Characterization of morphology and gas separation performance of dry-cast polycarbonate membranes

The development of the morphology and microstructure in dry-cast membranes from polycarbonate (PC)/dichloromethane (DCM) and PC/tetrahydrofuran (THF) solutions was investigated in this work. It was shown that changing the relative humidity (RH) of the air altered the transparency and the surface morphology of the membranes. Positron lifetime spectra for membranes with different surface morphology gave similar free volume parameters, which are believed to be mainly responsible for the constant selectivity of the membranes. In this study, the permeation and adsorption properties of the PC membranes cast from PC/DCM and PC/THF solutions were characterized as a function of the RH. Results demonstrated that the permeability of membranes increased with increasing RH of the air. The change in the permeability is presumably related to the forming of pores on the membrane surface due to the vapor-induced phase separation during casting. POLYM. ENG. SCI., 2013. © 2012 Society of Plastics Engineers