Preliminary investigation of gas transport mechanism in a H+ irradiated polyimide-ceramic composite membrane

Recent research by our group indicated that ion beam irradiation can simultaneously increase the gas permeability and permselectivity of polymeric membrane materials. The temperature dependence of the gas permeation properties of a H+ ion irradiated polyimide-ceramic composite membrane was investigated to address issues of changes in the gas transport mechanism in irradiated polymers. As was seen for glassy polymers, the temperature dependence of the permeation properties of the irradiated membrane followed an Arrhenius type relationship. Both the activation energy (E-p) for gas permeation and the pre-exponential factor (P-0) of the irradiated polymer were greater than the values of the unmodified bulk polymer. Large increases in the pre-exponential factor of the irradiated sample for small size gas molecules (He, O-2 and CO2) combined with the dominant contribution of the pre-exponential factor to the permselectivity for several gas pairs (He/CH4, O-2/N-2, and CO2/CH4) implied that the irradiated sample had a different permeation mechanism than the bulk material. (C) 1999 Published by Elsevier Science B.V. All rights reserved.