A method for preparing a flexible electric heating element

Abstract

This invention relates to a method for preparing a flexible electric heating element, comprising the following steps: S1, mixing an organic polymer matrix, conductive filler, and solvent to obtain a mixed slurry; S2, coating the mixed slurry onto the surface of an electrode layer, irradiating to shape it, and forming a heating layer; S3, etching the heating layer to obtain an etched electrode layer; S4, stacking insulating layers on the upper and lower surfaces of the heating layer-electrode layer composite, and then welding electrode leads to obtain the flexible electric heating element. The flexible electric heating element prepared by this invention has a multi-layer structure. The main heating layer is an organic-inorganic composite material, with an organic polymer as the matrix and inorganic materials as conductors to form the heating layer; an electrode layer covers the surface of the heating layer; the insulating layer is an insulating film, stacked on the upper and lower surfaces of the electrode layer and the heating layer. Due to the high intrinsic thermal conductivity of zinc oxide and the continuous thermally conductive network formed on the surface of barium titanate, the interfacial thermal resistance is effectively reduced, constructing an efficient heat conduction pathway.

Description

Technical Field

[0001] This invention relates to the field of electric heating technology, and specifically to a method for preparing a flexible electric heating element. Background Technology

[0002] Aerospace systems must mount a large number of electric heating devices to maintain the optimal operating temperature range of specific components. As electric heating systems continue to develop towards lightweight, low power consumption and intelligence, higher requirements are placed on the weight, power consumption, design flexibility and stability of electric heating devices.

[0003] Most existing flexible electric heaters are based on constantan or nickel-chromium metal resistance wires. Only one metal wire is needed to generate heat. They are covered with an insulating film for insulation protection. Therefore, traditional metal wire electric heating films have low cost. However, they require a lot of auxiliary equipment at the back end, resulting in a high cost of the overall temperature control system. Furthermore, during operation, they require external controllers, sensors, overheat protection wires, cables, voltage equipment, etc. to work together. They are large and heavy, complex in composition, consume a lot of power, and are subject to risks such as wire breakage failure and thermal runaway.

[0004] Therefore, there is an urgent need to develop a new type of flexible electric heating material. Summary of the Invention

[0005] To address the aforementioned problems in the prior art, this invention provides a method for preparing a flexible electric heating element, particularly a method for preparing a flexible electric heating element and controlling its performance.

[0006] The objective of this invention can be achieved through the following methods: This invention provides a method for preparing a flexible electric heating element, comprising the following steps: S1. Mix the organic polymer matrix, conductive filler, and solvent to obtain a mixed slurry; S2. The mixed slurry is coated onto the surface of the electrode layer and irradiated to set the shape, forming a heating layer; S3. The heating layer is etched to obtain the etched electrode layer, forming a heating layer-electrode layer composite. S4. An insulating layer is stacked on the upper and lower surfaces of the heating layer-electrode layer composite, and then electrode leads are welded to obtain a flexible electric heating element.

[0007] Furthermore, in step S1, the organic polymer includes one or more of phenyltrichlorosilane, diphenyldichlorosilane, and methylphenyldichlorosilane, with phenyltrichlorosilane being more preferably preferred. Phenylexatrichlorosilane has the best overall performance; its crosslinking density, thermal stability, and compatibility with the irradiation process are suitable for the preparation method of this invention.

[0008] Furthermore, in step S1, the conductive filler has a core-shell structure, with barium titanate as the core and zinc oxide as the shell. Zinc oxide coats the surface of the spherical barium titanate. The mass ratio of barium titanate to zinc oxide is 40–60:40–60, preferably 40–50:50–60. The barium titanate particle size is 100–200 nm.

