Preparation, characterization and antibacterial properties of hydro-charged melt-blown nonwovens coated with an N-halamine†

Air filtration materials can protect humans from the invasion of airborne pathogens. However, pathogens intercepted by air filters can survive in fibrous materials and pose a threat to human health if they proliferate in large quantities. Therefore, in this work, modified hydro-charged polypropylene (PP) melt-blown nonwovens with antibacterial properties were prepared to reduce the infection rate during the filtering process. Firstly, PP_m electret melt-blown nonwovens containing 5 wt% electret masterbatch PP-MgSt were prepared by the melt-blown process and hydro-charging technology. Then, an N-halamine compound, 1-chloro-2,2,5,5-tetramethyl-4-imidazolidinone (MC), was used for antibacterial modification. MC was evenly coated on the surface of the melt-blown fibers by spraying and dipping processes to obtain PP_m/MC-s and PP_m/MC-d melt-blown samples, respectively. The PP_m/MC-s and PP_m/MC-d samples demonstrated excellent antibacterial properties, killing 99.99% of E. coli and S. aureus in 5 and 10 minutes of contact times, respectively. However, the filtration results indicated that the surface coating treatment reduced the filtration efficiency of both samples to varying degrees. Specifically, the filtration efficiency of PP_m/MC-s decreased from 99.64% to 94.77%. Due to the excessive use of ethanol during the PP_m/MC-d modification process, more electret charges escaped, resulting in a significant decrease in filtration efficiency to 69.66%. Comprehensive analysis proposed that melt-blown nonwovens that have already been processed and formed are more suitable for MC antibacterial modification by spraying method. The modified melt-blown samples can provide strong antibacterial effects while maintaining high filtration efficiency and low pressure drop. This work provides a feasible industrialized antibacterial modification method for formed melt-blown filtration nonwovens, which can further improve the protective performance of traditional filter products.