A flexible carbon-based heating element, its preparation method and application

Abstract

This invention relates to the field of power generation and heating materials, specifically a flexible carbon-based heating element, its preparation method, and its application. This flexible carbon-based heating element includes an upper substrate and a lower substrate arranged vertically, with a heating layer between them. The heating layer includes a carbon nanotube membrane, with copper foil conductors connected to both ends of the carbon nanotube membrane via conductive paste. The copper foil conductors are connected to wires. The thickness of the flexible carbon-based heating element is 0.2–0.6 mm. This flexible carbon-based heating element is manufactured by cutting, bonding, and hot-pressing the various components together. The total thickness of the flexible carbon-based heating element prepared by this invention can be controlled below 0.6 mm. The core heating layer is a micron-sized carbon nanotube membrane, combined with a flexible polyimide substrate and rolled copper foil, exhibiting excellent flexibility and fit. Using conductive silver paste as the connection medium between the carbon nanotube membrane and the copper foil conductor creates a low-resistance, large-area surface contact, effectively reducing contact resistance and the risk of localized overheating, ensuring the uniformity and stability of the surface heating.

Description

Technical Field

[0001] This invention relates to the field of electrothermal materials technology, and in particular to an ultrathin, flexible, planar heating flexible carbon-based heating component, its preparation method and application. Background Technology

[0002] With the rapid development of wearable devices, flexible medical physiotherapy, curved smart terminals, and other fields, the market's performance requirements for electrothermal elements have shifted from the traditional single heating function to a comprehensive pursuit of high flexibility, bending resistance, and rapid response capabilities. An ideal flexible heating component should be able to conform to the complex curves of the human body like fabric, maintain stable performance under repeated bending, winding, and even dynamic deformation, and achieve uniform and efficient heating in a very short time.

[0003] Currently, mainstream electrothermal technologies face significant bottlenecks in such demanding flexible and dynamic application scenarios. Traditional metal resistance wire heating elements, being essentially metal wires, are inherently inflexible and rigid, making it difficult to achieve large-area uniform bonding. They are also prone to breakage at points of stress concentration due to bending or vibration, resulting in a short bending lifespan. While thick-film heating elements printed with carbon paste or graphite paste offer some flexibility, their thicker resistive layer and larger heat capacity lead to slow heating rates and sluggish response. Furthermore, their adhesive matrix is ​​prone to micro-cracks under repeated bending, causing resistance drift or even open-circuit failure, resulting in insufficient long-term dynamic reliability.

[0004] Therefore, developing a new type of heating component that combines the three core characteristics of "flexibility" (good fit), "bending resistance" (high dynamic reliability) and "rapid heating up" (low heat capacity and high thermal conductivity) has become a key technological issue that urgently needs to be addressed in the fields of flexible electronics and advanced thermal management. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to overcome the shortcomings of the prior art and provide a flexible carbon-based heating component with simple structure, ultra-thin and flexible, uniform heating and reliable connection, as well as its preparation method and application.

[0006] The technical solution adopted by this invention to solve its technical problem is: A flexible carbon-based heating component includes an upper substrate and a lower substrate disposed on the upper and lower substrates, with a heating layer disposed between the upper substrate and the lower substrate; The heating layer includes a carbon nanotube membrane, with copper foil conductors connected to both ends of the carbon nanotube membrane via conductive paste, and wires connected to the copper foil conductors; the carbon nanotube membrane is a thin film formed by the self-assembly of multi-walled carbon nanotubes with a diameter of 10-50 nm through van der Waals forces, with a film thickness of 12-20 μm and a sheet resistance of 1-15 ohms. The thickness of the flexible carbon-based heating element is 0.2–0.6 mm.

[0007] Furthermore, both the upper and lower substrates are made of polyimide film; the conductive paste is conductive silver paste.

[0008] Furthermore, the thickness of the upper substrate is 0.17–0.21 mm, and the thickness of the lower substrate is 0.17–0.21 mm.

[0009] Furthermore, the copper foil conductor is a rolled copper foil with a thickness of 18–35 μm and a width of 8–15 mm.

