Gas-separating polymer membranes

Figure 9-34. General sehematie of the microwave installation for plasma treatment of gas-separating polymer membranes (1) modulation system (2) power supply (3) microwave magnetron (4) plasmatron ...

Microwave Plasma System for Surface Modification of Gas-Separating Polymer Membranes... 

Microwave plasma modification of the surfaces of siloxane membranes (particularly lestosil and polycaibosil membranes) and acetate cellulose membranes is an example of plasma fabrication of asymmetric highly selective gas-separating polymer membranes (Arbatsky etal., 1988,1990). A schematic ofthe microwave plasma installation is showninFig. 9-34. 

The selectivity of gas-separating polymer membranes can be significantly increased by treatment in a microwave plasma (Section 9.9.2), which is illustrated in Figs. 9-40, and... 

Chemical and Stmctural Modification of Surface Layers of Gas-Separating Polymer Membranes by Microwave Plasma Treatment... 

To describe the influence of non-equilibrium plasma-treatment and cross-links on the permeability and selectivity of the gas-separating polymer membranes, let us first calculate the energy required for formation in an unbounded elastic medium of a hollow sphere with radius R corresponding to the radius of a penetrating molecule. Solving the Lame equation (9-90) in the absence of external forces (/ = 0) and for radial displacement Mr = R, the compression energy of the elastic medium can be found in this case as (Landau Lifshitz, 1986)... 

Permeability of Plasma-Treated Gas-Separating Polymer Membranes. Analyzing relation (9-97), compare the influence of sizes of penetrating molecules and cross-links on the permeability of plasma-treated gas-separating polymer membranes. Why do these two sizes appear in relation (9-97) for gas permeability through the membrane in a non-symmetric way with significantly different powers. 

In EP07708077A3 (Dabou et al. 1996), gas separation polymer membranes were prepared from mixtures of a polysulfone, Udel P-1700 and an aromatic polyimide, Matrimid 5218. The two polymers were proven to be completely miscible as confirmed by optical microscopy, glass transition temperature values and spectroscopy analysis of the prepared mixtures. This complete miscibility allowed for the preparation of both symmetric and asymmetric blend membranes in any proportion from 1 to 99 wt% of polysulfone and polyimide. The blend membranes showed significant permeability improvements, compared to the pure polyimides, with a minor change in the selectivity. Blend membranes were also considerably more resistant to plasticization compared with pure polyimides. This work showed the use of polysulfone-polyimide polymer blends for the preparation of gas separation membranes for applications in the separation of industrial gases. 

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