Electrostatic Properties of Nonwoven Masks Made of Polylactic Acid

Polylactic acid (PLA) is an emerging biodegradable alternative to the standard filtering materials such as polypropylene (PP) used for, e.g., surgical masks. Although static electricity was shown to improve its filtering performance similarly to the case of PP, its efficiency, distribution, retention time, etc. were understudied. In this work, by leveraging our recent development of the "mask charger", we report that PLA melt-blown sheets can be charged by the application of a high voltage similarly to PP, yet the fact that PLA is slightly less hydrophobic compared to PP makes it more susceptible to humidity during charging. Once charged, PLA retained its static electricity over a few days in open air. Importantly, neither sandwiching the PLA sheet with two spun bond sheets (protective layers) nor folding into zigzag configurations hindered the charging procedure, which highlights the possibility to charge it in the commercial surgical mask format. Finally, the particle filtration efficiency (PFE) test revealed that the static electricity boosted the filtering performance of these PLA sheets, e.g., from 92% to 96%. The data reported in this work will help with optimizing the production and application of biodegradable PLA-based filters in various fields and will contribute to reduce the environmental plastic pollution in the long run.