Modelling sorption induced volume dilation in glassy polymers within the NET-GP approach

Two distinct approaches proposed in the literature for the description of sorption induced volume dilation in glassy polymers are discussed and compared with respect to their predictive capability. Both Non-Equilibrium Restrained Swelling model (NE-RS) and Dry Glass Reference Perturbation Theory (DGRPT) have been proposed to address this problem within the framework of Non-Equilibrium Theory for Glassy Polymers (NET-GP). Both qualitative and quantitative characteristics of results from the two models are considered and corresponding predictions are compared with experimental data available in the literature, for the case of sorption of gas or vapor penetrants in conventional glassy polymers. Conclusions are drawn about the crucial role of correct description of induced volume swelling in prediction of high-pressure gas solubility in glassy polymers through NET-GP approach, as well as about different abilities and limits of the two models so far proposed to this aim.