Influence of interface structure on dielectric properties of epoxy/alumina nanocomposites

Alumina (Al2O3) nanoparticles with three different interface structures have been selected as reinforcement fillers for epoxy nanocomposite, that is surface untreated Al2O3 nanoparticles, γ-aminopropyl-triethoxysilane modified Al2O3 nanoparticles (Al2O3-APS), and hyperbranched aromatic polyamide grafted Al2O3 nanoparticles (Al2O3-HBP). The interface structures of the Al2O3 nanoparticles were characterized by X-ray diffraction and atomic force micrographs. Our studies reported the influence of the interface structure of Al2O3 nanoparticles on the morphology and dielectric properties of epoxy nanocomposites. It was found that the incorporation of the Al2O3-APS and Al2O3-HBP nanoparticles not only improved the dispersion of the nanoparticles in the epoxy matrix, but also enhanced the glass transition temperatures (Tgs) and largely influenced the dielectric properties of the epoxy nanocomposites as compared with the nanocomposites filled with the surface untreated Al2O3 nanoparticles. The improvement of Tgs, volume resistivity, dielectric strength, and the reduction of dielectric loss could be attributed to the good dispersion and special interface structure of the Al2O3 nanoparticles in the epoxy matrix. [graphic not available: see fulltext]