Abstract: This paper reported an investigation on the effect of mixing ratio of γ-butyrolactone and dodecanol on the morphology and properties of poly(vinylidene fluoride) (PVDF) hollow fiber membranes fabricated by a thermally induced phase separation method on the basis of principle of polymer-solvent compatibility. It was found that a solid-liquid phase separation between PVDF and dilutes occurred with a decrease of temperature when the fraction of γ-butyrolactone in the mixing diluents exceeded 30 wt %. A spherical structure was formed in the membrane, thus resulting in poor pore connectivity, low porosity, low pure water permeability and poor chemical resistance. When the fraction of γ-butyrolactone was less than 30 wt %, a liquid-liquid phase separation took place with a decrease of temperature. In this case, a cross-linking bi-continuous structure was formed, which led to high tensile strength and good chemical resistance for the hollow fiber membranes.

Key words: poly(vinylidene fluoride), thermally induced phase separation, mixed diluent, hollow flber membrane, tensile strength, chemical resistance