Constructing a Double Crosslinking Structure on Spherical Silica Powder for Enhancement in the Interfacial Adhesion of Epoxy Composite

Spherical silica powder (SSP), which exhibits excellent fluidity and resistance to chemical corrosion, has been widely used to reinforce epoxy (EP). However, the inherent polarity discrepancy between SSP and EP gives rise to weakened interfacial bonding properties, which would compromise the overall performance of the EP composite. Here, to enhance the interfacial bonding of the composite, a double crosslinking structure was constructed between SSP and EP by coating Metal‐polyphenol network‐silane coupling agent (MPN‐SCA) on the SSP surface. The “double crosslinking” structure not only improves the mechanical properties but also enhances the thermal and dielectric properties. Specifically, surface chemistry analysis revealed that the MPN‐SCA layer was successfully coated on the SSP surface. The flexural strength and thermal conductivity of the SSP/EP composite achieved 45.7% and 120.0% increases, respectively, compared to the pure EP. Electrical measurements demonstrate that the “double‐crosslinking” architecture effectively reduces both the dielectric constant and dielectric loss of SSP/EP composites. This study offers meaningful guidance for designing strategies to enhance interfacial adhesion in spherical silica powder/epoxy composites while simultaneously optimizing their functional performance.