In situ thermoresistive characterization of multifunctional composites of carbon nanotubes

The thermoresistive behavior of nanocomposites with electrically conductive networks of carbon nanotubes (CNTs) in a vinyl ester polymer matrix were characterized using an in situ electrical resistance measurement during thermomechanical analysis. A series of specimens above the electrical percolation threshold ranging from 0.10 to 1.00 wt% CNT were studied. The results show the thermoresistive behavior is strongly dependent on the CNT concentration, thermal expansion and polymer segmental motion. At higher concentrations of carbon nanotubes the temperature coefficient of resistance (TCR) varied with temperature and could either be positive or negative while specimens with low CNT concentrations near the percolation threshold showed a near-zero but negative TCR. Since the nanocomposite bulk resistivity of the specimens is dominated by the tunneling resistance at CNT/CNT junctions the nanotubes effectively act as a network of sensors that can detect thermal transitions and other thermochemical changes in situ.