Nature of the Swollen State as Determined from Tensile Properties After Cross-Linking

Abstract

Changes in internal fiber structure of cotton during swelling and tensioning were determined from the effects of these changes on physical properties imparted by cross-linking with dimethylolethyleneurea (DMEU). Cotton yarns were swollen with various agents and subjected to tension during swelling and subsequent washing. Dimethyl sulfoxide (DMSO), aqueous benzyltrimethylammonium hydroxide (BTOH), and solutions of KI and KCNS in NaOH were used as swelling agents. The effect on structure caused by repeated cycling between slack and original length during the base-swollen stage was judged from the effect of subsequent low-level cross-linking on physical properties. Resin pickup and distribution in the yarns were controlled by high-speed centrifugation.

The type and concentration of swelling agent are related to the form and degree of tension needed during the swelling steps to produce optimum properties after cross-linking. Improvement of physical properties after cross-linking was found to correlate with increased crystallite orientation over a part of the range studied. The relationship between degree of conversion of native cotton to Cellulose II and energy-to-rupture values is discussed. The characteristic features of low- level cross-linking previously observed in the fiber fragmentation patterns of yarns treated with DMEU, centrifuged to a low wet pickup, and cured, were also seen in the samples repeatedly swollen and restretched prior to DMEU treatment, centrifuging, and curing.

Keywords

Cotton cotton yarn DMEU. Chemically modified cotton. NaOH benzyltrimethylammonium hydroxide KI KCNS DMSO swelling agents polyethylene softener. Length load stretch temperature time concentration. Swelling orientation lattice conversion deswelling index of refraction tenacity break strength elongation energy- to-break diffractograms shrinkage. Physical testing fragmentation cycling.

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