Classifications

• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M4/00—Electrodes
  • H01M4/02—Electrodes composed of, or comprising, active material
  • H01M4/04—Processes of manufacture in general
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M4/00—Electrodes
  • H01M4/02—Electrodes composed of, or comprising, active material
  • H01M4/64—Carriers or collectors
  • H01M4/66—Selection of materials
  • H01M4/663—Selection of materials containing carbon or carbonaceous materials as conductive part, e.g. graphite, carbon fibres
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01G—CAPACITORS; CAPACITORS, RECTIFIERS, DETECTORS, SWITCHING DEVICES, LIGHT-SENSITIVE OR TEMPERATURE-SENSITIVE DEVICES OF THE ELECTROLYTIC TYPE
  • H01G11/00—Hybrid capacitors, i.e. capacitors having different positive and negative electrodes; Electric double-layer [EDL] capacitors; Processes for the manufacture thereof or of parts thereof
  • H01G11/22—Electrodes
  • H01G11/30—Electrodes characterised by their material
  • H01G11/32—Carbon-based
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M4/00—Electrodes
  • H01M4/02—Electrodes composed of, or comprising, active material
  • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M4/00—Electrodes
  • H01M4/02—Electrodes composed of, or comprising, active material
  • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
  • H01M4/139—Processes of manufacture
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M4/00—Electrodes
  • H01M4/02—Electrodes composed of, or comprising, active material
  • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M4/00—Electrodes
  • H01M4/02—Electrodes composed of, or comprising, active material
  • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
  • H01M4/621—Binders
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M4/00—Electrodes
  • H01M4/02—Electrodes composed of, or comprising, active material
  • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
  • H01M4/621—Binders
  • H01M4/622—Binders being polymers
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M4/00—Electrodes
  • H01M4/02—Electrodes composed of, or comprising, active material
  • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
  • H01M4/624—Electric conductive fillers
  • H01M4/625—Carbon or graphite
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M4/00—Electrodes
  • H01M4/02—Electrodes composed of, or comprising, active material
  • H01M4/64—Carriers or collectors
• • H—ELECTRICITY
  • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
  • H10N—ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
  • H10N30/00—Piezoelectric or electrostrictive devices
  • H10N30/01—Manufacture or treatment
  • H10N30/06—Forming electrodes or interconnections, e.g. leads or terminals
• • H—ELECTRICITY
  • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
  • H10N—ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
  • H10N30/00—Piezoelectric or electrostrictive devices
  • H10N30/80—Constructional details
  • H10N30/87—Electrodes or interconnections, e.g. leads or terminals
  • H10N30/877—Conductive materials
  • H10N30/878—Conductive materials the principal material being non-metallic, e.g. oxide or carbon based
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
  • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
  • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
  • Y02E60/10—Energy storage using batteries
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
  • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
  • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
  • Y02E60/13—Energy storage using capacitors
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
  • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
  • Y10T428/00—Stock material or miscellaneous articles
  • Y10T428/31504—Composite [nonstructural laminate]
  • Y10T428/31678—Of metal

Definitions

• the present invention relates to a method of making stretchable electrodes.
• electrically conductive carbon particles are introduced into a surface layer comprising an elastomer. These carbon particles may in particular be carbon nanotubes.
• the invention relates to an expandable electrode obtainable according to the invention and the use of such an electrode.
• Carbon nanotubes are known for their exceptional properties. For example, their strength is about 100 times that of steel, whose thermal conductivity is about twice that of diamond, their thermal stability reaches up to 2800 0 C in vacuum and their electrical conductivity can be many times the conductivity of copper , However, these structural characteristics are only accessible at the molecular level if it is possible to homogeneously distribute carbon nanotubes and to produce the largest possible contact between the tubes and the medium, ie to make them compatible with the medium and thus stable dispersible. With regard to electrical conductivity, it is furthermore necessary to form an optionally homogeneous network of tubes in which, ideally, they only touch at the ends.
• the carbon nanotubes should be as isolated as possible, that is agglomerate-free, not aligned and present in a concentration at which such a network can just form, which is reflected by the sudden increase in electrical conductivity as a function of the concentration of carbon nanotubes (percolation limit) ,
• Electrically conductive materials that do not or only slightly change their conductive properties under mechanical stress are for applications such as the term "smart apparel", flexible display elements, stretchable electrical circuits, implants, prostheses, microelectromechanical systems (MEMS) and dielectric Elastomer actuators can be used.
