Overcoming the disadvantages of fumed silica as filler in elastomer composites

Elastomeric composites have been prepared using pre-treated fumed silica as a reinforcing system. The processing disadvantages of fumed silica were overcome by a novel one-pot modification method based on silanization treatment of silica particles after an ultra-high energy sonication process that breaks down the micro-aggregates/agglomerates of pristine silica into nanoparticles. Grafted organosilane molecules on the nanoparticle surfaces avoid the natural tendency for silica particles to re-agglomerate obtaining a stable dispersion of organo nanosilica particles that are compatible with the rubber matrix. The modified nanosilica can be easily incorporated into the elastomer matrix by conventional methods employed in rubber technology, contrary to pristine fumed silica which shows significant compounding disadvantages leading to high viscosity compounds. The improved dispersion and enhanced interface significantly enhance the final properties of the composites. Finally, the filler–rubber interface was characterized combining 1H low field Double Quantum (DQ) NMR spectroscopy and equilibrium swelling experiments. This novel experimental methodology demonstrates the existence of improved interactions in the interface between silica particles and rubber macromolecules.