Flexible electric blanket for complex curved surface and preparation method thereof

Abstract

The invention discloses a flexible electric blanket for a complex curved surface and a preparation method thereof, and the electric blanket sequentially comprises a bionic outer protection layer which is a silica gel coating glass fabric with a micrometer pit and nanometer protrusion composite coarse structure from one side close to a to-be-heated surface to one side away from the to-be-heated surface; the conductive heating layer is a carbon nanotube and graphene mixed network formed on the surface of the polyimide film through a transfer process; the gradient heat preservation layer is formed by compounding a plurality of layers of SiO2 aerogel composite felts with different densities through hot pressing; an insulating layer and an outer protective layer. The invention also provides a preparation method of the electric blanket. The manufactured electric blanket solves the technical problems that an existing flexible electric heating part is poor in fitting performance to a complex curved surface, low in heat preservation efficiency, prone to being adhered to a workpiece and cumbersome on the whole, and has the excellent comprehensive performance of being light in weight, high in heat preservation performance, strong in fitting performance and easy to strip.

Description

Technical Field

[0001] This invention relates to the field of electric blanket manufacturing technology, and in particular to a flexible electric blanket for complex curved surfaces and its manufacturing method. Background Technology

[0002] Flexible electric heating components are often used in industrial preheating, composite material curing, equipment insulation and other fields. Common flexible electric heating components include metal wire braided heating pads and etched foil circuit heating films. However, they generally have the following technical problems: (1) Due to their own high rigidity, it is difficult to tightly fit complex three-dimensional curved surfaces with a curvature radius of less than 0.5 meters, resulting in gaps in the contact surface of the flexible electric heating components, causing serious local heat loss and temperature unevenness, affecting the heating effect and energy efficiency; (2) The insulation layer is mostly made of non-woven fabric and other materials. The thermal conductivity of non-woven fabric and other materials increases sharply in low temperature environment, the insulation performance is seriously degraded, and the elasticity after being compressed is poor, and it cannot adapt to the deformation of the curved surface; (3) When used in the curing of composite materials such as epoxy resin, the outer surface of the flexible electric heating component is easy to stick to the cured resin. When peeled off, it is very easy to damage the expensive working substrate (such as wind turbine blade skin), increasing maintenance costs and risks; (4) Existing flexible electric heating components are generally heavy, and the weight per unit area generally exceeds 3 kg / m 2 However, this makes it inconvenient to use on large components. Therefore, there is an urgent need for a flexible electrothermal component that can adapt to complex curved surfaces, has efficient heat preservation, easy interface peeling, and achieves lightweight design. Summary of the Invention

[0003] This application provides a flexible electric heating blanket for complex curved surfaces and its preparation method, which solves the technical problems of existing flexible electric heating components, such as poor fit to complex curved surfaces, low heat preservation efficiency, easy adhesion to workpieces at high temperatures, and overall bulkiness. By adopting a protective layer with a biomimetic micro-nano composite rough structure and an ultra-low surface energy coating, a gradient aerogel heat preservation layer with a gradient density, and a conductive heating layer based on a carbon nanotube and graphene hybrid network, the application achieves the technical effects of extremely thin and light electric heating blanket (i.e., flexible electric heating component), strong surface adaptability, high-efficiency energy-saving heat preservation, and non-destructive and easy peeling from composite materials.

[0004] This application provides a flexible electric heating blanket for complex curved surfaces, wherein the following components are stacked sequentially from the side closest to the surface to be heated to the side furthest away: A biomimetic outer protective layer, wherein the biomimetic outer protective layer is a silicone-coated fiberglass cloth with a composite rough structure of micron-sized pits and nano-sized protrusions; A conductive heating layer is stacked on top of the biomimetic outer protective layer. The conductive heating layer is a polyimide film as the base film and a carbon nanotube and graphene hybrid network formed on the surface of the polyimide film base film by a transfer process. A gradient insulation layer is stacked on top of the conductive heating layer. The gradient insulation layer is formed by hot-pressing multiple layers of SiO2 aerogel composite felt with different densities, and the density is gradient-distributed and ranges from 80 kg / m³. 3 Up to 180 kg / m 3 between; An insulating layer stacked on top of the conductive heating layer; And an outer protective layer.

