X‐ray studies on the crystallinity of cellulose

TLDR

The study reviews a previously described X‑ray method for determining cellulose crystallinity, presenting new data ranging from 8 % to 70 %. Crystallinity was quantified using X‑ray intensity measurements, and dry‑ground rayon powders were recrystallized in water to validate the approach. Cotton, flax, ramie, and most rayons exhibit ~70 % crystallinity, cellulose acetates and bacterial cellulose ~40 %, wood pulp and Valonia ~65‑70 %, and Du Pont Fiber G shows 53 %; dry‑ground rayon powders (~10 % crystalline) recrystallize to match rayon, and heat‑of‑wetting differences corroborate these findings.

Abstract

Abstract The method for the evaluation of the percentage crystallinity in cellulose preparations from x‐ray intensity measurements, previously described in detail (J. Appl. Phys., in press) is reviewed briefly and new material presented consisting of crystallinity percentages between 8% and 70%. Cotton, flax, and ramie possess equal crystallinity (70%) and so do the majority of rayons, independent of their degree of orientation and including cuprammonium and Lilienfeld rayons. Cellulose acetates saponified under varying conditions also yield almost the same value as rayon (40%). The New product Fiber G (du Pont) holds an exceptional position with 53% crystalline substance. In the series of native celluloses, wood pulp has about 65%, Valonia 65–70%, and bacterial cellulose about 40%. By dry grinding of rayon, a powder was obtained containing only slightly less than 10% crystalline substance, which on recrystallization in water, yields 2 product having the same crystallinity as rayon. The difference between the heats of wetting of the criginal and the recrystallized powder affords additional support of the results obtained.