Silicone rubbers for dielectric elastomers with improved dielectric and mechanical properties as a result of substituting silica with titanium dioxide

Yu, Liyun; Skov, Anne Ladegaard

doi:10.1080/19475411.2015.1119216

Cited by 49 publications

(42 citation statements)

References 47 publications

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“…Since -in practice -it is impossible to avoid defects, E B depends strongly on elastomer fi lm thickness, since the number of defects scales with volume and thus thickness. [ 67 ] Furthermore, it is important that the material exhibits low dielectric losses, which continuously contribute to the generation of heat in the material. If heat generated by these dielectric losses exceeds heat dissipated in to the surrounding area, the temperature in the elastomer will rise, which in turn could lead to thermal breakdown.…”

Section: Dielectric Elastomer Parametersmentioning

confidence: 99%

The Current State of Silicone-Based Dielectric Elastomer Transducers

Madsen

Daugaard

Hvilsted

et al. 2016

Macromol. Rapid Commun.

350

392

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Silicone elastomers are promising materials for dielectric elastomer transducers (DETs) due to superior properties such as high efficiency, reliability and fast response times. DETs consist of thin elastomer films sandwiched between compliant electrodes, and they constitute an interesting class of transducer due to their inherent lightweight and potentially large strains. For the field to progress towards industrial implementation, a leap in material development is required, specifically targeting longer lifetime and higher energy densities to provide more efficient transduction at lower driving voltages. In this review the current state of silicone elastomers for DETs is summarised and critically discussed, including commercial elastomers, composites, polymer blends, grafted elastomers and complex network structures. For future developments in the field it is essential that all aspects of the elastomer are taken into account, namely dielectric losses, lifetime and the very often ignored polymer network integrity and stability.Complete Manuscript

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Section: Dielectric Elastomer Parametersmentioning

confidence: 99%

The Current State of Silicone-Based Dielectric Elastomer Transducers

Madsen

Daugaard

Hvilsted

et al. 2016

Macromol. Rapid Commun.

350

392

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“…Incorporating rigid fillers, such as titanium dioxide, into the cross-linked PDMS matrix increases the dielectric permittivity of the resulting composite elastomer. Mechanical properties are also affected, with results varying according to particle size and surface treatment, from reinforcing to softening [18][19][20][21][22]. On the other hand, a thinly filled elastic film that maintains high strain for a given period of time will, to some extent, suffer mechanical ageing at the microscopic level.…”

Section: Introductionmentioning

confidence: 99%

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

Zakaria

Kofod³

et al. 2015

Materials Today Communications

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Dielectric elastomer (DE) pre-stretching is a key aspect of attaining better actuation performance, as it helps prevent electromechanical instability (EMI) and usually lowers the Young's modulus, thus leading to easier deformation. The pre-stretched DE is not only susceptible to a high risk of tearing and the formation of mechanical defects, but films with sustained and substantial strain may also experience mechanical degradation. In this study a long-term mechanical reliability study of DE is performed. Young's moduli, dielectric breakdown strengths and dielectric permittivities of commercial silica-reinforced silicone elastomers, with and without an additional 35% (35 phr) of titanium dioxide (TiO 2 ), were investigated after 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 prestretching is difficult to achieve with highly 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 silicone elastomers before use may increase reliability. 1 INTRODUCTIONThe reliability of dielectric elastomer (DE) transducers depends on the types of material used, as well as fabrication techniques and design and transducer operating conditions (such as maximum stretching, applied frequency and amplitude of the applied voltage). The acrylic double-adhesive VHB 4910, produced by 3M, is one of the best-performing elastomers with respect to actuation strain (s) at a given applied field, and it chiefly outperforms silicone-based elastomers over short time scales. Silicone elastomers, however, possess a faster actuation response as well as reliability over time, since performance remains more or less unaltered up to about 10 million cycles when pre-stretching is avoided.[1] Pre-stretching is well-known to be a prerequisite for the actuation of acrylic-based elastomers, since it simultaneously reduces thickness, decreases the Young's modulus and suppresses electro-mechanical instability (EMI). Pre-stretching has also been shown to cause the alignment of elastomer chains in the plane of stretching.[5] This alignment, which is perpendicular to the direction of the electric field, leads to an increase in breakdown strength, because charge carrier movement is impeded.[6] For acrylics, pre-stretching is also favourable due to strain-softening, whereas for silicone elastomers the elastomer usually does not show the same tendency and in many cases strain-hardening behaviour actually sets in. However, pre-stretching remains very favourable for silicone elastomers, as largely improved actuation strains can be obtained through the avoidance of EMI.The most common failure modes of DE transducers are pull-in instability, dielectrical breakdown and material strength failure [7,8]. Electromechanical pull-in instability, also known as electromechanical instability (EMI), was identified by Stark a...

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“…[56] 6. Losses are not directly included in the expressions but rather indirectly by limiting filler loadings for which losses become significant (by using rules of thumb).…”

Section: Quantitative Comparison Of the Four Permittivity-enhancing Mmentioning

confidence: 99%

Optimization Techniques for Improving the Performance of Silicone‐Based Dielectric Elastomers

Skov

2017

Adv Eng Mater

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Dielectric elastomers are possible candidates for realizing products that are in high demand by society, such as soft robotics and prosthetics, tactile displays, and smart wearables. Diverse and advanced products based on dielectric elastomers are available; however, no elastomer has proven ideal for all types of products. Silicone elastomers, though, are the most promising type of elastomer when viewed from a reliability perspective, since in normal conditions they do not undergo any chemical degradation or mechanical ageing/relaxation. Within this review, different pathways for improving the electro-mechanical performance of dielectric elastomers are highlighted. Various optimization methods for improved energy transduction are investigated and discussed, with special emphasis placed on the promise each method holds. The compositing and blending of elastomers are shown to be simple, versatile methods that can solve a number of optimization issues. More complicated methods, involving chemical modification of the silicone backbone as well as controlling the network structure for improved mechanical properties, are shown to solve yet more issues. From the analysis, it is obvious that there is not a single optimization technique that will lead to the universal optimization of dielectric elastomer films, though each method may lead to elastomers with certain features, and thus certain potentials.

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Silicone rubbers for dielectric elastomers with improved dielectric and mechanical properties as a result of substituting silica with titanium dioxide

Cited by 49 publications

References 47 publications

The Current State of Silicone-Based Dielectric Elastomer Transducers

The Current State of Silicone-Based Dielectric Elastomer Transducers

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

Optimization Techniques for Improving the Performance of Silicone‐Based Dielectric Elastomers

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