chips were then t r e a t e d w i t h a s o l u t i o n c o n t a i n i n g equal parts of 99»5 percent a c e t i c a c i d and 30-35 percent hydrogen peroxide. The tubes were submerged i n a hot water bath and heated at 100°C. f o r one hour. The samples were then washed w i t h s e v e r a l runs of water and shaken i n t o i n d i v i d u a l f i b r e s . The pulp thus obtained was thoroughly washed w i t h water f o r s e v e r a l days, to remove the l a s t t r a c e of a c i d , and f i n a l l y d r i e d at 50°C. A c y l i n d e r - t y p e specimen, 15 mm. i n le n g t h and 2 mm. i n diameter, was prepared f o r X-ray exposure. To prepare such a specimen, i t was necessary to separate the a i r - d r i e d pulp i n t o i n d i v i d u a l f i b r e s by a needle, i n order to e l i m i n a t e the e f f e c t of f i b r e o r i e n t a t i o n on X-ray d i f f r a c t i o n (3 ,46,65,72). E x a c t l y 50 mg. of separated f i b r e s were weighed and wetted w i t h d i s t i l l e d water. The f i b r e s were put i n t o a glas s tube w i t h an inner diameter of 2 mm. A s l i g h t pressure was a p p l i e d u n t i l the l e n g t h of the specimen was reduced to 15 mm. The tube c o n t a i n i n g the specimen was then d r i e d at 50°C. A f t e r two days, the specimen was pushed from the tube and d r i e d i n the open a i r . The specimen thus prepared was p e r f e c t l y 46 c y l i n d r i c a l and smooth; otherwise i t was rejected. 2. Holocellulose Wood meal was obtained by grinding the sample blocks with a Wiley m i l l . Since c r y s t a l l i n i t y w i l l decrease i f the size of p a r t i c l e i s too small, only the f r a c t i o n which passed through a 20 mesh, and was retained on a 35 mesh sieve, was c o l l e c t e d . A modification of the c h l o r i t e method of Wise,. Murphy and D'Addieco ( 162) , suggested by Dr. A.P. Yundt,^ was used for preparation of ho l o c e l l u l o s e . The procedure can be summarized b r i e f l y as follows. To 0 .7 g. of a i r - d r i e d wood meal i n an Erlenmeyer f l a s k of 60 ml. capacity, were added 10 ml. of stock solution "A" containing 60 g. of acetic acid and 20 g. of sodium hydroxide per l i t e r , and 1 ml. of stock solution "B" containing 200 g. of sodium c h l o r i t e per l i t e r . The mixture was well s t i r r e d and heated i n a hot water bath at 75°C. After . 7 5 , 1 .5 , and 2 . 5 hours, an additional 1 ml. of the stock solution "B" was added with s t i r r i n g . After 4 hours heating, the fl a s k was cooled i n ice water. Then 15 ml. of ice water was added, and the solution was removed by f i l t r a t i o n through mild suction. The residue was washed with 100 ml. of one percent acetic acid solution, followed by two 5 nil* portions of acetone, and dried i n the open a i r . ^Personal correspondence with Mr. J.M. Jaworsky. 47 One hundred and f i f t y mg. of the a i r - d r i e d h o l l o c e l l u l o s e were put into a s p e c i a l l y designed compression tube, and a gauge pressure of 1000 p s i was applied for f i v e minutes, using a laboratory press. The f i n a l disc-type specimen had a diameter of 14 mm. and a thickness of approximately 0 .75 mm. D. X-ray collimating system and procedure 1. Method A The p r i n c i p l e of the Debye-Scherrer powder technique was applied, as i l l u s t r a t e d i n Figure 2, page 48. This technique has been applied by Ant-Wuorinen (5) for determination of the c r y s t a l l i n i t y of c e l l u l o s e . The Cu K o alpha ray having a wave length of 1.54 A was monochromized by a n i c k e l f i l t e r and passed through a collimator. When t h i s incident ray str i k e s the specimen rotating at one rpm, i t produces symmetrical interference rings on the f i l m . The specimen was set exactly at the center of the camera so that a maximum, constant amount of f i b r e s were exposed to the X-ray. In order to create an unexposed area, the f i l m was covered with a piece of lead f o i l at the i n l e t bottom of the collimator. This unexposed area gives a zero reading for the densitometer c a l i b r a t i o n to be described l a t e r . A P h i l i p s X-ray machine (No. 12045) was operated at a voltage of 45 k i l o v o l t s and current density of 15 milliamperes. The machine was allowed to warm up for 30 minutes p r i o r to il-8 FIGURE 2. CAMERA ARRANGEMENT FOR T H E DEBYE-SCHERRER POWDER TECHNIQUE 3 0 | _ , , r-O 10 20 30 4 0 T \ M E ( M I N ) FIGURE 3. EFFECT OF X - R A Y EXPOSURE TIME ON CRYSTALLINITY INDEX 49 i n t r o d u c i n g the f i r s t sample. I n o r d e r t o de t e r m i n e t h e optimum exposure t i m e , a p r e l i m i n a r y experiment was c a r r i e d o u t . The r e s u l t s shown i n F i g u r e 3 , page 4 8 , i n d i c a t e an optimum exposure t i m e o f 20 m i n u t e s . Kodak m e d i c a l s a f e t y X - r a y f i l m was used. The f i l m was d e v e l o p e d by Kodak X - r a y d e v e l o p e r D-19 f o r 5 m i n u t e s , f i x e d i n Kodak f i x e r f o r 10 m i n u t e s , and hung up f o r d r y i n g . The X - r a y diagram thus o b t a i n e d i s shown i n F i g u r e 4 . F i g u r e 4 . Wood p u l p X - r a y diagram To o b t a i n q u a n t i t a t i v e d a t a on t h e i n t e n s i t y of the d i f f r a c t i o n p a t t e r n , a p h o t o v o l t e l e c t r o n i c d e n s i t o m e t e r (Model 525) was used. The z e r o r e a d i n g of the d e n s i t o m e t e r was c a l i b r a t e d by the unexposed a r e a o f the f i l m and i t s 100 p e r c e n t r e a d i n g , by p u t t i n g a p i e c e o f l e a d f o i l on t h e f i l m . The 50 f i l m was mounted on a microscope equipped with a stage micrometer which controlled p r e c i s e l y the movement of f i l m . The i n t e n s i t y reading at inter v a l s of 0 .2 mm. along the equator of the interference r i n g was plotted against the angle of r e f l e c t i o n (2Q) on graph paper. Since the inner diameter of the powder camera was 114.83 mm., one degree of the 26 corresponded to one millimeter on the f i l m . The i n t e n s i t y curve thus obtained was the same as that obtained by method B shown i n Figure 6 , page $1. 