# Repair Performance of Self-Healing Microcapsule/Epoxy Resin Insulating Composite to Physical Damage
## 1 Introduction  
Epoxy resin has been widely used in the field of electrical insulating materials due to its high insulation strength, stable chemical performance, and excellent weatherability [1; 2; 3; 4]. However, in the process of manufacture, transportation, and operation, the material can be deteriorated gradually by various factors (such as electrical, thermal, and mechanical factors). The deterioration can lead to the physical damage in material, such as micro-voids and micro-cracks [4; 5; 6; 7; 8]. In addition, micro defects can distort the electric field and lead to partial discharge, reducing the insulation performance of material [9; 10; 11]. Furthermore, the existing technologies are difficult to detect and repair the damaged parts. And most methods require maintenance after the power outage [12; 13; 14; 15]. Therefore, the physical damage has a great impact on the operation of electrical power system. If the insulating material has the self-healing ability, the further deterioration of defects can be prevented in time. So, the electrical and mechanical performances of material can be restored, which can greatly reduce the impact of tiny physical damage on the power system. However, the existing research on self-healing material are mostly related to the mechanical performances of building and coating material, and rarely involve theinsulating material [16; 17]. Therefore, it is necessary to develop the self-healing epoxy resin insulating composite. It can prolong the service life of insulating material fundamentally and improve the reliability of electrical power system. Recently, the self-healing technologies are mainly divided into two types: intrinsic and extrinsic [17; 18; 19; 20; 21]. The repair behavior of intrinsic material is mainly realized by the reversible chemical reaction or the diffusion of macromolecules [18; 19]. However, the intrinsic method has higher requirements on the properties of material, and its application range has some limitations. Compared with the intrinsic material, the extrinsic material has better weatherability, wider application range and more manufacturing process [20; 21]. Moreover, among them, the microcapsule system has higher stability, better repair rate and less damage to the matrix material structure [16; 17; 21]. Considering the operation environment and repair requirements of insulating material, the microcapsule system was selected as the research object in this paper. For microcapsule/epoxy resin composite, the self-healing characteristic of electrical performances have not been involved yet, and the repair behavior is still lack of systematic mechanism [20; 21; 22]. At present, there are few reports about self-healing insulation material. In the aspect of simulation, the static stress distribution of the microcapsule used for epoxy resin insulating material was simulated [2]. The results confirmed that the internal stress of insulating material can lead to the rupture of the microcapsule, thereby completing the repairing behavior. However, it does not involve the repairing ability of actual insulating material. In terms of experiment, the ability of microcapsule to repair electrical tree damage in epoxy resin was studied [23]. The results showed that the microcapsules can delay the development of electrical trees. But the change rules and mechanism of repair performance are still insufficient. In addition, the migration behavior of superparamagnetic nanoparticles was used to repair the electrical tree damage in polymers [24]. However, this method requires the stimulation of an external magnetic field, which belongs to the inductive repair system. There is still a certain gap with the active self-healing target of insulating material. Therefore, the research on the self-healing epoxy resin insulating material remains to be deepened. In this paper, based on the preparation of microcapsule/epoxy resin composite, its self-healing performance to physical damage was analyzed by the tests of scratch, cross-section, electric tree, and breakdown.