# Repair Performance of Self-Healing Microcapsule/Epoxy Resin Insulating Composite to Physical Damage
## Materials and Methods
### Materials and Preparation
#### 2.1.2 Preparation of Self-Healing Epoxy Resin Insulating Composite  
The temperature factor has a great influence on the curing reaction rate of epoxy resin and material properties. Thus, the room temperature curing system of epoxy resin-low molecular weight polyamide was selected to facilitate the operation of doping microcapsule and ensure the basic properties of insulating material. The raw materials used are all AR level.  
First, 80 parts of epoxy resin E-51 was diluted with 20 parts of epoxypropane butyl ether 660 as the matrix. Then 60 parts of room temperature curing agent polyamide, 3 parts of curing accelerator tri (dimethylamine methyl) phenol (DMP-30) and 10 parts of toughening agent dibutyl phthalate were added in matrix to obtain the epoxy room temperature curing system. After that, the microcapsule and the catalyst for core material (i.e., repairing agent) were mixed into the epoxy room temperature curing system to obtain the microcapsule/epoxy resin composite system. In addition, [PERSON] second-generation catalyst with better stability and catalytic efficiency was selected to improve the effect of self-healing. And the dosage of catalyst was 10% of the microcapsules mass.  
The composite system was mixed for 30 min at room temperature to ensure uniform dispersion. Then the bubbles in the system were removed by ultrasonic oscillation for 1 h and vacuum treatment for 20 min. Finally, it was cured for 4 days in the room temperature (\(25\pm 1\)\({}^{\circ}\)C).  
According to the relevant literature [16; 25] and my previous work (as shown in Table 1), the important basic properties (such as thermal stability, Young's modulus and tensile strength) of composite with about 1 wt. % microcapsule are more in line with the application requirements of epoxy resin insulating material.  
As the insulating material for industrial products, the thermal and mechanical properties of epoxy resin are crucial for its application. Moreover, the composite with 1 wt. % microcapsule has the best thermal stability and better mechanical properties on the premise of higher repair efficiency. Preliminary analysis shows that the effect of microcapsule on the basic properties of polyethylene is mainly related to the introduction of interface and impurities by microcapsule.  
On the one hand, the local state formed by the interface structure can anchor the macromolecular chains in the matrix material, improving the stability of matrix structure [25]. And the stable internal structure can hinder the invasion of external factors (such as thermal factor). Thus, appropriate number of interfaces can improve the properties of material (such as thermal stability). On the other hand, the excessive impurities and interface defects can increase the defect structure in the matrix material. Furthermore, the dispersion of microcapsules will be deteriorated with the increase of microcapsule concentration, affecting the properties of matrix material. Thus, higher concentration of microcapsules can reduce the properties of epoxy resin (such as mechanical properties and thermal stability). Therefore, the performances of composite are affected by the concentration of microcapsule.  
Overall, when the dosage of microcapsule was about 1% of the epoxy matrix mass, the comprehensive properties of composite are better. Thus, the more appropriate concentration (1 wt. %) was selected to study the repair performance of composite to physical damage and exclude the influence of other secondary factors.