[0010] A method for preparing the above-mentioned flexible carbon-based heating component, the method specifically includes the following steps: Step S1: Cut the upper substrate, lower substrate, carbon nanotube film, and copper foil conductor to the target size according to production requirements; Step S2: A copper foil conductor is attached to the upper surface of the substrate. Step S3: Screen print conductive paste onto the surface of the copper foil conductor. The printing amount of conductive paste is 50g / m. 2 ; Step S4: Align and attach the two ends of the carbon nanotube membrane with the conductive paste; Step S5: Lay the upper substrate on the upper surface of the carbon nanotube membrane, and then seal the edges of the upper and lower substrates by hot pressing to encapsulate the heating layer inside. Step S6: Solder a wire onto the copper foil conductor, with the wire passing through the upper substrate and connecting to the copper foil conductor; apply insulating adhesive to the solder joint and attach insulating tape. Step S7: Test the resistance and heating performance. Qualified products are finished flexible carbon-based heating components.

[0011] Furthermore, in step S2, the copper foil conductor is bonded to the substrate by an adhesive, which is an epoxy resin adhesive. Epoxy resin adhesives provide extremely high bonding strength and durability, ensuring that the copper foil does not peel off from the substrate during hot pressing and bending.

[0012] Furthermore, in step S5, the pressure of hot pressing is 0.8–1.5 MPa, the temperature is 140–160°C, and the pressing time is 30–50 seconds.

[0013] Furthermore, in step S6, the insulating adhesive is preferably room-temperature curing silicone rubber, and the insulating tape is black acetate tape. Silicone rubber has excellent insulation, high and low temperature resistance, and flexibility, and can well wrap the solder joints and adapt to bending. Acetate tape provides additional mechanical protection and high-temperature insulation, and its thinness does not significantly increase the component thickness.

[0014] Furthermore, the flexible carbon-based heating component is used in smart clothing, car seat heating, medical devices, and portable insulation equipment.

[0015] The beneficial effects of this invention are as follows: This invention has a reasonable design and a simple preparation method, and has the following advantages: 1. Ultra-thin and flexible: The total thickness of the component can be controlled below 0.6mm. The core heating layer is a micron-level carbon nanotube film, combined with a flexible polyimide substrate and rolled copper foil, giving it excellent flexibility and fit. 2. Reliable connection and uniform heating: The use of conductive silver paste as the connection medium between the carbon nanotube film and the copper foil conductor forms a low-resistance, large-area surface contact, which effectively reduces contact resistance and the risk of local overheating, and ensures the uniformity and stability of surface heating. 3. Stable structure and good sealing: The edges of the upper and lower substrates are sealed together by hot-pressing composite process, and the heating layer is completely encapsulated in an insulating environment, which improves the mechanical strength, environmental aging resistance and safety of the component. 4. Simple process and suitable for mass production: The preparation method has clear steps and mainly adopts mature processes such as cutting, bonding, screen printing and hot pressing, which are easy to automate and scale up production, with high yield and controllable cost. Attached Figure Description

[0016] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0017] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0018] Figure 1 This is a schematic diagram of the flexible carbon-based heating component in this invention; Figure 2 This is a flowchart of the preparation method in this invention; Figure 3 This is a graph showing the bending test results of the flexible carbon-based heating element prepared in Example 1; Figure 4 This is a graph showing the water washing test results of the flexible carbon-based heating element prepared in Example 1; Figure 5 This is a schematic diagram of the structure of the electrically heated vest in Application Example 1; Figure 6 This is a schematic diagram of the structure of the heated car floor mat in Application Example 2; Figure 7 This is a schematic diagram of the structure of the heated door skin for automobiles in Application Example 3.

[0019] In the figure: 1. Lower substrate; 2. Carbon nanotube membrane; 3. Copper foil conductor; 4. Upper substrate; 5. Wire; 200. Flexible carbon-based heating element. Detailed Implementation

[0020] It should be noted that the following detailed descriptions are illustrative and intended to provide further explanation of this application. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains.

