Effect of barium titanate particle filler on the performance of polyurethane-based dielectric elastomer actuators

Electroactive polymers are a major component of dielectric elastomer actuators (DEA). The performance of DEAs depends on the Young's modulus, dielectric constant and film thickness of the electroactive polymer as well as the compliance of the electrodes and the applied voltage. In literature mostly experiments on silicone- and acrylic-based DEAs are reported. However, better actuator performance can be expected with materials that have a higher dielectric constant. Therefore, unconventional electroactive polymers, such as polyurethane, chloroprene, or nitrile rubber, are currently attracting increasing interest for DEA applications. Besides their inherent dielectric properties, ferroelectric fillers embedded in the electroactive polymer can increase the dielectric constant even further. Provided that the filler concentration does not significantly increase the Young's modulus, ferroelectrically filled polymers can be expected to have a better actuator performance than standard materials. In this work, barium titanate particles with different concentrations were embedded in crosslinked polyurethane elastomer films. The hyperelastic material behavior of the polyurethane elastomer is represented by a Mooney-Rivlin model. Impedance spectroscopy is used to determine the dielectric constant of the electroactive compounds. Planar DEAs are designed from both unfilled and barium titanate-filled polyurethane films and compared with respect to their mechanical, dielectric, and actuator properties. The electric field response of unfilled and barium titanate-filled polyurethane-based DEAs is investigated experimentally and compared to an analytical solution of the actuator deformation. Additionally, a comparison between experimental DEA operation and an FEA prediction is carried out and discussed.