Graphene fiber reinforced flexible heating composite materials, their preparation methods and applications

Abstract

This invention discloses a graphene fiber-reinforced flexible heating composite material, its preparation method, and its applications. The composite material comprises an integrated flexible heating base layer formed by combining a fiber cloth with in-situ grown graphene with a thermoplastic resin. The graphene grows in situ on the fiber surface, forming a continuous and uniform conductive heating network, which, together with the thermoplastic resin matrix, constitutes a non-layered, integral structure. The composite material provided by this invention has a thinner structure, more uniform heating, and high interfacial bonding strength. It also possesses excellent flexibility, high structural strength, weather resistance, and washability, solving the technical pain points of existing flexible heating materials such as uneven heating, poor adhesion, and low structural strength. It can be widely used in industrial equipment heating and de-icing, low-temperature flexible bonding insulation heating, household heating, medical hot compresses, outdoor weather-resistant heating, and electric heating tube insulation, among other fields.

Description

Technical Field

[0001] This invention relates to the field of flexible heating materials technology, and more specifically, to a graphene fiber reinforced flexible heating composite material, its preparation method, and its application in heating devices. Background Technology

[0002] This section provides only background information related to this application to enable those skilled in the art to understand this application more thoroughly and accurately, and it is not necessarily prior art.

[0003] Flexible heating elements are widely used in industrial heat tracing, medical heating, home heating, and outdoor equipment due to their flexibility and ease of fitting. Currently, most flexible heating elements on the market use metal resistance wires or graphene / carbon paste coatings as heating elements, and the substrates are mostly traditional materials such as silicone rubber and ordinary fabrics.

[0004] However, in practical applications, flexible heating elements currently suffer from irreversible technical defects, making it difficult to meet the usage requirements of high-end application scenarios and harsh environments: For example, metal wire heating elements have poor flexibility and are prone to breakage after bending. The breakage of a single wire can lead to the failure of the entire element, resulting in low reliability. Furthermore, the heating temperature distribution is uneven, with obvious local hot and cold spots, leading to poor thermal comfort.

[0005] For example, in the case of coated graphene / carbon paste heating elements, the heating layer is attached to the surface of the substrate through a coating process. This is a physical contact and the bonding force with the substrate is weak. After long-term use or repeated bending, the coating is prone to peeling, cracking, and flaking, which can lead to resistance drift, severe attenuation of heating performance, and even safety hazards such as arcing.

[0006] Existing products generally struggle to balance flexibility, high structural strength, and chemical corrosion resistance. For example, silicone rubber substrates have low strength and are easily punctured; fabric substrates are not washable and have poor weather resistance. This makes existing flexible heating elements unsuitable for industrial or outdoor environments requiring high strength, washability, and corrosion resistance. While traditional fiberglass (glass fiber reinforced thermosetting resin) possesses high strength and corrosion resistance, its matrix is ​​a thermosetting resin (such as epoxy resin or unsaturated polyester), which, after curing, is hard and brittle with no flexibility, making it impossible to bend and fit onto curved surfaces, and thus unsuitable as a substrate for flexible heating devices.

[0007] In summary, existing technologies lack an integrated flexible heating material that can simultaneously meet the requirements of "uniform and stable heating, high structural strength, good flexibility, and strong interfacial bonding without detachment." The market urgently needs technological breakthroughs to address these pain points. Summary of the Invention

[0008] The purpose of this invention is to provide a graphene fiber reinforced flexible heating composite material and its preparation method, aiming to solve the technical problems of uneven heating, low structural strength, poor interfacial bonding, and poor resistance to bending and cleaning of existing flexible heating materials.

[0009] To achieve the above objectives, the technical solutions adopted in the embodiments of the present invention are as follows: In a first aspect, the present invention provides a graphene fiber-reinforced flexible heating composite material, comprising: The flexible heating substrate is composed of a fiber cloth with graphene grown in situ and a thermoplastic resin. The graphene forms a continuous and uniform conductive heating network on the surface of the fiber cloth and in the gaps between the fibers.

