PVDF membranes with inter-connected pores prepared via a Nat-ips process Original Research Article

Polyvinylidene fluoride (PVDF) flat sheet membranes with inter-connected pores were prepared via a non-solvent assisted thermally induced phase separation (Nat-ips) process. Triethylphosphate (TEP) was used as the latent solvent to prepare the metastable PVDF casting solution. The asymmetric ultra- and symmetric micro‐filtration membranes were respectively prepared by adjusting the polymer concentration and quench bath composition. Finger-like pores were totally eliminated and highly inter-connected pores were formed in both membranes. The morphology, crystallization, and mechanical strength of PVDF membranes were characterized by Scanning Electron Microscopy (SEM), Atomic Force Microscopy (AFM), X-ray Diffraction (XRD), and tensile strength testing respectively. The effective through-pore size and pore size distribution of PVDF membranes were investigated by a bubble-point method. Pure water flux, protein rejection and fouling resistance were measured to study the filtration performance. All results showed that PVDF membranes with highly inter-connected pores and unimodal pore size distribution could be readily prepared by the Nat-ips process. The ultra- and micro‐filtration PVDF membrane exhibited a pure water flux of 120 and 1860 L/m2 h with the corresponding effective through-pore size of 0.11 μm and 0.26 μm respectively.