2. Method B A Geiger-counter X-ray spectrometer, type No. 12021, was used i n th i s system. The spectrometer geometry i s shown i n Figure 5« A specimen was mounted on the glass specimen holder and f i t t e d onto the sample post. The X-ray, which had been collimated by s l i t 1 (7 mm. x 1.5 mm.), h i t the specimen and created an angle of r e f l e c t i o n (2©) as shown i n Figure 5» The d i f f r a c t e d ray was then f i l t e r e d by a n i c k e l f i l t e r and passed through s l i t 2 (4 mm. x 0 . 5 mm.) into a goniometer. The i n t e n s i t y of the d i f f r a c t e d beam registered by a goniometer was recorded automatically by a Brown Recorder (Model 153)• A motor, attached to the end of the goniometer, drove i t at a constant speed of \ rpm from r e f l e c t i o n angles of 90° to 0 ° . The gear arm was set to run through a range of 32° to 10° only. The chart of the recorder was driven by a synchronous motor and could be ca l i b r a t e d d i r e c t l y i n degrees per minute. The recorded chart, therefore, furnished a graph containing a 51 A - S O U R C E OF X-RAYS B-COLLIMATING SLIT NO. I C - SPECIMEN O - N I C K E L FILTER E - COLLIMATING SLIT NO.2 F - GONIOMETER G - M O T O R DRIVE 26-ANGLE OF REFLECTION FIGURE 5. S P E C T R O M E T E R GEOMETRY 10 20 3 0 2 O ( D E G R E E S ) FIGURE 6. X-RAY DIFFRACTION SPECTRUM 8 — THE BREADTH OF T H E 0 0 2 PEAK IN RADIANS 52 series of peaks proportional to the i n t e n s i t y of the d i f f r a c t e d X-ray beam plotted against the angle of r e f l e c t i o n ( 2 0 ) . The X-ray machine was operated from a normal 20 v o l t , 60 cycle source of supply. The magnification scale on the Brown Recorder was set at 50. The d i f f r a c t i o n pattern thus obtained i s shown i n Figure 5« E. Evaluation of c r y s t a l l i n i t y Since the primary purpose of t h i s study was to compare the r e l a t i v e v a r i a t i o n of c r y s t a l l i n i t y among ce r t a i n types of samples under t e s t , no attempt was made to evaluate the absolute c r y s t a l l i n i t y . C r y s t a l l i n i t y was evaluated as a c r y s t a l l i n i t y index i n X-ray method A (wood pulp), and c r y s t a l l i n i t y r a t i o i n X-ray method B (h o l o c e l l u l o s e ) . The f ormulae rapplied are shown below. I. C r y s t a l l i n i t y index C r y s t a l l i n i t y index (Cr. I . ) = (1 - 100 B ) 100, I 0 0 2 " Imin. where B i s the breadth of the 002 peak expressed i n radians, I Q Q 2 i s the maximum i n t e n s i t y of the 002 peak i n a r b i t r a r y units, and I m i n > i s the minimum i n t e n s i t y between the 002 peak and the (101 + 101) peak i n the same a r b i t r a r y u n i t s . This formula was developed by Ant-Wuorinen (5) and has been applied i n studies of r e l a t i v e t r a n s i t i o n of c r y s t a l l i n i t y due to various treatments (72). Because of the li m i t e d accuracy i n 5 3 the measurement of i n t e n s i t y by the densitometer, the index was reported to one decimal only. 2. C r y s t a l l i n i t y r a t i o C r y s t a l l i n i t y r a t i o (Cr. R.) = 1 (101 + 101) x 100, 1 (101 + 101) + I m i n . where I(IQI + 101) i s t i i e m a x i m u m i n t e n s i t y of the combined (101 + 101) peak, and I M I N # i s the minimum i n t e n s i t y between the 002 peak and the (101 + 101) peak i n a r b i t r a r y u n i t s . The i n t e n s i t y should be corrected by subtracting background i n t e n s i t y , i f the claim of Anker-Rasch and McCarthy ( 3 ) i s v a l i d . Since the nature of the specimen holder used i n the i r experiment was d i f f e r e n t from that used i n th i s experiment, i t was necessary to determine whether a background correction was necessary. To do t h i s , two d i f f r a c t i o n i n t e n s i t y charts were prepared, one with both specimen and sample holder, the other, with the specimen only. Comparison of these two charts showed that the former gave a s l i g h t l y higher i n t e n s i t y on the average due to some r e f l e c t i o n caused by a specimen holder, but the difference was so small that i t could be neglected. Accordingly, the i n t e n s i t y was corrected by subtracting the i n i t i a l reading from the I(IQ^ + IQT) and I M L R U reading on the i n t e n s i t y chart. The c r y s t a l l i n i t y r a t i o thus calculated was reported to the nearest hundredth. I RESULTS AND DISCUSSION A. Part It The degree of c r y s t a l l i n i t y of pulp and holocellulose of normal wood 1. Results The re s u l t s shown i n Table 4, page 55> and Figure 7, page 56» indicate that c r y s t a l l i n i t y of both wood pulp and holocellulose increases with age from p i t h for about 15 years, then reaches a more or less constant value. The c r y s t a l l i n i t y of summerwood pulp and of holoce l l u l o s e , i s also higher than that of the comparable springwood specimens. These differences i n c r y s t a l l i n i t y are found to be c l e a r l y s i g n i f i c a n t on analysis of variance, as shown i n Table 5j page 57» Further analysis shows that the difference i n c r y s t a l l i n i t y between the 15th and the 21st growth rings i s non-significant. This implies that the c r y s t a l l i n i t y of juvenile wood tracheids increases with age, whereas that of mature wood tracheids i s more constant, exhibiting n e g l i g i b l e v a r i a t i o n . Maturity i n t h i s case i s defined as the age at which the curve of c r y s t a l l i n i t y v s age f l a t t e n s . The numerical value of c r y s t a l l i n i t y index and c r y s t a l l i n i t y r a t i o obtained i n th i s study i s considerably lower than those obtained by other workers. The range of c r y s t a l l i n i t y index of wood pulp i n the present r e s u l t i s 55 Table 4 . E f f e c t of age and season on c r y s t a l l i n i t y of wood pulp and holocellulose Season C r y s t a l l i n i t y index Speci- -X-ray method A-men (wood pulp) C r y s t a l l i n i t y r a t i o -X-ray method B-(holocellulose) 3 + 9 15 21 3 9 15 21 Summer-wood 1 2 3 av. 53.4 55.4 56.3 58.1 53-3 54.2 57.5 58.0 53-0 54.9 57.3 56.9 53.2 54.8 57.0 57.7 54.56 54.88 55.51 55.52 54.31 54.73 55.28 55.63 54.44 54.81 55.40 55.58 Spring-wood 1 2 3 av. 53.1 55.0 57.0 56.5 52.0 54.4 56.3 56.4 52.2 54.6 56.4 56.2 52.4 54.7 56.6 56.4 54.31 54.65 55.06 54.89 54.21 54.76 55.00 55.05 54.26 54.71 55.03 54.97 •Age from p i t h , years. 