Spandex, translated as "spandex", is an elastic fiber, the scientific name is polyurethane fiber, or PU for short. Chinese mainland is called "spandex", which has high elasticity and can be stretched by 6 ~ 7 times, but it can recover quickly with the disappearance of tension. Its molecular structure is chain-like, soft and malleable polyurethane, and its characteristics are enhanced by connecting with hard segments. Spandex has excellent elasticity. The strength is 2 ~ 3 times higher than that of latex yarn, the linear density is thinner and it is more resistant to chemical degradation. Spandex has good acid and alkali resistance, perspiration resistance, seawater resistance, dry cleaning resistance and wear resistance. Synthetic fiber with high elongation at break (above 400%), low modulus and high elastic recovery rate. China trade name of multiblock polyurethane fiber. Also called elastic fiber. Spandex has high elongation (500% ~ 700%), low elastic modulus (200% elongation, 0.04 ~ 0. 12g/ denier) and high elastic recovery (200% elongation, 95% ~ 99%). In addition to high strength, other physical and mechanical properties are very similar to those of natural latex yarn. It is more resistant to chemical degradation than latex wire, with moderate thermal stability and softening temperature above 200℃. Most dyes and finishing agents used for synthetic fibers and natural fibers are also suitable for dyeing and finishing spandex. Spandex is sweat-resistant, seawater-resistant, resistant to all kinds of dry cleaners and most sunscreen oils. Long-term sun exposure or chlorine bleach will also fade, but the degree of fading varies with the type of spandex. The reason why spandex fiber has such high elasticity is that its polymer chain consists of low melting point amorphous "soft" segments as matrix and high melting point crystalline "hard" segments embedded in it. The molecular chains of flexible segments are crosslinked to form a certain network structure. Because the interaction between molecular chains is very small, they can expand and contract freely, resulting in great elongation. The molecular connecting force of the rigid segment is relatively large, and the molecular chain will not extend indefinitely, so the elasticity is high. Most of the cross sections of radon nylon wires are dog-bone-shaped, and some wires have smooth or serrated surfaces. The breaking strength is the lowest among all textile fibers, only 0.44 ~ 0.88 cn/dtex (the strength of polyether type is higher than that of polyester type). The moisture absorption range is small, generally 0.3- 1.2% (the moisture absorption rate of multifilament is slightly higher than that of monofilament). Heat tolerance varies greatly with different varieties. Most fibers will not be damaged when stored for a short time in the range of 90 ~ 150℃. The safe ironing temperature is below 150℃, which can be heated and disturbed and wet washed. It has excellent dyeing performance, can be dyed in various shades, has strong affinity for fibers, can adapt to most kinds of dyes, has good chemical resistance, is resistant to most acids, alkalis, chemicals, organic solvents, dry cleaning and bleaching agents, and is resistant to sunlight and snow, but is not resistant to oxides, which easily make fibers yellow and reduce strength. Generally, spandex is not used alone, but a small amount is mixed into the fabric. This kind of fiber has both rubber properties and fiber properties, and is often used in core-spun yarn with spandex as the core, which is called elastic core-spun yarn. The main characteristics of this kind of yarn are: first, it can obtain good hand feel and appearance, and the outer fiber is composed of natural fiber, which has good hygroscopicity; Second, only 1- 10% spandex filament can produce high-quality elastic yarn; Thirdly, the control range of elasticity percentage is from 10% to 20%, and different elasticity values can be selected according to the use of the product. It is easy to spin silk with different thickness of 25 ~ 2500 denier, so it is widely used to make elastic knitted fabrics, such as socks, furniture covers, ski clothes, sportswear, medical fabrics, belts, military equipment, elastic parts of spacesuits and so on. As people put forward new requirements for fabrics, such as lightness, comfort and softness, the proportion of low denier spandex fabrics in synthetic fiber fabrics is also increasing. There are nude spandex yarns and twisted yarns formed by combining spandex with other fibers, which are mainly used in various warp-knitted and weft-knitted fabrics, woven fabrics and elastic fabrics. Since 1958 DuPont introduced spandex into commercial use and registered its trademark as (Lycra), the market transliteration was [Lycra], many people took "LYCRA" as the name of spandex. Since then, it has been produced all over the world, such as VYRENE of American rubber company, ESPA of Toyo Textile of Japan, DORLASTAN of Bayer Company of Germany, COURTAULDS of West Germany and COURTAULDS of Britain. (ESTANE by B.F. Goodrich Chemical Co, Ltd., FUJIBO by Japan, Toray-DUPONT by DuPont and Toray by Toray by Japan, CLEARSPAN and GLOSPAN by GLOBEMANUFACTURING CO of the United