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

Abstract

Abstract 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 %°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 ∼104 Hz. Temperature also showed a strong influence on the piezoresistive response of the nanocomposites, showing a 10% increase in the piezoresistive sensitivity at 50 °C with respect to the response at 25 °C, and an important decrease in sensitivity at 100 °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.