Amorphous phase separation in polypropylene block copolymers as revealed by thermostimulated depolarization measurements. II. Thermal sampling analysis

We achieved a thermal sampling scanning of the β-relaxation region of polypropylene (PP) block copolymers together with the β process of isotactic polypropylene, high-density polyethylene, propylene-ethylene rubber, and part of the PP bloc copolymer soluble in xylene and insoluble in ether. The comparison of activation parameters determined in the above relaxations confirmed the hypotheses drawn from complex spectra studies concerning phase separation and the origin of dielectric relaxations in PP block copolymers. One of the dielectric relaxations of the part of PP block copolymer soluble in xylene and insoluble in ether could be attributed to polypropylene blocks. We related the preexponential factor of the relaxation time to chain environment. Then we discussed the compensation phenomenon in distributed relaxations and the relation between the compensation temperature and variation of thermal expansion coefficient through the compensating relaxation.