What is spandex covered yarn, Air covered spandex yarn, Covered elastic yarn?
Spandex covered yarn is an elastic yarn formed by covering the elongated spandex yarn with the spandex yarn as the core, and wrapping the elongated spandex yarn with the filament or short fiber yarn in a spiral manner.
Classification of spandex covered yarn
1. According to the number of covering layers, it can be divided into single covering yarn and double covering yarn. Among them, nylon ammonia and polyester ammonia are mostly covered in a single covering method.
2. According to different equipment, it can be divided into two types: mechanical covering yarn and air covering yarn.
The characteristics of spandex covered yarn
1. Air-covered yarn (abbreviated as empty package, English abbreviation as acy) is the outsourcing fiber filament and spandex yarn drafted through a certain type of nozzle at the same time, and the rhythmic network points are formed by the regular spray pressure of high-compression air. yarn. The fabric feels soft and smooth;
2. Mechanically covered yarn (abbreviated as machine package, English abbreviation is scy) is to continuously rotate the outer fiber filament and wind it on the core silk spandex that is drawn at a constant speed, and it has twist after twisting (English abbreviation is tpm) ), the flat and crisp fabric style is its main feature.
Empty bales and machine baled yarns have their own advantages and disadvantages in weaving in downstream weaving mills. When the empty bale is warped on the air-jet loom, sizing is generally required, otherwise the fabric is easy to fluff and break, but it can be used directly after beating up. From the perspective of cost alone, the production capacity of empty bales is much higher than that of machine bales, making the price lower than that of machine bales, which is convenient for reducing the cost of downstream weaving mills.
Although the machine bag does not expose the core yarn, except for the uneven twist, it is not easy to produce quality problems during spinning and weaving, but the output is low, so the price is more than RMB5000/t higher than the empty bag of the same specification. The price is even higher than RMB10000/t of empty bales of the same specification, which greatly increases the cost of using machine bales.
In the spinning process, the spandex stretch is an important process parameter, which affects the elasticity of the covered yarn and the fabric, and also affects the strength and elongation of the covered yarn, evenness Uniformity and creep properties. If the pre-draw ratio of spandex is too small, it cannot give full play to the advantages of the good elasticity of elastic fabrics. When the draft is too high, spinning is difficult, and it is easy to cause broken filaments, resulting in a decline in product quality; in addition, the percentage of spandex yarn also affects Elasticity of covered yarn, high content, good elasticity. In the case of a certain specification of spandex yarn, increasing the draft ratio will reduce the percentage of spandex yarn, that is, the pre-drawing ratio of spandex is inversely proportional to the percentage of spandex yarn.
The strength and elongation of the air-covered yarn increases with the increase of the spandex pre-drawing ratio. After the stretching reaches a certain value, the retractability of the spandex yarn makes the outer fiber curl; if the pre-drawing ratio is increased appropriately, the spandex The percentage content is reduced, and the degree of curling of the outsourcing fiber is large. However, when the draft is too large, the deformation of the spandex yarn is close to the critical value of deformation, which will reduce the strength and elongation of the covered yarn, but it is conducive to the evenness of the covered yarn.
The phenomenon that the deformation changes with time under the action of constant drawing force is called creep. The creep resistance of the conventional covered yarn is the best when the spandex yarn is pre-drawn 3.5 times. Specifically, it should be adjusted according to the purpose and the style of its downstream fabrics.
In addition to the requirements for the draft ratio of spandex in air-covered yarns for mechanically covered yarns, another important process parameter is the twist, which affects the quality, elongation and evenness of the yarn. Increasing the twist can increase the cohesion between the outer fiber and the spandex yarn, so that the strength of the covered yarn can be improved. If the twist is too low, the outer fibers will be loose, which will affect the coating effect and cause the core to appear. Therefore, the twist should be higher during mechanical coating. But the twist is too high, the fabric feels hard and the drapability is poor.
Generally, the twist should be adjusted according to the change of the denier of the yarn and the different style requirements of the fabric. For example, the twist of n40d+20d machine bag should be around 600 twists, while the twist of n70d+40d or t150d+40d machine bag should be controlled at 480 Left and right are fine. The elongation of the machine bag is also mainly determined by the performance of the spandex core yarn. If the twist is too large and the outer layer of fibers is too tightly wrapped, the elastic effect of the spandex yarn cannot be fully exerted, resulting in a decrease in elongation.
Evenness of evenness improves with increasing twist. If the twist is too small, the outer fiber is loose. During the spinning process, due to friction and other reasons, the fiber will move slightly along the yarn axis, so the evenness will deteriorate.
Mainly used in: weaving, elastic denim, webbing, socks, underwear, lace and sporting goods, etc.