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

TL;DR

This study investigates the thermal and electrical properties of PVA/PVdF blends reinforced with nano-graphene platelets, focusing on their potential as pressure-induced electro-switches and the effects of heterogeneity and phase transitions.

Contribution

It provides a comprehensive analysis of how nano-graphene and PVdF influence the electrical and thermal behavior of PVA composites, highlighting their piezoelectric and electro-active properties.

Findings

Nano-graphene enhances electrical conductivity near percolation threshold.

Electro-activity of PVdF grains affects internal electric fields.

Thermal transitions influence dielectric relaxation and conductivity.

Abstract

Nano-graphene /polymer composites can functionas 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 nanon-graphenes results from thecompetition among shorteningof the tunneling length and the increase of the polymer's polarizability. Such switching behaviorwas recentlyobserved inpolyvinyl alcohol (PVA) loaded withnano-graphene platelets (NGPs). In this work, PVA is blended withh alpha-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 macroscopicelectrical 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 Dielectricspectroscopy is employed to resolve and inspect electron transport and trapping with respect to thermal transitions and kineticprocessestraced 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 weakdependencies.