Covered Spandex Yarn
Spandex covered yarn is made of spandex yarn as the core and An elastic yarn formed by wrapping the elongated spandex yarn in a spiral manner with filament or short fiber yarn.
01 Classification
“Spandex coating according to the number of coating layers Yarns can be divided into single-covered and double-covered yarns. The difference lies in the number of layers of outer covering silk (yarn) and the degree of wrapping.
Single-covered yarn It is to wrap a layer of outer silk (yarn) on the outer layer of core spandex. The number of turns is small, and the exposed core of the fabric is obvious, so 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 to cover the outer layer of spandex core yarn with two layers of filament or yarn. The two layers of covering are generally in opposite directions. The core spandex is well covered and exposed. It is lighter, and because the outer yarn symmetrically wraps the core yarn with opposite helix angles, the elasticity of the outer yarn is well balanced, and the subsequent processing can generally be carried out without shaping treatment. However, the processing cost of double covering yarn is relatively high. High. Mainly used for elastic fabrics such as leggings, elastic bands, sock openings, and stockings.
“Depending on the device It can be divided into two types: mechanical covered yarn and air covered yarn.
Mechanical covered yarn (abbreviated as machine package, English abbreviation as SCY) is a continuous rotation and winding of the outer fiber filament on the core spandex that is drawn at a uniform speed. The fabric has a twist (TPM in English abbreviation) after being twisted, and its main feature is a smooth and crisp fabric style.
Air-coated yarn (abbreviated as air-coated yarn, abbreviated as ACY in English) is to draw the outer fiber filament and spandex yarn through a certain type of nozzle at the same time, and through the high compressed air pattern The consistent spray pressure forms a rhythmic network of yarn points. Its fabric feels soft and smooth.
Empty bale and machine bale yarns have their own advantages and disadvantages when weaved in downstream weaving mills. Empty bales generally need to be sized when being warped on an air-jet loom, otherwise the fabric is prone to fluffing and broken wires, etc. However, it can be used directly after beating up. Considering the 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 facilitates the reduction of costs for downstream weaving mills. Although machine bags do not expose the core yarn, generally apart from uneven twist, they are not prone to quality problems during spinning and weaving. However, the output is low, and the price is therefore higher than that of empty bags of the same specification by more than RMB5000/T. The fine denier covered yarn is The price is even higher than RMB10,000/T for empty packages of the same specifications, thus greatly increasing the cost of using machine packages.
02 Main process
During the spinning process, the pre-drafting ratio of spandex (Spandex Stretch) is an important process parameter, which affects the elasticity of covered yarn (Covered Yarn) and fabric, and also affects the strength and elongation, evenness and creep performance of covered yarn. The pre-draft multiple of spandex is too small, which cannot give full play to the advantages of elasticity of elastic fabrics. When the draft is too high, it is difficult to spin, and it is easy to cause wire breakage, and the product quality will decrease; in addition, the percentage of spandex fiber also affects The elasticity of the covered yarn is high, and the elasticity is good. The strength and stretch of the air-coated yarn increases with the increase of the spandex pre-drafting multiple. After the spandex is stretched to a certain value, the retractability of the spandex yarn causes the outer fiber to be in a curled state; appropriately increase the pre-drafting multiple, and the spandex will The percentage content decreases and the outer fiber curl degree is large. However, when the draft is too large and the deformation amplitude of the spandex yarn approaches the critical value of deformation, the strength and elongation of the covered yarn will decrease, but it will help the evenness of the covered yarn.
The phenomenon of deformation changing with time under the action of constant drafting force is called creep. Conventional covered yarn has the best creep resistance when the spandex yarn is pre-drafted 3.5 times. Specifically, it should be adjusted appropriately according to the purpose and the style of the downstream fabric.
In addition to the requirements for spandex draft ratio in air-coated yarns, mechanically covered yarns also have an important process parameter which is twist. , twist affects yarn quality, elongation and evenness. Increasing the twist can increase the cohesion between the covering fiber and the spandex yarn, thereby increasing the strength of the covering yarn. If the twist is too low, the outer fibers will be loose, which will affect the coating effect and lead to core exposure. Therefore, the twist should be higher during mechanical coating. But if the twist is too high, the fabric will feel hard and have poor drape. Generally, the twist needs to be adjusted accordingly as the denier of the yarn changes and the style requirements of the fabric are different. The elongation of the machine bag is also mainly determined by the performance of the spandex core yarn. If the twist is too large, the outer fiber coating is too tight, and the spandex On the contrary, the elastic effect of the silk cannot be fully exerted, causing the elongation to decrease.
03 Specifications and uses
Spandex covered yarn is mainly used for fabrics that require high elasticity. Partially for woven fabrics. Fabrics woven with covered yarn are thicker and are especially suitable for weaving sports tights, such as swimming suits, ski suits, etc.
The difference between core-spun yarn and covered yarn
✪The difference between the two, we use spandex Core-spun yarn and spandex covered yarn are examples. Spandex core-spun yarn is spandex wrapped with short fibers. It uses spandex yarn as the core and is wrapped with non-elastic short fibers. The core yarn is generally not exposed when stretched. Spandex covered yarn is an elastic yarn formed by wrapping spandex with chemical fiber filaments. It also uses spandex yarn as the core and non-elastic short fibers or filaments to cover the elongated spandex yarn in a spiral manner. There is core exposure in the tensioned state.
✪The production equipment is different. Core-spun yarn is a short fiber made on a spinning machine, covered yarn is made on a splicing + double-twisting machine, and long-fiber covered yarn is made on a long-fiber double-twisting machine.
✪The core yarn of core-spun yarn is wrapped by fibers. If their core yarn is well wrapped, you cannot see the core yarn. The technological route of staple fiber covered yarn is as follows: one or more yarns are first spliced, and then the spliced yarn bobbin is put on a two-for-one twisting machine to twist and wind the resulting yarn. All the yarns put together by this covering yarn, namely the core yarn and the outer covering yarn, are visible.
✪Core-spun yarn is usually made on a spinning frame. When drafting the roving, the textile raw materials that need to be wrapped in it are added. Such as cotton wrapped in spandex; polyester, viscose wrapped in spandex; cotton wrapped in polyester filament; polyester wrapped in polyester filament, etc. The covered yarn actually uses a twisting machine, one yarn is used as the core yarn, and the other yarn is wrapped around the outside. For example, spandex is used as the core yarn and is wrapped with polyester, nylon, etc. </p
