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 (Tmo) depression of PTT in the blends indicated the miscible characteristic of the blend system at all compositions. Tmo 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.