Electric heating compositions and related composite materials and methods

Abstract

Compositions and methods related to electrothermal nanomaterial compositions for heating surfaces are provided. [Solution] Heating applications include those for rotational molding. Nanomaterials may include silver nanowires, silver nanoflakes, carbon nanotubes, carbon nanofibers, nanographite, and carbon black. The heating composition may also include binders and solvents. Processing of the heating composition using coupling agents, silicone resin intermediates, and binder resins is provided. Methods for manufacturing heating panels and heating film sheets are provided. Methods for manufacturing panels and film sheets, and methods for preparing surfaces with the heating composition using a multilayer process are also provided.

Description

Technical Field

[0001] Embodiments of the present specification relate to electrothermal compositions. Specifically, embodiments of the present specification relate to electrothermal compositions containing conductive nanomaterials and related composite materials and methods.

Background Art

[0002] Conductive compositions and coatings have various applications. Generally, a conductive coating is disposed in thermal contact with a substrate to be heated. The coating receives an applied current across the coating, resulting in conduction of thermal energy to the substrate. Arc discharge can be minimized by disposing and embedding wires, foil electrodes, or conductive paints forming positive and negative terminals in conductive contact with the coating. As described in U.S. Patent No. 6,818,156 (Miller ‘156) by Miller, some useful applications of conductive coatings include heating of floors, walls, ceilings, roofs, and gutters. Still other applications include preheating of engine oil in transportation vehicles and power plants, local heating of batteries and auxiliary systems, heating of vehicles and tankers transporting oil and other liquids, coal transport vehicles, and de-icing of aircraft wings. Miller ‘156 specifies possible useful applications, such as for the purpose of offsetting the effects of various cold climates and for household / commercial electrical appliances and medical devices.

[0003] The coating itself includes a conductive particulate material dispersed in a binder suitable for application to a substrate using a brush, roller, spray, etc. Optionally, a primer may be applied between the coating and the substrate. When the substrate is itself a conductor such as metal, it is common to apply a highly dielectric non-conductive primer or intermediate layer to avoid short circuits. Instead, the substrate may be a highly dielectric non-conductive material and a primer may not be required. If the thickness of the coating or primer is not uniform, non-uniform heating or “hot spots” of the substrate may occur, which can lead to decomposition of the coating or primer.

[0004] Miller's U.S. Patent No. 6,086,791 (Miller'791) relates to a conductive heating coating having conductive flake carbon black with a particle size of approximately 5 to 500 μm and conductive flake graphite with a particle size of approximately 5 to 500 μm. In an improved heating coating, Miller'156 includes conductive carbon black particles with a particle size of approximately 0.001 to 500 μm and conductive graphite particles with a particle size of approximately 0.001 to 500 μm. More recently, Miller's U.S. Patent No. 10,433,371 (Miller'371) relates to a composition comprising a conductive carbon component (selected from the group consisting of conventional thermal black, furnace black, lamp black, channel black, surface-modified carbon black, surface-functionalized carbon black, and heat-treated carbon) and a resistive component containing graphite with a crystallinity of 99.9%.

[0005] However, the use of carbon components has many limitations. Elemental carbon has a negative thermal resistance coefficient, meaning that resistance decreases and conductivity increases as temperature rises. This property of elemental carbon in conductive coatings results in a lack of the desired conductive stability for many commercial applications. The use of carbon black as a conductor generally requires high concentrations to achieve the conductivity required for these applications. However, formulations containing high concentrations of carbon black tend to be brittle and crack due to thermal expansion and contraction when subjected to thermal cycling. This can result in the formation of hot spots (due to localized aggregation of conductive particles), cold spots (due to crack formation), difficulty in obtaining suitable electrode materials, and delamination of the coating layer. [Overview of the project]

[0006] This specification provides electrothermal compositions formed of a network of conductive nanomaterials for applications such as coatings, paints, inks, pastes, and films that convert electrical energy into heat. This specification also provides composite materials using the electrothermal compositions. The composite materials may be in the form of coatings, panels, and sheets. This specification also provides related methods for manufacturing the electrothermal compositions and composite materials, as well as methods for preparing surfaces for heating using the compositions and methods for preparing surfaces including rotational molds for heating using the composite materials. Embodiments of the electrothermal compositions disclosed herein have been observed to exhibit improved conductivity stability with respect to temperature changes and to have a much slower degradation rate than electrothermal compositions that primarily use carbon. Furthermore, the disclosed electrothermal compositions provide at least one of improved consistency, ease of molding, ease of coating, increased uniform thickness, increased reliability, increased flexibility, and increased thermal stability. Electrothermal coatings using the provided electrothermal compositions exhibit reduced hot spots and are easy to integrate and connect with electrodes.

[0007] Embodiments of the compositions described herein have an improved integration of an insulating layer, a heating layer, and conductive wires. The improved integration provides improved energy efficiency and durability. In the embodiments, electrodes referred to as cathodes and anodes are arranged in a pattern to minimize electrical channeling.

[0008] The embodiment includes using panels and sheets to avoid applying coatings directly to molds. This enables a more cost-effective process, as they are easy to install and allow for the manufacture of more complex patterns using computer numerical control (CNC) technology. This also makes it possible to use panels and sheets in a wider range of applications.

[0009] By using the provided electrothermal composition in the field of rotational molding, the need for ovens and related equipment is eliminated. Using the provided electrothermal composition in rotational molding improves energy efficiency and enhances heating control. Improved heating control allows for greater control over varying material thicknesses within a single mold. The use of electrothermal coatings in rotational molding can also facilitate the operation of slip rings, rather than using heaters and ducts in fluid connections or other systems where high-temperature fluids are used. Embodiments of the electrothermal composition, including the use of prefabricated panels or sheets, are suitable for a variety of applications, including heating floors, walls, ceilings, roofs and gutters; heating clothing; therapeutic heating pads; preheating engine oil in transport vehicles and power plants; localized heating of batteries and auxiliary systems; heating of vehicles and tankers carrying petroleum and other liquids; heating of coal carriers; de-icing of aircraft wings; offsetting the effects of cold weather; and use in household / commercial electrical appliances and medical equipment.

[0010] In one embodiment, the heating element comprises a network and binding components of conductive nanomaterials, the nanomaterials making up 10% to 80% of the mass of the heating element, and the heating element has a capacitance of 0.05 ohms / cm². 2 ~35 ohms / cm 2 It has a resistivity of .

[0011] In one embodiment, the heating element composition has nanomaterials comprising 40% to 70% of the mass of the heating element composition, and the heating element composition has a resistance of 0.08 ohms / cm². 2 ~10 ohms / cm 2 It has a resistivity of .

[0012] In one embodiment, the electric heating composition comprises a conductive nanomaterial having nanowires, nanotubes, nanoflakes, nanoparticles, or a combination thereof.

[0013] In one embodiment, the electric heating composition has a conductive nanomaterial including nanowires, and the network of conductive nanomaterials has interconnected strands of nanowires.

[0014] In one embodiment, the electric heating composition has a network of conductive nanomaterials further comprising at least one of nanoflakes and nanoparticles.

[0015] In one embodiment, the electric heating composition has interconnected strands having an average diameter of about 35 to 250 nm and an average length of about 8 to 60 μm.

[0016] In one embodiment, the heating element has interconnected strands having an average diameter of about 55 to 176 nm and an average length of about 14 to 30 μm.

[0017] In one embodiment, the conductive nanomaterial network is an electrically heated composition having an average network mesh size of less than 10 nm.