52.0 to 5 8 . 1 , whereas that obtained by Ant-Wuorinen (5) i s 63.O (bleached sulphite wood pulp), and that by Kouris, Ruck and Mason (72) i s 70.6 (softwood dissolving wood pulp). The range of c r y s t a l l i n i t y r a t i o of holocellulose obtained i n the present r e s u l t i s 54.21 to 55*63, whereas that obtained by Anker-Rasch and McCarthy (3) i s about 6 4 . 5 (bleached sulphite c e l l u l o s e containing 96.7 percent alpha-cellulose) to 65 .0 (bleached k r a f t c e l l u l o s e containing 93 .4 percent alpha-c e l l u l o s e ) . These are mainly due to the d i f f e r e n t types of c e l l u l o s e examined. The increase i n c r y s t a l l i n i t y of wood tracheids during the immature stage (from the p i t h to the 15th growth ( A ) W O O D P U L P - C R Y S T A L L I N I T Y I N D E X 5 8 5 7 X w O 5 6 z £ 5 5 z H W >" 5 3 o 52 51 — • — S U M M E R W O O D — O - - S P R I N G W O O D 15 21 (B) HOLOCELLULOSE - CRYSTALLINITY RATIO 5 6 < X 5 5 J >-H Z _ J _ J < W 5 4 or o 5 3 — • — SUMMERWOOD — O - - SPRINGWOOD F I G U R E 7 . V A R I A T I O N O F C R Y S T A L L I N I T Y W I T H A G E A N D S E A S O N I N N O R M A L W O O D 57 Table 5« Analysis of variance of c r y s t a l l i n i t y i n Table 4 (A) C r y s t a l l i n i t y index (wood pulp) Source of variance D. F. S. S. M. S» F Unit: r e p l i c a t i o n 2 0.77 O .385 1.774- N.S, age 3 69.44 23.147 106.668 * * * error 6 I . 3 0 0.217 Sub unit: season 1 2 .80 2.800 13.462 ** AxS 3 1.07 0.357 1.716 N.S, error 8 1.66 0.208 T o t a l 23 77.04 ** S i g n i f i c a n t at 1. percent, l e v e l *** S i g n i f i c a n t at 0 .1 percent l e v e l N.S. Non-significant (B) C r y s t a l l i n i t y r a t i o (holocellulose) Source of v a r i a t i o n D.F. S.S. M. S. F Unit: r e p l i c a t i o n 1 0.011 0.011 0.550 N.S. age 3 2.251 0.750 37.500 * * error 3 0.059 0.020 Subunit: season 1 O.388 O.388 48 .500 ** A x S 3 0.152 0.051 6.375 N.S. error 4 0 .030 0.008 Total 15 2.891 * * S i g n i f i e a n t at 1 percent l e v e l N.S. Non-significant 58 ring) seems to follow a constant increment. This means that the apparent degree of c r y s t a l l i n i t y might be correlated with age, i f the influence of prepared f i b r e orientation i n the samples could be discounted. Such preferred orientation of f i b r e has been found to give r i s e to-unpredictable changes i n r e l a t i v e i n t e n s i t y of the corresponding interference pattern (46). Neglect of t h i s e f f e c t during the X-ray exposure w i l l cause a misleading Interpretation i n the experimental r e s u l t s ( 3 , 4 6 , 6 5 , 7 2 ) • The orientation e f f e c t was minimized i n method A by c a r e f u l preparation of sample, and r o t a t i o n of specimen during the X-ray exposure. In method B, no r o t a t i o n was . applied during the X-ray exposure, so that only two-dimensional randomness of f i b r e was achieved rather than a three-dimensional one. A s l i g h t orientation e f f e c t was apparently inevitable i n both X-ray methods. Since' the present r e s u l t s are i n good agreement with those obtained by Tanlguchi (142), i n which the orientation e f f e c t may be completely ruled out by the acid hydrolysis method, the r e s u l t s can hardly be considered as s o l e l y a t t r i b u t a b l e to the orientation e f f e c t . I t could be assumed that difference i n c r y s t a l l i n i t y might ac t u a l l y exist among ages i n the juvenile wood. Evidence supporting t h i s point of view i s shown below. 59 (a) Tensile strength Wardrop (152) has I l l u s t r a t e d that t e n s i l e strength of tracheids increases with tree age. Since an increase i n t e n s i l e strength i s usually accompanied by an increase i n c r y s t a l l i n i t y , i t i s t h e o r e t i c a l l y acceptable that the c r y s t a l l i n i t y increases with age. But t h i s does not necessarily mean that an increase i n t e n s i l e strength i s s o l e l y a t t r i b u t a b l e to an increase i n c r y s t a l l i n i t y . F i b r i l angle and c e l l u l o s e molecular chain length d i s t r i b u t i o n are also important i n t h i s respect. (b) Alpha-cellulose content I t has been shown that Cross and Bevan c e l l u l o s e content ( 7 0 , 1 5 2 ) , or holocellulose content (164), increases with age for a given period i n certa i n species. Since there i s a strong p o s i t i v e c o r r e l a t i o n between alpha-cellulose content and holocellulose content (164), as well as the Cross and Bevan c e l l u l o s e content (70), i t may be assumed that the alpha-cellulose content increases with age. I f thi s i s true, then the c r y s t a l l i n i t y can be expected to increase with age, since a c e l l u l o s e of high alpha-cellulose content always gives a high degree of c r y s t a l l i n i t y ( 2 2 ) . c f . page.38. 