Dielectric and electromechanical properties of EAP/oxygen functionalized graphene nanocomposites
Résumé
Introducing carbon based nanomaterials into electroactive polymers (EAPs) is an attractive method to enhance their performance as actuators by reducing the applied electrical field for an expected deformation. Oxygen functionalized graphene nanoplatelets were then added into polyurethane polymer to form PU/OFG composites. It is observed indeed an increase of the dielectric permittivity, with a moderate mechanical reinforcement. The factor of merit of the electrical field induced strain versus electrical field, defined as permittivity/Young's modulus ratio, is then favorable for actuation performances. However, measured electromechanical coefficient values with “Bender” method under 10 MV m -1 are not in agreement with the excepted values calculated from data acquired at low (0.007 MV m -1 for permittivity measurement) or null electrical field values (Young's modulus measurement). It is recalled in this work that to predict the actuator performance, the consideration of dielectric and mechanical properties at high electrical fields is of prime importance, especially at low frequency. The effect of electrical field on permittivity can explain the results for pure PU but differences persist for PU-OFG composites. The conductivity behavior, as well as the interfacial cohesion between graphene nanoplatelets and the polyurethane matrix can also play a role in the actuation properties.