Composite electrothermal film suitable for high-temperature heating and preparation method thereof

Abstract

The invention relates to the field of electric heating devices, and discloses a composite electrothermal film suitable for high-temperature heating, which comprises a composite heating layer and packaging layers arranged on two sides of the composite heating layer, the composite heating layer comprises an electric heating composite film and end electrodes arranged on the two sides of the electric heating composite film, the electric heating composite film comprises electric heating film slurry and a heat-resistant substrate, and the electric heating film slurry comprises polyamide acid, glass fibers, conductive carbon black and an N-N dimethylacetamide solution. According to the invention, the electrothermal film comprising the composite heating layer and the packaging layer is designed, and the composite heating layer is used as an effective heating area, so that the high-temperature stability of the electrothermal film can be improved; the packaging layer protects the electrothermal film from being influenced by the environment, and the durability and the safety are enhanced; effective heating and current conduction of the electrothermal film are ensured by the electrothermal composite film and the terminal electrode in the composite heating layer; compared with a traditional metal conductive material, especially a heavy metal material, the whole structure is more environment-friendly.

Description

Technical Field

[0001] The invention relates to the field of electric heating devices, and in particular to a composite electric heating film suitable for high-temperature heating and a preparation method thereof. Background Art

[0002] With the continuous advancement of modern industrial technology and science, electric heating materials are widely used in many fields, including chemical industry, electronic equipment manufacturing, automobile industry, aerospace, and smart home, due to their high efficiency, convenience, and energy saving. In these application scenarios, electric heating film, as a new type of heating material, gradually replaces traditional heating elements such as metal heating wires and ceramic heating sheets with its advantages of lightness, flexibility, and efficient and uniform heating. However, with the increasing market demand for high-temperature heating, the performance limitations of existing electric heating films in high-temperature environments are gradually emerging.

[0003] The base materials of existing electric heating films are mainly polyester (PET) or ordinary polymers, which have low heat resistance and can usually only work below 150°C, making it difficult to meet the requirements of material stability and safety in high-temperature heating scenarios (such as 300°C and above). At the same time, the stability is poor in high-temperature environments, which seriously affects the heating efficiency and service life. Therefore, the development of a composite electric heating film that can work stably for a long time in a high-temperature environment not only has important industrial application value, but also has important significance for promoting the upgrading of high-temperature heating technology. Summary of the invention

[0004] The present invention is to solve the deficiencies in the prior art. One of the purposes of the present invention is to provide a composite electric heating film material based on polyacrylic acid (PAA) / glass fiber / conductive carbon black for high-temperature heating. The composite electric heating film material is composed of polyacrylic acid (PAA), glass fiber and conductive carbon black. Compared with ordinary electric heating film materials, it has better high temperature resistance and safety; the second purpose of the present invention is to provide a preparation method of the composite electric heating film material based on polyacrylic acid (PAA) / glass fiber / conductive carbon black for high-temperature heating.

[0005] In order to achieve the above object, the present invention adopts the following technical solutions: In the first aspect, the present invention provides a composite electric heating film suitable for high-temperature heating, comprising a composite heating layer and an encapsulation layer arranged on both sides of the composite heating layer; the composite heating layer comprises an electric heating composite membrane sheet and end electrodes arranged on both sides of the electric heating composite membrane sheet, the electric heating composite membrane sheet comprises an electric heating film slurry and a heat-resistant substrate, the electric heating film slurry comprises polyamic acid, glass fiber, conductive carbon black and NN dimethylacetamide.

[0006] Preferably, the electrothermal film slurry comprises 10 to 30 parts by weight of polyamic acid, 1 to 5 parts by weight of glass fiber, 5 to 10 parts by weight of conductive carbon black and 60 to 80 parts by weight of NN dimethylacetamide.

[0007] Preferably, the encapsulation layer is polyimide.

[0008] Preferably, the heat-resistant substrate includes one or more of polyimide, polytetrafluoroethylene, a ceramic substrate, a stainless steel substrate, and a metal substrate.

[0009] Preferably, the film thickness of the composite electric heating film is 10 μm to 150 μm.

[0010] Preferably, the terminal electrode is made of one or more of copper, aluminum or nickel.

[0011] Preferably, the encapsulation layer has a thickness of 10 μm to 150 μm.