[0005] Preferably, the composite rough structure of micron-sized pits and nano-sized protrusions is further grafted with a nano-thickness perfluoroalkyl silicon low surface energy coating.

[0006] Preferably, the sheet resistance of the conductive heating layer is 3.5-4.0 Ω / sq.

[0007] Preferably, the thickness of the gradient insulation layer is 3.0±0.2mm.

[0008] Preferably, the weight per unit area of ​​the electric blanket is no greater than 1.8 kg / m². 2 .

[0009] The present invention also provides a method for a flexible electric blanket for complex curved surfaces as described in any of the preceding claims, comprising the following steps: Step 1: Prepare a biomimetic outer protective layer by hot pressing a micron-sized pit array onto a glass fiber cloth impregnated with silicone rubber on one side, and then use plasma treatment to construct a composite rough structure of micron-sized pits and nano-protrusions. Step 2: Prepare the conductive heating layer. First, carbon nanotubes and graphene are co-grown on a high-temperature resistant metal foil substrate using chemical vapor deposition to form a hybrid network. Then, the hybrid network is transferred to the surface of a plasma-treated polyimide film substrate. Finally, composite electrode paste is printed and cured. Step 3: Prepare a gradient insulation layer by stacking three or more SiO2 aerogel felts of different densities and then hot-pressing them in a gradient manner to form a composite felt with a gradient change in density. Step 4: Stacking and encapsulating the electric blanket, the biomimetic outer protective layer, the conductive heating layer, the gradient heat preservation layer, the insulation layer and the outer protective layer are stacked in sequence and integrated into one unit through a hot-pressing composite process.

[0010] One technical solution provided in this application embodiment has at least the following technical effects: 1. Due to the adoption of a biomimetic outer protective layer with a composite rough structure of "micron-sized pits / nano-sized protrusions" grafted with a perfluoroalkyl silane coating, this structure effectively reduces its surface energy, achieving a contact angle of 162°±3° with liquid epoxy resin, thus realizing superhydrophobic resin properties. Therefore, it fundamentally solves the technical problem of adhesion between the electric heating blanket and the resin substrate after high-temperature curing, achieving a peel strength as low as 3.2 N / cm, enabling non-destructive and convenient peeling, protecting the surface integrity of the workpiece, and improving operational efficiency.

[0011] 2. Due to the use of densities from 80kg / m³ 3 Up to 180kg / m 3 The use of multi-layered SiO2 gradient aerogel composite felt with varying densities as an insulation layer significantly improves the thermal insulation performance of electric blankets. In extremely cold environments of -20℃, the system heat loss rate is effectively controlled to within 10.8%, achieving high efficiency and energy saving, and overcoming the defect of traditional insulation materials whose performance deteriorates sharply in low-temperature environments.

[0012] 3. Due to the use of a conductive heating layer with polyimide as the substrate and a hybrid network of carbon nanotubes and graphene as the heating element, this structure possesses excellent conductivity, flexibility, and uniform surface heating. This allows the electric blanket to maintain a temperature uniformity of ±1.8℃ on its heating surface when operating at a steady state of 85℃, effectively avoiding the risk of localized overheating. Simultaneously, the electric blanket has a lightweight and thin overall structure, with a unit area weight of no more than 1.8 kg / m². 2 With a minimum fit radius of curvature of 0.2 meters, it achieves close adaptive fitting of complex three-dimensional curved surfaces.

[0013] 4. Due to the synergistic design of the aforementioned biomimetic structure, gradient insulation, and uniform heating, and the integration through an optimized hot-pressing composite process, the electric blanket produced exhibits a power attenuation rate of less than 1.7% after 2880 hours of equivalent operation in an accelerated aging test at 110℃. Its insulation withstand voltage passes the 3750V AC test, verifying its excellent reliability and durability for long-term use in harsh industrial environments. Attached Figure Description

[0014] Figure 1 This is a schematic diagram of the structure of the electric blanket in Embodiment 1 of this application; 1-Bionic outer protective layer; 2-Conductive heating layer; 3-Gradient insulation layer; 4-Insulation layer; 5-Silicone-coated fiberglass cloth. Detailed Implementation

[0015] To make the objectives, technical solutions, and advantages of this invention clearer, the following detailed and complete description of a method for preparing a flexible electric blanket for complex curved surfaces, in conjunction with specific embodiments and accompanying drawings, will be provided. The following embodiments will proceed according to the four core steps of "bionic outer protective layer preparation," "conductive heating layer preparation," "gradient insulation layer preparation," and "overall assembly and packaging," specifically explaining the material selection, process parameters, and final integration method for each layer, so as to fully disclose the technical implementation path of this invention. Example 1

[0016] Step 1: Fabrication of a biomimetic outer protective layer (1) Select 280g / m 2 The substrate is a plain-weave fiberglass cloth with a thickness of 0.45mm, impregnated with liquid silicone rubber on one side.

