Heated film, method of making the same, heating apparatus, and vehicle

Abstract

The application provides a heating film and a preparation method thereof, a heating device and a vehicle. The heating film comprises a graphene film and a gradient radiation coating on the surface of the graphene film. The gradient radiation coating comprises a bottom layer, an intermediate layer and a surface layer in contact with the graphene surface. The resin matrix mass fraction of the bottom layer is greater than that of the intermediate layer, and the resin matrix mass fraction of the intermediate layer is greater than that of the surface layer. The boron nitride mass fraction of the bottom layer is greater than that of the intermediate layer, and the boron nitride mass fraction of the intermediate layer is greater than that of the surface layer. The mass fraction of the infrared radiation material of the bottom layer is less than that of the intermediate layer, and the mass fraction of the infrared radiation material of the intermediate layer is less than that of the surface layer. The bottom layer focuses on adhesion and heat conduction, the intermediate layer considers heat conduction and radiation, and the surface layer maximizes radiation efficiency. The infrared emissivity of the heating film is improved through the design of the gradient radiation coating.

Description

Technical Field

[0001] This application relates to the field of heat dissipation materials, and more particularly to a heating film and its preparation method, heating equipment, and vehicle. Background Technology

[0002] Existing car seats are generally equipped with seat heating and ventilation functions. The heating principle is that the seat heating module controls the current of the heating pad, and the heating pad generates heat, making passengers feel warmer and more comfortable when traveling in cold weather.

[0003] Traditional graphene heating pads for seats use resin and graphene powder as the heating element. Over time, the resin ages, increasing resistance and lowering the heating temperature. Severe resin aging can even cause breakage and sparking, leading to seat ablation and compromising passenger safety. Furthermore, the heating pad must maintain a seat surface temperature of at least 35°C after 5 minutes of heating under ambient temperature conditions of -20°C. However, conventional graphene heating pads often fail to meet this requirement due to their low infrared emission efficiency.

[0004] Currently, the common solution is to increase the heating power and current, but this increases control costs and accelerates the aging of the heating pad. Other improvements include coating the resistance wire with graphene oxide to impart infrared light emission, thereby improving electrothermal conversion efficiency. However, the infrared emission efficiency of this solution still falls short of requirements. Still other improvements involve treating the high-temperature reduced graphene film with plasma followed by oxidation with a strong oxidant to obtain a graphene film with high infrared emissivity. However, this technique requires complex equipment and is complicated to operate.

[0005] Therefore, improving the infrared emission efficiency of graphene heating films is an urgent problem to be solved. Summary of the Invention

[0006] This application provides a heating film and its preparation method, heating equipment and vehicle, for improving the infrared emission efficiency of graphene heating films.

[0007] In a first aspect, this application provides a heating film, comprising: a graphene film and a gradient radiation coating on the surface of the graphene film; the gradient radiation coating includes a bottom layer in contact with the graphene surface, an intermediate layer disposed on the bottom layer, and a surface layer disposed on the intermediate layer;

[0008] The resin matrix of the bottom layer has a greater mass percentage than the resin matrix of the intermediate layer, and the resin matrix of the intermediate layer has a greater mass percentage than the resin matrix of the top layer.

[0009] The boron nitride mass fraction of the bottom layer is greater than that of the intermediate layer, and the boron nitride mass fraction of the intermediate layer is greater than that of the surface layer.

[0010] The mass fraction of the infrared radiation material in the bottom layer is less than that in the middle layer, and the mass fraction of the infrared radiation material in the middle layer is less than that in the surface layer.

[0011] Furthermore, the bottom layer comprises 25-35 parts of resin matrix, 15-25 parts of boron nitride, and 5-10 parts of graphene nanosheets;

[0012] The intermediate layer comprises 18-25 parts of resin matrix, 8-15 parts of boron nitride, 3-8 parts of graphene nanosheets, and 8-15 parts of carbon black.

[0013] The surface layer comprises 10-18 parts of resin matrix, 2-5 parts of boron nitride, 5-12 parts of graphene nanosheets, and 10-20 parts of carbon black.

[0014] Furthermore, the bottom layer and the intermediate layer are connected by covalent bonds formed by a silane coupling agent.

[0015] Furthermore, the infrared radiation material of the intermediate layer includes graphene nanosheets and / or carbon black.

[0016] Furthermore, the thickness of the bottom layer is 3-5 μm, the thickness of the intermediate layer is 5-8 μm, and the thickness of the surface layer is 2-5 μm.

[0017] Furthermore, the resin matrix is ​​acrylic resin or polyurethane;

[0018] And / or, the sheet resistance of the graphene film is 40-60 mΩ / □.

[0019] Secondly, this application provides a method for preparing a heating film, comprising the following steps:

[0020] A first slurry is coated on the surface of a graphene film and then dried to obtain a first intermediate product.

[0021] A second slurry is coated onto the surface of the first intermediate product and then dried to obtain the second intermediate product.

[0022] A heating film is obtained by coating the surface of the second intermediate product with a third slurry and then drying it.

