Preparation of PVDF Hollow Fiber Membranes via Melt Spinning-stretching Method and Its Oil-water Separation Performance

Nowadays, green chemistry is attracting more and more attention. In this paper, polyvinylidene fluoride (PVDF) hollow fiber membranes were prepared by environment-friendly melt spinning-stretching method without any solvent and diluent involved in membrane preparation process. In particular, we selected perfluoroethylene propylene (FEP) as the dispersed phase and water-soluble polyethylene glycol (PEG) and calcium chloride (CaCl2) as the pore-forming agents. The influences of stretching ratio on the structure and properties of PVDF hollow fiber membranes were studied in detail based on pore size distribution, mechanical properties and water-in-oil emulsion separation performance. The results show that the dispersed phase and pore-forming agents can be uniformly dispersed in the matrix phase, and the the pore size distributions are relatively narrow. With the increase of the stretching ratio, the mean pore sizes and porosities of the membranes also increase. Meanwhile, the hydrophobility of the membranes decreases, but the water contact angles are all above 100 degrees. The M-3 membrane shows a good mechanical property and separation effect for water-in-oil emulsion, of which the tensile strength can be up to 19.3 MPa and the separation effects are all higher than 97% at 0.02 MPa after five cycles. The results demonstrate that the membrane is potentially applicable in oil-water separation process.