[0009] The conductive filler used in this invention is a composite material of two inorganic fillers with different properties. The two fillers have different physical characteristics: barium titanate, with large particle size and poor conductivity, serves as the "insulating foundation" of the system; and zinc oxide, with a small particle size forming a shell, has high conductivity. This core-shell structure conductive filler can reduce the percolation threshold to approximately 18 vol%. Replacing it with "similar" fillers such as SrTiO3, TiO2, or ITO would result in a sharp drop in performance due to insufficient dielectric loss, excessively high resistivity, or cost / contamination issues. The continuous ZnO network simultaneously conducts electricity and partially conducts heat, constructing a current path and guiding the BaTiO3 grain boundary hotspots to the metal foil, but macroscopic heat homogenization still relies on the metal electrodes.

[0010] Furthermore, in step S1, the conductive filler is barium titanate dispersed in a Zn-containing medium. 2+ The alcohol-water solution is obtained by hydrolyzing with ammonia or urea, filtering and drying, and then ultrasonic treatment.

[0011] Barium titanate, containing Zn 2+ The ratio of alcohol to aqueous solution is 40-60g:200ml.

[0012] Contains Zn 2+ In alcohol-water solutions, Zn 2+ The concentration is 2.4-3.7 mol / L.

[0013] The volume ratio of alcohol to water is 1:0.8-1.2.

[0014] Mixing was performed at high speed at 15,000–35,000 r / min for 1–10 min.

[0015] The mass ratio of barium titanate to ammonia or urea is 40-60:10.

[0016] The hydrolysis temperature is 50–80 °C, and the time is 10–50 min. Hydrolysis utilizes the slow decomposition of urea or ammonia water under heating conditions to produce OH-. - , making Zn 2+ The uniform precipitation of Zn(OH)2 on the surface of barium titanate and its conversion to ZnO achieves a core-shell structure coating; this is the core process for forming the core-shell structure, ensuring the dispersibility of the filler, and achieving a low permeation threshold and high stability.

[0017] The ultrasonic treatment temperature is 60~80 ℃, the frequency is 20~50 kHz, and the time is 10~20 h.

[0018] In the preparation of conductive fillers, the Zn-containing materials used 2+ Alcohol-water solution: Provides zinc ions. By controlling the alcohol-water mixed solvent, it promotes the uniform adsorption of zinc ions on the barium titanate surface, laying the foundation for subsequent heterogeneous nucleation. Hydrolysis with ammonia or urea: Slow hydrolysis with alkaline substances produces OH-. - To achieve Zn 2+ Controllable precipitation on the surface of barium titanate forms a uniform and dense ZnO coating layer, which is achieved by adjusting the Zn²⁺ concentration in the solution. + The concentration of barium titanate / zinc oxide can be controlled to adjust the amount of zinc oxide coating, thereby obtaining core-shell structured fillers with different barium titanate / zinc oxide mass ratios. Ultrasonic treatment: After filtration and drying, ultrasonic treatment further disperses the core-shell structured particles and promotes the densification of the coating layer, ultimately obtaining a highly dispersible and highly stable conductive filler.

[0019] Furthermore, in step S1, the solvent is one or more of xylene, N-methylpyrrolidone (NMP), and diethylene glycol butyl ether acetate.

[0020] Furthermore, in step S1, the mass ratio of the organic polymer matrix, conductive filler, and solvent is 30–60:30–60:10.

[0021] Furthermore, in step S1, the mixing method is ultrasonic mixing. The frequency of the ultrasound is 40~60kHz, the temperature during ultrasonic mixing is 60~80℃, and the time is 10~20 h.

[0022] Furthermore, in step S2, the electrode layer is a metal thin film with a thickness of 12~50μm. The metal thin film includes one of aluminum foil, tin foil, and copper foil.

[0023] Furthermore, in step S2, the temperature is set to 100~150℃ during the coating process, and the temperature is maintained for 30~60 minutes after coating.

[0024] Furthermore, in step S2, the irradiation shaping is performed using a low-energy electron beam, with an absorbed irradiation dose of 50~200kGy and a duration of 100~120s.

