COMPRESSED-GAS-INDUCED PLASTICIZATION OF POLYMERS

The glass transition in polystyrene-ethylene at pressures up to 78 atm has been studied using a Tian-Calvet heat-flow calorimeter. The glass transition temperature T-g decreases with an increase in ethylene pressure, the largest depression being 67 degrees C at 78 atm. The plasticization effect of ethylene is found to be almost the same as that of CO2, and is predicted well by the statistical thermodynamical formulation of the glass transition in polymer-diluent systems. The plasticization of amorphous poly(aryl ether ether ketone), PEEK, with CO2 at 100 degrees C and 100 atm results in induction of about 17% crystallinity in a high molecular weight sample. Overall crystallinity values as high as 44% are observed in the case of a low molecular weight PEEK sample.