Gas solubility in glassy polymers: predictions from non-equilibrium EoS

Extension of well established EoS for fluid mixtures to the description of thermodynamic properties of nonequilibrium glassy polymeric phases is considered and corresponding calculations for pseudo-equilibrium gas content are performed. Results obtained using three different “tangent hard spheres chain” EoS are discussed and compared with experimetnal data for low-pressure gas solubility in glassy polycarbonate. While the overall result allows to conclude that tools developed herein may be confidently used for pure predictions of gas and vapor solubility in polymeric material below the glass transition temperature, interesting differences among the performance of different models were observed which can be attibuted to the different form of interaction potential considered.

In this work an approach to the description of thermodynamic properties of non-equilibrium glassy phases, already applied to the Lattice Fluid Theory of Sanchez and Lacombe, has been extended to the “tangent hard spheres chain” EoS. The product of this effort is a predictive tool for the pseudo-equilibrium solubility of gases and vapours in glassy polymers. A comparison of predicted values with experimental data reveals the reliability of this tool, at least for the case of a model based on square well interaction potential. That result confirms the validity of the general approach and of the physical picture of glassy state the latter is based on.