[0018] In one embodiment, the electric heating composition has a conductive nanomaterial containing silver nanomaterials.

[0019] In one embodiment, the electric heating composition has at least one carbon component.

[0020] In one embodiment, the electric heating composition has at least one carbon component, which includes at least one of carbon nanotubes, carbon nanofibers, nanographite, and carbon black.

[0021] In one embodiment, the electric heating composition has a binding component that includes a silicone resin.

[0022] In one embodiment, an electric heating panel for applying heat to a surface upon contact has three layers. The first layer comprises an electrical insulating material. The second layer comprises an electric heating composition disposed on the first layer. The third layer comprises an anode and a cathode arranged in a pattern on the second layer.

[0023] In one embodiment, the electric heating panel has a layer of thermally conductive adhesive applied to a first layer and is placed on a removable backing sheet.

[0024] In one embodiment, the electrothermal film sheet for generating heat has two layers. The first layer includes a sheet of non-conductive film. The second layer includes an electrothermal composition disposed on the first layer.

[0025] In one embodiment, the electrothermal film has a third layer which is a sheet of non-conductive film for covering the second layer.

[0026] In one embodiment, the sheet of non-conductive film contains silicone.

[0027] In one embodiment, the sheet of non-conductive film contains polyimide.

[0028] In another aspect, a method of manufacturing an electrothermal panel for applying heat to a surface upon thermal contact with the surface includes forming a layer of electrically insulating material, forming a layer of electrothermal composition on the layer of electrically insulating material, and forming an anode and a cathode on the layer of electrothermal composition.

[0029] In one embodiment of the manufacturing method, the layer of electrothermal composition contains silver nanomaterials.

[0030] In another aspect, a method of manufacturing an electrothermal film sheet for generating heat includes forming a first layer of non-conductive film and forming a layer of electrothermal composition on the first layer.

[0031] In one embodiment, the method includes forming a second layer of non-conductive film to cover the layer of electrothermal composition.

[0032] In one embodiment of the manufacturing method, the layer of electrothermal composition contains silver nanomaterials.

[0033] In another aspect, a method of preparing a surface for heating using an electrothermal composition includes providing a mold made of a non-conductive material having one or more heat transfer surfaces, applying a layer of electrothermal composition to the one or more heat transfer surfaces, and applying electrodes to the layer of electrothermal composition.

[0034] In one embodiment of the manufacturing method, the mold includes one or more heat transfer surfaces of a conductive material, and includes applying a layer of electrical insulating material to the heat transfer surfaces before applying a layer of the electric heating composition.

[0035] In one embodiment of the manufacturing method, the layer of the electric heating composition contains silver nanomaterial. [Brief explanation of the drawing]

[0036] [Figure 1] This is a diagram of some elements of one embodiment of an electric heating composition. [Figure 2] This is a flowchart illustrating an exemplary method for manufacturing an electric heating composition according to several embodiments. [Figure 3] Figure 2 is a flowchart showing additional steps for providing conductive nanomaterials in the method. [Figure 4] This is a side view of one embodiment of a coating including an insulating layer, a heating layer, and a conductive wire layer. [Figure 5] This is a perspective view of an example of a rotational molding die. [Figure 6A] This is a plan view of one embodiment of a panel including an insulating layer, a heating layer, and a layer of conductive wires applied in a pattern. [Figure 6B] This is a cross-sectional view of the panel in Figure 6A along the cutting line 6-6. [Figure 7A] This is a plan view of another embodiment of a panel including an insulating layer, a heating layer, and a layer of conductive wires applied in a pattern. [Figure 7B] This is a plan view of another embodiment of a panel including an insulating layer, a heating layer, and a layer of conductive wires applied in a pattern. [Figure 8] This is a flowchart illustrating an exemplary method for manufacturing an electric heating panel according to several embodiments. [Figure 9] This flowchart shows the steps of applying an electro-heating coating to a rotary mold and heating the rotary mold, according to several embodiments. [Figure 10]This is a flowchart illustrating exemplary methods for heating rotational molds according to several embodiments. [Figure 11] This is a side view of an embodiment of a coating that includes an electric heating layer on a film layer. [Figure 12] This is a side view of one embodiment of a coating that includes an electrically heating layer between two layers of film. [Figure 13] This is a flowchart of a method for manufacturing a sheet having a layer of an embedded electric heating composition, according to several embodiments. [Figure 14] This is a plan view of one embodiment of a film sheet containing an electrically heated composition applied in a pattern. [Figure 15] This is a plan view of another embodiment of a film sheet containing an electrically heated composition applied in a pattern. [Figure 16] This is a plan view of another embodiment of a film sheet containing an electrically heated composition applied in a pattern. [Figure 17] This is a plan view of another embodiment of a film sheet containing an electrically heated composition applied in a pattern. [Modes for carrying out the invention]

[0037] Generally, this disclosure provides electrothermal compositions, related composite materials, and methods for applications such as coatings, paints, inks, pastes, and films that convert electrical energy into heat. The electrothermal composition may comprise a conductive nanomaterial and a binder, the nanomaterial being dispersed within the binder and forming a network of interconnected conductive pathways.

[0038] As used herein, “nanomaterial” refers to any material having at least one dimension in the nanometer range. In some embodiments, the metal of the nanomaterial includes silver. In other embodiments, the metal includes copper, gold, or any other suitable metal. Silver may be particularly suitable for the compositions disclosed herein due to its high conductivity and oxidation resistance.

[0039] Nanomaterials may be in the form of nanoparticles, nanowires, nanotubes and / or nanoflakes. As used herein, “nanoparticles” refers to particles in the nanometer range, “nanowires” refers to nanostructures having a diameter in the nanometer range and a length-to-width ratio greater than 100, “nanoflakes” refers to heterogeneous pieces of nanomaterial in the nanometer range where one dimension is substantially smaller than the other two dimensions, and “nanotubes” refers to tubular nanostructures having a diameter in the nanometer range and a length-to-width ratio greater than 100.

[0040] In some embodiments, the nanomaterials are surface-modified. For example, the nanomaterials may be surface-modified with a silane coupling agent to improve their compatibility with the binder resin.

[0041] As used herein, “binder” refers to any substance capable of accepting nanomaterials. In some embodiments, the binder includes, for example, a resin such as a silicone resin. Preferred binders include long-chain silicone resin mixtures. In some embodiments, the silicone resin is a high-temperature silicone resin (e.g., DOWSIL® RSN-0805 or DOWSIL® RSN-0806).

[0042] In some embodiments, the heating composition further comprises one or more carbon components. In some embodiments, the carbon components include carbon nanomaterials. Examples of carbon components include carbon nanotubes, carbon nanofibers, nanographite, and carbon black. Carbon components are generally less expensive than metal nanoparticles and can improve the fluid properties of the heating composition.

[0043] The heating element may contain about 5% to about 50% nanomaterial when wet (about 10% to 80% of the mass when dry). In some preferred embodiments, the heating element may contain about 8.5% to 31% nanomaterial when wet (about 40% to 70% of the mass when dry). In embodiments, the nanomaterial may contain up to 30% carbon nanomaterial, including, but not limited to, carbon nanotubes.