[0023] The resin matrix mass fraction of the first slurry is greater than that of the second slurry, and the resin matrix mass fraction of the second slurry is greater than that of the third slurry.

[0024] The boron nitride mass fraction of the first slurry is greater than that of the second slurry, and the boron nitride mass fraction of the second slurry is greater than that of the third slurry.

[0025] The mass fraction of infrared radiating material in the first slurry is less than the mass fraction of infrared radiating material in the second slurry, and the mass fraction of infrared radiating material in the second slurry is less than the mass fraction of infrared radiating material in the third slurry.

[0026] Furthermore, the first slurry comprises 25-35 parts of resin matrix, 15-25 parts of boron nitride, 5-10 parts of graphene nanosheets, 1-3 parts of silane coupling agent, 1-2 parts of dispersant, and 40-60 parts of deionized water.

[0027] The second slurry comprises 18-25 parts of resin matrix, 8-15 parts of carbon black, 3-8 parts of graphene nanosheets, 8-15 parts of boron nitride, 1-3 parts of dispersant, and 45-65 parts of deionized water;

[0028] The third slurry comprises 10-18 parts of resin matrix, 10-20 parts of carbon black, 5-12 parts of graphene nanosheets, 2-5 parts of boron nitride, 1-3 parts of dispersant, and 45-65 parts of deionized water.

[0029] Thirdly, this application provides a heating device including the heating film described in any of the first aspects, wherein the graphene film of the heating film is connected to a wire.

[0030] Fourthly, this application provides a vehicle, including a vehicle body, wherein the heating components on the vehicle body include the heating device described in the third aspect.

[0031] This application provides a heating film and its preparation method, heating equipment, and vehicle. The heating film includes: a graphene film and a gradient radiation coating on the surface of the graphene film; the gradient radiation coating includes a bottom layer in contact with the graphene surface, an intermediate layer disposed on the bottom layer, and a top layer disposed on the intermediate layer; the mass fraction of the resin matrix in the bottom layer is greater than that in the intermediate layer, and the mass fraction of the resin matrix in the intermediate layer is greater than that in the top layer; the mass fraction of boron nitride in the bottom layer is greater than that in the intermediate layer, and the mass fraction of boron nitride in the intermediate layer is greater than that in the top layer; the mass fraction of infrared radiation material in the bottom layer is less than that in the intermediate layer, and the mass fraction of infrared radiation material in the intermediate layer is less than that in the top layer. Detailed Implementation

[0032] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions in the embodiments of this invention will be clearly and completely described below in conjunction with the embodiments of this invention. Obviously, the described embodiments are only some embodiments of this invention, not all embodiments. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0033] In cold climates, heated car seats and interior trim are crucial for enhancing passenger comfort. Existing heating systems typically use electric heating films or resistance wires to transfer heat to the seat surface for rapid warming. However, traditional heating solutions suffer from significant performance bottlenecks in low-temperature environments (such as below -20°C): firstly, the heating efficiency of electric heating elements is greatly affected by ambient temperature, requiring higher power to reach the set temperature at low temperatures; secondly, existing material systems (such as resin-graphene composite films) are prone to aging and cracking during long-term use, leading to increased resistance, uneven heating, and even localized short circuits, posing safety hazards. Furthermore, seat heating functions demand extremely high material flexibility, requiring structural integrity to withstand frequent bending (such as seat adjustments and crash tests).

[0034] In view of this, this application provides a heating film with a graphene film as its substrate. No resin is added during the preparation of the graphene film, thus eliminating the problem of resin aging affecting resistance. The graphene film has three gradient radiation coating layers: the bottom layer focuses on adhesion and thermal conductivity, the middle layer balances thermal conductivity and radiation, and the surface layer maximizes radiation efficiency. The three layers are separated by a compositional gradient transition, eliminating interlayer stress concentration. This gradient radiation coating design increases the infrared emissivity of the heating film to above 0.93, and the gradient transition eliminates interlayer stress concentration, preventing delamination and cracking.

[0035] The technical solution of this application and how the technical solution of this application solves the above-mentioned technical problems are described in detail below with specific embodiments. The following specific embodiments can be combined with each other, and the same or similar concepts or processes may not be described again in some embodiments.

[0036] This application provides a heating film, including: a graphene film and a gradient radiation coating on the surface of the graphene film; the gradient radiation coating includes a bottom layer in contact with the graphene surface, an intermediate layer disposed on the bottom layer, and a top layer disposed on the intermediate layer.

[0037] The gradient radiation coating consists of a resin matrix, boron nitride, and infrared radiation materials in its base, intermediate, and top layers.

[0038] The mass fraction of the resin matrix in the bottom layer is greater than that in the middle layer, and the mass fraction of the resin matrix in the middle layer is greater than that in the top layer.

[0039] The mass fraction of boron nitride in the bottom layer is greater than that in the middle layer, and the mass fraction of boron nitride in the middle layer is greater than that in the surface layer.

