WO2021043588A1

WO2021043588A1 - Elastic dielectric with microscale pores, use and manufacturing method

Info

Publication number: WO2021043588A1
Application number: PCT/EP2020/073381
Authority: WO
Inventors: Urs Hunziker; Karl Rametsteiner
Original assignee: Brainchain Ag
Priority date: 2019-09-05
Filing date: 2020-08-20
Publication date: 2021-03-11
Also published as: DE102019123898B4; DE102019123898A1

Abstract

The invention describes an elastic dielectric (130) which has an elastic polymer (190) and a plurality of pores (180). The plurality of pores (180) have an average pore diameter (d) of 50 pm or less, and the plurality of pores (180) have a total pore volume which makes up 60% or less of the total volume of the elastic dielectric (130). The invention further relates to a use of the elastic dielectric (130), a dielectric device (100), a method for manufacturing an elastic dielectric (130), and a use of an electric insulator.

Description

Elastic dielectric with microscopic pores, use and

production method

The invention relates to an elastic dielectric. In particular, the invention relates to using the elastic dielectric. The invention also relates to a dielectric device, in particular a dielectric actuator and / or a dielectric sensor. The invention also relates to a method for producing the elastic dielectric. The invention also relates to using an electrical insulator.

The invention can thus relate to the technical field of elastic dielectrics. Furthermore, the invention can relate to dielectric devices. In particular, the invention can relate to the technical field of dielectric (elastomer) actuators and / or dielectric (elastomer) sensors. More particularly, the invention can relate to the technical field of the use of special insulators with respect to dielectric devices.

A dielectric device such as a dielectric (elastomer) actuator (DEA), a dielectric (elastomer) sensor (DES) or a mixed form (DEAS) is basically constructed like a flexible electrostatic capacitor. A (with regard to electromechanical aspects essentially) passive elastomer layer (or a polymer layer) is clamped between two electrode plates. When an electrical voltage U is applied (i.e. in the operating mode), the opposing electrode plates attract each other due to the electrostatic pressure (p _{e /} ). The incompressible elastomer layer is then compressed in the vertical direction and expands in the lateral direction (surface expansion). The electrostatic pressure that causes the deformation is determined by the dielectric constant, the relative permittivity, and the thickness of the material as well as the voltage applied.

The equivalent electromechanical pressure p _eq occurring in the operating mode is twice as large as the electrostatic pressure p _ei and can be calculated as: Peq = eo * e _G * (u ² / z ² ), where eo is the permittivity of the vacuum, e _{G is} the dielectric constant, and z is the layer thickness of the elastomer layer.

The movement is thus generated by the electrostatic forces that act on the elastomer layer between two electrode plates. In one example, a dielectric actuator achieves an elongation of up to 20% at a field strength of 30 V / pm. Usual unidirectional expansions of dielectric actuators are e.g. in the range 10 to 35%, maximum values up to 300%.

Since the elastomer layer is almost incompressible, the volume remains in principle constant during the deformation. When the voltage is reduced, the excess charges flow away via the voltage source, so that the elastomer layer returns to its original shape and can exert forces due to the stored elastic energy.

This principle can be used both as an actuator and as a sensor and offers a number of promising technical application possibilities. Particular advantages of these dielectric devices can be that they can be light, flexible and noiseless and also cause low material costs. However, these advantageous possible applications are currently opposed to unresolved issues relating to production and reliability.

In the event of a mechanical deformation of a dielectric device, the elastic dielectric material is displaced to the side due to a lack of compressible properties, which can negatively affect both the mechanical properties and the linearity.

In order to counteract this problem, foams are used as a dielectric in the prior art. However, this brings with it many technical disadvantages such as a low dielectric strength, a short service life (especially with a high electrical potential), and electrical field distortions. Furthermore, the problem of partial discharges also leads to component failure over time. In this document, the term "dielectric strength" can be understood to mean in particular that electrical field strength of a dielectric which may at most be present in the material (e.g. elastic polymer) without a voltage breakdown (e.g. electric arc or spark) occurring eg as breakdown field strength (kV / mm or kV / pm), which is calculated from the maximum voltage or breakdown voltage (in volts) based on the thickness (eg mm or pm area) of the dielectric.

In this context, the term "partial discharges" can denote any form of plasma or breakdown effects, Elms fires or breakthroughs due to electrical potential differences. These can result in the immediate or slow destruction of the electrical and / or mechanical properties of a dielectric.

With special foams known from electrical engineering (e.g. gap fillers, thermally conductive foam and gel foils), high dielectric strengths of around 4 kV / mm can be achieved. However, because of their mechanical properties, these foams are unsuitable for use as a dielectric (in particular not in a dielectric device).

It is an object of the present invention to provide an elastic dielectric (particularly suitable for efficient use in a dielectric device) which has a high dielectric strength, is robust against partial discharges, and is particularly durable.

This object is achieved by the subjects according to the independent patent claims. Preferred configurations emerge from the dependent claims.

According to one aspect of the present invention, an elastic dielectric is described which has an elastic polymer and a plurality of pores (in particular within the elastic polymer). The majority of Pore has a mean (or average) pore diameter of 50 mhh or less (in particular 20 μm or less). Furthermore, the plurality of pores has a total pore volume which makes up 60% or less (in particular 40% or less) of the total volume of the elastic dielectric (in particular the total volume of the elastic polymer).

According to a further aspect of the present invention, a use of the above-mentioned elastic dielectric is described in at least one of the group consisting of: a dielectric device (in particular a dielectric sensor and / or a dielectric actuator), a cable, a capacitor, a Vibration damper, an electromechanical system.

According to a further aspect of the present invention, a dielectric device (in particular a dielectric actuator and / or a dielectric sensor) is described (which is designed as a stack system). The dielectric device has: i) a plurality of electrodes, each of which has: a functional region which is formed along two main directions of extent (x, y) and spans a first plane, and ii) a plurality of elastic dielectrics, each dielectric is formed along the two main directions of extent (x, y) and spans a second plane. The electrodes and the elastic dielectrics are arranged alternately. At least one dielectric of the plurality of elastic dielectrics is an elastic dielectric (in particular with a pore configuration) as described above.

According to a further aspect of the present invention, a method for producing an elastic dielectric (in particular for a dielectric device, further in particular a dielectric actuator and / or sensor) is described. The method comprises: i) providing a (in particular elastic) polymer as the base material, and ii) forming a plurality of pores in the base material such that the plurality of pores has an average pore diameter of 50 μm or less, and the total pore volume of the plurality of pores is 60% or less of the total volume of the elastic dielectric.

According to a further aspect of the present invention, the use of an electrical insulator (for example a dielectric) is described which has (or has) an elastic polymer which has a plurality of gas bubbles (or gas (in particular air) -filled pores) mean pore diameter is 20 μm or less and the total pore volume of which makes up 40% or less of the total volume of the electrical insulator, as a dielectric in a dielectric actuator and / or a dielectric sensor.

In the context of this document, the term "dielectric (elastomer) actuator (DEA)" can be understood to mean, in particular, an actuator which consists of two electrodes and an intermediate spring-based or elasticity-based dielectric spacer, in particular made of elastomer material Understand the interplay of the spring forces between the electrodes (plates) on the one hand and the Coulomb attraction between the electrodes on the other.

In the context of this document, the term "dielectric (elastomer) sensor (DES)" can be understood to mean, in particular, a sensor which consists of two electrodes and an intermediate spring-based or elasticity-based dielectric spacer, in particular made of elastomer material capacity determined by the electrode spacing, or by the change in capacitance resulting from changes in the distance between the electrodes.

