Elastic fiber is an essential material in our lives. Without it, there would be no stockings for women, no swimsuits for summer, no tights to highlight the figure…It can be said that elastic fibers have made an indelible contribution to human beings to show their figure and enjoy the comfort of dressing.
The elastic fiber we often see in the composition of clothes is “spandex”. Although the content is not high, it is very important, such as wholesale spandex leggings.
When shopping online, check the ingredient label of the clothes. If you see spandex, you can roughly know that the clothes have a slimming effect. Clothes without elastic fibers are generally looser and not too close to the body, otherwise, it will hinder normal activities.
However, if you think that elastic fibers are only spandex, you are very wrong.
According to the definition given by the American Society for Testing and Materials (ASTM): elastic fiber refers to a type of material 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 . The following 6 types of fibers can all be called elastic fibers.
Diene Elastic Fiber (Rubber Yarn)
Diene elastic fiber is commonly known as rubber yarn or elastic yarn, and its 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 rib cuffs.
Rubber thread 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.
Polyurethane Fiber (Spandex)
Polyurethane elastic fiber refers to a fiber made of a block copolymer with polyurethane as the main component. It is referred to as spandex in China. The original product name in the United States was Spandex, which was later renamed Lycra in America, Elastane in Europe, Neolon in Japan, and Dorlastan in Germany.
Its elasticity comes from its molecular structure: a block copolymer network structure composed of all “soft” and “hard” segments. With different block copolymers and different spinning processes, this fiber has different elasticity and dyeing and finishing performance after forming different “segment” network structures.
Polyetherester Elastic Fiber
Polyetherester elastic fiber is an elastic fiber made of polyester and polyether copolymer through melt spinning. It was first produced by Teijin Corporation in 1990. Polyetherester elastic fiber not only has high strength, but also has good elasticity. At 50% elongation, the elasticity of medium-strength elastic fiber is equivalent to spandex, and the melting point is also higher. Blended with PET fiber, it can be dyed at 120 ℃ ~ 130 ℃, so polyester fiber can also be processed into elastic textiles.
In addition, its light resistance is excellent, and its chlorine bleaching resistance, acid and alkali resistance are better than ordinary spandex. Due to its good acid and alkali resistance, the fabric composed of it and polyester can also be processed by alkali reduction to improve the drape of the fabric.
This kind of fiber also has the advantages of cheap raw materials, easy production and processing, and is a kind of fiber with more development prospects.
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 catalysts. . It has good elasticity, 500% elongation at break. It can withstand high temperature of 220℃, resistant to chlorine bleaching and strong acid and alkali treatment, and has strong resistance to ultraviolet degradation.
Its production process is relatively simple, and the price of raw materials is lower than that of spandex. At the same time, there is almost no pollution during the production process and it is easy to recycle. As polyolefin elastic fiber has a variety of excellent properties, it has become increasingly widely used in recent years.
Composite Elastic Fiber
CONTEX (ST 100 composite elastic fiber, collectively referred to as T400 elastic fiber in the market) is a new type of two-component composite elastic fiber, which is made of DuPont Sorona and ordinary pet through advanced composite spinning process. It has natural permanent spiral curl, excellent bulkiness, elasticity, elastic recovery, color fastness and special soft handle. It can not only be pure woven alone, but also be interwoven with cotton, viscose, polyester, nylon, etc In a variety of styles.
It not only solves the problems of traditional spandex yarn, such as difficult dyeing, excessive elasticity, complex weaving, unstable fabric size, and easy aging in the process of use, but also can be directly woven on air-jet, water jet and arrow bar looms. It does not need to be made into coated yarn before weaving, which reduces the cost of yarn and improves the quality uniformity of products.
Hard Elastic Fiber
The above-mentioned elastic fibers are all soft elastic fibers, which undergo greater deformation and recovery under lower stress. From the perspective of thermodynamics, elasticity comes from the degree of freedom (or disorder) of the molecular chain, that is, the change in the entropy 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, are not easily deformed under low stress (because they have a higher modulus). But under higher stress, especially at lower temperature, it also has better elasticity, so this type of fiber is called hard elastic fiber.
The deformation and recovery of hard elastic fiber are obviously different from that of elastic fiber. For example, the modulus and strength of hard elastic PP fiber will decrease a lot if it is stretched for the second time immediately after tensile recovery. However, if the stress is removed and placed for a period of time, or the temperature is raised to make it fully relaxed, the deformation recovery is close to the first bending base.
This is because when the hard elastic fiber is stretched and recovered, not only the stretching and retracting deformation of the long chain segment of the soft elastic fiber curling molecule occurs, but also some changes of the micropore structure and the wafer network structure are also occurred during the stretching process. Only when these structural changes gradually recover can they return to the original state. They are called hard elastic fibers because of their deformation recovery under high pressure.
At present, rigid elastic fibers are not widely used in textiles. However, due to its elastic characteristics different from soft elastic fiber, it can be developed into some special textiles.