60 (c) Moisture regain The higher the c r y s t a l l i n i t y , the lower the moisture regain w i l l be.? Moisture regain data obtained by Wardrop (152) showed i t to decrease with age. This indicates the following two p o s s i b i l i t i e s : i ) C r y s t a l l i n i t y might increase with age so that moisture regain would decrease with age. i i ) The hemicellulose f r a c t i o n could decrease with age. In t h i s instance, moisture regain would also decrease with age. o I t has been noted by Ranby (11) that the lower l a t t i c e order of wood c e l l u l o s e , as compared with that of cotton c e l l u l o s e , should be due to the presence of other monosaccharides i n the c e l l u l o s e chains. Conrad and Scroggie (22) also claimed that an increase i n a c c e s s i b i l i t y w i l l occur when r e l a t i v e l y low-molecular-weight materials such as beta and gamma c e l l u l o s e are present. I f these workers are correct, then holocellulose near the p i t h , which contains higher hemicellulose as revealed by Zobel et a l (165), should give lower c r y s t a l l i n i t y . ' This i s i n good agreement with the present r e s u l t s . Thus both of the above mentioned p o s s i b i l i t i e s are t h e o r e t i c a l l y acceptable. The present r e s u l t s disagree with those obtained by Preston, Hermans and Weidinger (113) , who found that the 7 c f . Table 3 61 c r y s t a l l i n e - n o n - c r y s t a l l i n e r a t i o decreased with age. The samples used i n t h e i r study were Cross and Bevan c e l l u l o s e . According to the standard procedure for preparing the Cross and Bevan c e l l u l o s e , the sample should be d e l i g n i f i e d u n t i l an end-point reached. The time of d e l i g n i f i c a t i o n required to reach th i s end-point f o r various samples i s var i a b l e . I f a sample taken near the p i t h i s assumed to have a higher l i g n i n content than one near the bark, then the time of d e l i g n i f i c a t i o n for the former should be r e l a t i v e l y long, and the duration of r e c r y s t a l l i z a t i o n of c e l l u l o s e chains during the d e l i g n i f i c a t i o n would be considerably prolonged. Consequently, the c e l l u l o s e thus prepared might give higher c r y s t a l l i n i t y as compared with the one near the bark, even .though the i n i t i a l c r y s t a l l i n i t y was i d e n t i c a l for both samples. In both the present experiment and that of Taniguchi (142), time of d e l i g n i f i c a t i o n was kept constant. The f i n a l l i g n i n content of each sample might therefore be variable since no end-point technique was applied. Thus the lower value of c r y s t a l l i n i t y observed near the p i t h may be due to a s l i g h t l y higher l i g n i n content i n the pulp sample. The v a r i a t i o n of extractive content may also a f f e c t the f i n a l •J r e s u l t since i t w i l l influence the rate of penetration of chemicals, which i n turn gives d i f f e r e n t degrees of d e l i g n i f i c a t i o n . I f i t i s assumed that extractive content i s higher near the p i t h , then i t s d e l i g n i f i c a t i o n would be 62 poorer than that near the bark when the time of d e l i g n i f i c a t i o n Is kept constant for both samples. It i s apparent that the method of sample preparation w i l l c r i t i c a l l y a f f e c t the f i n a l r e s u l t s and w i l l lead to d i f f e r e n t i n t e r pretations. The observation that summerwood has higher c r y s t a l l i n i t y than springwood i s i n good agreement with Holzer and Lewis ( 5 7 ) , and Lindgren ( 7 7 ) . The difference i n c r y s t a l l i n i t y between summerwood and springwood i s smaller than was expected. This might be due to the fact that the summerwood sample contained about 50 percent of springwood tracheids because of inaccuracy i n dis s e c t i o n and to the anatomical c h a r a c t e r i s t i c s of a wood such as western hemlock. Using the same argument of the previous paragraph, one might expect summerwood to be of higher c r y s t a l l i n i t y , since i t contains a lower proportion of l i g n i n than springwood. Thus at the end of a given time of d e l i g n i f i c a t i o n , less l i g n i n might have been removed from the r e l a t i v e l y l i g n i n - r i e h springwood. 2. Probable mechanism of v a r i a b i l i t y of c r y s t a l l i n i t y i n wood The mechanism of v a r i a b i l i t y of c r y s t a l l i n i t y with age and season i s unknown, because of the inadequate information available about the mechanism of the formation of ce l l u l o s e c r y s t a l l i t e s and f i b r i l s of the c e l l w a l l . Wardrop (153) has proposed that c r y s t a l l i z a t i o n of c e l l u l o s e i s f a c i l i t a t e d by the absence of l i g n i n , based on the fac t that 6 3 c e l l u l o s e displays i t s highest c r y s t a l l i n i t y value when the l i g n i n content i s low. I f t h i s hypothesis i s correct, summerwood c e l l u l o s e should be more highly c r y s t a l l i z e d than springwood c e l l u l o s e because the proportion of c e l l u l o s e i n the summerwood has been found to be higher than that of springwood, while the proportion of l i g n i n i n summerwood i s lower than that of springwood (Il6,l61). C r y s t a l l i n i t y might also increase with age i n juvenile wood, since the c e l l u l o s e content has been shown to increase with age for given periods i n c e r t a i n species (70,152,164). The hypothesis proposed by Wardrop remains to be proved. B. Part I I : "• The degree of c r y s t a l l i n i t y of pulp and holocellulose from reaction wood as compared  to normal wood , • • 1. Results The c r y s t a l l i r i i t i e s of pulp and holocellulose of reaction wood as compared to those of normal wood are shown i n Table 6, page 64. Analysis of variance (Table 7, page 64) shows that c r y s t a l l i n i t y of compression wood fi b r e s and holocellulose i s s i g n i f i c a n t l y lower than that of normal wood, while c r y s t a l l i n i t y of tension wood i s s i g n i f i c a n t l y higher than that of normal wood i n the form of both pulp and hol o c e l l u l o s e . These are discussed separately below. 64 Table 6 . C r y s t a l l i n i t i e s of reaction wood C r y s t a l l i n i t y index C r y s t a l l i n i t y r a t i o R e p l i - -X-ray method A- --X-ray method B-cation (wood pulp) (holocellulose) C-T* C-N D-N D-C C-T C-N D-N D-C 1 2 3 av. 6 ? . 8 55.4 54.9 4 7 . 5 66.2 54.8 54.1 4 6 . 5 6 5 . 8 54.8 53.9 45 .2 66.6 55.0 54.3 4 6 . 