Dilatometric studies of isotactic polypropylene with different morphology before and after thermal degradation in air

Summary Glass transition phenomenon in isotactic polypropylene has been studied in this paper basicly on dilatometric studies. New suggestions are made for explaining the occurrence of twoT _g values with their characteristic dependence on the degree of crystallinity of the samples having a different morphological structure. The effects produced by thermooxidation are discussed. T _g calledT _g1 is considered as the true glass transition temperature in the amorphous phase of IPP whereasTg2 is melting of a smectic phase in IPP,T _g2 >T _g1.Author thanks Prof. M. Kryszewski for useful discussion.