Covered Spandex Yarn
Spandex covered yarn is It is an elastic yarn formed by using spandex yarn as the core and covering the elongated spandex yarn with filament or short fiber yarn in a spiral manner.
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Category
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According to the number of coating layers, spandex covered yarn can be divided into single coating and double coating. The difference It lies in the difference in the number of layers of outer covering silk (yarn) and the degree of wrapping.
Single covered yarn is a layer of outer covering silk (yarn) wrapped around the core spandex. Yarn), 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 covering yarn
It is to cover the outer layer of spandex core yarn with two layers of filament or yarn. The two layers of coating are generally in opposite directions. The core yarn spandex is well covered and the exposure phenomenon is light. Since the outer yarn is symmetrically wrapped around the core yarn at opposite helix angles, the elasticity of the wrapping yarn is well balanced. Generally, subsequent processes can be carried out without shaping treatment. Processing, but the processing cost of double-covered yarn is higher. Mainly used for elastic fabrics such as leggings, elastic bands, sock openings, and stockings.
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According to different equipment, it can be divided into mechanical coating There are two types of yarns and air-covered yarns.
Mechanical covered yarn (abbreviated as machine package, English abbreviation as SCY) is to continuously rotate and wrap the outer fiber filaments around the quilt. The core yarn spandex that is drawn at a constant speed is twisted and has a twist (TPM in English abbreviation), and its main feature is a smooth and crisp fabric style.
Air coating Yarn (referred to as empty bale, English abbreviation ACY) is a yarn in which the outer fiber filament and the spandex yarn are simultaneously drawn through a certain type of nozzle, and are regularly sprayed with high-compressed air to form a rhythmic network of points. Its fabric Soft and smooth to the touch.
Empty bales and machine-bundled yarns have their own advantages and disadvantages when weaved in downstream weaving factories. Empty bales When warping on an air-jet loom, sizing is generally required, otherwise the fabric is prone to fluffing and breakage, but beat-up can be used directly. Considering the cost alone, the empty bale production capacity is much higher than the machine bale production, making the price lower than the machine bale, which is convenient Reduce the cost of downstream weaving mills. Although the core yarn is not exposed in the machine bag, it is generally not prone to quality problems during spinning and weaving except for uneven twist. However, the output is low, and the price is therefore higher than the empty bale of the same specification by more than RMB5000/T. , the price of fine denier covered yarn is even higher than that of empty bales of the same specification, more than RMB10,000/T, thus greatly increasing the cost of using machine bales.
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Main process
In the spinning process, the pre-draft ratio of spandex (Spandex Stretch) is an important process parameter. It affects the elasticity of the covered yarn (Covered Yarn) and the fabric, and also affects the strength and elongation, evenness and creep properties of the covered yarn. The pre-draft multiple of spandex is too small and cannot give full play to the good elasticity of the elastic fabric. The advantage is that 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 content of spandex fiber also affects the elasticity of the covered yarn, and the higher the content, the better the elasticity. 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 Change. 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 spandex draft ratio requirements for mechanically covered yarns, there is another important process parameter: 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 fiber 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.
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Specifications and uses
Spandex covered yarn is mainly used for fabrics that require high elasticity, and is partially used 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
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The difference between the two is as follows: spandex core-spun yarn and spandex covered yarn. 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, with spandex as the core, and non-elastic short fibers or filaments covering the elongated spandex in a spiral manner. There is core exposure in the tensioned state.
✪ The equipment produced 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 the core-spun yarn is wrapped by fibers. If the 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 used on a spinning frame to pull the roving When stretching, add the textile materials that need to be wrapped inside. 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.