• the mechanical strains acting in such applications can range from less than 5% to over 200%.
• carbon nanotubes in the form of bundles and / or agglomerates find an energetic minimum in their mutual arrangement, their compatibility with the surrounding medium must be increased.
• a chemical, covalent functionalization of carbon nanotubes can actually improve their compatibility with the polymer medium. This manifests itself for example in an increased (thermal) long-term stability and the absence of reagglomeration.
• this surface modification also breaks the delocalized ⁇ -electron system of the tube and thus lowers the electrical conductivity of each individual tube as a function of the degree of functionalization.
• the non-covalent functionalization of carbon nanotubes by, for example, dispersing additives provides an alternative to chemical, covalent modification and compatibilization of the tube with the medium.
• this approach can be used for any new medium, whether elastomeric raw material or formulation requires new optimization with regard to the chemistry and the concentration of the respective dispersing additive and can never represent a universal solution.
• any processing of fillers including carbon nanotubes
• a new property such as electrical conductivity
• mechanical properties can be impaired by such agglomerates.
• carbon nanotubes would have to be homogeneously distributed over the entire volume of the material so that the percolation limit is exceeded and at the same time no residual agglomerates are present. This procedure very often fails already due to the dramatic increases in viscosity, which are due to the carbon nanotubes concentrations required for exceeding the percolation limit. Furthermore, the reagglomeration of homogeneously dispersed carbon nanotubes during elastomer processing with this method can not be excluded and easily prevented.
• WO 2008/150867 A2 discloses a method for embedding particles in a substrate.
• a fluid is applied to at least a portion of the substrate comprising a population of particles having at least one characteristic dimension in the range of about 0.1 nm to about 1 cm.
• the application is done in such a way that the substrate softens to a degree that a plurality of particles are at least partially embedded in the softened area of the substrate.
• at least a part of the substrate is hardened so that at least one particle is securely embedded in the substrate. It is stated that the application of heat can help embed particles.
• the embedding of carbon particles such as carbon nanotubes in elastomers is not described concretely.
• the examples in this patent application deal with embedding silver nanoparticles in polyvinyl chloride.
• the invention therefore proposes a process for the production of expandable electrodes with a surface layer comprising electrically conductive carbon particles, comprising the steps:
• Electrically conductive particles in the meaning of the present invention are initially all particles of a material which is not an insulator.
• insulators are substances having an electrical conductivity of less than 10 -8 S / m.
• the particles are introduced into a surface layer comprising an elastomer, which means that it is not only the surface itself that is occupied by the particles, but also the material immediately below the surface that absorbs the particles.
• the term surface layer as opposed to the two-dimensional surface, means a three-dimensional layer of material which includes the surface as one of its boundaries. The surface layer is delimited to the interior of the object in question at least by containing just these electrically conductive particles.
• an elastomer is provided.
• Elastomers in the context of the present invention are dimensionally stable, but elastically deformable plastics. It is envisaged that the elastomer has a glass transition temperature T g of> -130 0 C to ⁇ 0 0 C.
• the glass transition temperature can be determined according to the standard DIN EN ISO 6721-1 and can also be in a range from> -80 0 C to ⁇ -10 0 C or from -78 0 C to ⁇ -30 0 C.
• the stress ⁇ does not decrease with increasing elongation. This is to be understood as the behavior of the stress ⁇ at the intended operating temperature of the electrode.
• the curve for the stress ⁇ has no local maximum.
• the elastomers do not show a yield point in the stress-strain curve.
• Particularly suitable elastomers have a progressively increasing stress ⁇ with increasing elongation, without showing a yield point in the stress-strain curve.
• the stress ⁇ does not decrease with increasing elongation.
• Suitable elastomers may include, but are not limited to, a Shore A hardness according to ISO 868 of> 20 to ⁇ 100.
• the plastics may deform elastically under tensile and compressive loading and have tensile strengths in accordance with DIN 53 504 in the range of> 10 kPa to ⁇ 60 MPa. After the stress they find their way back to their original, undeformed shape.
• Good elastomers show only low permanent elongation and no noticeable creep under continuous mechanical load.
• the creep according to DIN EN 10 291 is ⁇ 20% and more preferably ⁇ 5%.
• Step (B) involves providing a preparation of non-aggregated carbon particles.
