Optimization of the electrospinning process of polyurethane nanofibers and their filtration performance for use in respiratory protection mask filters

Electrospun nanofibers can be used to produce filter media in personal protective equipment for the military. The present study aimed to optimize the electrospinning process used to create polyurethane nanofiber substrates and compare the optimum substrate filtration performance with a typical commercial substrate used in the structure of N95 respirators. In this experimental study, polyurethane polymer solutions were prepared in a solvent system consisting of dimethylformamide and tetrahydrofuran with a mixing ratio of 3: 2 (v/v%). The main and interactive effects of electrospinning process parameters (polymeric solution concentration, applied voltage, electrospinning distance, and polymer injection rate) on the mean diameter and uniformity of electrospun nanofibers and their optimal values were studied using response surface methodology, specifically, a central composite design. The filtration efficiency and pressure drop of the electrospun polyurethane nanofiber filter media were compared with the commercial media used in the N95 respiratory mask structure using a prepared filtration test rig. Based on the results of the quadratic model, the optimal conditions for the electrospinning of polyurethane polymer were polymeric solution concentration, applied voltage, electrospinning distance, and polymer injection rate of 14 w/v%, 17 kV, 10 cm, and 0.4 ml/h, respectively. The results showed that despite having a lower base weight, the filtration efficiency and quality factor of four layers of polyurethane nanofiber filter media were higher than that of a three-layer N95 mask (98.24% % versus 98.1%, and a quality factor of 0.061 versus 0.084 Pa-1, respectively). It can be concluded that the electrospun polyurethane nanofiber media have acceptable filtration efficiency and quality factor values for filtration applications. In addition, the fabrication of nanofiber media with desired properties (nanofiber diameter, uniformity, etc.) for use in the filters of respiratory protection equipment is possible by optimizing the electrospinning process.