Investigations on sorption, diffusion and permeation of chloro-alkanes and -alkenes through fluoroelastomeric membranes

Sorption, diffusion and permeation of halogenated liquids such as chloroform, dichloromethane, carbon tetrachloride, 1,2-dichloroethane, 1,1,2,2-tetrachloroethane, trichloroethylene and tetrachloroethylene into commercial fluoroelastomer (FC-2177 D) were studied at 30, 40 and 50°C using the sorption gravimetric method. The concentration-independent diffusion coefficients were calculated using Fick's equation from the initial linear portion of the sorption curves. The liquid concentration profiles were also computed using the analytical solution of Fick's equation with the appropriate initial and boundary conditions, and these were presented as a function of penetration depth of molecular migration and time of immersion. These results are discussed in terms of the molecular size of liquid penetrants and temperature. The transport phenomenon was found to follow anomalous behavior. From a temperature dependence of diffusion and permeation coefficients, the Arrhenius activation parameters were estimated. The activation energies for diffusion and permeation did not exhibit any systematic dependence on size of the penetrating molecules, but these were influenced by the nature of the liquids. None of the liquids showed any degradative effects on the membrane.