PBT and PET belong to the same polyester polymer. Compared with PET, the melting point of PBT macromolecules is lower due to the longer flexible part on the chain link, but the flexibility and elasticity of the macromolecular chain are improved. If the elastic recovery rate of PBT is 100%, nylon (PA) is only 70%; PET is 55%. In addition, compared with PET, PBT dyeing can be boiled without the dye carrier, and compared with nylon, the shortcomings of nylon that are easy to yellow and chlorine resistant are improved.
PBT macromolecular chain has an ester group and benzene ring structure, which is what gives it excellent elastic recovery and strength, as well as dyefastness, lightfastness, heat resistance, chemical resistance and dimensional stability similar to polyester.
Because the length of PBT molecular links and Young's modulus are similar to those of PA6, the fibers are easy to be micro-curled, and the molecules can move more freely when curled. This results in its textured yarn and its fabrics showing excellent compressive and tensile elasticity.
structure of PBT fibers, there are crystalline variants, color elongation heat treatment, molecular chains become elongated β crystalline variants, color loose heat treatment, and molecular chains become α crystalline variants. Since this variant is also prone to production at room temperature, the heat setting properties of PBT fibers are not very good, and the dimensional stability of the braid is inferior to that of PET fibers.
The strength of PBT fiber is lower than that of PET fiber and PA fiber, and the Young's modulus (about 300kg/mm2) is similar to that of PA6 fiber, and the elongation elastic recovery rate is 99% at 3% elongation and 80% at 10%, which is the same as that of PA6 fiber. The curling characteristics of deformed are better than those of PET and PA6, and the curl is smaller than that of PA6, and the elasticity is better.
PBT fiber has easy dyeability, and the color absorption rate is about 75% when disperse dyes are used, which is better than that of PET fiber, but the properties of fastness, light yellowing, and wetting pollution are not as good as those of PET fiber.