Fine structure and tensile properties of decrystallized products prepared from cotton

摘要

AbstractA highly decrystallized product was prepared from cotton by treating it with ethylamine, extracting the ethylamine with pyridine, and then partially acetylating the sample in this solvent. The properties of this material were compared with those of cotton, partially acetylated cotton, cotton partially acetylated after treatment with ethylamine and water, and mercerized cotton. It was confirmed that the reactivity toward acetylation of ethylamine‐treated, pyridine‐extracted cotton (in the never‐dried state) was higher than that of the ethylamine‐treated, water‐extracted sample. However, the acetylation of both these materials and also of cotton can be represented by an equation developed for diffusion‐controlled reactions. Acetylation was necessary to retain the highly decrystallized state of never‐dried ethylamine‐treated cotton that had been pyridine‐extracted. It was deduced from hygroscopicity measurements that the fraction of amorphous cellulose in this never‐dried material was 0.71. The values for dried ethylamine‐treated cotton and mercerized cotton were 0.51 and 0.57, respectively, Comparison of the x‐ray diffractograms of cotton and of acetylated ethylamine‐treated, pyridine‐washed cottons (acetyl contents 8.5–10.6) showed that the base of the (002) plane diffraction peak of the treated materials was broader and that maxima corresponding to the (101), (101) crystalline reflections were no longer present. A comparison of electron micrographs of these materials indicated that the microfibrils in the secondary wall of the decrystallized fibers remained closely parallel though slightly crimped. In mercerized cotton, on the other hand, the microfibrils were swollen and crimped and there was considerable disorientation. Mercerization treatment and ethylamine treatment which was followed by pyridine extraction and partial acetylation increased the strength of cotton by similar amounts. The former treatment also produced a marked increase in the elongation at break of the fibers while the latter did not p