[0010] Secondly, the present invention provides a method for preparing the graphene fiber reinforced flexible heating composite material as described above, comprising the following steps: Provide a fiber cloth that has undergone demolding and washing pretreatment; The fiber cloth was soaked in a carbon source precursor solution and graphene was grown in situ on the fiber surface by scanning electromagnetic induction ultrafast quenching technology to obtain graphene fiber cloth. The graphene fiber cloth is integrally composite molded using thermoplastic resin through hot melt impregnation and molding processes to obtain the graphene fiber reinforced flexible heating composite material.

[0011] Thirdly, this invention provides innovative applications of the above-mentioned graphene fiber-reinforced flexible heating composite material in different scenarios: As mentioned above, the application of graphene fiber reinforced flexible heating composite material in heating elements for industrial equipment housings, wherein the thermoplastic resin is polyphenylene sulfide.

[0012] As mentioned above, in the application of graphene fiber reinforced flexible heating composite material in low-temperature flexible bonding heating sheets, the thermoplastic resin is ethylene-vinyl acetate copolymer.

[0013] As mentioned above, in the application of graphene fiber reinforced flexible heating composite material in household whole-house universal heating elements, the thermoplastic resin is linear low-density polyethylene and polystyrene.

[0014] As mentioned above, in the application of graphene fiber reinforced flexible heating composite material in medical heat therapy pads, the thermoplastic resin is a thermoplastic polyester elastomer.

[0015] As mentioned above, in the application of graphene fiber reinforced flexible heating composite material in outdoor camping weather-resistant heating plates, the thermoplastic resin is a low-temperature resistant modified ethylene-vinyl acetate copolymer.

[0016] As mentioned above, in the application of graphene fiber reinforced flexible heating composite material in electric heating tube sleeve, the thermoplastic resin is a thermoplastic elastomer, and the flexible heating base layer is also composited with a rubber protective layer and / or a heat insulation layer on the outside.

[0017] The following benefits can be obtained by adopting this technical solution: First, by growing graphene in situ on the fiber surface, a strong chemical bond is formed between the heating element and the reinforcement at the microscale, creating an inseparable whole. This fundamentally solves the problems of heating layer detachment, cracking, and performance degradation. When combined with thermoplastic resin, it forms a seamless whole with extremely high reliability. Second, graphene forms continuous and interconnected conductive pathways within the fiber network. When energized, the entire matrix experiences uniform Joule heating, completely eliminating localized hot and cold spots, resulting in extremely high electrothermal conversion efficiency. Finally, the graphene is grown using scanning electromagnetic induction ultrafast quenching technology, which is highly efficient, energy-efficient, and environmentally friendly. Subsequent use of mature composite material molding processes is simple, controllable, and easy for large-scale industrial production.

[0018] This patent achieves an unexpected and beneficial effect of synergistic flexibility and high structural strength, stemming from the creative control of micro-nano interface structures: Graphene grown in situ on the fiber surface using scanning electromagnetic induction ultrafast quenching technology forms a chemical bond with the fiber substrate in the form of a nanofilm, rather than a physical attachment. The bonding strength reaches level 5B, and the graphene film is firmly anchored to the fiber surface without falling off or peeling off.

[0019] In-situ grown graphene possesses a complete two-dimensional six-membered ring lattice structure. The residual oxygen-containing functional groups in the lattice can form hydrogen bonds, van der Waals forces, and chemical anchoring with the thermoplastic resin molecular chains, significantly improving the resin's wettability and interfacial bonding to the graphene fiber cloth. In contrast, physically coated graphene powder slurry lacks a continuous lattice and active functional groups, resulting in loosely packed materials with extremely poor interfacial bonding. This "fiber-graphene-resin" three-in-one micro-nano interface structure enables the composite material to maintain flexibility while achieving excellent tensile strength and structural stability. After repeated washing, bending, and stretching, the heating network remains undamaged, and the resistance does not drift, achieving long-term stable uniform heating.

