A nanoGraphite (nanoG) having a high surface area and a high shape anisotropy, defined as the ratio between the crystallite dimensions in a direction orthogonal and parallel to structural layers, was used to prepare nanocomposites based on poly(1,4-cis-isoprene) (IR), in the neat polymer matrix and in the presence of carbon black (CB). Tensile and dynamic-mechanical measurements showed that nanoG forms a filler network at a relatively low concentration in neat IR and a hybrid filler network at a lower nanoG concentration in the presence of CB. A synergistic effect between the two carbon allotropes was found: composites containing both fillers present initial modulus values much higher than those calculated through the simple addition of the initial moduli of the composites containing only CB or nanoG.

Abstract. Interactive effects of carbon allotropes on the mechanical reinforcement of polymer nanocomposites were investigated. Carbon nanotubes (CNT) and nano-graphite with high shape anisotropy (nanoG) were melt blended with poly(1,4-cis-isoprene), as the only fillers or in combination with carbon black (CB), measuring the shear modulus at low strain amplitudes for peroxide crosslinked composites. The nanofiller was found to increase the low amplitude storage modulus of the matrix, with or without CB, by a factor depending on nanofiller type and content. This factor, fingerprint of the nanofiller, was higher for CNT than for nanoG. The filler-polymer interfacial area was able to correlate modulus data of composites with CNT, CB and with the hybrid filler system, leading to the construction of a common master curve.

The filler networking process promoted by multiwalled CNTs is studied in neat and CB-filled poly(1,4-cis-isoprene) matrices. TEM analysis, tensile, dynamic-mechanical, and electrical measurements reveal that the CNTs form a filler network at low concentration in neat PI and a continuous hybrid filler network at a lower CNT concentration in the presence of CB, with a remarkable increase of the nonlinear dynamicmechanical behavior of the nanocomposites at low deformation. A synergistic effect between CB and CNTs is demonstrated. The addition of CNTs to the CB-filled PI matrix leads to initial modulus values much larger than those calculated by simple addition of the two initial moduli of the composites containing only CB and only CNTs, respectively

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