Abstract
From classical theory, gas permeation rate through an elastomeric membrane from high pressure to low depends directly on the applied pressure differential. However, at several hundred atmospheres, the elastomer can apparently be consolidated, to reduce permeation rate. As a contrast, swelling also occurs in some other cases. Many permeation coefficients have been obtained at these pressures for the permeation at different temperatures of several gases through various polymers, and data rationalized.
Use of a device to measure the thickness of the pressurized sample membrane in situ has led to correlation being shown between thickness reductions when pressures are applied and corresponding decreases in permeation coefficients. For some conditions, these changes take several hours to occur, indicating that the polymer Tg has been increased by the applied high pressure to become near to the test temperature. It is more likely that the compacted polymer is "leathery" rather than "glassy". When permeating gas and elastomer are chemically-compatible, swelling has been observed, accompanied by a further reduction in permeation rate. A limited number of diffusion and solubility coefficient data are given for various gas/polymer combinations.
