Correlation of Nitrogen Enriching Polymeric Membranes Performance Developed through Various Methods with their Morphological Structure Revealed via SEM

Various phase inversion methods were applied to fabricate oxygen selective membranes out of polymeric materials such as polycarbonate (PC), ethylene vinyl acetate (EVA), and polyvinylchloride (PVC) that were dissolved in solvents like chloroform, tetrahydrofuran (THF), cyclohexanone, and dimethylformamide (DMF). Developed membranes were investigated using their permeability data and scanning electron microscopy (SEM) images. The more concentrated was the solution, the more homogeneous overall structure was obtained with smaller pores and more decreased gas diffusivity. Application of DMF as the solvent was found to be incorporated in the formation of larger porosity in the membranes. Less crystalline and hence more permeable membranes were made using volatile solvents such as THF. In casting 10% PVC solution in THF via the wet phase inversion method, micro-voids developed in the membrane and a non-homogeneous finger-type structure with porous skin was formed. Films with 28% vinyl acetate prepared by thermal phase inversion had a semi porous skin and a dense structure in the sub-layer. Results showed that EVA containing 28% vinyl acetate demonstrated the most appropriate permeability and selectivity for separation of oxygennitrogen gas mixtures.