Enhanced mechanical and protective properties of silicone epoxy coatings doped with modified boron nitride nanosheets

Abstract

While organic coatings effectively prevent metal corrosion, they are prone to micro-porosity and micro-cracking during curing and can be degraded by environmental factors, reducing their protective capacity and the substrate's lifespan. Inspired by the polymer confinement effect, this study synthesizes BNNSs-PDA-TiO₂ nanocomposites to enhance the mechanical and protective properties of silicone epoxy (SE) coatings. FTIR, TGA, XPS, and TEM/EDS analyses confirm the successful growth of TiO₂ on PDA-modified BNNSs. The incorporation of these nanofillers significantly restricts polymer chain mobility, leading to notable improvements in the composite coating's mechanical and protective performance. Compared to pure SE, the tensile strength and Young's modulus of the 1 % BNNSs-PDA-TiO₂/SE composite coating increased by 91 % and 83 %, respectively. Electrochemical impedance spectroscopy (EIS) revealed that, after 6 cycles of accelerated cathodic polarization in 3.5 wt% NaCl solution, the low-frequency impedance modulus and coating resistance of the 1 % BNNSs-PDA-TiO₂/SE composite coating were three orders of magnitude higher than those of pure SE. This enhanced corrosion resistance is attributed to a dual protection mechanism: an improved passive barrier effect (strong interface and restricted polymer chains increased coating density) and the corrosion-inhibiting action of PDA and TiO₂. This study introduces the concept of polymer confinement, offering a new perspective for designing high-performance organic coatings reinforced with 2D nanocomposite fillers.