Abstract:

In in-phase self-twist yarn there exists an obviously weak twist area between the twisted  and no twisted zones. Therefore, during the self-twist spinning process, different distances from the two strands to the convergence point is adopted to produce a certain phase difference to improve the yarn strength. There are two methods used for calculating the twist distribution function of self-twist yarn: 1. using the difference in distance c, and 2. using the twist distribution function of strands A and B, respectively. Then the average twist over a half cycle length is calculated by the twist distribution functions from the two methods mentioned above. Comparing the calculation value from the two methods with actual test twists for the half cycle length, the result shows that the calculation value from method 2 is closer to the values measured, namely the twist distribution function derived from that of strands A and B, respectively. The twist unevenness of self-twist yarn is calculated by the twist distribution function from  method 2. The twist unevenness of yarn 1 is the highest. That of yarns 2 and 3 decreases in turn. From the test data of 49×2 tex and 113×2 tex selftwist yarns, in-phase self-twist yarn 1, with maximum twist unevenness, has the minimum tenacity and  maximum unevenness of tenacity, and in the same way phased self-twist yarn 3, with the minimum twist unevenness, has the maximum tenacity and  minimum unevenness of tenacity.