Preparation, microstructure and properties of polyethylene/alumina nanocomposites for HVDC insulation

In the recent decades, the phenomena of space charge accumulation in the high voltage direct current (HVDC) insulation have been attracted more attention. In this paper, low density polyethylene (LDPE) nanocomposites filled with alumina nanoparticles (nano-Al₂O₃) were prepared employing melting blend method. Morphologies of nanoparticles and LDPE/Al₂O₃ nanocomposites were performed by scanning electron microscopy (SEM). Electrical properties of the LDPE nanocomposites were also investigated. Results shown that the nano-Al₂O₃ particles modified with vinyl silane coupling can effectively enhance the breakdown strength of LDPE nanocomposites. With the nano-Al₂O₃ particles loading, the volume resistivity of the LDPE nanocomposites was increased, while dielectric permittivity of the nanocomposites was decreased. Space charge of the LDPE nanocomposites was measured by pulsed electro-acoustic (PEA) method. The charge profiles indicated that space charge suppression of the LDPE nanocomposites was better than that of pure LDPE. The excellent insulation properties of the LDPE nanocomposites were attributed to the better interfacial adhesion between the surface-treated nano-Al₂O₃ particles and the LDPE matrix.