AbstractIt is well established that diffusion and relaxation processes in polymers aboveTgare closely related in that they are both governed by the polymer segmental motions, which are believed to be determined by the free volume present in the system. The diffusion coefficients of gases in elastomers can be accounted for by the WLF equation using the “universal values” of constantsAandB. The parameterK=BD/Bηof Frisch and Rogers is used as a correction factor. An analysis has been made of the diffusion of five gases in nine elastomers, from data found in the literature.Kand logDgare shown to vary with the penetrant but not with the polymer. Therefore, once the values ofKand logDgof gases are determined, their diffusion coefficients in any elastomers of knownTgat a variety of temperatures can be estimated. From the Arrhenius and the WLF relationships, an equation is derived to predict the activation energy of diffusion directly from the temperature of diffusion, the glass transition temperature of the amorphous polymer, the predetermined value ofK, and the universal constantsAandB. In the systems studied, the predictions agree on the average to within 11–17 of the values calculated from the experimenta
展开▼