[0020] Additional aspects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Attached Figure Description

[0021] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0022] Figure 1 A schematic diagram of the preparation process of graphene fiber reinforced flexible heating composite material; Figure 2 Photos of actual products after graphene has been grown on the surfaces of different ceramic fibers; Figure 3 Photo of a graphene-quartz fiber reinforced flexible (TPU) thermal composite material; Figure 4 Machine-washable photo of graphene-quartz fiber reinforced flexible (TPU) heating composite material; Figure 5 Photo of a graphene-quartz fiber-reinforced flexible (silicone) heating composite material; Figure 6 Photo of a graphene-quartz fiber cloth-reinforced flexible (rubber) heating composite material; Figure 7 Photo of a graphene-quartz fiber reinforced flexible (PI) heating composite material; Figure 8 Photo of a graphene-basalt fiber reinforced flexible (TPU) thermal composite material; Figure 9 Infrared thermograph of graphene basalt fiber reinforced flexible (TPU) heating composite material; Figure 10 Photo of a graphene-quartz fiber reinforced flexible (TPU) heating element; Figure 11 Infrared thermal image of a graphene-quartz fiber reinforced flexible (TPU) heating tube; Figure 12 Tensile strength curves of flexible heating composites reinforced with different graphene ceramic fiber cloths. Detailed Implementation

[0023] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0024] Example 1: The graphene fiber-reinforced flexible heating composite material provided in this embodiment includes a flexible heating base layer. This flexible heating base layer is composed of a fiber cloth with in-situ grown graphene and a thermoplastic resin.

[0025] The fiber cloth serves as the reinforcing skeleton, and its material can be any combination of one or more of the following: glass fiber cloth, quartz fiber cloth, alumina fiber cloth, silicon carbide fiber cloth, basalt fiber cloth, high-silica fiber cloth, mullite fiber cloth, zirconium oxide fiber cloth, silicon nitride fiber cloth, and aluminosilicate fiber cloth. This embodiment uses quartz fiber cloth as an example, with a thickness of 0.1~0.3mm and an areal density of 100~300 g / m³. 2 The diameter of a single fiber is 1~5 μm.

[0026] Graphene is grown directly on the surface of the fiber cloth and in the interfiber spaces using in-situ growth technology, forming a continuous conductive and heating network. This growth method allows for a strong interfacial bond between graphene and the fiber surface through chemical bonding. Tested according to ASTM D3359 standard, the interfacial bond strength reaches level 5B. This strong interfacial bond originates from the chemical bonding between the in-situ grown graphene and the fiber, as well as the efficient wetting and anchoring of the graphene's two-dimensional six-membered ring structure with the resin. Tensile testing shows that the tensile strength of the composite material is more than 300% higher than that of traditional coated heating elements. After repeated washing for 30 minutes and bending 100,000 times, the structure showed no cracking, the heating layer did not detach, the heating uniformity remained unchanged, and the temperature difference remained ≤±2℃. This performance is beyond the expectations of those skilled in the art. Depending on the application requirements, the sheet resistivity of the fiber cloth with in-situ grown graphene can be adjusted within the range of 50 Ω•sq⁻¹ to 5000 Ω•sq⁻¹. The graphene heating network is embedded inside the composite material structure, forming a seamless whole with the fiber reinforcement and resin matrix. It integrates heating, reinforcement, protection and insulation functions, fundamentally solving the problems of easy peeling and cracking of traditional coated heating layers.

[0027] Thermoplastic resin, as the matrix material, permeates and encapsulates the entire fiber network, providing protection, insulation, and flexibility. Thermoplastic resins can be selected from any one or more combinations of polyphenylene sulfide, thermoplastic polyurethane, ethylene-vinyl acetate copolymer, polyethylene, polypropylene, linear low-density polyethylene, thermoplastic polyester elastomer, thermoplastic polyolefin, polyetheretherketone, polyimide, nylon 6, polycarbonate, thermoplastic vulcanized rubber, or silicone. The selection of thermoplastic resins gives the composite material excellent flexibility at room temperature, allowing for repeated bending without damage, while also providing good mechanical support and resistance to environmental corrosion. The overall thickness of the flexible heating base layer can be adjusted within the range of 0.05 mm to 5 mm as needed.

