Influence of Yarn Twist Technology on Yarn Strength and Quality

The process adjustment of yarn twist not only affects the breaking strength of single yarn and the elongation at break of single yarn, but also affects the yarn linear density, evenness, thick places, details, neps, hairiness and other items. The twisting degree of the yarn changes with different degrees; in the daily twist process adjustment, it is necessary to pay attention not only to the twist change, but also to the related changes in the overall quality of the yarn due to the twist process adjustment. Twist is a parameter to measure the degree of twisting of the yarn, and it is the basic condition for the yarn to be formed and wound, and to give the yarn strength. Usually, in the adjustment of yarn twist process, the influence of twist change on single yarn breaking strength and single yarn breaking elongation is often only concerned, while the effect of twist change on yarn linear density, evenness CV%, The causal relationship of thick places, details, neps, hairiness and other items; ignore the influence of yarn twist change on other quality changes of yarn, fail to take comprehensive quality control measures, thus causing customers to be dissatisfied with yarn quality, with undue loss of trade. In this paper, a group of samples are selected according to the conventional varieties of textile enterprises, and different levels of twist are set for the same sample, and each sample is sampled for various tests, so as to compare and analyze the influence of twist changes on the overall quality of the yarn. Yarn twist comparison test at different levels 1. Sample selection C14.6texT, CJ14.6texT, C14.6texK, T35/C35 13.1texT, T80/C20 13.1texT, C27.8texT. Within the normal twist range of each variety, in order to compare the quality changes brought about by different yarn twists, the twist of each variety was set to three levels of high, medium and low, and samples were taken separately. In order to enhance the comparison of the inspection and reduce the influence of accidental factors on the inspection and comparison, ten bobbins are taken from each group of samples at different levels; 30 bobbins are taken from each variety. CV% value, thick places, details, and nubs are tested by: GB/T3292.1-2008, evenness tester; Hairiness test by: FZ/T01086-2000, YG172A yarn hairiness tester; Single yarn breakage Strength test adopts: GB/T3916-1997, YG063T automatic single yarn strength tester; Linear density test adopts: GB/T4743-2009, Y802A eight blue oven, EL-200S precision electronic balance; Twist test adopts: GB/T2543. 2-2001, YG156 Automatic Twist Tester. 3. Temperature and humidity Temperature: 20±1.0℃ Humidity: 65±2%RH 4. Inspection times In order to reduce the influence of the discreteness of different fragments of each group of samples on the inspection results, the inspection results of each sample were compared and analyzed by the average value. The number of inspections at different levels of each sample is (see Table 1): the linear density is 100m per tube, and a total of ten times; the twist is 2 times per tube, and a total of 20 times; the breaking strength of single yarn is 2 times per tube, and a total of 20 times; The evenness test is done at 400m/min, 1min per tube, a total of ten times; the length of the hairiness test segment is 30m, the test speed is 30m/min, 1 minute per tube, 10 times, this test only counts 1mm, 3mm, 5mm, 7mm hairiness index. 5. Test results The test results are shown in Table 1. Changes in the quality of yarns with different twists. Analysis From Table 1, it can be seen that the linear density of the yarn, single yarn breaking strength, evenness, and hairiness vary with the twist of the yarn. As far as the twist change is concerned, the overall quality of the yarn is uncertain. Although the magnitude and trend of the change in different twists and varieties are not the same, the change of the yarn quality due to the twist can be determined. 1. Twist and yarn strength After the whisker is twisted, the fibers are in close contact and not easy to slip off. Generally, within a reasonable twist coefficient range of the yarn, the breaking strength of single yarn increases with the increase of twist. This is because with the increase of twist, the frictional resistance between fibers increases, which increases the strength of the whiskers during the breaking process, so the breaking strength of single yarn will gradually increase within a certain twist range. After the single yarn breaking strength reaches the maximum value (the corresponding twist is called the critical twist) and then twists again, the fiber twist angle also increases, so that the effective component force that the fiber itself can withstand in the axial direction of the whisker is reduced. In addition, the excessive twist will increase the uneven distribution of the fiber stress in the inner and outer layers of the whisker, aggravate the asynchrony of fiber breakage, and reduce the strength of the fiber itself, so that the breaking strength of the single yarn after the critical twist shows a downward trend (the critical value of different types of yarns. The twist is different). T65/C35 13.1tex T single yarn breaking strength changes with twist coefficient.

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