• a stable preparation in this case occurs in a storage at room temperature for a period of at least one day, preferably a week or four weeks, no flocculation or precipitation of the carbon particles.
• the existing aggregates of the carbon particles can be broken by energy input, for example by means of ultrasound, grinding processes or high shear forces.
• the solvent is selected after that it can both form the preparation of the carbon particles and swell the elastomer surface.
• the average particle diameter may also be in a range from> 1 nm to ⁇ 1000 nm or from> 3 nm to ⁇ 100 nm.
• the determination can be made for example by means of scanning electron microscopy or dynamic light scattering.
• the solvent may be an aqueous or a nonaqueous solvent. In the latter case, it is preferably a polar, aprotic solvent. In this way, the solvent can interact well with soft segment domains in the elastomer.
• nonaqueous means that no additional water has been added to the solvent, but excludes the technically unavoidable traces of water, for example up to an amount of ⁇ 5% by weight, preferably ⁇ 3% by weight and more preferably ⁇ 1% by weight. %, not from.
• the carbon particles may be deagglomerated and dispersed by the addition of surfactants or other surfactants.
• the carbon particles may be present in the solvent in a concentration of, for example, from> 0.01% by weight to ⁇ 20% by weight,> 0.1% by weight to ⁇ 15% by weight or> 0.04% by weight to ⁇ 5% by weight -% exist.
• step (C) The contacting of the surface layer comprising an elastomer with the preparation of the carbon particles in step (C) naturally takes place via the surface of the elastomer.
• the preparation of the carbon particles acts on the surface layer.
• the solvent swells the surface of the elastomer, forms pores in the surface layer, and allows carbon particles to migrate into these pores.
• swelling of the elastomer is favored when hydrophilic domains are present in the polymer.
• the particles may penetrate the surface layer to a depth of ⁇ 10 ⁇ m, ⁇ 1 ⁇ m or ⁇ 0.3 ⁇ m. The exposure time is chosen so that the elastomer of the surface layer is not converted into solution.
• step (E) involves stopping the exposure of the preparation of the carbon particles to the surface layer.
• the preparation of the carbon particles is separated from the surface layer again.
• the surface layer can be rinsed to remove adherent preparation. This can be done inter alia by removing the elastomeric article with the surface layer to be modified from a dipping bath. Thereafter, the article can be rinsed with acetone, for example.
• step (E) is followed by a drying step in which the solvent in the swollen surface layer is removed, closing the pores in the elastomer and entrapping the carbon particles in the polymer.
• the method according to the invention offers the possibility of selectively providing the surface layer of an elastomeric article with an electrically conductive surface for the production of an expandable electrode. Because the elastomer functionalized in the process is selected according to the invention, the electrode is also suitable for cyclic loading. In the process, the shape of the article is not destroyed by dissolution, so that even finished moldings can be treated. Since the particles are concentrated in the near-surface area of the article, an overall smaller amount is needed to obtain an electrically conductive elastomer surface. Finally, unlike solution-based processes, no large amounts of solvents need to be removed to obtain the final modified polymer. It is also possible to keep the concentration of the carbon particles in a range in which no technically disadvantageous increase in viscosity occurs.
• a further advantageous aspect of the method according to the invention for producing expandable electrodes is the treatment of elastomer moldings which are subsequently to be painted by an electrostatic powder coating or which are to be galvanized.
• the electrically conductive particles in the surface layer provide for an improved electrostatic powder application.
• Another application relates to the treatment of elastomeric moldings for the preparation of an electrodeposition coating. It is also possible to obtain conductive electrode materials or elastic capacitors.
• electronic components or cable sheathing can be provided with an antistatic coating. In one embodiment of the method according to the invention, this further comprises the step:
• step (F) applying an additional electroconductive layer to the surface layer comprising the electrically conductive carbon particles obtained in steps (B) to (E), wherein the obtained additional electroconductive layer ruptures or tears when the surface layer is stretched therebefore.
• the additional electrically conductive layer in step (F) may be, for example, a conductive paint, a conductive paste, a metal layer or a layer of an electrically conductive polymer.
• metals are gold, silver, copper and / or tin.
• electrically conductive polymers are polythiophenes, in particular the poly (3,4-ethylenedioxythiophene) commonly referred to as PEDOT or PEDT.
