Hydrophobic phenolic/silica aerogel composites with high fire safety and strength for efficient thermal insulation

To develop a polymer-based aerogel composite with excellent fire safety and strength for efficient building insulation, hydrophobic phenolic/silica aerogel composites (PSACs) were synthesized using a facile, self-catalyzed sol-gel process based on co-condensation of resorcinol (R), formaldehyde (F), and 3-(aminopropyl)triethoxysilane (A). The hydrophobicity was achieved via the gas-phase modification of the aerogels. The hydrophobicity and thermal conductivity of the PSACs are governed by the R/A ratio and aerogel density, respectively. A glass fiber paper-reinforced PSAC with an R/A ratio of 2 and an aerogel density around 0.10 g cm^-3 (GP/RA21-10) exhibits a high water contact angle of 138°, a low thermal conductivity of 0.021 W m^-1 K^-1, and a high strength (1.67 MPa of compression strength, 2.54 MPa of tensile strength, and 1.65 MPa of flexural strength). GP/RA21-10 exhibits significantly superior thermal insulation properties compared to commercially available insulation materials, including thermosetting polystyrene board, silica aerogel coating board, and rock wool. GP/RA21-10 is flame-retardant and high-temperature resistant and demonstrates superior fire safety during building insulation. The design presented here offers important guidelines for the advancement of high-performance building insulation materials.