Filler concentration effect on breakdown strength and trap level of epoxy resin–Al2O3 nanocomposites

In this work, epoxy resin samples incorporated with nano-Al 2 O 3 of various concentrations 0, 1, 3 and 5 wt% were prepared. Surface treatment of nano-Al 2 O 3 was performed by the saline coupling agent of γ-aminopropyltriethoxysilane (KH550) to restrict the aggregation. The thermal gravimetric analysis (TGA) of the epoxy resin/Al 2 O 3 nanocomposites was observed at different filler concentrations. TGA analysis indicated that incorporation of nano-Al 2 O 3 increases the decomposition temperature as compared to pure epoxy resin. Moreover, 3 wt% filler concentration showed increased decomposition temperature because nanoparticles form close connections between molecules due to which thermal stability improved at higher temperatures. Atomic force microscopy was employed for the surface morphology of epoxy resin/Al 2 O 3 nanocomposites which has indicated that surface roughness of epoxy resin/Al 2 O 3 nanocomposites increased slightly with the filler concentration. The distribution of trap energy and trap density obtained by isothermal surface potential decay measurements revealed that 1 wt% filler concentration results in decrease in surface potential decay rate. In addition, significant increase in deep trap energy level and trap density was obvious at 1 wt% filler concentration. AC and DC breakdown strength of the samples was measured to evaluate the effect of filler concentrations on the electrical characteristics of epoxy resin. The results showed that breakdown strength of the epoxy resin/Al 2 O 3 nanocomposites increases with the nano-Al 2 O 3 concentration. Moreover, increase in trap energy results in an increase in the breakdown strength of the nanoparticles.