BLENDS OF AMIDE MODIFIED POLYBUTYLENE TEREPHTHALATE AND POLYCARBONATE- PHASE-SEPARATION AND MORPHOLOGY

Blends are made of polycarbonate (PC) and poly(butylene terephthalate) (PBT) or amide modified poly(butylene terephthalate) (PBTA). The blen ds were prepared by melt blending. The blend morphology was studied by transmission electron microscopy. The PC phase was stained with RuO4. The particle sizes in the PC/PBT blends are small (less than 0.5 mu m ) and the particle sizes in the PC/PBTA blends are larger (0.5-5 mu m) The blends were stabilized against transesterification by inactivatio n of the titanate catalyst in the PBT/PBTA with triphenyl phosphite (T PPi). A side effect of TPPi is that it acts as a plasticizer for the P C phase. The results were corrected for this effect. Also studied are the influence of the amide concentration in the PBTA from 0% (PBT) to 25 mol% (PBTA25) and the concentration of PBT(A) in the PC/PBT(A) blen d over the whole composition range on the glass transition temperature (T-g) of the PC phase of the blend. Also studied are the crystallizat ion behaviour as function of PC/PBT(A) composition and the phase separ ation on annealing. The PC/PBT blends were found to be partially misci ble. As a result of this, the T-g of the PC was lowered and the crysta llization of PBT slowed down. The PC/PBTA blends with 20-25 mol% amide s in the PBTA were immiscible. The crystallization rate of the PBTA wa s high, and was not affected by the presence of the PC. The blends wit h PBTA had a higher melting temperature, were faster crystallizing, an d had a higher T-g of the PC phase. (C) 1997 Elsevier Science Ltd.