Pure and mixed gas sorption of carbon dioxide and ethylene in poly(methyl methacrylate)

Abstract

The sorption of CO 2, C 2 H 4 and mixtures of these gases in poly(methyl methacrylate) at 35°C has been characterized at pressures up to 6.5 atm. The pure gas sorption isotherms exhibit significant concave curvature to the pressure axis and are described well by the dual mode sorption model. The mixed gas sorption data indicate that significant decrements in the solubility of each component in the mixture occur relative to the pure component case at equivalent partial pressures. This phenomenon is predicted accurately by the dual mode sorption model, which accounts for competition between mixture components for sorption in the polymer. The model requires only pure component sorption parameters to describe the mixture behaviour over the full range of composition. The mixture data reveal that the model should be formulated in terms of the gas phase fugacity rather than the partial pressures of the gases at high pressures where non-ideal gas mixture behavior may occur. Deviations between mixed gas sorption data and model predictions based on pure component dual mode parameters are small (± 2.1%) and probably negligible for most purposes for the pressure range studied.