The important technique of interfacial polymerization (IP) is used to fabricate thin film composite (TFC) membranes. In experiments here, microporous polypropylene (PP) flat film membranes were used as a support for fabricating TFC membranes for reverse osmosis by the IP technique. Substantial chemical, pH, and solvent resistance is provided by porous polypropylene membranes. Therefore, it is reasonable to choose porous polypropylene membranes as supports to fabricate TFC membranes for reverse osmosis.

The external and the pore surfaces of polypropylene flat film membrane were hydrophilized first by pre-wetting with acetone, then oxidized with chromic acid solution kept at 65°C. Next, the procedure to successfully coat the hydrophilized flat film membranes was implemented. Poly(ethyleneimine) (PEI) and isophthaloyl dichloride (IPD) were chosen as the reaction monomers for IP. Pressure dependences of the solvent flux and solute rejection of the TFC membranes were studied using the modified flat sheet membranes up to a pressure of 650-850 KPa. The TFC membranes were characterized by reverse osmosis based removal of sodium chloride (MW 58.44) in water. A rejection value of 89.43 % was achieved for sodium chloride at a pressure of 850 KPa. Solvent flux increased linearly with an increase in the transmembrane pressure. An increase in the transmembrane pressure also results in an improvement of sodium chloride rejection. Higher concentration and more reaction time for the monomeric system yields membranes with salt higher rejection.