In the context of this document, the term "dielectric (elastomer) actuator and sensor (DEAS)" can be understood to mean, in particular, a combination of the principles of DEA and DES in one system. Features that apply to a DEA can also apply to a DES and vice versa.

In the context of this document, the described coordinate system can be understood such that the directions x and y (as Main extension directions) span the surface of an electrode and the height direction z is aligned for this purpose along the distance direction of two opposing (parallel aligned) electrodes. In one embodiment with regard to a manufacturing process, x can correspond to the width (cross-direction (CD) in a reel-to-reel production) and y to the processing direction (machine direction (MD) in a reel-to-reel production).

In the context of this document, the term “electrode” can in particular be understood to mean an electron conductor which is connected to a counter electrode (then referred to as anode and cathode, or as a plus pole and a minus pole) via a (dielectric) medium located between the two electrodes In this way, an electric field can be generated between the electrodes. In this case, an electrode can have a “functional (active) area” or else consist entirely of the functional area. The functional area is electrically conductive (in particular comprising a metal) and can thus form the active part of the electrode, which interacts electrically with the counter-electrode. Furthermore, an electrode can have an electrically non-conductive area, e.g. a carrier material, to which the functional area (e.g. as a metal foil) is applied. Furthermore, an electrode can have an (electrically conductive) contact area to which contact can be made with the electrode or to which a voltage can be applied. According to one embodiment, the metal of the electrode (or of the functional area) is at least one from the group consisting of: Ag, Al, Au, Be, Cr, Cu, Fe, In, Mg, Mo, Ni, Pb, Pd ,

Pt, Rh, Sb, Sn, Ti, Zn, and alloys thereof. Alloy components below 2% by weight can also consist of other metals (e.g. Si, As, etc.). Alloys can include, for example: iron alloy, brass, bronze, stainless steel, aluminum, etc. In order to avoid incompatibilities (e.g. copper on polymer), metal multilayer structures are also possible.

In the context of this document, the term “dielectric” (or insulator) can in particular denote any material (or substance) in which charge carriers are essentially not freely movable an electrically weakly conductive to non-conductive property. A dielectric can, for example, be a polymer, in particular an elastomer. A dielectric cannot be a metal. With regard to a dielectric device, the dielectric can be an elastic dielectric, for example a dielectric polymer (DE). Dielectric polymers, along with piezoelectric polymers and electrostrictive polymers, are also known as electroactive polymers (EAP).

In one embodiment, to produce a dielectric, material of an elastic polymer (in particular elastomer material) is applied in uncured form (in particular on an electrode) and then cured. In this document, the term “hardening” can be understood to mean in particular a multitude of different forms of material hardening or an increase in material viscosity. In a hardening process, a material can change from a first state to a second state, the material being in the second state is more solid than in the first state. Furthermore, the viscosity of the first state can be significantly lower than the viscosity of the second state. Curing can include, for example, at least one of the following processes: crosslinking, thermal solidification processes, drying reactions, gelation processes. In one example, a non-cured, at least partially liquid elastomer material (e.g. in a solvent or a suspension medium) applied to an electrode (or a carrier film) during curing (e.g. by drying the solvent / suspension medium and / or crosslinking the elastomer material as, in particular a specifically controlled crosslinking e.g. by means of UV radiation), the elastomer material can have an essentially more solid form and / or have a higher viscosity than the uncured elastomer material. In particular, the cured elastomer material can be used as a dielectric.

The curing can be carried out, for example, by means of a crosslinking reaction and / or film formation by drying from solution and / or film formation by drying from a dispersion. With regard to networking, this can be done with at least one of the following processes the following are carried out: i) radiation crosslinking (preferably by UV radiation), ii) electron crosslinking (eg by an electron beam source), iii) thermally initiated radical crosslinking, iv) thermal sulfur crosslinking, v) peroxide initiated radical crosslinking.

In the context of this document, the term “pores” can denote in particular any type of cavity within a dielectric (or insulator), in particular the elastic polymer of the dielectric. The term “pores” can mean a (discrete) cavity within the elastic polymer matrix of a dielectric describe. The term “pore” can be synonymous with “bubble”. The pores can be fluid (in particular air) filled or evacuated. In a preferred example, the pores have a pore diameter in the micro-scale or nano-scale range The pores are particularly preferably designed as discrete cavities. This can be understood to mean that the majority of the cavities do not coagulate, but that the majority of the pores are spatially separated from one another (by the material of the elastic polymer). The pores are preferably not part The term “foam or foams” can in particular denote that open-line gas bubbles are present in a base material, with only thin cell walls made of the base material being present between the gas bubbles. These gas bubbles in foam can thus be described as coagulating and not as discrete. The dielectric described, on the other hand, preferably consists of the elastic polymer base material which contains isolated pores that are encapsulated in large volumes by the base material (that is, discrete and non-coagulating). Compared to foams, this can result in completely different electrical and / or mechanical properties.

In the context of this document, the term "pores" relates in particular to the total pore volume, that is to say to the totality of the pores in the elastic polymer of the dielectric. In a preferred embodiment, this total of pores in the elastic polymer has a total pore volume which is 60% ( in particular 40%) or less of the total volume of the elastic dielectric. The pores are designed as discrete cavities. By means of these formulations, foams be excluded. According to the invention, a robust dielectric is preferably described which has isolated (discrete) pores in the form of cavities with a small total pore volume and which does not represent any foam. In particular, the term “pores” in this document does not refer to embedded particles, full-cell structures, or undesired gas bubbles.

According to an exemplary embodiment, the invention can be based on the idea that an elastic dielectric (in particular for a dielectric device) can be provided, which has a high dielectric strength, is robust against partial discharges, and is particularly long-lived by the elastic polymer of the dielectric with micro (or nano) -scalines (ie average pore diameter 50 μm or less) pores (in particular air-filled gas bubbles) is provided, which only require part of the dielectric volume (total pore volume 60% (in particular 40%) or less in relation to the Total dielectric volume).

The dielectric with the actually incompressible elastic polymer and the described pore configuration thus shows (pseudo) compressible properties with a high dielectric strength at the same time. The micro (nano) -scaline gas bubbles can be distributed in the dielectric in such a way that field distortions are minimized and at the same time a displacement space is created for mechanical stress. The molecular chain movements of the elastic polymer can be reduced in such a way that a particularly long (material) service life is created.

It has been shown, completely surprisingly, that the combination of micro (or nano) -scaline pores (or gas bubbles) with a significantly reduced total pore volume proportion leads to a derivation of force influences due to external mechanical factors (pseudo-compressible behavior) and, at the same time, a minimal field distortion to ensure a particularly high dielectric strength or dielectric strength. With these properties, the described dielectric can be installed particularly advantageously in a dielectric device (as described above) and thus enable the provision of dielectric devices with a (pseudo) compressible dielectric, which nevertheless does not show any large field distortions, has a high dielectric strength, and so that it counteracts premature signs of aging.

According to one exemplary embodiment, the pores are fluid-filled (in particular gas-filled, furthermore in particular air-filled). This has the advantage that the dielectric exhibits particularly efficient (pseudo) compressible properties. The pores can be completely or partially (e.g. residual liquids in addition to the gas) gas-filled.