[0044] The heating element has a resistance of approximately 0.05 ohms / cm². 2 ~35 ohms / cm 2 It may have a resistivity of about 0.08 ohms / cm². In some preferred embodiments, the heating composition has a resistivity of about 0.08 ohms / cm². 2 ~10 ohms / cm 2 It has a resistivity of . Referring to Figure 1, in one embodiment, the electrothermal composition comprises a network 100 of conductive nanomaterials in a suitable binder (not shown). In this embodiment, the network of conductive nanomaterials comprises a combination of silver nanowires 102, carbon nanotubes 104, and silver nanoflakes 106, which are arranged in a non-uniform direction and have connection points 110 to form an intermesh network of co-continuity of conductive paths. In this embodiment, the silver nanowires 102 have an average diameter and average length of about 35 to 250 nm and about 8 to 60 μm, respectively, and an average network mesh size of less than 10 nm. In this embodiment, the silver nanowires 102 have an average diameter and average length of about 55 to 176 nm and about 14 to 30 μm, respectively, and an average network mesh size of less than 10 nm. The average network mesh size refers to the average distance between connection points 110. In this embodiment, silver nanoparticles (not shown) can be used instead of or in combination with the silver nanoflakes 106. In one embodiment, the silver nanoflakes 106 (and / or nanoparticles) may be about 10 μm in size. In an exemplary embodiment, the electrothermal composition includes silver nanowires 102, carbon nanotubes 104, silver nanoflakes 106, and nanoparticles.

[0045] While silver has been shown to be a suitable conductive material in the form of conductive nanoparticles, any conductive nanoparticles with similar properties to silver can be used. For example, gold has favorable properties in terms of conductivity, oxidation resistance, and resistance. Copper has desirable cost and conductivity properties, but is less preferred because it is more easily oxidized than silver.

[0046] Silver is a suitable component for electrothermal compositions due to its high conductivity and oxidation resistance. Embodiments relating to electrothermal compositions include silver nanoparticles, nanoflakes, and nanowires. In embodiments, other conductive nanoparticles may be present together with the silver nanoparticles. In one embodiment, silver nanowires are used. In embodiments, silver nanowires can be synthesized using a chemical reaction, in which case silver nitrate is used as a precursor of atomic silver. By applying a polymeric surfactant, the crystallization of atomic silver can be induced to form a one-dimensional rod-like structure rather than a spherical one. The functional one-dimensional structure of the nanowires is suitable for forming conductive pathways that form a conductive network and generally maintains good conductivity even under deformation, thus minimizing junction resistance. By exchanging the ligands of the silver nanowires, the silver nanowires can be homogeneously dispersed in the electrothermal composition. This homogeneity helps the electrothermal composition have consistency and reproducible mechanical and electrical properties.

[0047] In certain applications, it may be desirable to include carbon-based components in the electrothermal composition. Carbon-based components are less expensive than silver nanoparticles and, when included in the composition, can provide improved flow properties. Examples of carbon components include carbon nanotubes, carbon nanofibers, nanographite, and carbon black. Adding carbon black particles at lower concentrations can improve coating uniformity, resulting in improved uniformity of the applied coating and enhanced stability of suspended particles. Carbon nanotubes can also be used to form conductive pathways. Because carbon nanotubes have higher conductivity at a lower mass than carbon black, they can be a suitable component.

[0048] In embodiments, the heating composition further comprises one or more binders or conjugates for holding the heating composition together once cured. In embodiments, the binder is a silicone resin such as DOWSIL® RSN-0805 or DOWSIL® RSN-0806. The silicone resin has suitable heat resistance, weather resistance, UV stability, sufficiently high dielectric strength to prevent dielectric breakdown, and water repellency. Furthermore, these resins are available in a variety of viscosities, from high-viscosity liquids to solids.

[0049] Here, various embodiments include conductive nanomaterials such as nanoparticles, nanotubes, nanoflakes, and / or nanowires dispersed in the binder, which can also act as primers, thus eliminating the need to separately apply primers such as those in Miller'791 and Miller'156. Furthermore, in embodiments, the substrate itself may be an intermediate layer to maximize application to many different types of objects, which can be readily manufactured in the form of one or more panels, each of which is treated with the electrothermal composition. In other embodiments, the composition may be applied directly to a non-conductive film sheet and wrapped in a sheet without the use of conductive wires. By applying the composition to a panel or film sheet having known preferred properties, the quality of the treatment can be made reproducible and consistent. The treated panel or film can be applied to the object to be heated using various conventional techniques, including bonding with conventional heat-resistant adhesives suitable for the object. Furthermore, the properties of the composition and the use of panel-shaped substrates allow for the use of CNC plotters for the application of the composition, electrodes, or both, and for application to complex panel shapes in some embodiments.

[0050] Electrical heating compositions containing conductive nanomaterials allow for more precise structural control than electrical heating compositions containing conductive materials on a micron scale or larger.

[0051] The electrothermal composition is suitable for many applications requiring localized heating of a surface and can be stable even at high temperatures. The use of the electrothermal composition for heating a surface provides directed and efficient heating. The use of the disclosed electrothermal composition can result in improved heating efficiency, with energy requirements in rotational molding applications being approximately 10% to 90% lower compared to convection techniques.

[0052] Manufacturing of electric heating compositions Figure 2 is a flowchart of an exemplary method 200 for producing an electrothermal composition according to several embodiments. Method 200 may be used to produce embodiments of the electrothermal composition described above. Referring to Figure 2, block 202 provides a conductive metal nanomaterial. As used herein, “provide” means to manufacture, purchase, acquire or otherwise obtain the nanomaterial. In embodiments, the nanomaterial includes nanoparticles, nanowires, nanotubes and / or nanoflakes, which may be silver as described in more detail above. Block 204 provides a suitable binder as detailed above. In block 206, the conductive metal nanomaterial, which may be treated with one or more coupling agents and silicone resin intermediates as described below, can be homogeneously dispersed in a diluted binder resin. Proper dispersion can be achieved by multiple steps of alternating stirring and sonication. The stirring rate, and therefore the shear rate, used may depend on the volume of the mixture. In embodiments, a carbon component may also be dispersed in the binder.

[0053] Figure 3 is a flowchart showing an additional step 300 for providing the nanomaterial in method 200 of Figure 2. Referring to Figure 3, in the embodiment, in the additional step 300, the conductive metal nanomaterial is treated with a coupling agent 302 and / or a silicone resin intermediate 304 and then combined with a binder. In block 302, the conductive metal nanomaterial may be surface-treated with one or more silane coupling agents using a suitable method as described in detail below. In block 304, the conductive metal nanomaterial may be treated with a reactive silicone resin intermediate or a functional silicone resin to improve its dispersibility in the binder resin as described in detail below.

[0054] Surface treatment of additives with coupling agents and / or silicone resin intermediates improves the homogeneity, stability, and performance of the composition. However, omitting these steps simplifies and shortens the manufacturing procedure and reduces manufacturing costs. The resulting electrothermal composition may be less stable than that prepared using surface-treated additives. Less stable coatings may require stronger mixing and application within a short time after mixing.

[0055] Treatment of nanomaterials with coupling agents In one embodiment of block 302, silver flakes and / or silver nanoparticles may be treated with one or more silane coupling agents. The purpose of this treatment is to graft the silane coupling agents onto the surface of these particles to improve their compatibility with the binder resin. In this embodiment, sufficient compatibility between the silver flakes and the binder is ensured while allowing conductive additives or direct contact between particles by maintaining a surface coating of less than about 10%.

[0056] Surface treatment of silver flakes and silver nanoparticles can be carried out by any preferred method, including conventional methods such as grafting of silane coupling agents with acid or base catalysts onto the nanomaterial surface. Conventional methods can be modified to facilitate manufacturing equipment and requirements, such as by changing reaction conditions such as temperature and the molar ratio of reactants, as will be described in more detail in the following examples.

