PERVAPORATION MEMBRANE FOR ETHANOL-WATER MIXTURE PREPARED BY PLASMA POLYMERIZATION OF HEXAFLUOROETHANE-ALLYLAMINE SYSTEM

Pervaporation membrane for ethanol-water mixture was prepared by plasma polymerization and the relationship between ethanol permselectivity and membrane structure was studied. To control hydrophobicity of membranes, allylamine (AA) was plasma-copolymerized with hexafluoroethane (HFE) at various HFE/AA ratios of monomer flow rate. Membranes were characterized by IR, XPS and SEM. The particle-like structure contained in membranes, particularly in those prepared at lower HFE/AA values, tends to decrease with increase in HFE added. Fluorine content, F/C, increased with HFE up to ca. 1.2, although some amount of hydrogen as well as nitrogen and also oxygen, which may be incorporated as radicals formed in membrane reacting with oxygen in air, can be detected. The separation coefficient of ethanol, measured for 4.8wt·%-solution at 40°C, also increased, but the permeation flux decreased with HFE/AA or F/C ratio. The effect of HFE plasma treatment onto AA membrane was also investigated. © 1990, The Society of Chemical Engineers, Japan. All rights reserved.