Simulation on Critical Frequency of Polymer in Electrostrictive Properties

The critical frequency and the relaxation time are analyzed through deformation and displacement during electrostriction which is induced by the electrical field at different frequencies. First, when the frequency is 50 Hz and the field strength is 2.5 kV mm−1, the electrostrictive displacement of polyethylene is 6.72 × 10−4 mm. After the data fitting, it is found that the displacement increases linearly with the square of field strength and that the proportional coefficient of 50 Hz is 1.08 × 10−4. Second, due to the influence of relaxation polarization and power loss, with the increase of frequency, the displacement and the proportional coefficient first increases then decreases, and when the frequency is 10 kHz, the displacement of 2.20 × 10−6 mm and the proportional coefficient of 3.51 × 10−7 have minimum values, which are 99.67% and 99.68% lower than that of 50 Hz, respectively. There is the critical frequency. Finally, based on the characteristic of anomalous dispersion, the relaxation time of polyethylene is 9.19 × 10−6s, which is in the time range of thermionic relaxation polarization and consistent with the actual situation. This analysis confirms the quantitative relationship between electrostrictive characteristics, field strength, and polarization. In addition, the relationship between frequency and strain is discussed, and the critical frequency in polymer and the relaxation time are confirmed.