Molecular transport of organic esters into tetrafluoroethylene/propylene copolymer membranes

Diffusion, permeation, and equilibrium sorption coefficients have been determined using a sorption gravimetric technique for methyl acetoacetate, ethyl acetoacetate, methyl benzoate, ethyl benzoate, methyl salicylate, isobutyl salicylate, and diethyl malonate into tetrafluoroethylene/propylene copolymer membranes in the temperature range 25–70°C. The sorption kinetics process has been characterized by first-order rate constants and penetration velocities. From a temperature dependence of the transport coefficients, the activation parameters have been estimated. It is observed that the values of the transport coefficients for the systems of this study depend on the nature of the penetrant molecules rather than on their molecular sizes. On the whole, the mechanism of solvent transport into the copolymer membranes used here follows nearly the Fickian trend. © 1994 John Wiley & Sons, Inc.