Study on the effects and properties of PVDF/FEP blend porous membrane

• FEP particles brought about interfacial microvoids in the PVDF/FEP blend membrane.
• FEP brought about the improvement of hydrophobicity and permeability.
• The cast solution exhibited good Newtonian flowing property which the n is 0.903.

Polyvinylideneflouride (PVDF)/poly(tetrafluoroethylene-co-hexafluoropropylene) (FEP) blend flat-sheet membranes were fabricated by the immerged phase-inversion method. Micro–nanometer scale FEP particles were introduced into PVDF/N,N-dimethylacetamide (DMAc) casting solution. Effects of FEP content on the rheology behavior of casting solution and performances of PVDF/FEP blend membranes were investigated respectively. Results shown that: (1) With FEP content increasing, the viscosity of casting solution decreased while the value of non-Newtonian index n increased. When FEP content was 60 wt.%, the value of n reached as high as 0.903 which demonstrated that the casting solution exhibited good Newtonian flowing property; (2) with FEP content increasing, the porosity and permeability of blend membranes increased obviously while the liquid entrance pressure (LEP) decreased. Blend membranes' cross-section morphologies shown that the increase in FEP content aided the formation of a larger and deeper finger-like pore structure; and (3) with FEP content increasing, mechanical strength of blend membranes decreased while the water contact angle increased at first then decreased.