[0040] The mass fraction of the infrared radiation material in the bottom layer is less than that in the middle layer, and the mass fraction of the infrared radiation material in the middle layer is less than that in the surface layer.

[0041] The high boron nitride content in the bottom layer (with an in-plane thermal conductivity >30 W / m·K) rapidly homogenizes the point-like heat sources formed by the carbon nanotube-graphene network in the graphene heating film, improving the uniformity of the coating surface temperature distribution. The middle layer (radiation conversion layer) receives the heat flow after homogenization from the bottom layer. Infrared radiation materials efficiently convert thermal energy into infrared radiation, while an appropriate amount of boron nitride in the middle layer reflects inward radiation back into the coating, creating a "secondary utilization." The surface layer, a high-infrared radiation material, receives infrared radiation and heat conduction from the middle layer and, according to Kirchhoff's law of thermal radiation, efficiently converts the received radiation into far-infrared emission. Therefore, an energy transfer chain is formed between the three layers: "uniform thermal field in the bottom layer - radiation conversion and recovery in the middle layer - efficient far-infrared output in the surface layer." This three-layer gradient radiation coating can increase the infrared emissivity of the graphene film from 0.45 to 0.93, meeting the temperature rise requirements at low temperatures. Removing one layer not only results in the loss of its own contribution but also leads to a decrease in the performance of the other two layers, resulting in an overall emissivity lower than the three-layer combination.

[0042] Through a multi-layered gradient structure design, the three layers perform different functions: the bottom layer (thermally conductive bonding layer) focuses on adhesion and thermal conductivity, the middle layer (radiative conversion layer) balances thermal conductivity and radiation, and the top layer (high emissivity layer) maximizes radiation efficiency, thus resolving the contradiction between high emissivity and coating adhesion in a single-layer radiation coating. In addition, the gradient transition of components between the three layers can also eliminate interlayer stress concentration.

[0043] Furthermore, the heating film uses pure graphene film, free of resin and additives, so its resistance does not change over time and it has good aging resistance. Pure graphene film has low resistance, resulting in rapid and uniform heating after being energized. Its high strength allows it to be cut into any shape, effectively avoiding ventilation holes during the placement of the seat heating pad without affecting the heating effect.

[0044] In some embodiments, the substrate comprises 25-35 parts of resin matrix, 15-25 parts of boron nitride, and 5-10 parts of graphene nanosheets; for example, the resin matrix may be composed of any number of components, such as 25, 27, 30, 32, 35, or more; the boron nitride may be composed of any number of components, such as 15, 17, 20, 23, 25, or more; and the graphene nanosheets may be composed of any number of components, such as 5, 6, 7, 8, 9, 10, or more.

[0045] In the bottom layer, the high boron nitride content provides excellent thermal conductivity (in-plane thermal conductivity >30W / m·K), enabling the heat generated by the heating film to spread rapidly and evenly; the high resin content ensures strong adhesion to the graphene film surface; and the graphene nanosheets provide additional conductive and thermal pathways.

[0046] The intermediate layer comprises 18-25 parts of resin matrix, 8-15 parts of boron nitride, 3-8 parts of graphene nanosheets, and 8-15 parts of carbon black; for example, the resin matrix may be composed of any number of components, such as 18, 20, 22, 23, 25, or more; the boron nitride may be composed of any number of components, such as 8, 10, 12, 14, 15, or more; and the graphene nanosheets may be composed of any number of components, such as 3, 4, 5, 6, 7, 8, or more.

[0047] In the intermediate layer, carbon black and graphene nanosheets work synergistically to provide efficient infrared radiation capability; the boron nitride content is moderate, taking into account both thermal conductivity and radiation function; the resin content is moderate, ensuring interlayer bonding strength without excessively encapsulating radiation powder.

[0048] The boron nitride content in the intermediate layer (8-15 parts) is a preferred option after optimization. More than 8 parts provides strong thermal conductivity and reduces the likelihood of heat buildup. Less than 15 parts avoids excessive boron nitride-induced infrared reflection (boron nitride exhibits Resthralen band reflection characteristics in the infrared band, at 700-1400 cm⁻¹). -1 (Band reflectivity > 80%).

[0049] The surface layer comprises 10-18 parts of resin matrix, 2-5 parts of boron nitride, 5-12 parts of graphene nanosheets, and 10-20 parts of carbon black. For example, the resin matrix may be composed of 10, 12, 14, 16, 18, or more of any component; the boron nitride may be composed of 2, 3, 4, 5, or more of any component; and the graphene nanosheets may be composed of 5, 7, 9, 10, 11, 12, or more of any component.

[0050] In the surface layer, high carbon black and high graphene content maximize infrared emissivity (emissivity > 0.93); this layer has radiation as its main function and low boron nitride content; low resin content reduces the encapsulation of radiation powder, allowing the powder to be fully exposed on the surface and maximizing radiation efficiency.

