CO2 Plasticization of polyethersulfone/polyimide gas‐separation membranes

This work reports the CO2 plasticization of gas‐separation hollow‐fiber membranes based on polyimide and polyethersulfone blends. The feed pressure effect on the permeance of pure gases (CO2, N2) and the separation performance of a gaseous mixture (CO2/N2, 55/45%) is examined. Contrary to dense membranes, the permeance of CO2 through ultrathin asymmetric fibers increases immediately with pressure resulting in pronounced apparent plasticization and reduction of the ideal CO2/N2 selectivity. However, no evidence of plasticization was observed when a CO2/N2, 55/45% mixture was fed to the hollow‐fiber membranes. In all cases, CO2 permeance decreased with pressure, while that of N2 remained constant. Experimental results were validated by means of mathematical modeling. Membrane‐separation performance was overestimated when pressure‐independent permeabilities were used in the model, while pressure‐dependent permeabilities, due to the overall effect of plasticization and competition phenomena, explained excellently, the obtained stage‐cut and permeate purity.