Gas permeation properties of hexafluoro aromatic polyimides

Two hexafluoro-substituted aromatic polyimides, 6FDA-p-PDA and 6FDA-4,4′-ODA, were synthesized. The influence of some synthetic conditions on physical properties and gas permeabilities of the 6FDA polyimide membranes were studied. Gas permeabilities and permselectivities of six different gases for the homogeneous films have been determined at 15-35°C and at pressures up to 10 atm. 6FDA polyimide composite membranes with asymmetric structure were prepared by the solution-casting method. The membranes showed exceptionally high permeation fluxes and permselectivities. No capability deterioration of asymmetric membrane was observed during 19 days operation with pure gases.