[0025] Furthermore, in step S2, the thickness of the heating layer is 100μm ~ 200μm.

[0026] Compared to the long time required for curing and crosslinking under normal temperature and pressure, during which incomplete reactions and difficulties in curing may occur, the irradiation shaping of this invention is a physically controllable instantaneous energy intervention, which has high process controllability, material performance consistency, and ability to form complex structures.

[0027] Furthermore, in step S3, the electrode etching method is wet etching. The electrode etching temperature is 40–70°C.

[0028] During the etching process, hydrogen ions in the acidic solution react with the oxides on the surface of the aluminum foil to generate soluble salts, thereby removing the oxide layer on the surface of the aluminum foil and improving its roughness. This can eliminate defects and contamination and enhance the adhesion of subsequent processes.

[0029] Furthermore, in step S3, insulating layers are applied to the top and bottom of the etched electrode layer for insulation of the heating element; electrode leads are then welded to the electrode positions of the heating layer after the insulating layers are stacked. Both the upper and lower insulating layers are polyimide films.

[0030] The principle of the heating layer of this invention: Organic polymers, such as phenyltrichlorosilane, are cross-linked by electron beam to form a flexible insulating framework. In the core-shell BaTiO3 / ZnO filler, BaTiO3 provides high dielectric loss and polarization heat, while ZnO acts as the main current channel and amplifies Joule heating in the percolation network. The two work together to form a "dielectric-semiconductor positive feedback", which enables the sheet to heat up rapidly within seconds under low voltage.

[0031] While existing technologies include carbon-based, metal-based, or ceramic-semiconductor network heating plates, this invention is the first to combine a ferroelectric-semiconductor core and shell with electron beam crosslinked siloxane to achieve rapid and uniform heating of a low-voltage flexible thin film, which differs from existing technologies.

[0032] The present invention also provides a flexible electric heating element obtained by the preparation method described above. The performance of the flexible electric heating element is controlled by adjusting the ratio of the organic matrix to the conductive filler and the ratio of barium titanate to zinc oxide.

[0033] The flexible electric heating element can be adjusted within a wide range of resistance and heating temperature, with a resistance range of 10. 1 ~10 5 Ω, heating temperature range is 45~110℃.

[0034] Compared with the prior art, the present invention has the following beneficial effects: (1) In the organic matrix, due to the high intrinsic thermal conductivity of zinc oxide (about 60 W / (m·K)) and the continuous thermally conductive network formed on the surface of barium titanate, the interfacial thermal resistance is effectively reduced, and an efficient heat conduction pathway is constructed.

[0035] (2) Barium titanate is a typical ferroelectric material and is an excellent insulator (high resistivity). Its addition ensures that the composite material can maintain extremely high volume resistivity even when working under high voltage or high frequency electric fields, preventing current leakage and breakdown risks. Its role is as the "insulating foundation" of the system. However, traditional barium titanate is prone to a sharp increase in system viscosity when added at high amounts, resulting in problems such as thickening during stirring and difficulty in molding. Zinc oxide is uniformly coated on the surface of barium titanate to form a stable core-shell structure. This structure significantly improves the compatibility between the filler and the organic matrix, making the composite material exhibit "thinning during stirring" behavior. Even at ultra-high filling amounts, it can still maintain good fluidity and processability, solving the contradiction between the processability and performance of high thermal conductivity materials (barium titanate itself is not a "high thermal conductivity" material, and its room temperature bulk thermal conductivity is only about 2-4 W / m). -1 K -1 The thermal conductivity is much lower than that of typical thermally conductive fillers such as boron nitride, alumina, and silicon nitride. It mainly utilizes its high dielectric constant to improve the thermal conductivity of the composite system by 30%-150% through surface modification or coating with a high thermal conductivity phase (such as BN, ZnO, or graphene). However, the thermal conductivity of the composite system is still determined by the introduced thermally conductive phase, rather than barium titanate itself.

