A comprehensive theoretical framework for the sub and supercritical sorption and transport of CO2 in polymers

The sorption and transport of CO2 in two polymers, Matrimid and PDMS, were modelled using data available across the critical region, at various temperatures and up to 18 MPa. The experimental trends show a complex behavior that is affected by the transition from gas-like to liquid-like density of CO2, as well as by the sorption induced glass transition of the polymer. The Non Equilibrium Thermodynamics (NET-GP) approach for the solubility, coupled to its complementary tool for the permeability, the Standard Transport Model (STM), allows to represent thoroughly the complexity of CO2 sorption and permeation in this operative range with a selfconsistent set of parameters. Furthermore, the model offers a deep insight in the swelling induced by CO2 in the different states of the polymers, and allows to decouple the kinetic and thermodynamic contributions to the transport phenomena in a meaningful way. This work takes a step forward in the understanding and simulation of the complex interactions between high pressure, supercritical CO2 and industrially relevant polymeric materials.