[0057] Treatment with silicone resin intermediates In one embodiment of block 304, silver nanowires or carboxyl or hydroxyl-functionalized multilayer carbon nanotubes (commercially available) can be treated with reactive silicone resin intermediates such as DOWSIL® 3074 and DOWSIL® 3037, or functional silicone resins such as DOWSIL® RSN-0805 or DOWSIL® RSN-0806, to improve their dispersibility in the binder resin. Note that the surface density of the graft resin can be kept low to avoid crosslinking of the resin.

[0058] Multilayer composite material having an insulating layer and a conductive layer This specification also provides electrothermal composite materials including the electrothermal compositions described above. An exemplary composite material 400 is shown in Figure 4. The composite material 400 of this embodiment is a coating comprising an insulating layer 402, a conductive layer 406, and an electrothermal layer 404 between them. The electrothermal layer 404 may include any embodiment of the electrothermal composition described above.

[0059] Conventional electrolytic heating coatings may lack proper harmony of thermal expansion coefficients, resulting in different layers of the coating expanding and contracting at varying rates during the heating process. These varying rates of expansion and contraction between layers can lead to cracking and separation of the layers.

[0060] In applications using conductive substrates that require an insulating layer, cracks in the insulating layer can lead to direct contact between the heating layer and the conductive substrate. Such contact can cause electrical short circuits, destruction of the insulating layer, and ultimately, sudden failure of the heating layer. Separation of the insulating layer and the heating layer can reduce the efficiency of heat transfer from the heating layer to the heated surface (through the insulating layer).

[0061] Cracks in conductive wires can similarly reduce conductivity, worsen the channeling of electrical paths (within the wire), and increase degradation. Cracks that disrupt the electrical conduction of a conductive element can render the element unusable. Separation of the conductive wire from the heating layer can render the conductive wire ineffective due to the lack of a valid electrical connection. Separation between the conductive wire and the heating layer can also cause arc discharge, which can accelerate the degradation of the entire coating layer. Composite material 400 with an integrated layer can avoid these problems.

[0062] In the embodiment, the insulating layer 402 is electrically insulating and contains a binder. In the embodiment, the insulating layer 402 may further contain a dispersant, a defoaming agent and / or other materials to improve mechanical strength, insulation resistance, solvent resistance and prevent pinhole formation.

[0063] In embodiments, the insulating layer 402 contains the same binder used in the heating composition. In embodiments, this binder contains a silicone resin such as DOWSIL® RSN-0805 or DOWSIL® RSN-0806. It has been found that the use of this binder results in good compatibility with the heating layer. Furthermore, the insulating layer 402 has been found to have high heat resistance, high dielectric strength, and is substantially pinhole-free. In one embodiment, the insulating layer contains titanium oxide or titanium dioxide nanopowder (e.g., AEROXIDE® TiO2 P 25), aluminum oxide, bentonite, and / or mica to improve mechanical strength, insulation resistance, solvent resistance, and prevent pinhole formation. In embodiments, the insulating layer may contain a dispersant to improve the homogeneity of the composition. In embodiments, the insulating layer may contain a defoaming agent (e.g., TEGO Airex 900) to prevent air trapping and pinhole formation. In this embodiment, all components of the insulating layer can be combined and mixed simultaneously by mechanical stirring and ultrasonic treatment.

[0064] In this embodiment, the heating layer 404 includes silver nanowires in a binder. Using only silver nanowires in combination with a suitable binder increases cost but can improve flexibility and energy efficiency. As outlined above, the flexibility of the heating layer 404 is important for reasons of expansion and contraction. The thickness of the heating layer 404 applied can affect the heating effect, as the resistance of the applied heating layer 404 correlates directly with its thickness. As a result of this relationship, the amount of heating layer 404 required increases as the required power increases and can be adjusted to suit specific applications. In practice, the power generated by a heating composition is often limited by the limits of the available power source.

[0065] The conductive layer 406 forms a cathode and anode together with conductive wires that can apply current to the heating layer 404. When electricity is passed through the conductive layer 406, power is generated. The power generated by the heating layer 404 is directly proportional to the square of the applied voltage and inversely proportional to the resistance of the heating layer 404.

[0066] The conductive layer 406 may contain any suitable material having high conductivity. Preferably, the conductive layer 406 also has good integration with the heating (electric heating) layer 404 in terms of thermal expansion, thermal contraction and adhesion to the electric heating layer 404.

[0067] The conductive layer 406 can be applied to the heating element by printing, spraying, or other methods, which can be done manually or with a printer or CNC machine. The conductive layer 406 is compatible with both AC and DC power supplies. However, in practice, AC current is generally more readily available.

[0068] Preferably, the conductive layer 406 has high conductivity, low thermal sensitivity, and conductivity up to three orders of magnitude higher than that of the heating layer 404. It has been found that when copper foil is used as the heating layer 404, the risk of arc discharge increases due to delamination of the foil from the heating layer 404 or the formation of cracks at the foil / coating boundary.

[0069] During use, when electricity is supplied to the conductive wires of the conductive layer 406, the heating composition of the heating layer 404 generates heat. Since the composite material 400 contains multiple different layers, it may be desirable to ensure durability and performance by ensuring that each layer is compatible with and integrated with the other layers due to their different coefficients of thermal expansion.

[0070] To ensure durability, the insulating layer 402 preferably has high heat resistance, high dielectric strength at high temperatures, and is substantially defect-free. It has been found that when commercially available heat-resistant paint is used for the insulating layer 402, the heating composition of the heating layer 404 can partially dissolve the commercially available heat-resistant paint. Furthermore, it has been found that when commercially available heat-resistant paint is used for the insulating layer 402, pinholes occur in the commercially available heat-resistant paint, resulting in insufficient dielectric strength and further contributing to the accelerated deterioration of the commercially available heat-resistant paint. Porcelain coatings have also been found to be unsuitable. Porcelain coatings generally require expensive and time-consuming procedures to be applied to rigid mold surfaces. Furthermore, porcelain heating requires curing at high temperatures and is unsuitable for application to aluminum or welded sheet metal molds.

[0071] The heating element 404 can be formulated to provide desired conductivity and have mechanical flexibility during thermal expansion / contraction. In embodiments, suitable binders can be used to provide different flexibility and hardness or strength. The suitable binder, upon curing, forms a matrix that protects the conductive elements (e.g., silver nanowires) from oxidation.

[0072] Application of electrothermal coatings to multilayer composite materials In the embodiments, the electrothermal composition is applied as a coating using a wet coating process such as dip coating, spray coating, or bar coating. Because the electrothermal coating is flexible and pliable, it can be adapted to various shapes using various media, such as a rotational mold 500 as shown in Figure 5. In the embodiments, a solvent is used when preparing the electrothermal composition to provide a medium for dissolving or dispersing the components. Since the solvent evaporates as the electrothermal composition dries and hardens, the resulting electrothermal composition coating may contain little to no solvent. The binder of the electrothermal composition dissolves in the solvent, but the silver nanoparticles, nanoflakes, and nanowires are suspended in the solvent. As a result, the electrothermal composition may require stirring immediately before coating. Ultrasonic stirring has been found to be suitable for this purpose and to make the electrothermal composition suitable for coating. It has been found that the electrothermal composition thus coated can result in a coating of substantially uniform thickness. In the embodiments, the solvent may include toluene or xylene. In the embodiments, less than 5% by weight of ethanol may be used as a co-solvent.

