Through polymers localized sorption

Although extensive data for mixed-gas permeation in the plasticization regime are not available, good pure-gas values are available and illustrate some important points. The permeability of CO2 in various substituted polycarbonates shown in Figure 28 (111) increases with pressure above a certain characteristic value for each of the polymers. The shapes of the permeability curves are like the curve shown schematically in Figure 21. Plasticization occurs despite the fact that the downstream pressure is maintained at a vacuum of less than 1330 Pa (10 mm Hg). To determine when true transport plasticization occurs, the local diffusion coefficient Dap(Ca), which measures the ability of a penetrant to move through the membrane at a point where the local concentration of penetrant is equal to Ca, must be considered. The sorption isotherms for CO2 in the various materials are shown in Figure 29 (111), and application of the standard... 

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