Twisting is one of the purposes of spinning, and the amount of twisting is an important indicator to measure the performance of the yarn, which is generally expressed by twist. Twist refers to the number of twists per unit length of the yarn (ie, the number of helical turns). The unit length varies with the type of yarn, and its measurement unit can be expressed as "twist/10cm" or "twist/m", the former is used for cotton and cotton-type chemical fiber yarn, the latter is used for worsted wool yarn and Twist measurement of synthetic filament yarns. Twist affects the strength, rigidity, flexibility, elasticity, shrinkage and other indicators of the yarn. As the twist of the yarn increases, its strength increases, but the twist cannot exceed a certain value, otherwise its strength will decrease. This certain value is called the critical twist of the yarn. The critical twist of yarns with different raw materials is different. The softness, elasticity and shrinkage of the yarn are also closely related to the twist. In general, under the premise of meeting the strength requirements, the smaller the twist of the yarn, the better, because the increase of the twist will make the yarn feel harder, the elasticity will decrease, and the shrinkage rate will increase. Or less twist's sake. In addition, twist has an effect on the bulk weight and diameter of the yarn, and the twisting effect increases the tightness of the yarn. Within a certain range, the volume weight of the yarn increases with the increase of the twist, and the diameter of the yarn decreases with the increase of the twist, so that the coverage and comfort of the fabric change.
In short, the yarn twist should be selected according to different fabric applications. If the warp yarn needs to have higher strength, the twist should be larger; the weft and knitting yarns should be soft and the twist should be smaller; the yarn for woven and knitted fleece fabrics should have a smaller twist to facilitate raising; Crepe fabrics are required to be smooth, stiff and cool, and the twist of the yarn should be larger.
