Miscibility and thermal properties of melt-mixed poly(trimethylene terephthalate)/amorphous copolyester blends

This work examined the miscibility, crystallization kinetics, and melting behavior of melt-mixed poly(trimethylene terephthalate) (PTT)/poly(ethylene-co-cyclo-hexane 1,4-dimethanol terephthalate) (PETG) blends. Differential scanning calorimetry (DSC) and wide-angle X-ray diffraction techniques were used to approach the goals. The single composition-dependent glass-transition temperatures of the blends and the equilibrium melting temperature (T_m^o) depression of PTT in the blends indicated the miscible characteristic of the blend system at all compositions. T_m^o of pure PTT, determined with a conventional extrapolative method, was 525.8 K. Furthermore, the Flory-Huggins interaction parameter was estimated to be -0.38. The dynamic and isothermal crystallization abilities of PTT were hindered by the incorporation of PETG. A complex melting behavior was observed for pure PTT and its blends. The observed complex melting behavior resulted mainly from the recrystallization and/or reorganization of the originally formed crystals during the heating scans. For the samples crystallized under the same conditions, the degree of recrystallization and/or reorganization declined with increasing PETG contents in the blends. The preliminary results obtained from the DSC experiments suggested that untraceable interchange reactions occurred in the studied blends.