Multilevel structured TPU/PS/PA-6 composite membrane for high-efficiency airborne particles capture: Preparation, performance evaluation and mechanism insights

Particulate matter pollution poses a tremendous threat to people's health. Air filters composed of the random-oriented fibrous membrane could capture aerosol particles and protect the public against air pollution. However, conventional fibrous membranes still faced challenges such as the decline of filtration efficiency, fiber damage, and high pressure drop. In this study, a thermoplastic polyurethanes/polystyrene/polyamide-6 (TPU/PS/PA-6) multilevel structured composite membrane has been designed and prepared via electrospinning technique. The hierarchical membrane consisted of a TPU sub-micron (fiber size around 900 nm) fibrous layer, a PS bead-on-string nanofibrous (fiber size around 500 nm) layer, and a PA-6 ultrafine (fiber size around 60 nm) nanofibrous layer, produced both physical sieving manner and electrostatic effect to achieve a high filtration performance during a long-term operation. Due to the combined filtration mechanisms, the composite membrane had high filtration efficiency up to 99.99%, low air resistance of 54 Pa, high quality factor of 0.17 Pa-1, and robust mechanical strength of 6.72 MPa. In addition, the membrane presented insignificant deterioration during the particle-loading process, and still preformed filtration efficiency of 70% after discharge. The composite membrane exhibited considerable potential in personal protection and air purification for aerosol removal.