A methodology for reinforcement of liquid ethylene propylene dicyclopentadiene copolymer (liquid-EPDM) based elastomer with multiwalled carbon nanotubes (MWCNTs) was proposed. Acid-treated MWCNTs were first reacted with poly(acryloyl chloride) (PACI) leading to a grafted encapsulation, which were subsequently reacted with hydroxy ethyl acrylate (HEA) to generate vinyl groups. Thus obtained vinyl groups functionalized MWCNTs (vinyl-MWCNTs) were characterized using Fourier transform infrared spectroscopy, transmission electron microscopy, and thermogravimetric analysis. The vinyl-MWCNTs were blended with liquid-EPDM and subjected to co-curing; an intercrosslinked structure was obtained via the free radical polymerization among the vinyl groups on vinyl-MWCNTs and the double bonds on liquid-EPDM. As a result, the vinyl-MWCNTs and the cured EPDM matrix were covalently linked. The chemical interfacial interaction between vinyl-MWCNTs and the cured matrix were observed by scanning electron microscope, which provided obvious reinforcement of elastomer. POLYM. ENG. SCI., 50:1408-1413, 2010. (C) 2010 Society of Plastics Engineers