Diffusion of gases and vapors through polyvinyl chloride–polyvinyl acetate copolymer films II. The effect of polymer segment mobility

The minimum free volumes involved in the diffusion of gases of various sizes through a copolymer of polyvinyl chloride–polyvinyl acetate have been calculated by use of equations developed by F. Bueche. It was found that as the gas diameter of the diffusant increased, the minimum free volume for diffusion increased exponentially. Bueche's modification of the Williams, Landel, and Ferry equation permitted use of the diffusion data to determine the number of polymer segments that cooperate in the diffusion process for each particular gas. The internal pressure of the polymer and the energy of activation for viscous flow were also calculated from the gas diffusion data. A discussion of the results is given.