[0012] In a second aspect, the present invention provides a method for preparing a composite electric heating film suitable for high temperature heating, characterized in that it comprises the following steps: S1: dropping polyamic acid into NN dimethylacetamide solution to prepare PAA-DMAc glue; S2: adding an appropriate amount of glass fiber and conductive carbon black to the PAA-DMAc glue prepared in step S1, and mixing the filler and the PAA-DMAc glue thoroughly and evenly by mechanical stirring to form an electric heating film slurry; S3: uniformly coating the electric heating film slurry prepared in step S2 on the surface of the substrate by a slurry scraping method, and forming a composite electric heating film after high-temperature curing; S4: placing the terminal electrodes on the surface of the composite electric heating film prepared in step S3, and packaging it using a plastic packaging machine. Preferably, the curing temperature in S3 is in the range of 60 to 200°C.

[0013] Preferably, the curing time in S3 is 2-12 hours.

[0014] Compared with the prior art, the present invention has the following beneficial effects: By designing an electric heating film including a composite heating layer and a packaging layer, the composite heating layer serves as an effective heating area, which can improve the high-temperature stability of the electric heating film; the packaging layer protects the electric heating film from environmental influences, thereby enhancing durability and safety; the electric heating composite diaphragm and end electrodes in the composite heating layer ensure effective heating and current conduction of the electric heating film, while the packaging layer provides additional protection; the entire structure is more environmentally friendly than traditional metal conductive materials, especially heavy metal materials.

[0015] Furthermore, through a specific ratio of ingredients (polyamic acid, glass fiber, conductive carbon black and NN dimethylacetamide solution), it is ensured that an electric heating film with excellent electrothermal properties and mechanical strength is prepared while maintaining flexibility.

[0016] Furthermore, polyimide, as a high-performance polymer, has excellent heat resistance, mechanical strength, insulation and chemical stability, so as an encapsulation layer, it can significantly improve the durability, high temperature stability and electrical insulation performance of the electric heating film.

[0017] Furthermore, the selection of a variety of heat-resistant substrate materials (such as polyimide, polytetrafluoroethylene, ceramic substrate, stainless steel substrate, metal substrate) improves the overall temperature resistance and chemical stability of the composite electric heating film, allowing the electric heating film to adapt to different application scenarios and temperature requirements.

[0018] Furthermore, the specific film thickness range (10μm to 150μm) ensures that the electric heating film has sufficient strength and conductivity, and is also conducive to uniform distribution and conduction of heat.

[0019] Furthermore, using copper, aluminum or nickel metal as the material of the terminal electrode can provide good conductivity and mechanical strength, ensuring the stability and reliability of the electric heating film during operation.

[0020] Furthermore, a specific encapsulation layer thickness (10 μm to 150 μm) can protect the electric heating film without affecting its heating efficiency and thermal conductivity; control of the encapsulation layer thickness helps to ensure the encapsulation effect without affecting the flexibility of the electric heating film while providing adequate protection.

[0021] On the other hand, from the perspective of the preparation method, the present invention prepares the electric heating film slurry by mixing the organic high molecular polymer, the electric heating material and the organic solvent, and then applies it on the surface of the heat-resistant substrate by the doctor blade method and cures it at high temperature, and finally uses a plastic sealing machine to package it to form a composite electric heating film. This method can prepare a uniform, dense composite electric heating film with good electric heating performance, and the operation process is relatively simple and suitable for large-scale production.

[0022] Furthermore, the specific curing temperature range (60-200°C) ensures that the electric heating film slurry can be fully cross-linked and fully cured during the curing process to form a continuous and uniform film layer and a stable electric heating film structure, while avoiding the adverse effects of excessively high temperatures on the performance of the electric heating film.

[0023] Furthermore, the appropriate curing time (2-12h) ensures that the electric heating film slurry has enough time to undergo cross-linking reaction during the curing process, thereby obtaining an electric heating film product with a complete film layer and stable performance. At the same time, a reasonable curing time can also improve production efficiency and reduce costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] The drawings described herein are only for explanation purposes and are not intended to limit the scope of the present invention in any way. In addition, the shapes and proportional dimensions of the components in the drawings are only for illustration purposes to help understand the present invention and are not intended to specifically limit the shapes and proportional dimensions of the components of the present invention. In the drawings: Figure 1 A schematic diagram of a composite electric heating film suitable for high temperature heating obtained in Example 1; Figure 2 The temperature-time curve of the composite electric heating film suitable for high temperature heating obtained in Example 1 under a DC voltage of 12V; Among them, 1. packaging layer; 2. composite heating layer; 3. terminal electrode; 4. heat-resistant substrate. DETAILED DESCRIPTION

[0025] In order to enable those skilled in the art to better understand the technical solutions in the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the present invention.

