Single-component materials, permeability membranes

Table 20.2-S presents the system parameters determined by Ward et al. for producing 10 x 10 SCFD of 30% oxygen with single-stage 1000 A ultrathin silicone-polycarbonate copolymer membranes. In addition to their thinness, these membranes had high permeabilities due to their silicone rubber component (57% on a mole basis) (see Fig. 20.2-7). The separation factor for the family of silicone-polycaibonate materials shown in Fig. 20.2-8 increases as the fraction of flexibilizing silicone decreases. If one considers the ratio of permeabilities at 0% silicone and at 57% silicone, it is clear that an aqrproximately lOO-foU increase in permeation area is required to achieve the same oxygen productivity far pure polycarbonate membranes as for the 57% copolymer. Thus, roughly 7.8 x 1(T ft of membrane area widi a 1(K)0 A thick separating layer would be required to supply the same absolute amoum of oxygen in the product gas for the polycarbonate case as compared to 78,CW0 ft for the copolymer case.

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