[0036] (3) Both zinc oxide and barium titanate are inorganic ceramic materials, possessing the excellent properties common to ceramics: high melting point, high hardness, corrosion resistance, and stable physicochemical properties at high temperatures. Furthermore, the preparation process of this composite material is extremely simple; uniform coating of barium titanate with zinc oxide can be achieved through in-situ hydrolysis deposition, with the entire process completed within minutes, significantly improving efficiency compared to traditional ball milling coating (which requires more than 3 hours). In addition, the raw materials used (zinc oxide, barium titanate, and organic matrix) are all mature industrial products, with controllable costs and high process stability, providing the foundation for large-scale industrial applications. This efficient and low-cost preparation path provides a feasible solution for the large-scale production of high-end thermal conductive materials. Detailed Implementation

[0037] The present invention will now be described in detail with reference to specific embodiments. The following examples are implemented under the premise of the technical solution of the present invention, providing detailed implementation methods and specific operating procedures, which will help those skilled in the art to further understand the present invention. It should be noted that the scope of protection of the present invention is not limited to the following embodiments; any adjustments and improvements made under the concept of the present invention are all within the scope of protection of the present invention.

[0038] Example 1 This embodiment provides a method for preparing a flexible electric heating element, the steps of which are as follows: (1) Preparation of core-shell structured conductive fillers: 50g of barium titanate (particle size 100nm) was dispersed in 200ml of an alcohol-water solution containing ZnCl2 (Zn 2+ The solution (concentration 3.07 mol / L, alcohol-to-water volume ratio 1:1) was mixed at 25000 rpm for 3 min, then 10 g of urea was added, and hydrolysis was carried out at 70 °C for 30 min. During the hydrolysis process, the urea slowly decomposed to produce OH-. - , making Zn 2+ Zn(OH)2 is uniformly precipitated on the surface of barium titanate and further dehydrated to form ZnO, forming a continuous coating layer. After the reaction, the mixture is filtered, washed, and dried, and then ultrasonically treated at 70℃ and 40kHz for 10h to obtain a core-shell structured filler (barium titanate:zinc oxide mass ratio of 1:1).

[0039] (2) According to the material formula, weigh 30 parts, 40 parts, and 60 parts of phenyltrichlorosilane, 60 parts, 50 parts, and 30 parts of conductive filler, and 10 parts of xylene respectively by weight ratio using a weighing balance; mix each component by ultrasonic mixing for 10 hours, the ultrasonic mixing frequency is 40 kHz, the ultrasonic temperature is 70 ℃, and the resulting composite material is coated onto the surface of aluminum foil (thickness is 30 μm) by coating, the coating temperature is 150 ℃, and the heat preservation time after coating is 1 hour; (3) The coated slurry is irradiated by electron irradiation (low-energy electron beam, irradiation absorbed dose of 150kGy) for 100s to form a heating layer (thickness of 120μm). (4) Cut the irradiated heating layer to the required size and perform electrode etching by wet etching at a temperature of 60°C. Then, an insulating layer (polyimide film, 50μm thick) is applied to the top and bottom of the etched heating layer-electrode layer composite to insulate the electric heating element. This process is carried out at room temperature and pressure. Finally, electrode leads are welded to the electrode positions of the heating layer after the insulation layer is laminated to make flexible electric heating elements (S1-1, S1-2, S1-3) that can be used for testing. Their electrical properties are shown in Table 1.

[0040] Results: The coating sections S1-1, S1-2, and S1-3 exhibited good leveling properties and a smooth surface free of pinholes. After 50 cycles of power on / off switching, the resistivity change rate was consistently <5%. Taking S1-2 as an example, it heated to 82℃ in 10 seconds at 30V, reaching a steady-state temperature of 105℃, with a power density of 2.1 W·cm³. -2 The sample exhibits a rapid thermal response at low voltage, demonstrating excellent electrothermal performance.

