Solvent-free green preparation of PVDF/ PPTA-pulp hollow fiber membrane and construction of the multi-porous structure

Abstract

The traditional polyvinylidene fluoride (PVDF) separation membrane preparation process often requires the addition of organic solvents during membrane fabrication. In contrast, the solvent-free preparation method (melt spinning-stretching) used in this study is an environmental-friendly approach, but the hollow fiber membrane prepared by this method typically exhibit low permeability. To enhance the permeability of PVDF separation membranes fabricated by melt spinning-stretching, poly-p-phenylene terephthalamide pulp (PPTA-pulp) with highly fibrillated structure was used as the dispersed phase to promote the formation of interfacial pores during the stretching process, water-soluble inorganic (NaCl), water-soluble organic polyethylene oxide (PEO) and polyethylene glycol (PEG) were used as composite pore-forming agents to increase the diversity and continuity of the leached pores. In this study, we investigated the effects of PPTA-pulp content and stretching ratio on the permeability and separation performance, and discussed how PPTA-pulp addition affected the formation of stretching pores, interfacial pores, and dissolving micropores in the multi-pore structure. The results showed that this membrane-forming system has good melt processing and spinning properties, the prepared PVDF/PPTA-pulp hollow fiber membranes exhibited a multi-porous structure composed of dissolution pores and interfacial pores with different morphologies, the addition of PPTA-pulp increased the number of PVDF interfacial pores and membrane permeability. The amount of PPTA-pulp added has a significant impact on pore size and porosity.