[0021] It should be noted that the terminology used herein is for the purpose of describing particular implementations only and is not intended to limit the exemplary implementations according to this application. As used herein, the singular form includes the plural form unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this description, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0022] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0023] Firstly, such as Figure 1 As shown, the present invention provides a flexible carbon-based heating component, including an upper substrate 4 and a lower substrate 1 disposed on the upper and lower sides, with a heating layer provided between the upper substrate 4 and the lower substrate 1; The heating layer includes a carbon nanotube film 2, with copper foil conductors 3 connected to both ends of the carbon nanotube film 2 via conductive paste, and copper foil conductors 3 connected to wires 5; the carbon nanotube film 2 is a thin film formed by the self-assembly of multi-walled carbon nanotubes with a diameter of 10-50 nm through van der Waals forces, with a film thickness of 12-20 μm and a sheet resistance of 1-15 ohms. The thickness of the flexible carbon-based heating element is 0.2–0.6 mm.

[0024] Both the upper substrate 4 and the lower substrate 1 are made of polyimide film; the conductive paste is conductive silver paste.

[0025] The thickness of the upper substrate 4 is 0.17–0.21 mm, and the thickness of the lower substrate 1 is 0.17–0.21 mm.

[0026] The copper foil conductor 3 is a rolled copper foil with a thickness of 18-35 μm and a width of 8-15 mm.

[0027] Secondly, such as Figure 2 As shown, the present invention also provides a method for preparing the above-mentioned flexible carbon-based heating component, which specifically includes the following steps: Step S1: According to production requirements, cut the upper substrate 4, lower substrate 1, carbon nanotube film 2 and copper foil conductor 3 to the target size; Step S2: A copper foil conductor 3 is attached to the upper surface of the lower substrate 1; Step S3: Screen print conductive paste onto the surface of copper foil conductor 3. The printing amount of conductive paste is 50g / m. 2 ; Step S4: Align and attach the two ends of the carbon nanotube membrane 2 with the conductive paste; Step S5: Lay the upper substrate 4 on the upper surface of the carbon nanotube membrane 2, and then seal the edges of the upper substrate 4 and the lower substrate 1 by hot pressing to encapsulate the heating layer inside. Step S6: Solder wire 5 onto copper foil conductor 3. Wire 5 passes through upper substrate 4 and connects to copper foil conductor 3. Apply insulating adhesive to the solder joint and attach insulating tape. Step S7: Test the resistance and heating performance. Qualified products are finished flexible carbon-based heating components.

[0028] In step S2, the copper foil conductor 3 is bonded to the lower substrate 1 by an adhesive, wherein the adhesive is an epoxy resin adhesive.

[0029] In step S5, the pressure of hot pressing is 0.8 to 1.5 MPa, the temperature is 140 to 160°C, and the pressing time is 30 to 50 seconds.

[0030] In step S6, the insulating adhesive is preferably room temperature curing silicone rubber, and the insulating cloth is black acetate cloth.

[0031] Thirdly, the present invention also provides the application of the flexible carbon-based heating component in smart clothing, car seat heating, medical devices, and portable heat preservation equipment, specifically in electrically heated vests, car heated floor mats, and car heated door panels.

[0032] Example 1 The flexible carbon-based heating component of this embodiment includes an upper substrate 4 and a lower substrate 1 disposed on the upper and lower sides, with a heating layer provided between the upper substrate 4 and the lower substrate 1. The heating layer includes a carbon nanotube film 2, with copper foil conductors 3 connected to both ends of the carbon nanotube film 2 via conductive paste, and copper foil conductors 3 connected to wires 5; the carbon nanotube film 2 is a thin film formed by the self-assembly of multi-walled carbon nanotubes with a diameter of 10-50 nm through van der Waals forces, with a film thickness of 15 μm and a sheet resistance of 3 ohms. The flexible carbon-based heating element has a thickness of 0.4 mm.

[0033] Both the upper substrate 4 and the lower substrate 1 are made of polyimide film with a thickness of 0.18 mm; the conductive paste is conductive silver paste.

[0034] The copper foil conductor 3 is made of rolled copper foil with a thickness of 25μm and a width of 10mm.

[0035] The fabrication process of the flexible carbon-based heating element in this embodiment is as follows: Step S1: According to the design drawings, laser cut out the polyimide film (as the upper substrate 4 and the lower substrate 1), carbon nanotube film 2 and rolled copper foil strip of the required size.

