Studies On The Effects Of Comonomer With Long Alkane Segment On PBT's Crystallization And Melting Behavior

Poly(butylene terephalate) (PBT) is a crystalline thermoplastic polyester with excellent mechanical properties, and its application fields are expanding, such as hot melt adhesive prepared from the copolymer of PBT in the packaging, textile, automobile and other broad application.In this paper, sebacic acid and dodecanoic acid were introduced into PBT, then the poly(butylene terephthalate-co-sebacate) (PBTS) and poly(butylene terephthalate-co-dodecanoate) (PBTD) copolymers were synthesized. The molecular weight distribution, melting point and glass transition temperature of PBT, PBTS and PBTD were tested and characterized.The isothermal crystallization kinetics and melting behaviors after isothermal crystallization of PBT, PBTS and PBTD, and the nonisothermal crystallization kinetics and melting behaviors after nonisothermal crystallization of PBT and PBTS were investigated by differential scanning calorimetry (DSC). The equilibrium melting temperatures of PBT, PBTS and PBTD were determined by Hoffman-Weeks equation. Through analysis of the crystallization kinetic data using the Avrami equation, the Avrami exponent n varies in the range of 2.16-3.68, indicating that the isothermal crystallization follows two-and three-dimensional growth mechanism, and the crystallization rate parameter K showed that the introduction of sebacate enhanced the crystallization of PBT in PBTS. The Avrami equation modified by Jeziorny and the equation deduced by Mo were used to describe the behaviors of the nonisothermal crystallization, respectively. Related equation parameters were obtained by regressing, and discussing the effect of cooling rate on the crystallization rate.