Testing the influence of the temperature, RH and filler type and content on the universal power law for new reduced graphene oxide TPU composites

In this paper, 6 different reduced graphene oxide (rGO) were prepared by a modified Hummers' method and reduced by thermochemical methods. rGO materials were intentionally prepared to obtain different BET and thickness and oxygen content maintaining constant the lateral size to compare its performance on thermoplastic polyurethane (TPU) matrix. Microstructure and the effect of the incorporation of rGO on the hardness and electrical properties of TPU were investigated. The temperature and humidity dependence of the electrical conductivity have been studied and the sensitivity and the response time to humidity changes have been determined. Influence of the filler content, temperature and humidity on the Jonscher's universal power law (UPL) for ac conductivity versus frequency and its fitting parameters A and n were determined. An anomalous behaviour (according to UPL) has been observed and a linear correlation between log A and n independently of the filler content, humidity and temperature, however there is an influence of the rGO used for the preparation of the composite. To study the transport mechanisms the experimental results were adjusted to the equation σ   =   σ ₀exp[−( T _Mott/ T ) γ ] and the maximum adjustment for γ   =  1/4 like other carbon nanocomposites however there is not an unequivocal behaviour. (paper)