Superior broadband sound absorption in hydrophobicity and mechanical enhancing Poly(urethane-imide)/Melamine aerogels via ambient drying

Noise pollution has been recognized as having negative impacts on human psychological and physiological health. Common porous sound-absorbing materials are often limited by low sound absorption coefficient (SAC), excessive thickness, and poor moisture resistance or mechanical properties. Herein, poly(urethane-imide) and melamine foam (MF) were successfully combined for the first time using hydrothermal synthesis and ambient drying to fabricate a poly(urethane-imide)/melamine (PUI/MA) aerogel with a multi-stage pore structure and a core-shell framework. The introduction of PUI reduces pore size and increases tortuosity, thereby enhancing thermal and viscous losses of sound waves. Compared to unmodified MF, the noise reduction coefficient of PUI/ MA aerogel achieves an 80 % improvement. Furthermore, numerical microstructural modeling calculations show that the JCA model's predictions are more consistent with the SACs of PUI/MA aerogels. In addition to significantly improving SAC, the core-shell structure endows the composite aerogels with a compressive Young's modulus up to 30 times that of MF, a water contact angle over 120 degrees, and a thermal conductivity of less than 60 mW/m/K at 150 degrees C. The facile and cost-effective fabrication process, superior broadband sound absorption, and excellent fundamental properties suggest that PUI/MA aerogel is a promising candidate for noise mitigation in residential, rail transport, and industrial applications.