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.

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An attempt has been made to develop a mathematical model to determine an economically optimal loom speed. The optimal loom speeds have theoretically been analyzed under the following three evaluating criteria ; (1) the maximum production rate criterion which makes the amount of fabrics to woven in a unit time to the maximum, or minimum time criterion which reduces the time to be required to weave a unit of area to a minimum, (2) the minimum cost criterion relating to weaving of a unit area of fabrics at the leasi cost, and (3) the maximum profit rate criterion which makes the profit gain in a given time to the maximum. The principle and algorithm have been derived to determine the optimal loom speed by using the data obtained in practical weaving mills.Then, a calculating try to get solutions proved successful in a computational simulation model.

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Fifteen kinds of fabrics were tactually and visually investigated by 388 subjects to identify constituent fibers of fabrics. A principal component analysis was made by using eight kinds of adjectives; cotton -, linnen -, silk -, wool -, metal -, glass -, china - and waxlike.The analysis has shown that four kinds of adjectives, i.e., cotton -, silk -, wool - like and non - fibrous material are enough to express the fabric character.Then, the image patterns of 15 kinds of fabrics were illustrated by using the above four adjectives. The fabrics were significantly characterized by the image patterns.

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