A study on the development of composite membranes for the separation of organic vapors

Composite membranes were prepared by the plasma polymerization of hexamethyldisiloxane (HMDS) monomer, and the membranes were applied for the separation of volatile organic compounds (VOC) from air. A tubular type reactor system with an external coil was provided to initiate and maintain glow discharges. Through the plasma polymerization of HMDS, poly(dimethylsiloxane)-like films were prepared. The FT-IR spectra of the plasma-polymerized films were similar to that of poly(dimethylsiloxane) (PDMS). The ratio of discharge power to monomer flow rate (W/F) in plasma polymerization affected the permeability of penetrants. In the plasma-polymerized membranes prepared under low W/F ratio, the permeability was mainly dependent of the condensability of VOCs and the membrane showed the high permselectivity of organic vapors over nitrogen. As the W/F ratio increased, molecular size effect became stronger and the selectivities decreased.