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.

Chem. reduced graphite oxide with strongly improved shape anisotropy was prepd. by Staudenmaier oxidn. of high surface area graphite, followed by hydrazine monohydrate redn. Selection of the starting graphite was effected on the basis of the highest shape anisotropy of the crystallites. The overall oxidn.-​redn. procedure preserves the in-​plane order of graphite and dramatically increases the out-​of-​plane disorder, which becomes similar to that one of carbon black. In particular, the overall procedure led to aggregates of few piled structural layers (D⊥ ≈ 2 nm) with increased periodicity perpendicular to the layers (from 0.339 nm up to 0.362 nm) and with high shape (D‖/D⊥ ≈ 13) and strain (ε⊥/ε‖ ≈ 15) anisotropy

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.

Nanocomposites were prepared via melt blending, based on organically modified clays (OC), carbon nanotubes (CNT), and graphitic nanofillers made by a few layers of graphene (nanoG). In particular, nanocomposites based on a hybrid filler system, with a nanostructured filler such as carbon black (CB), are examined. It is shown that low crystalline order in the interlayer space of a layered nanofiller (such as OC and nanoG) leads to easier delamination. Nanofillers give rise to filler networking at low concentration, particularly in the presence of CB. Hybrid filler systems lead to nanocomposites' having initial moduli that are much higher than those calculated through the sum of the initial modulus of composites containing either only CB or only the nanofiller. Nanofillers enhance the matrix modulus by a multiplication factor that depends only on the nanofiller type and content, regardless of whether the matrix is a neat or a CB-filled polymer. Furthermore, the filler–polymer interfacial area is shown to be a parameter able to correlate the mechanical behavior of both nano-CNT and nanostructured (CB) fillers. By plotting values of the composite initial modulus versus the filler–polymer interfacial area, points due to CB, CNT, and the hybrid CB-CNT system lie on the same curve.

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