• the application of the metals can be done, for example, by chemical vapor deposition, physical vapor deposition or sputtering. Preference is given to the sputtering of gold.
• the application of the electrically conductive polymers can be carried out by means of a polymer solution, followed by evaporation of the solvent.
• Other possible materials for the additional layer are indium tin oxide (ITO), fluorine doped tin (IV) oxide (FTO), aluminum doped zinc oxide (AZO) and / or antimony doped stannic oxide (ATO).
• the additional electrical layer may include, but is not limited to, a thickness of> 10 nm to ⁇ 10 ⁇ m or from> 20 nm to ⁇ 1 ⁇ m.
• the material of the additional electrically conductive layer is selected so that the additional layer first breaks or tears when the surface layer is stretched.
• the advantage of this is that the electrical conductivity of the overall system does not abruptly collapse due to the contact of the broken or cracked coating with the surface layer comprising carbon particles, but is still maintained to a certain extent.
• the power density of a stretchable electrode decreases with time due to the stress, but does not completely extinguish. This behavior is particularly favorable when the elastomer is subjected to cyclic stretching and unloading and is promoted throughout the period via an electrical conductivity.
• step (D) the action of the preparation of the carbon particles on the surface layer of the elastomer takes place using ultrasound and / or heat instead.
• the energy input by ultrasound and / or heat counteracts the formation of particle aggregates and thus enables higher particle concentrations in the solution.
• the introduction of the particles into the elastomer surface layer is accelerated.
• the frequency is advantageously> 20 kHz to ⁇ 20 MHz and, independently of this, the power density in the solvent is> 1 W / l to ⁇ 200 W / l.
• the temperature may be, for example,> 30 ° C. to ⁇ 200 ° C., preferably> 40 ° C. to ⁇ 150 ° C.
• the carbon particles used are not further covalently functionalized on the surface following their preparation. This "means that the particles carry no additional covalently linked via further reaction steps functional groups on its surface.
• oxidizing agents such as nitric acid, hydrogen peroxide, potassium permanganate and sulfuric acid or a possible mixture of these agents for the functionalization of the carbon particles.
• non-covalently functionalized particles means that the ⁇ -electron system of the surface is not disturbed and therefore can contribute fully to the electrical conductivity.
• the carbon particles are selected from the group comprising carbon nanotubes, single-walled carbon nanotubes, multi-walled carbon nanotubes, carbon nanohorns, carbon nano-onions, fullerenes, graphite, graphene, carbon fibers, carbon black and / or carbon black.
• these particles can also improve mechanical properties of the surface layer, such as elasticity and impact strength.
• Carbon nanotubes according to the invention are all single-walled or multi-walled carbon nanotubes of the cylinder-type, scroll-type, multiscroll-type or onion-like structure. Preference is given to using multi-walled carbon nanotubes of the cylinder type, scroll type, multiscroll type or mixtures thereof. It is favorable if the carbon nanotubes have a ratio of length to outer diameter of> 5, preferably> 100.
• the individual graphene or graphite layers in these carbon nanotubes seen in cross-section, evidently run continuously from the center of the carbon nanotubes to the outer edge without interruption. For example, this may allow for improved and faster intercalation of other materials in the tube framework as more open edges than the entry zone of the
• the carbon particles are non-covalently functionalized, multi-walled carbon nanotubes with a diameter of> 3 nm to ⁇ 100 nm.
• the diameter here refers to the mean diameter of the nanotubes. It can also be in a range from> 5 nm to ⁇ 80 nm and advantageously from> 6 nm to ⁇ 60 nm.
• the length of the nanotubes is initially not limited. However, it may, for example, be in a range of> 1 ⁇ m to ⁇ 100 ⁇ m and advantageously of> 10 ⁇ m to ⁇ 30 ⁇ m.
• the solvent is selected from the group comprising methanol, ethanol, isopropanol, butanol, ethylene glycol, propylene glycol, butylene glycol, glycerol, hydroquinone, acetone, ethyl acetate, trichlorethylene, trichloroethane, trichloromethane, methylene chloride, cyclohexanone, N, N Dimethylformamide, dimethylsulfoxide, tetrahydrofuran, N-methyl-2-pyrrolidone, benzene, toluene, chlorobenzene, styrene, polyesterpolyols, polyetherpolyols, methyl ethyl ketone, ethylene glycol monobutyl ether, diethylene glycol, mixtures of the abovementioned solvents with one another and / or mixtures of the abovementioned solvents with water.