[0041] Example 2 This embodiment provides a method for preparing a flexible electric heating element, the steps of which are as follows: According to the material formula, 40 parts of phenyltrichlorosilane, 50 parts of conductive filler, and 10 parts of xylene were weighed using a weighing balance according to the weight ratio. In this embodiment, the preparation methods of the conductive filler and flexible electric heating element are the same as in Example 1, but the Zn content in the solution is adjusted. 2+ The concentration was adjusted so that the final mass ratio of barium titanate to zinc oxide was 20:30, 25:25, and 30:20 (corresponding to S2-1, S2-2, and S2-3), and the remaining steps were the same as in Example 1.

[0042] The specific composition and electrical properties of the prepared flexible electric heating elements (S2-1, S2-2, S2-3) are shown in Table 1.

[0043] Results: The coating sections S2-1, S2-2, and S2-3 exhibited good leveling properties and a uniform, defect-free surface; the resistance change rate after 50 power-on / off cycles was less than 5%; under 30V, the temperature rise over 10 seconds reached 95℃ (S2-1), 68℃ (S2-2), and 42℃ (S2-3) depending on the barium titanate / zinc oxide ratio, respectively, with steady-state temperatures of 110℃, 74℃, and 47℃, and power densities of 2.4 W·cm³. -2 1.8 W·cm -2 1.2 W·cm -2 All of them have good electrical properties.

[0044] Example 3 This embodiment provides a method for preparing a flexible electric heating element, the steps of which are as follows: The preparation steps of this embodiment are basically the same as those of Example 1 (S1-2), except that phenyltrichlorosilane is replaced with methyltrichlorosilane.

[0045] Results: The S3 coating section had high volatile content and surface pinholes; the resistivity changed by +12% after 50 power cycles; it heated to 68℃ in 10 s at 30V, with a steady-state temperature of 85℃ and a power density of 1.4 W·cm³. -2 . Example 4 This embodiment provides a method for preparing a flexible electric heating element, the steps of which are as follows: The preparation steps of this embodiment are basically the same as those of Example 1 (S1-2), except that phenyltrichlorosilane is replaced with dimethyldichlorosilane.

[0046] Results: The S4 coating section exhibited poor leveling properties and surface pores; the resistivity change rate increased by 26% after 50 power-on / off cycles; the temperature rose to 72 °C in 10 s at 30V, with a steady-state temperature of 88 °C and a power density of 1.5 W·cm³. -2 .

[0047] Conclusion: In summary, although other organic polymer matrices can achieve heating functions, their thermal aging stability (characterized by the rate of change in resistance after 50 cycles of power on and off) is inferior to that of the phenyltrichlorosilane system.

[0048] Comparative Example 1 The preparation steps of this comparative example are basically the same as those of Example 1, with the only difference being: According to the material formula, weigh 30 parts, 40 parts, and 60 parts of phenyltrichlorosilane, 60 parts, 50 parts, and 30 parts of barium titanate, and 10 parts of xylene according to the weight ratio using a weighing balance.

[0049] The specific composition and electrical properties of the prepared flexible electric heating elements (D1-1, D1-2, D1-3) are shown in Table 1.

[0050] Results: The room temperature resistance of D1-1, D1-2, and D1-3 was relatively high, and applying a 30V voltage did not produce a significant electric heating effect. This is because barium titanate itself is a high-resistivity insulator; although it is uniformly distributed in the matrix, it cannot form a conductive path. Therefore, barium titanate needs to be modified or combined with highly conductive materials.

[0051] Comparative Example 2 The preparation steps of this comparative example are basically the same as those of Example 1, with the only difference being: According to the material formula, weigh out 30 parts, 40 parts, and 60 parts of phenyltrichlorosilane, 60 parts, 50 parts, and 30 parts of zinc oxide, and 10 parts of xylene using a weighing balance.

