Fabrication and Properties of Asymmetric Fluorinated Polyimide Membrane with High Gas Permeability
Department of Applied Chemistry, Tokyo Metropolitan University; Hachioji-shi 192-0397 Japan
The control of gas transport though polymer membranes is of primary concern in the development of new gas separation membranes. Here, a new possibility for gas separation is presented using an asymmetric fluorinated polyimide membrane with an ultrathin and defect-free skin layer. The structure of the asymmetric membrane fabricated by a dry/wet phase inversion process showed an ultrathin skin layer and sponge-like structure characterized by the presence of macrovoids. We have prepared a series of asymmetric membranes with different skin layer thicknesses from 10 to 5.0×103 nm by the dry/wet phase inversion. Four gas permeances through the asymmetric membrane decreased in the order, CO2> O2>N2>CH4, and the trend was in accordance with the kinetic diameter of gas molecules. The gas selectivity of the asymmetric membrane increases with a decrease in the surface skin layer thickness, which may be due to the fact that the surface skin layer of the membrane with a thinner thickness forms a more packed structure.
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