[0073] Several observations were made regarding the carbon-based components in the heating element composition. Carbon nanofibers were found to tend to clog spray nozzles and roughen the surface of the heating element composition during application. Furthermore, it was found that mixing carbon black as a binder improved the fluidity of the heating element composition.

[0074] Heating panel Referring to Figure 6, in one embodiment, a panel 600 is provided that includes the aforementioned electrothermal composite material. The panel 600 comprises an insulating layer 602 including a layer of the aforementioned electrical insulating material. An electrothermal layer 604 including the aforementioned electrothermal composition is applied on top of the insulating layer 602. Electrodes, including an anode 606 and a cathode 608, are arranged on the electrothermal layer 604. The anode 606 and cathode 608 are in a specific pattern depending on the shape and layout of the electrothermal layer 604. In the embodiment, the electrodes are arranged such that the resistance between the anode 606 and cathode 608 is as close as possible to uniform resistance throughout the entire electrothermal layer 604. When a resistance difference exists, more current tends to flow through the path with lower resistance. The resulting difference in current across the entire electrothermal layer 604 is undesirable for several reasons. First, a temperature difference exists, which can lead to uneven heating. Second, paths through which more current flows tend to degrade faster. The conductive layer on which the anode 606 and cathode 608 are arranged to have nearly uniform resistance facilitates the transmission of current nearly evenly and substantially simultaneously across the entire associated heating layer 604.

[0075] For illustrative purposes, Figures 7A and 7B show different arrangements of the heating composition applied to a square panel. Referring to Figure 7A, the square panel 700 includes a material forming an insulating layer. A layer 702 of the heating composition is applied to the square panel 700. An electrode labeled anode 704 is positioned at one corner of the square. An electrode labeled cathode 706 is positioned diagonally opposite the anode 704. In this arrangement, the current flows unevenly, with more current flowing along the diagonal between the electrodes.

[0076] Alternatively, referring to Figure 7B, in the case of a square panel 750 to which a layer 752 of the electric heating composition is applied, the first electrode band 754 is located on the first side of the panel 750, and the second electrode band 756 is located on the second side opposite to the first side. This arrangement is thought to allow a uniform current to flow between the electrodes.

[0077] Manufacturing of heating panels Figure 8 is a flowchart of an exemplary method 800 for manufacturing an electrically heated panel that applies heat to a surface upon thermal contact. This method 800 may be used to manufacture the embodiments of the heated panel described above. Referring to Figure 8, block 802 is formed of a layer of electrically insulating material, including the insulating layer described above. In the embodiment, the insulating layer is formed as a sheet of uniform thickness with a geometric shape suitable for the intended application. In block 804, a layer of the electrothermal composition is applied to the insulating layer using the method described below. In the embodiment, the electrothermal layer is also formed as a sheet of uniform thickness and may cover all or part of the insulating layer from block 802. In block 806, electrodes designated as the anode and cathode are applied to the electrothermal layer using the method described below. The electrode pattern is made as described above.

[0078] The multilayer electrothermal composite coating applied in this manner has been found to be durable. In one example, a coated substrate was thermally cycled for more than 25 cycles per day, totaling more than 12,000 cycles. The wet coating method described above can be applied directly to surfaces that require heating. Depending on the surface characteristics, other treatments may be more appropriate. For example, if the surface is non-conductive and suitable for other applications, the electrothermal composition can be applied directly to the surface without an insulating layer. Importantly, when applying directly to a non-conductive surface, the coating should be of substantially uniform thickness. If the adhesion of the electrothermal composition to the surface is insufficient, a primer may be used. In addition, if the surface may be exposed to organic substances such as oil and gas, the coating or any of its components may further contain substances to prevent corrosion, etc. Additives included in the insulating layer, electrothermal layer, and conductive layer may need to be balanced between their intended purpose and the suitability of the coating's components.

[0079] The electrothermal composite can be applied directly as a coating to the target surface (the surface heat to be heated) or applied to a substrate (preferably a flexible thermal conductive material) to form a panel, which is then placed on the target surface. Examples of such substrates include thick (≧0.002 inch) aluminum, steel, or copper foil. These substrates can be coated with an electrically insulating heat-resistant paint two or more times, cured at about 230°C for at least 20 minutes to solidify the insulating layer, and then coated with the electrothermal composition. After curing the electrothermal composition at about 230°C for about 20 minutes, a conductive layer may be applied. A panel is formed by a combination of the substrate (including any insulating layer), the electrothermal composition, and the conductive layer.

[0080] In some embodiments, the panel can be applied to an object or surface to be heated. Once the panel is fully cured, it can be fixed to the object by thermal conduction contact. In some embodiments, the panel can be attached to the surface of an object using an adhesive compatible with the panel and surface. The adhesive may have properties similar to an insulating layer, including preferably high heat resistance to the design temperature, high dielectric strength at high temperatures, and lack of reactivity with the panel substrate or the target surface. The heat-resistant adhesive can be applied to the back surface of the panel and cured, for example, at about 230°C for at least 5 minutes. In each curing step, the temperature may be raised gradually or in multiple steps, for example, at about 60°C for about 5 minutes, at about 120°C for about 2 minutes, and at about 230°C for about 20 minutes, in order to avoid blistering of the coating. The panel is then ready for installation on the target surface.

[0081] In another embodiment, an adhesive is applied to the back surface of the panel, and the adhesive-coated panel can be peelably bonded to a non-adhesive release liner. The panel can then be stored, shipped in a convenient format, and finally installed on the target surface. The use of prefabricated panels with adhesive applied to the release liner offers many advantages, including: the ability to form the panels in a manufacturing facility according to specifications and transport them to the desired location easily and economically; and the ability to simply remove and replace any faulty panel or part thereof with a similar panel.

[0082] Rotational molding applications The application of electrothermal compositions is carried out either as a coating directly on a surface or as a panel that can be used in the field of rotary molding or rotary casting, commonly known as rotational molding. Rotational molding is widely used to form a variety of hollow, thin-walled plastic products. Rotational molding requires a heated hollow mold filled with a feed amount or shot weight of plastic powder material. The mold is slowly rotated around two vertical axes, thereby dispersing the softened material and causing it to adhere to the mold walls.

[0083] Rotational molding generally involves four steps: mold preparation, mold heating, mold cooling, and mold removal. To prepare the mold, a predetermined amount of polymer powder or polymer resin is placed into a hollow mold shell, and the mold is closed. To date, rotational molding molds are typically heated in an oven to a temperature range of approximately 260°C to 370°C, depending on the polymer used, by convection, conduction, or radiation. After heating the mold to the desired level, it is generally removed from the oven and cooled. Mold cooling is usually done using air (by a fan), water, or a combination of both. Heating ovens may require space depending on the application, but they are associated with energy efficiency (low energy efficiency) due to significant heat loss to the surrounding environment.

[0084] Referring to Figure 5, the rotational mold 500 comprises a target surface 502 to which heat is applied using an embodiment of the electric heating composition. Figure 9 shows an exemplary method 900 for heating the target surface 502 using the electric heating composition. Block 902 provides the rotational mold. As used herein, “provide” means to manufacture, purchase, obtain or otherwise acquire the rotational mold. Block 904 applies the insulating layer detailed above to the target surface 502. Block 906 applies a layer of the electric heating composition to the insulating layer in the method described below, and in embodiments similar to block 804 of method 800. Block 908 applies electrodes designated as anode and cathode to the electric heating layer in the method described below, and in embodiments similar to block 806 of method 800. Block 910 supplies power through the anode and cathode, resulting in an electric current flowing through the electric heating composition and generating thermal energy to heat the rotational mold 500.

