Vapor/Condensed phase synergistic flame retardancy in core-shell structure electrospun nanofiber membranes with low-frequency sound absorption

Fire safety and low-frequency noise pollution have become two critical challenges restricting the development of healthy and safe green buildings. Traditional organic sound-absorbing materials widely used in construction suffer from inherent flammability, releasing large amounts of toxic smoke during combustion and posing severe threats to personnel safety, while their low-frequency sound absorption efficiency remains unsatisfactory. In this study, multifunctional A-PAN/PVP@Cu electrospun nanofibrous membranes (ENMs) with core-shell structure were fabricated via coaxial electrospinning followed by sequential hydrazine hydrate reduction and copper ion loading modification. The optimal A-PAN/PVP@Cu-2H sample exhibited excellent flame retardancy with 76.5% reduction in peak heat release rate, 80% reduction in total heat release, and 66.7% reduction in maximum smoke production rate compared to pristine PAN/PVP ENMs. Thermogravimetric-infrared analysis and XPS characterization revealed that copper-based components catalyzed the formation of dense copper oxide-carbon composite protective layers in the condensed phase and scavenged free radicals in the gas phase, achieving synergistic flame retardancy and smoke suppression. Meanwhile, the hierarchical pore gradient derived from the core-shell structure and the rough surface decorated with copper nanoparticles synergistically enhanced sound energy dissipation through viscous friction and multiple scattering, achieving an average low-frequency sound absorption coefficient of 0.46 and a minimum full-frequency absorption coefficient of 0.27, meeting the requirements of building sound-absorbing materials. This work provides a promising strategy for developing integrated fire-safe and acoustic-comfortable building materials, which have broad application prospects in interior decoration of subways, commercial complexes and residential buildings.