[0026] It should be noted that when an element is referred to as being "disposed on" another element, it may be directly on the other element or there may be a central element. When an element is considered to be "connected to" another element, it may be directly connected to the other element or there may be a central element at the same time. The terms "vertical", "horizontal", "left", "right" and similar expressions used herein are for illustrative purposes only and are not intended to be the only embodiment.

[0027] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art to which the present invention belongs. The terms used herein in the specification of the present invention are only for the purpose of describing specific embodiments and are not intended to limit the present invention. The term "and / or" used herein includes any and all combinations of one or more of the related listed items.

[0028] Embodiment 1: Embodiment 1 provides a composite electric heating film suitable for high temperature heating and a preparation method thereof, and the specific steps are as follows: S1, dropping 10 parts by weight of polyamic acid (PAA) into 75 parts by weight of NN dimethylacetamide solution to prepare PAA-DMAc glue; Among them, NN dimethylacetamide solution is used to control the solid content of polyamic acid (PAA).

[0029] S2, adding 5 parts by weight of glass fiber and 10 parts by weight of conductive carbon black to the PAA-DMAc glue prepared in step S1, and mixing the filler and the PAA-DMAc glue thoroughly and evenly by mechanical stirring to form an electric heating film slurry; Among them, the increase of glass fiber improves the heat resistance and enhances the mechanical properties; the increase of conductive carbon black increases the maximum temperature.

[0030] S3, using a slurry coating method to evenly apply the electric heating film slurry prepared in step S2 on the surface of the polyimide substrate, and then curing it at 150° C. for 6 hours to form a composite electric heating film; By adding glass fiber reinforcement materials and optimizing the heat-resistant substrate 4 selection (such as polyimide, polytetrafluoroethylene, etc.), the electric heating film is given excellent mechanical properties, which can maintain structural integrity in high temperature environments. At the same time, it has good flexibility and can adapt to complex curved surfaces and diversified application scenarios, making up for the defect of easy brittle cracking of existing rigid substrate materials.

[0031] S4, placing the copper electrode on the surface of the composite electric heating film prepared in step S3, and packaging it using a plastic packaging machine.

[0032] The thickness of the electric heating film in this embodiment is 90 μm. Controlling the film thickness helps to balance the heating efficiency and mechanical strength of the electric heating film. Too thin may affect the strength and durability, while too thick may reduce the heating efficiency. The thickness of the encapsulation layer 1 is 10 μm. Controlling the thickness of the encapsulation layer 1 helps to ensure the encapsulation effect, without affecting the flexibility of the electric heating film, and providing sufficient protection.

[0033] The resistance and electric heating performance of the composite electric heating film for high temperature heating prepared in Example 1 were tested. The resistance was 50 Ω·mm. The electrical performance test was as follows: Figure 2 As shown in the figure, the electric heating film reaches a constant temperature within 80s under a voltage of 40V, and the maximum temperature is 250℃. This test uses an infrared imager and a thermocouple temperature sensor to measure the surface temperature of the electric heating film. The thermocouple sensor can directly contact the surface of the electric heating film to provide more accurate temperature data. The temperature measurement points are selected to cover the core area of ​​the electric heating film, especially at the position of the composite heating layer 2. And multiple temperature measurement points are selected to ensure temperature uniformity and avoid local overheating or temperature deviation.

[0034] With such a short response time, in some industrial processes, such as coating heating and heat treatment, quickly reaching the required temperature can improve production efficiency. The 80s heating time is particularly important for this type of high-efficiency production. The maximum temperature is 250°C, which is the result of the heat exchange between the heat generated by the conductive material of the composite heating layer 2 under the input power and the heat of the surrounding environment to achieve a balance. 250°C In some food industries, such as the catering industry or fast food heating equipment, the electric heating film can quickly provide high temperature for food heating, especially in the heating process that needs to be completed in a short time. The electric heating film that heats up to 250°C within 80 seconds can significantly improve the heating efficiency. Figure 2 As shown in FIG. 1 , the temperature curve shows a platform, and the electric heating film can work stably at the highest temperature. This embodiment also conducts a thermal cycle test, repeatedly heating and cooling the electric heating film to 250°C, and testing its thermal expansion, contraction, and changes in electrical properties. Through multiple thermal cycles, it is proved that the electric heating film can work stably at this temperature without performance degradation due to thermal stress.