According to a further exemplary embodiment, the plurality of pores has an average pore diameter of 20 μm or less (in particular 10 μm or less, further in particular 1 μm or less). This has the advantage that the dielectric strength (in particular with regard to partial discharges) can be improved particularly efficiently.

According to a further exemplary embodiment, the total pore volume makes up 40% or less (in particular 25% or less, further in particular 12% or less, further in particular 8% or less) of the total volume of the elastic dielectric. This has the advantage that the dielectric has particularly efficient and robust (pseudo) compressible properties. In particular, the displacement space can thus be delimited in an advantageous manner in a targeted manner.

According to one exemplary embodiment, the pores can be (essentially) highly closed pores, so that there is no rapid gas exchange with the environment in the case of pulsed compression. For this reason, it can be advisable to choose the pore volume as a proportion of the dielectric in such a way that the pressure increase in the pores during compression fits optimally into a dielectric device. For example, with a total pore volume of 10% and a deflection of the actuator by 5% in the vertical direction, the pressure in the pores can increase double that. This increase in pressure can be sufficient to experience noticeable effects of adiabatic compression, which corresponds to a reduction in efficiency by heating the air in the pores. If dielectric devices remain in the compressed state slowly or for an extended period of time, heat can be given off into the environment (and vice versa).

According to a further exemplary embodiment, the total pore volume makes up at least 5%, in particular at least 2.5%, further in particular at least 1%, further in particular at least 0.5%, further in particular at least 0.01%, of the total volume of the elastic dielectric.

According to a further exemplary embodiment, the pores are (essentially) distributed homogeneously in the elastic dielectric.

According to one exemplary embodiment, it has been shown that, in addition to the measures mentioned, a homogeneous distribution of the pores can also be advantageous for the overall performance of the dielectric or a dielectric device. Preferably, pore formation mechanisms can be used during production which, by virtue of their operating principle, promote or contain a homogeneous fine distribution of the pores. An example of this can be the action of hyperbaric CO2, which diffuses into a thin (preferably not yet or not yet fully crosslinked) dielectric layer (or polymer base material) and (preferably during crosslinking, so that the pore mobility remains low and none Pore coagulation occurs) then expanded in a controlled manner to form gas bubbles.

This described (highly) homogeneous distribution of the pores can allow the dielectric to react to the next pore with minimal volume movements during mechanical loads. This next pore can be provided a suitable compression or expansion space for the total volume changed in height direction by external force in an operating mode. It has been recognized that this high degree of homogenization can ensure that the molecular chains rubbing against one another in an elastic polymer under dynamic loading have a minimal effect Experience the friction path. Since every rubbing of molecular chains against each other increases the risk of chemical changes (e.g. through reorganization of molecular chains), any mechanical deformation load can fundamentally affect the service life. In particular, loads at the upper limit of elastic extensibility and high numbers of strokes reduce the service life. This effect is shown by the use of the dielectric as an insulator, ie when the insulator is "under voltage" it is also negative Service life and an improvement in resistance to aging, especially under dynamic stress. The advantage can also be noticeable under static mechanical stress. In addition, this described effect and the related relationships can also apply to coiled molecular chains.

According to a further exemplary embodiment, the mean distance (r) between at least 50% (in particular at least 90%, further in particular 97%) of the pores of the plurality of pores is greater than half the mean diameter (d) of the plurality of pores.

In another example, the mean distance (r) between at least 50% (in particular at least 90%, further in particular 97%) of the pores of the plurality of pores is greater than the mean diameter (d) of the plurality of pores.

According to a further exemplary embodiment, the pores are distributed in the elastic dielectric in such a way that 10% or less (in particular 1% or less, further in particular 0.1% or less) of the pores coagulate.

In one example it has been shown that the dielectric strength or dielectric strength can mainly depend on the homogeneous distribution of the pores. If the pore generation is not caused by nuclei (e.g. hyperbaric CO2, which principle penetrates an as yet non-crosslinked elastomer in a uniformly distributed manner and thus implicitly enters into a natural uniform distribution), methods and mechanisms are available to achieve a to achieve such uniform distribution before pore formation (e.g. by ultrasound or microwave) and then to maintain this uniform distribution until crosslinking.

In one example, it was achieved that only a few pores coagulate, which can indirectly be a measure of the homogeneous distribution of the pore-forming nuclei. It was thus achieved that less than 10%, with special care even less than 1%, or less than 0.1%, of the pores coagulate. Further investigations have shown that with such a homogeneous distribution the mean distance for 50% of the pores can be larger than the mean pore diameter; with certain elastomers this reference applies to over 90% of the pores, and in the case of particularly pronounced homogenization measures to over 97% of the pores Pores.

According to a further exemplary embodiment, the elastic polymer has at least one from the group consisting of: i) a diene polymer (in particular at least one of butadiene, isoprene, dimethylbutadiene, halobutadiene, cyclopentadiene, cyclooctadiene), ii) an elastomer with a 1 , 2 and / or 1,4 linkage in cis and / or trans form, iii) a copolymer with monounsaturated monomers (in particular one of styrene, ethene, propene, butene, acrylonitrile, acrylic acid, acrylic acid esters, vinyl ethers, vinyl esters, vinyl halides ), iv) a thermoplastic elastomer (in particular a crosslinked thermoplastic elastomer), v) a polyaddition elastomer (in particular polyurethane or a silicone elastomer), vi) an elastomer which was subsequently crosslinked (in particular by means of one from the group consisting of sulfur, peroxide , UV radiation, photoinitiators), vii) a polymer mixture of at least two of the above-mentioned elastomers. In one example, the elastomer comprises natural rubber (NR) or a derivative thereof. In a further example, the elastomer has nitrile butadiene rubber (NBR) or a derivative thereof. These embodiments can have the advantage that tried and tested industrial materials can be used directly.

It has been shown that particularly desirable results can be achieved with the following elastomers: 1. Elastomers which are present as polymers of dienes, such as butadiene, isoprene, dimethylbutadiene, halobutadiene, cyclopentadiene, cyclohexadiene, cyclooctadiene, etc.

2. Elastomers which are 1,2 and / or 1,4 linkages, both in cis and / or trans form.

3. Elastomers, which are present as copolymers with monounsaturated monomers such as: styrene, ethene, propene, butene, acrylonitrile, acrylic acid (esters), vinyl ethers, vinyl esters, vinyl halides, etc.

4. Elastomers which have been subjected to subsequent crosslinking using sulfur, peroxide, UV light and photoinitiators and other free-radical-initiated methods. Such polymers are known and can be used as non-crosslinked rubbers (e.g. NR, EPDM, SBR, NBR, HNBR, XNBR, HXNBR, BR, EVA, etc.).

5. Thermoplastic elastomers (TPEs) that can be subsequently crosslinked are also suitable.

6. Furthermore, polyaddition elastomers such as polyurethanes or silicone elastomers based on the Pt addition process (also by means of peroxide crosslinking) are suitable.

7. In addition, mixtures (polymer alloys) of the elastomers mentioned above are also included in the context of the invention, as well as elastomer mixtures with high-boiling solvents and "extenders" such as paraffins, waxes, carbonic acid esters, plasticizers, etc., insofar as they meet the general requirements as dielectric elastomers.

