CRYSTALLIZATION OF POLY(ETHYLENE-TEREPHTHALATE) POLYCARBONATE BLENDS .1. UNREINFORCED SYSTEMS

The crystallization and transition temperatures of poly(ethylene terep hthalate) (PET) in blends with polycarbonate (PC) is considered using thermal analysis. Additives typically used in commercial polyester ble nds, transesterification inhibitor and antioxidant, are found to enhan ce the crystallization rate of PET. Differential scanning calorimetry (DSC) reveals two glass transition temperatures in PET/PC blends, cons istent with an immiscible blend. Optical microscopy observations are a lso consistent with an immiscible blend. Small shifts observed in the T-g of each component may be due to interactions between the phases. T he degree of crystallinity of PET in PET/PC blends is significantly de pressed for high PC contents. Also, in blends with PC content greater than 60 wt %, two distinct crystallization exotherms are observed in d ynamic crystallization from the melt. The isothermal crystallization k inetics of PET, PET modified with blend additives, and PET in PET/PC b lends have been evaluated using DSC and the data analyzed using the Av rami model. The crystallization of PET in these systems is found to de viate from the Avrami prediction in the later stages of crystallizatio n. Isothermal crystallization data are found to superimpose when plott ed as a function of time divided by crystallization half-time. A weigh ted series Avrami model is found to describe the crystallization of PE T and PET/PC blends during all stages of crystallization. (C) 1996 Joh n Wiley & Sons, Inc.