Spandex, polyurethane fiber, a very elastic fiber, is often used in knitted inner clothing, especially underwear, bikinis and the like. It was first successfully developed by Du Bang Company in 1958 and given the registered trade name LYCRA (Lycra), so some people call it Lycra. Spandex, translated as "Spandex", is a kind of elastic fiber, its scientific name is polyurethane fiber (Polyurethane), abbreviated as (PU). Called "spandex" in mainland China, it is highly elastic and can be stretched 6 to 7 times, but can quickly return to its original state as the tension disappears. Its molecular structure is chain-like, soft and extensible. Polyurethane, which enhances its properties by linking together hard segments. Spandex has excellent elasticity. The strength is 2 to 3 times higher than latex silk, the linear density is also thinner, and it is more resistant to chemical degradation. Spandex has good acid and alkali resistance, sweat resistance, seawater resistance, dry cleaning resistance, and abrasion resistance. Synthetic fiber with high elongation at break (above 400), low modulus and high elastic recovery rate. Chinese trade name for multi-segmented polyurethane fiber. Also known as elastic fiber. Spandex has high elongation (500-700), low elastic modulus (200 elongation, 0.04-0.12 g/den) and high elastic recovery rate (200 elongation, 95-99). In addition to its greater strength, other physical and mechanical properties are very similar to natural latex silk. It is more resistant to chemical degradation than latex silk, has moderate thermal stability, and has a softening temperature above about 200°C. Most dyes and finishes used for synthetic and natural fibers are also suitable for dyeing and finishing spandex. Spandex is resistant to sweat, sea water, various dry cleaning agents and most sunscreen oils. It can also fade with long-term exposure to sunlight or chlorine bleach, but the degree of fading varies greatly depending on the type of spandex. The reason why spandex fiber has such high elasticity is that its polymer chain is composed of low-melting, amorphous "soft" segments as the matrix and high-melting, crystallized "hard" segments embedded in it. The flexible segment molecular chains are cross-linked to form a certain network structure. Due to the small interaction force between the molecular chains, they can expand and contract freely, resulting in large elongation performance. The molecular chain binding force of the rigid segment is relatively large, and the molecular chain will not extend indefinitely, resulting in high resilience. Most of the cross-sections of radon filaments are dog-bone-shaped, and some filaments have smooth or jagged surfaces. The breaking strength is the lowest among all textile fibers, only 0.44~0.88CN/dtex (the strength of polyether type is higher than 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). The heat resistance varies greatly depending on the variety. Most fibers will not be damaged when stored for a short period of time in the range of 90 to 150°C. The safe ironing temperature is below 150°C, and heating interference and wet cleaning are possible. It has excellent dyeing performance and can be dyed into various colors. The dye has strong affinity for fibers and can be adapted to most types of dyes. It also has good chemical resistance and is resistant to most acids, alkalis, chemicals, organic solvents, It is resistant to dry cleaning agents and bleaches, and is resistant to sunlight, wind and snow, but is not resistant to oxidants, which can easily cause the fibers to turn yellow and reduce their strength. Spandex is generally not used alone, but is incorporated into fabrics in small amounts. This kind of fiber has both rubber and fiber properties. It is mostly used in core-spun yarns with spandex as the core yarn, which is called elastic core-spun yarn. The main characteristics of this kind of yarn are: first, it can obtain good feel and appearance; The outer fiber composed of natural fibers has good hygroscopicity; secondly, high-quality elastic yarn can be produced with only 1-10 spandex filaments; thirdly, the elasticity percentage control range is from 10 to 20, and different selections can be made according to the use of the product. elasticity value. It is easy to spin yarns of different thicknesses from 25 to 2500 denier, so it is widely used to make elastic knitted fabrics, such as socks, furniture covers, ski suits, sportswear, medical fabrics, belts, military equipment, elastic parts of space suits, etc. . As people put forward new requirements for fabrics, such as light weight, comfortable fit, soft texture, etc., low-denier spandex fabrics account for an increasing proportion of synthetic fiber fabrics.

