Torsional Testing Apparatus and its Application to Experimental Investigation on the Relation between Torsional Properties of Yarns and Fibers

A new torsional testing apparatus has been developed to measure the torsional property of single fibers and yarns with high accuracy and easy operation . The torsional properties of spun, textured and filament yarns were measured under different yarn tension by this new apparatus, and the torsional property of single fibers . which were sampled from the yarns were also measured in order to investigate the interrelation between the properties of yarns and fibers. The torque is measured by detecting the twisted angle of a thin steel wire connected with a spe cimen by means of a linear differential transformer. When each of the fibers which compose a yarn is twisted without any interaction between fibers, the torsional rigidity of the yarn must be equal to the sum of the rigidity ofeach of the fibers. Here, a is defined as : The a values for some of actual yarns were examined and observed that a depends on yarn tension and yarn structure, and represented by the experimental formula : where, ao, a1, a2 are constants and Wt is (yarn tension)/(tex) . The results show that although the values of as for polyester and nylon multifilament yarns are almost unity, those of polyester spun yarns and textured yarns are value of 3 or more. On the other hand, ao of a worsted yarn, even though it is a spun yarn, is also unity. Thus a is significantly related to fiber property as well as to yarn structure . Hysteresis in torsional property of these yarns are also examined and discussed in relation to the value of a, (Received July 10, 1976)