Despite of the variety of existing techniques, there is still a continuous demand in the development of more efficient recycling technologies, for economic and environmental reasons. A new approach for recycling EPDM rubber waste has been recently introduced utilizing a solvent free activation process by addition of liquid polymers (LP). The present study investigates the influence of the content and varying types of activated rubber waste particles (RWP-LP) in new composites. By varying the proportion of RWP-LP in the range from 25 up to 75 v/v % information about optimized compositions of new compounds were obtained. It was found that the ratio and type of RWP-LP induce significant differences in terms of cure characteristics, mechanical properties, crosslink density and morphology. Promising results with high potential application for the production of seal and sealing systems on the industrial scale were obtained by using up to 50 v/v % of RWP-LP with low ethylene amount. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 42097.