Theoretical and experimental investigations of molecular migration and diffusion kinetics of organic esters into tetrafluoroethylene/propylene copolymer membranes

A theoretical analysis of the experimental results on the migration and diffusion kinetics of methyl acetate, ethyl acetate, n-propyl acetate, n-butyl acetate and iso-amylacetate into tetrafluoroethylene/propylene copolymer membranes has been made. Diffusion and permeability coefficients have been calculated from Fick's equation. The concentration profiles of the liquids have been calculated from a solution of Fick's equation as well as using an empirical relation for the esters into the varying penetration depths of the membranes at different time intervals. The diffusion coefficients show a systematic decrease with increasing size of esters and the results are discussed in terms of the membrane-solvent interactions.