[0085] Figure 10 is a flowchart of another method 1000 for heating the target surface 502. Block 1002 provides a rotational mold. Block 1004 applies the heating panel, fabricated according to the above description, to the target surface 502. In the embodiment, the heating panel can be attached to the target surface 502 with an adhesive as described above. Block 1006 supplies power through the anode and cathode of the panel, resulting in an electric current flowing through the heating composition and generating thermal energy to heat the rotational mold 500.

[0086] Heating rotational molds using electrothermal compositions is more energy-efficient and eliminates the need for large ovens and associated equipment typically used for mold heating. The ease with which electrothermal compositions can be molded or applied to various shapes, including complex forms, also makes their use suitable for rotational molding. The ability to control specific parts of the mold differently from others (e.g., by using independent control of panels or zones) enables rotational molding of structures with intentionally uneven walls. Furthermore, this composition has been found to function up to approximately 350°C, which is generally above the temperature required for rotational molding. Additionally, this composition has been found to have sufficient heat capacity to melt plastics, thus making it suitable for rotational molding. Moreover, heating rotational molds using electrothermal coatings is more resource-efficient than using an oven, which requires cooling the mold after the process before handling the mold, during which time the oven is unavailable for heating other molds.

[0087] Other applications of the electrothermal composition include articles that are heated but often require significant auxiliary devices such as electrical supply components and associated structures. For example, hot beverage mugs that are heated to maintain a preferred temperature typically use internal or base electrodes. Instead, mugs can be coated with the described composition, which allows for the use of multiple third-party mugs that require only electrically connected devices, such as a simplified base, and are modified solely by the addition of the composition.

[0088] Other applications of embodiments of the electric heating composition include heating floors, walls, ceilings, roofs, and gutters; preheating engine oil in transport vehicles and power plants, localized heating of batteries and auxiliary systems, heating of vehicles and tankers that transport petroleum and other liquids, heating of coal transport vehicles, de-icing of aircraft wings; and use of prefabricated panels for a variety of applications, such as offsetting the effects of cold weather, and for household / commercial electrical appliances and medical equipment.

[0089] Application of electrothermal coatings to non-conductive films This specification also provides other electrothermal composite materials including the aforementioned electrothermal composition. Exemplary composite materials 1100 and 1200 are shown in Figures 11 and 12, respectively. Referring to Figure 11, the composite material 1100 of this embodiment is in the form of a sheet and includes a layer 1102 of the electrothermal composition applied to a nonconductive substrate 1104. Once the layer 1102 of the electrothermal composition and the nonconductive substrate 1104 are fully cured, the composite material 1100 can be used as a functional panel. In embodiments, another layer of the nonconductive substrate is used to impart properties such as enhanced elasticity or enhanced heat distribution. Referring to Figure 12, the composite material 1200 of this embodiment is in the form of a sheet and includes a layer 1202 of the electrothermal composition applied to a first nonconductive substrate 1204 and sandwiched between the first nonconductive substrate 1204 and a second nonconductive substrate 1206. Figure 13 is a flowchart of an exemplary method 1300 for producing a composite material sheet according to several embodiments. In block 1302, nonconductive substrates of a size and shape suitable for a specific application are provided. As used herein, “provided” means to manufacture, purchase, obtain, or otherwise acquire nonconductive substrates. In block 1304, a heating composition is applied to a nonconductive substrate to form a heating layer in a desired pattern. In embodiments, the pattern of the heating layer is designed to provide a uniform current flow and corresponding uniform heating, as will be described in detail below. In block 1306, a second layer of nonconductive substrate is applied to cover the heating layer of block 1304.

[0090] In the embodiments, the non-conductive substrate includes a polyimide film, a polyimide adhesive tape, a metallized polyimide, or a silicone rubber film. In the embodiments, the non-conductive substrate has desirable mechanical properties such as high dielectric strength at high temperatures, good heat resistance, good elasticity, good thermal conductivity, and flexibility. In the embodiments, the polyimide film is Kapton®, but can be any non-conductive material having desirable properties at temperatures up to about 250°C. The polyimide film and silicone rubber film may require physical and chemical treatments to enhance adhesion of the electrothermal coating, such as surface preparation and roughening with a solvent. In embodiments using Kapton®, sufficient adhesion can be obtained without surface treatment if a suitable binder is used. In embodiments in which two layers of non-conductive substrate containing Kapton® sandwich a layer of the electrothermal composition, an adhesive tape may be used to provide good adhesion between the layers.

[0091] In embodiments where the nonconductive substrate includes silicone rubber, the silicone rubber layer is formed from a thick paste and applied using a film applicator. Since fully cured silicone rubber may not provide good adhesion, the heating composition can be applied when the silicone rubber is partially cured. The heating composition can be applied by spraying onto the substrate or using a CNC plotter. In embodiments, the silicone rubber paste comprises liquid silicone rubber and may further contain one of the common fillers such as silica, titanium oxide, alumina, and carbon black.

[0092] In embodiments where a non-conductive substrate is applied to the surface, a high-temperature adhesive can be applied to the back surface of the non-conductive substrate and cured at 230°C for at least 5 minutes. The use of the adhesive is optional, and in embodiments, it may alternatively be applied to the target surface first. In each curing step, to avoid blistering of the coating, the temperature is increased gradually or in multiple steps, for example, at 60°C for 5 minutes, 120°C for 2 minutes, and 230°C for 20 minutes. The finished product is considered ready for placement on the target surface. The non-conductive substrate can also be cut into panels, similar to panels using the multilayer process described later.

[0093] In embodiments using a non-conductive substrate, conductive wires for the insulating layer and the conductive layer are unnecessary, eliminating the problem of integrating the insulating layer and the conductive layer, and reducing the possibility of dielectric breakdown.

[0094] In the embodiment, the electrothermal coating is applied using a CNC plotter. The electrothermal coating can be drawn on the substrate in a pre-designed complex geometric pattern that imparts the desired electrical resistance, thus enabling the uniform generation of the required amount of thermal energy across the entire panel. The pattern can be designed using software such as SOLIDWORKS®. In this case, since the current is applied directly to the electrothermal coating, there is no need to consider the arrangement of conductive wires to ensure uniform distances between electrodes. Referring to Figures 14 to 17, the electrothermal coatings 1402, 1502, 1602, and 1702 can be applied in specific patterns depending on the shape layout of the associated films 1400, 1500, 1600, and 1700. When a voltage is applied, the current can travel along the path of the electrothermal composition that generates thermal energy.

[0095] Uses of heated clothing In applications where heat is easily lost to the environment, directly directing thermal energy to the microclimate, such as warming the human body, is more efficient and crucial. By embedding heating elements in clothing, thermal energy can be actively generated in the target area, in contrast to conventional clothing that only slows down heat transfer from the body to the surroundings. Actively heating the body with Personal Heated Garments (PHGs) eliminates the need for thick, multi-layered clothing that restricts movement and reduces agility. More importantly, active heating compensates for the inevitable loss of body heat to the surrounding environment.

