Solubility in Glassy Polymers:  Correlations through the Nonequilibrium Lattice Fluid Model

The representation of solubility isotherms of gases and vapors in glassy polymers has been analyzed through the use of a thermodynamic model, nonequilibrium lattice fluid, recently introduced. The possible use of the model as a predictive tool for gas solubility in glassy polymers has been discussed in previous works for the special cases in which the polymer density in pseudo-equilibrium conditions is known from experimental measurements. In this paper, a different use of the model is presented in which the polymer density at different sorption conditions is not known from direct experimental measurements and is thus treated as a correlation parameter, following the typical linear dilation isotherm. The solubility isotherms thus obtained by the model have been compared with several experimental data, obtaining a rather satisfactory representation of the sorption isotherms, through use of two fitting parameters, at most.