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

Abstract

It was the purpose of this study to compare pulps prepared from normal, sound wood with those prepared from juvenile wood, compression wood, tension wood and decayed wood with regard to their apparent degree of crystallinity. The crystallinity index and crystallinity ratio of the pulps prepared from these woods were determined by two different X-ray methods. In method A, the principle of the Debye-Scherrer powder technique was applied and the crystallinity index of the pulp was evaluated from the 002 peak of the X-ray diffraction pattern. In method B a Geiger-counter X-ray spectrometer was used and the crystallinity ratio of holocellulose was evaluated from the (101 +101¯) combination peak. It was found that the apparent crystallinity of wood pulp and holocellulose prepared from normal western hemlock wood increased significantly through successive growth rings from the pith to about 15 years, after which it reached a more or less constant value. The crystallinity of wood pulp and holocellulose of summerwood was significantly higher than that of springwood. The crystallinity of wood pulp and holocellulose of compression wood from Douglas fir was considerably lower than that of normal wood, whereas the crystallinity of tension wood from cottonwood was significantly higher than that of normal wood. The crystallinity of cottonwood and Douglas fir holocellulose increased significantly during the incipient stage of decay. The rate of increase in crystallinity was very rapid during the incipient stage of decay represented by a six percent weight loss, but became very slow and showed an almost constant value thereafter. The relative value of crystallinity after decay depends mainly on the initial crystallinity rather than the history of decay.

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