4 1 57.74 54.55 53.84 52.86 57.71 54.35 53.79 52.41 57.73 54.45 53.82 52.64 •C-T represents cottonwood tension wood C-N represents cottonwood normal wood D-N represents Douglas f i r normal wood D-C represents Douglas f i r compression wood Table 7 . Analysis of variance of c r y s t a l l i n i t y i n Table 6 (A) C r y s t a l l i n i t y index (wood pulp) Source of v a r i a t i o n D. F. s. s. M. S. F R e p l i c a t i o n Type of wood Error Total 2 11 • . , 4 .535 623.062 1.165 628.762 2.268 207.687 0.194 11.691 1070.552 ** *** • • S i g n i f i c a n t at 1 percent l e v e l • • • S i g n i f i c a n t at 0 .1 percent l e v e l (B) C r y s t a l l i n i t y r a t i o (holocellulose) Source of v a r i a t i o n D. F. s. S. M. S. F Replication Type of wood Error Total 1 3 3 7 O.O67 28.506 0.056 28.629 O.O67 9.502 0.019 3.526 500.114 N.S. *** ••• S i g n i f i c a n t at 0 .1 percent l e v e l N.S. Non-significant 65 2. Compression wood The present r e s u l t s might be expected i n view of the lower alpha-cellulose content, higher longitudinal shrinkage and lower strength values observed i n compression wood. The c o r r e l a t i o n of these three properties to low degree of c r y s t a l l i n i t y has been discussed previously.^ The present discussion w i l l be confined to the problem as to why the c r y s t a l l i n i t y i n compression wood should be low. In compression wood, the decreased tracheid length i s usually accompanied by an increase i n f i b r i l angle. These att r i b u t e s are associated with an increased number of oblique a n t i c l i n a l d i v i s i o n s i n the cambium, occasioned by the increased r a d i a l growth rate (156). I t has been pointed out that vigorous r a d i a l growth i s achieved by p e r i c l i n a l d i v i s i o n of the fusiform i n i t i a l s of the cambium (111) . Thus, i f rapid p e r i c l i n a l d i v i s i o n i s accompanied by an increased number of oblique a n t i c l i n a l d i v i s i o n s , then a wider growth ri n g w i l l produce shorter tracheids (155)• This implies that f i b r i l angle as well as f i b r e length are simply a function of rate of change of growth i n circumference. Since the same relationships are found i n the juvenile wood, i t follows that the re l a t i o n s h i p of f i b r i l angle and f i b r e length to growth rate holds f o r both normal wood and compression wood. Accordingly, there would be no 8 c f . Table 3 . 66 appreciable differences i n f i b r i l angle between two tracheids as long as they are formed i n a ring of the same growth rate, i r r e s p e c t i v e of age or wood condition. This i s confirmed by Wardrop and Dadswell ( 1 5 5 )J who claimed that compression wood tracheids are apparently no d i f f e r e n t from normal wood tracheids of the same length so far as the f i b r i l angle of the layer S2 i s concerned. From t h i s point of view, compression wood may be considered more juvenile than adjacent wood of the same age. The properties of compression and juvenile wood compared to normal, mature wood show that both juvenile wood and compression wood have lower c e l l u l o s e content, tracheid length, t e n s i l e strength, and higher f i b r i l angle, lon g i t u d i n a l shrinkage and l i g n i n content. Consequently, the previous assumption that compression wood can be regarded more juvenile than adjacent normal wood seems acceptable. Under t h i s assumption, compression wood should, t h e o r e t i c a l l y , give lower c r y s t a l l i n i t y as observed i n the present study. 3 . Tension wood The high degree of c r y s t a l l i n i t y of ce l l u l o s e found i n tension wood as compared with normal wood i s i n good agreement with the work of Wardrop and Dadswell (11,153,154, 157) .^ The structure of tension wood has been well established by means of p o l a r i z i n g microscopy and X-ray d i f f r a c t i o n 9NO numerical data were given i n th e i r r e s u l t s . 67 (154,157)• I n b r i e f , there exists a thick inner gelatinous layer i n addition to the layers S I , S2 and S3, or the S3 layer, or both S2 and S3 layers, may be lacking. The f i b r i l angle i n t h i s a d d i t i o n a l layer has been shown to be approximately 5° with respect to the longitudinal axis of f i b r e . Further evidence has shown that t h i s layer i s u n l i g n i f i e d and that i t s c e l l u l o s e i s i n a highly c r y s t a l l i n e state. On reviewing c h a r a c t e r i s t i c s of tension wood, the question may be raised as to whether the high c r y s t a l l i n i t y of ce l l u l o s e i n tension wood i s at t r i b u t a b l e to a l l layers of the secondary wall or s o l e l y to the addit i o n a l gelatinous l a y e r . Wardrop and Dadswell (157) have studied t h i s problem from the point of view of equilibrium moisture content, density, and sharpness of an X-ray d i f f r a c t i o n pattern. They f i n a l l y concluded that the high degree of c r y s t a l l i n i t y of c e l l u l o s e i n tension wood was s o l e l y a t t r i b u t a b l e to a greater degree of l a t e r a l order i n the c r y s t a l l i n e region of the gelatinous layer, whereas the pa r a c r y s t a l l i n e phase (or the amorphous phase) of the rest of the layers was sim i l a r i n both normal and tension wood. Since tension wood consists of c e l l u l o s e of high c r y s t a l l i n i t y , i t should possess a l l the c h a r a c t e r i s t i c s of highly c r y s t a l l i n e c e l l u l o s e given i n Table 2. There are several deviations from t h i s t h e o r e t i c a l expectation however: abnormally high lo n g i t u d i n a l shrinkage ( 1 7,20,24 , 1 5 4 ) , low 68 strength values for f i b r e stress at the proportional l i m i t of bending, modulus of rupture, modulus of e l a s t i c i t y , work to the proportional l i m i t , work to ultimate load and longitudinal shear ( 1 3 ) . Tension wood does not decrease the toughness ( 1 9 ) , which i s supposed to be lower i f c r y s t a l l i n i t y of c e l l u l o s e i s high.