Elastomer composites based on improved fumed silica and carbon black. Advantages of mixed reinforcing systems

The combination of reinforcing fillers is one of the most promising tendencies in elastomer reinforcement, where a synergic effect between them is desired. Up to now, the use of mixed fillers has been focused on the preparation of dual fillers based on a complex synthesis process where silica particles are in situ generated in a carbon black matrix. In this paper, mixed filler systems are prepared following a straightforward methodology, where carbon black is gradually and partially substituted by modified fumed silica. The presence of reinforcing fillers with different surface energies significantly decreases filler networking, reducing the non-linear viscoelastic response of the composites. The hybrid reinforcing systems prepared were easily incorporated into the elastomer matrix by conventional methods in rubber technology. Physical and dynamic responses of the elastomeric composites were characterized in order to find the optimum mixed system combination. Filler–rubber interface was characterized combining 1H low field DQ (Double Quantum) NMR spectroscopy and equilibrium swelling experiments.