[0096] The compositions disclosed herein, when applied as layers with a thickness of 100 microns or less and connected to a relatively low-voltage power source such as a 5-12 volt battery or power bank, can generate sufficient heat for PHG applications. The embedded heating compositions, sandwiched between layers of film, can be customized into many shapes or patterns. For applications where the film is in direct contact with human skin, an appropriate grade of silicone rubber can be used. In embodiments, the heating composition can be sandwiched between two layers of film, providing a lightweight (less than 40 mg per square centimeter), soft and flexible product that is both mechanically and electrically resilient after being stretched to 20% of its initial size. The embedded heating composition can function as an independent heating pad or be incorporated into clothing. The thermal energy generated per unit area is determined by the resistance of the composition and the output capacity of the power source. The thermal energy can be easily adjusted with a small controller.

[0097] Without limiting themselves to the foregoing, compositions, composite materials and methods disclosed herein will be further illustrated by the following examples. However, it should be understood that these examples are for illustrative purposes only and are not intended to limit the scope of this disclosure. [Examples]

[0098] Example 1 - Treatment of nanomaterials with coupling agents As an example of this step, acetic acid may be added dropwise to about 50 ml of ethanol while stirring until the pH of the solution reaches about 4. The temperature of the solution may be raised to about 75°C, and the mixture may be stirred under reflux. In a separate container, a 3.2 mM solution of either 3-(2-aminoethylamino)propyl]trimethoxysilane or 3-glycidyloxypropyl)trimethoxysilane may be prepared in ethanol. About 10 ml of this 3.2 mM solution may be added to the main reaction mixture. The main reaction mixture may then be stirred for about 5-10 minutes until its temperature stabilizes. About 10 g of silver flakes with an average particle size range (either about 10-12 microns or 5-9 microns) may be added to the mixture while stirring at about 500 RPM using a magnetic stirrer. Stirring may be continued for about 1 hour, after which the reaction can be stopped by immersing the reaction vessel in a water bath at about 25°C. The solids of the reaction product can be separated by centrifugation at about 1500 RPM. The precipitate can be washed three times with ethanol, once with acetone, and twice with distilled water. Washing involves adding approximately 50 ml of solvent (ethanol, acetone, or water) to the precipitate, dispersing and / or dissolving substantially all components of the precipitate by ultrasonic shaking, and separating the silver flakes from the dissolved components by centrifugation at approximately 1500 RPM. The supernatant can be discarded at each stage of washing and the precipitate can be recovered. After washing, the treated silver flakes can be dried at ambient temperature for at least 24 hours.

[0099] Example 2 - Treatment of nanomaterials with silicone resin intermediates As an example of this step, carboxyl or hydroxyl functionalized multilayer carbon nanotubes can be added to about 150 ml of toluene. This mixture can be stirred with a magnet at room temperature for at least 10 minutes, and then sonicated for at least 20 minutes. This process can be repeated three times. About 10-20 ml of DOWSIL® 3074 (preferred) or DOWSIL® 3037 can be added to the mixture and stirred for at least 10 minutes. This mixture can be sonicated at about 50°C for about 30 minutes and used in the next step without further modification.

[0100] Example 3 - Dispersion of nanomaterials in diluted binder resin As an example of this step, in a preparation procedure that can yield approximately 30 ml of electrothermal composition, approximately 2 g of silver nanowires (average diameter approximately 60 nm to 120 nm and average length approximately 15 to 50 μm) can be partially dispersed in approximately 2.3 ml of ethanol by sonication for approximately 1 minute. Approximately 11.5 ml of single-component or multi-component silicone resin can be added. This resin can be diluted with approximately 11.5 ml to 23 ml of toluene depending on the viscosity requirements. Examples of silicone resins that can be used in this formulation include: DOWSIL® RSN-0805, DOWSIL® RSN-0806, DOWSIL® 2405, and blends of RSN-0805 and RSN-0806 resins having compositions ranging from 20 / 80 wt% (RSN-0805 / RSN-0806) to approximately 80 / 20 wt%. The mixture can be stirred with a magnetic stirrer for about 10 minutes and then sonicated for about 2 minutes. This can be repeated at least four times until the mixture is visually homogeneous. Next, 22 grams of treated silver flakes can be added to the mixture. When DOWSIL® 2405 is used as the binder resin, 0.15 g to 0.3 g of titanium(IV) butoxide can be added as a curing catalyst. The mixture can be stirred and sonicated several more times until the silver flakes are uniformly dispersed. Depending on the storage time, this composition may require sonication (at least 1 minute) and stirring (at least 2 minutes) before application to a surface.

[0101] Example 4 - Dispersion of nanomaterials in a diluted binder resin As an example of this step, approximately 2.5 grams of silver nanowires (average diameter approximately 60 nm to 120 nm, average length approximately 15 to 50 μm) can be first treated at room temperature by multiple cycles of sonication and stirring with approximately 8 ml of ethanol and approximately 40 ml of single-component or multi-component silicone resin. Examples of silicone resins that can be used in this formulation include: DOWSIL® RSN-0805, DOWSIL® RSN-0806, DOWSIL® 2405, and blends of RSN-0805 and RSN-0806 resins having compositions ranging from 20 / 80 wt% (RSN-0805 / RSN-0806) to approximately 80 / 20 wt%. The mixture can be subjected to stirring for approximately 5 minutes and sonication for approximately 5 minutes, and this can be repeated at least three times. Next, approximately 18 grams of surface-treated silver flakes, approximately 18 grams of surface-treated silver nanoparticles, and 40 ml of toluene can be added to the mixture. The mixture can be continuously ultrasonically treated and stirred until a uniform dispersion is achieved. Before application of the final product, the viscosity of the mixture can be adjusted by adding up to approximately 40 ml of toluene.

[0102] Example 5 - Dispersion of nanomaterials in diluted binder resin As an example of this step, approximately 1.5 grams of silver nanowires (average diameter approximately 60 nm to 120 nm, average length approximately 15 to 50 μm) can be partially dispersed in approximately 2.4 ml of ethanol by sonication for approximately 1 minute. Approximately 12 ml of single-component or multi-component silicone resin diluted in approximately 12 ml of toluene can be added. Examples of silicone resins that can be used in this formulation include: DOWSIL® RSN-0805, DOWSIL® RSN-0806, DOWSIL® 2405, and blends of RSN-0805 and RSN-0806 resins having a composition ranging from 20 / 80 wt% (RSN-0805 / RSN-0806) to approximately 80 / 20 wt%. The mixture can be stirred with a magnetic stirrer for approximately 10 minutes and sonicated for approximately 2 minutes. This can be repeated at least four times until the mixture is visually homogeneous. Approximately 11.52 ml of the carbon nanotube dispersion prepared in Step 3 and approximately 22 grams of treated silver flakes were added to the above mixture. When DOWSIL® 2405 is used as the binder resin, approximately 0.15 g to 0.3 g of titanium(IV) butoxide can be optionally added as a curing catalyst. The mixture may be subjected to several more stirrings and sonication until the silver flakes and carbon nanotubes are uniformly dispersed. This procedure yields approximately 40 ml of the electrothermal composition. Depending on the storage time, this composition may require the addition of some solvent, sonication (at least 1 minute), and stirring (at least 2 minutes) before application to a surface.

