Studies of the permeability coefficient of polyethylene terephtalate and the influence of protons implanted on polymer molecular structure

The principle of operation of an apparatus developed to study gas permeation through thin film is described, and the experimental procedure is discussed. Use is made of diffusion theory to obtain an expression for the permeability coeficient K as a function of the rate of increase of the pressura in the receiving volume. Measurements of K for Polyethylene Terephtalate (P.E.T.) were performed using Argon and Helium. The Gibbs function for ''He-P.E.T'' was determined from the study of K as a function of the film temperature. Protons were implanted along the thickness of P.E.T samples. The observed increase of K may be explained by possible modifications of the polymer structure: degradation and/or crosslinking. Preliminary studies using small angle X-rays scattering suggest again structurural modifications of the proton implanted P.E.T. (author)