Irrespective of this, very good effects were achieved with elastic dielectrics, which are based on the use of elastomers with functional groups that increase the dielectric constant (DEK) accordingly. Such are, for example, nitrile rubber (NBR) and / or its derivatives such as HNBR, XNBR, HXNBR. The rule here is that an increased nitrile content can increase the rigidity / hardness, but at the same time can increase the DEK. This increase in stiffness can thus be compensated for with the pore proportion described. In addition, a homogeneous product is retained that is free of punctual foreign substances that cause a correspondingly unfavorable field distortion and promote breakdown. The use of dielectrics with functional groups to increase the dielectric constant can be associated with an increased degree of crosslinking go, which in turn improves the fatigue strength in terms of aging, oxidation and heat, even if the dielectric could be stiffened somewhat.

According to a further exemplary embodiment, the elastic dielectric has a dielectric strength of 5 kV / mm or more (in particular of 12 kV / mm or more, further in particular of 16 kV / mm or more). The aforementioned particularly advantageous dielectric strength can be achieved through the selection or configuration of the pores described above.

Due to the described (in particular very isolated (discrete)) pores with a very small diameter, the field inhomogeneity in the dielectric can be reduced and very high dielectric strengths of over 5 kV / mm, in particular over 16 kV / mm, can be achieved. In foil form, the dielectric strengths can be higher by a factor of approximately three, because the thinner the dielectric, the higher the dielectric strength (and the associated partial discharge problem).

According to a further exemplary embodiment, the elastic dielectric has a thickness of 100 μm or less (in particular 70 μm (50 μm, 40 μm, 20 μm) or less). According to a further exemplary embodiment, the elastic dielectric has a dielectric strength of 15 V / pm or more (in particular 36 V / pm or more, further in particular 48 V / pm or more). Due to the configuration of the pores described above, a particularly advantageous dielectric strength can also be achieved for very thin dielectrics (which in turn enable particularly advantageous dielectric devices).

According to a further exemplary embodiment, the elastic dielectric has: a capacitance-increasing additive (in particular a ferroelectric dielectric additive which crystallizes in the perovskite manner, further in particular a titanate). This has the advantage that the capacity can be increased. The described pore design can counteract hardening of the polymer by the additive. In one example, a heterogeneous dielectric can be provided by mixing in capacitance-increasing substances. These can be ferroelectric dielectrics that _{crystallize in perovskite (CaTi0 3} ) type. These are (mixed) oxides of e.g. Ba, Sr, Pb and titanate (e.g. BaTiOs). The perovskite structure is a well-known type of structure for compounds such as ferroelectrics. These can be very hard and specifically heavy, so that hardening of the dielectric can be determined. Despite the addition of capacity-increasing additives, in one example the effect of hardness (and thus an increase in the modulus of elasticity) can be counteracted by means of the above-described pore design of the elastomer.

According to a further exemplary embodiment, the elastic dielectric has: a fluoropolymer, in particular polytetrafluoroethylene (PTFE). This has the advantage that, in specific applications, the sliding ability and / or the resilience of the elastic polymer can be improved.

In one embodiment, the dielectric is used as an insulator in an electrical cable (or e.g., a vibration damper). For this embodiment variant (s), a fluoropolymer such as PTFE is preferably added as an additive to the elastic polymer. This can bring about the following additional positive changes in properties: i) improved sliding ability between the dielectric and further layers in a cable, ii) improved resilience in the elastic polymer in the event of mechanical expansion or compression.

According to a further exemplary embodiment, the elastic dielectric is (essentially) designed as an integral foam. In particular, the elastic dielectric has a (essentially) closed outer layer. This has the advantage that the dielectric is protected against partial discharges in the outer area (in particular when used in a dielectric device between two electrodes).

For example, a type of foam that has a closed outer skin (or outer layer) and decreases in density towards the inside can be referred to as integral foam. The term “integral foam” preferably relates in this However, document on the characteristic of the outer layer and not on the density variation.

In one embodiment, the dielectric is designed analogously to an integral foam (with regard to the outer layer). The fact that there are (essentially) no pores on the surface of the dielectric (or of the elastic polymer) can prevent partial discharge effects (in particular Elmsfeuer) from occurring on the electrode of a dielectric device. An exemplary process for this would be "reaction injection molding" (RIM). The pore-free zone is kept at a lower temperature than the rest of the dielectric. The lower temperature results in significantly weaker pore formation, which is surprising for the mentioned effect of the outer layer can already be enough.

According to a further exemplary embodiment, the elastic dielectric is formed along two main directions of extent (x, y), which span a plane, and the elastic dielectric is set up in an operating mode to carry out a change in length in a height direction (z) which is perpendicular to the main directions of extent (x, y) is oriented. This has the advantage that the dielectric described can advantageously be used as an actuator and / or sensor in a large number of applications.

According to a further exemplary embodiment, the elastic dielectric is set up to carry out a change in length of 1% or more (in particular 3% or more, further in particular 5% or more) in an operating mode in at least one spatial direction. Furthermore, the elastic dielectric is set up to carry out a plurality of the changes in length.

According to one embodiment, the described pore configuration (in particular also due to the highly homogeneous distribution of the pores) can be used to improve the electrical properties as well as an improvement in the mechanical properties: the already described close proximity to the next pore for each elastomer molecule Volume change compensation has other additional effects: the reduced bond load on the molecular chains can result in good resilience of the elastomer (or the elastic polymer). This is especially true for long-term fluctuating loads. In addition, it was found that the tendency to creep can be reduced.

This reduction in a mechanical fatigue effect can be particularly evident in the case of larger mechanical deflections in the dielectric. Improvements in the mechanical properties mentioned were found when the elastomer experiences a change in length of more than 1%, preferably more than 3%, particularly preferably more than 5%, in at least one direction. Mechanical alternating stresses can also be better tolerated by the design described. It was found that the dielectric allows the mentioned change in length several times, very often with adequate design and has consistently better mechanical properties compared to comparable products.

In one embodiment, the dielectric is used to produce a dielectric actuator and / or a dielectric sensor (DEAS). Particularly for DEAS with high dynamic loads, it has been shown that both the aging behavior and the dielectric strength could be optimized and the pores are also suitable for absorbing the excess volume in the elastic polymer of the dielectric that is created during the DEAS compression.

In a further exemplary embodiment, the elastic dielectric is used to produce an electrical cable, in particular which is designed for high voltage loads and at the same time has a high long-term load cycle strength and / or an improved cross-sectional stability. In terms of cross-sectional stability, the pores can compensate for the volume of material displaced or expanded during bending. Thereby, the formation of an oval deformation can be suppressed.

In particular, strands and / or wires can be sheathed and insulated with the elastic dielectric (in particular to provide cables therefrom), which, due to the compressibility of the elastic dielectric, have a particularly high degree of flexibility and suppleness.

In a further exemplary embodiment, the elastic dielectric is used to produce a capacitor (in particular a capacitor which has acousto-electrical properties). The pores can achieve greater elasticity, which in turn can improve the acoustic radiation output when an alternating voltage is applied.

In a further exemplary embodiment, the elastic dielectric is used to produce an electrically insulating vibration damper. Due to the improved high voltage properties, both the dielectric strength and the long-term stability of the corresponding component can be improved. The inherent pores (gas bubbles) can reduce a change in cross-section in the event of mechanical stress.

In a further exemplary embodiment, the elastic dielectric can be used as an insulator in an electro-mechanical system. In one example, the improved high-voltage properties can reduce the size of such systems.

According to a further exemplary embodiment of the dielectric device, the at least one elastic dielectric is adhered to the two adjacent electrodes (or only to one of the two adjacent electrodes). This has the advantage that the dielectric device can be designed to be particularly robust and at the same time efficient, and that partial discharges can be reduced (or suppressed).