• solvents uniquely combine the ability to form aggregate-free or aggregate-free solutions with the carbon particles, while at the same time leading to swelling of the elastomer surface when the choice is matched to the polymer. Mixtures of the abovementioned solvents relate to cases in which the solvent in the desired mass fraction is also soluble in water.
• the contacting of the surface layer comprising an elastomer with the preparation of the carbon particles can take place inter alia by immersion, application, printing, brushing, spraying and / or pouring.
• immersion in a dip can be For example, treat objects easily completely.
• a continuous process for producing a thus treated polymer film can be easily realized.
• the printing of elastomeric articles for example by screen printing, allows the representation of electrically conductive structures such as printed conductors on the elastomeric article.
• the elastomer is selected from the group comprising polyacrylate, acrylic ester rubber, polyacrylonitrile, poly (acrylonitrile-co-butydiene-co-styrene), poly (acrylonitrile-co-methyl methacrylate), polyamide, polyamide-imide, polyester , Polyetheretherketone, polyetherester, polyethylene, ethylene-propylene rubber, poly (ethylene-co-tetrafluoroethylene), poly (ethylene-co-vinylacetate), poly (ethylene-co-vinylalcohol), fluoro-silicones, perfluoroalkoxypolymer, (natural) Rubber,
• Butadiene-co-styrene nitriles, olefins, polyphosphazenes, polypropylene, poly (methyl methacrylate), polyurethanes, polyvinyl chloride, polyvinyl fluorides and / or silicones.
• the surface layer of the elastomer is partially covered by a mask.
• the mask covers parts of the surface and leaves other areas free. In this way, electrically conductive structures on the elastomer surface such as printed conductors and the like can be represented.
• the elastomer surface obtained according to the invention may, for example, have a resistivity of the surface layer of> 10 -3 ohm cm to ⁇ 10 8 ohm cm.
• the resistivity can be determined by the standard ASTM D 257.
• this resistance is in a range of> 1 ohm cm to ⁇ 1000000 ohm cm, more preferably of
• the layer thickness required for calculating the specific resistance p can be obtained from electron microscope images of a sample cross section.
• the present invention also relates to a stretchable electrode comprising an elastomer having a surface layer comprising an electrically conductive carbon particle obtainable by a process according to the invention, wherein the elastomer has a glass transition temperature T g of> -130 0 C to ⁇ 0 0 C and wherein further in the Elastomer, the stress ⁇ does not decrease with increasing elongation.
• T g glass transition temperature
• Tensile electrodes according to the invention are useful, for example, in elastomer molded parts, which are then to be painted by an electrostatic powder coating or electrocoating or to be galvanized. Other examples are generally electronic components or cable sheathing with an antistatic coating. Particularly preferred uses are given below.
• the carbon particles are present in the surface layer to a depth of ⁇ 10 ⁇ m below the surface.
• the surface layer comprises an elastomer.
• the particles in this surface layer form a network, so that an electrical conductivity occurs.
• the particles may also be present to a depth of ⁇ 5 ⁇ m or ⁇ 1 ⁇ m below the surface.
• articles which comprise the elastomeric surface layer provided with carbon particles and additionally comprise further materials They may, for example, be commodities which at least partially comprise an elastomer surface and in which surface or elastomer surface layer the electrically conductive carbon particles have been introduced.
• the carbon particles are present within the elastomeric material of the surface layer comprising them in a proportion of> 0.1% by weight to ⁇ 10% by weight.
• the proportion can also be in a range from> 0.5% by weight to ⁇ 4% by weight or from> 1% by weight to ⁇ 5% by weight.
• this indicates the content of carbon particles in the surface layer.
• the boundary of the surface layer inside the article, from which the elastomer material is no longer included in the calculation, is formed by the lowest (innermost) line, up to which the carbon particles occur in the elastomer region.
• the percolation limit for the carbon particles can be exceeded, so that the electrical conductivity is greatly improved.
• this has a resistivity of the surface layer of> 10 ⁇ 3 ohm cm to ⁇ 10 8 ohm cm.
• the resistivity can be determined by the standard ASTM D 257.
• this resistance is in a range of> 1 ohm cm to ⁇ 1000000 ohm cm, more preferably from> 10 ohm cm to ⁇ 100000 ohm cm.
