Study on a novel PTFE membrane with regular geometric pore structures fabricated by near-field electrospinning, and its applications

Novel poly(tetrafluoroethylene) (PTFE) membranes with regular geometric pore structure were fabricated via near-field electrospinning (NFES) method. Firstly, computer aided design (CAD) was utilized to design membrane's pore geometry (triangle, diamond, square, hexagon and their different size). Secondly, the PTFE spinning solution consisted of PTFE emulsion and carrier (PVA aqueous solution) was electrospun into nascent PTFE/PVA membrane, which had regular geometric pore structure. Finally, the nascent membrane suffered sintering process, and the NFES PTFE membrane was obtained. Effects of PTFE/PVA mass ratio, sintering temperature and annealing condition, pore geometry on the membrane morphology, structure and properties were investigated, respectively. Results found that the square membrane showed good combination of membrane performances and properties, when PTFE/PVA mass ratio was 6:1 and sintered at 380 °C followed by cooling in muffle furnace. Owing to the excellent hydrophobicity, the obtained PTFE membranes exhibited excellent oil/water separation performance in terms of high oil flux (707 L m-2 h-1) without extra pressure, and high separation efficiency (rejection up to 99.6%). Owing to the regular and accurate pore structure, the PTFE membrane was utilized in the particle sequential separation. The mixed silica (SiO2) particles with a series of diameter (1, 5, 10, 20 μm) were sequential separated by PTFE membranes with different pore geometry, and the rejection reached up to 82.0%.