[0052] The specific composition and electrical properties of the prepared flexible electric heating elements (D2-1, D2-2, D2-3) are shown in Table 1.

[0053] Results: The room temperature resistance of the electric heating elements D2-1, D2-2, and D2-3 is relatively low. Applying voltage to the electric heating elements can achieve the electric heating function. However, after 50 on-off cycles, the room temperature resistance of the electric heating elements cannot return to the initial value. This indicates that although the single zinc oxide filler can provide conductivity, its thermal stability is poor, and a second phase (such as barium titanate) needs to be introduced to improve the resistance stability.

[0054] Comparative Example 3 The preparation steps of this comparative example are basically the same as those of Example 1 (S1-2), except that the conductive filler is an equal mass of conductive carbon black.

[0055] Results: Carbon black has a high specific surface area and large surface energy. Its viscosity soars under high-speed mixing. When coated at 150°C, it forms a "jelly"-like gel and cannot be leveled when scraped.

[0056] Comparative Example 4 The preparation steps of this comparative example are basically the same as those of Example 1 (S1-2), except that the conductive filler is an equal mass of tin oxide.

[0057] Result: The intrinsic resistivity of SnO2 is 10. 4 The resistance is Ω·cm, which is two orders of magnitude higher than that of ZnO, and requires 35 vol% to percolate; it can be heated to 48℃ in 10s at 30V; the particle size is similar to that of BaTiO3, but SnO2 has severe agglomeration, and the resistance increases by 30% after 50 cycles of power on and off (D4).

[0058] Comparative Example 5 The preparation steps of this comparative example are basically the same as those of Example 1 (S1-2), except that the conductive filler is an equal mass of strontium titanate.

[0059] Results: The dielectric constant of SrTiO3 is only 1 / 6 that of BaTiO3, and the interfacial polarization loss is significantly reduced; its dielectric loss tanδ decreases from 0.04 in the BaTiO3 system to 0.007, and the power density is 1.1 W·cm⁻¹ when heated from 30V to 58℃ in 10s. -2 .

[0060] Comparative Example 6 The preparation steps of this comparative example are basically the same as those of Example 1 (S1-2), except that the conductive filler is prepared by a simple physical mixing method, namely, 50g of barium titanate (100nm) and 50g of zinc oxide (20nm) are mixed at high speed at 25000r / min for 3min (without hydrolysis coating step), and then ultrasonically mixed with organic polymer and solvent.

[0061] Results: During the mixing process, BaTiO3 and ZnO agglomerated separately. SEM showed that the interfacial gap between the two phases was >100 nm, and the percolation threshold increased to 28 vol% (far higher than the approximately 18 vol% in Example 1). Even after 10 h of ultrasonic treatment, the agglomeration could not be broken up. The coating viscosity was high, and the overall reliability was significantly worse than that of the core-shell structure sample in Example 1.

[0062] Comparative Example 7 (D7) The preparation steps of this comparative example are basically the same as those of Example 1 (S1-2), except that the coated slurry is left to cure and crosslink at room temperature and pressure for 20 hours to form a heating layer.

[0063] Results: The coated section surface was slightly sticky, and the resistivity changed by +19% after 50 power-on / off cycles. The power density was 1.1 W·cm³ after heating to 58 °C (steady-state 79 °C) in 10 seconds at 30V. -2 Room temperature curing is affected by the environment, resulting in low and uneven cross-linking density, which leads to poor electrical stability and mechanical flexibility compared to irradiation curing.

[0064] Table 1. Raw material composition of the heating layer slurry in the examples and comparative examples.

[0065] Test method: (1) Room temperature resistance measurement method: Place the heating element in a room temperature environment and use a multimeter to test the room temperature resistance of the heating element. Then apply a 30V voltage to the heating element and perform 50 on-off cycles. Then test the room temperature resistance of the heating element again with a multimeter. One cycle consists of 1 hour of power-on and 1 hour of power-off.

