Polymer-based electrothermal film having sandwich structure, and preparation method therefor

Abstract

The present application provides a polymer-based electrothermal film having a sandwich structure, and a preparation method therefor. The polymer-based electrothermal film having a sandwich structure comprises a base film layer, a first conductive fluid layer coated on the base film layer, a polymer-based conductive layer coated on the first conductive fluid layer, a second conductive fluid layer coated on the polymer-based conductive layer, a heat conductive layer coated on the second fluid conductor layer, and a flame-retardant waterproof layer coated on the heat conductive layer. The first conductive fluid layer, the polymer-based conductive layer, the second conductive fluid layer, the heat conductive layer and the flame-retardant waterproof layer are all prepared by means of a 3D printing method.

Description

A sandwich-structured polymer-based electrothermal film and its preparation method

[0001] Cross-references to related applications

[0002] This application claims priority to Chinese Patent Application No. 202411552412.6, filed on November 1, 2024, entitled "A Sandwich Structure Polymer-Based Electrothermal Film and Its Preparation Method", the entire contents of which are incorporated herein by reference. Technical Field

[0003] This application relates to the field of electrothermal films, specifically a sandwich-structured polymer-based electrothermal film and its preparation method. Background Technology

[0004] An electrothermal film is an electrically driven device that converts electrical energy into heat energy. Specifically, when an electric current is applied to the two ends of the electrodes of the electrothermal film, the Joule effect causes the conductive layer of the electrothermal film, which has a certain resistance, to transfer heat to the environment in the form of thermal radiation, thermal conduction, and thermal convection. Therefore, the essence of an electrothermal film is that its heating performance can be controlled by adjusting the resistance of the conductive layer between the electrodes. At the same time, the distance between the electrodes can also affect the electrothermal characteristics of the electrothermal film.

[0005] Generally, electrothermal films employ two electrode structures: symmetrical electrode structures and sandwich structures. Symmetrical electrode structures result in a larger electrode spacing, leading to higher device resistance, which is detrimental to electrothermal heating. There are three possible solutions: First, improve the resistivity of the conductive layer, typically by adding more conductive agents during fabrication to reduce device resistance. However, this significantly increases raw material costs, and once the resistance reaches a certain level, it becomes difficult to further reduce it, potentially affecting the film-forming properties and mechanical strength. Second, reduce the electrode spacing to shorten the electron transport path. While this method can significantly improve device resistance, the expensive electrode materials will multiply production costs and increase device weight, contradicting the goal of lightweight polymer-based electrothermal films. Third, increase the applied voltage to increase the current value, according to Q=I... 2 As shown in Rt (where Q is heat, I is the current flowing through the device, R is the device resistance, and t is the energizing time), heat generation increases linearly with the square of the current. However, the increased voltage parameters will seriously threaten the safety of the device. The sandwich structure, where the electrodes are distributed as two-dimensional layers on both sides of the polymer-based conductive layer with a small electrode spacing, significantly reduces the device resistance and enables low-voltage operation, making it a safe and reliable solution.

[0006] However, existing electrothermal film preparation methods typically rely on large-area wet coating. For example, patent CN114205935A discloses a production process for a self-regulating electrothermal film, including the following steps: S1, preparing raw materials; S2, coating the raw materials; S3, film treatment; S4, printing conductive ink; S5, printing conductive fluid; S6, setting a waterproof membrane; S7, film protection. Although wet coating can produce polymer-based electrothermal films over large areas at low cost, its processability is limited for smaller areas and products requiring customization. Furthermore, traditional wet coating equipment is complex, requiring mixing equipment, slurry preparation equipment, coating equipment, drying equipment, electrode laying equipment, and encapsulation equipment, resulting in a large footprint for the machinery.

[0007] Therefore, existing technologies still need to be improved and developed to address the drawback of poor processability of small-sized polymer-based electrothermal films. Summary of the Invention

[0008] In view of the shortcomings of the prior art, the purpose of this application is to provide a sandwich-structured polymer-based electrothermal film and its preparation method. The polymer-based electrothermal film is prepared layer by layer on a base film using 3D printing, which allows for customized processing by setting the size conditions, structural parameters, and other information of the polymer-based electrothermal film according to the program, resulting in high processing efficiency and strong customizability. Simultaneously, the interfacial bonding between layers is good, the integrity is high, and the structure is stable.

[0009] To achieve the above objectives, this application adopts the following technical solution:

[0010] In a first aspect, this application provides a sandwich structure polymer-based electrothermal film, comprising a base film layer, a first fluid-conducting layer covered on the base film layer, a polymer-based conductive layer covered on the first fluid-conducting layer, a second fluid-conducting layer covered on the polymer-based conductive layer, a thermally conductive layer covered on the second fluid-conducting layer, and a flame-retardant and waterproof layer covered on the thermally conductive layer.

