Hot-pressed PAN/PVDF hybrid electrospun nanofiber membranes for ultrafiltration

Abstract The objective of this study was to develop highly efficient and cost-effective ultrafiltration (UF) media/membranes from electrospun nanofibers alone without using expensive/complicated chemical modification methods. The hypothesis was that, during hot-pressing hybrid electrospun nanofiber membranes (ENMs) consisting of a thermoplastic polymer (e.g., PVDF) and a skeleton polymer (e.g., PAN), the PVDF nanofibers could be partially melted/softened even broken, leading to the conglutination/fusion of nanofibers. This would further result in the reduction of membrane porosities and the variation of membrane morphologies/structures; consequently, the membrane equivalent/apparent pore sizes would also be decreased. To test the hypothesis, as-collected PAN/PVDF hybrid ENMs (PPHENMs) were hot-pressed at 180 °C (above the PVDF melting point of ~177 °C) by using different pressures of 2.5, 5, and 10 MPa; for comparison, PPHENMs were also prepared upon being hot-pressed at 60 °C. The PPHENMs180 hot-pressed under 10 MPa had the lowest porosity of ~16.7 vol%, indicating that nanofibers occupied ~5/6 vol in the membrane; and the membrane exhibited high pure water flux value of ~200 L m−2∙h−1 under the applied pressure of 4 bar. Moreover, this membrane could completely reject/remove polystyrene particles with sizes larger than 20 nm from water; and the rejection percentages for bovine serum albumin and bovine γ-globulin molecules reached ~60% and ~75%, respectively. Therefore, hot-pressed hybrid ENMs made of thermoplastic nanofibers and skeleton nanofibers could provide an innovative and facile approach for the development of high-performance UF media/membranes.