• the carbon particles are unfunctionalized, multi-walled carbon nanotubes with a diameter of> 3 nm to ⁇ 100 nm.
• the diameter here refers to the mean diameter of the nanotubes. It can also be in a range from> 5 nm to ⁇ 80 nm and advantageously from> 6 nm to ⁇ 60 nm.
• the length of the nanotubes is initially not limited. However, it may, for example, be in a range of> 1 ⁇ m to ⁇ 100 ⁇ m and advantageously of> 10 ⁇ m to ⁇ 30 ⁇ m.
• the latter has a first and a second surface layer comprising electrically conductive carbon particles, wherein the said first and second surface layers are arranged opposite one another and are separated from one another by an elastomer layer. Due to the manufacturing process, the first and second surface layers are integrally bonded to the separating, electrically insulating elastomer.
• this comprises an additional electrically conductive layer arranged on the surface layer comprising electrically conductive carbon particles, wherein the additional electrically conductive layer breaks or tears when the surface layer expands before it.
• the additional electrical layer can be, for example, a conductive lacquer, a conductive paste, a metal layer or a layer of an electrically conductive polymer. Examples of metals are precious metals, copper and / or tin.
• the additional electrical layer may, but is not limited to, have a thickness of> 10 nm to ⁇ 50 ⁇ m or of> 20 nm to ⁇ 10 ⁇ m.
• the material of the additional electrically conductive layer is selected so that the additional layer first breaks or tears when the surface layer is stretched. The advantage of this is that the electrical conductivity of the overall system does not abruptly collapse due to the contact of the broken or cracked coating with the surface layer comprising carbon particles, but is still maintained to a certain extent.
• the power density of a stretchable electrode decreases with time due to the stress, but does not completely extinguish. This behavior is particularly favorable when the elastomer is subjected to cyclic elongation and relief and the electrical conductivity is required all the time.
• the additional electrically conductive layer comprises gold, silver, copper, indium tin oxide, fluorine doped tin (IV) oxide, aluminum doped zinc oxide, antimony doped tin (IV) oxide and / or poly (3,4-ethylenedioxythiophene).
• Gold can be applied by sputtering, for example.
• Poly (3,4-ethylenedioxythiophene) is commonly referred to as PEDOT or PEDT and may be applied from a formulation of the polymer.
• the elastomer article according to the invention is present as a composite of a carrier material with the elastomeric surface layer comprising electrically conductive carbon particles.
• support materials are ceramics, metals, but also other polymers such as polycarbonates or polyolefins.
• a metal molding may first be coated with the elastomer, and then the elastomeric surface layer may be provided with the carbon particles and the additional electrically conductive layer.
• the invention further relates to the use of an electrode according to the invention as an electromechanical transducer, as an electromechanical actuator and / or as an electromechanical sensor.
• the elastomer in the electrode is an electroactive polymer, and especially a dielectric elastomer.
• FIG. 1 shows an electrode arrangement with a multilayer structure
• FIG. 2, 3 and 4 conductivity measurements under strain for different elastomer samples
• FIG. 5a, 5b, 6a, 6b, 7a, and 7b are scanning electron micrographs of various elastomer samples
• FIG. 1 schematically shows an electrode arrangement according to the invention with a multilayer structure. Starting from an elastomeric workpiece were in the upper (1) and the lower (2)
• Carbon particles such as carbon nanotubes. These particles are represented by dashes or dots in the respective layers (1, 2). It can be seen that the particles have a limited penetration into the
• the surface layers (1, 2) are in each case an additional electrically conductive layer (4, 5).
• the surface layers (1, 2) are separated from each other by a particle-free elastomer layer (3). Due to the manufacturing process, the electrode is still constructed in one piece with respect to the surface layers (1, 2) and the surface layers are bonded to the particle-free layer (3).
• the electrodes shown may, with suitable dimensions, serve for example as a film-shaped capacitor or as an electroactive polymer (EAP).
• EXAMPLES relate to the functionalization of two elastomers El and E2.
• Elastomer El was a thermoplastic polyurethane (DESMOPAN® 3380A, Bayer Material Science AG), having a Shore A hardness according to ISO 868 of 80 and a glass transition temperature T g of -35 0 C.
• the glass transition temperature Tg of the elastomer E2 was -65 0 C.
• the mentioned in the Examples carbon particles (CNT) for a carbon nanotube in the form of multi-walled carbon nanotubes with the trade name BAYTUBES® C 150 P from Bayer Material Science AG.
