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Effects of aspect ratio of multi-wall carbon nanotubes (MWCNTs) on the dispersion of MWCNTs in ethylene-α-octene block copolymer (OBC) and the properties of OBC/MWCNTs nanocomposites were studied, and two series of MWCNTs with different aspect ratios based on the same length and the same diameter were considered. Scanning electron microscope (SEM) and transmission electron microscope (TEM) results show that small and large agglomerates induced by intra- and inter-entanglement of MWCNTs are present for MWCNTs with high aspect ratio having smaller diameter and larger length, respectively. Rheological, electrical and tensile properties of OBC/MWCNTs nanocomposites are related to the aspect ratio and dispersion of MWCNTs. The formation of agglomerates, especially large agglomerates, influence the network perfection, weakening the contribution of MWCNTs to the rheology and electrical properties. The inter-entanglement shows less negative effect on the enhancement for the modulus and strength of OBC nanocomposites, and intra-entanglement of MWCNTs shows discounted enhancing properties. The aspect ratios of MWCNTs related to not only the length but also the diameter play the dominant role on the dispersion in polymers and the properties of polymer nanocomposites. [ABSTRACT FROM AUTHOR]

An isotactic polypropylene (iPP) nanocomposite with low percolation threshold, ultrahigh dielectric permittivity and toughness by controlling the dispersion of multi-walled carbon nanotubes (MWCNTs) through ethylene-α-octene block copolymer (OBC), is reported. A special ‘sosatie’ structure, i.e. finely dispersed long MWCNTs inserted in OBC phase uniformly distributed in the continuous iPP matrix, was constructed through simple melt compounding process. The percolation threshold of the prepared iPP/OBC/MWCNT nanocomposites was ca. 0.5 vol%, lower than that of iPP/MWCNT nanocomposites. The iPP/OBC/MWCNT nanocomposites exhibited an ultrahigh dielectric permittivity (ca. 9000) at 100 Hz and a very low dielectric loss (ca. 1.5). MWCNTs also improved the compatibility between iPP and OBC components, leading to a high impact strength of iPP/OBC/MWCNT nanocomposites (about 13 times higher than pure iPP when the content of MWCNT was 1.49 vol%). Thus, the approach reported in this work can provide a new and convenient route to prepare high-performance polymer nanocomposite dielectric materials with low percolation thresholds and balanced mechanical properties. [ABSTRACT FROM AUTHOR]

1 vol% multiwalled carbon nanotubes (MWCNTs) is finely dispersed in poly(propylene) (PP)/boron nitride (BN) composites with the assistance of commercial ethylene‐α‐octene block copolymer (OBC) through a conventional melt‐compounding method, whereas serious agglomeration of MWCNTs occurs in the melt compounded PP/MWCNTs/BN composites. The good dispersion of MWCNTs facilitates the formation of a better conductive network to synergistically improve the thermal conductivity of PP/OBC/MWCNT/BN composites, up to 1.71 W m−1 K−1 at a BN content of 20 vol%. Meanwhile, the elastomeric OBC component leads to markedly enhanced impact toughness (>8.0 kJ m−2) and elongation at break (>23%) of the composites. This work sheds light on the fabrication of thermally conductive polymer composites with balanced mechanical performance through a conventional processing technique. [ABSTRACT FROM AUTHOR]