Influence of carbon nanotube dimensions on the percolation characteristics of carbon nanotube/polymer composites

The effect of carbon nanotube aspect ratio (AR) on the percolation characteristics of their polymer composites was investigated by melt blending the multi-wall carbon nanotubes (MWCNTs) with different AR with a thermoplastic elastomer. Previously, most studies reported the effect of aspect ratio of MWCNTs only in the context of achieving the maximum electrical conductivity at lower percolation thresholds in the polymer composites. In this study, our results indicate that aspect ratio can also influence other percolation properties such as the pre-percolation conductivity, percolation conductivity and post-percolation conductivity, shape of the percolation curve, and the width of the insulator-conductor transition. We have established that AR can be used to tailor the percolation curves from sharp to quasi-linear ones, which can help us fabricate the percolative composites with stable electrical properties. Experimental results suggested that the mathematically calculated nominal AR of the MWCNTs was an unclear parameter to correlate with the percolation characteristics of the composites. Instead, an approach taking into consideration the nominal length (l) and the diameter (d) of the MWCNTs individually rather than as a combined AR (l/d) parameter gave a better explanation of the relation between MWCNT dimensions and percolation characteristics.