Co-casting technique for fabricating dual-layer flat sheet membranes for gas separation

The present research investigated the feasibility of utilizing dual-layer flat sheet membranes for gas separation purpose. Polyetherimide (PEI) was used as top-layer (TL) and blending of polyetherimide and polysulfone (PSF) as sub-layer (SL) polymer matrixes. TL concentration, SL viscosity and SL PEI/PSF composition were chosen as the most important parameters to play with. To study the delamination/adhesion phenomena the PEI/PSF composition of SL was chosen as key-parameter. There was an optimum in the composition which by virtue the delamination phenomenon was suppressed hence guaranteed the TL/SL adhesion. FESEM images were interpreted by solubility analysis and permeation gas testing, and there was a good agreement between the membrane performance and the membrane morphologies. Dual-layer flat sheet membranes at PEI/PSF = 17.5/17.5–25/10, showed an enhancement in both permeance and selectivity. In conclusion, combination of incompatible polymer pairs will be a favourable choice to prepare the substrate membrane. Void spaces between the two incompatible polymers will enhance permeation rate of the substrate membrane, and consequently that of the composite membrane.