this work, the dielectric spectroscopy and dynamic mechanical thermal spectroscopy of neat epoxy and epoxy nanocomposites modified by boehmite, gamma-alumina and alpha-alumina nanoparticles, respectively, were investigated. The dielectric behavior of epoxy resin was significantly affected by the incorporation of alpha-alumina nanofiller. The values of real and imaginary part of relative permittivity of epoxy/alpha-alumina nanocomposite were even lower than these of neat epoxy. On the contrary, these values of boehmite and gamma-alumina nanocomposites were higher than these of neat epoxy. The glass transition temperature (T-g) determined by dynamic mechanical thermal analysis (DMA) was obviously decreased when boehmite nanofiller was added into the epoxy nanocomposite. The value of T-g was slightly decreased by gamma-alumina and apparently increased by alpha-alumina nanofiller. These changes of performance may be attributed to that the existence of alpha-alumina nanoparticles restricted the mobility of polymer molecular chains. (C) 2016 Society of Plastics Engineers