- 1 , 0 Several workers (17,19,154) have suggested possible explanations, but further investigations are required. Even some chemical properties of tension wood are at variance with those expected. For instance, the alpha-c e l l u l o s e content of tension wood i s s i g n i f i c a n t l y higher than that of normal wood, whereas the pentosan content i s lower ( 1 7 ) . Thus some workers pointed out that the c e l l u l o s e i n tension wood was of longer molecular chain than the c e l l u l o s e i n normal wood ( 1 7 ) . Nevertheless, the degree of polymerization found i n the holocellulose of tension wood was reported to be lower than that of normal wood ( 11) . I t i s clear now that a single factor such as c r y s t a l l i n i t y , which i s found to be strongly correlated with physical and chemical properties of c e l l u l o s e and wood under normal conditions, cannot be applied to explain the behavior of reaction wood without considering the effects of some other f a c t o r s . Gross anatomical structure also has a role as important as f i n e structure. i U A sim i l a r abnormality can also be found i n compression wood, which has a lower c r y s t a l l i n i t y accompanied by a very low value of toughness. 69 c « Part I I I : The degree of c r y s t a l l i n i t y of holocellulose of decayed wood 1. Results Some of the X-ray spectra of decayed wood holocellulose are shown i n Figure 8 , page 71 . The v a r i a t i o n i n the c r y s t a l l i n i t y r a t i o of wood holocellulose due to decay i s shown i n Table 8 , page 7 0 , and Figure 9 , page 72 . Analysis of variance (Table 9 , page 70) indicates that both decay and type of wood are c l e a r l y s i g n i f i c a n t at 0 . 1 percent l e v e l . Further analysis shows the following: (a) C r y s t a l l i n i t y of holocellulose i s greatly increased due to decay i n both normal and reaction wood. (b) The r e l a t i v e magnitude of increase i n c r y s t a l l i n i t y i s approximately i d e n t i c a l f or each type of wood. Thus the order of decreasing c r y s t a l l i n i t y a f t e r decay remains the same as that of the controls. The order of c r y s t a l l i n i t y of d i f f e r e n t types of decayed wood depends mainly on the i n i t i a l c r y s t a l l i n i t y of wood rather than on the hi s t o r y of decay. (c) The rate of increase i n c r y s t a l l i n i t y i s very rapid i n the e a r l i e r stage of decay, represented by a 6 percent weight l o s s , but I t levels to almost constant c r y s t a l l i n i t y thereafter except i n compression wood, where c r y s t a l l i n i t y i s s t i l l increasing to stage B, but at a slower rat e . In this l a t t e r case, the increase i s s t a t i s t i c a l l y s i g n i f i c a n t . 70 Table 8 . C r y s t a l l i n i t y r a t i o of holocellulose of decayed wood R e p l i - Decay Decay Type of wood cation Control stage A stage B Cottonwood tension wood 1 2 av. 57.74 57-71 57.73 59.7O 59.50 . 59.60 59.56 59.70 59.63 Cottonwood normal wood 1 2 av. 54 .35 54 .55 54.45 55.95 55.83 55.89 55.90 56.17 56.04 Douglas f i r normal wood 1 2 av. * 53.84 53.79 53.82 54.50 54.71 ' 54.61 54.65 54.59 54.62 Douglas f i r compression wood 1 2 av. 52.41 . 52.86 52.64 53.46 53.32 53.88 53.83 Table 9 . Analysis of variance of c r y s t a l l i n i t y r a t i o i n Table 8 Source of v a r i a t i o n D. F. S. S. M. S. Unit: r e p l i c a t i o n 1 0 .061 0 .061 ' 2 .179 N.S. type of wood 3 111.009 37.003 I3215.OOO *** error 3 O.O83 0.028 Subunit: treatment 2 8.911 4.456 278.500 * * * t x w 6 I.I98 0.200 I2.50O ** error 8 0 . 125 0 .016 Total ' 23 I 2 I . 3 8 7 ** S i g n i f i c a n t at 1 percent l e v e l *** S i g n i f i c a n t at 0.1,.percent l e v e l N.S. Non-significant 71 i — i • > • 10 2 0 3 0 2 9 ( D E G R E E S ) FIGURE 8. X - R A Y DIFFRACTION SPECTRA O F DOUGLAS FIR H O L O C E L L U L O S E A . DECAYED NORMAL W O O D , S T A G E B B. DECAYED COMPRESSION WOOD, S T A G E B C COMPRESSION WOOD, CONTROL 72 F I G U R E 9. E F F E C T OF DECAY AND TYPE O F WOOD ON CRYSTALLINITY RATIO OF H O L O C E L L U L O S E C - T COTTONWOOD TENSION WOOD C - N COTTONWOOD NORMAL WOOD D - N DOUGLAS FIR NORMAL WOOD D - C DOUGLAS FIR COMPRESSION WOOD 73 In order to understand the probable mechanism behind these experimental r e s u l t s , the biochemical transformation of c e l l u l o s e and wood which may occur during decay should be reviewed. 2 . Biochemical transformation of c e l l u l o s e Though much has been learned regarding the enzymatic degradation of cotton and modified c e l l u l o s e , enzymatic breakdown of whole wood i s less well understood. This i s due to the r e l a t i v e complexity of wood compared to other c e l l u l o s i c materials, and the inadequacy of present knowledge of the chemical structure of wood, i n p a r t i c u l a r of the l i g n i n . The following presentation i s based primarily on enzymatic degradation of c e l l u l o s e rather than wood. The energy that hyphae require for growth i s derived from that available i n glucose. This energy i s made available to hyphae by the phy s i o l o g i c a l oxidation, i n which one mole of glucose provides a t h e o r e t i c a l amount of energy equivalent to 676.6 k c a l . (131) . C 6 H 1 2 ° 6 + 6 0 2 • 6 H 20 + 6 C0 2 A F = -676.6 k c a l . In order for t h i s reaction to proceed, c e l l u l o s e must be transformed to glucose. The biochemical transformation of c e l l u l o s e into glucose includes two major steps. Step 1: Transformation of the native c e l l u l o s e into i n d i v i d u a l l i n e a r c e l l u l o s e molecules by s p l i t t i n g of the three-dimensional cross-linkage. Step 2: Breakdown of the l i n e a r c e l l u l o s e chains into glucose. 