Electrical and Dielectric Properties of Exfoliated Thermally Reduced Graphene Based Polyurethane Nanocomposites

Abstract

Thermally reduced graphene nanosheets (TRG) were prepared by using thermal exfoliation followed by annealing and then were served as fillers to well disperse in thermoplastic polyurethane (TPU) in a concentration range of 0.5-5.5 vol.%. The electrical conductivity, dielectric and mechanical properties of as-prepared TPU/TRG nanocomposite thin films were examined. The DC electrical conductivity was improved up to 3 x 1x10(-2) S m(-1) for the 5.5 vol.% TPU/TRG nanocomposite in comparison to 2 x 81x10(-11) S m(-1) for neat TPU matrix. Addition of TRG nanosheets enhanced the Young's modulus but reduced the strain-at-break and tensile strength of the nanocomposite films. The dielectric behavior including dielectric constant (epsilon) and tangent loss varied with the TRG loading in the nanocomposites. Results showed the increase in dielectric constant from 1 to 550 as well as the increase in tangent loss from 0.03 to 350 upon increasing concentration of TRG in the frequency range of 20-106 Hz. The high dielectric constant values in the low frequency region is mainly attributed to the Maxwell-Wagner polarization effect, while high values of tangent loss is contributed from the current leakage through the electrically conducting network of TRG sheets formed within the TPU matrix at high filler loadings.