Spandex (PU) fiber
Spandex fiber (referred to as PU fiber), belongs to polyurethane structure, has high elongation, low elastic modulus and high elastic recovery rate, in addition, spandex also has excellent chemical stability and thermal stability, it is more resistant to chemical degradation than latex wire, softening temperature is about 200 °C above. Spandex fibers are resistant to perspiration, seawater, and a variety of dry cleaners and most sunscreens. Long-term exposure to sunlight or chlorine bleach can also bleed, but the degree of fading varies greatly with the type of spandex. Garments made of spandex-containing fabrics have good shape retention, dimensional stability, no sense of oppression, and comfortable wearing. Usually as long as 2% ~ 10% spandex is added, the underwear can be soft and close, comfortable and beautiful, so that the sportswear fits softly, free movement, and makes fashion and casual wear have good drape, shape retention and fashion. Therefore, spandex is an indispensable fiber for the development of highly elastic textiles. 

Polypropylene terephthalate (PTT) fiber
Polypropylene terephthalate fiber (referred to as PTT fiber) is a new product in the polyester family, which belongs to polyester fiber and is a family of commonly used polyester PET. PTT fiber has the characteristics of polyester and nylon, soft feeling, good elastic recovery, easy to dye under normal pressure, bright color, good dimensional stability of the fabric, very suitable for the field of clothing. PTT fiber can be blended, twisted and interwoven with natural fibers such as wool and cotton or synthetic fibers, and can be applied to woven fabrics and knitwear. In addition, PTT fiber can also be used in industrial fabrics and other fields, such as the manufacture of carpets, decorations, webbing, etc. PTT fiber has the advantages of spandex elastic fabric, and the price is lower than spandex elastic fabric, which is a promising new fiber.

Elastane T-400
T-400 fiber is a new type of elastic fiber product developed by DuPont for spandex fiber in textile applications. T-400 does not belong to the spandex family, but is a parallel composite fiber made of two polymers, PTT and PET, which have different shrinkage rates. It solves many problems such as spandex is not easy to dye, excess elasticity, complex weaving, unstable fabric size and spandex aging during use.

The fabric it makes has the following characteristics: (1) Elasticity is easy, comfortable and durable; (2) The fabric is soft, structured and has good drape; (3) The cloth surface is flat and has good wrinkle resistance; (4) Moisture absorption and fast drying, smooth feeling; (5) Good dimensional stability and easy handling.

T-400 can be blended with natural fibers and man-made fibers to improve strength and softness, the appearance of the blended fabric is clean and silky, the garment contour is clear, the clothes can still maintain a good shape after repeated washing, the fabric color fastness is good, it is not easy to fade, and it still looks like new clothes after long-term wear. At present, T-400 is widely used in pants, denim, sportswear, high-end women's clothing and other fields because of its excellent performance.