PRESSURE INFLUENCE ON THE GLASS-TRANSITION OF POLYMERS AND POLYMER BLENDS

p-V-T measurements have been carried out on a broad series of polymers and polymer blends. The effect of pressure on the glass transition te mperature, T(g), and on related properties - increments of the coeffic ients of expansion, DELTAalpha, and compressibility, DELTAkappa, at T( g) - has been evaluated critically. The results are discussed in' term s of the free volume, the order parameter, and the statistical mechani cal theory. It is concluded that neither the simple 'free volume' theo ry, nor the order parameter theory in the one order assumption predict correctly the observed behaviour. A possible explanation of the pheno mena observed is offered assuming an expansion of the free volume, whi ch is independent of the nature of the polymer. For the blends binary contacts between the components are discussed, with respect to interac tion energy and to conformational rearrangements.