The manifestation of spandex in textiles

2021/04/13

Guide:Spandex, the scientific name is polyurethane fiber, the English name is spandex, and the abbreviation is PU. Spandex usually exists in four forms of bare silk, core-spun yarn, covered yarn, and twisted yarn in textiles.





The manifestation of spandex in textiles
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The manifestation of spandex in textiles

spandex

In 1937, the German Bayer company successfully developed;

In 1959, the American DuPont Company began industrial production;

In 1989, Yantai Spandex Plant, China's first spandex production plant, was put into operation. Now, China has become the world's largest producer of spandex.

 

Spandex usually exists in four forms of bare silk, core-spun yarn, covered yarn, and twisted yarn in textiles.

Bare yarn, core-spun yarn, covered yarn and twisted yarn

1. Spandex bare yarn

 

The earliest developed polyurethane elastic fiber varieties have good tensile and recovery properties, and can be used for production without spinning, so they have the advantage of low cost. Due to the large friction coefficient and poor sliding properties of bare silk, few are directly used for weaving fabrics, and it is generally suitable for interweaving with other chemical filaments on knitting machines. The main textile products are tights, sportswear, leg socks, surgical bandages and socks, cuffs, etc.

Spandex bare yarn

2. Core-spun yarn

 

The core-spun yarn is made of spandex yarn as the core and wrapped with one or several inelastic short fibers. The yarn with natural fiber as the outer fiber has good moisture absorption. And because of this kind of coating, the core yarn is generally normal when stretched. It is also not exposed, so it has good comfort, and dark-dyed products will not affect the same color due to the light color of spandex. However, the strength of core-spun yarn is relatively low. Generally, the strength of single yarn is only equivalent to 80% to 90% of that of a single yarn made of the same specification outer fiber.

Core-spun yarn

A yarn spun with polyurethane elastic fiber as the core yarn and outsourcing one or several non-strong short fibers (cotton fiber, wool, polyacrylonitrile fiber, polyester fiber, etc.). The core layer provides excellent elasticity, and the outer fibers provide the required surface characteristics. For example: cotton core-spun yarn, in addition to good elasticity, also maintains the feel and appearance of ordinary cotton yarn. Its fabric has the style, feel and performance of cotton cloth, and can be made into a variety of cotton fabrics; wool core-spun yarn is not only It has the appearance of a general wool fabric and good warmth retention, and the fabric has good resilience, stretches freely when wearing, enhances the sense of comfort, and can show a beautiful body shape. Compared with other elastic yarns, core-spun yarn has a significant feature, that is, the core yarn is not easy to be exposed when the yarn is stretched under tension, so the dyeing effect is good, and it is suitable for products of various colors including dark colors. But its strength is lower than other stretch yarns. Core-spun yarn is the most widely used yarn variety among polyurethane elastic fibers.

 

3. Covered yarn

 Covered yarn

Also known as wrapping yarn, it is a stretch yarn formed by polyurethane elastic fiber as the core and wrapped with synthetic fiber filament or yarn in a spiral manner. The covered yarn feels stiffer, the yarn is thicker, and the woven fabric is thicker. The strength of the covered yarn is the strength of the outer filament or yarn, so it is stronger than the core-spun yarn of the same specification.

 

Covered yarn can be divided into single covered yarn and double covered yarn.

 

Single-covered yarn is a layer of filament or yarn wrapped on the outer layer of polyurethane elastic fiber. Due to the small number of covering turns applied to the core yarn, core exposure may sometimes occur on high-elongation elastic fabrics. It is not suitable for dark-colored products, and is mainly used for elastic fabrics such as socks and weft-knitted underwear.

 

Double-covered yarns are covered with two layers of filaments or yarns on the outer layer of polyurethane elastic fiber, and the wrapping directions of the two layers are opposite. Because the outer fibers are symmetrically wrapped with opposite helix angles, the yarn can be achieved without twisting. The balance of yarn elasticity. The processing cost of double-covered yarn is relatively high, and it is mainly used for elastic fabrics such as leg guards, elastic bands, sock mouths, and pantyhose.

 

Covered yarn is also a stretch yarn formed by using spandex as the core, and non-elastic filament or short fiber yarn wraps the stretched spandex yarn in a spiral manner. One of the most obvious differences between covered yarns and other elastic yarns is the untwisted degree of core yarns. The degree of entanglement between the core yarn and the outer layer is significantly lower than that of the core yarn and the twisted yarn, so its elasticity is higher than the latter two. There is core exposure under tension. If there is a significant color difference between the dyeing depth of spandex yarn and the outer fiber, under tension, the homochromaticity of the textile will be reduced, which is more obvious for dark products. The strength of the covered yarn is mainly the strength of the outer filament or yarn, so the strength is higher.

 

4. Twisted yarn

 

Also called plied yarn, it is made by merging and twisting two other inelastic yarns while drawing the polyurethane elastic fiber. If this kind of yarn is untwisted, a lighter impact is applied to the entire yarn while the tension is weakened, so that the relative movement between the yarns reaches a stable state, and finally the elastic fiber enters the yarn core, and other inelastic yarns As the outer layer, the structure of the twisted yarn can be stabilized. Using this method can produce a variety of fancy twisted yarn or three-in-one twisted yarn.

 

The twisted yarn is mostly used to weave thick and thick fabrics, such as stretch labor cloth, stretch single-sided gabardine, etc. The advantage is that it is evenly dry and the product is clean; the disadvantage is that the hand feels a little harder, and some elastic fibers are exposed to the outside, making it easy to cause color difference during dyeing, so it is generally not used for dark fabrics.

 

Spandex yarn can be combined with various yarns or filaments to produce elastic twisted yarn. Since the spandex yarn is twisted with other yarns, the spandex yarn will be exposed when the yarn is under tension. If the color of spandex is very different from other twisted yarns during dyeing, the textile will have poor homochromaticity and is not suitable for dyeing dark colors. The strength of the twisted yarn is equal to the elasticity of the matched non-elastic yarn, so the strength is higher. The degree of entanglement between spandex yarn and non-elastic yarn is also lower than that of core-spun yarn, so its elasticity is also higher than that of core-spun yarn.

Twisted yarn

 

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