Combination Strategy of Melt-Blowing and Breath-Figure Enabling Scale-Up Production of Hierarchically Structured Polylactic Acid (PLA) Nonwovens for Durable and Efficient Air Filtration

Abstract

Biodegradable polylactic acid (PLA) melt-blown nonwovens (MN) are regarded as the promising alternatives for petroleum-based air filtration mediums. However, the filtration performances of most PLA MN were greatly relied on their electrostatic effects which would suffer from inevitable attenuation caused by environment conditions during long-term storage. Herein, the innovative combination of breath-figure (BF) and melt-blowing technologies was proposed to prepare the hierarchically structured PLA MN-bearing BF net pattern (PMBP) for enhanced air filtration. Initially, melt-blowing technology was employed to conduct large-scale preparation of PLA MN with a low-pressure drop of 25.7 Pa but an unsatisfactory PM_2.5 (aerodynamic diameter below 2.5 μm) filtration efficiency of 59.5%. At the optimized BF processing conditions involving polymer concentration of 0.5 wt% in hexafluoroisopropanol and relative humidity of 50%, the resultant BF net pattern exhibited uniformly microporous structure with the average pore size low to 1.02 μm. The integration of large-pore PLA MN and small-pore net pattern endowed PMBP with hierarchical structures, which induced PMBP displaying excellent filtration performances (filtration efficiency of 95.8% and pressure drop of 39.3 Pa), and eliminating over 99% of PM_2.5 particles within 3 min in the actual smoke test, even without the benefit of static charges. The filtration performances of the PMBP remained stable in high-humidity environments and during long-term storage. Furthermore, the PMBP also exhibited exceptional self-cleaning properties. Overall, this work opens up a promising approach to develop fully bio-based and high-performance filtration materials with hierarchical structures.

Graphical Abstract