[0028] Furthermore, a patterned electrode layer is disposed on at least one surface of the flexible heating substrate. The patterned electrode layer is used to uniformly feed power to the graphene conductive heating network, ensuring a uniform power density distribution across the entire heating surface. The patterned electrode layer can be made of highly conductive metal foil (such as copper foil or silver foil) or conductive ink / silver paste, and formed into strip electrodes or interdigitated electrodes through printing or lamination processes. The electrode width is preferably 0.1 mm to 20 mm, and the spacing between adjacent electrodes is preferably 5 mm to 50 mm.

[0029] Furthermore, one or more of the following layers—rubber, silicone, and insulation—are further laminated onto one or both sides of the flexible heating substrate to enhance the composite material's protective properties, weather resistance, or insulation performance. The rubber layer provides excellent mechanical cushioning, waterproof sealing, and chemical corrosion resistance, effectively protecting the internal heating network from external impacts and environmental erosion, making it particularly suitable for industrial equipment and harsh outdoor environments. The silicone layer combines flexibility and biocompatibility, improving skin-friendly feel and user comfort in medical heating and wearable applications. The insulation layer (such as aerogel felt or polyurethane foam) significantly reduces heat loss to non-working surfaces, improving heat utilization efficiency and reducing energy consumption, making it particularly suitable for applications requiring directional heat transfer, such as electric heating tube sleeves and pipe tracing. These functional layers are integrated with the flexible heating substrate through hot pressing or bonding processes, preserving the substrate's original flexibility and heating uniformity while expanding the product's environmental adaptability as needed, enabling the composite material of this invention to cover a wider range of application requirements.

[0030] Example 2: The preparation method of graphene fiber reinforced flexible heating composite material provided in this embodiment includes the following steps: Step S1: Provide a fiber cloth that has undergone demolding and washing pretreatment.

[0031] Commercial fiber cloths typically contain organic substances such as sizing agents on their surface, which need to be removed. Taking quartz fiber cloth as an example, it is placed in a high-temperature furnace and heated to 450℃~550℃ in an air atmosphere, held at that temperature for 1~3 hours, and then naturally cooled to room temperature for demolding. After demolding, it is ultrasonically cleaned sequentially with acetone, anhydrous ethanol, and deionized water (40~50 kHz), with each cleaning time being 15~30 minutes. After each cleaning step, it is vacuum dried at 80℃~100℃ for 30 minutes to thoroughly remove surface residues and moisture, exposing a clean fiber surface and providing favorable nucleation sites for in-situ graphene growth.

[0032] Step S2: The fiber cloth is soaked in a carbon source precursor solution and graphene is grown in situ on the fiber surface by scanning electromagnetic induction ultrafast quenching technology to obtain graphene fiber cloth.

[0033] The pretreated fiber cloth is completely immersed in a carbon source precursor solution. The carbon source precursor can be a solution of phenolic resin, polyacrylonitrile, asphalt, etc., with a preferred concentration of 5 wt% to 20 wt%. The solvent is a volatile organic solvent such as ethanol or acetone. The immersion time is 20 to 60 minutes to allow the carbon source to be fully adsorbed onto the fiber surface. After removal, it is air-dried naturally or dried at a low temperature until surface dry.

[0034] Fibers impregnated with carbon source precursors are arranged in a "sandwich" oxygen-deficient structure composed of a graphite plate and a glass plate (with the fiber cloth in the middle), and heated using a scanning electromagnetic induction heating device. The heating temperature is 1000℃~1500℃, and the heating method is high-frequency induction scanning heating, with the preferred current frequency being 50kHz~200kHz. Through the scanning movement of the induction coil, the fiber cloth is rapidly heated to the target temperature and maintained for several seconds. The carbon source precursor undergoes instantaneous pyrolysis at high temperature and reconstructs to form graphene. Subsequently, the material temperature is reduced to room temperature by natural cooling, completing the quenching process. By adjusting the scanning speed, heating power, and precursor concentration, the growth thickness and density of graphene can be precisely controlled, thereby adjusting the sheet resistivity of the graphene fiber cloth within the range of 50~5000 Ω•sq⁻¹.

[0035] The method utilizes electromagnetic induction to heat the fiber cloth itself, resulting in high energy efficiency; the heating and cooling rates are extremely fast, which is conducive to the formation of high-quality graphene; the scanning method can process large-area continuous materials, making it suitable for industrial production.

