Optimization of the mechanical properties of polymeric composite membranes prepared via emulsion pathways

Abstract

A novel composite membrane which is effective in the separation of ethanol-water mixtures by pervaporation was prepared by the concentrated emulsion polymerization pathway. In this method, a concentrated emulsion is employed as a precursor for a hydrophilic-hydrophobic composite from which subsequently the membrane is prepared by polymerization. A mixture of styrene (St) and butyl acrylate (BA) constitutes the continuous phase of the emulsion, while an aqueous solution of sodium acrylate (SA) forms the dispersed phase. The presence of BA in the continuous phase profoundly affects the mechanical properties of the membranes. In its absence, the membrane is brittle; it becomes more rubber like as the concentration of BA increases without becoming too large. It was found that water causes the swelling of the membrane to a much greater extent than ethanol does. The separation factor (α) increases markedly, and the permeation rate through the membrane decreases gradually as the water concentration decreases in the feed. Increasing the content of polysodium acrylate (PSA) results in a higher permeation rate, but the separation factor (α) decreases. At room temperature, the separation factor (α) varies between 23 and 724, and the permeation rate varies between 13 and 246 g/m 2-hr.