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 tetrafluoroe thylene/propylene copolymeric membranes have been studied by the weigh t gain assay method at 25, 40, 55 and 70 degrees C. Kinetic curves hav e been generated for these systems to compute diffusion and sorption c oefficients. Equilibrium concentrations have been described by the fir st-order kinetic rate equation. The temperature dependence of the tran sport parameters followed an Arrhenius relationship, from which the ac tivation energy for diffusion and permeation were calculated. Calculat ed results are discussed in terms of size and shape of diffusing molec ules into a polymer membrane. Profiles of liquid concentrations have b een 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