In one example, the dielectric is adhesively bonded to both electrodes. This adhesion is preferably so strong that it is greater than the expansive forces occurring during operation (eg external load in the case of a dielectric sensor or repulsion force in the case of a dielectric actuator). Depending on the area of application, this does not have to be particularly strong. As a result, repulsion effects (which, however, can be very weak) can be possible with actuators due to electrodes that are charged in the same way, as well as a correspondingly extended one Sensor area when using. Furthermore, this adhesion can ensure that there are no large-area (eg larger than 100 to 10,000 square micrometers) air inclusions between the electrode and the dielectric, which could cause partial discharge problems.

According to a further exemplary embodiment of the dielectric device, the maximum change in length of the dielectric device in an operating mode in the height direction (z) is 20% or less (in particular 12% or less, further in particular 8% or less). This has the surprising advantage that the efficiency of the dielectric device can be improved.

Due to the low total volume fraction of the pores, on the one hand the dielectric strength can be ensured, but on the other hand the volume which is available as a displacement space for the activated (or in the operating mode) dielectric device can be limited. It has been shown in one embodiment that the dielectric device experiences a maximum of 20% change in length in the vertical direction, that with length changes of up to 12% the efficiency is particularly desirable and with length changes of up to 8% the efficiency can be essentially optimal.

According to a further exemplary embodiment of the method, the formation of the plurality of pores comprises: i) applying a fluid (in particular CO2) to (essentially) non-hardened (in particular not completely crosslinked) base material at a predetermined pressure, and then ii) lowering the predetermined pressure Pressure during curing (in particular crosslinking) of the base material. This has the advantage that the described pores can be provided particularly efficiently with tried and tested and established methods (in particular homogeneously distributed).

According to a further exemplary embodiment of the method, the formation of the plurality of pores has at least one of the following steps: i) Introducing a propellant into the base material, and subsequently thermal decomposition of the propellant (in particular during a sulfur vulcanization or a Peroxide crosslinking), ii) carrying out a photochemically activated peroxide crosslinking in such a way that oxygen is split off and acts as a pore-forming gas, iii) photochemical initiation of an azo polymerization in such a way that nitrogen is split off and acts as a pore-forming gas, iv) generation of CO2 as a pore-forming gas (in particular using at least one of the following substances: photoacid generator (PAG), photoacid (PAH), carboxylated nitrile rubber, isocyanate), v) thermal decomposition of tetrazoles (in particular formed by means of the nitrile groups of nitrile rubber and azides) in such a way that nitrogen is split off and as pore-forming gas acts. This also has the advantage that the described pores can be provided particularly efficiently using tried and tested and established methods.

According to a further exemplary embodiment, the method comprises: initiating targeted crosslinking in the base material. In particular, where the initiation is at least one from the group consisting of: i) radiation crosslinking, in particular by means of UV radiation, ii)

Electron crosslinking, in particular by means of an electron beam source, iii) thermally initiated radical crosslinking, iv) thermal sulfur crosslinking, v) peroxide-initiated radical crosslinking. In this way, the networking can advantageously be influenced or controlled. This also allows very thin layers (e.g. in the range of approx. 20 to 150 micrometers) to be applied efficiently.

According to a further exemplary embodiment of the method, the base material is a polymer gel. This can have the advantage that an elastic dielectric with particularly advantageous elastic properties can be provided.

Gels can be defined as viscoelastic liquids that have the properties of solids and liquids at the same time. The solids can be crosslinked elastomers that have liquid components embedded in a three-dimensional network. This gives the elastomer network the possibility of a more free spread into the liquid free spaces: For example, balls can dissolve or relax, Twists, spirals, helixes can stretch, etc. so move much more easily overall.

This means that gels of the present type can be particularly suitable for actuator and sensor tasks, since they can combine the easy deformability of liquids with the resilience of elastomers. The listed high boiling points of the liquids (e.g. cyclic carbonates etc.) can be important here, so that the equilibrium does not shift from the gel to the elastomer due to evaporation.

In a particular embodiment, the gels can be provided with thixotopic properties which make gels reversibly “more fluid”, that is to say more easily deformable, by shearing (ie dielectric loading).

The following design variants relate to mechanisms of pore generation and can be freely combined both with one another and with the above mechanisms. The list is exemplary. As shown in the following design variants below, the gases that subsequently fill the cavities are usually formed by chemical reactions. i) Complete, or usually partial, pressure saturation of thermoplastic (uncrosslinked) elastomer with gas (nitrogen, carbon dioxide, noble gases) at 30 to 200 bar pressure and subsequent rapid relaxation to form micropores and immediately subsequent crosslinking (especially photochemical). ii) Thermal decomposition of blowing agents in the course of sulfur vulcanization of unsaturated elastomers at 150 ° to 200 ° C: NR, NBR, EPDM, SBR etc. Such blowing agents (e.g. azodicarbonamide, sulfonic acid hydrazides, nitrosamines, phenyltetrazole etc.) decompose, possibly through "Kicker" activated at temperatures of 120 ° to 200 ° C, ie in the range of vulcanization. The gas yields (eg N2, CO2) can be in the range of 120 to 230 ml / g 8% and 40% amounts of 0.5 to 2 mg propellant / g elastomer to be introduced, primarily in the form of a solution, preferably that solvent, in which the unvulcanized elastomer, including all crosslinking and auxiliary substances, was dissolved or dispersed in order to apply it to a carrier (conveyor belt, mold, carrier layer, but also metal electrode) in the appropriate layer thickness (spraying, lolling, screen printing, pouring ...) · Iii) Saturated elastomers (eg HNBR, including those with oils as extenders) cannot be crosslinked with sulfur, but with peroxide. The procedure here is analogous to embodiment ii), working at lower temperatures (100 ° to 130 ° C.). On the one hand, this requires propellants with a low decomposition temperature (sulfohydrazides), and at the same time enables the use of sodium bicarbonate, which breaks down into CO 2 and H 2 O (in addition to Na 2 CO 3). At working temperatures> 100 ° C, both decomposition products are gaseous and can be used as pore-forming agents, but at least CO2 (1 g NaHCO3 provides up to 260 ml CO2). The amounts used can be very small (less than 2 mg / g elastomer). iv) Peroxide crosslinking (for both saturated and unsaturated elastomers) can also be carried out photochemically. This is achieved with UV light sources (Hg high pressure lamps) or LED blue light sources at moderate temperatures (> 0 ° C). By coordinating peroxides and UV sources (wavelengths), simultaneous crosslinking by means of peroxide A and decomposition of peroxide B with the elimination of oxygen as a gas supplier can be carried out. Benzoyl peroxide (as an example for peroxide B) provides about 90 ml O2 / g. Additions of 1-5 mg / g elastomer should therefore be used. v) Analogously to the photochemical peroxide crosslinking, this can also be possible with azo-polymerization initiators (such as azo-bis (isobutyronitrile) - AIBN). These also break down under the influence of UV into crosslinking radicals and N2, which can be used in situ to form pores, for example 1 g of AIBN provides 130 to 140 ml of N2. By combining different, commercially available azonitriles and related initiators, the crosslinking and decomposition temperature for N2 production can be set in a wide range (50 to 150 ° C). vi) Combination of iv) and v) for optional crosslinking by means of peroxide and / or azonitrile or gas extraction by means of peroxide and / or azonitrile. If necessary also in a multiphase irradiation by means of different wavelengths or different temperatures. vii) Variation of the exemplary embodiments iv), v) and vi) such that peroxides and / or azonitriles are only used for gas extraction, while the crosslinking takes place with other, non-gas-forming photoinitiators. Such (eg alkylhydroxybenzophenones, polythiols etc.) allow extensive adaptation to the type of elastomer and crosslinking conditions. viii) Photoacid generators (PAGs) and photoacids (PAHs) form so-called Brönsted or Lewis acids under the influence of UV. These reaction products are usually used for the cationic polymerization / curing of epoxides and vinyl ethers, but are generally not suitable for crosslinking elastomers. According to the invention, however, these acids can be used in combination with finely divided carbonates of the alkali and alkaline earth metals and ammonium bases to generate CO ₂ . The UV radiation that is required for this reaction can, however, also be used at the same time for crosslinking and / or additional pore formation according to exemplary embodiments iv), v), vi), and vii). ix) Another _{variant generates CO 2} from the combination of elastomers with (eg carboxylated nitrile rubber such as XNBR or HXNBR in its hydrogenated form) as an acidic component: using the carboxyl function, CO _{2 is} generated from finely divided carbonates. Crosslinking by means of photoreactions iv) - viii). x) In a further embodiment, CO ₂ can be generated by reaction of isocyanates (R-NCO) with water to form urea derivatives (2 RNCO + H ₂ O - RNH-CO-NH-R + CC). In order to avoid the disadvantageous introduction of water into an elastomer-isocyanate mixture, it is proposed to generate the required water in situ by reacting acid with base. The acid part according to embodiment viii) is generated from PAG by a photoreaction. The base portion is preferred to quaternary Ammonium bases, preferably tetrabutylammonium hydroxide, provided. The particular advantage can lie in the solubility of this base in organic solvents and in a function of this compound which catalyzes the reaction of isocyanate with water. xi) Another embodiment is based on the thermal decomposition potential of tetrazoles (formation of N2). These can be formed by the (partial) reaction of nitrile groups from NBR rubbers (the dielectric) with azides. The crosslinking takes place, for example, thermally or photocatalytically. xii) Another embodiment uses non-crosslinked elastomers as dielectric, but polymer gels, preferably made of PVDF, HFP, etc., in organic carbonates such as propylene carbonate and uses photo reactions according to examples iv) to viii) or isocyanate reaction for gas or pore formation in the course the gelation process.

