The effect of temperature on the electrical and thermal conductivity of graphene-based polymer composite films

In this work, we studied the effect of temperature on the electrical, thermal, and mechanical properties of graphene-based poly(vinylidene fluoride-co-hexafluoropropylene) composites. Graphene-based polymer composites (PC-Gn) with various graphene content were prepared using solution mixing and molding process. The physical, chemical, and mechanical properties of the PC-Gn composites were investigated using different characterization techniques including differential scanning calorimetry, scanning electron microscopy, potentiostatic electrochemical impedance spectroscopy, and dynamic mechanical analysis (DMA). DMA results showed that the strength of obtained PC-Gn composites increased with higher graphene wt%. The in-plane electrical and thermal conductivity values were measured over a temperature range from 25 to 125 degrees C using a four-point probe electrical conductivity system and optothermal Raman technique, respectively. Our results showed that temperature had a noticeable effect on the in-plane electrical and thermal conductivity values for PC-Gn where both values gradually decreased by the increment of temperature. We believe that by increasing temperature, the vibration of composite particles became more severe, which increased the system's anharmonicity and strongly reduced the lifetimes of electrons and phonons in the composite. Further analysis, including electrochemical analysis, was also done on all composite films showing that our process produced highly conductive films that potentially can be used in many electrochemical applications in the future.