[0011] As an optional technical solution of this application, the first fluid-conducting layer, the polymer-based conductive layer, the second fluid-conducting layer, the thermally conductive layer, and the flame-retardant and waterproof layer are all fabricated by 3D printing.

[0012] As an optional technical solution of this application, the base film layer is one or more of polyimide (PI), polyethylene terephthalate (PET), and polytetrafluoroethylene (PTFE), with a thickness of 10-200 μm.

[0013] As the bottom layer of the electrothermal film, the base film layer needs to possess good mechanical strength, heat resistance, chemical stability, and dimensional stability. Materials such as polyimide (PI), polyethylene terephthalate (PET), and polytetrafluoroethylene (PTFE) possess these properties, enabling them to maintain stable performance under high temperatures and harsh environments. By selecting an appropriate thickness, the flexibility and strength of the electrothermal film can be balanced.

[0014] As an optional technical solution of this application, the first fluid-conducting layer and the second fluid-conducting layer are prepared by one or more of conductive silver paste and conductive copper paste, with a viscosity of 15000-30000mPa·s (25℃), sheet resistance <15mΩ / sq, and thickness of 10-100μm.

[0015] The conductive layer needs to possess good electrical conductivity and appropriate viscosity to ensure that current can pass through the electrothermal film uniformly and efficiently. Conductive silver paste and conductive copper paste have high conductivity and good printability, enabling the formation of a uniform conductive layer on the base film. By controlling the viscosity, uniform material distribution and good adhesion during printing can be ensured. Sheet resistance requirements ensure that energy loss of the electrothermal film is minimized during heating.

[0016] As an optional technical solution of this application, the polymer-based conductive layer is prepared by polymer conductive paste, which is formulated by 50-80 parts of polymer matrix, 10-50 parts of conductive agent, 5-15 parts of inorganic filler, 200-600 parts of solvent and less than 5 parts of additives, and has a thickness of 20-200 μm.

[0017] The polymer-based conductive layer is achieved through the formulation of a polymer conductive paste. The polymer matrix provides structural support and flexibility, the conductive agent forms a conductive network, and inorganic fillers enhance conductivity and mechanical strength. Solvents are used to disperse and dissolve the material, ensuring uniformity and smoothness during the printing process. Additives such as coupling agents and defoamers are used to improve the processability of the material and the performance of the final product. By adjusting the proportions of each component, the conductivity and mechanical properties of the electrothermal film can be optimized.

[0018] Optionally, the polymer matrix is ​​one or more of thermoplastic polyurethane elastomer (TPU), polyethersulfone resin (PES), polyvinylidene fluoride (PVDF), polyethylene terephthalate (PET), polyethylene oxide (PEO), polyacrylic acid (PAA), and poly(m-phenylene isophthalamide) (PMIA).

[0019] Optionally, the conductive agent is one or more of conductive carbon black, graphite, carbon nanotubes, graphene, and silver nanofibers.

[0020] Optionally, the inorganic filler is one or more of glass fiber, silicon carbide, montmorillonite, silicon dioxide, aluminum oxide, calcium carbonate, aluminum nitride, and magnesium oxide.

[0021] Optionally, the solvent is one or more of N-methylpyrrolidone (NMP), N,N-dimethylformamide (DMF), N,N-dimethylacetamide (DMAc), chloroform, carbon tetrachloride, deionized water, and tetrahydrofuran (THF).

[0022] Optionally, the additive is one or more of a coupling agent and an antifoaming agent.

[0023] As an optional technical solution of this application, the thermally conductive layer is prepared by a thermally conductive slurry, which is formulated by 20-70 parts of polymer binder, 30-80 parts of thermally conductive filler, and 150-500 parts of organic dispersant, and has a thickness of 10-100 μm.

[0024] The thermally conductive layer is achieved through the formulation of a thermally conductive paste. A polymer binder provides structural support and stability, while thermally conductive fillers such as glass fiber and aluminum nitride possess high thermal conductivity, enabling rapid heat transfer. Organic dispersants are used to disperse and dissolve the material, ensuring uniformity and adhesion during the printing process. By selecting appropriate thermally conductive fillers and polymer binders, the thermal conductivity of the electrothermal film can be optimized, improving heating efficiency.

[0025] Optionally, the polymer binder is one or more of thermoplastic polyurethane elastomer (TPU), polyethersulfone resin (PES), polyvinylidene fluoride (PVDF), polyethylene terephthalate (PET), polyethylene oxide (PEO), polyacrylic acid (PAA), and poly(m-phenylene isophthalamide) (PMIA).