[0036] Step S3: Form a patterned electrode layer on at least one surface of the graphene fiber cloth.

[0037] This step is performed when fabricating composite materials with patterned electrodes. Screen printing can be used: First, purchase a high-precision screen stencil with a mesh count of 300-400 according to design requirements. Then, uniformly apply the prepared conductive silver paste to the surface of the screen stencil and scrape it across the stencil at a 45° angle and uniform speed using a squeegee, transferring the conductive silver paste through the mesh to the surface of the graphene quartz fiber cloth, forming the pre-defined conductive path pattern. Alternatively, gravure printing or lamination can be used to create highly conductive metal foil or conductive ink / silver paste on the surface of the graphene fiber cloth, forming strip or interdigitated electrode patterns. After printing or lamination, cure at 120℃-180℃ for 20-60 minutes to ensure good electrical contact and mechanical bonding between the electrode layer and the graphene fiber cloth.

[0038] Step S4: Using thermoplastic resin, graphene fiber cloth is integrally composite molded through hot melt impregnation and molding processes to obtain graphene fiber reinforced flexible heating composite material.

[0039] After thoroughly drying the selected thermoplastic resin granules at 60℃~120℃, heat them to above their melting temperature (usually 180℃~200℃). Completely immerse the graphene fiber cloth (including the electrode layer) in the molten resin and hold for 3~5 minutes to allow the resin to fully penetrate and fill the fiber gaps. Then transfer the impregnated blank to a flat vulcanizing mold preheated to the appropriate temperature (e.g., 170~180℃), close the mold, and apply a molding pressure of 5MPa~10MPa for 5~10 minutes. During the holding pressure period, perform 1~2 rapid pressure releases to eliminate internal air bubbles and improve material density. After the holding pressure is completed, maintain the pressure and allow the mold to cool naturally to room temperature or slightly above room temperature before releasing the pressure and demolding. Finally, the demolded composite material can be subjected to low-temperature annealing treatment at a temperature of 60℃~100℃ for 1~4 hours to eliminate internal stress and further improve dimensional stability, ultimately obtaining graphene quartz fiber cloth reinforced flexible (TPU) heating composite material.

[0040] Example 3: This embodiment demonstrates the application of the composite material shown in Example 1 in the heating element of an industrial equipment housing, wherein the thermoplastic resin is polyphenylene sulfide (PPS).

[0041] Raw materials: Quartz fiber cloth (0.2 mm thick); PPS granules; phenolic resin ethanol solution (10 wt%); nickel-plated copper foil (0.1 mm thick).

[0042] Preparation: Following the method in Example 2, the surface resistivity of the graphene fiber cloth was controlled to be 800~1500 Ω•sq⁻¹. The electrodes were made of copper foil strips with a width of 2 mm and a spacing of 20 mm. The PPS melting temperature was 290℃, the impregnation time was 5 minutes, and the molding temperature was 180℃, the pressure was 8 MPa, and the holding time was 8 minutes. The product thickness was approximately 2 mm.

[0043] Performance tests: Insulation resistance ≥1000MΩ, temperature resistance -40℃~220℃, salt spray resistance for 500 hours without corrosion, IPX6 waterproof, 50,000 bending cycles without cracking. Example 4: This embodiment demonstrates the application of the composite material shown in Example 1 in a low-temperature flexible bonding heating sheet, wherein the thermoplastic resin is selected as ethylene-vinyl acetate copolymer (EVA).

[0044] Raw materials: fiberglass cloth (0.15mm thick); EVA; phenolic resin ethanol solution (10 wt%); copper tape (0.05mm thick).

[0045] Preparation: Following the method in Example 2, the surface resistivity of the graphene fiber cloth was 2000~2500 Ω•sq⁻¹. The electrodes were made of copper tape with a width of 3 mm and a spacing of 10 mm. The EVA melting temperature was 150℃, and the impregnation time was 5 minutes. The molding temperature was 130℃, the pressure was 3 MPa, and the holding time was 15 minutes. The product thickness was approximately 0.5 mm.

