Design of PVDF hollow fiber membranes with stable crystalline and porous structure by solvent‐free method

Abstract

AbstractOne of the critical principles of green chemistry and environmental sustainability is to avoid using harmful solvents in chemical processes. In this study, a novel solvent‐free method was employed to prepare poly (vinylidene fluoride) (PVDF) hollow fiber composite membranes with stable crystalline and porous structures. Utilizing the cold‐hot stretching method, the crystalline structure and orientation of PVDF were effectively redesigned, resulting in improved mechanical and penetration properties of the membrane. Additionally, an investigation into the internal crystalline structure of the PVDF hollow fiber membrane was conducted, focusing on crystalline changes induced by ion‐dipole interactions. Results indicated that the addition of neutral ion‐dipole functional particles (N‐P) promoted the conversion of α crystalline to β crystalline, leading to stable β crystalline and controllable pore sizes in the prepared PVDF hollow fiber membrane. Furthermore, the internal crystalline structure significantly contributed to enhancing the membrane's mechanical properties and penetration performance. Notably, a PVDF hollow fiber with high β crystalline content was achieved through 150% cold‐hot stretching and the addition of 20. wt% N‐P further enhanced the β‐crystalline content in the membrane. This study presents a promising approach for reducing solvent consumption and minimizing environmental impact in the field of environment‐friendly membrane fabrication.