Effect of immobilizing adsorption on the diffusion time lag

Abstract

Abstract A “dual sorption” model has been proposed by Michaels, Vieth, et al. to explain extensive equilibrium sorption data for several gases in some glassy polymers. To explain data on sorption kinetics, it was further postulated that one of the sorption modes immobilizes the gas molecules. Stated mathematically, this model leads to a modified form of Fick's second law. Both normal and desorption time lags for diffusion have been computed here for this model of diffusion in glassy polymers. The computed time lags are shown to be dependent on the boundary concentrations used in permeation. Experimental measurement of these time lags would be a sensitive and critical test to ascertain the validity of this theory.