A simple device for quality control of polymer films, using measurements of permeation and diffusion coefficients

A simple device for the rapid determination of transport characteristics of vapors, gases or gaseous mixtures through polymer films has been constructed. This device may be useful either for routine quality control or for precise research work. It consists of two coupled permeation cells: the difference between the permeation rates of a tested specimen with respect to a standard film is measured and the resulting signal interpreted in terms of diffusion and permeation coefficients. The two coupled cells are of a differential type: the gas permeating through the film is collected by a flowing stream of an inert gas and carried to the analytical system (gas-chromatographic determinations have been used in this study). Such a system allows high pressure measurements without imposing mechanical stresses on the film and determination of transport coefficients of any gaseous mixture. A theoretical analysis of the transient signal in terms of transport parameters is reported together with some experimental results on commercial polycaprolactam films.