INSTABILITY IN THE RUBBERY STATE REVEALED BY D. S. C. OF RHEOMOLDED POLYSTYRENE SAMPLES.

Differential scanning calorimetry (D. S. C. ) results are presented on polystyrene samples which show T//l//,//l as an enhanced peak interfering with the classical T//g endothermal manifestation especially at very short annealing times. This behavior and the influence of annealing on the position of the peaks suggest that the stability of the rubbery state is far from being simple and that the relaxations perceived as transitions at T//g and T//l//,//l probably result from cooperative coupled processes. The enhancement of the thermal characteristics at T//l//,//l in the polystyrene samples is obtained by application during cooling of a new molding process called 'Rheomolding'. This process is briefly described.