Fabrication of novel PVDF/P(VDF-co-HFP) blend hollow fiber membranes for DCMD

In this research, porous hollow fiber membranes for DCMD desalination were fabricated by non-solvent induced phase inversion. The membrane materials were PVDF 6010 and its blend with P(VDF-co-HFP), expected to combine the advantages of each material. It was found that with higher P(VDF-co-HFP) content in the blend, the membrane materials acquired stronger hydrophobicity. The maximum tensile strength was obtained with hollow fibers having 30% P(VDF-co-HFP), which was 2.86 MPa. Cloud point test showed that the one phase region of the solution with neat P(VDF-co-HFP) was closer to the polymer-solvent axis in the phase diagram, indicating a lower thermodynamic stability of this polymer solution. The varied degree of the liquid/liquid demixing and the solid/liquid demixing induced by changing P(VDF-co-HFP) content might be the underlying factor causing the dissimilarities in the above membrane structural and mechanical characteristics. DSC was employed to corroborate the crystallinity of the membranes. The DCMD tests using NaCl aqueous solution showed that membranes with higher PVDF 6010 content provided apparently higher flux. Stable salt rejection above 99% were obtained with all the membranes under the operation conditions investigated.