74 Both of these reactions are ca r r i e d out by enzymes secreted by hyphae. Recent studies (76,115) have shown that there are at least two types of enzymes which are responsible for the biochemical transformation of c e l l u l o s e molecules. The f i r s t type of enzyme i s responsible for making c e l l u l o s e molecules available for reaction, corresponding to step 1, while the second type of enzyme i s responsible for hydrolysis of the l i n e a r polysaccharide into sugars, corresponding to step 2 . The former type i s known as c e l l u l a s e (130), whereas the l a t t e r i s named Cx (115) . The condensed stepwise transformation i s i l l u s t r a t e d i n Table 10. Table 10. Stepwise biochemical transformation of ce l l u l o s e into glucose (131) Native c e l l u l o s e (cotton) 1 , c r y s t a l l i n e region amorphous region (slow) (rapid) ... rupture of H-bonds, van der Waals forces, by c e l l u l a s e Linear Polysaccharide ... Polysaccharidase enzyme, Cx, acting Cellobiose ... Cellobiase acting Absorption into organism 75 In the case of wood, only r e s t r i c t e d groups of fungi are able to u t i l i z e i t for food. The nature of the association between c e l l u l o s e and l i g n i n of wood i s primarily responsible for such r e s t r i c t i o n . It has been suggested that the biochemical transformation of wood c e l l u l o s e into l i n e a r polysaccharides Is carried out by an unknown factor "X" presumably enzyma.tic, possessed only by fungi adapted to t h i s type of substance ( 2 3 ) . The symbol "X" has been used to i d e n t i f y the as-yet-unknown enzymes responsible for t h i s transformation. Absence of t h i s factor accounts for the i n a b i l i t y of non-wood-destroying fungi to u t i l i z e wood for food. The transformation from l i n e a r polysaccharides to glucose i s the same as that of native cotton ( 2 3 ) . 3 . Preference of enzymic attack Evidence indicates that the enzymic degradation of c e l l u l o s e starts preferably from the amorphous region rather than randomly. On the basis of.a d i f f e r e n t i a l energy require-ment, the amorphous region i s preferable to the c r y s t a l l i n e region because much less energy w i l l be required to dislodge a c e l l u l o s e chain i n the former (131). Assuming that, the action of the enzymes i s s i m i l a r to that of d i l u t e mineral a c i d as described previously, i t i s reasonable to presume that the reaction starts i n the amorphous region and extends gradually i n t o the c r y s t a l l i n e region. Several workers (106,107,149) have demonstrated the s i m i l a r i t y of acid and enzymatic hydrolysis by comparing the rate of hydrolysis. Walseth (150) 76 made use of t h i s c h a r a c t e r i s t i c to determine the a c c e s s i b i l i t y of c e l l u l o s e , and h i s r e s u l t s were i n good agreement with those obtained by acid hydrolysis. Norkrans and Ranby (106,107) also claimed that the enzymatic degradation apparently occurred i n e a s i l y accessible regions of the c e l l u l o s e aggregates, leaving more re s i s t a n t p a r t i c l e s , and therefore better c r y s t a l l i z e d c e l l u l o s e , as a residue. I t has been shown (8) that there are c e r t a i n wood-destroying fungi whose hyphae advance by producing h e l i c a l l y oriented c a v i t i e s within the thick secondary wall of f i b r e s . Such c a v i t i e s are of two p r i n c i p a l geometric forms. They may be b i c o n i c a l or c y l i n d r i c a l , with conical ends, and are oriented p a r a l l e l to the long axis of the f i b r i l . In some cases they may be oriented at an angle of 20 to 25 degrees to the axis of the f i b r i l . These c a v i t i e s were found tcr be the r e s u l t of hydrolysis of c e l l u l o s e through enzymatic a c t i v i t y . The reaction takes place i n the amorphous region f i r s t , and leaves the c r y s t a l l i n e region e n t i r e l y i n t a c t , so that the external shape of the m i c r o f i b r i l and f i b r i l i s maintained. I t i s now clear that the i n i t i a l enzymatic reaction starts from the amorphous region. This preference i s believed to be the most probable factor r e s u l t i n g i n the rapid increase i n c r y s t a l l i n i t y during the e a r l i e r stage of decay observed i n t h i s study. The increase i n c r y s t a l l i n i t y may be attributed to either or both of the following factors: 77 (a) Removal of the amorphous materials. (b) R e c r y s t a l l i z a t i o n during preparation of the c e l l u l o s e specimen used for determination of c r y s t a l l i n i t y . R e c r y s t a l l i z a t i o n i s quite possible because the free ends of the broken chain on the surface of the c r y s t a l l i t e always tend to arrange themselves for r e c r y s t a l l i z a t i o n . Since there i s no possible way to show whether or not r e c r y s t a l -l i z a t i o n a c t u a l l y took place, probably both r e c r y s t a l l i z a t i o n and removal of amorphous materials are responsible for an increase i n c r y s t a l l i n i t y a f t e r decay. As the decay progresses, the enzymes w i l l gradually reach the c r y s t a l l i n e region which i s r e l a t i v e l y inaccessible to chemical reaction, and highly r e s i s t a n t to enzymatic hydrolysis. The rate of increase i n c r y s t a l l i n i t y w i l l slow down and f i n a l l y l e v e l o f f , as shown i n stage B, Figure 9. In other words, an increased degree of c r y s t a l l i n i t y w i l l give r i s e to greater resistance to enzymatic hydrolysis. This i s i n good agreement with r e s u l t s of other workers (68,106,149 ,150). 