According to an exemplary embodiment, an elastic dielectric is described which has an elastic polymer with a plurality of pores, the pores being discrete gas-filled cavities, the totality of the pores in the elastic polymer having an average pore diameter of 50 μm or less, and where the totality of the pores in the elastic polymer has a total pore volume which makes up 60% (in particular 40%) or less of the total volume of the elastic dielectric.

In the following, exemplary embodiments of the present invention are described in detail with reference to the following figures.

Figures la, lb, and lc each show a dielectric device according to an embodiment of the invention.

Figure ld shows a dielectric device as a stack actuator / sensor according to an embodiment of the invention.

FIG. 2 shows an elastic dielectric, which has a plurality of pores, according to an exemplary embodiment of the invention. Before the figures are described in detail, some exemplary embodiments are discussed again below to illustrate the concept of the invention.

According to an exemplary embodiment, on the one hand, a corresponding space is to be created for the compressed or expanded elastic dielectric, so that these movements are possible without significant lateral changes in volume in the x or y direction. On the other hand, the problem of electric fields caused by gas bubbles should be minimized. For small pores, the field disturbance (or field distortion) can be smaller (more than just linearly smaller) than for larger pores. Based on the existing calculation models, it can be said that the changes in capacity due to the pores are associated with the square of the radius of a pore. This allows a suitable partial discharge to be determined for each area of application by choosing the average (or maximum) pore diameter. A partial discharge is not desirable, but surprisingly it has been shown that no nano-scale pores are required to design a partial discharge behavior, but that even micro-scale pores alleviate the problem of partial discharges in such a way that it can be used as a dielectric device (e.g. DEA) is efficiently enabled.

According to an exemplary embodiment, with a pore diameter of less than 100 micrometers, the partial discharge use increases to over 15 kV / mm. This means that in the further reduction in size of the pores (e.g. 20 instead of 100 micrometers, i.e. 1/5 of the radius, thus 1/25 of the problem, so that the partial discharge starting area theoretically shifts above the breakdown value of the actual base material of the dielectric) can "calculate out" the partial discharge problem by itself. This may not increase the breakdown voltage compared to the value without pores, because every insertion of micro- or nanopores can disrupt the field (and thus reduce the breakdown voltage and increase the Partial discharge tendency), but the disturbing influence of the pores with respect to the field can be negligible. According to an exemplary embodiment, the modulus of elasticity of the polymer can be reduced by inserting pores into an elastic polymer base material. This makes the base material more elastic. In this case, the described pores can act as “thinners”, which is shown in an increase in the deflection (or in the actuator path (with a reduction in the actuator force)) of a dielectric device.

According to an exemplary embodiment, a special feature is a low degree of expansion in the pore formation. As a rule, known methods are aimed at generating foams for insulating and damping purposes, that is to say at a particularly low foam weight. In the present case, however, it is not a matter of “foam” (pores from one another, usually only separated by cell membranes, mostly even connected to one another), but an elastic material with discrete (not coagulated) pores and thus completely different relevant mechanical and electrical ones Characteristics.

According to an exemplary embodiment, the term "pores" is understood to mean discrete, gas-filled cavities within an elastomer matrix. Discrete because, if possible, contact between individual pores must / should be avoided This would be in complete contrast to the desired partial discharge field strength and limit this. In terms of a desired minimum layer thickness of the elastic dielectric of <50 μm, in particular 20 μm, the cavities should not exceed 40% of the Total dielectric volume, preferably <25%, even more preferably <12%, resulting in a preferred cavity diameter of <5 μm.

In the following, an example calculation, idealized for size estimation, is shown according to an exemplary embodiment: A dielectric with a thickness of 50 μm (h) contains approximately (assuming that the pore diameter roughly corresponds to the pore spacing) the following number of pores in order to ensure a discrete pore distribution:

The gases that fill the cavities are usually formed by chemical reactions. Accordingly, the Avogadro rule applies, according to which 1 mol of a gas corresponds to a volume of 22.4 l or 1 mmol to 22.4 ml and 1 pmol to 22.4 pl.

As a model, the CC formation by acidification of CaCCb is used to estimate the relevant production parameters:

CaCC> 3: molecular weight 100.1; s = 2.71; gives 22.4 I CC / mol,

1 cube with a side length of 1 cm weighs 2.71 g,

1 ball of 1 cm 0 weighs 1.41 g,

100.1 g CaC03 result in 22.4 l gas (CO2),

100.1 mg CaCO3 yield 22.4 ml gas,

2.71 mg (cube 1 mm s) gives 0.61 ml gas = 610 mm ² = pore with 8.5 mm 0, 1.41 mg (sphere 1 mm 0) gives 0.32 ml gas = 320 mm ³ = Pore with 6.9 mm 0.

A pore (or gas bubble) about 7 times as large is created from spherical CaCCb. In addition, cubic CaCCb creates a pore about 8.5 times as large.

