In this work, the role of graphene flake size on the properties of poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) composites was studied. Graphene flakes were added to PVDF-HFP using a solution mixing and molding process. By increasing graphene particle size and its concentration in the composites, higher electrical conductivity, in-plane thermal conductivity, and elastic modulus were achieved. Maximum tensile strength was obtained for the composites with average graphene flake size of 2, 5, and 7 μm at graphene concentrations of 10 wt%, 5 wt%, and 20 wt%, respectively. Thick flexible composite films (0.2-0.4 mm) with ultra-high in-plane electrical conductivity (~4500 S/m), in-plane thermal conductivity (~26 W/m/K), and tensile strength (~50 MPa) were obtained for the samples containing the graphene flakes with a larger average particle size of 7 μm. To our knowledge, the first two values are larger than any other values reported in the literature for PVDF-based composites.
In this work, we studied the effect of temperature on the electrical, thermal, and mechanical properties of graphene-based poly(vinylidene fluoride-cohexafluoropropylene) 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 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.applications, conducting polymers, thermal properties
| INTRODUCTIONGraphene, a one-atom-thick two-dimensional honeycomb network of carbon atoms, has a very large specific surface area of 2600 m 2 /g and very high mechanical, thermal, and electrical properties. 1 The in-plane thermal conductivity of a single layer of graphene is very high and is around 3080-5150 W/mK at room temperature. 2
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