The general theory of permeation of a gas or liquid through a polymer matrix [1] states that permeation is the product of a diffusion term and a solubility constant of the permeant in the polymer matrix, both of which are often independent of each other. The process of permeation through a polymeric barrier involves four steps: absorption of the permeating species into the polymer surface, solubility into the polymer matrix, diffusion through the wall along a concentration gradient, and finally desorption from the outer surface.