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Mercerization of cellulose. III. Changes in crystallite sizes
Author(s) -
Nishimura Hisao,
Sarko Anatole
Publication year - 1987
Publication title -
journal of applied polymer science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.575
H-Index - 166
eISSN - 1097-4628
pISSN - 0021-8995
DOI - 10.1002/app.1987.070330314
Subject(s) - cellulose , crystallite , amorphous solid , materials science , crystal (programming language) , chemical engineering , crystal structure , crystallography , polymer chemistry , chemistry , organic chemistry , computer science , programming language , engineering
When cellulose is mercerized slowly, the initial conversion is from the cellulose I crystal structure to that of Na–cellulose I. The conversion is a crystal‐to‐crystal phase transformation, without passage through an amorphous state. The analysis of crystallite sizes of cellulose I and Na‐cellulose I during this transformation has shown that the process takes place in two steps. The first is a rapid step, occurring in approximately 1/7 (or less) of the total conversion time, resulting in a conversion ratio of ca. 65%. The measured crystallite sizes of both cellulose I and Na–cellulose I remain constant during this stage, at ∼ 62 and ∼ 35 Å, respectively. In the following slow step, complete conversion to Na–cellulose I takes place, and the crystallite size of cellulose I decreases steadily until disappearance. The crystallite size of Na–cellulose I increases steadily at the same time, to a final value of ∼ 50 Å. Simultaneously, the unit cell parameters of cellulose I change significantly. The observation of a two‐step conversion is consistent with a proposed mercerization mechanism in which the conversion is assumed to begin in the amorphous phase of the cellulose fiber.