Investigation On Dielectric Properties Of ZnO/LDPE Composites

Polyethylene is widely used because of its excellent insulation properties in thermoplastic insulation materials. However, with the development of industry, more and more requirement has emerged from engineering application. Many scholars add inorganic fillers into LDPE to form new composites for the idea of developing new superior dielectric materials by controlling the morphology of composites and revealing the relationship between the mesoscopic structure and macroscopic properties of composites.This paper uses low density polyethylene(LDPE) as matrix, nano-ZnO and micro-ZnO as additives. ZnO/LDPE nanocomposites, ZnO/LDPE microcomposites, ZnO/LDPE micro-nanocomposites with different contents of inorganic particles are prepared through two-step melt-blending processes. The modified ZnO particles were characterized by FTIR, the result shows that coupling agent has been attached to the surface of nano-ZnO particles. Crystalline state and the crystallization process of composite materials were observed by PLM and DSC. Then we found that ZnO particles make the size of polyethylene crystalline smaller and the structure more compact. and increase the crystallization rate, melting temperature, and crystallinity. Especially with the same filler content, the melting temperature and crystallization rate of microcomposite is highest, crystallinity of micro-nanocomposite is highest.DC conductivity and AC breakdown measurements of pure LDPE and ZnO/LDPE composites are carried out. The results show that the sequence of four composites` conductivity from low to high is micro-nanocomposite, nanocomposite, pure LDPE, microcomposite, and the sequence remains still the same at high temperature. The nano-ZnO improve the AC breakdown strength of LDPE, the micro-ZnO decreases on the contrary, The AC breakdown strength of microcomposite decrease with the particles contents, the AC breakdown strength of micro-nanocomposite increase with the nano-ZnO contents, but the AC breakdown strength of nanocomposite increase and then decrease with the increment of nano-ZnO contents. The dielectric spectrum and corona corrosion test are carried out, the results show that the content of ZnO particles have influence on the relative permittivity of LDPE, and the dielectric loss factor of three composites are higher than that of LDPE. Nano-ZnO and micro-ZnO can improve the corona corrosion resistance of LDPE, and the corona breakdown resistance of micro-nanocomposite is the highest. After a period of the corona experiments, the results show that the corona corrosion of micro-nanocomposites and nanocomposites are not obvious. The dielectric properties of micronanocomposite are outstanding.