Thin film composite membranes were prepared by coating PDMS-g-PS and PDMS solution on porous polysulfone support. The permeabilities of oxygen, nitrogen and air increased as the pressure difference was increased. The selectivity ($P_O2/P_N2$) showed slight increase as the pressure difference was increased in the polystyrene containing membrane.
The selectivity increased from 2.03 to 2.46 as the polystyrene concentration was increased from 0 wt% to 35 wt% in the coating materials. The permeability showed Arrhenius type dependence on temperature and selectivity decreased as the temperature was raised.
The effects of the operating parameters (pressure ratio, cut and temperature) on the air separation were investigated. Oxygen enriched air with 34 wt% $O_2$ could be obtained through PDMS-g-PS/PDMS membrane (PS 35 wt%) when operated at pressure difference of 0.168 and stage cut of 0.01.
Silicone and polyurethane nonporous membranes were prepared. The permeability, diffusion and solubility coefficients of oxygen and nitrogen were estimated at the various temperatures. Polyurethane membrane had lower permeability but higher selectivity than silicone membrane. The permeability and diffusion coefficient increased very rapidly in polyurethane membrane as the temperature was increased.