In the present study, different quantities of multiwalled carbon nanotubes and an immiscible blend of polyamides, 50 vol%/50 vol%. Polyamide 12/polyamide 6 (PA12/PA6), are melt blending by extrusion to obtain conducting polymer composites. The rheological and electrical properties of nanocomposites are evaluated as function of nanofiller content. Both rheological and electrical percolation thresholds are calculated by graphical methods and fitting the experimental data to the well‐known power‐law expression. The low percolation thresholds are probably due to the high aspect ratio of the nanotubes, kept after the composite processing and to the preferential localization of carbon nanotubes (CNTs) in the polyamides interface. This latter is predicted by the wetting parameter and finally confirmed by TEM micrographs. The mixing strategy followed, by using a PA12 masterbatch and an immiscible blend of polyamides, seems suitable to form a segregated conductive network in the matrix with low CNT quantities. POLYM. COMPOS., 38:2679–2686, 2017. © 2015 Society of Plastics Engineers

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The effect of different toughening strategies on the mechanical properties of multiwalled carbon nanotube/polycarbonate composite (PC/MWNT) for electromagnetic interference shielding was analyzed from the mechanical and fracture tests using linear elastic fracture mechanics. The effect of processing (injection and compression molding) and manufacturing (annealing) conditions in the mechanical properties and electrical conductivity has been studied. The classic electromagnetic theory predicts a shielding effectiveness around 40 dB for nanocomposites with 5 wt% of MWNT in the frequency range studied. These values make these compounds to be very interesting materials for potential applications as electronic housings. Therefore, a combination of cyclic form of polybutylene terephthalate addition and annealing strategies let to optimize flexural parameters and improve the flexural modulus of PC composites. The rheology results showed that the dynamic moduli and the viscosity grew with increasing MWNT content. A significant change in frequency dependence of the moduli was observed, with respect to pure PC, which indicates a transition from a liquid‐like to a solid‐like behavior. Finally, the morphological study proves that the composites display different toughening mechanisms as function of carbon nanotube quantity. This fact could explain the different fracture behaviors of materials. In summary, it has been proved that it is possible to obtain PC/MWNT nanocomposites with relatively high conductivity, minimizing the loss of mechanical properties, using processing techniques easily scalable at industrial level. POLYM. COMPOS., 34:1938–1949, 2013. © 2013 Society of Plastics Engineers

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Three different types of carbon nanofibers (CNF) were incorporated in the same polypropylene (PP) matrix by twin-screw extrusion. The rheological and thermal properties were investigated. The rheological characterization of CNFs/PP composites as function of their volume fraction shows different microstructures: percolated and non-percolated behaviors of their CNF's networks. In this work, the laser flash technique is employed in the experimental determination of the thermal diffusivity and conductivity of composites at room temperature. The ultimate aim is to correlate microstructure described by rheological analysis with final thermal properties. The results show that thermal diffusivity and conductivity are clearly higher for rheologically percolated composites suggesting that above certain critical content of nanofibers thermal transport is mainly controlled by percolated structures caused by interconnected CNFs' networks. Finally, thermal conductivity results are described by means of percolation theory from which an intrinsic thermal conductivity for the CNFs' network of approximately 6.5 W/ m K, i.e. close to three times lower than some values reported in literature for SWCNTs' networks, was calculated.