Nano and nanostructured fillers and their synergistic behavior in rubber composites such as tyres

In this work, it was investigated the filler networking phenomenon promoted by nanofillers in IR matrix. IR based composites were prepared containing the following nanofillers: organically modified layered silicates (OC), carbon nanotubes (CNT), graphite with a high surface area (G) or chemically reduced graphite oxide (CRGO). These nanofillers were used as the only filler or in combination with 60 phr of carbon black (CB). The composite structure was investigated through transmission electron microscopy and X-ray diffraction analysis. Composites were characterized with tensile and dynamic-mechanical measurements, determining the initial modulus E from nominal stress-nominal strain curves and the dependence of shear storage G’ and loss modulus G’’ on the strain amplitude. All of the mentioned fillers were able to give rise, in the composite material, to particles with at least one dimension of one or few nanometers. They can be thus considered as nanofillers and the composites based on them can be considered as nanocomposites. OC, CNT and G were found to establish a network in the rubber matrix at a relatively low concentration, with a percolation threshold in a range from about 5 to about 8 phr, when they were used as the only filler. A hybrid filler network was formed in the presence of carbon black, with evidence of different regimes for the dependence of the excess of modulus (either E or G’ at minimum deformation) on the nanofiller content. The comparison between G and CRGO allowed to investigate the effect of a different degree of order, in layered materials, in the direction orthogonal to the structural layers, obtaining a preliminary indication that a higher number of ordered pillared layers brings to higher dynamic shear moduli.