PBT fiber is polykudzu elastic fiber, the scientific name is polybutylene terephthalate, in Japan and the United States in the early 80s of the 20th century, socks were only produced in large quantities), used in the development and application of textile products. The melting point of PBT fiber is lower than that of polyester and nylon, which is 21 °C, and the relative density is higher than that of nylon (1.14) at 1.35 and lower than that of polyester, and the stability of light and size is better. The crystallinity is also particularly high, its POY yarn strength is lower than that of nylon (3.9cN/dtex, 4gf/dtex) and higher than that of polyester (2.0cN/dtex, 2.0gf/dtex) of 2.45cN/dtex11, 5gf/dtex), while DTY yarn is 2.8cN/dtex (2.9gf/dtex), and its POY (high-speed spinning, pre-oriented) yarn elongation is l00% (nylon is 70% - 75%). When 0.02cN/dtex (18mgf/dtex) is applied to 75dtex/34f filament, its bulkiness is 81010, the elastic recovery rate is 59%, the elasticity is 2.74cN (2.8gf), and the curl is 44%. It is superior to nylon and polyester knitted fabrics in terms of curl, elasticity, and recovery, but it is less abrasion resistant. It can be boiled and dyed, with good color fastness and good dimensional stability in wet state.
Fabrics made of PBT fibers can be used to make yukata, women's underwear, pantyhose, stretch jeans and sportswear, carpets and various decorative rugs.