[0066] (2) Heating temperature measurement method: The heating element is placed in a room temperature environment, a platinum resistance temperature sensor is attached to the surface, a 30V voltage is applied to the heating element, and the surface temperature of the heating element is detected after 10s and 1h of power-on.

[0067] (3) Coating section: Visual inspection; (4) Power density: Measure the effective heating area, calculate P=UI and then divide by the area.

[0068] Table 2 Performance Tests of Heating Layer Slurry in Examples and Comparative Examples

[0069] Compared with traditional metal wires, the heating element of this invention integrates the heating layer, electrode layer, and insulation layer within a thickness of 200µm, eliminating the need for external sensors and complex temperature control circuits, resulting in faster response, finer partitioning, and safer failure modes.

[0070] Compared to carbon black or metal wire systems, the core-shell BaTiO3 / ZnO system of this invention utilizes the high dielectric loss-semiconductor synergistic effect to reach 95°C within 10 seconds at 30V (as in S2-1). Simultaneously, this composite material exhibits a positive temperature coefficient of resistance (PTC) within a certain temperature range, which is beneficial for suppressing thermal runaway; its heating layer also exhibits excellent temperature uniformity. This invention combines low-voltage drive, rapid thermal response, good mechanical flexibility, and overheat self-protection characteristics—significant technical advantages that are difficult to achieve with carbon black or metal wire through dosage control.

[0071] The specific embodiments of the present invention have been described above. It should be understood that the present invention is not limited to the specific embodiments described above, and those skilled in the art can make various modifications or variations within the scope of the claims, which do not affect the essence of the present invention.

Claims

1. A method for preparing a flexible electric heating element, characterized in that, Includes the following steps: S1. Mix the organic polymer matrix, conductive filler, and solvent to obtain a mixed slurry; S2. The mixed slurry is coated onto the surface of the electrode layer and irradiated to set the shape, forming a heating layer; S3. The heating layer is etched to obtain the etched electrode layer, forming a heating layer-electrode layer composite. S4. An insulating layer is stacked on the upper and lower surfaces of the heating layer-electrode layer composite, and then electrode leads are welded to obtain a flexible electric heating element. In step S1, the conductive filler has a core-shell structure, with barium titanate as the core and zinc oxide as the shell.

2. The preparation method according to claim 1, characterized in that, In step S1, the organic polymer includes one or more of phenyltrichlorosilane, diphenyldichlorosilane, and methylphenyldichlorosilane.

3. The preparation method according to claim 1, characterized in that, In the conductive filler of step S1, the mass ratio of barium titanate to zinc oxide is 40-60:40-60.

4. The preparation method according to claim 1, characterized in that, In step S1, the conductive filler is prepared by dispersing barium titanate in a Zn²⁺-containing medium. + In an alcohol-water solution, ammonia or urea is added to initiate a hydrolysis reaction, causing Zn²⁺ to react with the solution. + It is converted into ZnO and coated on the surface of barium titanate, then filtered, dried and ultrasonically treated to obtain the final product.

5. The preparation method according to claim 1, characterized in that, In step S1, the solvent is one or more of xylene, N-methylpyrrolidone, and diethylene glycol butyl ether acetate.

6. The preparation method according to claim 1, characterized in that, In step S1, the mass ratio of the organic polymer matrix, conductive filler, and solvent is 30-60:30-60:

10.

7. The preparation method according to claim 1, characterized in that, In step S2, the electrode layer is a metal thin film with a thickness of 12~50μm; the metal thin film includes one of aluminum foil, tin foil, and copper foil.

8. The preparation method according to claim 1, characterized in that, In step S2, the thickness of the heating layer is 100μm~200μm.

9. The preparation method according to claim 1, characterized in that, In step S2, irradiation shaping is performed using a low-energy electron beam with an absorbed dose of 50-200 kGy and a duration of 100-120 s.

10. A flexible electric heating element obtained by the preparation method as described in claim 1.

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