Description of elastic fiber characteristics by different standards

Classification of elastic fibers
According to the difference in elastic mechanism, elastic fibers can be divided into intrinsic elastic fibers inlaid in soft and hard segments, such as spandex, rubber yarn, thermoplastic polyester elastomer; and morphological elastic fibers, such as through the subsequent mechanical processing due to their shrinking properties The difference is obtained by the bicomponent composite fibers of the crimped structure.

According to the elastic size, it can be divided into high elastic yarn (elastic elongation 400%~800%), medium elastic yarn (elastic elongation 150%~390%), microelastic yarn (elastic elongation 20%~150) %) and low elastic yarn (elastic elongation is less than 20%).
Several elastic fibers
There are many types of elastic fibers on the market, which can be divided into: spandex elastic fibers (PU), polyether ester elastic fibers, polyolefin elastic fibers (represented by DOW XLA fibers), PTT fibers, and two-component composites Crimped fibers (PET/PTT represented by T400), hard elastic fibers, etc.
At present, the most successful commercial elastic fiber is spandex, which is widely used in various plants in the form of spandex core-spun yarn; polyolefin elastic fiber (XLA) is particularly suitable for wool fabrics because it does not require heat setting; PET/PTT double The component fibers have received extensive attention because they can be directly applied without coating, have excellent chemical stability, and have the irreplaceable advantages of the first two types of composite fibers.
Polyurethane fiber (spandex)
Spandex fiber is a polyurethane type structure, which is the earliest developed elastic fiber with the most extensive application and the most mature production technology. It has high elongation, low elastic modulus and high elastic recovery rate. The elongation of spandex can reach 400%~800%, and the recovery rate of 500% production is as high as 95%~99%. Spandex also has excellent chemical and thermal stability. Spandex has good acid and alkali resistance, sweat resistance, seawater resistance, dry cleaning resistance, and abrasion resistance. But spandex needs to be covered before it can be used, and it has the disadvantages of not being resistant to chlorine bleach and easy to relax.
Generally, as long as 2%~10% spandex is added, the underwear can be soft and close-fitting, comfortable and beautiful, and the sportswear can be soft and soft, and it can move freely. It is a fashion and casual pants with good drape, shape retention and fashionability.

Polyetherester elastic fiber
Polyetherester elastic fiber is an elastic fiber made by melt spinning of polyester and polyether copolymer, which was first produced by Teijin Corporation in 1990. Polyetherester elastic fibers are similar to polyurethane elastic fibers in structure, and also have "segment" structural characteristics. The "soft" segments are mainly polyether segments, which have good flexibility and long chains, which are easy to elongate and deform; the "hard" segments are polyester segments, which are relatively stiff, easy to crystallize, and have short chains. When deformed by force, it acts as a node, giving elastic recovery performance, and determining the strength and heat resistance of the fiber.
Polyetherester elastic fiber not only has high strength, but also good elasticity. When stretched by 50%, the elasticity of medium-strength elastic fiber is already equivalent to spandex, and the melting point is also high. It can be blended with PET fiber at 120~130 ℃ Dyeing, so polyester fibers can also be processed into elastic textiles. In addition, they have excellent light resistance, chlorine bleach resistance, acid and alkali resistance, etc. are better than ordinary spandex. Due to the 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 more promising fiber.
Polyolefin Elastic Fiber (XLA)
XLA fiber is a polyolefin fiber launched by the American Dow company. The average crystallinity of the fiber is 14%, the elongation at break reaches 500%, it can generate recovery, and can withstand 220 ℃ high temperature, chlorine bleach resistance and strong acid and alkali, etc. It is attacked by chemicals and has strong resistance to ultraviolet degradation.
After being washed, bleached, dyed, coated and bonded, the inherent elasticity is basically unaffected. At the same time, because the force required to stretch the fabric of XLA fiber is smaller than most other elastic fabrics, the contraction is more natural and comfortable, and it is suitable for infants and children's clothing.
In addition, because the main component of XLA is a recyclable polyolefin, it will not be suitable for spinning volatile organic compounds in the textile process, does not contain heavy metals, and will not hinder the recycling of clothing.
Composite elastic fiber (T400 fiber)
ConTEX (ST 100 composite elastic fiber, market collectively referred to as T400 elastic fiber) is a two-component new composite elastic fiber that uses DuPont Sorona as the main raw material and is made with ordinary PET through an advanced composite spinning process; it has a natural permanent spiral Curling and excellent bulkiness, elasticity, elastic recovery rate, color fastness and particularly soft feel, it can be woven alone or interwoven with cotton, viscose, polyester, nylon, etc., forming a variety of types style.
It not only solves the problems that traditional spandex yarn is not easy to dye, excess elasticity, complex weaving, unstable fabric size, and easy aging during use. It can also be woven directly on air jet, water spray, arrow shaft loom, not like spandex. In that case, the covering yarn must be made before weaving, which reduces the cost of yarn and improves the uniformity of product quality.
Hard elastic fiber
The above-mentioned elastic fibers are all soft elastic fibers and undergo large deformation and recovery under low stress. From a thermodynamic point of view, the elasticity comes from the degree of freedom (or chaos) of the molecular chain, that is, the change of the 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), polyethylene (PE) and other fibers, although not easy to deform under low stress (because they have a higher modulus), but at a higher Under stress, especially at lower temperatures, it also has better elasticity, so this type of fiber is called a hard elastic fiber.
The deformation and recovery of hard elastic fibers are significantly different from those of elastic fibers. For example, the rigid elastic PP fiber is stretched immediately after the second recovery, its modulus and strength will drop a lot, but if it is left for a period of time after the stress is removed, or the temperature is increased to relax it sufficiently, the second stretching is performed. Extension, the deformation recovery is basically close to the first curve. This is because when the hard elastic fibers are stretched and recovered, not only the stretching and retraction deformation of the long chain segments of the aforementioned soft elastic fibers curling molecules, but also some micropore structure changes during the stretching process, their The chip network structure has also changed. Only after these structural changes are gradually restored can they return to their original state, so they deform and recover under higher pressure, called hard elastic fibers.
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.
The use of elastic fibers
Clothing containing elastic fibers fits the body shape, displays beautiful natural curves and increases beauty; it does not cause comfort to the human body's activities and caters to the human body's requirements for comfort. Therefore, more and more people apply elastic fibers to various fabrics, such as swimwear, ski suits, casual sweatshirts, underwear, tights, stockings, etc.
Among the 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 the wearing comfort and fluffy warmth of clothing. Therefore, it is in the textile industry in China and the world. China occupies a stable position, and the flexibility given to textile fabrics has become an inevitable development trend for wearing textiles.