Preparation of PVDF Membranes via TIPS Method: The Effect of Mixed Diluents on Membrane Structure and Mechanical Property

Abstract

Abstract PVDF membranes were prepared via thermally induced phase separation method (TIPS). Two series of mixed solvents were used as diluents, and they were composed of γ‐butyrolactone(γ‐BA)/cyclohexanone(CO) or cyclohexanone(CO)/dibutylphthalate(DBP), respectively. In this paper, all the membrane formation processes only went through the solid‐liquid phase separation. The polymer melting/crystallization temperature in different mixed diluent was determined using differential scanning calorimeter (DSC). The effect of mixed diluents on crystal phase of membrane, crystallinity of membrane and membrane cross‐section morphology was investigated using wide angle X‐ray diffractometer (WAXD) and FT‐IR spectrometer. The obtained membrane exhibited two kinds of cross‐section morphology, including spherulite‐like crystallite and sheaf‐like crystallite. The membrane with a plenty of sheaf‐like crystallites had good tensile strength and permeation flux for pure water. Keywords: poly(vinylidene fluoride) membranethermally induced phase separationmembrane morphologypolymer crystallization 5 Acknowledgements The authors greatly appreciate the financial support of the Major State Basic Research Program of China (No. 2003CB615701), National Natural Science Foundation of China (No. 20576059), Postdoctoral Science Foundation of China (No.2005038345), SINOPEC Foundation (No. X505002) and CNPC Innovation Foundation.