How many kinds of elastic fibers do you know?

Elastic fiber refers to tow with high extensibility and high resilience. The most classic definition is a kind of fiber given by the American Society for Testing and Materials ASTM: "At room temperature, the material is repeatedly stretched to at least 2 times its original length, and can quickly recover to its original length after the tension is released". For polyurethane materials, it refers to the fiber that can quickly recover to its original length after the tension is released to 3 times its original length. In addition, there are other definitions according to different countries and regions.
Among many functional varieties, elastic fiber, as a "sunrise industry", can give the human body a good sense of contact, and plays an irreplaceable role in clothing comfort, bulkiness and warmth, so it occupies a stable position in the textile industry in China and even in the world, and giving textile fabrics a certain degree of elasticity has become an inevitable development trend of clothing textiles.
1、 Diene elastic fiber (rubber filament)
The diene elastic fiber is commonly known as rubber wire or rubber band wire, 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, wear resistance, and is widely used in the knitting industry such as socks, rib cuffs, etc. Rubber fiber is an elastic fiber used in the early stage. Because it is mainly made into coarse count yarn, its application range in weaving fabric is very limited.
2、 Polyurethane fiber (spandex)
Polyurethane elastic fiber refers to the fiber made of a block copolymer with polyurethane as the main component. It is referred to as spandex in China. The original trade name in the United States was Spandex, and later changed to Lycra in Leica, Elastane in Europe, Neolon in Japan, and Dorlastan in Germany. Its elasticity comes from the block copolymer network structure composed of so-called "soft" and "hard" segments. With different block copolymers and different spinning processes, this fiber has different elasticity and dyeing and finishing properties after forming different "block" network structures.
The spinning methods of spandex include dry spinning, wet spinning, chemical reaction spinning and melt spinning. Dry spinning technology is the most common method in the current spandex industry production. It has the advantages of fast spinning speed (1000m/min), small spinning size, good product quality and small workshop area, but it also has the disadvantages of serious environmental pollution and high cost. On the contrary, melt spinning technology, which does not use solvent and coagulant, has no problem of wastewater treatment, low production cost, and has great development potential, is one of the current research hotspots.
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 a kind of elastic fiber made from polyester and polyether copolymer by melt spinning. It was first produced in 1990 by Imperial Corporation of Japan. The structure of polyether ester elastic fiber is similar to that of polyurethane elastic fiber, and it also has the characteristics of "section" structure. The "soft" chain segment is mainly polyether chain segment, with good flexibility, long chain length and easy elongation and deformation; The "hard" chain segment is a polyester chain segment, which is relatively rigid, easy to crystallize, and short in chain. It acts as a node when the fiber is deformed under stress, endows elastic recovery performance, and determines the strength and heat resistance of the fiber.
Polyether ester 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 that of spandex, and its melting point is also high. It is blended with PET fiber and 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. 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 drapability 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 promising development prospects.
4、 Polyolefin elastic fiber (DOW XLA fiber)
Polyolefin elastic fiber is prepared by melt spinning of polyolefin thermoplastic elastomer. The XLA launched by Dow Chemical in 2002 is the first commercially available polyolefin elastic fiber, which is prepared by melt spinning of ethylene-octene copolymer (POE), which is polymerized in situ by metallocene catalyst. It has good elasticity, 500% breaking elongation, 220 ℃ high temperature resistance, chlorine bleaching resistance and strong acid and alkali treatment, and strong ultraviolet degradation resistance. Its production process is relatively simple, the price of raw materials is lower than that of spandex, and there is almost no pollution in the production process and it is easy to recycle.
Because polyolefin elastic fiber has many excellent properties, it has been widely used in recent years.
5、 Composite elastic fiber (T400 fiber)
Contex (ST 100 composite elastic fiber, commonly referred to as T400 elastic fiber in the market) is a new two-component composite elastic fiber made with DuPont Sorona as the main raw material and ordinary PET through advanced composite spinning process; It has natural permanent spiral curl, excellent bulkiness, elasticity, elastic recovery rate, color fastness and special soft feel. It can be woven alone or interwoven with cotton, viscose, polyester, nylon, etc. to form a variety of styles. It not only solves many problems of traditional spandex yarn, such as difficulty in dyeing, excess 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 rod looms. It does not need to be made into coated yarn before weaving, like spandex, which reduces the cost of yarn and improves the quality uniformity of products.
6、 Hard elastic fiber
The above elastic fibers are soft elastic fibers, which will undergo large deformation and recovery under low stress. From the perspective of thermodynamics, the elasticity comes from the degree of freedom (or chaos) of the molecular chain, that is, the change of the system entropy, so the crystallinity of the above fibers is very low. However, some fibers made under special processing conditions, such as polypropylene (PP), polyethylene (PE), are not easy to deform under low stress (because they have high modulus), but also have good elasticity under high stress, especially at low temperature, so these fibers are called hard elastic fibers.
The deformation and recovery of hard elastic fiber are significantly different from that of elastic fiber. For example, the modulus and strength of the hard elastic PP fiber will decrease a lot after the second stretch immediately after the tensile recovery, but if it is placed for a period of time after the stress is removed, or if the temperature is raised to make it fully relax, and then the second stretch is carried out, its deformation recovery is close to the original 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 soft elastic fiber crimping molecule occurs, but also some changes in the microporous structure and their chip network structure occur during the stretching process. Only after these structural changes are gradually restored, can they return to the original state, so they will undergo deformation recovery 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 soft elastic fibers, some special textiles can be developed.