ABSTRACT
One–step preparation of electrospun bimodal fibrous membrane based on single nozzle is the key to the efficient fabrication of high–performance air filter. However, the preparation mechanism of electrospun bimodal fibers at low conductivity solution system is not clear, and there is a lack of evaluation methods for the quality of bimodal nanofibers, which limits the applicability of single nozzle electrospinning and the preparation efficiency of electrospun bimodal fibers. Here, three electrospinning processes at low conductivity solution systems of polyamide–6 (PA6), PA6 blended PVP (PA6/PVP), and PA6 blended polyethylene oxide (PA6/PEO) were studied according to the rheological properties and the fluid electrics (i.e., zeta potential), and the quality of the prepared bimodal fibrous membrane was creatively evaluated by R value. Inhomogeneous phase separations of the electrospinning jet along the direction parallel (x–axis) or perpendicular (y–axis) to the electric field were responsible for the formation of bimodal fibers. In addition, for the same solution system, the R value had a positive correlation with the air filtration performance. This work will greatly enhance the applicability of one–step single nozzle electrospinning for the preparation of bimodal nanofibers, improve the preparation efficiency, and promote the development of high–performance air filter. © 2022 Elsevier Ltd