In this study, nanocomposites of thermoplastic polyurethane and multiwalled carbon nanotubes (MWCNTs) with varying nanofiller content (ranging from 0 wt% to 1 wt%) were prepared via the melt compounding method. Moreover, the influence of shear field and thermal processing on electrical conductivity has been evaluated. The evaluation of the phase separation degree revealed that with the increase in the nanofiller content from 0% to 0.4%, the phase separation degree increased by 25%. However, a further increase in the nanoparticle content slightly decreased the phase separation degree. Moreover, by increasing the nanofiller content up to 0.4%, the melting temperature and the melting enthalpy of the soft phase as well as the melting temperature of the hard phase increased. With the increase in the nanofiller content to 0.4%, a 3D network of MWCNTs was developed, corroborating the formation of an electrically conductive nanocomposite. The conductivity increased 3750-fold in the quenched and 5000-fold in the annealed samples with the increase in the nanofiller content from 0.2% to 1%. In general, the annealed nanocomposites featured lower conductivity than the quenched ones. The effect of the shear on conductivity was nanofiller content-dependent. Exposure to shear below and above the percolation threshold decreased and increased the electrical conductivity, respectively.

Two types of carbon-based fillers, i.e. multi-walled carbon nanotubes and carbon fibers, were incorporated into thermoplastic polyurethane (TPU) through melt mixing to prepare mono-filler and bi-filler composites. It was evaluated as to how much the properties of bi-filler composites were different from those of their mono-filler counterparts. Attenuated total reflectance Fourier transform infrared (ATR-FTIR) and time sweep rheological measurements were employed to study the microphase separation of TPU. The quantitative results of ATR-FTIR corroborated that the bi-filler composites possessed greater microphase separation compared to their mono-filler counterparts. The kinetics of networks formed by microphase separation was accelerated for the composite samples compared to neat TPU. The fillers acting as platforms provided a suitable surface for the hard segments to form microphase-separated domain networks. Conductivity measurement proved that the electrical conductivity values of the bi-filler composites were higher than those of the mono-filler counterparts and the simultaneous presence of fillers decreased the electrical percolation threshold. Moreover, the effect of shear deformation applied during the processing on the rheological and electrical properties of the mono-filler and bi-filler composites was evaluated. It was found that shearing at low rates increased the cross-time of G 0 and G 00 , and vice versa. Shearing at an intermediate rate of 20 s −1 promoted the electrical conductivity of both mono-filler and bi-filler composites and coherently decreased the electrical percolation threshold.

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