Study on co[poly(butylene terephthalate-p-oxybenzoate)] thermotropic copolyester. II. Thermal behavior and crystalline morphology

The POB/PBT copolyesters, designated B28, B46, B64, and B82, were prepared from p-acetoxybenzoic acid (PAB) and poly(butylene terephthalate) (PBT). Th e polymeric products obtained were then ground and subjected to solid-state polymerization under vaccum for 4 h. The melting and crystallization behav iors of these copolyesters haven been studied by differential scanning calo rimetry (DSC). In the DSC scan of the POB-rich composition, the endothermic peak shows obscurely, and enthalpy of fussion becomes small due to the cha nge in the crystalline morphology from isotropic to anisotropic. In general , the melting point of the copolyester is increased by the solid-state poly merization reaction. Also, thermogravimetric analysis (TGA) were performed with these samples obtained. It was found that the decomposition temperatur e (T-d) is increased as the POB content is increased. Effects of compositio n and solid-state polymerization on the decomposition temperature of copoly esters are also discussed. The crystalline morphology of copolyester was in vestigated with a Zeiss polarized optical microscope. It was found that the POB/PET copolyesters with 60 mol % POB was shown to be highly anisotropic. (C) 2000 John Wiley & Sons, Inc.