Abstract
The transport of gases and solvents in polymeric membranes is an important phenomenon with many technical applications, such
as the mixture separation using polymeric membranes, the polymeric membrane preparation, the polymer devolatilization and the
selection of appropriate polymeric membranes for a certain process. In most membrane separation operations and manufacturing,
equilibrium and diffusion data are required.
Useful information on equilibrium and diffusion can be obtained from the solvent sorption study. The phase equilibrium for
polymer solvent systems can be successfully described using the correlative model or the predictive model based on the UNIFAC
group contribution such as the UNIFAC-FV. The diffusion coefficients in polymers depend strongly on temperature and their
composition. First researches concerning the diffusion in polymers were reported by different studies. The free-volume theory is
the most widely used theory for correlating and predicting the diffusion in polymer-solvent systems. It has been extended to
predict the diffusion in ternary polymer-solvent-solvent systems using the pure component viscosity and density data and the
binary polymer-solvent diffusion data.
The aim of this work is to present some literature models used to calculate the solvent-polymer equilibrium and the diffusion
behaviors, including Fickian and non-Fickian diffusion. These models will be used to correlate equilibrium and diffusion data in
solvent polymer systems, such as: methanol - polyvinyl acetate, toluene - polyvinyl acetate, toluene - polystyrene,
dichlormethane - cellulose triacetate, water-polyvinyl alcohol and water – Nafion membranes, at different temperatures.