Characterization of asymmetric polymeric membranes by gas permeation

Polycarbonate films (thickness 18, 25 and 38 microm) were irradiated by a beam of 100MeV Ni7+ ion. The permeability for hydrogen and carbon dioxide was measured from both sides of membrane at increasing etching time. These membranes show larger permeability from the irradiation side, than the reverse side indicating the formation of conical tracks and asymmetrical membrane. The stopping range (Se) of 100MeV Ni7+ ion beam in polycarbonate is 22microm, for 18microm thick membrane the etching time at which the permeability increases rapidly is less than that of 38microm thick membrane, for both the gases. The difference in permeability from the two sides is attributed to the conical shape of the track generated by the ions. The controlled flow rate of the membrane leads to the design of a special type of gas filter.