Correlations with and prediction of activation energies of gas permeation and diffusion in glassy polymers

Three types of novel correlations for activation energies of gas permeation E-P and diffusion E-D in amorphous glassy polymers are considered and their application for prediction of the E-P and E-D values for different gases are examined. The first one is based on application of the group contribution method. Combined consideration of the equation of free volume and Arrhenius equation results in the correlation of E-P and E-D with free volume Vf and Fractional free volume (FFV). At last, the correlations between E-P and the permeability coefficient at a certain reference temperature P(T-ref), as well as E-D versus D(T-ref), are based on the fulfilment of the so-called compensation effect between activation energies and preexponential factors in activated processes. Examples of applicability of the correlations considered and recommendations for their use in prediction of the E-P and E-D values are given for transport of various gases in glassy polymers and separately in amorphous glassy polyimides. (C) 1998 Elsevier Science B.V. All rights reserved.