Temperature-frequency dependence of electrostrictive properties of a polyurethane elastomer

It was discovered recently that a large electric-field-induced strain can be obtained in several polyurethane elastomers which show promises for the applications in the transducers and actuators. In this study, electrostrictive properties of a polyurethane elastomer were investigated systematically. The elastic, dielectric and DSC spectroscopy analysis indicated the existence of two transition processes in the polyurethane from -50 °C to 80 °C. The field-induced strain coefficients exhibited large increases at the transition regions, indicating that the transition processes have a significant effect on the field-induced strain response. From the elastic and dielectric constant data, the contribution of uniform Maxwell stress was calculated. It was found that the contribution of the Maxwell stress effect to the measured strain coefficient increased from about 10% below the glass transition temperature, T_g, (approximately -25 °C) to about 50% and 35% for the frequencies of 10 Hz and 100 Hz, respectively, at approximately 40 °C, which is above T_g. The difference between the measured strain response and the calculated Maxwell stress effect indicates a significant contribution from other mechanisms such as electrostriction.