[0051] From the bottom layer to the top layer, the boron nitride content decreases, the thermal conductivity gradually weakens, and the radiation function gradually strengthens; from the bottom layer to the top layer, the carbon black + graphene content increases, and the infrared radiation capability increases layer by layer; from the bottom layer to the top layer, the resin content decreases, the adhesion gradually weakens, but the radiation efficiency gradually strengthens; the transition between each layer is achieved through gradient ratios to avoid abrupt performance changes and stress concentration at the interlayer interfaces.

[0052] In some embodiments, the bottom layer and the intermediate layer are connected by covalent bonds formed by a silane coupling agent. The silane coupling agent (e.g., KH-550) not only forms chemical bonds with the boron nitride surface, but its amino groups also undergo condensation reactions with the hydroxyl groups of the acrylic resin in the intermediate layer, forming covalent bridges. Therefore, there is no clear physical interface between the layers; instead, a chemically continuous gradient transition region is formed, rather than a simple physical stacking, which increases structural stability and bending resistance.

[0053] In some embodiments, to increase the bonding strength between the intermediate layer and the surface layer, the intermediate layer and the surface layer are connected by covalent bonds formed by a silane coupling agent.

[0054] In some embodiments, the infrared radiating material of the intermediate layer includes graphene nanosheets and / or carbon black.

[0055] In some embodiments, the thickness of the bottom layer is 3-5 μm, for example, a range of any two of 3 μm, 4 μm, 5 μm, or more; the thickness of the intermediate layer is 5-8 μm, for example, a range of any two of 5 μm, 6 μm, 7 μm, 8 μm, or more; and the thickness of the top layer is 2-5 μm, for example, a range of any two of 2 μm, 3 μm, 4 μm, 5 μm, or more. The thinner top layer ensures flexibility and prevents brittle cracking.

[0056] In some embodiments, the resin matrix is ​​acrylic resin or polyurethane. The resin matrix, as a support material, has the ability to chemically react with the coupling agent to enhance interlayer bonding.

[0057] In some embodiments, a resin-free graphene film is used, with a sheet resistance ranging from 40 to 60 mΩ / □.

[0058] This application also provides a method for preparing a heating film, including the following steps:

[0059] A first slurry is coated on the surface of a graphene film and then dried to obtain a first intermediate product.

[0060] The second intermediate product is obtained by coating the surface of the first intermediate product with the second slurry and then drying it.

[0061] A heating film is obtained by coating a third slurry onto the surface of the second intermediate product and then drying it.

[0062] The resin matrix mass fraction of the first slurry is greater than that of the second slurry, and the resin matrix mass fraction of the second slurry is greater than that of the third slurry.

[0063] The boron nitride mass fraction of the first slurry is greater than that of the second slurry, and the boron nitride mass fraction of the second slurry is greater than that of the third slurry.

[0064] The mass fraction of infrared radiating material in the first slurry is less than that in the second slurry, and the mass fraction of infrared radiating material in the second slurry is less than that in the third slurry.

[0065] Specifically, the first slurry includes 25-35 parts of resin matrix, 15-25 parts of boron nitride, 5-10 parts of graphene nanosheets, 1-3 parts of silane coupling agent, 1-2 parts of dispersant, and 40-60 parts of deionized water.

[0066] The second slurry comprises 18-25 parts resin matrix, 8-15 parts carbon black, 3-8 parts graphene nanosheets, 8-15 parts boron nitride, 1-3 parts dispersant, and 45-65 parts deionized water.

[0067] The third slurry consists of 10-18 parts resin matrix, 10-20 parts carbon black, 5-12 parts graphene nanosheets, 2-5 parts boron nitride, 1-3 parts dispersant, and 45-65 parts deionized water.

[0068] Specifically, the prepared slurries are poured into the coating machine's trough. The coating gap is adjusted, and the calendered graphene heating film is passed through the coating machine's scraper to sequentially coat the graphene film with three layers of radiation-enhancing slurry, applying the required thickness. After each layer is coated, it is dried in a vertical oven at 100-120℃. After passing through a cooling roller, the second and third layers are applied sequentially. The second layer is dried at the same temperature before the third layer is applied. After the third layer is applied, it enters a large oven at 150-180℃ for overall curing. During this process, the resin molecular chains between adjacent layers diffuse into each other, forming an interpenetrating network (IPN) structure. This results in no clear physical interface between the three layers, but rather a chemically continuous gradient transition zone.

[0069] This application also provides a heating device, including the above-mentioned heating film, wherein the graphene film of the heating film is connected to a wire for energizing the heating film to generate heat.

[0070] Specifically, the manufacturing process of this heating device is as follows: The prepared heating film is laminated and rolled up with a PET backing film. A cutting die is prepared according to the heating film circuit design. The roll is cut into the required shape using the die, excess graphene film is removed, and the required film is rolled up. The cut heating film is pressed onto the required flame-retardant nonwoven fabric A, with the coated heating film side facing upwards. TPU hot melt adhesive is pre-attached to the flame-retardant nonwoven fabric. After the heating film is placed in the designated position, wires and an NTC temperature control probe are riveted at the wiring points. After powering on and heating without abnormalities, nonwoven fabric B (same shape as A) is placed over the graphene heating film (nonwoven fabric B has a heat-insulating reflective film underneath). The three layers are then pressed together using a hot press, leaving wiring openings. The wires are connected to the graphene film using rivets. After wiring, hot melt adhesive is applied for fixation, and the rivet points are covered with acetate cloth to increase strength and prevent sparking.

