Roles of filler dimensions, interphase thickness, waviness, network fraction, and tunneling distance in tunneling conductivity of polymer CNT nanocomposites

We present a simple model to express the tunneling conductivity of polymer CNT nanocomposites as a function of the filler dimensions, filler conductivity, interphase thickness, waviness, fraction of networked CNTs, and tunneling distance. This model expresses the percolation threshold and the fraction of networked CNTs in terms of filler dimensions, waviness, and interphase thickness. The model was tested using experimental results from the literature. The predictions show good agreement with the experimental results in all samples, demonstrating the model's robustness for estimating tunneling conductivity. Moreover, the tunneling distance decreases as the filler concentration increases in all samples. The model parameters have a reasonable effect on the tunneling conductivity. The waviness and tunneling distance inversely affect the tunneling conductivity. Further, the waviness weakens the effective length of the nanotubes, and large tunneling distances cannot effectively transfer electrons between two adjacent nanotubes. The interphase thickness directly controls the tunneling conductivity, because a thick interphase reduces the percolation threshold. Poor percolation also creates large and dense conductive networks in nanocomposites, which is desirable for conductivity. (C) 2017 Published by Elsevier B.V.