Experimental investigation of the thermoresistive response of multiwall carbon nanotube/polysulfone composites under heating-cooling cycles

The thermoresistive behavior of multiwall carbon nanotube (MWCNT)/polysulfone composites is experimentally investigated under heating-cooling cycles. Composites with MWCNT weight concentrations between 0.5 and 50 wt.% were fabricated and their morphology and porosity were examined. Changes in their electrical resistance upon changes in temperature were simultaneously measured under heating-cooling cycles above and below room temperature (25 °C), and under incremental steps of constant temperature. The thermoresistive sensitivity (temperature coefficient of resistance, TCR) and the hysteresis of each heating-cooling cycle were also investigated. Composites with MWCNT concentrations of 25 wt.% and below showed a positive TCR, while negative ones were measured for composites with 40 wt.% and 50 wt.%. The thermoresistive hysteresis was higher for composites with high MWCNT content (40 wt.% and 50 wt.%). Higher TCRs were found for temperatures above room temperature than below, and dominance of the MWCNT inherent thermoresistivity was observed for composites with very high MWCNT content (≥40 wt.%). Finally, the potential of this material to perform as a thermistor was assessed by comparing its readings to those of a commercial (solid state) sensor, showing very high sensitivity, good reproducibility and fair agreement with the commercial sensor.