PLASMA-GRAFT FILLING POLYMERIZATION - PREPARATION OF A NEW TYPE OF PERVAPORATION MEMBRANE FOR ORGANIC LIQUID-MIXTURES

A new membrane for organic liquid separation, called the filling-polymerized membrane, is proposed. To develop an organic liquid permselective membrane, suppressing membrane swelling as well as enhancing the solubility difference is important. The membrane is composed of two kinds of polymer materials. One is a porous substrate film, which is inert to organic liquids, and the other is a polymer, soluble only in specific solvents, filling the substrate pores. The solubility difference of the filling polymer causes permselectivity while the substrate matrix restrains the swelling of the filling polymer. In the present study, the filling-polymerized membrane was prepared by the plasma-graft polymerization technique. A porous high-density polyethylene film and poly(methyl acrylate) were used as the substrate and grafted polymer, respectively; this grafted polymer is soluble in aromatic hydrocarbons, such as benzene, but insoluble in aliphatic hydrocarbons, such as cyclohexane. Morphological analysis of the grafted membrane by TEM and FT-IR analysis showed that the grafted polymer filled the pores of the substrate. The membrane swelling experiments in a benzene/cyclohexane mixture verified that the matrix of the substrate restrained the swelling of the grafted polymer. Pervaporation separation of the benzene/cyclohexane mixture through the membranes obtained was carried out. The separation took place through the grafted polymer, which filled the pores of the substrate film, and the membranes showed high permselectivity for benzene, as expected. Suppressing membrane swelling raised the selectivity in accordance with the concept of the filling-polymerized membrane.