[0036] Step S2: Apply a thin layer of epoxy resin to the predetermined position on the lower substrate 1, flatly attach the copper foil conductor 3, and apply slight pressure to fix it. Step S3: Using a screen printing machine, print conductive silver paste on the area of ​​the copper foil conductor 3 where the carbon nanotube film 2 needs to be connected, control the wet film thickness so that the dry film weight is about 50g / m², and then place it in an 80℃ oven for pre-curing for 10 minutes. Step S4: Pick up the cut carbon nanotube film 2 with a precision jig, align its two ends accurately and press them onto the printed and pre-cured conductive silver paste areas on both sides.

[0037] Step S5: Cover with substrate 4 and send it into a flatbed hot press; set the hot pressing parameters as follows: pressure 1.0MPa, temperature 150℃, holding time 30 seconds; after hot pressing, the edges of the upper and lower substrates are fused to form a strong sealing edge.

[0038] Step S6: Use a soldering iron to solder the high-temperature resistant wire 5 to the protruding end of the copper foil conductor 3. Apply a layer of silicone rubber insulating adhesive to the solder joint and surrounding area, and after it is surface dry, apply a small piece of polyimide insulating tape for reinforcement protection.

[0039] Step S7: Use a multimeter to measure the resistance of the component and test its surface temperature distribution and heating curve under the specified voltage; the component with stable resistance and uniform heating is a qualified finished product.

[0040] Example 2 The flexible carbon-based heating element in this embodiment has a total thickness of 0.35 mm. The upper substrate 4 and lower substrate 1 are both made of flexible polyester (PET) films with a thickness of 0.15 mm. The carbon nanotube film has a thickness of 12 μm. The copper foil conductor has a thickness of 18 μm and a width of 8 mm. The hot-pressing parameters are: pressure 0.8 MPa, temperature 160°C, and time 30 seconds.

[0041] The flexible carbon-based heating element in this embodiment is used in environments where flexibility requirements are not high and heating at low temperatures is required.

[0042] Example 3 The flexible carbon-based heating element in this embodiment has a total thickness of 0.3 mm. The upper substrate 4 and lower substrate 1 are both made of 0.1 mm thick polyester fabric. The carbon nanotube film is 12 μm thick. The copper foil conductor is 18 μm thick and 10 mm wide. The hot-pressing parameters are: pressure 1.2 MPa, temperature 160°C, and time 40 seconds. This solution is suitable for applications requiring high flexibility, comfort, and rigidity.

[0043] Comparative Example 1 This comparative example uses a traditional carbon fiber heating film.

[0044] The flexible carbon-based heating element prepared in Example 1 and the carbon fiber heating film of Comparative Example 1 were subjected to the following tests: (1) Heating rate performance The sample resistance of the flexible carbon-based heating element is 12.6 ohms, U is 13.5V, I is 1.07A, and the total power is 14.44W.

[0045] The carbon fiber heating film sample has a resistance of 12.7 ohms, a voltage of 13.5V, a current of 1.06A, and a power of 14.31W.

[0046] The test results of the heating rate for both are shown in Table 1.

[0047] Table 1 Test results of Example 1 and Comparative Example 1

[0048] As shown in Table 1, the flexible carbon-based heating element prepared in Example 1 has a significantly improved heating rate compared to the traditional carbon fiber heating film.

[0049] (2) Tests on bending resistance and water washing resistance The flexible carbon-based heating element prepared in Example 1 was bent 180°, and the test results are as follows: Figure 3 As shown.

[0050] Depend on Figure 3 It can be seen that after performing more than 20,000 180-degree bends with a radius of 5 mm on Example 1, the resistance change rate is less than 5%, indicating that it has excellent dynamic reliability.

[0051] The flexible carbon-based heating element prepared in Example 1 was subjected to a water washing test, and the test results are as follows: Figure 4 As shown.

[0052] Depend on Figure 4 It can be seen that the heating effect remained effective after 27 water washing tests on Example 1.

[0053] (3) High voltage breakdown test When AC 500V voltage was applied to the component of Example 1 for 60 seconds, no breakdown occurred, and the insulation strength met the safety specifications.