[0046] Performance tests: No cracking at -20℃, bending radius ≤5mm, electrothermal conversion efficiency >98%, temperature difference ≤1.0℃.

[0047] Example 5: This embodiment demonstrates the application of the composite material shown in Example 1 in a universal heating element for home use, wherein the thermoplastic resin is a mixture of linear low-density polyethylene (LLDPE) and polystyrene (PS) in a mass ratio of 7:3.

[0048] Raw materials: Quartz fiber cloth (thickness 0.25mm); LLDPE / PS mixed resin; phenolic resin ethanol solution (10wt%); copper tape (thickness 0.1mm).

[0049] Preparation: Following the method in Example 2, the surface resistivity of the graphene fiber cloth was 2500~3000 Ω•sq⁻¹. The electrodes were made of copper tape with a width of 5 mm and a spacing of 15 mm. The resin melting temperature was 180℃, and the impregnation time was 5 minutes. The molding temperature was 160℃, the pressure was 5 MPa, and the holding time was 10 minutes. The product thickness was approximately 1 mm.

[0050] Performance testing: Easy to clean and washable ≥50 times, wrinkle-free when folded, resistant to weak acids and alkalis, operating temperature 30~70℃, IPX4 waterproof.

[0051] Example 6: This embodiment demonstrates the application of the composite material shown in Example 1 in a medical hot compress heating pad, wherein the thermoplastic resin is selected as thermoplastic polyurethane (TPU).

[0052] Raw materials: Quartz fiber cloth (thickness 0.1mm); TPU; phenolic resin ethanol solution (10 wt%); silver foil (thickness 0.03mm).

[0053] Preparation: Following the method in Example 2, the surface resistivity of the graphene fiber cloth was 1500~2000 Ω•sq⁻¹. The electrodes were made of silver foil with a width of 5 mm and a spacing of 15 mm. The TPEE melting temperature was 200℃, and the impregnation time was 3 minutes. The molding temperature was 180℃, the pressure was 5 MPa, and the holding time was 8 minutes. The product thickness was approximately 0.3 mm.

[0054] Performance testing: Biocompatibility meets standards, skin-friendly and non-irritating, resistant to sweat corrosion, washable and reusable, temperature difference ≤1.2℃, no local hot spots.

[0055] Example 7: This embodiment demonstrates the application of the composite material shown in Example 1 in an outdoor camping weather-resistant heating plate, wherein the thermoplastic resin is a low-temperature resistant modified ethylene-vinyl acetate copolymer (EVA, VA content 40%).

[0056] Raw materials: basalt fiber cloth (thickness 0.2mm); low-temperature resistant modified EVA; phenolic resin ethanol solution (10 wt%); tin-plated copper foil (thickness 0.08mm).

[0057] Preparation: Following the method in Example 2, the surface resistivity of the graphene fiber cloth was 1000~1200 Ω•sq⁻¹. The electrodes were made of tin-plated copper foil with a width of 8 mm and a spacing of 25 mm. The EVA melting temperature was 150°C, the impregnation time was 5 minutes, and the molding temperature was 130°C, the pressure was 3 MPa, and the holding time was 15 minutes. The product thickness was approximately 0.8 mm.

[0058] Performance testing: -40℃ to 10℃ in 30 seconds, stabilizes at 25℃ in 10 minutes, UV aging resistant, IPX7 waterproof, compatible with car / power bank.

[0059] Example 8: This embodiment demonstrates the application of the composite material shown in Embodiment 1 in an electric heating tube sleeve, wherein the thermoplastic resin is selected as thermoplastic polyurethane (TPU), and the outer side of the base layer is composited with a rubber protective layer and an insulation layer.

[0060] Raw materials: Quartz fiber cloth (0.1mm thick); TPU; Phenolic resin ethanol solution (10 wt%); Conductive silver paste; Silicone rubber raw material; Aerogel insulation felt (3mm thick).

