Effects of CNT size, network fraction, and interphase thickness on the tunneling distance between neighboring carbon nanotubes (CNTs) in nanocomposites

This article develops a simple equation for the tunneling distance between neighboring carbon nanotubes (CNTs) in polymer CNTs nanocomposites (PCNTs) as a function of CNT concentration, CNT dimensions, interphase thickness, the percentage of networked CNTs, and the wettability of the CNTs by polymer chains. The coupling of two developed models for the conductivity of PCNTs, assuming interphase and tunneling effects expresses in this equation. The suggested equation calculates the tunneling distance for some PCNT samples at different filler concentrations, and expresses the impacts of all the parameters on the tunneling distance. The appropriate predictions of the developed models for the conductivity of the samples and the acceptable levels of tunneling distance at various values of all parameters validate the suggested equation. The calculations indicate that the thinnest CNTs (radius of 5 nm) and the largest CNTs (length of 5 μm) produced the shortest tunneling distance of 2.5 nm, but the maximum tunneling distance of 6.5 nm was observed at the CNT radius of 20 nm and length of 20 μm. In addition, the low surface energy of the polymer matrix and the high CNT surface energy result in a short tunneling distance, but their roles in the tunneling distance are negligible.