Covered spandex yarn classification
According to the number of covering layers, covered spandex yarn can be divided into single covering and double covering. The difference lies in the number of layers of outer covering yarn (yarn) and the degree of wrapping.
Single-covered yarn is a layer of outer-coated yarn (yarn) wrapped on the outer layer of spandex with core yarn. The number of turns is small, and the exposed core of the fabric is more obvious. It is not suitable for dark-colored products. It is mainly used for elastic fabrics such as socks and weft-knitted underwear.
Double-covered yarn is coated with two layers of filaments or yarns on the outer layer of spandex core yarn, and the two layers of coating are generally in opposite directions. The core silk spandex is well covered, and the exposed phenomenon is relatively light, and because the outer covering silk wraps the core silk symmetrically with opposite helical angles, the elastic balance of the covering silk is good, and the subsequent process can be carried out without setting treatment. Processing, but the processing cost of double covered yarn is higher. It is mainly used for elastic fabrics such as leggings, elastic bands, sock openings, pantyhose and so on.
According to different equipment, it can be divided into two types: mechanical covering yarn and air covering yarn.
Mechanically covered yarn (referred to as machine package, English abbreviation is SCY) is a yarn that continuously rotates the outer fiber filament and winds it on the core yarn spandex that is drawn at a constant speed, and is twisted to have a twist (English abbreviation is TPM). , The flat and crisp fabric style is its main feature.
Air-covered yarn (abbreviated as empty package, English abbreviation as ACY) is a yarn that draws outer fiber filaments and spandex yarns through a certain type of nozzle at the same time, and forms rhythmic network points through regular spray pressure of high-compression air. . Its fabric is soft and smooth to the touch.
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 more than RMB10000/T of the empty package of the same specification, which greatly increases the cost of using the package.
The main process of covered spandex yarn
In the spinning process, the pre-draw ratio of spandex (Spandex Stretch) is an important process parameter, which affects the elasticity of the covered yarn (Covered Yarn) and the fabric, and 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. 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 spandex draft ratio in air-covered yarns, mechanically covered yarns also have an important process parameter twist, which affects yarn quality, elongation and evenness. 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 style requirements of the fabric. The elongation of the machine bag is also mainly determined by the performance of the spandex core filament. On the contrary, the elastic effect of the silk cannot be fully exerted, which reduces the elongation.
Specifications and uses of covered spandex yarn
Covered spandex yarn is mainly used for fabrics that require high elasticity, and some are used for woven fabrics. The fabric woven with covered yarn is thicker, especially suitable for weaving sports tights, such as swimming suits, ski suits, etc.
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