[0071] This application also provides an automotive component, which can be a heated steering wheel, heated interior trim, heated seats, heated door handles, etc. The component includes the aforementioned heating device, which includes the heating film described in the above embodiments.

[0072] This application also provides a vehicle, including a vehicle body and the aforementioned heating components in the vehicle body.

[0073] The performance of the heating film is characterized and analyzed below using specific embodiments.

[0074] The following examples and comparative examples use the same preparation process for the graphene films:

[0075] 1.1 Preparation of heating slurry;

[0076] By weight, the composition is: 100 parts graphene oxide paste, 200-600 parts deionized water, 5-10 parts dispersant, 2-8 parts carbon nanotubes, and 5-10 parts alkali solution.

[0077] Among them, the carbon nanotubes used are FT9100 from Jiangsu Tiannai Technology Co., Ltd. (the length of the carbon nanotubes is 10um); the graphene oxide paste uses SE2430W from Sixth Element (solid content 41-47%); the alkaline solution (ammonia water) uses ammonium hydroxide reagent from Sinopharm with a concentration of 25%-28%; and the dispersant uses 4900 from Vebos New Materials (Weifang) Co., Ltd.

[0078] Add a dispersant to deionized water and stir until homogeneous. Dispersion speed is 800-1000 r / min. First, add carbon nanotubes and stir for 5-10 min, then add graphene oxide paste and disperse at 200-400 r / min. Add ammonia water for neutralization and adjust the pH to 6-7. Stir for 2-4 h, resulting in a slurry viscosity of 40000-50000 mPa·s. Then, perform high-pressure homogenization and vacuum degassing. The high-pressure homogenization pressure is 50-250 MPa, and the vacuum degassing vacuum value is -95 to -50 kPa. The prepared graphene oxide slurry has a viscosity of 20000-40000 mPa·s and a solid content of 6%-10%.

[0079] 1.2 Graphene film preparation;

[0080] Graphene oxide slurry is fed into the coating machine's feed trough at a speed of 0.5-10 m / min, resulting in a coating thickness of 2-5 mm. The oven temperature is 50-110℃, and the dry film thickness of the graphene oxide coating is 0.3-0.8 mm. The graphene film is separated from the base film to obtain a graphene film roll. The graphene film roll is then heat-treated in an oven, a carbonization furnace, and a graphitization furnace at temperatures of 300℃, 1100℃, and 2800℃, respectively, for 70 hours, 26 hours, and 24 hours. The fired roll is then calendered to produce a 50 μm thick heating film on a calender. This heating film is smooth and flawless. The sheet resistance of this heating film is 40-60 mΩ / □, which can be adjusted by the film thickness and the solid content of the slurry.

[0081] The preparation processes for the slurries in the following embodiments and comparative examples are the same, and the following processes are used:

[0082] 1.3 Preparation of slurry.

[0083] Raw materials: waterborne acrylic resin is Tekspro 7612 from Yantai Wanhua (solid content is 55%), dispersant is HH2008 from Houhuan Chemical Additives, graphene powder is SE1231 from Sixth Element, carbon black is BP2000 from Cabot, boron nitride is BN-N from Liaobin Chemical, and coupling agent is KH-550 from Nanjing Pinning.

[0084] Add a dispersant to deionized water and stir until homogeneous at a speed of 800-1000 rpm. Then add carbon black / graphene nanosheets and boron nitride powder and stir for 5-10 minutes. Next, grind the slurry in a sand mill for 5-8 hours to obtain a dispersion with a fineness of 7-10 μm. Add the ground dispersion to water-based acrylic resin and stir at 200-400 rpm for 0.5-1 hours, resulting in a slurry viscosity of 1000-3000 MPa·s. Then, perform high-pressure homogenization and vacuum degassing. The high-pressure homogenization pressure is 50-250 MPa, and the vacuum degassing vacuum value is -95 to -50 kPa. The resulting slurry is then obtained.

[0085] The heating films in the following embodiments and comparative examples are prepared using the same process, as follows:

[0086] The prepared first, second, and third slurries are poured into their respective coating machine troughs. The coating gap is adjusted, and the calendered graphene heating film is passed through the coating machine's doctor blade to sequentially coat the graphene film with three layers of radiation-enhancing slurry, applying the required thickness. After each layer is coated, it is dried in a vertical oven at 100-120℃. After passing through a cooling roller, the second and third layers are applied sequentially. The second layer is dried at the same temperature before the third layer is applied. After the third layer is completed, it is placed in a large oven and cured at 150-180℃. The coating machine speed is 10-20 meters per minute.

