A new soft dielectric silicone elastomer matrix with high mechanical integrity and low losses

Madsen, Frederikke Bahrt; Yu, Liyun; Daugaard, Anders Egede; Hvilsted, Søren; Skov, Anne Ladegaard

doi:10.1039/c4ra13511c

Cited by 85 publications

(82 citation statements)

References 35 publications

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“…A more sophisticated method of increasing the permittivity has been presented by Madsen et al, who covalently linked high-dielectric constant dipolar molecules to the elastomer backbone via a novel type of chain extender. [18,19] Nevertheless, none of the reported elastomers presently meets the requirements that are foreseen for a highly efficient, reliable and thus also commercially attractive dielectric elastomer. The indisputable need for materials improvement leads to many unconventional approaches for reaching a breakthrough in the development of dielectric elastomer actuators.…”

Section: Introductionmentioning

confidence: 99%

Glycerol as high‐permittivity liquid filler in dielectric silicone elastomers

Mazurek

Gerhard

et al. 2016

J of Applied Polymer Sci

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A recently reported novel class of elastomers was tested with respect to its dielectric properties.The new elastomer material is based on a commercially available polydimethylsiloxane (PDMS) composition, which has been modified by embedding glycerol droplets into its matrix. The approach has two major advantages that make the material useful in a dielectric actuator. First, the glycerol droplets efficiently enhance the dielectric constant which can reach astonishingly high values in the composite. Second, the liquid filler also acts as a softener that effectively decreases the elastic modulus of the composite. In combination with very low cost and easy preparation, the two property enhancements lead to an extremely attractive dielectric elastomer material. Experimental permittivity data are compared to various theoretical models that predict relative-permittivity changes as a function of filler loading, and the applicability of the models is discussed.

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Section: Introductionmentioning

confidence: 99%

Glycerol as high‐permittivity liquid filler in dielectric silicone elastomers

Mazurek

Gerhard

et al. 2016

J of Applied Polymer Sci

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“…TiO 2 -silicone composites have by far been the most commonly investigated elastomer system due to the availability of nanosized TiO 2 particles with various surface functionalizations. More complex approaches exist such as the covalent grafting of dipoles [11][12][13] and the creation of heterogeneous elastomers with hard and soft domains from controlled network formation [14][15][16][17]. Incorporating rigid fillers, such as titanium dioxide, into the cross-linked PDMS matrix increases the dielectric permittivity of the resulting composite elastomer.…”

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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“…Elastomer systems were prepared using two different approaches. The first approach was based on allyl-terminated chloropropyl-functional copolymers which were prepared according to a previously described procedure [11][12][13] . The allyl-groups on the copolymers allowed for platinum catalysed addition reactions with hydride-functional cross-linkers and thereby incorporation of the copolymers into the silicone network.…”

Section: Resultsmentioning

confidence: 99%

“…The procedures used for synthesising chloropropyl-functional copolymers have been previously described 11 . Two copolymers were prepared: one copolymer contained chloropropyl-groups with 1200 g mol −1 dimethylsiloxane spacer units between each group (ClCo-1), and the other copolymer contained chloropropylgroups with 580 g mol −1 dimethylsiloxane spacers between the functional groups (ClCo-2).…”

Section: Methodsmentioning

confidence: 99%

Super soft silicone elastomers with high dielectric permittivity

Madsen

Hvilsted

et al. 2015

SPIE Proceedings

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Dielectric elastomers (DEs) have many favourable properties. The obstacle of high driving voltages, however, limits the commercial viability of the technology at present. Driving voltage can be lowered by decreasing the Young's modulus and increasing the dielectric permittivity of silicone elastomers. A decrease in Young's modulus, however, is often accompanied by the loss of mechanical stability and thereby the lifetime of the DE. New soft elastomer matrices with high dielectric permittivity and low Young's modulus, with no loss of mechanical stability, were prepared by two different approaches using chloropropyl-functional silicone polymers. The first approach was based on synthesised chloropropyl-functional copolymers that were cross-linkable and thereby formed the basis of new silicone networks with high dielectric permittivity (e.g. a 43% increase). These networks were soft without compromising other important properties of DEs such as viscous and dielectric losses as well as electrical breakdown strength. The second approach was based on the addition of commercially available chloropropyl-functional silicone oil to commercial LSR silicone elastomer. Two-fold increase in permittivity was obtained by this method and the silicone oil decreased the Young's modulus significantly. The viscous losses, however, also increased with increasing content of silicone oil. Cross-linkable chloropropyl-functional copolymers offer a new silicone elastomer matrix that could form the basis of dielectric elastomers of the future, whereas the chloropropyl silicone oil approach is an easy tool for improvement of the properties of existing commercial silicone elastomers.

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A new soft dielectric silicone elastomer matrix with high mechanical integrity and low losses

Abstract: Alkyl chloride-functional siloxane copolymers are synthesised as the basis for a new soft matrix for dielectric elastomers.

Cited by 85 publications

References 35 publications

Glycerol as high‐permittivity liquid filler in dielectric silicone elastomers

Glycerol as high‐permittivity liquid filler in dielectric silicone elastomers

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

Super soft silicone elastomers with high dielectric permittivity

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