Construction of sustainable fully bio-based sodium alginate composite aerogels for advanced thermal insulation and fire protection

Biomass aerogels have attracted considerable attention in the field of building thermal insulation due to their low thermal conductivity and environmental friendliness. However, achieving biomass aerogels with both excellent flame retardancy and low thermal conductivity remains a significant challenge. In this study, a fully bio-based flame-retardant aerogel was constructed with sodium alginate, tannic acid and phytic acid as raw materials. The prepared aerogels exhibit a limiting oxygen index (LOI) exceeding 60 % and achieve a V-0 rating in the UL-94 vertical burning test. It demonstrates an ultra-low total heat release of 1.5 MJ/m 2 and a smoke release value of 0.97 m 2 , along with a low thermal conductivity of 0.039 W·m −1 ·K −1 . To further improve the environmental stability, the aerogel was hydrophobically modified using MTMS via a simple CVD process, endowing it with enhanced water resistance and interfacial durability. Furthermore, the synergistic interaction between tannic acid and phytic acid significantly enhances the mechanical properties of the aerogel. This study offers a novel design strategy and theoretical foundation for the development of green, efficient, bio-based gas barrier aerogel materials.