Elastic fiber has made an indelible contribution to human beings to show their figure and enjoy the comfort of dressing. Girls' sexy stockings, summer bikinis, and winter beautiful and slim tights are all inseparable from her.

Spandex is a common elastic fiber that can increase the comfort and flexibility of people's activities. However, if you think that elastic fibers are only spandex, you are quite wrong. According to the ASTM definition of the American Society for Testing and Materials, elastic fiber refers to a type of fiber that is repeatedly stretched to at least twice its original length at room temperature, and can quickly return to its original length after the tension is released. Therefore, The following 6 types of fibers can all be called elastic fibers.

1. Diene elastic fiber (rubber wire)

Diene elastic fibers are commonly known as rubber yarns or elastic yarns, and their elongation is generally between 100% and 300%. The main chemical component is vulcanized polyisoprene, which has good chemical and physical properties such as high temperature resistance, acid and alkali resistance, and abrasion resistance. It is widely used in knitting industries such as socks and ribbed cuffs. Rubber yarn is an elastic fiber used in the early days. Because it is mainly made into coarse yarns, its use in woven fabrics is very limited.

2. Polyetherester elastic fiber

Polyetherester elastic fiber is an elastic fiber made of polyester and polyether copolymer through melt spinning. It was first produced in 1990 by Teijin Corporation of Japan. Polyetherester elastic fiber not only has higher strength, but also good elasticity. At 50% elongation, the elasticity of medium-strength elastic fiber is equivalent to spandex, and the melting point is also higher. It can be blended with PET fiber at 120 ℃ ~ 130 ℃ Under dyeing, polyester fibers can also be processed into elastic textiles. In addition, their light resistance, chlorine bleaching resistance, acid and alkali resistance, etc. are better than ordinary spandex. Due to its good acid and alkali resistance, the fabric composed of it and polyester can also be reduced in weight to improve the drape of the fabric. This kind of fiber also has the advantages of cheap raw materials, easy production and processing, and it is a kind of more promising fiber.

3. Polyolefin elastic fiber

Polyolefin elastic fiber is made of polyolefin thermoplastic elastomer by melt spinning. XLA, launched by DOW Chemical in 2002, is the first commercialized polyolefin elastic fiber. It is made by melt spinning of ethylene-octene copolymer (POE) catalyzed by metallocene catalyst in situ polymerization. . It has good elasticity, 500% elongation at break, can withstand high temperatures of 220 ℃, resistant to chlorine bleaching and strong acid and alkali treatment, and has strong resistance to UV degradation. Its production process is relatively simple, the price of raw materials is lower than that of spandex, and at the same time, there is almost no pollution during the production process and it is easy to recycle. As polyolefin elastic fibers have a variety of excellent properties, they have become increasingly widely used in recent years.

4. Composite elastic fiber

CONTEX (ST 100 composite elastic fiber, collectively referred to as T400 elastic fiber in the market) is a two-component new composite elastic fiber made from DuPont Sorona as the main raw material and through an advanced composite spinning process with ordinary PET. It has a natural permanent spiral. Curl and excellent bulkiness, elasticity, elastic recovery rate, color fastness and particularly soft hand feeling. It can be woven alone or interwoven with cotton, viscose, polyester, nylon, etc. to form a variety of types style.

It not only solves the problems of traditional spandex yarns that are not easy to dye, excessive elasticity, complex weaving, unstable fabric size, and easy aging during use, but also can be woven directly on air jet, water jet, arrow shaft looms, and does not need to be like spandex. In that way, it must be made into covered yarn before weaving on the machine, which reduces the cost of yarn and improves the quality uniformity of the product.

5. Hard elastic fiber

The above-mentioned elastic fibers are all soft elastic fibers, which undergo greater deformation and recovery under lower stress. From a thermodynamic point of view, elasticity comes from the degree of freedom (or disorder) of the molecular chain, that is, the change in the entropy of the system, so the crystallinity of the above-mentioned fibers is very low. However, some fibers made under special processing conditions, such as polypropylene (PP), polyethylene (PE) and other fibers, are not easily deformed under low stress (because they have a higher modulus), but at higher Under stress, especially at lower temperatures, it also has better elasticity, so this type of fiber is called hard elastic fiber.

The deformation and recovery of hard elastic fibers are significantly different than elastic fibers. For example, the hard elastic PP fiber is stretched for the second time immediately after being stretched and recovered, its modulus and strength will drop a lot, but if it is left for a period of time after the stress is removed, or the temperature is increased to fully relax it, then the second stretch is performed. Extension, the deformation recovery is basically close to the first curve. This is because when the hard elastic fiber is stretched and recovered, not only the stretching and shrinking deformation of the long chain segment of the soft elastic fiber crimping molecule occurs, but also some changes in the microporous structure during the stretching process. The chip network structure has also changed. Only after these structural changes gradually recover, can they return to their original state, so they deform and recover under higher pressure, which are called hard elastic fibers.

At present, hard elastic fibers are not widely used in textiles, but because their elastic characteristics are different from soft elastic fibers, some special textiles can be developed.