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

Poly(butylene terephthalate)(PBT), a sort of polymer with good performance, and its copolyesters which are prepared from the PBT have attracted a wide spread attention and become a focal point of research in recent years.Fumaric acid with rigid double bonds is an unsaturated dicarboxylic acid. In this article, the poly(butylene terephthalate-co-fumarate) (PBTF) copolymers were synthesized by introducing fumarate segment into PBT chain. The molecular weight distribution, chemical composition, crystallization structure, glass transition temperature of PBT and PBTF were measured and characterized by gel permeation chromatography (GPC),1H-NMR spectrometer, wide-angle X-ray diffraction (WAXD) and differential scanning calorimetry (DSC), respectively.The crystallization kinetics and melting behaviors after crystallization of PBT and PBTF were studied by using differential scanning calorimetry (DSC). The equilibrium melting temperatures for the samples were calculated by Hoffman-Weeks equation. As the results of Avrami equation, these polymers had same Avrami kinetic parameters(n=2.50-2.96), indicating that the addition of fumarate does not affect the nucleation mechanism and growth style of PBT. Crystallization activation energy (ΔE) and nucleation constant (Kg) of PBTF copolymers are higher than that of PBT homopolymer, suggesting that adding fumarate into PBT hinders its crystallization. Their crystallization behaviors under different cooling rate were analyzed by Jeziorny model and Mo model. It was found that Jeziorny model successfully described the initial stage of nonisothermal crystallization process and Mo model can describe the total process.