The effect of concentration and size of fine dispersed particles of graphite on ultimate tensile stress, elongation at break, melt flow rate, and wear resistance of composite materials based on propylene block-copolymer with ethylene was considered. The possibility of essential improvement of the properties of nanocomposites was shown by means of crosslinking reaction in the dynamic mode. Using the method of thermo-mechanical analysis, the transition regularities of nanocomposites from solid to viscous state were investigated. Also, optimal concentrations of the reacting components were established to achieve the highest physic-mechanical properties of nanocomposites.