A study of segment movement in polybutylene terephthalate/polycarbonate blends using thermally stimulated depolarization

The segment relaxation behaviour of finely dispersed polybutylenterephthala te (PB-T)/polycarbonate (PC) blends mixed by twin in screw extruder, was in vestigated in detail by the method of thermal stimulated depolarisation (TS D) and thermal stimulated depolarisation with thermal sampling (TSD-TS). Th e resulting temperature dependencies and distribution functions of activati on energies of the beginning of segment motions, and the character of the i nfluence of annealing on the relaxation behaviour of the mixed phases. were discussed in considering the phase morphology, the crystalline structure a nd the crystallisation behaviour. The relationships are good to explain in the frame of the hypothesis on the spontaneous fractionation of polymers in blends and the decomposition of the cooperative restoring regions of segme nts, caused by the interactions with the different molecules. In finely dis persed, less than or equal to 0.5 mu m small particles of the PET rich phas e. a degeneration of the cooperative alpha-segment relaxation in a non-coop erative beta-segment was detected by the solution of PC molecules in PET. T he rho-peak of the PC rich matrix which is caused by the T-11 transition is strongly depressed in the PBT/PC blend with 80% PC, correlating with a mar ked increase of the heat resistance. (C) 1998 Elsevier Science Ltd. All rig hts reserved.