Structurally tunable polytetrafluoroethylene nanofiber membranes derived by in-situ fibrillation technology with polycaprolactone as precursor for high-performance filtration and separation applications

Porous polytetrafluoroethylene (PTFE) membranes are widely used in high-efficiency filtration, protective ventilation, and medical applications, but their traditional stretching-based preparation methods suffer from significant problems such as pollution, high energy consumption, and lengthy processes. Here, we prepared PTFE nanofiber membranes based on in-situ fiber forming technology. Exploiting the excellent melt processability of polycaprolactone (PCL) over a wide temperature window (90–180 °C), a microstructure-controllable fabrication strategy for PTFE nanofiber membranes was developed. By systematically regulating processing temperature, screw speed, and circulation time, the shear force imposed on PTFE crystals was precisely tuned, enabling fine control over fiber diameter, pore size, and membrane thickness. The resulting PTFE nanofiber membranes exhibit tunable fiber diameters (70–185 nm), pore sizes (0.23–1.4 µm), and thicknesses (8–24 µm), while maintaining a high porosity (> 76%). The membranes demonstrate excellent tensile strength of up to 25.3 MPa and outstanding chemical stability. In oil–water separation, the membranes show high oil permeance and separation efficiency. Moreover, in high-precision solid–liquid filtration, the membranes achieve a rejection rate approaching 99.9% for submicron particles such as carbon nanotubes (CNTs), significantly outperforming commercial stretched PTFE membranes in filtration precision. This research provides a versatile strategy with high structural customizability to address the challenges in controlled fabrication of PTFE nanofiber membranes and their application in high-precision filtration fields.