Chitosan/clay aerogel: Microstructural evolution, flame resistance and sound absorption

Different porous structures of biomass-based aerogels were regulated by adjusting the ratios of carboxymethyl chitosan (CCS) and montmorillonite (Mt). The hierarchically porous structures were obtained via a directional freeze method and the freeze-drying process. The diverse microstructures and flame retardant and sound absorption properties of as-prepared CCS/Mt. aerogels were studied. The results revealed that the incorporation of Mt. could dramatically improve the flame retardancy of the resultant aerogel, with the limiting oxygen index reaching up to 85%, attaining the nonflammable level. And the CCS/Mt. aerogels exhibit a super low density (33.85–38.27 mg/cm3) and high porosity (98.20%). The honeycomb-like structure of the aerogel could apparently improve the sound adsorption properties at low-frequency. Overall, this work provides a novel approach to develop bio-composites featured with excellent flame retardant and sound-adsorption properties that would find a broad range of potential applications as building material.