[0054] In summary, this invention, through a unique structural design of "conductive paste connection + thermo-press encapsulation" and corresponding processes, has successfully produced a high-performance flexible ultra-thin planar heating component, which has broad application prospects in fields such as smart clothing, car seat heating, medical devices, and portable insulation equipment.

[0055] Application Example 1 The flexible carbon-based heating element 200 prepared according to this invention is applied to an electrically heated vest, with the specific structure as follows: Figure 5 As shown.

[0056] Application Example 2 The flexible carbon-based heating element 200 prepared by this invention is applied to a heated car floor mat, and the specific structure is as follows: Figure 6 As shown.

[0057] Application Example 3 The flexible carbon-based heating element 200 prepared according to this invention is applied to a heated door panel for automobiles, and the specific structure is as follows: Figure 7 As shown.

[0058] 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 therein. Such 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 flexible carbon-based heat generating assembly, characterized by: It includes an upper substrate (4) and a lower substrate (1) arranged vertically, with a heating layer between the upper substrate (4) and the lower substrate (1); The heating layer includes a carbon nanotube membrane (2), with copper foil conductors (3) connected to both ends of the carbon nanotube membrane (2) through conductive paste, and wires (5) connected to the copper foil conductors (3); the carbon nanotube membrane (2) is a thin film formed by the self-assembly of multi-walled carbon nanotubes with a diameter of 10-50 nm through van der Waals forces, with a film thickness of 12-20 μm and a sheet resistance of 1-15 ohms; The thickness of the flexible carbon-based heating element is 0.2–0.6 mm.

2. The flexible carbon-based heat generating assembly of claim 1, wherein: Both the upper substrate (4) and the lower substrate (1) are made of polyimide film; the conductive paste is conductive silver paste.

3. The flexible carbon-based heat generating assembly of claim 1, wherein: The thickness of the upper substrate (4) is 0.17-0.21 mm, and the thickness of the lower substrate (1) is 0.17-0.21 mm.

4. The flexible carbon-based heat generating assembly of claim 1, wherein: The copper foil conductor (3) is a rolled copper foil with a thickness of 18-35 μm and a width of 8-15 mm.

5. A method for preparing a flexible carbon-based heating component as described in any one of claims 1 to 4, characterized in that: The preparation method specifically includes the following steps: Step S1: According to production requirements, cut the upper substrate (4), lower substrate (1), carbon nanotube film (2) and copper foil conductor (3) to the target size; Step S2: A copper foil conductor (3) is attached to the upper surface of the lower substrate (1); Step S3, silk screen printing conductive paste on the surface of the copper foil conductor (3), the printing amount of the conductive paste is 50 g / m 2 ; Step S4: Align and attach the two ends of the carbon nanotube membrane (2) with the conductive paste; Step S5: Lay the upper substrate (4) on the upper surface of the carbon nanotube membrane (2), and then seal the edges of the upper substrate (4) and the lower substrate (1) by hot pressing to encapsulate the heating layer inside. Step S6: Weld wires (5) onto the copper foil conductor (3), with the wires (5) passing through the upper substrate (4) and connecting to the copper foil conductor (3); apply insulating adhesive to the weld and attach insulating tape; Step S7: Test the resistance and heating performance. Qualified products are finished flexible carbon-based heating components.

6. The method for preparing the flexible carbon-based heating component according to claim 5, characterized in that: In step S2, the copper foil conductor (3) is bonded to the lower substrate (1) by an adhesive, which is an epoxy resin adhesive.

7. The method for preparing the flexible carbon-based heating component according to claim 5, characterized in that: In step S5, the pressure of hot pressing is 0.8–1.5 MPa, the temperature is 140–160°C, and the pressing time is 30–50 seconds.

8. The method for preparing the flexible carbon-based heating component according to claim 5, characterized in that: In step S6, the insulating adhesive is preferably room temperature curing silicone rubber, and the insulating tape is black acetate tape.

9. An application of the flexible carbon-based heating component as described in any one of claims 1 to 4, characterized in that: Applications of the flexible carbon-based heating element in smart clothing, car seat heating, medical devices, and portable insulation equipment.

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