Mechanical measurement of the plasticization of polymers by high-pressure carbon dioxide

A linear variable displacement transducer has been used to measure (lie central deflection of 2-3 mm thick polymer samples undergoing three-point bending while exposed to CO2 at pressures of tip to 120 bar. Significant reductions in the bending onset temperatures were observed on the application of CO2, for polycarbonate, polystyrene, and poly(methyl methacrylate) of typically 20-40 K over the range of pressures applied. Initial onset temperatures correlated reasonably well with literature values for glass transition temperatures, but complete softening of the sample required further time for CO2 to diffuse into the samples.