Regulation of polylactic acid using irradiation and preparation of PLA-SiO2-ZnO melt-blown nonwovens for antibacterial and air filtration

Since the COVID-19 pandemic, polypropylene melt-blown nonwovens (MBs) have been widely used in disposable medical surgical masks and medical protective clothing, seriously threatening the environment. As a bio-based biodegradable polymer, polylactic acid (PLA) has attracted great attention in fabricating MBs. However, there are still issues with the undesirable spinnability of PLA and the limited filtration and antibacterial performance of PLA MBs. Herein, a high-efficiency, low-resistance, and antibacterial PLA filter is fabricated by melt-blown spinning and electret postprocessing technology. The irradiation technique is used to tune PLA chain structure, improving its spinnability. Further, silica (SiO2) nanoparticles are added to enhance the charge storage stability of PLA MBs. With a constant airflow rate of 32 L min(-1), the PLA-based MBs exhibit a high particulate filtration efficiency of 94.8 +/- 1.5%, an ultralow pressure drop of 14.1 +/- 1.8 Pa, and an adequate bacterial filtration efficiency of 98 +/- 1.2%, meeting the medical protective equipment standard. In addition, the zinc oxide (ZnO) masterbatches are doped into the blend and the antibacterial rate of PLA-based MBs against Escherichia coli and Staphylococcus aureus is higher than 99%. This successful preparation and modification method paves the way for the large-scale production of PLA MBs as promising candidates for high-efficacy and antibacterial filters.