Effect of the carbon nanotube size dispersity on the electrical properties and pressure sensing of the polymer composites

Two different-diameter carbon nanotubes (CNTs), i.e., CNT-1 (diameter = 10–30 nm, length = 5–15 μm) and CNT-2 (diameter = 20–40 nm, length = 5–15 μm), were mixed in various relative concentrations to obtain series of hybrids with wider diameter disparity, which were subsequently melt blended with a polypropylene-based thermoplastic elastomer to fabricate their respective polymer composites. By changing the relative concentrations of CNTs in a polydisperse mixture, we were able to tune the percolation characteristics and the pressure–resistance sensitivity of the polymer composites. Percolation threshold, percolation window, and the minimum achievable resistivity value of the composites were found to be the function of relative concentration of CNTs in the polydisperse system. An important finding of this study is that percolation characteristics of composites with polydisperse system of CNTs prepared by mixing of two different CNTs with different relative concentrations can be explained by model of hybrid fillers. These findings may open a new pathway to design the conductive polymer composites with controlled electrical and sensing properties for various applications.