Polyarylate nanofiber-enabled binder-free micro/nano dual-scale hollow nanocomposite aerogels from recycled PET for thermo-acoustic insulation

The widespread accumulation of waste polyethylene terephthalate (PET) from packaging, textile and engineering applications has posed a dual challenge of microplastic pollution and resource inefficiency, driving an urgent demand for high-value upcycling strategies. Conventional disposal routes, e.g. landfilling, incineration and low-value recycling, fail to fully exploit the intrinsic material potential of PET. Herein, we report a high value-added upcycling strategy for waste PET by converting recycled PET bottle flakes into hollow fibers via coaxial melt hollow spinning and further assembling them with self-made thermotropic liquid-crystal polyarylate (PAR) nanofibers into binder-free PET/PAR micro/nano dual-scale hollow composite aerogels through solution blending, freeze-drying and thermal consolidation. Benefiting from the secondary thermoplasticity of PAR and π-π interactions between PAR and PET, the aerogels form a hierarchically porous network with strong interfacial bonding, enabling efficient stress transfer. The synergistic regulation of heat conduction and sound propagation is achieved by (i) increasing skeleton tortuosity, (ii) inducing the Knudsen effect and (iii) promoting multiple sound scattering and cavity-induced resonance. At a PET content of 15 wt%, the composite aerogel exhibits an optimal combination of properties, i.e. a low thermal conductivity of 0.035 W·m -1 ·K -1 , an average sound absorption coefficient of 0.79, a noise reduction coefficient of 0.46, a sound pressure level reduction of ~14.2 dB and a Young’s modulus of 31.52 kPa. Moreover, it demonstrates excellent cyclic compressive stability and thermal/dimensional stability at elevated temperatures, offering a promising route toward sustainable thermo-acoustic insulation materials.