Lowering spinning temperature for polyketone (PK) hollow fiber membrane fabrication with low-toxic diluent system via thermally induced phase separation

Due to the excellent solvent resistance properties of polyketone (PK), the traditional non-solvent induced phase separation (NIPS) preparation process is both highly toxic and complex. In this work, we successfully and efficiently prepared PK hollow fiber membranes using the thermally induced phase separation (TIPS) method, capitalizing on a low-toxicity diluent system of polyethylene glycol 300 (PEG300) and triethylene glycol (TEG). Moreover, by simply adding TEG to the diluent, we achieved a reduction in the spinning temperature, resulting in membranes that display an interconnected structure formed through the liquid-liquid phase separation process. We systematically investigated the impact of the TEG ratio in the diluent, PK concentration, and propylene carbonate (PC) ratio in the bore liquid on the phase diagram, membrane morphology, and characteristics of PK membranes. Increasing the PC ratio in the bore liquid significantly improves the inner surface porosity due to PC penetration into the dope solution, leading to high water permeability. Additionally, the resulting PK membrane exhibits exceptional resistance to organic solvents. This work introduces a novel approach to lower the spinning temperature for PK membrane preparation in the TIPS process while preserving the membrane structure and properties.