Service Durability of PLA Melt-Blown Nonwovens: Roles of Humidity and Airflow Velocity in Degradation and Filtration Performance

The energy and environmental challenges associated with petroleum-based nonwovens have driven interest in renewable alternatives such as polylactic acid (PLA)-based melt-blown materials. However, their air filtration performance is highly sensitive to service conditions due to environmental degradation. This study investigates the physicochemical structure changes and application performance of PLA melt-blown nonwovens based on a full factorial design of service conditions combining humidity, airflow velocity, particulate matter, and natural microbes. Results showed that PLA melt-blown nonwovens exposed to service conditions remain in the early stage of degradation and follow first-order kinetics, with a rate constant up to 3.88 × 10–2 h–1, accompanied by a mechanism dominated by surface degradation and erosion. A qualitative correlation between the fiber surface degradation mechanism and nonwoven filtration performance was established based on filter cake formation theory and fiber microstructural changes. Two-way analysis of variance revealed that humidity acts as the primary driver of degradation by progressively shifting its influence mechanism from moisture absorption (accounting for 90% of the variance in short-term WCA-30s) to severe mechanical erosion and pressure drop (explaining 77% of the variation in yield strength and 91% in pressure drop in the long term). Meanwhile, airflow velocity governs dynamic filtration performance by determining particle-media contact efficiency and inertial impaction, contributing 57% to the variance in filtration efficiency and 52% to the quality factor in the long term.