STUDIES OF MISCIBILITY, TRANSESTERIFICATION AND CRYSTALLIZATION IN BLENDS OF POLY(ETHYLENE-TEREPHTHALATE) AND POLY(ETHYLENE-2,6-NAPHTHALENE DICARBOXYLATE)

Blends of poly(ethylene terephthalate) (PET) and poly(ethylene-2,6-naphthalene dicarboxylate) (PEN) were obtained by coprecipitation from solution followed by melt-pressing for different times t(m) and quenching in iced water. When the melt-pressing time was 0.2 and 0.5 min, two glass transition (DMA), indica were observed by means of dynamic mechanical analysis temperatures T-g were observed by means of dynamic mechanical analysis (DMA), indicating that there are two phases present, a PEN-rich phase and a PET-rich phase. The differential scanning calorimetry (DSC) curves show two crystallization peaks and two melting peaks which, according to wide-angle xray scattering (WAXS) measurements, can be attributed to PET and PEN, respectively. In the case of t(m) = 2 min or longer, a single value of T-g and thus a single phase is found to exist. For t(m) = 10 min and 45 min no crystallization and melting at all is observed during heating with 10 degrees C/min, indicating that a copolyester of PET and PEN has been formed by transesterification during melt-pressing. Time-resolved WAXS measurements during isothermal crystallization show that, in the blend, the half-time of crystallization of PET is different from that of PEN, and not the same as that which is found in the pure polymer.