The diffusion and solution of gases in highly crosslinked copolymers

Abstract

A study has been made of the diffusion and solution of helium, hydrogen, neon, argon, krypton, oxygen, nitrogen, methane and carbon dioxide in a series of highly crosslinked copolymer membranes in the temperature range 40° to 80°C. The membranes were prepared by copolymerizing mixtures of tetraethylene-glycoldimethacrylate (TEGDM) and ethylacrylate (EA) containing 100, 80, 60, 40 and 20 mole per cent of TEGDM. Diffusion and solubility coefficients were obtained by several different methods. Some anomalies were found and are discussed in terms of the polymer microstructure. The diffusion and permeability coefficients of gases larger than neon decreased by almost an order of magnitude as the mole percentage of TEGDM was increased from 20 to 100. The solubility coefficient was little affected. The diffusion coefficients were analysed in terms of the transition state and activated zone theories of diffusion and several correlations of the diffusion and solubility coefficients with other physical parameters were examined. Separation factors for several gas pairs at 60°C were calculated and examined along with similar data for other systems. In general it appears that high permeation rates are gained at the expense of permselectivity.