CNC ‐Enhanced Carboxymethyl Chitosan Aerogel for Sound Absorption, Flame Retardancy, and Antibacterial Properties

ABSTRACT In the process of noise pollution control, the limitation of simply relying on increasing the thickness of the sound‐absorbing layer has been recognized. Aerogel, due to its lightweight and multifunctional characteristics, has become a research hotspot. However, how to optimize the structure of aerogels to balance sound‐absorption performance with other key characteristics remains an important research direction. In this study, by in situ combining zinc borate (ZB) nanoparticles and directional freezing technology, the optimal incorporation amount of nanocellulose (CNC) was explored, and CNC/ZB/carboxymethyl chitosan aerogel with honeycomb pore structure and excellent sound absorption effect was prepared. In order to expand its application in complex scenes, its antibacterial and flame retardant properties were further studied. The experiments demonstrated that the optimized incorporation of CNC not only enhanced the sound‐absorbing performance (with the peak of sound absorption coefficient in the 500–1500 Hz frequency band approaching 1), but also maintained an antibacterial rate of over 97% and a combustion rate as low as 0.76 mm s −1 . This sound‐absorbing aerogel integrates efficient sound absorption, mechanical strength and toughness, as well as antibacterial and flame‐retardant properties, providing a new material design concept for addressing environmental noise and health and safety issues.