X‐ray studies on the crystallinity of cellulose

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.

Caracterização química e estrutural de fibra de sisal da variedade Agave sisalana

“…Hu et al [40] realizando estudos com celulose proveniente de algodão observou que a reflexão no plano (002) corresponde aos planos de rede dos anéis glicosídicos, que são os mais densos na estrutura da celulose do tipo I. Segundo a literatura [41][42][43] a forma polimórfica da celulose que ocorre naturalmente é apenas a do tipo I. Também de acordo com Hu et al [40] , a intensidade do pico da reflexão 002 aumenta, e sua largura diminui com o desenvolvimento da fibra, indicando que ocorre um aumento no alinhamento dos anéis glicosídicos no plano (002) com o desenvolvimento da biosíntese do algodão, ocorrendo um aumento na porção cristalina da mesma.…”

X‐ray studies on cellophane1

“…3 The cellophane tubings contained 20y0 glycerin by weight, based on total dry weight of glycerin and cellulose. Significantly, the processing included simultaneous drying and stretching (linearly and transversely) of the plasticized gel tubing (neverdried glycerin and cellulose), "said stretching being within the range of 17% to 23% in the transverse direction and 2% to 8% in the longitudinal direction., 13 The chemical analysis of the sample has been reported earlier.2…”

Determinação dos índices de cristalinidade de fibras celulósicas

“…As técnicas de caracterização morfológica da fibra de algodão são bastante conhecidas no exterior (Hermans & Weidinger, 1949;Radhakrishnan, 1959;Egle Ir. & Grant, 1970;Patil, 1970;Peterlin & Ingram, 1970;Hindeleh & lohnson, 1971;Wakelin et ai., 1959).…”