Preparation of Epoxy-Enhanced Silica Aerogels with Thermal Insulation and Hydrophobicity by Ambient Pressure Drying

Abstract

The SiO₂ aerogel is attractive for thermal insulation but is plagued by poor mechanical and high drying process costs. Therefore, there is an urgent requirement for developing a low-cost, low-density, low-thermal conductivity, and hydrophobic monolithic SiO₂ aerogel with high strength. This work reports two epoxy-enhanced amine-modified silica aerogels (AMSA). One type is to utilize 3-aminopropyl-triethoxysilane (APTES) and tetraethylorthosilicate (TEOS) to synthesize AMSA first, ensured to be crack-free by introducing ionic liquids (IL) into the reaction system, and then cross-link with epoxy resin to obtain composite aerogels with a framework structure by a two-step enhancement gel network strategy (TES-AMSA). Composite aerogels are thermally insulating and hydrophobic, the maximum compression strength of TES-AMSA reaches 3.97 MPa, and the minimum thermal conductivity and maximum water contact angle (WCA) are 0.031 W m^–1 K^–1 and 137°, respectively. Another way is to add epoxy resin as a reinforcement to the solvent system before forming the gel network without the role of IL. A composite aerogel like the brick structure by a one-step enhancement gel network strategy (OES-AMSA) was produced under atmospheric pressure drying. The maximum compression strength of OES-AMSA reached 1.57 MPa. In addition, OES-AMSA also has a low thermal conductivity (0.035 W m^–1 K^–1) and a high WCA (143°). Two composite aerogels provide insight for the designing of pressure-resistant insulation materials, aiming to use them as an insulating material for crude oil storage tanks, ultralow-temperature refrigerators, and construction materials.