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Abstract
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In the present study, two types of carbon-based fillers, i.e., multi-walled carbon nanotubes (MWCNTs) and carbon fibers (CFs), were incorporated into thermoplastic polyurethane (TPU) through melt mixing to prepare mono-filler and bi-filler composites. It was evaluated how much the properties of bi-filler composites were different from those of their mono-filler counterparts. ATR-FTIR and time sweep rheological measurements were employed to study the microphase separation of TPU. The quantitative results of ATR-FTIR corroborated that bi-filler composites possessed higher microphase separation compared to their mono-filler counterparts. The kinetics of networks formed by microphase separation was accelerated for the composite samples compared to the 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 the 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' and G", and vice versa. Shearing at an intermediate rate of 20 s-1 prompted the electrical conductivity of both mono-filler and bi-filler composites and coherently decreased the electrical percolation threshold.
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