Thermal and electrical characterization of poly(vinyl)alcohol)/poly (vinylidene fluoride) blends reinforced with nano-graphene platelets

Nano-graphene/polymer composites can function as pressure induced electro-switches, at concentrations around their conductivity percolation threshold. Close to the critical point, the pressure dependence of the electron tunneling through the polymer barrier separating nano-graphene?s results from the competition among shortening of the tunneling length and the increase of the polymer?s polarizability. Such switching behavior was recently observed in polyvinyl alcohol (PVA) loaded with nano-graphene platelets (NGPs). In this work, PVA is blended with ?-poly(vinylidene fluoride) (PVdF) and NGPs. Coaxial mechanical stress and electric field render the nano-composite piezoelectric. We investigate the influence of heterogeneity, thermal properties, phase transitions and kinetic processes occurring in the polymer matrix on the macroscopic electrical conductivity and interfacial polarization in casted specimens. Furthermore, the effect of electro-activity of PVdF grains on the electric and thermal properties are comparatively studied. Broadband Dielectric spectroscopy is employed to resolve and inspect electron transport and trapping with respect to thermal transitions and kinetic processes traced via Differential Scanning Calorimetry. The harmonic electric field applied during a BDS sweep induces volume modifications of the electro-active PVdF grains, while, electro-activity of PVdF grains can disturb the internal electric field that free (or bound) electric. The dc conductivity and dielectric relaxation was found to exhibit weak dependencies.

Automated summary

The study focuses on the piezoelectric properties of nano-graphene/polymer composites and the influence of heterogeneity, thermal properties, phase transitions, and kinetic processes in the polymer matrix on macroscopic electrical conductivity and interfacial polarization. Broadband Dielectric spectroscopy is used to analyze electron transport and trapping, with effects of the harmonic electric field on the volume modifications of electro-active PVdF grains observed. Additionally, the electro-activity of PVdF grains is found to have weak dependencies on dc conductivity and dielectric relaxation.