[0026] Optionally, the thermally conductive filler is one or more of glass fiber, aluminum nitride, magnesium oxide, silicon carbide, and silicon nitride.

[0027] Optionally, the organic dispersant is one or more of N-methylpyrrolidone (NMP), N,N-dimethylformamide (DMF), N,N-dimethylacetamide (DMAc), chloroform, carbon tetrachloride, and tetrahydrofuran (THF).

[0028] As an optional technical solution of this application, the flame-retardant and waterproof layer is prepared by flame-retardant composite slurry, which is formulated by 70-95 parts of polymer main phase, 5-30 parts of flame retardant and 150-300 parts of organic solvent, and has a thickness of 10-150μm.

[0029] The flame-retardant and waterproof layer is achieved through the formulation of a flame-retardant composite slurry. The polymer main phase provides structural support and stability, while flame retardants such as phosphate esters, halogenated hydrocarbons, and inorganic flame retardants inhibit the spread and diffusion of flames, improving the flame-retardant performance of the electrothermal film. Organic solvents are used to disperse and dissolve the materials, ensuring uniformity and adhesion during the printing process. By selecting appropriate flame retardants and polymer main phases, the flame-retardant and waterproof properties of the electrothermal film can be optimized, ensuring safety and stability in harsh environments.

[0030] Optionally, the main phase of the polymer is one or more of polyimide (PI), polyethylene terephthalate (PET), and polytetrafluoroethylene (PTFE).

[0031] Optionally, the flame retardant is one or more of the following: tributyl phosphate, tris(2-ethylhexyl) phosphate, tris(2-chloroethyl) phosphate, tris(2,3-dichloropropyl) phosphate, tris(2,3-dibromopropyl) phosphate, Pyrol99 / toluene-diphenyl phosphate, tricresyl phosphate, triphenyl phosphate, (2-ethylhexyl)-diphenyl phosphate, chlordane anhydride, dibromomethane, trichlorobromomethane, dichlorobromomethane, pentabromoethylbenzene, tetrabromobisphenol A, etc., aromatic bromides, tris(dibromopropyl) phosphate and halocyclohexane and their derivatives, decabromodiphenyl ether and its derivatives, tellurium compounds, aluminum hydroxyl, magnesium hydroxide, and borates.

[0032] The organic solvent is one or more of N-methylpyrrolidone (NMP), N,N-dimethylformamide (DMF), N,N-dimethylacetamide (DMAc), chloroform, carbon tetrachloride, and tetrahydrofuran (THF).

[0033] Each available technical solution is based on the physical and chemical properties of the materials, as well as the functional and performance requirements of the electrothermal film. By rationally selecting materials and adjusting the proportions of each component, sandwich-structured polymer-based electrothermal films with excellent electrothermal, mechanical, thermal conductivity, flame retardant, and waterproof properties can be prepared.

[0034] Secondly, this application provides a method for preparing a sandwich-structured polymer-based electrothermal film, comprising the following steps:

[0035] S1. Print the first fluid guiding layer on the base film layer using printer ① and then dry it.

[0036] S2. Prepare a polymer conductive paste and print a polymer-based conductive layer on the surface of the first conductive layer obtained in S1 using printer ②, and then perform a drying process.

[0037] S3. Print a second conductive layer on the surface of the polymer-based conductive layer obtained in S2 using printer ③, and then dry it.

[0038] S4. Prepare the thermally conductive paste and print the thermally conductive layer on the surface of the second fluid-conducting layer obtained in S3 using printer ④, and then perform a drying process.

[0039] S5. Prepare a flame-retardant composite slurry and print a flame-retardant and waterproof layer on the surface of the thermally conductive layer obtained in S4 using printer ⑤, and then perform a drying process.

[0040] As an optional technical solution of this application, the drying temperature in S1, S2, S3, S4, and S5 is 60-120℃ and the time is 10-120min.

[0041] Based on the above technical solution, this application has the following beneficial effects:

[0042] (1) The sandwich structure polymer-based electrothermal film of this application has good interfacial bonding force between different functional layers and high degree of integration, which is beneficial to extending the working life of the electrothermal film device.

[0043] (2) The interface between the polymer-based conductive layer and the fluid-conducting layer is tightly bonded, which not only helps to reduce the resistance of the device, but also makes the heating of the electrothermal film more uniform during operation.

