1. Diene Elastic Fiber (Rubber Wire)
Diene elastic fiber is commonly called rubber yarn or rubber band 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 wear resistance, and is widely used in knitting industries such as socks and rib cuffs. Rubber yarn is an early elastic fiber. Because it is mainly made into coarse yarn, its application in weaving fabric is limited.
2. Polyurethane Fiber (Spandex)
Polyurethane elastic fiber refers to a kind of fiber made of block copolymer with polyurethane as the main component, which is referred to as Spandex in China. The original trade name in the United States is Spandex, later renamed Lycra in Europe, Elastane in Europe, Neolon in Japan and Dorlastan in Germany. Its elasticity comes from the block copolymer network structure whose molecular structure is composed of so-called "soft" and "hard" segments. This kind of fiber has different elasticity and dyeing and finishing properties with different block copolymers and different spinning processes and different "segment" network structures.
The spinning methods of spandex include dry spinning, wet spinning, chemical reactive spinning and melt spinning. Dry spinning technology is the most common method for industrial production of spandex at present, which has the advantages of fast spinning speed (1000 m/min), small spinning fineness, good product quality and small workshop area, but at the same time it has the disadvantages of serious environmental pollution and high cost. On the contrary, melt spinning technology, which does not use solvents and coagulants, has no problem of wastewater treatment, low production cost and great development potential, is one of the hot spots in current research.
Spandex is the earliest developed and most widely used elastic fiber with the most mature production technology.
3. Polyether Ester Elastic Fiber
Polyether ester elastic fiber is an elastic fiber made of polyester and polyether copolymer by melt spinning. Polyether ester elastic fiber is similar to polyurethane elastic fiber in structure, and also has "segment" structural characteristics. The "soft" segment is mainly polyether segment, which has good flexibility, long chain and easy elongation and deformation; The "hard" segment is a polyester segment, which is relatively stiff, easy to crystallize and short. It acts as a node when the fiber is deformed by force, giving it elastic recovery performance and determining the strength and heat resistance of the fiber.
Polyether ester elastic fiber not only has high strength, but also has good elasticity. When it is stretched by 50%, the elasticity of medium-strength elastic fiber is equivalent to that of spandex, and its melting point is also high. When it is blended with PET fiber, it can be dyed at 120~130℃, so polyester fiber can also be processed into elastic textiles. In addition, their light fastness, chlorine bleaching resistance, acid and alkali resistance are better than ordinary spandex. Because of its good acid and alkali resistance, the fabric composed of it and polyester can also be processed by alkali deweighting to improve the drape of the fabric.
This kind of fiber also has the advantages of cheap raw materials and easy production and processing, and it is a kind of fiber with more development prospects.
4. Composite elastic fiber (T400 fiber)
CONTEX Contex (ST 100 composite elastic fiber, collectively referred to as T400 elastic fiber in the market) is a new bicomponent composite elastic fiber made of DuPont Sorona as the main raw material and ordinary PET through advanced composite spinning process. It has natural and permanent spiral curl, excellent bulkiness, elasticity, elastic recovery rate, color fastness and particularly soft hand feeling. It can be woven alone or interwoven with cotton, viscose, polyester and nylon to form various styles. It not only solves many problems of traditional spandex yarn, such as difficult dyeing, excessive elasticity, complicated weaving, unstable fabric size, and easy aging during use, but also can be directly woven on air-jet, water-jet and arrow-bar looms, without having to make covered yarn before weaving on the machine like spandex, which reduces the cost of yarn and improves the quality uniformity of products.
5. Polyolefin Elastic Fiber (DOW XLA Fiber)
Polyolefin elastic fiber is made of polyolefin thermoplastic elastomer by melt spinning. XLA, introduced by DOW Chemical in 2002, is the first commercial polyolefin elastic fiber, which is prepared by melt spinning of ethylene-octene copolymer (POE) catalyzed by metallocene catalyst. It has good elasticity, 500% elongation at break, resistance to high temperature of 220℃, chlorine bleaching and strong acid and alkali treatment, and strong resistance to ultraviolet degradation. Its production process is simple, the price of raw materials is lower than that of spandex, and at the same time, there is almost no pollution in the production process and it is easy to recycle.
Polyolefin elastic fiber has been widely used in recent years because of its many excellent properties.
6. Hard Elastic Fiber
The above elastic fibers are all soft elastic fibers, which undergo great deformation and recovery under lower stress. From the thermodynamic point of view, elasticity comes from the degree of freedom (or disorder) of molecular chain, that is, the change of entropy value of the system, so the crystallinity of the above fibers is very low. However, some fibers made under special processing conditions, such as polypropylene (PP) and polyethylene (PE), are not easy to deform under low stress (because they have higher modulus), but they also have better elasticity under higher stress, especially at lower temperature, so these fibers are called hard elastic fibers.
The deformation and recovery of hard elastic fibers are obviously different from those of elastic fibers. For example, when the hard elastic PP fiber is stretched for the second time immediately after stretching recovery, its modulus and strength will be greatly reduced. However, if it is left for a period of time after stress is removed, or the temperature is raised to make it fully relaxed and then stretched for the second time, its deformation recovery is basically close to the curve of the first time. This is because when the hard elastic fiber is stretched and recovered, not only the stretching and retraction deformation of the long-chain segment of the curled molecule of the soft elastic fiber occurs, but also some changes in micropore structure are accompanied during the stretching process, and their wafer network structure has also changed. Only after these structural changes are gradually restored can they return to their original state, so they are deformed and restored under high pressure, which is called hard elastic fiber.
At present, hard elastic fibers are not widely used in textiles, but because their elastic characteristics are different from those of soft elastic fibers, some special textiles can be developed.