An in situ study of plasticization of polymers by high-pressure gases

A high-pressure differential scanning calorimetric technique is described for studying polymer plasticization by compressed gases at pressures to 100 atm. The in situ measurements avoid problems due to gas desorption encountered with conventional DSCs, thus providing an accurate way to determine the change in glass transition temperature, T-g, with pressure, p. The entire Tg-p curve can be established in less than 2 days. The glass transition was observed as a sharp step in the case of 100-200-mu m thin samples, whereas thicker samples gave a broad transition; highly reproducible results were obtained for the thin samples. For PS-CO2, the measured T(g)s under various pressures were found to be in good agreement with literature values. Results for the systems PS-HFC134a, PVC-CO2, and PC-CO2 are also reported. (C) 1998 John Wiley & Sons, Inc.