Abstract
In order to get an information on the change in fine structure of nylon 6 yarn during the practical false-twisting process, nylon 6 gut yarn was twisted, annealed and untwisted under the conditions simialr to the practical ones. The wide- and small-angle X-ray diffraction (WAXD and SAXD) methods together with electron microscopic -technique (EM) were used here. The degree of molecular orientation in the crystalline region of the twisted yarn decreases gradually with increasing twisting number (TN) in the region of TN >> 100. The long period of the crystalline, determined by SAXD of the twisted yarn increases with increasing TN. The observedvalue can not be interpreted in terms of the value of the long period of the untwisted yarn added with the change in the long period due to the elongation of the yarn in the twisting process. The elongation of the amorphous region during twisting was suggested by WAXD. Angle between the streak line observed by EM for twisted yarn surface and the fiber axis agrees very well with the twist angle of the yarn. The twisting effect on the yarn structure becomes less remarkable in the center region of the yarn axis. The lamallae are staggered normal to the streak line at the initial stage (i. e. at the low value of TN), but they begin to deviate from normal with their partial destruction as TN increases. From SAXD and density measurement, the internal strain of the yarn annealed after twisting is fully relaxed. When the yarn is untwisted after twisting and annealing, the orientaion of the crystalline region recovers gradually to thatof the untreated yarn. The normal line of the lamellae in the vicinity of center axis of these yarnbecome parallel to the fiber axis, but the lamellae in the outer region do not.
