Fabrication of multifunctional hydrophobic silica aerogels with superior thermal safety enabled by a dual flame-retardant strategy

Hydrophobic silica aerogel (HSA) represents a promising thermal insulating material for addressing challenges from climate change and energy consumption. However, its susceptibility to high-temperature sintering and flammability limits its application scope. Herein, a thermal safety regulation strategy was proposed through hypophosphorous acid catalysis and the incorporation of flame-retardant modified halloysite nanotubes. The resulting HSA composite exhibited improved fire resistance, with 16.6 % and 15.5 % reductions in peak of heat release rate and total heat release, respectively. Additionally, after prolonged thermal attack at 800 °C, the skeleton structure of the aerogel remained stable, showing no collapse. Furthermore, the enhancement of the thermal safety of the aerogel did not decrease the hydrophobicity (water contact angle of 142.9°) and heat insulation properties (thermal conductivity of 22.4 mW/m·K). This study provides valuable insights into optimizing the thermal safety of HSA, which broaden its applications in thermal insulation with fire protection requirements.