Orientation-Disorientation Effects in Tensioned, Mercerized Cotton. The Pretreatment of Yarns for Wash-Wear Fabrics of High Strength and Durability

Abstract

Slack mercerization of cotton, with restretching to various degrees in the mercerizing alkali, was compared to merceriza tion at constant, preselected lengths as a method of yarn pretreatment. Fabrics were woven of these pretreated 2-ply yams and were crosslinked with DMEU to a wrinkle recovery of 270°-286° (W + F). In certain cases little or no loss of strength occurred during DP finishing, and the yarn-mercerized fabrics possessed greater strength after crosslinking than ordinary fabric not crosslinked at all. Moreover, after 20 launderings several of the experimental wash-wear fabrics equalled in strength the unmercerized, uncrosslinked, unlaundered fabrics prepared as controls. X-ray orientation, yarn strength, and elongation, as well as the degree of stretching during yarn pretreatment, were correlated with yarn and fabric strength after crosslinking and after fabric laundering. In yarn slack-mercerized and restretched to 91% of normal length, both the strength and the elongation after crosslinking equalled the values for unmercerized yarn before cross linking. The same effect occurred in fabrics woven from these yarns. Evidence is presented that domains of swelled and shrunken cellulose remain in mercerized cotton fibers even after tension has been applied to orient the crystallites and straighten the fibrillar spirals of the alkali-wet cotton. The most effective yarn pretreatment, for increased strength retention after DMEU crosslinking, was slack mercerization followed by restretching to 103% of normal length. In fabrics woven of these yarns, covalent crosslinking by DMEU actually increased the durability, as measured by strength retained during multiple launderings. Yarn commercially mercerized to 102% of normal length also was highly suitable. The increased yarn length obtained in this kind of pretreatment could largely offset the cost of yarn mercerization, leaving the cost of yarn plying as the principal item of expense.