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 SiO 2 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. Image 1 • PVDF membranes were fabricated via melt spinning and stretching (MS-S) process. • PSF was used as a rigid dispersed phase particle to promote higher porosity and flux. • Pores formed along the interface between dispersed and continuous phases. • Microfiltration pore size can be controlled by changing the stretching ratios. • MS-S is a "green" process that avoids use of toxic organic solvents. [ABSTRACT FROM AUTHOR]