GAS PERMEATION IN POLYCARBONATE MEMBRANES PREPARED BY THE WET-PHASE INVERSION METHOD

Polycarbonate (PC) membranes prepared by the wet-phase inversion proce ss was investigated in the present study. Varying amounts of a non-sol vent (methanol) were added to the casting solution during membrane pre paration and was found to increase significantly membrane porosity. Th e gas permeability of the PC membranes was increased from 1.68 and 0.2 6 barrers, respectively, for oxygen and nitrogen without the non-solve nt, to 35.1 and 3.86 barrers with 3 ml of the nonsolvent added. The dr astic increase in gas permeability was accompanied by only a slight de crease in selectivity. Hence, the PC membranes prepared with addition of methanol have a great potential for industrial oxygen enrichment ap plications. A simple gas diffusion model with an effective gas diffusi on coefficient was found to describe reasonably well the gas permeatio n process. The estimated effective gas diffusion coefficient can close ly reflect the increase in gas permeability of the membranes due to th e addition of methanol.