Solubility of gases and vapors in glassy polymers modelled through non-equilibrium PHSC theory

Well established equation-of-state (EoS) models from Perturbed Hard Sphere Chain Theory have been adopted within the framework of non-equilibrium thermodynamics for glassy polymers (NET-GP) to describe the solubility of small penetrants in glassy polymers. The procedure presented here parallels the one already applied to the Lattice Fluid EoS, obtaining the Non-Equilibrium Lattice Fluid (NELF) model. The solubility is calculated as pseudo-equilibrium solute content in the glassy polymeric phase at fixed temperature and solute fugacity, and is compared to the experimental data. The NE-PHSC model predictions require pure component and binary EoS parameters, together with the value of the glassy polymer density during sorption. Several common glassy polymers, as well as a high free volume fluoropolymer, have been considered to test the model ability to represent the thermodynamic properties of glassy gas–polymer mixtures. A comparison between the performance of two NE-PHSC models, endowed with different expressions for the interaction potential, is also presented, offering interesting conclusions on their accuracy in the representation of the thermodynamic properties of relatively high-density systems.The results obtained in this work show that the NET-GP approach provides a reliable description of the properties of homogeneous glassy mixtures.