[0103] Example 6 - Dispersion of nanomaterials in diluted binder resin As an example of this step, to prepare approximately 700 ml of the electrothermal composition, approximately 98 ml of the carbon nanotube dispersion prepared in step 3 can be added to approximately 145 ml of a single-component or multi-component silicone resin diluted with approximately 260 ml of toluene. Examples of silicone resins that can be used in this formulation include: DOWSIL® RSN-0805, DOWSIL® RSN-0806, and blends of RSN-0805 and RSN-0806 resins having a composition ranging from 20 / 80 wt% (RSN-0805 / RSN-0806) to approximately 80 / 20 wt%. The mixture is stirred with an overhead stirrer for approximately 5 minutes, followed by sonication for approximately 15 minutes. This can be repeated at least twice. Approximately 38.25 g of surface-treated silver flakes can be added together with approximately 60 ml of toluene. The mixture is stirred with an overhead stirrer for approximately 5 minutes, followed by sonication for approximately 15 minutes. This can be repeated at least twice. Approximately 6.12 g of carbon black, preferably a highly conductive carbon black such as VULCAN® XCmax® 22, and approximately 40 ml of toluene can be added. At this stage, the paint can be stirred for approximately 5 minutes and subjected to ultrasonic treatment for approximately 5 minutes only once. As with the previous formulations, it is preferable to subject this composition to ultrasonic treatment and stirring before application.

[0104] Example 7 - Dispersion of nanomaterials in diluted binder resin As an example of this step, approximately 2 g of silver nanowires (average diameter approximately 60 nm to 120 nm, average length approximately 15 to 50 μm) can be partially dispersed in approximately 2.5 ml of ethanol by sonication for approximately 1 minute. The partially dispersed nanowires are then treated with approximately 5 to 6 ml of single-component or multi-component silicone resin. Examples of silicone resins that can be used in this formulation include: DOWSIL® RSN-0805, DOWSIL® RSN-0806, and blends of RSN-0805 and RSN-0806 resins having a composition ranging from 20 / 80 wt% (RSN-0805 / RSN-0806) to approximately 80 / 20 wt%. The mixture can be stirred with a magnetic stirrer for approximately 5 minutes, and then sonicated at a temperature of approximately 45 ± 5°C for approximately 4 minutes. This can be repeated at least 4 times until the mixture is visually homogeneous. To maintain the desired temperature and improve homogeneity, the mixture can be diluted with up to approximately 25 ml of toluene. Approximately 20 g to 30 g of silver flakes can be added, and the mixture can be stirred several times and ultrasonically treated until the silver flakes are uniformly dispersed. Approximately 20 g of two-part silicone rubber is added. The ratio of part A to part B of the liquid silicone rubber can be set according to the manufacturer's instructions. Examples of liquid silicone rubber compounds used in this formulation include, but are not limited to, SILASTIC® RBL-9200, SILASTIC® MS-1002, SILASTIC® 9252, and SILASTIC® 9151-200P, all of which have a Shore hardness A of 30 to 60.

[0105] Next, to avoid premature hardening of the elastomer material, the mixture may be vigorously stirred and sonicated at approximately 25°C. This procedure yields approximately 60 ml of expandable electrothermal composition. Depending on the storage time, some solvent addition, sonication (at least 1 minute), and stirring (at least 2 minutes) may be required before applying this composition to a surface.

[0106] While several embodiments have been shown and described, it will be understood by those skilled in the art that various modifications and alterations can be made to these embodiments without altering or departing from their scope, intent, or functionality. The terms and expressions used herein are for illustrative purposes only and are not intended to be limiting, and the use of such terms and expressions is not intended to exclude equivalents of any and all of the features presented and described.

Claims

1. An electrothermal composition comprising a network of conductive nanomaterials and a binding component, wherein the nanomaterials constitute 10% to 80% of the mass of the electrothermal composition, and the electrothermal composition has a conductivity of 0.05 ohms / cm². ２ ~35 ohms / cm ２ An electric heating composition having a resistivity of [value].

2. The nanomaterial constitutes 40% to 70% of the mass of the heating composition, and the heating composition has a capacitance of 0.08 ohms / cm². ２ ~10 ohms / cm ２ The electric heating composition according to claim 1, having a resistivity of the specified value.

3. The electrically heated composition according to claim 1 or 2, wherein the conductive nanomaterial includes nanowires, nanotubes, nanoflakes, nanoparticles, or a combination thereof.

4. The electrically heated composition according to claim 3, wherein the conductive nanomaterial includes the nanowires, and the network of the conductive nanomaterial includes interconnected strands of the nanowires.

5. The electric heating composition according to claim 4, wherein the network of conductive nanomaterials further comprises at least one of the nanoflakes and the nanoparticles.

6. The electric heating composition according to claim 4 or 5, wherein the interconnected strands have an average diameter of about 35 to 250 nm and an average length of about 8 to 60 μm.

7. The electric heating composition according to 6, wherein the interconnected strands have an average diameter of about 55 to 176 nm and an average length of about 14 to 30 μm.

8. The electrically heated composition according to claim 6 or 7, wherein the network of conductive nanomaterials has an average network mesh size of less than 10 nm.

9. The conductive nanomaterial comprises a silver nanomaterial, as described in any one of claims 1 to 8.

10. The electric heating composition according to any one of claims 1 to 9, further comprising at least one carbon component.

11. The electric heating composition according to claim 10, wherein the at least one carbon component comprises at least one of carbon nanotubes, carbon nanofibers, nanographite, and carbon black.

12. The heating element according to any one of claims 1 to 11, wherein the binding component includes a silicone resin.

13. An electric heating panel for applying heat to a surface upon contact with the surface, A first layer containing an electrical insulating material, A second layer comprising the electric heating composition according to any one of claims 1 to 12, wherein the second layer is disposed on the first layer, A third layer including an anode and a cathode arranged in a pattern on the second layer Electric heating panels including

14. The electric heating panel according to claim 13, wherein a layer of thermally conductive adhesive is applied to the side of the first layer distal to the second layer, and the side of the panel containing the thermally conductive adhesive is placed on a removable backing sheet.

15. An electrically heated film sheet for generating heat, A first layer comprising a sheet of non-conductive film, A second layer comprising the electric heating composition according to any one of claims 1 to 12, wherein the second layer is disposed on the first layer and A heat-generating film sheet containing electric heating elements.

16. The electric heating film sheet according to claim 15, further comprising a third layer including a sheet of non-conductive film for covering the second layer.

17. The electric heat generating film sheet according to claim 15 or 16, wherein the sheet of non-conductive film contains silicone.

18. The electric heat generating film sheet according to claim 15 or 16, wherein the sheet of the non-conductive film contains polyimide.

19. A method for manufacturing an electric heating panel for applying heat to a surface upon thermal contact with the surface, Forming a layer of electrical insulating material, Forming a layer of the electric heating composition on the layer of the aforementioned electrical insulating material, Forming an anode and a cathode on a layer of the aforementioned electric heating composition A method that includes this.

20. The manufacturing method according to claim 19, wherein the layer of the electric heating composition comprises silver nanomaterial.

21. A method for manufacturing an electrically heated film sheet for generating heat, To form a first layer of non-conductive film, Forming a layer of the electric heating composition on the first layer and A method that includes this.

22. The method according to claim 21, further comprising forming a second layer of non-conductive film so as to cover the layer of the electric heating composition.

23. The method according to claim 21 or 22, wherein the layer of the electric heating composition comprises silver nanomaterial.

24. A method for preparing a surface for heating using an electric heating composition, To provide a mold made of a non-conductive material having one or more heat transfer surfaces, Applying a layer of the electric heating composition to one or more of the heat transfer surfaces, Applying electrodes to the layer of the electric heating composition A method that includes this.

25. The method according to claim 24, wherein the mold comprises one or more heat transfer surfaces of a conductive material, and the method further comprises applying a layer of an electrically insulating material to the heat transfer surfaces before applying the layer of the electric heating composition.

26. The method according to claim 24 or 25, wherein the layer of the electric heating composition comprises silver nanomaterial.

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