What is the meaning of yarn twist
Yarn twist means that in order to make the yarn have certain strength, elasticity, elongation, luster, feel and other physical and mechanical properties, the cotton yarn must be changed by twisting, and the yarn twisting is realized by the fiber structure. In fact, the relative angular displacement between the cross sections of the cotton yarn is generated, so that the original straight and parallel fiber and the yarn axis are tilted to change the yarn structure. In the twisting process, the width of the thick strip shrinks gradually, and the two sides are gradually folded and drawn into the center of the yarn strip, forming a twisting triangle. In the twisting triangle, the width and section of the cotton strip change, from a flat ribbon to a cylindrical yarn.
What are the determination methods of yarn twist
1, untwist method: used for short fiber pure spinning, blended (ring spinning, spinning, wing spinning) strands thicker and twisted filament. Untwist to fiber parallel, counting the number of untwist revolutions per unit length of yarn.
2, untwist twist method: short fiber traditional spinning in the thinner yarn, with untwist and reverse twist to stretch the yarn and shrink back to the original length, with the added number of twists half of the yarn twist number. Recently, the methods of double untwisting, triple untwisting and quadruple untwisting have been developed. The purpose is to eliminate the change of structure of fiber filament when twisting in reverse. But it may also cause yarn structure changes and make the test results inaccurate.
3, reflective method: use a parallel beam to illuminate the yarn, measure the Angle of the reflected light peak deflection, accounting for twisting yarn surface helix Angle calculation twist.
For the twist of new yarns such as rotating cup spinning, electrostatic quiet, jet spinning, Cyro spinning, self-twist spinning, because of the different structure, especially the yarn core twist number is different or even different twist direction. Try to stratify separate tests and develop different test methods separately.