[0035] Embodiment 2: Embodiment 2 provides a composite electric heating film suitable for high temperature heating and a preparation method thereof, and the specific steps are as follows: S1, dropping 20 parts by weight of polyamic acid (PAA) into 70 parts by weight of NN dimethylacetamide solution to prepare PAA-DMAc glue; Polyamic acid has good stability at high temperatures and can withstand high temperatures without obvious decomposition or degradation; it has high mechanical strength and toughness and can withstand large external forces without easily breaking; it has excellent electrical insulation properties; polyamic acid has good resistance to most organic solvents and chemicals and is not easily corroded or dissolved; polyamic acid has certain flame retardant properties and is not easy to burn, making it suitable for applications that require fire resistance; polyamic acid can maintain a high degree of transparency under certain conditions and is suitable for the production of transparent conductive films and optical devices; polyamic acid can be formed by solution processing, coating, spraying, etc., and has good processing properties; polyamic acid can be further cross-linked under heating conditions to form polyimide, and this cross-linking process gives the material higher thermal stability and mechanical strength; compared with some traditional polymer materials, polyamic acid has less impact on the environment during production and use, and has certain environmental advantages.

[0036] Polyamic acid (PAA) is used as the core material. Through the composite design with glass fiber and conductive carbon black, the composite electric heating film can work stably for a long time in a high temperature environment above 300°C, and the instantaneous temperature resistance can reach 500°C, which significantly improves the high temperature tolerance of the electric heating film and solves the problem of traditional electric heating films being prone to aging and failure in high temperature environments.

[0037] S2, adding 5 parts by weight of glass fiber and 5 parts by weight of conductive carbon black to the PAA-DMAc glue prepared in step S1, and mixing the filler and the PAA-DMAc glue thoroughly and evenly by mechanical stirring to form an electric heating film slurry; S3, using a slurry scraping method to evenly apply the electric heating film slurry prepared in step S2 on the surface of the ceramic substrate, and then curing it at 150° C. for 6 hours to form a composite electric heating film; S4, placing the copper electrode on the surface of the composite electric heating film prepared in step S3, and packaging it using a plastic packaging machine.

[0038] The thickness of the electric heating film in this embodiment is 100 μm. Controlling the film thickness helps to balance the heating efficiency and mechanical strength of the electric heating film. Too thin may affect the strength and durability, while too thick may reduce the heating efficiency. The thickness of the encapsulation layer 1 is 10 μm. Controlling the thickness of the encapsulation layer 1 helps to ensure the encapsulation effect, without affecting the flexibility of the electric heating film, and providing sufficient protection.

[0039] The composite electric heating film for high temperature heating prepared in Example 2 was tested for resistance and electric heating performance. The resistance was 70 Ω·mm. The electric heating film reached a constant temperature within 70 seconds under a voltage of 40V, with a maximum temperature of 200°C, and could work stably at the maximum temperature.

[0040] Embodiment 3: Example 3 provides a composite electric heating film suitable for high temperature heating and a preparation method thereof, and the specific steps are as follows: S1, dropping 30 parts by weight of polyamic acid (PAA) into 60 parts by weight of NN dimethylacetamide solution to prepare PAA-DMAc glue; S2, adding 5 parts by weight of glass fiber and 5 parts by weight of conductive carbon black to the PAA-DMAc glue prepared in step S1, and mixing the filler and the PAA-DMAc glue thoroughly and evenly by mechanical stirring to form an electric heating film slurry; S3, using a slurry scraping method to evenly apply the electric heating film slurry prepared in step S2 on the surface of the metal substrate, and then curing it at 150° C. for 6 hours to form a composite electric heating film; S4, placing the copper electrode on the surface of the composite electric heating film prepared in step S3, and packaging it using a plastic packaging machine.

[0041] The thickness of the electric heating film in this embodiment is 115 μm. Controlling the film thickness helps to balance the heating efficiency and mechanical strength of the electric heating film. Too thin may affect the strength and durability, while too thick may reduce the heating efficiency. The thickness of the encapsulation layer 1 is 10 μm. Controlling the thickness of the encapsulation layer 1 helps to ensure the encapsulation effect, without affecting the flexibility of the electric heating film, and providing sufficient protection.

[0042] The composite electric heating film for high temperature heating prepared in Example 3 was tested for resistance and electric heating performance. The resistance was 97 Ω·mm. The electric heating film reached a constant temperature within 75 seconds at a voltage of 40V, with a maximum temperature of 175°C, and could work stably at the maximum temperature.

