A MODIFIED RADIOTRACER TECHNIQUE FOR MEASURING SOLVENT DIFFUSION WITH ZERO CONCENTRATION GRADIENT THROUGH POLYMER-FILMS

A modified radiotracer technique is described for measuring liquid diffusion through polymer films. The method has been evaluated by following the diffusion of ethanol and of ethyl laurate through oriented polypropylene (PP) and polyethylene terephthalate (PET) films which had been preswelled in ethyl laurate and ethyl acetate respectively. Ethanol can diffuse easily through PP and PET with the assistance of a swelling agent. Even in the case of PET, where only trace amounts of diffusion are found, the method was adequately sensitive to measure diffusion coefficients from the linear diffusion graphs. Because diffusion can be studied under conditions of zero concentration gradient, the method is capable of yielding values of self-diffusion coefficients. © 1990.