## 3 Results and Discussion
### Analysis of Typical Performances
#### 3.2.3 Dielectric Properties
Moreover, the steering polarization of molecular chains and impurities can cause energy loss, resulting in an increase in the \(\varepsilon^{\prime\prime}\) in middle and low frequencies (as shown in Figure 9b). However, with the increase in frequency, the steering polarization cannot be established, and its energy loss becomes smaller. Therefore, the \(\varepsilon^{\prime\prime}\) of LDPE is decreased with the increase in frequency. In addition, with the decrease in crystallinity, the free volume of material is increased. Hence, the micro-structure becomes rough and loose, increasing the internal defects, which increases the depth and density of charge traps in the sample. Therefore, the relaxation loss of deep traps in LDPE with modified process is increased, and the \(\varepsilon^{\prime\prime}\) rises in high-frequency regions. Microcapsules can improve the crystallinity of the LDPE matrix, making the internal structure more compact and orderly. Moreover, the interface region between the microcapsule and LDPE matrix anchors the macromolecular chains in the amorphous region of the material (as shown in Figure 10). The anchoring effect can hinder the movement of the molecular chains or impurity groups, improving the stability of the internal structure. Thus, the steering polarization of molecular chains and polar impurity groups in the amorphous region of composite is weakened. In other words, the increase in crystallinity and the anchoring effect of the interface can reduce the polarization property and conduction loss of polyethylene matrix. Therefore, the \(\varepsilon^{\prime}\) in all frequency bands and the \(\varepsilon^{\prime\prime}\) in the low-frequency region of the composite are decreased. The interface polarization (i.e., space charge polarization) induced by the interface region between the microcapsule and the matrix was enhanced [46; 50]. Moreover, the polarization effect of the microcapsules and the catalyst particles themselves cannot be ignored. Therefore, the \(\epsilon^{\prime}\) of the composite cannot be restored to the original state, and its dielectric loss in the low- and medium-frequency regions is also higher. In addition, the interface region introduced by the microcapsule system can lead to many localized states near the conduction band and the valence band. As a result, the interface region can introduce many new charge traps (as shown in Figure 8), which leads to the increase in traps relaxation loss in the material. Therefore, the \(\epsilon^{\prime\prime}\) of the composite is increased further in the high-frequency regions. Overall, doping microcapsules can change the structural characteristics of crystalline and amorphous regions in polyethylene, and introduce impurities and interfaces. These can affect the polarization process of polyethylene, thus changing the dielectric constant and dielectric loss of the polyethylene matrix. The \(\epsilon^{\prime}\) of the composite does not fluctuate significantly in all frequency bands, and its dielectric loss (i.e., \(\epsilon^{\prime\prime}\)) is maintained at a relatively low level. Therefore, the composite can meet the basic application requirements of insulating material.