[0061] Preparation: Following the method in Example 2, the surface resistivity of the graphene fiber cloth was 300~800 Ω•sq⁻¹. Electrodes were formed using screen-printed silver paste to create interdigitated electrodes with a width of 1 mm and a spacing of 10 mm. TPU was melted at 195°C for 3 minutes, molded at 180°C, pressure of 5 MPa, and held for 8 minutes to obtain a 0.3 mm thick heating inner layer. An outer layer was then laminated with a 0.2 mm silicone rubber protective layer (hot-pressed at 170°C) and a 3 mm aerogel insulation felt.

[0062] Performance testing: Temperature resistance -60℃~260℃, ultra-thin thickness, resistance change <3% after 100,000 bends, stable performance after 5000 hours of continuous operation.

[0063] Comparative Example 1: Traditional metal wire heating element This comparative example uses a commercially available silicone rubber wire heating pad (100mm×100mm, 12V / 10W) as the test sample. To evaluate the heating performance of the traditional wire heating pad, this study used infrared thermal imaging technology to test its surface temperature distribution. During the test, the heating pad was placed at room temperature (25℃), and after being powered on until thermal equilibrium was reached, the difference between its highest and lowest surface temperatures was recorded. The test results showed that the traditional wire heating pad had a heating temperature difference of 12.5℃ and obvious hot spots, indicating that its surface temperature distribution was significantly uneven. The heating pad was fixed on a dedicated bending test device and repeatedly bent at a frequency of 30 times per minute, with each bending angle being 90°. The experimental results showed that the traditional wire heating pad failed after 5000 bends due to wire breakage, indicating insufficient mechanical reliability. The heating pad was completely immersed in deionized water for 24 hours, and then its insulation resistance value was measured using an insulation resistance tester. Experimental results show that the insulation resistance of traditional metal wire heating elements drops to <1MΩ after immersion in water, which is far below the safety standard.

[0064] Comparative Example 2: Coated Graphene Heating Sheet This comparative example uses a commercially available PET-based graphene-coated heating element (100mm×100mm, 5V) as the test sample. Test results show: adhesion is ASTM 3B, with peeling at the crossed edges, indicating insufficient bonding strength between the coating and the substrate; after 20,000 bends, the coating cracks at the creases, with a 50% increase in local resistance, indicating that the graphene coating is prone to microstructural damage under repeated mechanical stress, leading to increased resistance; after 10 machine washes, the coating peels off, indicating poor water resistance.

[0065] As can be seen from the comparison of the above examples, the embodiments of the present invention exhibit significantly better overall performance than the prior art in different application scenarios, especially in terms of high interface bonding strength, excellent heat generation uniformity and long service life.

[0066] It should be noted that in the description of this invention, the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," and "circumferential" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0067] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this invention, "a plurality of" means two or more, unless otherwise explicitly specified.

[0068] In this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0069] In this invention, unless otherwise explicitly specified and limited, "above" or "below" the second feature can mean that the first feature is in direct contact with the second feature, or that the first feature is in indirect contact with the second feature through an intermediate medium. Furthermore, "above," "over," and "on top" of the second feature can mean that the first feature is directly above or diagonally above the second feature, or simply that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature can mean that the first feature is directly below or diagonally below the second feature, or simply that the first feature is at a lower horizontal level than the second feature.

[0070] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0071] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention.

[0072] For those skilled in the art, various changes and modifications will undoubtedly be apparent after reading the above description. Therefore, the appended claims should be construed as covering all changes and modifications that encompass the true intent and scope of the invention. Any and all equivalent scope and content within the scope of the claims should be considered to remain within the intent and scope of the invention.

Claims

1. A graphene fiber reinforced flexible heating composite material, characterized in that, include: The flexible heating substrate is composed of a fiber cloth with graphene grown in situ and a thermoplastic resin. The graphene forms a continuous and uniform conductive heating network on the surface of the fiber cloth and in the gaps between the fibers.

2. The graphene fiber reinforced flexible heating composite material according to claim 1, characterized in that, The fiber cloth includes any one or more combinations of glass fiber cloth, quartz fiber cloth, alumina fiber cloth, silicon carbide fiber cloth, basalt fiber cloth, high silica fiber cloth, mullite fiber cloth, zirconium oxide fiber cloth, silicon nitride fiber cloth, and aluminum silicate fiber cloth.