[0087] Example 1

[0088] First slurry formulation: 35 parts water-based acrylic resin, 15 parts boron nitride (particle size 1-5μm, hexagonal boron nitride), 5 parts graphene nanosheets (number of layers <5, sheet size 1-5μm), 3 parts silane coupling agent (KH-550), 2 parts dispersant (HH2008), and 40 parts deionized water.

[0089] The second slurry formulation consists of: 20 parts water-based acrylic resin, 15 parts boron nitride (particle size 1-5μm, hexagonal boron nitride), 15 parts carbon black (particle size 20-50nm), 8 parts graphene nanosheets (number of layers <5, sheet size 1-5μm), 2 parts dispersant (HH2008), and 40 parts deionized water.

[0090] The third slurry formulation consists of: 15 parts water-based acrylic resin, 5 parts boron nitride (particle size 1-5μm, hexagonal boron nitride), 20 parts carbon black (particle size 20-50nm), 12 parts graphene nanosheets (number of layers <5, sheet size 1-5μm), 2 parts dispersant (HH2008), and 46 parts deionized water.

[0091] Example 2

[0092] First slurry formulation: 35 parts water-based acrylic resin, 15 parts boron nitride (particle size 1-5μm, hexagonal boron nitride), 5 parts graphene nanosheets (number of layers <5, sheet size 1-5μm), 3 parts silane coupling agent (KH-550), 2 parts dispersant (HH2008), and 40 parts deionized water.

[0093] The second slurry formulation consists of: 27 parts water-based acrylic resin, 8 parts boron nitride (particle size 1-5μm, hexagonal boron nitride), 15 parts carbon black (particle size 20-50nm), 8 parts graphene nanosheets (number of layers <5, sheet size 1-5μm), 2 parts dispersant (HH2008), and 40 parts deionized water.

[0094] The third slurry formulation consists of: 10 parts water-based acrylic resin, 5 parts boron nitride (particle size 1-5μm, hexagonal boron nitride), 20 parts carbon black (particle size 20-50nm), 12 parts graphene nanosheets (number of layers <5, sheet size 1-5μm), 2 parts dispersant (HH2008), and 46 parts deionized water.

[0095] Example 3

[0096] First slurry formulation: 35 parts water-based acrylic resin, 15 parts boron nitride (particle size 1-5μm, hexagonal boron nitride), 5 parts graphene nanosheets (number of layers <5, sheet size 1-5μm), 3 parts silane coupling agent (KH-550), 2 parts dispersant (HH2008), and 40 parts deionized water.

[0097] The second slurry formulation consists of: 20 parts water-based acrylic resin, 20 parts boron nitride (particle size 1-5μm, hexagonal boron nitride), 13 parts carbon black (particle size 20-50nm), 5 parts graphene nanosheets (number of layers <5, sheet size 1-5μm), 2 parts dispersant (HH2008), and 40 parts deionized water.

[0098] The third slurry formulation consists of: 10 parts water-based acrylic resin, 5 parts boron nitride (particle size 1-5μm, hexagonal boron nitride), 20 parts carbon black (particle size 20-50nm), 12 parts graphene nanosheets (number of layers <5, sheet size 1-5μm), 2 parts dispersant (HH2008), and 46 parts deionized water.

[0099] Example 4

[0100] First slurry formulation: 35 parts water-based acrylic resin, 15 parts boron nitride (particle size 1-5μm, hexagonal boron nitride), 5 parts graphene nanosheets (number of layers <5, sheet size 1-5μm), 3 parts silane coupling agent (KH-550), 2 parts dispersant (HH2008), and 40 parts deionized water.

[0101] The second slurry formulation consists of: 27 parts water-based acrylic resin, 4 parts boron nitride (particle size 1-5μm, hexagonal boron nitride), 15 parts carbon black (particle size 20-50nm), 8 parts graphene nanosheets (number of layers <5, sheet size 1-5μm), 2 parts dispersant (HH2008), and 44 parts deionized water.

[0102] The third slurry formulation consists of: 10 parts water-based acrylic resin, 5 parts boron nitride (particle size 1-5μm, hexagonal boron nitride), 20 parts carbon black (particle size 20-50nm), 12 parts graphene nanosheets (number of layers <5, sheet size 1-5μm), 2 parts dispersant (HH2008), and 46 parts deionized water.

[0103] Example 5

[0104] First slurry formulation: 35 parts water-based acrylic resin, 15 parts boron nitride (particle size 1-5μm, hexagonal boron nitride), 5 parts graphene nanosheets (number of layers <5, sheet size 1-5μm), 3 parts silane coupling agent (KH-550), 2 parts dispersant (HH2008), and 40 parts deionized water.

[0105] The second slurry formulation consists of: 22 parts water-based acrylic resin, 13 parts boron nitride (particle size 1-5μm, hexagonal boron nitride), 15 parts carbon black (particle size 20-50nm), 8 parts graphene nanosheets (number of layers <5, sheet size 1-5μm), 2 parts dispersant (HH2008), and 40 parts deionized water.