[0044] (3) The preparation method of the sandwich structure polymer-based electrothermal film of this application can be quickly customized to meet customer needs. At the same time, it can be configured with a dedicated printer according to different processes to achieve pulsed production. It has strong processability and is conducive to reducing production costs. Attached Figure Description

[0045] Figure 1 is a three-dimensional structural schematic diagram of the sandwich-structured polymer-based electrothermal film obtained in Example 1;

[0046] Figure 2 is a schematic cross-sectional view of the sandwich-structured polymer-based electrothermal film obtained in Example 1;

[0047] Figure 3 is a process flow diagram of the preparation of the sandwich-structured polymer-based electrothermal film obtained in Examples 1-3;

[0048] Figure 4 shows the temperature-time curve of the sandwich-structured polymer-based electrothermal film obtained in Example 1 under a DC voltage of 3V.

[0049] Among them, 1 is the base film layer, 2 is the first fluid-conducting layer, 3 is the polymer-based conductive layer, 4 is the second fluid-conducting layer, 5 is the thermally conductive layer, and 6 is the flame-retardant and waterproof layer. Detailed Implementation

[0050] As shown in Figures 1 and 2, the first objective of this application is to provide a sandwich structure polymer-based electrothermal film, wherein the Meiji structure polymer-based electrothermal film includes a base film layer 1, a first fluid-conducting layer 2 covered on the base film layer 1, a polymer-based conductive layer 3 covered on the first fluid-conducting layer 2, a second fluid-conducting layer 4 covered on the polymer-based conductive layer 3, a thermally conductive layer 5 covered on the second fluid-conducting layer, and a flame-retardant and waterproof layer 6 covered on the thermally conductive layer.

[0051] The design principle of the sandwich-structured polymer-based electrothermal film provided in this application is mainly based on the layered structure and functional superposition of materials. By orderly combining different materials and functional layers, the multifunctionality and high efficiency of the electrothermal film are achieved. The base layer, as the bottom layer of the electrothermal film, provides structural support and stability. The base layer is typically made of polymer materials with good mechanical properties and heat resistance, such as polyimide and polycarbonate. The first fluid-conducting layer, located above the base layer, primarily guides the uniform distribution of current and heat within the electrothermal film. This fluid-conducting layer is typically made of metals or alloys with good electrical conductivity, such as copper and aluminum. The polymer-based conductive layer, as the core layer of the electrothermal film, is responsible for converting electrical energy into heat energy. This conductive layer consists of a polymer matrix and conductive fillers, with the conductive fillers uniformly dispersed in the polymer matrix to form a conductive network. The second fluid-conducting layer, located above the conductive layer, works together with the first fluid-conducting layer to further ensure the uniform distribution of current and heat. The thermally conductive layer primarily improves the thermal conductivity of the electrothermal film, rapidly transferring the heat generated by the conductive layer to the surface of the electrothermal film, achieving rapid heating. The thermally conductive layer is typically made of materials with good thermal conductivity, such as graphite and carbon nanotubes. The flame-retardant and waterproof layer, as the outermost layer of the heating film, provides flame retardancy and waterproofing, ensuring the safety and stability of the heating film in harsh environments.

[0052] The sandwich structure design gives the electrothermal film excellent electrothermal conversion performance, enabling efficient conversion of electrical energy into heat energy for rapid heating. The presence of the first and second fluid-conducting layers ensures uniform distribution of current and heat within the electrothermal film, preventing localized overheating and scorching. The addition of a thermally conductive layer improves the thermal conductivity of the electrothermal film, allowing heat to be rapidly transferred to the film surface and increasing heating efficiency. A flame-retardant and waterproof layer provides additional safety, maintaining stability and safety even in harsh environments. The sandwich structure polymer-based electrothermal film can be processed and customized according to actual needs, such as adjusting the thickness of each functional layer and selecting materials, to meet the requirements of different application scenarios.

[0053] As shown in Figure 3, the second objective of this application is to provide a method for preparing a sandwich-structured polymer-based electrothermal film, comprising the following steps:

[0054] S1. Print the first fluid-conducting layer 2 on the base film layer 1 and perform drying treatment;

[0055] S2. Prepare a polymer conductive paste, print a polymer-based conductive layer 3 on the surface of the first conductive layer 2, and perform a drying process.

[0056] S3. Print the second fluid-conducting layer 4 on the surface of the polymer-based conductive layer 3 and perform a drying process;

[0057] S4. Prepare the thermally conductive paste, print the thermally conductive layer 5 on the surface of the second fluid-conducting layer 4, and perform drying treatment.

[0058] S5. Prepare flame-retardant composite slurry, print flame-retardant and waterproof layer 6 on the surface of the heat-conducting layer 5, and perform drying treatment.

