In this research, the effects of preparation conditions, including the coagulation bath temperature, polymer solution composition, preliminary drying time, and thickness of cast polymeric films, on the phology of ethylene/vinyl acetate copolymer membranes were investigated with scanning electron microscopy and nitrogen gas permeability tests. Flat sheet membranes were prepared through a thermal–wet phase-inversion method. Scanning electron microscopy pictures showed asymmetric structures for some of the membranes. It was also observed that the porosity of the membranes decreased with an increase in the temperature of the coagulation bath and the solvent evaporation period. When the concentration of the polymer solution was increased from 5 to 12 wt %, the nucleation and growth of the solvent-rich phase replaced the nucleation and growth of the polymer-rich phase. With an increase in the thickness of the cast polymeric films, the number of macrovoids increased in the membranes. The nitrogen gas permeability of the developed membranes was in good agreement with the scanning electron microscopy results.

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