Gas permeation properties of asymmetric polyimide membranes with partially carbonized skin layer

In this study, the gas permeance and selectivity of the asymmetric polyimide membrane irradiated by He ions were measured using a high vacuum apparatus with a Baratron absolute pressure gauge at 76 cmHg and 35 degreesC. The asymmetric polyimide membranes were prepared from a dry-wet phase inversion process, and the surface skin layer on the membrane was irradiated by He ions in the fluence range from 1 x 10(12) to 3 x 10(15) (He+/cm(2)) at 50 keV. We demonstrated that the gas selectivity of the He+-irradiated membrane increased with an increase in the ion fluence and that the depth profile of the energy loss for the irradiating ions in the skin layer had a significant influence on the gas permeability and selectivity of the asymmetric membrane.