Effect of temperature on the electrical and electromechanical properties of carbon nanotube/polypropylene composites

The effect of temperature on the electrical and electromechanical (piezoresistive) properties of composite films made of multiwall carbon nanotubes (MWCNTs) and polypropylene is investigated. The electrical response to temperature in alternating current (AC, i.e. thermoimpedance) showed higher sensitivity than in direct current (DC, thermoresistivity) and is influenced by frequency (f). The sensitivity factor in DC reached 1.07 %& DEG;C-1, while in AC at 100 Hz was 2.7 % C-1 for the impedance modulus for 4 wt.% MWCNT nanocomposites . The electrical properties of the nanocomposites in AC investigated through broadband dielectric spectroscopy exhibited a resistive-capacitive behavior with a transition at f & SIM;10(4) Hz. Temperature also showed a strong influence on the piezoresistive response of the nanocomposites, showing a 10% increase in the piezoresistive sensitivity at 50 & DEG;C with respect to the response at 25 & DEG;C, and an important decrease in sensitivity at 100 & DEG;C for small (<3%) strains. The influence of temperature on the electrical and electromechanical responses investigated herein may assist in further developments of smart temperature-sensing materials, and in developing thermal compensation factors to properly calibrate piezoresistive/piezoimpedance responses for strain measurements.

Automated summary

The effect of temperature on the electrical and electromechanical properties of carbon nanotube-polypropylene composite films is investigated. The electrical response to temperature is influenced by frequency and the sensitivity is higher in alternating current than in direct current. The piezoresistive response of the nanocomposites is also affected by temperature, with an increase in sensitivity at 50°C and a decrease at 100°C for small strains. This research has implications for the development of smart temperature-sensing materials and the calibration of piezoresistive/piezoimpedance responses for strain measurements.