[0043] As a further development of high-temperature heating composite electric heating films, heat-resistant material research and development can be carried out: find or develop new substrate materials, such as high-temperature resistant polymers, ceramic-based composite materials or inorganic non-metallic materials, which must have good stability and mechanical strength at temperatures of 300°C and above; conductive material optimization can also be carried out: the conductive layer in the electric heating film also needs to be able to withstand high temperatures without losing its conductive properties, which may involve the use of high-performance conductive materials such as metal nanowires, carbon nanotubes, graphene, and their good combination technology with the substrate material; multi-layer composites can also be carried out: through the complementary advantages of multi-layer structures and different materials, both The heat resistance of the electric heating film is guaranteed, while its good electrical conductivity and mechanical strength are ensured; thermal stress management can also be carried out: considering the difference in thermal expansion coefficient of the material at high temperature, a structure that can effectively alleviate thermal stress is designed to avoid damage to the electric heating film due to excessive thermal stress; the manufacturing process can also be optimized: improving high-precision coating and printing technology. In order to achieve efficient and uniform heating of the electric heating film, high-precision coating or printing technology is required to accurately control the thickness and distribution of the conductive layer; high-temperature curing technology can also be improved, and a process suitable for material curing in a high-temperature environment is developed to ensure that the electric heating film is structurally stable and its performance is not affected during the high-temperature manufacturing process.

[0044] Many embodiments and many applications beyond the examples provided will be apparent to those skilled in the art upon reading the above description. Therefore, the scope of the present teachings should not be determined with reference to the above description, but rather with reference to the preceding claims and the full scope of equivalents to which such claims are entitled. For the purpose of comprehensiveness, all articles and references, including disclosures of patent applications and publications, are incorporated herein by reference. The omission of any aspect of the subject matter disclosed herein in the preceding claims is not intended to be a disclaimer of such subject matter, nor should it be considered that the applicants did not consider such subject matter to be part of the disclosed inventive subject matter.

[0045] The above content is a further detailed description of the present invention. It cannot be determined that the specific implementation methods of the present invention are limited to these. For ordinary technicians in the technical field to which the present invention belongs, without departing from the concept of the present invention, they can also make several simple deductions or substitutions, which should be regarded as belonging to the protection scope of the present invention determined by the submitted claims.

Claims

1. A composite electric heating film suitable for high temperature heating, characterized in that: It comprises a composite heating layer (2) and a packaging layer (1) arranged on both sides of the composite heating layer (2); the composite heating layer (2) comprises an electric heating composite membrane and terminal electrodes (3) arranged on both sides of the electric heating composite membrane, the electric heating composite membrane comprises an electric heating membrane slurry and a heat-resistant substrate (4), and the electric heating membrane slurry comprises polyamic acid, glass fiber, conductive carbon black and NN dimethylacetamide.

2. A composite electric heating film suitable for high temperature heating according to claim 1, characterized in that: The electric heating film slurry comprises 10 to 30 parts by weight of polyamic acid, 1 to 5 parts by weight of glass fiber, 5 to 10 parts by weight of conductive carbon black and 60 to 80 parts by weight of NN dimethylacetamide.

3. The composite electric heating film suitable for high temperature heating according to claim 1, characterized in that: The encapsulation layer (1) is polyimide.

4. The composite electric heating film suitable for high temperature heating according to claim 1, characterized in that: The heat-resistant substrate (4) includes one or more of polyimide, polytetrafluoroethylene, a ceramic substrate, a stainless steel substrate, and a metal substrate.

5. The composite electric heating film suitable for high temperature heating according to claim 1, characterized in that: The film thickness of the composite electric heating film is 10 μm to 150 μm.

6. The composite electric heating film suitable for high temperature heating according to claim 1, characterized in that: The material of the terminal electrode (3) is one or more of copper, aluminum or nickel.

7. The composite electric heating film suitable for high temperature heating according to claim 1, characterized in that: The thickness of the encapsulation layer (1) is 10 μm to 150 μm.

8. A method for preparing a composite electric heating film suitable for high temperature heating according to any one of claims 1 to 7, characterized in that: The following steps are involved: S1: dropping polyamic acid into NN dimethylacetamide solution to prepare PAA-DMAc glue; S2: adding an appropriate amount of glass fiber and conductive carbon black to the PAA-DMAc glue prepared in step S1, and mixing the filler and the PAA-DMAc glue thoroughly and evenly by mechanical stirring to form an electric heating film slurry; S3: uniformly coating the electric heating film slurry prepared in step S2 on the surface of the substrate by a slurry scraping method, and forming a composite electric heating film after high-temperature curing; S4: placing the terminal electrode (3) on the surface of the composite electric heating film prepared in step S3, and packaging it using a plastic packaging machine.

9. The method for preparing a composite electric heating film suitable for high temperature heating according to claim 8, characterized in that: The curing temperature in S3 is in the range of 60 to 200°C.

10. A method for preparing a composite electric heating film suitable for high temperature heating according to any one of claim 8, characterized in that: The curing time in S3 is 2-12 hours.

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