Melt-blowing and crystallization of high-performance Polylactic acid (PLA) nonwovens for air filtration

The growing need for sustainable, high-efficiency filtration materials has driven interest in biodegradable alternatives to polypropylene (PP)-based nonwovens, which dominate global production but generate severe environmental burdens. This study presents a comprehensive investigation of additive-free, low-viscosity biodegradable polylactic acid (PLA) melt-blown nonwovens, establishing relationships between processing parameters, fiber structure, crystallization, and electrostatic charging performance. Across 135 experiments, we reveal that die geometry, die-to-collector distance, polymer throughput, air pressure, and temperature jointly determine fiber morphology and crystallinity of PLA melt-blown nonwovens, thereby affecting the filtration performance. Clear process–structure–performance connections for PLA nonwovens were defined. PLA nonwovens with submicron fibers achieving >95% filtration efficiency at <160 Pa pressure drop were fabricated without post-charging, demonstrating the feasibility of scalable, biodegradable filter media. X-ray diffraction and thermal imaging reveal that in situ crystallinity can be tuned by air pressure, polymer throughput, and collection speed, which enhances thermal stability and supports long-term charge retention. Two-month charge decay tests further identify fiber diameter as the dominant factor in electret stability, with crystallinity playing a secondary but reinforcing role. By combining systematic experimentation with mechanistic insights, this work offers practical guidance for industrial-scale manufacturing of high-performance PLA nonwovens and advances the development of next-generation sustainable air filtration media.