This article reports on a novel route to develop ethylene-propylene-diene rubber (EPDM)/montmorillonite nanocomposites Modification of the MMT was carried out with maleic anhydride (MA), which acts as the intercalation agent for MMT and the vulcanizing agent for EPDM matrix, as well as the compatibilizer for the EPDM and MMT phases. The effect of MA-modified MMT in nanocomposites was investigated by focusing on three major aspects: structural analysis, thermal properties, and material properties. The d-spacings of both the MA modified MMT and exfoliated nanocomposites were investigated by X-ray diffraction (XRD), and the morphology of these nanocomposites was examined by transmission electron microscopy (TEM) and scanning electron microscopy (SEM). Dynamic mechanical analysis confirms the constraint effect of exfoliated MMT layers on EPDM chains, which benefited the increased storage modulus, increased glass transition temperature. Thermogravimetric analysis indicates that there is some enhancement in degradation behavior between the nanocomposites and EPDM matrix. The nanocomposites exhibit great improvement in tensile strength and modulus, as well as elongation-at-break. The effects of MA addition on the formation of nano-metric reinforcement and on the mechanical properties of nanocomposites are discussed. (c) 2005 Wiley Periodicals, Inc.