DC breakdown investigation on polyurethane elastomeric films with and without deposited electrodes

Electroactive polymers (EAP) have recently drawn considerable attention, because of their potential use in wave energy converters, muscle-like actuators and as a material for applications in robotics and biomimetics. The widespread interest in electroactive polymers is primarily attributed to the electrostrictive effect that manifests in the stretching and compression of the soft polymer, when voltage is applied to the electrodes. The degree of deformation is proportional to the square of the applied electric field, therefore it is important to study the effect of high voltages on EAP. Our work presents a study on electrical breakdown characteristics of polyurethane (PU) - one of the most promising representatives of EAP, because of its high dielectric constant, combined with a high breakdown strength and low mechanical creep. Ramp and step-up breakdown tests were performed on PU films with and without compliant electrodes, in order to determine the breakdown strength of the samples. The investigation showed that the electrical behaviour of a PU film can be affected by the type of electrodes that are attached to the surface of the polymer. Gold sputtered electrodes have a good adhesion, but they do not stretch along with the PU film under voltage excitation. This results in cracks, reducing the performance of the electrode surface. PU samples with special compliant electrodes have lower breakdown voltages, but these electrodes can change their form along with the polymeric film. The results of plain PU films without applying compliant electrodes on the surface are presented as a reference.