Elastic fiber is an essential material in our life.Without it, there would be no silk stockings, no summer bathing suit, no figure-enhancing tights…It can be said that elastic fibers for human body, enjoy the comfort of clothing made an indelible contribution.
The elastic fiber we often see in the composition of clothes is called “spandex”.Although the content is not high, but very important oh.When you shop online, you can check the ingredient label of the clothes and see the spandex, you can generally know that the clothes have a slimming effect, so you can wear a little tight feeling.And the dress that does not have stretch fiber, want to choose and buy commonly a bit looser, cannot too close-fitting, can hinder normal activity otherwise.
But if you think spandex is just spandex, think again.According to the definition given by ASTM of American Society for The Testing of Materials, elastic fiber is repeatedly stretched to at least 2 times of its original length at room temperature, and can be quickly restored to the original length after release of tension. The following 6 kinds of fibers can be called elastic fibers.
Diene elastic fiber (rubber silk)
The elongation of diene elastic fibers, commonly known as rubber or elastic fibers, is generally between 100 %~300 %.The main chemical composition is polyisoprene sulphide, which has good chemical and physical properties such as high temperature resistance, acid and alkali resistance, abrasion resistance, etc. It is widely used in socks, rib cuffs and other knitting industry.
Rubber silk is an early elastic fiber, which is mainly made into coarse yarns, so its use in woven fabrics is very limited.
Polyurethane fibre (spandex)
Polyurethane Elastane is a type of fiber derived from a block copolymer based on polyurethane, known as Spandex in China. Originally marketed as Spandex in the United States, it was renamed Lycra Lycra in America, Neolon in Japan, and Dorlastan in Germany.
Its elasticity derives from the molecular structure of a block copolymer network consisting of “soft” and “hard” chain segments.With the different block copolymers, the spinning process of the fiber is different, and the elasticity and dyeing and finishing properties of the fiber are also different after forming different “segment” network structure.
Polyether ester elastic fiber
Polyether ester elastomer (POLYEther) is a elastomer made from polyester and polyether copolymer via melt spinning. It was first produced by Dairen In 1990.Polyether ester elastic fiber not only has high strength, but also good elasticity. At the elongation of 50%, the elasticity of medium strength elastic fiber is equal to that of spandex, and the melting point is also high. When blended with PET fiber, polyester fiber can be dyed at 120℃~130 ℃, so polyester fiber can also be processed into elastic textiles.In addition, they have good light resistance, chlorine resistance, acid and alkaline resistance are better than ordinary spandex.Due to its good acid and alkaline resistance, the fabric made of it and polyester can also be processed with alkali deweighting 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 fiber with a promising future.
Polyolefin elastic fiber
Polyolefin elastomers are prepared from polyene thermoplastic elastomers by melt spinning.DOW Chemical launched XLA in 2002 as the first commercial polyolefin elastomer, made from vinyl octene copolymers (POE) catalyzed in situ by metallocene catalysts via melt spinning.It has good elasticity, 500% breaking elongation, can withstand 220℃ high temperature, chlorine bleaching and strong acid and alkali treatment, and has a strong anti-ultraviolet degradation performance.Its production technology is simple, the raw material price is lower than that of spandex, and the production process produces little pollution and is easy to recycle.
Polyolefin elastic fibers have been widely used in recent years because of their excellent properties.
Composite elastic fibre
CONTEX CONTEX (ST 100 composite elastic fiber, collectively referred to as T400 elastic fiber in the market) is a new two-component composite elastic fiber made by advanced composite spinning technology with dupont Sorona as the main raw material and common PET.With natural permanent spiral curl and excellent swelling, elasticity, elastic recovery rate, color fastness and special soft handle, can be woven alone, but also with cotton, viscidity, polyester, polyamide fiber interweave, form a variety of types of style.
It not only solved the traditional fiber silk is not easy to dyeing, elastic excess, weaving complex, fabrics, size is not stable, and easy ageing, and many other problems in use process, and can be directly on the jet, water jet, shaft loom weaving, don’t must be made as spandex coated before computer weaving yarn, reduce the cost of yarn, improve the quality of the product homogeneity.
Hard elastic fibre
The elastic fibers mentioned above are soft elastic fibers, which can deform and recover greatly under low stress.From the perspective of thermodynamics, the elasticity comes from the degree of freedom (or chaos) of the molecular chain, namely the change of entropy of the system, so the crystallinity of the above fibers is very low.But under the condition of special processing of some fibers, such as polypropylene (PP), polyethylene (PE), such as fiber, while under low stress is not easy to deformation (because they have higher modulus), but under high stress, especially at low temperature, also has good flexibility, so this kind of fiber is called hard elastic fibers.
The deformation and recovery of hard elastic fibers are obviously different from those of elastic fibers.For example, the hard elastic PP fiber will be stretched for a second time immediately after the recovery after stretching, and its modulus and strength will decrease a lot. However, if it is placed for a period of time after the stress is removed, or it is stretched for a second time after the temperature is raised to make it fully relaxed, its deformation recovery will be basically close to the curve of the first time.This is because when the hard elastic fiber is stretched and recovered, not only the long chain segment of the above-mentioned soft elastic fiber is stretched and retracted, but also some micropore structure changes during the stretching process, and their chip network structure also changes.Only after the gradual recovery of these structural changes can they return to the original state, so that they can be deformed under higher pressure, known as 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.