There are also useful spandex naked yarns and twisted yarns made by combining spandex and other fibers and twisting them. They are mainly used in various warp knitting, weft knitting fabrics, woven fabrics and elastic fabrics. Since DUPONT introduced Spandex for commercial use in 1958 and registered the trademark (LYCRA), which is transliterated in the market as [Lycra], many people have used "Lycra" as the name of Spandex. Later, they were produced all over the world, such as "VYRENE" from U.S. RUBBERCO., "ESPA" from TOYOBO of Japan, and BAYER, A.G., W.GERMANY of Germany. "DORLASTAN" from COURTAULDS, UK, "SPANZELLE" from UK, "ESTANE" from (B.F.GOODRICHCHEMICAL CO., LTD), "FUJIBO" from Japan's Fujibo, "TORAY-DUPONT" ??from DUPONT and Japan's Toray ", "CLEARSPAN" and "GLOSPAN" from the United States (GLOBEMANUFACTURING CO.), "ACELAN" from South Korea's TAE-KWANG, "TEXLON" from TONGKOOK, "TOPLON" and "CREORA" from HYOSUNG Hyosung "It's the largest in the world. Japan's Asahi Kasei's "ROICA", and then Asahi Kasei cooperated with Taiwan's Formosa Plastics Group in early 1999 to establish the "FORMOSAASAHI" company, referred to as "FAS", Japan's Nisshinbo's "MOBILON" also Added a production line to produce TOWNSPAN Donghua silk in Taiwan, and Taiwan invested in Xue Hengxing's "SHEIFLEX" (雪飞丝), while mainland China also has Yantai's "Newstar" and Lianyungang's "Aoshen". "TOYOBO" is produced with Toyobo's equipment and technology, and Guangdong Heshan Spandex Factory was put into operation in 1996. Fujian Changle, Nantong Haimen, and Shandong Zibo also began to produce spandex. China's DUPONT cooperates with Huayuan in Shanghai to produce, and Zhejiang Huafeng's " Millennium brand spandex was also put into production in 2000. In addition, DUPONT also cooperates with other factories (but DUPONT is not involved in production matters) and sells it under the "ELASPAN" brand. All over the world are investing in or expanding the production of spandex, making the elastic fiber market booming. [2] China's DUPONT is produced in cooperation with Huayuan in Shanghai, and Zhejiang Huafeng's "Millennium" brand spandex was also put into production in 2000. In 2004, Zhejiang Hualai Spandex, which adopted the world's most advanced Japanese "Nisshinbo" spandex production technology, was completed and put into production. 7 Editorial Summary of Production Methods Spandex fiber has overcome quality defects such as stress, strain performance, count range and moldability of rubber yarn. At that time, DUPONT was the first to adopt dry spinning production. Today, there are roughly four production methods. Type: Dry spinning (DRY SPINNING): A method in which the solution solidifies into silk due to the volatilization of the solvent under hot air flow. Production process: solution (passed)----spinning pump (filtration)----drying box (100°C hot air blows through to volatilize the solution)----spinning----winding forming spinning speed : From 200 to 800M/min Spinning temperature: 200 to 230°C Fiber fineness: 22.2 to 1244dtex Used by: DUPONT, Bayer, Toyobo Characteristics: Large process pollution, complex process, high cost. Melt spinning (MELT-SPINNING): A method in which a polymer is heated above the melting point to form a melt and form filaments. Production process: Polymer is polymerized without solvent----granulation----slicing at constant temperature----cleaning and impurity removal----drying----dehydration----entering screw press The solution is made into a solution - extruded through a spinneret - cooled through a cold box - rolled into shape.

Spinning speed: from 600 to 1600M/min. Spinning temperature: 160 to 220°C. Fiber fineness: 9 to 1100dtex. Used by: Zhongfang, Bayer, Nisshinbo. Characteristics: short process, low cost, and less pollution. Wet spinning ( WET-SPINNING): A method in which the raw liquid is solidified into silk through double diffusion in the coagulation bath. Production process: Raw solution----Spinning pump (filtration)----Enter warm water (below 90℃) from the spinneret----Regeneration tank coagulation bath----Remove solvent----Filament ribbon Washing----drying----rolling and forming. Spinning speed: from 50 to 150M/min. Spinning temperature: below 90°C. Warm water fiber fineness: 44 to 440dtex. Adopt: Japan Fujibo. Characteristics: This method produces a large amount of pollution, slow spinning speed and high cost. The chemical reaction method is a method in which a polymer solution is chemically reacted with a chain extender and solidified into filaments. Production process: solution----pass through spinneret to coagulating liquid----add chain extender (chemical reaction)----winding and forming----hardening---processed into mesh fibers. Spinning speed: from 50 to 150M/min Fiber fineness: 44 to 80dtex Used by: American Universal Characteristics: The production process of this method is highly polluting and costly. 8 Form Editor: There are also different brightness forms in Spandex production, usually: (Take DUPONT as an example) Transparent (CLEAR-LUSTER): The surface fibers are smoother, so the reflection becomes transparent, the friction rate is low, and the evenness is poor. , the coloring is also poor, suitable for the production of short fiber materials, and is mostly used in warp fabrics. DULL-LUSTER: It is basically white, with uneven fiber surface, large friction surface, and good coloring effect. It is suitable for long-fiber production and is used for thick roots, such as bust products and accessories. Translucent (BRIGHT-LUSTER): Titanium dioxide and anti-slip agent are added to make it more resistant to chemical agents. It is often used in swimming suits because it has anti-chlorine function. Matt color (MATT- LUSTER): It is between natural white and translucent. It is matte white and suitable for knitting. Spandex has different uses and various product forms, mainly divided into three types: bare yarn, core-spun yarn, covered or twisted yarn. Each different combination corresponds to a different purpose. Bare yarn: It is 100 spandex yarn. Bare yarn is generally not used directly on fabrics. Most of them are produced together with rival materials and require special equipment for production. Knitwear is the most commonly used, such as swimsuits, sportswear, etc., generally 22-78Dtex. Core spun yarn uses bare yarn as the core and other materials as yarn spun from the outer sheath, referred to as CSY. For example, if the cotton core is wrapped, the stretched bare yarn is usually inserted into the spinning wheel of the ring-spinning machine. The elongation of the bare yarn wrapped with the core-spun yarn must be adjusted appropriately, and its expansion rate is suppressed to 2 to 3 times. Today, core-spun yarns are divided into hard-core yarns and soft-core yarns. The rival materials of core-spun yarns include cotton, polyester, polyester, etc. It is widely used in fabrics, knitwear, bandages, socks, underwear, and jeans, generally 22-235Dtex.