Sol–Gel CaCO3/SiO2 Boost Anti-Flashover Silicones

This study developed high-performance anti-flashover silicone coatings using sol–gel-synthesized CaCO3/SiO2 hierarchical fillers optimized via L16(45) orthogonal design. The optimal filler (Sample 5) was prepared under 70 vol% ethanol, with nTEOS:nCaCO3 = 1:1 and 0.2 mol/L NH3·H2O, at 45 °C, for 18 h, featuring covalent Si-O-Ca bonding, a dual-scale microstructure (2–4 μm CaCO3 cores + 20–40 nm SiO2 nodules), a 14.44 m2/g specific surface area, and bimodal porosity (8–80 nm). Composite C7 (30 wt% filler, 3 wt% KH-570, 1:2 resin-to-filler ratio) achieved superhydrophobicity (a 153° contact angle via Cassie-Baxter stabilization), ultrahigh electrical insulation (3.20 × 1014 Ω·cm volume resistivity, 1.60 × 1013 Ω surface resistivity), and robust mechanical properties (Shore 3H hardness, 5B adhesion). Standardized IEC 60507:2020 tests showed that C7’s flashover voltages (14.8 kV for KMnO4, 14.3 kV for NaCl/KMnO4, 13 kV for NaCl) exceeded that of neat silicone resin (NSR) and conventional CaCO3-filled composite (SR-CC) by >135%. Additionally, C7 retained superhydrophobicity after 500 h UV aging and maintained a 124° contact angle after 12 months of outdoor exposure. The superior performance stems from synergistic hierarchical topology, tortuous discharge paths, and interfacial passivation. This work establishes a microstructure-driven design paradigm for grid protection materials in harsh environments.