Preparation and characterization of novel hollow fiber composite membranes

Poly(vinylidene fluoride) (PVDF)/poly(vinyl chloride)(PVC)/poly(methyl methacrylate)(PMMA) composite membranes were prepared by a dry-wet phase inversion technology using a triple spinneret. Dimethylacetamide (DMAQ and polyvinyl pyrrolidone (PVP) were used as a solvent and an additive, respectively. The membranes were characterized in terms of water flux and solute rejection ratio for the wet membranes. The cross-sectional structures were examined by scanning electron microscopy (SEM). In a conventional dry-wet spinning technology, the outer layer of the extruded polymer solution was exposed to the atmosphere in the air, which can result in relatively dense structure in the outer fiber surface. A modified spinning process using a triple spinneret was developed to overcome the above disadvantage. A fluid with a high amount of solvent was pumped through the outer annulus of the spinneret. The results demonstrated that the hollow fiber composite membranes prepared by this modified process show unchanged separation properties but improved water permeation flux.