Recently, the production of polymers loaded with inorganic nanomaterials has been one of the most economical techniques playing a special role in improving the physical and mechanical properties of nanocomposites. Rubbers loaded with different concentrations of carbon nanoparticles (CNPs) were synthesized. The mechanical properties were tested according to standard methods. It was found that the properties of the investigated nanocomposites were improved, depending on the concentration of CNPs in the investigated composite. The optimum concentration was found to be 1.3 vol %. Affine deformation based on the Mooney-Rivilin model was used to visualize the effect of CNPs on the rubber. When polyethylene (PE) was added to rubber/CNPs at the optimum concentration (12.4 vol %), the modulus, tear resistance, and fatigue life were increased, whereas the tensile strength decreased, and the strain at rupture remained almost same. A crosslink model was used to explain the influence of PE on the rubber/CNP nanocomposites. (C) 2011 Wiley Periodicals, Inc. J Appl Polym Sci 122:3023-3029, 2011