Effects of SiO2 particles on surface charge of epoxy nanocomposites

Epoxy used as insulating material in electronic and electrical devices plays an important role in system reliability. Addition of nanoparticles into epoxy can improve the insulating properties compared with undoped material. However, due to the change of the material structure, trap characteristics and charge behaviors are altered as a consequence. This possibly leads to a great risk of electric field distortion and discharge that degrades the insulation. From the viewpoint of safety, it is necessary to investigate the charge behavior on epoxy nanocomposites. This paper presents study aimed at clarifying the effect of nano-filler content on surface charge accumulation and decay behaviors of epoxy nanocomposites with SiO₂ particles. Samples were prepared by dispersing nano-scale SiO₂ into epoxy by mixing with shear force. Corona charging tests were performed at room temperature with a relative humidity of ~ 40%. The charge distribution was measured by means of an electrostatic voltmeter. Obtained results show the dependence of the accumulated charge as well as the charge decay rate upon the concentration of SiO₂, varying as a function of the charge polarity, charging time and charging voltage. It is suggested that the charge dynamics is dependent upon the characteristics of localized surface states that are altered by the nanoparticles.