Influence of the type of carbon nanocharges on the dielectric, mechanical and electroactive properties of polyurethane composites films
Résumé
Composites based on a polyurethane polymer matrix filled with various amounts of different types of nano-objects (carbon black, carbon nanotubes and graphene) were prepared and characterized. Such semi-crystalline polymers are very attractive for electromechanical applications as they can generate high strain levels under moderate electrical fieds. The use of conductive fillers is of a great interest because they effectively increase the electromechanical capabilities due to the enhanced relative permittivity. The dielectric constants of the nanocomposite films are presented with the help of the percolation theory and the critical exponents are discussed. It was found that the percolation thresholds depend on the size and shape of the nano-objects. Electromechanical capabilities of the nanocomposite films have been assessed by measuring the thickness strain under applied electric fields at low frequency with a laser interferometer. All composite films showed an improved electromechanical response as compared to the pure polymer.