Electrical breakdown in soft elastomers: Stiffness dependence in un-pre-stretched elastomers

Abstract

The relation between electrical breakdown and mechanical properties in soft polymeric materials is of particular interest for multiple applications, such as smart and flexible materials. In the literature, this relation is commonly investigated by variation of temperature, which indirectly causes a change in mechanical properties, but it also affects other factors that may influence the electrical breakdown, such as conductivity. Here, we present experiments that are performed at a constant temperature, on blends of chemically identical tri-block thermoplastic elastomers with different stiffnesses. Stress-strain measurements proved that continuous variation in mechanical properties could be obtained, here a range of 94 -316 kPa was found. Breakdown measurements found that the breakdown field increases with Youngs modulus. The results were compared to several theories in literature, however, only the recently proposed theory of [5] was found to explain the observations adequately.

The influence of static pre-stretching on the mechanical ageing of filled silicone rubbers for dielectric elastomer applications

“…The standard deviations were considerably greater for several samples, due to the non-uniformity of film thicknesses and defects contained in the prepared samples, while the major uncertainty of the breakdown data may also indicate bimodal distributions of breakdown strengths for several samples (see Figure 4 in SI). Nonetheless, the data in Table 2 confirm that the breakdown strengths lower in line with mechanical ageing, due to the decrease in the Young's modulus of the aged samples [43]. Normalized Breakdown strength …”

“…The thicknesses of the investigated films cannot be controlled precisely due to different PDMS formulation viscosities, and the variation in thicknesses can be seen in Table 1 in SI. Simultaneously, as mechanical properties change, breakdown strengths will also change [43], and as discussed previously the Young's moduli do not change monotonically. This behaviour is also observed within the determinations of breakdown strengths.…”

Self-Healing, High-Permittivity Silicone Dielectric Elastomer

“…The Si-B control sample is softer than Si-A due to lower crosslinking density and thus possesses slightly lower electrical breakdown strength. It is well known that the electrical breakdown performance of dielectric elastomers is influenced strongly by material conditions such as the Young's modulus, 21 applied pre-strain 20,22-24 and elastomer thickness. 22,24 Electrical breakdown strength values remain constant within experimental uncertainty, irrespective of the concentration of the added ionic network, the presence of which in the investigated concentrations therefore does not affect the overall breakdown strength of the materials.…”

The dielectric breakdown limit of silicone dielectric elastomer actuators

“…[1][2][3][4][5][6][7][8] The dielectric breakdown strength is the ultimate physical limit that hinders the possibility of actively stretching a dielectric elastomer up to its mechanical failure and, therefore, is of paramount importance in defining the actuator performance bounds. 4,9 It does not depend solely on the chemical properties of the material, but also on its physical properties such as mechanical stiffness, 10,11 thickness, [12][13][14][15][16][17] and stretch state, [18][19][20] the latter of great interest for dielectric elastomer actuators (DEAs) due to its beneficial effects on actuation. 4,9,20,21 In literature, the combined effect of thickness and pre-stretch on the breakdown strength of soft elastomers eligible to be used as actuators has been studied mostly for the acrylic elastomer VHB 4910, widely used for early implementations of dielectric elastomer actuators, thanks to its commercial availability as a bonding tape.…”