[0059] The fabrication method of the sandwich-structured polymer-based electrothermal film is based on the principle of layered construction and functional superposition: using printing technology, material layers with different functions and properties are orderly superimposed on a base film layer to form a multifunctional electrothermal film. The base film layer, as the bottom layer of the electrothermal film, needs to have good mechanical properties and heat resistance to provide stable structural support. A first and second fluid-conducting layer are deposited on top of the base film layer and the polymer-based conductive layer using printing technology. Their main function is to guide the uniform distribution of current and heat within the electrothermal film, ensuring efficient and uniform heating performance. A polymer conductive paste is deposited on top of the first fluid-conducting layer using printing technology to form the polymer-based conductive layer. This layer is the core of the electrothermal film, responsible for converting electrical energy into heat energy. A thermally conductive paste is deposited on top of the second fluid-conducting layer using printing technology to form a thermally conductive layer. The main function of the thermally conductive layer is to improve the thermal conductivity of the electrothermal film, rapidly transferring the heat generated by the conductive layer to the surface of the electrothermal film. A flame-retardant composite paste is deposited on top of the thermally conductive layer using printing technology to form a flame-retardant and waterproof layer. The main function of this layer is to provide flame retardancy and waterproofing, ensuring the safety and stability of the electrothermal film in harsh environments.

[0060] Furthermore, the use of printing technology to fabricate electrothermal films enables high-precision, high-resolution pattern and structural designs, meeting complex and diverse application needs. Through a layered construction method, material layers with different functions and properties can be orderly stacked together to form a multifunctional electrothermal film. This layered construction method allows for flexible adjustment of parameters such as the thickness and material selection of each functional layer to achieve optimal performance and cost-effectiveness. Due to the precise stacking and coordination of each functional layer, the electrothermal film exhibits excellent electrothermal conversion performance, efficiently converting electrical energy into heat energy for rapid heating. The presence of a fluid-conducting layer ensures uniform distribution of current and heat within the electrothermal film, preventing localized overheating and scorching, thus improving the heating efficiency and safety of the electrothermal film. The addition of a thermally conductive layer enhances the thermal conductivity of the electrothermal film, enabling rapid heat transfer to the film surface and improving heating efficiency. A flame-retardant and waterproof layer provides additional safety protection for the electrothermal film, maintaining its stability and safety even in harsh environments.

[0061] Furthermore, 3D printing technology is a layer-by-layer construction technique. By precisely controlling the movement of the print head and the extrusion of material, a first fluid-conducting layer, a polymer-based conductive layer, a second fluid-conducting layer, a thermally conductive layer, and a flame-retardant and waterproof layer can be directly printed on the base film layer. This technology enables high-precision, high-resolution pattern and structural design, ensuring tight bonding and overall performance between layers. As the bottom layer of the electrothermal film, the base film layer needs to possess good mechanical properties, heat resistance, and chemical stability. Materials such as polyimide (PI), polyethylene terephthalate (PET), and polytetrafluoroethylene (PTFE) possess these properties, meeting the requirements for electrothermal film applications. Excellent mechanical properties and heat resistance ensure the stability of the electrothermal film. Good chemical stability makes it less susceptible to environmental factors. Appropriate thicknesses can be selected according to requirements to meet different application scenarios.

[0062] Furthermore, the conductive layer needs to possess good electrical conductivity and appropriate viscosity to ensure uniform distribution of current and heat within the electrothermal film. Conductive silver paste and conductive copper paste are commonly used conductive materials, exhibiting high conductivity and good printability. High conductivity ensures efficient heating of the electrothermal film. Appropriate viscosity facilitates printing and drying. Low sheet resistance reduces energy loss. The polymer-based conductive layer consists of a polymer matrix, conductive agent, inorganic filler, solvent, and additives. These components work together to form a conductive layer with excellent conductivity. The polymer matrix provides structural support, the conductive agent forms a conductive network, the inorganic filler enhances conductivity and mechanical strength, the solvent disperses and dissolves the material, and the additives improve the material's processing performance. The thermally conductive layer consists of a polymer binder, thermally conductive filler, and organic dispersant. The polymer binder provides structural support, the thermally conductive filler forms thermally conductive channels, and the organic dispersant disperses and dissolves the material. These components work together to improve the thermal conductivity of the electrothermal film. The flame-retardant and waterproof layer consists of a polymer main phase, flame retardant, and organic solvent. The polymer matrix provides structural support and flame-retardant properties, flame retardants enhance the flame-retardant effect, and organic solvents are used to disperse and dissolve the material. These components work together to improve the flame-retardant and waterproof properties of the electrothermal film.

