Design of Environmentally Friendly Sound-Absorbing Composites with Multi-scale Pore Size Based on Porous Polylactic Acid Nanofibers

Abstract

With the rapid advancement of global industrialization and population explosion, noise pollution has seriously threatened human survival and social development. Fibrous porous sound-absorbing materials are widely utilized in the transportation field due to their high sound absorption abilities, cost-effectiveness, ease of fabrication and lightweight properties. However, materials designed to combat pollutants should not become new sources of pollutants. In response, environmentally friendly fibrous sound-absorbing materials based on polylactic acid (PLA) were developed. The electrospun porous polylactic acid (PLA) nanofibers were combined with PLA needle-punched nonwovens through vacuum filtration and freeze-drying to prepare PLA sound-absorbing composites with a hierarchical structure and multi-scale pore size. The results revealed that increasing the vacuum filtration time reduced the thickness of PLA composites with different PLA nanofiber solid contents, with all samples maintaining a thickness below 10 mm. The average sound absorption coefficients (SACs) of the composites were also significantly affected by the nanofiber solid contents, with PLA_0.7–40 composites achieving an average SACs of 0.33. When the nanofiber solid content reached 0.70 wt.%, the PLA composites exhibited the highest sound absorption coefficient (α) at different filtration times, with the maximum α shifting toward lower frequencies as filtration time increased. Notably, the α values of PLA_0.7 and PLA_1.0 composites at medium frequencies improved considerably, with α₁₀₀₀ values reaching 0.30 and 0.35 for PLA_0.7–40 and PLA_1.0–40 composites, respectively.