3. The graphene fiber reinforced flexible heating composite material according to claim 1, characterized in that, The thermoplastic resin includes at least one or more combinations of polyphenylene sulfide, thermoplastic polyurethane, ethylene-vinyl acetate copolymer, polyethylene, polypropylene, linear low-density polyethylene, thermoplastic polyester elastomer, thermoplastic polyolefin, polyetheretherketone, polyimide, nylon 6, polycarbonate, thermoplastic vulcanized rubber, and silicone.

4. The graphene fiber reinforced flexible heating composite material according to claim 1, characterized in that, It also includes a patterned electrode layer disposed on at least one surface of the flexible heating substrate for uniformly feeding power to the conductive heating network.

5. The graphene fiber reinforced flexible heating composite material according to claim 4, characterized in that, The patterned electrode layer is a strip electrode or interdigitated electrode formed by printing or bonding processes using highly conductive metal foil or conductive ink / silver paste.

6. The graphene fiber reinforced flexible heating composite material according to claim 5, characterized in that, The width of the strip electrode or interdigitated electrode is 0.1 mm to 20 mm, and the spacing between adjacent electrodes is 5 mm to 50 mm.

7. The graphene fiber reinforced flexible heating composite material according to claim 1, characterized in that, The sheet resistivity of the fiber cloth in which graphene is grown in situ is 50 Ω·sq⁻¹~5000 Ω·sq⁻¹.

8. The graphene fiber reinforced flexible heating composite material according to claim 1, characterized in that, The overall thickness of the flexible heating substrate is 0.05 mm to 5 mm.

9. The graphene fiber reinforced flexible heating composite material according to claim 1, characterized in that, The flexible heating base layer is further laminated with one or more of the following: a rubber layer, a silicone layer, and a heat insulation layer, on one or both sides.

10. A method for preparing a graphene fiber reinforced flexible heating composite material as described in any one of claims 1 to 9, characterized in that, Includes the following steps: Provide a fiber cloth that has undergone demolding and washing pretreatment; The fiber cloth was soaked in a carbon source precursor solution and graphene was grown in situ on the fiber surface by scanning electromagnetic induction ultrafast quenching technology to obtain graphene fiber cloth. The graphene fiber cloth is integrally composite molded using thermoplastic resin through hot melt impregnation and molding processes to obtain the graphene fiber reinforced flexible heating composite material.

11. The preparation method according to claim 10, characterized in that, The heating temperature of the scanning electromagnetic induction ultrafast quenching technology is 1000℃~1500℃, and the heating method is high-frequency induction scanning heating.

12. The preparation method according to claim 11, characterized in that, The process parameters for hot melt impregnation and molding are as follows: impregnation and molding temperature is 150℃~220℃, molding pressure is 1 MPa~15 MPa, and holding time is 3 min~15 min.

13. The application of the graphene fiber reinforced flexible heating composite material as described in any one of claims 1 to 9 in the heating element of the outer shell of industrial equipment, wherein the thermoplastic resin is polyphenylene sulfide.

14. The application of the graphene fiber reinforced flexible heating composite material as described in any one of claims 1 to 9 in a low-temperature flexible bonding heating sheet, wherein the thermoplastic resin is an ethylene-vinyl acetate copolymer.

15. The application of the graphene fiber reinforced flexible heating composite material as described in any one of claims 1 to 9 in a universal heating element for whole-house use, wherein the thermoplastic resin is linear low-density polyethylene and polystyrene.

16. The application of the graphene fiber reinforced flexible heating composite material as described in any one of claims 1 to 9 in a medical heat therapy heating pad, wherein the thermoplastic resin is thermoplastic polyurethane or silicone.

17. The application of the graphene fiber reinforced flexible heating composite material as described in any one of claims 1 to 9 in outdoor camping weather-resistant heating sheets, wherein the thermoplastic resin is a low-temperature resistant modified ethylene-vinyl acetate copolymer.

18. The application of the graphene fiber reinforced flexible heating composite material as described in any one of claims 1 to 9 in an electric heating tube sleeve, wherein the thermoplastic resin is a thermoplastic elastomer.

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