Earthworm-inspired mechanical toughened biodegradable polylactic acid microfiber for sustainable air filtration

Fully renewable and biodegradable polylactic acid (PLA) microfiber filters are attractive candidates for traditional unsustainable filters due to their unique advantages of maintaining mechanical strength while in service and rapidly degrading after waste. However, the toughness of sustainable PLA melt-blown microfibers (PLAMFs) with high polymeric chain orientation is poor, which makes it difficult to meet the requirements of air filtration applications. Here, a facile but effective polymeric chain limited domain rearrangement (PLR) strategy inspired by earthworms is developed to toughen PLAMFs. In this process, the short-time and high-temperature heat treatment can quickly break the original hydrogen bonds between polymeric chains and form new ones, which stimulates the thermal movement of polymeric chains from the low entropy position to the high entropy position, resulting in the intrinsically toughening of PLAMFs while maintaining strength. The resulting PLR-PLAMFs and PLR PLA melt-blown nonwovens (PLR-PLAMNs) exhibit enhanced toughness of 146.32 MJ m−3 (an increase of 143.99 %) and 0.80 MJ m−3 (an increase of 66.67 %), respectively. Moreover, toughened PLA melt-blown nonwovens (PLAMNs) after corona electret (CE) treatment exhibit high filtration efficiency (>90.00 % PM0.3 removal) and extremely low pressure drop (<0.02 % atmospheric pressure), which is highly promising for application in sustainable air filtration.