ISOTHERMAL AND ISOBARIC PVT-MEASUREMENTS OF ATACTIC POLYMERS

It is evidenced that due to the kinetic character of the glass transit ion as a 'freeze in' process, PVT measurements extended over the glass transition range depend not only on the thermal history but also on t he pressure acting during the formation of the polymeric glasses. As a consequence metastable glasses are formed which show during heating o f the glassy polymer through the glass transition range 'volume relaxa tion zones', characterized by a retarded increase or even decrease of the volume. The width of the 'relaxation zone' increases with increasi ng pressure and depends additional on the mode of operation used durin g the PVT measurements. In the same time a pressure induced shift of t he glass temperature to higher temperatures is observed, the shift bei ng the greater the stiffer the polymer, i.e. the higher the glass temp erature of the polymer at atmospheric pressure. Due to the metastable character of polymeric glasses the evaluation of universal equations o f states is thus not ingenious for polymeric glasses, because the dedu ced EOS will be valid only for that given glass characterized by a wel l defined thermal and pressure history. Additionally the EOS is influe nced by the unknown time dependent aging and relaxation processes with in polymeric glasses.