In situ natural-ester-grafted coating extends cellulose insulation paper service life: Hydrophobicity and thermal-aging resistance for high-voltage equipment

Cellulose insulation paper, with excellent insulation and mechanical properties, plays a vital role in oil-paper insulation systems of power equipment. Moisture intrusion and thermal aging are two major challenges that significantly compromise its performance. Combined enhancement of hydrophobicity and thermal-aging resistance in a synergistic manner is key to achieving greater durability and extended service life. This paper proposes a vegetable oil-based microscopic surface grafted coating strategy to modify cellulose insulation paper by applying a functional layer onto the macrofibrils surface inside the porous cellulose paper. The designed modification process occupies hydrophilic sites of cellulose and creates micro-nano natural ester shielding on the surface, resulting in simultaneous improvements in both hydrophobicity and thermal-aging resistance. The modified insulation paper exhibits external water contact angle of 120.1°, reduced internal moisture adsorption, and slower polymerization degree decay during accelerated thermal aging process. Additionally, electrical properties are maintained or improved due to the kept porous network structure. This micro-interface-targeted and process-simple approach retains the advantages of vegetable oils without the limitations of bulk vegetable oil impregnation, thereby significantly extending the service life of insulation paper. Moreover, this strategy offers a transferable route for engineering porous cellulose materials operating under complex conditions, providing valuable insights for the environmentally friendly and intelligent development of electrical power equipment.