Three-level gradient design for high-performance waterborne sodium silicate wood coatings and the interfacial bonding mechanism

Abstract

To address the limitations of conventional sodium silicate coatings—high water solubility, poor adhesion, and single functionality, this study introduces a three-stage gradient strategy of “molecular bridging-micropore filling-functional coupling.” Using a sodium silicate solution as the base material, a sodium silicate-polyvinyl alcohol composite coating was prepared via organic–inorganic hybridization. Further, the modified coating was strengthened by introducing nano-SiO₂ modified with silane coupling agent KH550, thus constructing a high-performance water-based composite coating system. Results show that through the molecular regulation of KH550, spatial orientation of its organic and inorganic ends is achieved, effectively suppressing nano-SiO₂ agglomeration and establishing a molecular-level connection at the wood-coating interface; Nano-SiO₂ fill coating micropores, significantly increasing cross-linking density and mechanical properties; Through the synergistic effect of the Nano-SiO₂/PVA/2NH₂-PDMS composite system, a “rigid Si-O-Si and type siloxane” dual-network structure is constructed, addressing the shortcomings of traditional coatings being hard and brittle; The composite exhibits outstanding performance: enhanced mechanical properties (wear resistance: 0.083 g/r, hardness: 6H), adhesion meeting Grade 1 standard, essentially no residual contamination from cola, soy sauce, or sesame oil, and rapid, smokeless self-extinguishment. It fully meets application requirements in furniture, interior decoration, and construction, offering a new approach for high-value utilization of bio-based materials.