Robust Preparation and Pore Structure Design of Homogeneous Braid-Reinforced PVDF Hollow Fiber Membrane

In this work, the homogeneous braid-reinforced poly(vinylidene fluoride) (PVDF) hollow fiber membrane with multiple pore structure is prepared successfully based on a nonsolvent-induced phase separation (NIPS) method by adding different dioctyl phthalate (DOP) contents into the casting solution. The addition of DOP will restrict the phase separation process to avoid forming finger-like macropores, while the placeholder and movement of DOP are conducive to the formation of more microporous and through holes. It is found that when the DOP content is 13%, the membrane has a porous surface layer with large surface pores and a cross section with bicontinuous structure. Compared with the membrane prepared without DOP, the separation flux of the membrane increases by 407% while maintaining a higher separation efficiency. Moreover, the prepared membranes reveal outstanding mechanical properties, and their tensile strength all exceeds 100 MPa. These findings indicate that the method may open more opportunities for the pore structure design based on the NIPS method.