Dielectrically Graded Photocurable Nanocomposite Coating for Achieving Enhanced Surface Insulation and Long-Term Stability

Surface functionally graded material (SFGM) exhibits novelty and effectiveness in mitigating the catastrophic surface flashover of solid insulation. However, existing SFGMs mainly rely on sophisticated, time-consuming fabrication procedures, and usually demonstrate an inadequate long-term stability. This study developed a convenient, scalable SFGM fabrication method utilizing ultraviolet light (UV) curable coating, which has simplified processing, high flashover voltage (FOV), and strong adhesion to epoxy matrix. The coating material is a mixture of photocurable acrylic resin and perfluoro-silane-treated BaTiO3 (BT) nanoparticles, whose component formula and UV-curing technique were optimized according to the rheological and photocuring properties. The insulation performance of UV-SFGM was studied by flashover tests in a compressed gaseous medium. Long-term stability was investigated by the tests of interfacial adhesion, thermal cycling resistance, and hydrofluoric acid (HF) erosion tests. Experimental results show that FOV of UV-SFGM increases by 21.94% in 0.3 MPa SF6, which is attributed to the effective reduction of the maximum electric field. As for the long-term stability, the UV-SFGM has strong adhesion to epoxy/Al2O3 substrate (cross-cut level 5B and 6.54 MPa pull-off strength), especially when surface roughening on the substrate is carried out. Moreover, good resistance to thermal cycling and HF erosion is observed in the photocurable coatings. In summary, the proposed UV-SFGM has an accurate and efficient fabrication process, high insulation performance, and good long-term stability, making it promising in industrial applications.