The Effect of Fiber-Bundle Elongation of Medium Staple Cottons on Processing Performance and Y arn Properties

Abstract

Cottons differing in fiber-bundle elongation (5.8%, 7.3%, and 10.1%) were processed into 30/1 (20 tex) and 40/1 (15 tex) yarns at two levels of twist (3.75 T. M. and 4.50 T.M.) and of spinning draft (27.5 and 40.0). Fiber elongation had no effect on nep potential or uniformity of slivers. No relation was found between fiber-bundle elonga tion, 2.5% span length and fiber strength measured at " gage length, and only a general inverse trend was found with Micronaire reading. The reduction in fiber hooks when the cottons differing in elongation were processed from card sliver into second drawing sliver was significantly lower for the high- than for the low-elongation cotton. The higher-elongation cotton spun with fewer ends down than the lower-elongation cotton with this effect being more,pronounced at higher drafts and spindle speeds, lower twists, and as the yarn became finer. Generally, an increase in fiber elongation from 6% to 10% made possible a spindle speed increase of about 1000 rpm for the high twist 30/1 and 40/1 yarns at constant end breakage rate. In practical terms, it appears that the overall effect of fiber elongation (low to high) was approximately twice that of draft and about two-thirds that of twist and yarn number. It was possible to use higher spindle speeds without increasing end breakage with a tougher fiber and with a fiber of lower average tensile stiffness. Fiber average tensile stiffness and toughness were linearly and directly correlated with their yarn counterparts. Single-strand yarn strength and yarn elongation were linearly related to fiber elongation, with increased fiber elonga tion resulting in increased yarn strength and elongation.