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

Dielectric elastomer (DE) pre-stretching is a key aspect of attaining better actuation performance, as ithelps prevent electromechanical instability (EMI) and usually lowers the Young’s modulus, thus leading toeasier deformation. The pre-stretched DE is not only susceptible to a high risk of tearing and the formationof mechanical defects, but films with sustained and substantial strain may also experience mechanicaldegradation.

In this study a long-term mechanical reliability study of DE is performed. Young’s mod-uli, dielectric breakdown strengths and dielectric permittivities of commercial silica-reinforced siliconeelastomers, with and without an additional 35% (35 phr) of titanium dioxide (TiO2), were investigatedafter being subjected to pre-stretching for various timespans at pre-stretches to strains of 60 and 120%,respectively.

The study shows that mechanical stability when pre-stretching is difficult to achieve withhighly filled elastomers. However, despite the negative outlook for metal oxide-filled silicone elastomers,the study paves the way for reliable dielectric elastomers by indicating that simply post-curing siliconeelastomers before use may increase reliability.