Synthesis of poly(urea–formaldehyde) microcapsules for the self‐healing system of silicone rubber insulating material

Abstract Silicone rubber is used as an antipollution flashover material in outdoor insulation, which is susceptible to aging and has a shorter service life than other candidates. Microcracks are a common aging phenomenon that are difficult to be detected and repaired. The microcapsule self‐healing technology can be used to repair microcracks and extend the service life of silicone rubber. This study considers hydrogen silicone oil as a representative of the polydimethylsiloxane healing agent system. Poly(urea–formaldehyde) microcapsules containing the hydrogen silicone oil are synthesized by in situ polymerization. The effects of the emulsifier concentration, initial pH value, initial ratio of the core–shell material, and sodium chloride (NaCl) concentration on the synthesis are investigated. Accordingly, the properties of the microcapsules before and after long‐term storage are analyzed. The results demonstrate that microcapsules synthesized using poly(ethylene‐alt‐maleic anhydride) (EMA)+ polyvinyl alcohol (PVA) as the emulsifier have satisfactory morphology and performance, where the best synthesis conditions are 0.13 wt% EMA, 0.05 wt% PVA, initial ratio of the core–shell material of 1.5:1–2.0:1, initial pH value of 3.5–4.0, and 2 wt% NaCl. In long‐term storage, the core material is well protected by the shell material. The synthesized microcapsule can serve as a material in the self‐healing system of silicone rubber.