Single-walled carbon nanotube filled thermoplastic polyurethane nanocomposites: Influence of ionic liquid on dielectric properties

Abstract

Electrically conductive nanocomposites based on thermoplastic polyurethane (TPU) and single walled carbon nanotube (SWCNT) have been successfully prepared by solution casting technique. Prior to mixing, SWCNT is first dispersed in DMF and ionic liquid 1-Allyl-3-methyl imidazolium chloride (AMIC). The SWCNT phase is uniformly dispersed in the ionic liquid (IL) containing systems as observed in HRTEM and FESEM photomicrographs. The dielectric properties like dielectric permittivity (ε'), AC conductivity (σac), real and imaginary parts of impedance (Z' and Z'') of TPU/SWCNT nanocomposites have been analysed in the frequency range of 1–106 Hz. A comparison study of the dielectric properties of the systems with and without IL are thoroughly investigated. Increasing trend of ε' with increasing the SWCNT loading is mostly due to the increase in polarizable dipoles and adequate interfacial polarization of the charge carriers in the field direction. Frequent hopping and tunnelling mechanism with increasing the SWCNT loading is mainly responsible for the hike in σac. The increase in close proximity between the conductive channels with increase in conductive SWCNT loading and incorporation of IL reflects from the decrease in Zʹ and Z ʹʹ of the systems. The semi-circular nature of the Nyquist plot informs about the dielectric and capacitive characteristics of the developed nanocomposites and the decrease in area under the Nyquist plot significantly explains about the decrease in bulk resistivity.