• the other type of carbon particles was carbon black in the form of carbon black (Ketjenblack 600).
• PEDOT used as coating agent was poly-3,4-ethylenedioxythiophene with the trade name Clevios P® from HCStarck. This was as a preparation of 0.3% by weight in demineralized water.
• the dip solution was prepared by sonicating a defined amount of carbon particles in the solvent by means of ultrasonic lance and used immediately.
• the ultrasonic frequency was 20 kHz and the power density 300 W / kg.
• the samples were completely immersed in the dip formulation and sonicated for a defined time in an ultrasonic bath. After removal, the surface was rinsed briefly with acetone, dried completely at room temperature and then rubbed off with an aqueous soap solution.
• the optional coating of the CNT-functionalized elastomers was carried out in a second step by the vapor deposition of gold (Cressington device, model Sputter Coater 108auto) or dipping for 20 seconds in the aforementioned PEDOT-containing solution.
• the applied gold layers were opaque and shiny metallic. Therefore, a layer thickness of over 10 nm was assumed.
• surface and volume resistivities were measured according to ASTM D 257 standard. Furthermore, the course of the surface resistance was measured as a function of the mechanical strain. For this purpose, rectangular bars for tensile tests analogous to DIN 53504 were punched out of the elastomers and the terminals were electrically connected equipped against the tractor isolated, opposite the sample conductive contacts. With a conventional Keithley Model 2400 multimeter, the resistance across the sample was measured continuously during the slow-running tensile test, pulling speed 1 mm / min, and in a second step the force-deformation curve was synchronized with the resistance measurement over the time stamp of the individual measurement.
• FIG. 2 shows the dependence of the force F (left y-axis) or the resistance of the tensile bar of the sample R (right y-axis) on the strain D (x-axis) for different variants of the elastomer EIe.
• Traces 100 and 110 refer to the force during deformation. Curve 100 is a superposition of two curves that are almost congruent. One of these curves relates to the elastomer sample EIe without further coating, the other the elastomer sample EIe with gold layer. At about 275% elongation, the measurement for the gold-coated sample EIe was discontinued, as can be seen from the reduced thickness of the curve 100 above this strain. From the course of these curves it follows that the additional gold layer exerts no influence on the mechanical properties of the elastomer.
• the trace 110 refers to a sample of the elastomer EIe with an additional layer of PEDOT.
• Curves 120, 130 and 140 represent the course of the resistance R as a function of the deformation D for different samples of the elastomer EIe.
• the curve 120 refers to a gold-coated sample. Again, the measurement was stopped at about 275% elongation.
• Curve 130 refers to an elastomer EIe without further coating.
• curve 140 relates to a PEDOT coated sample of the elastomer EIe. It can be clearly seen that elastomer E1e has a non-vanishing conductivity under deformation, which can be further significantly improved with an additional, conductive surface layer in certain deformation ranges.
• FIG. FIG. 3 again shows the dependence of the force F (left y-axis) for the elastomer EIe in measurement curve 210. A rough estimate shows that the resistance in the measured strain range of about 230% increases by about two orders of magnitude.
• FIG. FIG. 4 relates to an untreated sample of the elastomer El which has not been functionalized with carbon particles and which has not been immersed in acetone (as would be the case for a sample of the name EIa).
• the figure shows the dependence of the force F (left y-axis) or in measurement curve 300 of the resistance R (right y-axis) of the strain D (x-axis) for a sputtered on both sides with gold sample of the elastomer El in curve 310.
• the conductivity of the gold-sputtered sample collapses during deformation even at small deformations.
• Figures 5a, 5b, 6a, 6b, 7a and 7b show scanning electron microscope (SEM) images of various samples according to the invention. They were made with a type ESEM Quanta 400 SEM from FEI.
• FIG. 5a shows a SEM image of the surface of a sample of the elastomer E2b.
• a enlarged image of this sample is shown in FIG. 5b.
• FIG. FIG. 6a shows an SEM image of the surface of a sample of the elastomer E2c and FIG. 6b shows an enlarged picture of this sample.
• FIG. FIG. 7a shows an SEM image of the surface of the surface of a sample of the elastomer E2d and
• FIG. 7b shows an enlarged SEM image of this sample.
• the particles ie carbon nanotubes and / or soot particles

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