Design of PTFE/PP multilayer composite membrane as mask filter layer with steady filtration efficiency and high dust holding capacity

Currently, commercially available mask filter materials, such as electrostatic electret polypropylene (PP) melt-blown cloth and polytetrafluoroethylene (PTFE) nanofiber membranes, always suffer a compromise between filtration efficiency and dust holding capacity, when used alone during air purification. In this study, a novel multilayer composite membrane was designed by thermally laminating a PP melt-blown filter layer (as the dust-holding layer) and a PTFE (Polytetrafluoroethylene) nanofiber layer (as the filtration layer), to improve filtration stability and capacity. The performance of the composite membrane was examined in relation to the effect of key laminating parameters (i.e., temperature, pressure and speed) on the dust holding capacity, filtration efficiency and resistance. NaCl aerosol was used as the model dust source. Results show that the composite membrane, prepared at a lamination temperature of 120 °C, a lamination pressure of 0.2 MPa and a lamination speed of 4 m/min, had a dust-holding capacity of 12.21 g/m², which was over six times higher than that of the PTFE nanofiber membrane alone. During ten repeated cycles of NaCl aerosol filtration, water washing and alcohol disinfection, the composite membrane exhibited a steady filtration efficiency of above 99.9% over the NaCl aerosol. Meanwhile, the dust holding capacity was maintained above 8 g/m² over the multiple cycles, while the resistance was smaller than 70 Pa.