Preparation and gas separation performance of silicone‐coated polysulfone membranes

Composite membranes (CM) were prepared by coating the dense surface of different asymmetric polysulfone flat membranes (AM) with a solution of silicone rubber polymer. The surface porosity (ε) of the dense skin AM samples varied between 4 × 10−5 and 1·5 × 10−8, with an average mean pore size between 0·10 and 0·07 μm. Scanning electron microscopy (SEM), gas permeation experiments (H2, N2, CH4, CO2) and a simple resistance model were used for the determination of structure‐permeability relationships. This study indicates that the CM prepared with polysulfone AM having ε < 3 × 10−7, coated with a concentration of 6% silicone solution and a contact time of 1 min, has the best gas separation performance, with selectivities very close to the intrinsic polysulfone selectivities.