Solids (such as CaCOs) can be produced by mechanical comminution (impact mill) or precipitation with a minimum fineness of 30 nm to 80 nm particle size, ie, according to the above approximation, pore diameters of about> 250 to 700 nm can be realized. What is important, however, is the need for a corresponding distribution within the overall formulation, in particular because nano-fine particles are usually found merge to form larger agglomerates. This can be achieved by applying appropriate shear forces, for example with the help of ultrasound.

Further possibilities for pore formation are based on reactions that start from dissolved reagents, thus enabling an even finer pore structure. In order to achieve a total pore volume proportion of 8 to 40%, the following amounts of cubic CaC0 ₃ ultra-fine powder would be necessary (based on the example):

8% 0.08 ml gas corresponds to 0.3 - 0.4 mg / g elastomer,

40% 0.40 ml gas corresponds to 1.5 - 2.0 mg / g elastomer.

With these quantities, no changes in the other chemical, physical or mechanical properties of the elastomer are to be expected, apart from the change in elasticity produced by the pores.

Identical or similar components in different figures are provided with the same reference numbers.

FIG. 1 a shows a dielectric device 100 which can be used as a dielectric actuator (DEA), a dielectric sensor (DES) or a mixed form (DEAS). The device 100 has a first electrode 110 and a second electrode 120, the second electrode 120 being arranged opposite the first electrode 110. Furthermore, the device 100 has an elastic dielectric 130 which is arranged between the first electrode 110 and the second electrode 120. The electrodes 110, 120 each have a contact area 114 which consists of electrically conductive material and via which the electrodes 110, 120 can be contacted, or via which a voltage U can be applied. The second electrode 120 here represents the counter electrode to the first electrode 110. Each of the two electrodes 110, 120 is electrically contacted separately, so that an electrical field can be generated by means of the electrodes 110, 120. In the example shown, no voltage is applied (0 volts), so that the dielectric device 100 is not in an operating mode.

Each of the two electrodes 110, 120 has a functional area 112, which has an electrically conductive metal. The functional area 112 is Plate-shaped and thus extends along two main directions of extent x, y, the functional area 112 spanning an area plane E. In the example shown, the functional area 112 makes up the entire electrode plate 110. In other exemplary embodiments, the electrode 110 has an (insulating) carrier material, on which the functional region 112 is then arranged (for example vapor-deposited).

FIG. Lb shows the dielectric device 100 according to FIG. La, the electrodes 110, 120 being electrically contacted at the respective contact areas 114. In the example shown, a voltage of 1 kV is applied to the electrodes 110, 120, so that the dielectric device 100 is in an operating mode. The first electrode 110 now forms a positive pole and the second electrode 120 (counter electrode) forms the negative pole.

This electrical contact leads to the positively charged first electrode 110 and the negatively charged second electrode 120 attracting one another and moving spatially towards one another. If the dielectric 130, which is arranged between the first electrode 110 and the second electrode 120, is designed as an elastic dielectric (e.g. as an elastomer), it is partially pressed out to the sides of the dielectric device 100 due to its incompressibility.

FIG. 1c shows the basic functional principle of the dielectric device 100 (as already described above for FIGS. 1a and 1b) as a dielectric actuator or sensor. If a voltage U is applied to the electrodes 110, 120, the electrode plates move towards one another. This in turn generates a pressure P on the dielectric 130, which is arranged between the electrodes 110, 120. If the dielectric 130 is designed as an elastomer, it is essentially incompressible and is forced to expand by the pressure from above (z +) and from below (z-). The area expansion (see the movement arrows pointing outwards) takes place along the two main directions of extension x, y of the electrodes 110, 120.

Figure ld shows a plurality of dielectric devices 100 according to Figures la to lc, which are in the form of a stack actuator (or stack sensor) or a stacking system are arranged. Here, the individual dielectric devices 100 are stacked one on top of the other in the height direction (z) to form a dielectric device 100 composed of multiple units. A third electrode 121, which is arranged opposite the second electrode 120, is now arranged below the first electrode 110 and the second electrode 120 (between which the first dielectric 130 is arranged).

Correspondingly, a second elastic dielectric 131 is arranged between the third electrode 121 and the second electrode 120. This arrangement can be continued by means of a fourth electrode and a third dielectric, etc. The first electrode 110 and the third electrode 121 are connected in an electrically conductive manner at their contact areas 114 via a bonding wire. The second electrode 120 (and then the fourth electrode, etc.) in this case represent the counter electrodes 160, the counter electrodes 160 again being connected to one another in an electrically conductive manner (e.g. by means of bonding wires) at their contact areas 114. In further embodiments, several such stacks can also be arranged next to one another and used jointly.

FIG. 2 shows an elastic dielectric 130 (or an electrical insulator) which has an elastic polymer 190. A plurality of pores 180 are formed in the polymer 190. The pores 180 are here filled with air, the air essentially not being able to escape from the pores 180. The elastic dielectric 130 is designed essentially as an integral foam and thus has a closed (air-impermeable) outer layer 191.

Each pore 180 has a pore diameter d. The pores are very small and the pore diameters d are in the micro-scale range. An average pore diameter of the plurality of pores 180 can be calculated from the plurality of pore diameters d. This mean pore diameter is 50 μm or less.

Furthermore, the pores 180 only take up a (small) part of the dielectric 130 (or the elastic polymer 190). Each pore 180 has a pore volume and a total pore volume can be calculated from the majority of the pore volumes of the pores 180 (for example by addition). This Total pore volume is 60% or less (in particular 8% or less) of the total volume of the elastic dielectric 130 (or the total volume of the elastic polymer 190).

In the elastic dielectric 130, the pores 180 are distributed essentially homogeneously, so that less than 10% (in particular less than 0.1%) of the pores 180 coagulate. The pores 180 are separated from one another by a respective pore spacing r. Using the plurality of pores 180, an average pore spacing can be calculated from the individual pore spacings r. This mean pore spacing is greater than half the mean diameter of the plurality of pores (or greater than the mean diameter of the plurality of pores) for at least 50% (in particular at least 97%) of the pores.

The elastic dielectric 130 has a particularly high dielectric strength of 5 kV / mm or more (in particular of 16 kV / mm or more). The elastic dielectric 130 is preferably designed to be very thin with a thickness of 100 μm or less. With this particularly small thickness, the elastic dielectric 130 has a dielectric strength of 15 n / mhh or more (in particular 48 V / pm or more).

Furthermore, the elastic dielectric 130 is formed along the two main directions of extent x and y, which span a plane. The elastic dielectric 130 is set up in an operating mode to carry out a change in length (or deflection) in a height direction z, which is oriented perpendicular to the main extension directions x, y.

In addition, it should be pointed out that “having” does not exclude any other elements or steps and “a” or “a” does not exclude a plurality. Furthermore, it should be pointed out that features or steps that have been described with reference to one of the above exemplary embodiments also can be used in combination with other features or steps of other exemplary embodiments described above. Reference symbols in the claims are not to be regarded as a restriction. Bezuaszeichen

100 Dielectric Device

110 First electrode, metal foil

112 Functional (electrically conductive) area

114 Contact Area

120 Second electrode

121 Third electrode

130 (first) dielectric

131 Second dielectric

150 structuring

160 counter electrode

180 pore

190 elastic polymer / base material

191 Outer layer d pore diameter

E area level

P pressure r pore spacing

U voltage

X, Y main directions of extent z height direction

Claims

Expectations

1. An elastic dielectric (130) which has an elastic polymer (190) and a plurality of pores (180), the plurality of pores (180) having an average pore diameter (d) of 50 μm or less, and wherein the Plurality of pores (180) has a total pore volume which makes up 60% or less of the total volume of the elastic dielectric (130).

