Evaluation of Gas Transport Properties of Highly Rigid Aromatic PI DPPD-IMM/PBI Blends

Abstract

In this work we discuss the gas transport properties behavior of dense blend membranes of a high free volume polyimide PI DPPD-IMM with PBI using the latter polymer in an attempt to enhance gas selectivity. Thermal and mechanical properties of dense blend membranes were also evaluated. The aim is to test the use of PBI as a gate polymer for establishing a window to enhance selectivity of CO2/CH4 and O2/N2 gas pairs with a minimum loss of gas permeability. Wide-angle X-ray diffraction measurements show that PI DPPD-IMM has an open structure with a d-spacing maximum at 5.4 A, which is not affected when PBI concentration in the blends is lower than 25 wt %. This reflects a moderate loss of gas permeability as compared to PI DPPD-IMM. Blends with PBI concentrations 50 wt % or above presented a shift in WAXD toward 4.4 A. It is found that as PBI concentration increases in the blend, there is an enhanced selectivity for O2/N2 and CO2/CH4 gas pairs duplicating their value with respect to PI DPPD-IMM and followin...