Melt Crystallization Behavior and Spherulitic Morphology of Poly(Trimethylene Terephthalate)/Poly(Propylene Glycol) Copolymers with Different Poly(Propylene Glycol) Molecular Weights

Poly(trimethylene terephthalate)/poly(propylene glycol) (PTT/PPG) copolymers with different PPG molecular weights (400–4,000 g /mol) were successfully synthesized and characterized. Double melting endotherms during isothermal melt crystallization were observed by differential scanning calorimetry. Middle-temperature melting endotherms in all copolymers were stronger than that in PTT homopolymer and became smaller with the increasing PPG molecular weight. Nonisothermal crystallization kinetics of all samples were analyzed by Ozawa and Mo models. Polarized optical microscopy micrographs revealed that ring-banded spherulitic morphology was relatively easier to be observed in copolymers with higher PPG molecular weight at lower crystallization temperature, and PPG molecular weight nearly had no influence on the band spacing.