Synthesis of SiO2 Nanoparticles from Two Precursors to Fabricate Polyurethane/SiO2 Aerogels for Applications as Thermal Insulators

In order to address the issues of weak interface bonding, poor structural stability, and difficulty in simultaneously optimizing functional performance of traditional silica (SiO2) aerogel materials, and to further expand the application of SiO2 aerogels in the field of building energy conservation, 3-aminopropyltriethoxysilane (APTES) and tetraethoxysilane (TEOS) were used as cosilicon sources in this study. On this basis, polyurethane foam (PUF)/SiO2 aerogel composite phase-change materials (PFSA-X) with different APTES/TEOS molar ratios were prepared by vacuum impregnation and freeze-drying technology. The effects of the APTES ratio on the nanostructure and properties of the composites were systematically investigated. Studies have shown that when n (APTES):n (TEOS) = 0.3, APTES can give full play to the role of a “molecular bridge” and a “network regulator” to construct an organic–inorganic hybrid system with dense nanostructures and strong interface bonding. Thanks to this nanostructure feature, PFSA-0.3 exhibits a high phase-change enthalpy (350.7 J/g), a low thermal conductivity (0.028 W/(m·K)), high compressive strength, excellent thermal stability, and significantly improved flame retardant and smoke suppression properties. This study not only provides ideas and experimental basis for the nanostructure design of high-performance composite phase-change materials but also lays a foundation for its application in the fields of building energy conservation and high-temperature thermal protection.