[0063] Therefore, each scheme in this application is rationally designed based on the physical and chemical properties of the materials and the application requirements of the electrothermal film. By selecting appropriate materials and formulation ratios, sandwich-structured polymer-based electrothermal films with excellent electrothermal, mechanical, thermal conductivity, flame retardant, and waterproof properties can be prepared. These advantages make this electrothermal film a promising candidate for applications in heating, de-icing, and heat preservation.

[0064] The present application will be further described below with reference to the accompanying drawings and specific implementation methods.

[0065] Example 1:

[0066] Example 1 provides a sandwich-structured polymer-based electrothermal film and its preparation method, the specific steps of which are as follows:

[0067] S1. Using conductive silver paste as ink, a silver first fluid-conducting layer is printed on the surface of polyethylene terephthalate (PET) with a thickness of 80μm using printer ①, and dried at 60℃ for 120min. The thickness of the first fluid-conducting layer is about 10μm.

[0068] S2. Dissolve 2g of thermoplastic polyurethane elastomer (TPU) in 4g of N-methylpyrrolidone (NMP) solvent, and heat and stir at 60℃ and 400rpm for 6h to form a TPU solution. Then add 0.7g of conductive carbon black powder, 0.2g of silica powder, and 0.05g of siloxane coupling agent to the TPU solution, and heat and stir at 60℃ and 400rpm for 3h to form a polymer conductive paste. Add the prepared polymer conductive paste to printer ② and print it on the surface of the silver first conductive layer prepared in S1. Dry at 80℃ for 100min. The thickness of the obtained polymer-based conductive layer is approximately 50μm.

[0069] S3. Using conductive silver paste as ink, a second silver conductive layer is printed on the surface of the polymer-based conductive layer obtained in S2 using printer ③, and dried at 60°C for 120 min. The thickness of the second conductive layer is approximately 10 μm.

[0070] S4. Dissolve 1g of thermoplastic polyurethane elastomer (TPU) in 3g of N-methylpyrrolidone (NMP) solvent, and heat and stir at 60℃ and 400rpm for 6h to form a TPU solution. Then add 0.8g of glass fiber powder to the TPU solution, and heat and stir at 60℃ and 400rpm for 3h to form a thermally conductive paste. Add the prepared thermally conductive paste to printer ④ and print it on the surface of the silver second thermally conductive layer prepared in S3. Dry at 80℃ for 100min. The thickness of the obtained thermally conductive layer is approximately 30μm.

[0071] S5. Dissolve 1g of polyethylene terephthalate (PET) in 4g of N,N-dimethylformamide (DMF) solvent, and heat and stir at 80℃ and 400rpm for 6h to form a PET solution. Then add 0.2g of tributyl phosphate, and heat and stir at 80℃ and 400rpm for 3h to form a flame-retardant composite slurry. Add the prepared flame-retardant composite slurry to printer ⑤ and print it on the surface of the second fluid-conducting layer prepared in S4. Dry at 80℃ for 120min. The resulting flame-retardant and waterproof layer has a thickness of approximately 60μm.

[0072] Figure 1 shows a three-dimensional structural schematic diagram of the sandwich-structured polymer-based electrothermal film obtained in Example 1, Figure 2 shows a cross-sectional structural schematic diagram, and Figure 3 shows a process flow chart. The first and second fluid conductors of the sandwich-structured polymer-based electrothermal film obtained in Example 1 are connected to the positive and negative electrodes of a DC regulated voltage, respectively. The temperature-time curve at 3V is shown in Figure 4. The stable heating temperature at room temperature is 60℃.

[0073] Example 2:

[0074] Example 2 provides a sandwich-structured polymer-based electrothermal film and its preparation method, the specific steps of which are as follows:

[0075] S1. Using conductive copper paste as ink, a copper first conductive layer is printed on a polyimide (PI) surface with a thickness of 30 μm using printer ①, and dried at 80°C for 60 min. The thickness of the first conductive layer is approximately 20 μm.

[0076] S2. Add 0.5g graphite powder, 0.3g conductive carbon black powder, 0.1g glass fiber powder, and 0.04g siloxane coupling agent to a DMAc / NMP mixed solution containing dissolved polyacrylic acid (PAA), and heat and stir at 80℃ and 400rpm for 3h to form a polymer conductive slurry. Add the prepared polymer conductive slurry to printer ② and print it onto the surface of the copper first conductive layer prepared in S1. Dry at 90℃ for 90min. The thickness of the obtained polymer-based conductive layer is approximately 50μm.

[0077] S3. Using conductive copper paste as ink, a second copper conductive layer is printed on the surface of the polymer-based conductive layer obtained in S2 using printer ③, and dried at 80°C for 60 min. The thickness of the second conductive layer is approximately 15 μm.

