AbstractPermeability coefficients have been measured for CO2and CH4in polyethylene membranes at 20, 30, and 40°C and at applied gas pressures up to ca. 2 MPa and for CH4in three kinds of rubber films at 25, 30, and 35°C and at applied gas pressures up to ca. 2.4 MPa. The pressure dependence of the logarithms of permeability coefficients became linear except for the CO2—polyethylene system, where the pressure dependence became quadratic, with a minimum at a certain value of pressure. The linear and quadratic dependences can be interpreted by a free volume model of diffusion of a gas molecule in polymers. The temperature dependence of the permeability coefficients at zero pressure difference across the polymer film for each system obeyed an Arrhenius type equat
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