The Effect of SiO₂ Particle Size on Crystallization Behavior and Space Charge Properties for SiO₂/MMT/LDPE Composites

The matrix material used in this paper was low-density polyethene (LDPE), and the added particles selected were silicon oxide (SiO₂) particles and montmorillonite (MMT) particles. The sizes of the SiO₂ particles were 1 µm, 30 nm, and 100 nm, respectively; three kinds of SiO₂/MMT/LDPE multi-component composites were prepared based on MMT/LDPE composites doped with MMT particles. The effect of the SiO₂ particle size on the crystallization behavior and space charge properties of SiO₂/MMT/LDPE composites was studied. The crystalline behaviors and crystallinity of the materials were analyzed. At the same time, the changes in the relative dielectric constant ε_r and loss factor tanδ for each material with the influence of frequency were studied, and the space charge accumulation, residual characteristics, and apparent charge mobility of each material were explored. The results show that the smaller the size of the added particles, the smaller the grain size and the clearer the grain outline for the multi-composite material. After adding 30 nm SiO₂ particles, the crystallinity of the material increases significantly. The microstructure formed by the addition of 100 nm SiO₂ particles effectively restricts molecular chain movement and makes it difficult to establish the polarization of the composite. The incorporation of large-size particles can reduce the proportion of the crystalline structure for the material as a whole, resulting in the formation of a new structure to promote charge transfer. Among the three kinds of SiO₂ particles, the addition of 30 nm SiO₂ particles can effectively suppress the space charge, and the composite material has the lowest residual space charge after depolarization. The addition of 100 nm SiO₂ particles can cause the accumulation of many homopolar charges near the anode.