Solvent-free green fabrication of PVDF hollow fiber MF membranes with controlled pore structure via melt-spinning and stretching

In this work, we developed a solvent-free and green route to prepare poly(vinylidene fluoride) (PVDF) hollow fiber membranes through melt-spinning and stretching (MS-S) technique based on the interface pore theory. The bisphenol A polysulfone (PSF) molecular chain contained the rigid aromatic rings, which was introduced into the PVDF melt for improving the interface layer between the matrix phase (PVDF) and the dispersed phase (PSF). Due to the poor compatibility of the two phases, the interface pore structure could occur and be controlled precisely through the further stretching. Interestingly, the pore size of the prepared membranes could be controlled from 0.172 to 0.550 μm by changing the stretching ratios. Applied to filter the SiO2 and active sludge suspensions, the prepared membranes showed a high rejection (99.99%), and the turbidity decreased sharply (˂0.01 NTU). In addition, the obtained membranes exhibited outstanding mechanical properties, which could meet the long-term service demand. In particular, there were not any hazardous solvents used in the preparation process, which could achieve green preparation of PVDF membranes.