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DOI: 10.1177/004051755902900409 Part II: Effects of Strains During Swelling, Washing, and Drying
Yarns from samples of Pima S-1 and Hopi Acala varieties were merceriud and decrystallized when strain was controlled to provide unrestricted shrinkage in length, normal length, and 3% extension beyond normal length during ethylamine treatment. Comparisons of effects of sodium hydroxide and ethylamine at different strain conditions were made from measurements on the cellulose, tensile properties of fiber bundles and yarns, and elastic behavior of the yarns. Densities of the mercerized are in general below those of the decrystallized if occluded solvents are removed. The lower densities are in accord with the higher moisture regains for mercerized than decrystallized cottons. Strains had no influence on the crystallinity ratio during decrystallization but pre vented complete conversion to cellulose type II in mercerization. The decreases in bundle tenacities with increases in gauge length were essentially equal in the decrys tallized and untreated cottons but smaller in the mercerized. Yarn tenacities of the mercerized and untreated increased as the moisture regain was increased, white those of the decrystallized were essentially equal at standard and wet conditions. Elongation at break was decreased by strain during treatment and increased with moisture in the sample when tested. The slack mercerized or decrystallized yarns when strained to less than 2% of their elongation at break have greater recovery and less permanent set than the untreated. At high strains or stresses the reverse in recovery and permanent set was found. Yarns treated at normal length have no appreciable difference in re covery and permanent set from that of the untreated.
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