This article describes the preparation, characterization, and properties of thermoplastic vulcanizate (TPV)/silica nanocomposites. The nanocomposites were prepared by the melt blending of TPV and maleic anhydride grafted polypropylene (mPP) into organically modified SiO2 (M-SiO2), treated with n-hexadecyl trimethylammonium bromide as a grafting agent for TPV during the melt mixing. The thermal stability and storage modulus of the 1 wt % m-SiO2 containing TPV/mPP/M-SiO2 nanocomposite were higher than those of pristine TPV. The most important observation was obtained from dynamic mechanical analysis, which revealed that the glass-transition temperature of the polypropylene phase of the nanocomposites increased (in comparison with that of virgin TPV), whereas the ethylene-propylene-diene monomer phase remained almost the same. The adhesion strength between the TPV/mPP/mSiO(2) nanocomposites and steel also increased with increasing M-SiO2 content. (c) 2005 Wiley Periodicals, Inc.