States, ACELAN by TAE Light of Korea, and Eastward's). ROIKO of Asahi Kasei, Japan, later cooperated with Formosa Plastics Group of Taiwan Province Province in early 1999 to establish Formosa Plastics Corporation, referred to as FAS, and Japan's MOBILON also increased its production line in Taiwan Province Province to produce Donghua yarn, while Taiwan Province Province invested her in Xingzhi, Xue Heng Province. There are also Neustad in Yantai and Aoshen in Lianyungang in Chinese mainland, all of which are produced by the equipment and technology of Toyo Spinning, while Guangdong Heshan spandex Factory 1996 was put into production, Fujian Changle, Nantong Haimen and Shandong Zibo also started to produce spandex, China DuPont cooperated with Shanghai Huayuan, and Zhejiang Huafeng's "Millennium" brand spandex was also produced in 2000. In addition, DuPont also cooperates with other factories (but DuPont is not involved in production matters) and sells them under the brand "ELASPAN". All parts of the world have invested in or increased the production of spandex, making the spandex market prosperous. [2] Dupont of China cooperated with Huayuan in Shanghai, and Zhejiang Huafeng "Millennium" brand spandex was put into production in 2000. In 2004, Zhejiang Hualai spandex was completed and put into production, adopting the most advanced Japanese "Nissin Spinning" spandex production process. 7 Production method Editor's summary spandex fiber overcomes the quality defects of rubber yarn such as stress, strain performance, count range and modulus. Dupont first used dry spinning in those years. Up to now, there are roughly four production methods: dry spinning: the method in which the solution is solidified into filaments due to solvent volatilization under hot air flow. Production technology: solution (passing through)-spinning pump (filtering)-oven (blowing 100℃ hot air to volatilize the solution)-spinning-winding forming spinning speed: 200-800m/min, spinning temperature: 200-230℃. Melt spinning: a method of heating a polymer above its melting point to melt it and spin it into silk. Production technology: solvent-free polymer polymerization-granulation-constant temperature slicing-cleaning and impurity removal-drying-dehydration-solution entering screw press mechanism-spinneret extrusion-cold box cooling-winding molding. Spinning speed: 600 ~ 1600 m/min, spinning temperature: 160 ~ 220℃, fiber size: 9 ~1/00 dtex, Uses: Bell spinning, Bayer spinning and Nissin spinning. Features: short process, low cost and little pollution (wet spinning). Production process: stock solution-spinning pump (filtration)-warm water from spinneret (below 90℃)-coagulation bath in regeneration tank-solvent removal-silk washing-drying-winding rotation speed: from 50 ~1 Spinning temperature: below 90℃; Warm water fiber size: 44 ~ 440 dtex Japanese Fuji spinning characteristics: This method is characterized by heavy pollution, slow spinning speed and high cost. Chemical reaction method A method in which a polymer solution reacts chemically with a chain extender and solidifies into filaments. Production technology: solution-from spinneret to solidification solution-adding chain extender (chemical reaction)-winding forming-hardening-processing into mesh fiber. Spinning speed: from 50 ~ 150 m/min, fiber size: 44 ~ 80 dtex. General characteristics of the United States: this method has great pollution and high cost in the production process. 8 Shape Editor spandex also has different brightness shapes in production, usually: (Take DuPont as an example) clear type: the surface fiber is smooth, so it is transparent, low friction rate, poor uniformity and chromatic aberration, which is suitable for short fiber material production and widely used in warp fabrics. Dull: white, uneven surface fibers, large friction surface and good coloring effect. Suitable for producing long fibers, used for thick roots, such as bust and accessories. Glossy: Titanium dioxide and anti-slip agent are added, which has strong resistance to chemical agents. Swimsuit is widely used because of its chlorine resistance. Subgloss: between white and translucent, it is dumb white and suitable for knitting. Spandex has different uses and various product forms, which are mainly divided into bare yarn, core-spun yarn, covered yarn or twisted yarn. Each different combination corresponds to a different purpose. Bare yarn: 100% spandex yarn. Bare yarn is generally not directly used in fabrics, but is mostly produced by hand, which requires special equipment. Knitwear is the most commonly used, such as swimsuit and sportswear, generally 22-78Dtex. Core-spun yarn is spun with bare yarn as the core and other materials as the skin, which is called CSY for short. If the stretched bare yarn is inserted into the ring spinning frame with cotton core, the elongation of the bare yarn of core-spun yarn must be properly adjusted to restrain its expansion rate to 2 ~ 3 times. Nowadays, core-spun yarn can be divided into hard core yarn and soft core yarn. The competitive raw materials of core-spun yarn are cotton, polyester and acrylic fiber. Widely used in fabrics, knitwear, bandages, socks, underwear, jeans, generally 22-235Dtex.