[0106] The third slurry formulation consists of: 18 parts water-based acrylic resin, 8 parts boron nitride (particle size 1-5μm, hexagonal boron nitride), 12 parts carbon black (particle size 20-50nm), 8 parts graphene nanosheets (number of layers <5, sheet size 1-5μm), 2 parts dispersant (HH2008), and 52 parts deionized water.

[0107] Example 6

[0108] The first slurry formulation consists of 35 parts water-based acrylic resin, 15 parts boron nitride (particle size 1-5μm, hexagonal boron nitride), 5 parts graphene nanosheets (number of layers <5, sheet size 1-5μm), 2 parts dispersant (HH2008), and 43 parts deionized water.

[0109] The second slurry formulation consists of: 22 parts water-based acrylic resin, 13 parts boron nitride (particle size 1-5μm, hexagonal boron nitride), 15 parts carbon black (particle size 20-50nm), 8 parts graphene nanosheets (number of layers <5, sheet size 1-5μm), 2 parts dispersant (HH2008), and 40 parts deionized water.

[0110] The third slurry formulation consists of: 15 parts water-based acrylic resin, 5 parts boron nitride (particle size 1-5μm, hexagonal boron nitride), 20 parts carbon black (particle size 20-50nm), 12 parts graphene nanosheets (number of layers <5, sheet size 1-5μm), 2 parts dispersant (HH2008), and 46 parts deionized water.

[0111] Comparative Example 1

[0112] There are no three types of slurry; only a graphene heating film with a thickness of 50μm is used.

[0113] Comparative Example 2

[0114] The first slurry is the same as the first slurry in Example 1, with no second slurry and no third slurry.

[0115] Comparative Example 3

[0116] The second slurry is the same as the second slurry in Example 1, but without the first slurry and without the third slurry.

[0117] Comparative Example 4

[0118] The third slurry is the same as the third slurry in Example 1, but without the first slurry and without the second slurry.

[0119] Comparative Example 5

[0120] The first and third slurries are the same as in Example 1, but there is no second slurry.

[0121] Comparative Example 6

[0122] The first slurry, the second slurry, and the third slurry differ from those in Example 1 in that the thickness of the three-layer membrane is controlled differently during the preparation process, as detailed in Table 1.

[0123] Comparative Example 7

[0124] First slurry formulation: 15 parts water-based acrylic resin, 5 parts boron nitride (particle size 1-5μm, hexagonal boron nitride), 20 parts carbon black (particle size 20-50nm), 12 parts graphene nanosheets (number of layers <5, sheet size 1-5μm), 2 parts dispersant (HH2008), and 46 parts deionized water.

[0125] The second slurry formulation consists of: 22 parts water-based acrylic resin, 13 parts boron nitride (particle size 1-5μm, hexagonal boron nitride), 15 parts carbon black (particle size 20-50nm), 8 parts graphene nanosheets (number of layers <5, sheet size 1-5μm), 2 parts dispersant (HH2008), and 40 parts deionized water.

[0126] The third slurry formulation consists of: 35 parts water-based acrylic resin, 15 parts boron nitride (particle size 1-5μm, hexagonal boron nitride), 5 parts graphene nanosheets (number of layers <5, sheet size 1-5μm), 3 parts silane coupling agent (KH-550), 2 parts dispersant (HH2008), and 40 parts deionized water.

[0127] Performance testing:

[0128] The heating films of the above embodiments and comparative examples are laminated and rolled together with PET backing film (the backing film has a basis weight of 100g / m² and a release force of 5g). A cutting die is prepared according to the heating film circuit design. The roll is cut into the desired shape using the die, excess graphene film is removed, and the desired film is rolled up. The cut heating film is pressed onto the required flame-retardant nonwoven fabric A, with the heating film side coated with radiation-enhancing coating facing upwards. TPU hot melt adhesive is pre-attached to the flame-retardant nonwoven fabric. After the heating film is placed in the specified position, wires and NTC temperature control probes are riveted at the wiring positions. After powering on and heating without abnormalities, nonwoven fabric B (with the same shape as A) is placed over the graphene heating film (nonwoven fabric B has a heat-insulating reflective film underneath). The three layers are then pressed together using a hot press, leaving wiring openings. The heating pad is prepared by connecting the wires and the graphene film with rivets, fixing them with hot melt glue after wiring, and covering the rivet points with acetate cloth.

[0129] Infrared emissivity test: Infrared emissivity was tested according to GB / T 2797-2015 standard.

[0130] Bending test: Perform 100,000 bending cycles on each bending point of the heating pad and measure the change in resistance.

[0131] Heating performance test: Each heating pad was placed in the same seat (seat cover thickness 10mm (PU leather), memory foam thickness 20mm), and heated at -20℃ for 5 minutes, and the surface temperature was measured.

