Abstract
Microporous polypropylene membranes were prepared via thermally-induced phase separation from mixtures of polypropylene/soybean oil, polypropylene/oleic acid, and polypropylene/linoleic acid. The phase diagram of each system was obtained by thermal analysis and cloud point measurements. It was proved that each system has a liquid-liquid phase separation region at concentrations less than the monotectic composition. A cellular structure was obtained for each system, which is the typical structure for liquid-liquid phase separation via slow cooling. Fine structure with tiny polypropylene spherulites was obtained via quenching process. Mobility of diluent was related with its rejection during the polypropylene spherulite formation. A melt spinning apparatus was designed to produce microporous hollow fiber membranes. The mechanical strength of the hollow fiber seemed to be related to solution viscosity. Polypropylene/soybean oil samples had much greater solution viscosity than the other systems, and formed fibril structures with enhanced mechanical strength.
