Preparation and Characterization of Lightweight, Hydrophobic, and Insulative Melamine Foam/Fumed Silica Composites

Nanoparticulate silica is renowned for its excellent thermal insulation and low density; however, it faces challenges in practical applications due to high production costs and poor mechanical properties. In this study, a lightweight, hydrophobic, and insulative composite consisting of fumed silica and melamine foam (MF-FS) was prepared by using an atmospheric impregnation and drying process. Four different concentrations of fumed silica (5, 10, 15, and 20%) were systematically incorporated into the melamine foam to assess their effects on the composite's performance. The microstructure, thermal insulation, and sound absorption properties of the resulting materials were characterized. Mechanical tests showed that the addition of fumed silica enhanced the tensile strength of the composites, and the optimal concentration was 15%. Thermal conductivity measurements showed that the room temperature thermal conductivity of the composites decreased with an increasing fumed silica content, reaching a minimum of 26.24 mW/m·K at 15% fumed silica. Sound absorption tests indicated significant improvements in sound insulation attributed to the increased complexity of sound wave propagation paths within the composites. Additionally, the composites exhibited excellent water repellency, which is crucial for maintaining long-term thermal insulation efficiency in humid environments. These findings suggest that MF-FS composites have substantial potential for thermal insulation and soundproofing applications, particularly in the power battery and construction industries, where there is a high demand for cost-effective and high-performance materials.