[0078] S4. Add 0.6g of aluminum nitride powder to a DMAc / NMP mixed solution containing dissolved PAA, and heat and stir at 80℃ and 400rpm for 2h to form a thermally conductive paste. Add the prepared thermally conductive paste to printer ④ and print it onto the surface of the copper second thermally conductive layer prepared in S3. Dry at 90℃ for 90min. The thickness of the obtained thermally conductive layer is approximately 25μm.

[0079] S5. Add 0.1g of tricresyl phosphate to a DMAc / NMP mixed solution containing dissolved PAA, and heat and stir at 80℃ and 400rpm for 2h to form a flame-retardant composite slurry. Add the prepared flame-retardant composite slurry to printer ⑤ and print it onto the surface of the second fluid-conducting layer prepared in S4. Dry at 90℃ for 90min. The resulting flame-retardant and waterproof layer has a thickness of approximately 50μm.

[0080] The sandwich-structured polymer-based electrothermal film obtained in Example 2 is connected to the positive and negative terminals of a DC regulated voltage at the first and second fluid conductors, respectively. The stable heating temperature can reach 150°C at a voltage of 10V.

[0081] Example 3:

[0082] Example 3 provides a sandwich-structured polymer-based electrothermal film and its preparation method, the specific steps of which are as follows:

[0083] S1. Using conductive silver paste as ink, a silver first fluid-conducting layer is printed on a polytetrafluoroethylene (PTFE) surface with a thickness of 60μm using printer ①, and dried at 110℃ for 20min. The thickness of the first fluid-conducting layer is approximately 10μm.

[0084] S2. Dissolve 2.5g of polyvinylidene fluoride (PVDF) in 5g of N-methylpyrrolidone (NMP) and heat and stir at 70℃ and 400rpm for 6h to form a PVDF solution. Then add 0.05g of silver nanofibers, 0.1g of multi-walled carbon nanotubes, 0.15g of conductive carbon black, and 0.1g of alumina powder to the PVDF solution and heat and stir at 70℃ and 400rpm for 3h to form a polymer conductive paste. Add the prepared polymer conductive paste to printer ② and print it on the surface of the silver first conductive layer prepared in S1. Dry at 80℃ for 60min. The thickness of the obtained polymer-based conductive layer is approximately 20μm.

[0085] S3. Using conductive copper paste as ink, a silver second conductive layer is printed on the surface of the polymer-based conductive layer obtained in S2 using printer ③, and dried at 80°C for 70 min. The thickness of the second conductive layer is approximately 10 μm.

[0086] S4. Dissolve 1g of polyvinylidene fluoride (PVDF) in 3g of N-methylpyrrolidone (NMP) solvent, and heat and stir at 70℃ and 400rpm for 6h to form a PVDF solution. Then add 0.8g of magnesium oxide powder to the PVDF solution, and heat and stir at 70℃ and 400rpm for 3h to form a thermally conductive paste. Add the prepared thermally conductive paste to printer ④ and print it on the surface of the silver second thermally conductive layer prepared in S3. Dry at 110℃ for 20min. The thickness of the obtained thermally conductive layer is approximately 40μm.

[0087] S5. Dissolve 1g of polyethylene terephthalate (PET) in 4g of N,N-dimethylformamide (DMF) solvent, and heat and stir at 80℃ and 400rpm for 6h to form a PET solution. Then add 0.1g of aluminum hydroxide, and heat and stir at 80℃ and 400rpm for 3h to form a flame-retardant composite slurry. Add the prepared flame-retardant composite slurry to printer ⑤ and print it on the surface of the second fluid-conducting layer prepared in S4. Dry at 70℃ for 90min. The resulting flame-retardant and waterproof layer has a thickness of approximately 30μm.

[0088] The sandwich-structured polymer-based electrothermal film obtained in Example 3 is connected to the positive and negative terminals of a DC regulated voltage at the first and second fluid conductors, respectively. The stable heating temperature can reach 50°C at a voltage of 2V.

Claims

1. A sandwich-structured polymer-based electrothermal film, characterized in that: The Meiji-structured polymer-based electrothermal film includes a base film layer, a first fluid-conducting layer covering the base film layer, a polymer-based conductive layer covering the first fluid-conducting layer, a second fluid-conducting layer covering the polymer-based conductive layer, a thermally conductive layer covering the second fluid-conducting layer, and a flame-retardant and waterproof layer covering the thermally conductive layer.

2. The sandwich-structured polymer-based electrothermal film according to claim 1, characterized in that: The first fluid-conducting layer, the polymer-based conductive layer, the second fluid-conducting layer, the thermally conductive layer, and the flame-retardant and waterproof layer are all fabricated using 3D printing.

