What Is Single Covered Yarn


Single covered yarn (SCY) is made by continuously rotating and winding the outer fiber filament on the core spandex that is drawn at a uniform speed. It is twisted and has strong strength (TPM). The fabric style is smooth and crisp as its main feature.

Covered Spandex Yarn generally has single-pack, double-pack and other covering forms. Among them, nylon ammonia and polyester ammonia are mostly coated in a single package. In the spinning process, Spandex Stretch is an important process parameter. It affects the elasticity of the covered yarn and fabric, and also affects the elongation, evenness and creep properties of the covered yarn. The pre-draft ratio 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.

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In addition, the percentage content of spandex yarn also affects the elasticity of the covered yarn. High content means good elasticity. Under the condition of a certain specification of polyamide fiber, increasing the draft ratio will reduce the percentage of spandex fiber, that is, the pre-draft ratio of spandex is inversely proportional to the percentage of spandex in the finished yarn. The strength and stretch of the covered yarn increases with the increase of the spandex pre-drafting multiple. After the spandex yarn is stretched to a certain value, the retractability of the spandex yarn causes the outer fiber to be curled, and the spandex core yarn is straightened.

Appropriately increase the pre-drafting ratio, the percentage of spandex will decrease, and the degree of curling of the outer fiber will increase. 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.

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The phenomenon of deformation changing with time under the action of constant drafting force is called creep. The creep resistance of the covered yarn is the best when the spandex yarn is pre-stretched 3.5 times. The twist of the machine package affects the quality, elongation and evenness of the yarn. Increasing the twist can increase the cohesion between the covering fiber and the spandex yarn, thereby increasing the strength of the covering yarn. The elongation of the machine bag is mainly determined by the performance of the spandex core yarn. If the twist is too large and the outer fiber is wrapped too tightly, the elastic effect of the spandex yarn cannot be fully exerted, causing the elongation to decrease. As twist increases, evenness improves.

The twist is too small and the outer fibers are loose. During the spinning process, the fibers will move slightly along the axis of the yarn due to friction and other reasons, so the evenness deteriorates. The presence of spandex yarn in the machine package will weaken the cohesion between the outer fiber filaments. The resultant force, the twist is too low, and the outer fiber is loose, which affects the covering effect and exposes the core. Therefore, the twist should be higher during mechanical covering. But if the twist is too high, the fabric will feel hard and have poor drape. Generally, the twist should be adjusted as the denier of the yarn changes. For example, for N40D+20D machine package, the twist is 600, while for N70D+40D or T150D+40D machine package, the twist degree should be controlled at around 480. Some small spinning machines In order to consider delivery time and reduce production costs, yarn mills will reduce the speed or increase the speed of equipment to increase output, which is not conducive to the quality of wrapped yarn.

Due to the high strength and hardness of machine-covered yarn, it is suitable for knitted fabrics requiring high elasticity, and some are used for woven fabrics, such as high-grade thin wool and linen fabrics, jacquard double-layer weft knitted fabrics and warp knitted fabrics, etc. ideal yarn. It can usually be made into T-shirts, suits and other slightly stiff fabrics. Machine-wrapped yarn can also be made into products with high wear resistance requirements such as industrial supplies and sports equipment. Covered yarn can be spun into both thick and thin yarns, with elastic yarns being the majority, suitable for weaving sports tights, such as swimwear, ski suits, women's underwear, etc. The covering yarn has a higher strength than any single yarn by selecting the appropriate core yarn and covering yarn according to the purpose.

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