Physicochemical Characterization of Interfacial Defect Reduction in Superficially Modified Hydrophobic SiO2-Aerogel Composites

The aim of this research is to reduce the number of defects caused by the hydrophobicity of silica aerogel (SA) in the interfacial transition zone formed by this solid aggregate and a liquid binder in an alternative construction composite (paste). A new technique for controlling compatibility issues has been developed by modifying the chemicals and physical properties involved, evaluating two surfactants that function as elements that increase adhesion strength. The characteristics of wettability and free surface energy are beneficial for macroscopic morphology, microscopic structure, porosity, pore size, and physisorption, and they influence the mechanical and thermal properties of the composites. The contact angle shows that the composites obtained with the smallest SA particle size modify the wettability of the composite, increasing the contact angle to 136°, thus approaching the limit of superhydrophobic surfaces. Conversely, the composites with the large SA particles sizes decrease the angle to 94°, approaching the hydrophilic limit. The copolymer (COP) is the most efficient surfactant, achieving high surface energies, sometimes doubling those of composites integrated with only SA. Microscopy images show the presence of additional compact and homogeneous composites, with few separations and cracks. Additionally, the porosity increases to a total pore volume of 0.3376 cm 3 /g, and the specimen has an average pore size of 26.576 nm and a surface area of 50.811 m 2 /g. The compounds modified with the copolymer A3100COP and A3110COP and those modified with A3100S and silane (S) achieve great efficiency, with a mechanical strength of 5.19 MPa and a thermal conductivity of 0.141 W/(m·K) after 28 days.