3. The sandwich-structured polymer-based electrothermal film according to claim 1, characterized in that: The base film layer is one or more of polyimide, polyethylene terephthalate, and polytetrafluoroethylene, and the thickness of the base film layer is 10-200 μm.

4. The sandwich-structured polymer-based electrothermal film according to claim 1, characterized in that: The first and second fluid-conducting layers are prepared from one or more of conductive silver paste and conductive copper paste, with a viscosity of 15000-30000 mPa·s, a sheet resistance of <15 mΩ / sq, and a thickness of 10-100 μm.

5. The sandwich-structured polymer-based electrothermal film according to claim 1, characterized in that: The polymer-based conductive layer is prepared from a polymer conductive slurry, which is composed of 50-80 parts of polymer matrix, 10-50 parts of conductive agent, 5-15 parts of inorganic filler, 200-600 parts of solvent and less than 5 parts of additives, with a thickness of 20-200 μm.

6. The sandwich-structured polymer-based electrothermal film according to claim 5, characterized in that: The polymer matrix is ​​one or more of thermoplastic polyurethane elastomer, polyethersulfone resin, polyvinylidene fluoride, polyethylene terephthalate, polyethylene oxide, polyacrylic acid, and polyisophthalamide; the conductive agent is one or more of conductive carbon black, graphite, carbon nanotubes, graphene, and silver nanofibers; the inorganic filler is one or more of glass fiber, silicon carbide, montmorillonite, silicon dioxide, aluminum oxide, calcium carbonate, aluminum nitride, and magnesium oxide; and the solvent is one or more of N-methylpyrrolidone, N,N-dimethylformamide, N,N-dimethylacetamide, chloroform, carbon tetrachloride, deionized water, and tetrahydrofuran.

7. The sandwich-structured polymer-based electrothermal film according to claim 1, characterized in that: The thermally conductive layer is prepared from a thermally conductive slurry, which is composed of 20-70 parts of polymer binder, 30-80 parts of thermally conductive filler, and 150-500 parts of organic dispersant, with a thickness of 10-100 μm.

8. The sandwich-structured polymer-based electrothermal film according to claim 7, characterized in that: The polymer binder is one or more of thermoplastic polyurethane elastomer, polyethersulfone resin, polyvinylidene fluoride, polyethylene terephthalate, polyethylene oxide, polyacrylic acid, and polyisophthalamide; the thermally conductive filler is one or more of glass fiber, aluminum nitride, magnesium oxide, silicon carbide, and silicon nitride; and the organic dispersant is one or more of N-methylpyrrolidone, N,N-dimethylformamide, N,N-dimethylacetamide, chloroform, carbon tetrachloride, and tetrahydrofuran.

9. The sandwich-structured polymer-based electrothermal film according to claim 1, characterized in that: The flame-retardant and waterproof layer is prepared from a flame-retardant composite slurry, which is composed of 70-95 parts of a polymer main phase, 5-30 parts of a flame retardant, and 150-300 parts of an organic solvent, with a thickness of 10-150 μm. The polymer main phase is one or more of polyimide, polyethylene terephthalate, and polytetrafluoroethylene. The flame retardant is tributyl phosphate, tris(2-ethylhexyl) phosphate, tris(2-chloroethyl) phosphate, tris(2,3-dichloropropyl) phosphate, tris(2,3-dibromopropyl) phosphate, or Pyrol99. The organic solvent is one or more of the following: toluene-diphenyl phosphate, tricresyl phosphate, triphenyl phosphate, (2-ethylhexyl)-diphenyl phosphate, chlordane anhydride, dibromomethane, trichlorobromomethane, dichlorobromomethane, pentabromoethylbenzene, tetrabromobisphenol A and other aromatic bromides, tri(dibromopropyl) phosphate and halocyclohexane and their derivatives, decabromodiphenyl ether and its derivatives, tellurium compounds, aluminum hydroxyl, magnesium hydroxide, and borates; 10. A method for preparing a sandwich-structured polymer-based electrothermal film according to any one of claims 1-9, characterized in that, Includes the following steps: S1. Print the first fluid-conducting layer on the base film layer and perform drying treatment; S2. Prepare a polymer conductive paste, print a polymer-based conductive layer on the surface of the first conductive layer, and perform a drying process. S3. Print a second conductive layer on the surface of the polymer-based conductive layer and perform a drying process; S4. Prepare the thermally conductive paste, print the thermally conductive layer on the surface of the second fluid-conducting layer, and perform a drying process. S5. Prepare flame-retardant composite slurry, print a flame-retardant and waterproof layer on the surface of the thermally conductive layer, and perform drying treatment.

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