Co-electrospun PU–PVDF/TiO₂ nanofiber membranes: A multifunctional strategy for durable, antibacterial, and low-resistance air filters

To address the issue of reduced mechanical strength and ductility in ultra-thin nanofiber membranes—common drawbacks when minimizing thickness to lower air resistance as well as the potential secondary pollution caused by bacterial growth during long-term use, this study developed a polyurethane (PU)-reinforced, antibacterial, high-efficiency, and low-resistance air filter membrane via co-electrospinning. The membrane, denoted as PU–PVDF/TiO₂, incorporates polyvinylidene fluoride (PVDF) as in situ polarization adsorption with PU as enhancement of mechanical strength and titanium dioxide (TiO₂) as a photocatalyst for antimicrobial functionality. The electret filtration performance, mechanical properties, and antibacterial activity of the membrane were systematically characterized using SEM, XRD, FTIR, filtration tests, and density functional theory (DFT) simulations. Novelly, DFT modeling was employed to elucidate the mechanisms of the self-polarization effect and the reinforcement role of PU. Results indicate that the addition of PU significantly improves the mechanical performance of the PVDF membrane, achieving a tensile strength of 6.59 MPa and a 27.2% increase in elongation at break, with only a minor rise in air resistance. Meanwhile, TiO₂ not only provides photocatalytic antibacterial activity but also facilitates the β-phase crystal transformation in PVDF, thereby enhancing filtration efficiency and reducing pressure drop—resulting in 97.3% efficiency for PM_1.0 and a low resistance of 31.8 Pa. Additionally, the incorporation of TiO₂ contributed to a reduction in average fiber diameter from 366 to 258 nm. The membrane exhibited an antibacterial efficiency of 99.9% against Staphylococcus aureus. The developed PU–PVDF/TiO₂ nanofiber membrane demonstrates great potential for industrial applications in high-performance, low-resistance, and antibacterial air filtration.

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