Modified Dry Glass Reference Perturbation Theory for Linear Sorption in Dense Glassy Polymers

Multicomponent solubility predictions in glassy polymers are of profound importance in the modeling of membrane-based separations of complex mixtures. The dry glass reference perturbation theory (DGRPT) closure of the nonequilibrium thermodynamics of glassy polymers (NETGP) has been shown to provide an accurate methodology to predict these solubilities. In this work, we study the application of DGRPT to gas sorption in dense polymers with linear pressure dependence. It is shown that DGRPT loses accuracy in these cases. A simple modification to DGRPT is introduced, which allows for the accurate representation of linear isotherms.