Guar-based aerogels with oriented lamellar structure and lightweight properties for flame-retardant and thermal...

In this study, a multi-functional guar gum aerogel with the oriented lamellar structure, which introduced sodium silicate (Na₂O·nSiO₂) and phytic acid (PA) as thermal insulation additives and flame-retardant agents, respectively, was fabricated via freeze drying. Our aerogel's chemical structure, morphology, and thermal and mechanical properties were analyzed. The oriented lamellar structure was attributed to the orientated growth of ice crystals, which was induced by the "silicate-guar, guar-phytate, and phytate-silicate" multiple hydrogen bonds formed between Na₂O·nSiO₂, PA, and guar gum. The density of the sample with 2 wt% PA could reach 0.0335 g·cm^-3, and the porosity was 5 %, along with a specific pore volume of 0.8144 cm³·g^-1. The mechanical properties and thermal insulation performed significant differences in the radial and axial direction of the oriented lamella (nearly 100 % resilience while 50 % deformation quantity and 0.0235 W/(m*K) of thermal conductivity in the radial direction, up to 0.079 MPa of compressive strength in the axial direction). The presence of PA attached a good flame-retardant ability to our aerogel (The Limiting Oxygen Index (LOI) was 30.77 %). This work provides a novel and promising method for developing anisotropic aerogel with excellent potential in building energy efficiency and flame-retardant.