Distinguishing Between Two Cottons That Differ Only in Fiber Micronaire. Part 1. By Yarn Tensile Tenacity.

L.B. De Luca, D.P. Thibodeaux and Y. El-Mogahzy


 
ABSTRACT

A series of five yarns at each of five twist factors was spun on a ring frame using two different cottons. Yarn tensile data, obtained from the Uster Dynamat II, Scott skein, and Uster Tensorapid testers (in the order of increasing rate of extension) compared by a method that determines yarn tenacity per fiber, yarn tenacity per broken fiber, and number of broken fibers in each yarn. For the high-micronaire cotton, the number of broken fibers increased with rate of extension for all yarn sizes and twist factors. For the low-micronaire cotton, the same is true, however, the number of fibers broken in the Tensorapid test for (a) the coarsest yarn was least and (b) the second size yarn was intermediate between the Dynamat II and skein tests. Linear relationships were found between total fibers and broken fibers for each set of data. These results show that the low-micronaire cotton, when tested at a high rate of extension, binds during extension and fewer fibers are broken. The relationship between Yarn Twist and the square root of yarn tenacity per fiber (or per broken fiber) at constant twist factor is linear for each testing machine. As twist factor changes, the linear regression lines converge at a point near zero twist and zero normalized yarn tenacity that represents infinite yarn size and is the means by which the number of broken fibers in the yarns were determined. The way in which the different twist factor regression lines [yarn twist-vs-(yarn tenacity/broken fiber)(1/2) curves] converge for each cotton and testing machine shows the effect of fiber binding during extension when the low micronaire cotton is tested in the Tensorapid machine at a high rate of extension.



Reprinted from 1992 Proceedings Beltwide Cotton Conferences pg. 1468
©National Cotton Council, Memphis TN

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Document last modified Sunday, Dec 6 1998