The preparation, characterization, and properties of the new thermoplastic vulcanizate (TPV)/organoclay nanocomposites are reported in this article. The nanocomposites were prepared by the melt intercalation method. The organoclay was first treated with glycidyl methacrylate, which acts as a swelling agent for organoclays, as well as a grafting agent for TPV (in the presence of dicumyl peroxide) during the melt mixing. The nanocomposite was intercalated, as evidenced by X-ray diffraction. The tensile modulus of the 5% TPV/organoclay nanocomposite was higher than that of the 20% tale-filled microcomposite. The storage modulus of the nanocomposite was higher than that of the pristine TPV. The most important observation is obtained from dynamic mechanical analysis, which reveals that the glass-transition temperature of the polypropylene phase of the nanocomposite increases (as compared to virgin TPV), whereas the ethylene-propylene-diene monomer phase remains almost the same. (C) 2004 Wiley Periodicals, Inc.