Heat effects in sorption of organic vapors in rubbery polymers

During supposedly isothermal sorption/desorption of gases or vapors by solid polymers, latent heat effects alter local temperatures with the result that diffusion behavior may appear to be non-Fickian. Even when sorption curves are seemingly Fickian, spurious values of the diffusion coefficient, D, may still be inferred. These phenomena are examined in an experimental and theoretical study of incremental sorption/desorption of acetone vapor in the fluoroelastomer, vinylidene fluoride/hexafluoropropylene copolymer. A theoretical analysis developed earlier to model water vapor sorption in wool and cellulose is shown to successfully reconcile measured mass transfer rates and temperature changes.