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

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.