[0132] Table 1. Performance of each embodiment and comparative example

[0133]

[0134] Referring to the data in Table 1, the infrared emissivity of the three-layer gradient radiation coating is greater than that of the single-layer and double-layer infrared emissivity of Comparative Example 5. Compared to Comparative Example 5, Example 1 has an additional intermediate layer, increasing the infrared emissivity from 0.82 to 0.93, demonstrating that the intermediate layer is indispensable for improving infrared emissivity. The thickness ratio of each layer in Comparative Example 6 also affects the infrared emissivity. Compared to Comparative Example 7, Example 1 achieves high infrared emissivity by following the increasing patterns of carbon black and graphene content from the bottom layer to the top layer, as well as the decreasing patterns of boron nitride content and resin content from the bottom layer to the top layer.

[0135] Comparing the various embodiments, in Example 3 compared to Example 1, the amount of boron nitride increased. Excessive boron nitride reflects infrared radiation, resulting in a slight decrease in infrared emissivity. In Example 4 compared to Example 1, the amount of boron carbide decreased, leading to heat accumulation and a slightly lower temperature after 5 minutes of heating compared to Example 1. In Example 1 compared to Example 6, a silane coupling agent was used, resulting in stronger interlayer bonding and improved bending resistance.

[0136] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A heating film, characterized in that, include: Graphene film and gradient radiation coating on the surface of the graphene film; The gradient radiation coating includes a bottom layer in contact with the graphene surface, an intermediate layer disposed on the bottom layer, and a surface layer disposed on the intermediate layer. The resin matrix of the bottom layer has a greater mass percentage than the resin matrix of the intermediate layer, and the resin matrix of the intermediate layer has a greater mass percentage than the resin matrix of the top layer. The boron nitride mass fraction of the bottom layer is greater than that of the intermediate layer, and the boron nitride mass fraction of the intermediate layer is greater than that of the surface layer. The mass fraction of the infrared radiation material in the bottom layer is less than that in the middle layer, and the mass fraction of the infrared radiation material in the middle layer is less than that in the surface layer.

2. The heating film according to claim 1, characterized in that, The bottom layer comprises 25-35 parts of resin matrix, 15-25 parts of boron nitride, and 5-10 parts of graphene nanosheets; The intermediate layer comprises 18-25 parts of resin matrix, 8-15 parts of boron nitride, 3-8 parts of graphene nanosheets, and 8-15 parts of carbon black. The surface layer comprises 10-18 parts of resin matrix, 2-5 parts of boron nitride, 5-12 parts of graphene nanosheets, and 10-20 parts of carbon black.

3. The heating film according to claim 1, characterized in that, The bottom layer and the intermediate layer are connected by covalent bonds formed by a silane coupling agent.

4. The heating film according to claim 1, characterized in that, The infrared radiation material of the intermediate layer includes graphene nanosheets and / or carbon black.

5. The heating film according to any one of claims 1-4, characterized in that, The thickness of the bottom layer is 3-5 μm, the thickness of the intermediate layer is 5-8 μm, and the thickness of the top layer is 2-5 μm.

6. The heating film according to any one of claims 1-4, characterized in that, The resin matrix is ​​acrylic resin or polyurethane; And / or, the sheet resistance of the graphene film is 40-60 mΩ / □.

7. A method for preparing a heating film according to any one of claims 1-6, characterized in that, Includes the following steps: A first slurry is coated on the surface of a graphene film and then dried to obtain a first intermediate product. A second slurry is coated onto the surface of the first intermediate product and then dried to obtain the second intermediate product. A heating film is obtained by coating the surface of the second intermediate product with a third slurry and then drying it. The resin matrix mass fraction of the first slurry is greater than that of the second slurry, and the resin matrix mass fraction of the second slurry is greater than that of the third slurry. The boron nitride mass fraction of the first slurry is greater than that of the second slurry, and the boron nitride mass fraction of the second slurry is greater than that of the third slurry. The mass fraction of infrared radiating material in the first slurry is less than the mass fraction of infrared radiating material in the second slurry, and the mass fraction of infrared radiating material in the second slurry is less than the mass fraction of infrared radiating material in the third slurry.

8. The preparation method according to claim 7, characterized in that, The first slurry comprises 25-35 parts of resin matrix, 15-25 parts of boron nitride, 5-10 parts of graphene nanosheets, 1-3 parts of silane coupling agent, 1-2 parts of dispersant, and 40-60 parts of deionized water. The second slurry comprises 18-25 parts of resin matrix, 8-15 parts of carbon black, 3-8 parts of graphene nanosheets, 8-15 parts of boron nitride, 1-3 parts of dispersant, and 45-65 parts of deionized water; The third slurry comprises 10-18 parts of resin matrix, 10-20 parts of carbon black, 5-12 parts of graphene nanosheets, 2-5 parts of boron nitride, 1-3 parts of dispersant, and 45-65 parts of deionized water.

9. A heating device, characterized in that, The heating film includes the heating film according to any one of claims 1-6, wherein the graphene film of the heating film is connected to a wire.

10. A vehicle, characterized in that, The vehicle body includes a heating component, which includes the heating device as described in claim 9.

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