Elastic fiber is an essential material in our lives. Without it, there would be no women’s stockings, no summer swimsuits, no figure-highlighting tights… It can be said that elastic fiber has made an indelible contribution to human beings showing their figures and enjoying the comfort of dressing.
The elastic fiber we often see in the content of clothes is “spandex”. However, if you thought spandex was the only thing available, you’d be wrong. We textile people work tirelessly to develop new fibers and new technologies, striving to contribute more to the clothing industry of mankind… (It seems that we are far away again~~ Come back soon)
According to the definition given by the American Society for Testing and Materials ASTM: elastic fiber filaments are stretched repeatedly to at least 2 times their original length at room temperature, and can quickly return to their original length after the tension is released. A long type of fiber, the following 6 types of fibers can all be called elastic fibers.
1 Diene elastic fiber (rubber yarn)
Diene elastic fiber is commonly known as rubber yarn or elastic yarn, and its elongation rate 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 wear 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. Since it is mainly made into thick yarn, its use in woven fabrics is very limited.
2 Polyurethane fiber (spandex)
Polyurethane elastic fiber refers to a fiber made of a block copolymer with polyurethane as the main component. In my country, it is called spandex. The original trade name in the United States was Spandex, which was later renamed Lycra, Lycra, It is called Elastane in Europe, Neolon in Japan, and Dorlastan in Germany.
Its elasticity comes from the block copolymer network structure of its molecular structure composed of “soft” and “hard” segments. This kind of fiber has different block copolymers and different spinning processes. After forming different “segment” network structures, the elasticity and dyeing and finishing processing properties are also different.
3 Polyetherester elastic fiber
Polyetherester elastic fiber is an elastic fiber produced by melt spinning of polyester and polyether copolymer. It was first produced by Teijin Company in Japan in 1990. Polyetherester elastic fiber not only has high strength, but also has good elasticity. When stretched by 50%, the elasticity of medium-strength elastic fiber is equivalent to that of spandex, and the melting point is also higher. When blended with PET fiber, it can be used at 120℃~130℃ Polyester fibers can also be processed into elastic textiles due to the dyeing process. In addition, they have excellent 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 processed with alkali reduction to improve the drape of the fabric.
This fiber also has the advantages of cheap raw materials, easy production and processing, and is a promising fiber.
4Polyolefin elastic fiber (DOW XLA fiber)
Polyolefin elastic fiber is produced from polyolefin thermoplastic elastomer through melt spinning. XLA, launched by DOW Chemical in the United States in 2002, is the first commercialized polyolefin elastic fiber. It is produced 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°C, is resistant to chlorine bleaching and strong acid and alkali treatment, and has strong resistance to ultraviolet degradation. Its production process is relatively simple, its raw material price is lower than that of spandex, and it produces almost no pollution during the production process and is easy to recycle.
Because polyolefin elastic fibers have a variety of excellent properties, their applications have become increasingly widespread in recent years.
5 Composite elastic fiber (T400 fiber)
CONTEX (ST100 composite elastic fiber, collectively referred to as T400 elastic fiber in the market) is a new two-component composite elastic fiber made from DuPont Sorona as the main raw material and ordinary PET through advanced composite spinning technology. ; It has natural permanent spiral curl and excellent bulking, elasticity, elastic recovery rate, color fastness and particularly soft feel. It can be woven alone or interwoven with cotton, viscose, polyester, nylon, etc. to form A wide variety of styles.
It not only solves many problems such as traditional spandex yarn is not easy to dye, has excessive elasticity, is complex in weaving, is unstable in fabric size, and is prone to aging during use, but it can also be directly used in air-jet, water-jet, and arrow shaft weaving. Weaving on the machine does not have to be made into covered yarn before weaving on the machine like spandex, which reduces the cost of the yarn and improves the quality uniformity of the product.
6 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 perspective, elasticity comes from the degree of freedom (or disorder) of the molecular chain, that is, the change in the entropy value of the system. Therefore, 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, although not easy to deform under low stress (because they have a higher modulus), are not easily deformed under high stress. It also has good elasticity under stress, especially at lower temperatures, so this type of fiber is called hard elastic fiber.
The deformation and recovery of hard elastic fibers are significantly different from those of elastic fibers. For example, hard elastic PIf the P fiber is stretched for the second time immediately after being stretched and recovered, its modulus and strength will drop a lot. However, if the stress is removed and left for a period of time, or the temperature is raised to fully relax and then stretched for the second time, then Its 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 retracting deformation of the long chain segments of the crimped molecules of the soft elastic fiber occur, but also some changes in the micropore structure are accompanied 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. Therefore, they deform and recover under higher pressure and 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.
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