SORPTION KINETICS AND DIFFUSION OF ALKANES INTO TETRAFLUOROETHYLENE PROPYLENE COPOLYMER MEMBRANES

Sorption kinetics and diffusion of hexane, heptane, octane, nonane, de cane, cyclohexane, and 2,2,4-trimethylpentane through tetrafluoroethyl ene/propylene copolymer membranes were studied using the gravimetric s orption method at 30, 45, and 60 degrees C. Coefficients of diffusion were calculated from Fick's equation. From these data, the permeabilit y coefficients were obtained. Analytical solutions of Fick's relations were used to estimate the liquid concentration profiles into the poly meric membranes at different times. The profiles of liquid concentrati ons were also simulated for the polymer-solvent systems using the nume rical simulation method. Activation parameters for diffusion and sorpt ion were evaluated and these results are discussed in terms of the mol ecular sizes and geometries of liquids (i.e., shape) as well as temper ature. The diffusion coefficients follow a systematic decrease with in creasing size of the penetrant molecules. The activation energies i.e. , E(D) values, increase with increasing size of n-alkanes. (C) 1996 Jo hn Wiley & Sons, Inc.