Synthesis and Characterization of Scratch‐Resistant and Hard Hybrid Sol–Gel Coatings for Polycarbonate Surfaces

Abstract UV‐curable SiO 2 ‐doped hybrid organic‐inorganic hard films were synthesized for polycarbonate (PC) substrates using the sol‐gel method. The coatings were formulated using tetraethyl orthosilicate (TEOS), 3‐(methacryloyloxy)propyl trimethoxysilane (MPTS), and crosslinking agent's diethylene glycol dimethacrylate (DEGDMA) and triethylene glycol dimethacrylate (TEGDMA) to balance mechanical durability and optical transparency. High‐purity silica particles Sibelite® M3000, M4000, and M6000 were chemically modified with MPTS to enhance their dispersion within the hybrid matrix. Among these, Sibelite® M6000 particles, at 3 µm in size, showed superior integration, forming a dense cross‐linked silicate network that enhanced mechanical and thermal properties. Incorporating modified silica nanoparticles significantly improved coating performance, achieving a pencil hardness of 8H and scratch resistance of 5 N. Fourier transform infrared (FTIR) spectroscopy confirmed the successful grafting of MPTS onto silica particles. Thermal analysis demonstrated improved stability, with modified silica coatings exhibiting lower water retention and higher residue rates above 500 °C. Optical characterization revealed that the coatings maintained over 85% transmittance and acceptable clarity, despite increased haze with higher silica content. Overall, the hybrid films provided a robust, optically transparent, and thermally stable solution for protecting PC substrates in demanding applications.