Structure and property relationships in PET blends

Blends of poly(ethylene terephthalate) (PET) and polycarbonate (PC) have been prepared by twin-screw extruder with and without added a transesterification catalyst - lanthanum acetylacetonate hydrate. The blends without added catalyst are completely immiscible over the study range while the blends with added catalyst show partial miscibility. The mechanical properties are slightly improved in the latter blends. Studies were made on the crystallization and melting behaviour of PET and both of blends. It has been found that the crystallisation was inhibited in the presence of PC, particularly in the blends with added catalyst for which the equilibrium m.pt. showed considerable depression greater than the other samples. Multiple melting endotherms are due to dual lamellar thickness distributions and recrystallisation during heating. Miscibility, melting and crystallisation were also studied by MTDSC which proved to be a powerful tool separating reversing and non-reversing events. The crystallinities of PET and blends were measured using the First Law method and consistent with those measured by density and WAXD procedures. Both blends annealed at higher temperature the thermal properties, phase structure and transesterification have been investigated as a function of time. Kinetics parameters were also determined