2. The elastic dielectric (130) according to claim 1, wherein the pores (180) are fluid-filled, in particular air-filled.

3. The elastic dielectric (130) according to claim 1 or 2, wherein the plurality of pores (180) has an average pore diameter (d) of 20 μm or less, in particular 10 μm or less, more particularly 1 μm or less.

4. The elastic dielectric (130) according to any one of the preceding claims, wherein the total pore volume is 40% or less, in particular 25% or less, further in particular 12% or less, further in particular 8% or less, of the total volume of the elastic dielectric (130) ) matters.

5. The elastic dielectric (130) according to any one of the preceding claims, wherein the pores (180) are distributed substantially homogeneously in the elastic dielectric (130).

6. The elastic dielectric (130) according to claim 5, wherein the mean distance (r) between at least 50%, in particular at least 90%, further in particular 97%, of the pores (180) of the plurality of pores (180) is greater than that Is half the mean diameter (d) of the plurality of pores (180) or greater than the mean diameter (d) of the plurality of pores (180); and or wherein the pores (180) are distributed in the elastic dielectric (130) in such a way that 10% or less, in particular 1% or less, further in particular 0.1% or less, of the pores (180) coagulate.

7. The elastic dielectric (130) according to any one of the preceding claims, wherein the elastic polymer (190) comprises at least one from the group consisting of: a diene polymer, in particular at least one of butadiene, isoprene, dimethylbutadiene, halobutadiene, Cyclopentadiene, cyclooctadiene; an elastomer with a 1,2 and / or 1,4 linkage in cis and / or trans form; a copolymer with monounsaturated monomers, in particular one of styrene, ethene, propene, butene, acrylonitrile, acrylic acid, acrylic acid esters, vinyl ethers, vinyl esters, vinyl halides; a thermoplastic elastomer, in particular a crosslinked thermoplastic elastomer, a polyaddition elastomer, in particular polyurethane or a silicone elastomer; an elastomer which was subsequently crosslinked, in particular by means of one from the group consisting of sulfur, peroxide, UV radiation, photoinitiators; a polymer mixture of at least two of the above-mentioned elastomers.

8. The elastic dielectric (130) according to any one of the preceding claims, wherein the elastic dielectric (130) has a dielectric strength of 5 kV / mm or more, in particular of 12 kV / mm or more, further in particular of 16 kV / mm or more , having.

9. The elastic dielectric (130) according to any one of the preceding claims, wherein the elastic dielectric (130) has a thickness of 100 µm or less; and wherein the elastic dielectric has a dielectric strength of 15 V / pm or more, in particular 36 V / pm or more, further in particular 48 V / pm or more.

10. The elastic dielectric (130) according to any one of the preceding claims, wherein the elastic dielectric (130) has at least one of the following additives: a capacity-increasing additive, in particular a ferroelectric dielectric additive which crystallizes in the perovskite type, further in particular a titanate; a fluoropolymer, especially polytetrafluoroethylene, PTFE.

11. The elastic dielectric (130) according to any one of the preceding claims, wherein the elastic dielectric (130) is designed essentially as an integral foam, in particular wherein the elastic dielectric (130) has a substantially closed outer layer (191).

12. The elastic dielectric (130) according to any one of the preceding claims, wherein the elastic dielectric (130) is formed along two main directions of extent (x, y) which span a plane, and wherein the elastic dielectric (130) is arranged in one Operating mode to carry out a change in length in a height direction (z) which is oriented perpendicular to the main extension directions (x, y).

13. The elastic dielectric (130) according to any one of the preceding claims, wherein the elastic dielectric (130) is set up in an operating mode in at least one spatial direction a change in length of 1% or more, in particular 3% or more, further in particular 5% or more, to carry out, in particular wherein the elastic dielectric (130) is set up to carry out a plurality of the changes in length.

14. Use of an elastic dielectric (130) according to any one of the preceding claims 1 to 13 in at least one of the group consisting of: a dielectric device, in particular a dielectric sensor and / or a dielectric actuator, a cable, a capacitor, a vibration damper, an electromechanical system.

15. A dielectric device (100), in particular a dielectric actuator and / or a dielectric sensor, which has: a plurality of electrodes (110, 120, 121), each of which has: a functional area (112) which extends along two main directions of extent (x, y) is formed and spans a first plane; and a plurality of elastic dielectrics (130, 131), each dielectric (130, 131) being formed along the two main directions of extension (x, y) and spanning a second plane; wherein the electrodes (110, 120, 121) and the elastic dielectrics (130, 131) are arranged alternately; and wherein at least one dielectric of the plurality of elastic dielectrics (130, 131) is an elastic dielectric (130) according to any one of claims 1 to 13.

16. The dielectric device (100) according to claim 15, wherein the at least one elastic dielectric (130) is adhesively attached to the two adjacent electrodes (110, 120).

17. The dielectric device (100) according to claim 15 or 16, wherein the maximum change in length of the dielectric device (100) in an operating mode in the height direction (z) is 20% or less, in particular 12% or less, further in particular 8% or less , is.

18. A method for producing an elastic dielectric (130), in particular for a dielectric device, further in particular a dielectric actuator and / or sensor, the method comprising: Providing an, in particular elastic, polymer as the base material

(190);

Forming a plurality of pores (180) in the base material (190) such that the plurality of pores (180) has an average pore diameter (d) of 50 μm or less, and the total pore volume of the plurality of pores (180) is 60% or less less of the total volume of the elastic dielectric (130).

19. The method of claim 18, wherein forming the plurality of pores (180) comprises:

Applying a fluid, in particular CO2, at a predetermined pressure to essentially uncured, in particular not completely crosslinked, base material (190); and then

Lowering the predetermined pressure during curing, in particular crosslinking, of the base material (190).

20. The method of claim 18 or 19, wherein forming the plurality of pores (180) comprises at least one of the following steps:

Introducing a propellant into the base material (190), and subsequently thermal decomposition of the propellant, in particular during sulfur vulcanization or peroxide crosslinking;

Carrying out a photochemically activated peroxide crosslinking in such a way that oxygen is split off and acts as a pore-forming gas; photochemical initiation of an azo polymerization in such a way that nitrogen is split off and acts as a pore-forming gas;

Generating CO2 as a pore-forming gas, in particular using at least one of the following substances: Photoacid generator, PAG, Photoacid, PAH, carboxylated nitrile rubber, isocyanate. thermal decomposition of tetrazoles, in particular formed by means of the nitrile groups of nitrile rubber and azides, in such a way that nitrogen is split off and acts as a pore-forming gas.

21. The method of any one of claims 18 to 20, wherein the method comprises:

Initiation of a targeted crosslinking in the base material (190), in particular wherein the initiation is at least one from the group consisting of:

Radiation crosslinking, in particular by means of UV radiation; Electron crosslinking, in particular by means of an electron beam source; thermally initiated radical crosslinking; thermal sulfur crosslinking;

Cross-link peroxide-initiated radical.

22. The method of any one of claims 18 to 21, wherein the base material (190) is a polymer gel.

23. Using an electrical insulator which has an elastic polymer (190) which has a plurality of gas bubbles (180) whose mean pore diameter (d) is 20 μm or less and whose total pore volume is 40% or less of the total volume of the electrical insulator , as a dielectric (130) in a dielectric actuator and / or dielectric sensor (100).