Dielectric elastomers are being developed for use in actuators, sensors and generators to be used in various applications,
such as artificial eye lids, pressure sensors and human motion energy generators. In order to obtain maximum efficiency,
the devices are operated at high electrical fields. This increases the likelihood for electrical breakdown significantly.
Hence, for many applications the performance of the dielectric elastomers is limited by this risk of failure, which is
triggered by several factors. Amongst others thermal effects may strongly influence the electrical breakdown strength.
In this study, we model the electrothermal breakdown in thin PDMS based dielectric elastomers in order to
evaluate the thermal mechanisms behind the electrical failures. The objective is to predict the operation range of PDMS
based dielectric elastomers with respect to the temperature at given electric field. We performed numerical analysis with
a quasi-steady state approximation to predict thermal runaway of dielectric elastomer films. We also studied
experimentally the effect of temperature on dielectric properties of different PDMS dielectric elastomers. Different films
with different percentages of silica and permittivity enhancing filler were selected for the measurements. From the
modeling based on the fitting of experimental data, it is found that the electrothermal breakdown of the materials is
strongly influenced by the increase in both dielectric permittivity and conductivity.
Liquid silicone rubbers (LSRs) have been shown to possess very favorable properties as dielectric electroactive polymers
due to their very high breakdown strengths (up to 170 V/μm) combined with their fast response, relatively high tear
strength, acceptable Young’s modulus as well as they can be filled with permittivity enhancing fillers. However, LSRs
possess large viscosity, especially when additional fillers are added. Therefore both mixing and coating of the required
thin films become difficult. The solution so far has been to use solvent to dilute the reaction mixture in order both to
ensure better particle dispersion as well as allowing for film formation properties. We show that the mechanical
properties of the films as well as the electrical breakdown strength can be affected, and that the control of the amount of
solvent throughout the coating process is essential for solvent borne processes. Another problem encountered when
adding solvent to the highly filled reaction mixture is the loss of tension in the material upon large deformations. These
losses are shown to be irreversible and happen within the first large-strain cycle.
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