4. Relationship between l a t e r a l order and rate of  enzymatic attack The present r e s u l t shows that c r y s t a l l i n i t y of decayed-wood holocellulose depends la r g e l y on c r y s t a l l i n i t y of sound wood. This might be a t t r i b u t e d to the following two points: 78 (a) During the early stage of deeay, the enzymes attack the amorphous regions at almost the same rate for various types of wood. (b) The degree of perfection of the l a t t i c e structure i n the c r y s t a l l i n e regions i s heterogeneous rather than homogeneous. There must be a s t a t i s t i c a l d i s t r i b u t i o n of degree of l a t e r a l order. Two mechanisms have thus far been postulated i n order to explain the breakdown of ce l l u l o s e chains by enzymes. One i s a random cleavage mechanism and the other, an endwise attack mechanism (107)• Since the former i s thought to be much more probable (131) , i t i s assumed that the enzymes randomly attack c e l l u l o s e chains at the surface of the c r y s t a l l i t e . Thus both width and length of c r y s t a l l i t e w i l l decrease simultaneously as the decay advances. As shown i n part I I , the order of decreasing c r y s t a l l i n i t y of holocellulose from various types of wood i s tension wood, normal wood and compression wood. These differences i n c r y s t a l l i n i t y can be represented by the schematic lateral-order d i s t r i b u t i o n curve i l l u s t r a t e d by Howsmon and Sisson ( 1 1 0 ) . 1 1 Postulated curves obtained i n t h i s way are shown i n Figure 10A, page 8 l . The high c r y s t a l l i n i t y of tension wood i s characterized by a negatively skewed d i s t r i b u t i o n curve, whereas the low c f . page 13 79 c r y s t a l l i n i t y of compression wood i s characterized by a p o s i t i v e l y skewed d i s t r i b u t i o n curve. In order to correlate the sequence of enzymatic attack to the v a r i a t i o n of c r y s t a l l i n i t y , the l a t e r a l order d i s t r i b u t i o n curves are transformed to two-dimensional diagrams as shown i n Figure 10B. The l a t e r a l order i s assumed to be highest at the central portion of the c r y s t a l l i n e region, and to gradually decrease toward the surface of the c r y s t a l l i t e . Thus the highly c r y s t a l l i n e tension wood possesses a larger area of high l a t e r a l order at the center of the c r y s t a l l i t e , while the weakly c r y s t a l l i n e compression wood has a larger area of low l a t e r a l order at the surface of the c r y s t a l l i t e . No d e f i n i t e borderline a c t u a l l y exists between each phase of l a t e r a l order, so that the t r a n s i t i o n of l a t e r a l order should be regarded as continuous. As enzymatic hydrolysis begins, the outermost area of low l a t e r a l order, which corresponds to the amorphous region, w i l l be dissolved away quickly to leave the r e l a t i v e l y high l a t e r a l order portion (see Figure IOC). Consequently the degree of c r y s t a l l i n i t y of c e l l u l o s e increases r a p i d l y at t h i s stage, as shown i n Figure 9. Since the r e l a t i v e area of the high late r a l - o r d e r portion i s not changed through successive stages of decay, as shown i n Figure 10D, the order of degree of c r y s t a l l i n i t y can be expected to remain the same as i n the cont r o l . 8o When a l l r e a d i l y accessible c e l l u l o s e i s dissolved and decay advances from stage A to B, enzymatic attack s t i l l proceeds, but presumably at slow rate, and only at the surface of the c r y s t a l l i t e ( 1 5 0 ) . Hence the rate of increase i n c r y s t a l l i n i t y w i l l be n e g l i g i b l e at th i s stage, as demonstrated by the experimental r e s u l t s summarized i n (c) page 6 9 . As mentioned previously, c r y s t a l l i n i t y of compression wood holocellulose increased continuously throughout stage B. This can be explained by i t s abnormally low l a t e r a l order as i l l u s t r a t e d i n Figure 10B. At stage A, there i s s t i l l a considerable amount of r e l a t i v e l y low latera l - o r d e r material l e f t on the c r y s t a l l i t e surface of compression wood (see Figure IOC). The enzymatic attack continues to proceed at a fa s t rate, allowing the c r y s t a l l i n i t y to increase as shown i n Figure 10D, and Figure 9. 81 D FIGURE 10. SCHEMATIC L A T E R A L ORDER DISTRIBUTION CURVE AND S E Q U E N C E OF ENZYMATIC ATTACK ON THE CRYSTALLINE REGION A . SCHEMATIC L A T E R A L ORDER DISTRIBUTION CURVE dQ _ QUANTITY OF CELLULOSE BELONGING T O A dO PARTICULAR ORDER B. CROSS SECTION OF T H E CRYSTALLINE REGION O F T H E C O N T R O L C . DECAY S T A G E A (APPROX. 6 PERCENT WT. L O S S ) D. DECAY S T A G E B (APPROX. 15 P E R C E N T WT. L O S S ) L A T E R A L ORDER » M > > • > ffigjgjjg CONCLUSIONS 1. C r y s t a l l i n i t y of wood pulp and h o l o c e l l u l o s e of the normal western hemlock wood sampled increases s i g n i f i c a n t l y through successive growth r i n g s from the p i t h t o about 15 years, a f t e r which i t reaches a more or l e s s constant v a l u e . 2. C r y s t a l l i n i t y of wood pulp and h o l o c e l l u l o s e of summer-wood from the western hemlock sampled i s s i g n i f i c a n t l y higher than that of springwood. 3. C r y s t a l l i n i t y of wood pulp and h o l o c e l l u l o s e of the Douglas f i r compression wood specimens i s cons i d e r a b l y lower than that of normal wood, whereas c r y s t a l l i n i t y of wood pulp and h o l o c e l l u l o s e of the t e n s i o n wood samples of cottonwood i s s i g n i f i c a n t l y higher than that of normal wood. ' 4. The abnormal p h y s i c a l and chemical p r o p e r t i e s of r e a c t i o n wood - suggest that c r y s t a l l i n i t y i s not the only f a c t o r which a f f e c t s r e a c t i o n wood p r o p e r t i e s . There must be other f a c t o r s r e s p o n s i b l e f o r the p r o p e r t i e s of r e a c t i o n wood. 5. C r y s t a l l i n i t y of cottonwood and Douglas f i r wood h o l o c e l l u l o s e increases s i g n i f i c a n t l y during decay caused by the brown^rot f u n g i , P o r i a i n c r a s s a t a and P o r i a  monticola. 83 6 . The rate of increase i n c r y s t a l l i n i t y due to decay i s very rapid during the i n c i p i e n t stage of decay represented by 6 percent weight l o s s , but becomes very slow and shows almost a constant value of c r y s t a l l i n i t y thereafter. 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