Sorption/diffusion of aliphatic esters into tetrafluoroethylene/propylene copolymeric membranes in the temperature interval from 25 to 70 degrees C

The sorption and diffusion of seven aliphatic esters into tetrafluoroethylene/propylene copolymeric membranes have been studied by the weight gain assay method at 25, 40, 55 and 70 degrees C. Kinetic curves have been generated for these systems to compute diffusion and sorption coefficients. Equilibrium concentrations have been described by the first-order kinetic rate equation. The temperature dependence of the transport parameters followed an Arrhenius relationship, from which the activation energy for diffusion and permeation were calculated. Calculated results are discussed in terms of size and shape of diffusing molecules into a polymer membrane. Profiles of liquid concentrations have been calculated by solving Fick's diffusion equation and also by using a numerical method based on a finite difference method. Copyright (C) 1996 Elsevier Science Ltd