Magnetically Targeted <scp>UV</scp> ‐Shielding Microcapsules for Self‐Healing of Electrical Treeing in Dielectric Polymers

ABSTRACT Electrical treeing, an irreversible degradation process in dielectric polymers under high electrical stress, critically threatens the reliability of power equipment by propagating undetectable damage. To address this challenge, magnetically responsive microcapsules were developed for targeted electrical tree repair. These microcapsules are magnetically positioned within dielectric encapsulants and engineered with a higher dielectric constant than the host matrix to guide electrical trees toward microcapsule rupture. The core‐shell structure integrates: (i) a hybrid healing agent (photosensitive hyperbranched polyurethane acrylate/epoxy resin) and (ii) functional shells incorporating Fe 3 O 4 @SiO 2 nanoparticles for magnetic navigation and titanium dioxide/graphitic carbon nitride (TiO 2 /g‐C 3 N 4 ) for UV‐shielding. During electrical tree propagation, electroluminescence triggers polymerization of the released healing agent, enabling autonomous crack‐sealing. Optimized microcapsules achieve 75% encapsulation efficiency with uniform size distribution (~100 μm). After optimization, a doping concentration of 4 wt% was identified as optimal, at which the composite exhibited a peak tensile strength of 37.54 MPa (compared to 36.21 MPa for the neat resin) and a minimal reduction in breakdown voltage to 36.4 kV (from 37.2 kV). In situ optical microscopy confirms effective damage repair during tree growth, demonstrating a precision self‐healing strategy that extends service life without compromising intrinsic material properties.