[0017] (2) The semi-cured silicone fiberglass cloth is passed through a precision roller pressing mold with micro-cylinder array. The precision roller pressing mold has a column diameter of 15~150μm and a height of 5~50μm. It is hot-pressed at 120℃ and 0.5MPa pressure for 5min. In this step, the micro-cylinders of the mold are used to imprint the corresponding micro-pit array on the silicone surface, thereby obtaining a preliminary biomimetic structure on the material surface.

[0018] (3) The material with the micro-pit structure in step (2) is placed in a plasma treatment device and subjected to plasma treatment for 30 seconds in a mixed atmosphere of oxygen and tetrafluoromethane. This step is mainly to further etch nanoscale textures on the basis of the micron-level pit structure to form a composite rough structure of "micron-pits / nano-protrusions" and activate surface chemical bonds. Then, immediately on the plasma-activated surface, a nano-thickness film is uniformly applied to the surface by ultrasonic spraying using a perfluoroalkyl silane solution. Subsequently, heat treatment is performed at 150°C to form a strong, dense, and extremely low surface energy permanent functional coating, thus obtaining a biomimetic outer protective layer.

[0019] Step 2: Prepare the conductive heating layer (1) Take a 50μm thick polyimide film as the base film, clean it and place it in a plasma treatment machine, treat it at 100-200W power for 1-2 minutes to improve the surface energy.

[0020] (2) First, a hybrid network of vertical arrays of carbon nanotubes and few-layer graphene sheets is co-grown on a copper foil substrate at 650°C and ambient pressure using catalytic chemical vapor deposition. Then, the hybrid network is completely transferred to the surface of the polyimide film in (1) using polymer-assisted wet transfer technology, and is firmly adhered by applying pressure and heating. The areal density of the film is controlled to be 8-10 g / m². 2 .

[0021] (3) Using a high-precision screen printing machine, a composite slurry of silver nanowires with a diameter of 30 nm and a length of 20-50 μm and a thermosensitive self-healing hydrogel was printed onto both ends of the film as electrodes according to a predetermined pattern. The film was then cured in an 80°C oven for 30 minutes. The sheet resistance was measured using a four-probe tester to ensure it was within the range of 3.5–4.0 Ω / sq. A withstand voltage test was performed at ≥3000V AC for 1 minute.

[0022] Step 3: Prepare the gradient insulation layer (1) The density is 80 kg / m³ 3 120 kg / m 3 180 kg / m 3 Three types of SiO2 aerogel felts were stacked in order of low, medium, and high density. On a specialized hot press, by precisely controlling the pressure distribution (higher at the edges, lower at the center), the materials were hot-pressed for 10 minutes at 0.2-0.8 MPa and 100°C, allowing the three layers to interpenetrate at the interfaces, forming a composite felt with a gradient structure transitioning from the low-density side to the high-density side. The total thickness was controlled at 3.0 ± 0.2 mm.

[0023] (2) Cut according to product size and seal the edges with high temperature resistant fiberglass tape to prevent powder from falling off.

[0024] Step 4: Assembly and Packaging of the Electric Blanket (1) The biomimetic outer protective layer 1, conductive heating layer 2, gradient insulation layer 3, insulating layer 4, and silicone-coated fiberglass cloth 5 are stacked in order from bottom to top. The bottommost biomimetic outer protective layer is the one that contacts the surface to be heated. Before stacking, a 50μm thick thermoplastic polyurethane hot melt adhesive film is applied to the upper and lower surfaces of the gradient insulation layer. The stack is placed in a vacuum hot press and kept at 0.15MPa and 135℃ for 15 minutes. The selected SiO2 aerogel gradient composite felt has a temperature resistance much higher than this composite temperature, which allows the hot melt adhesive film to melt and penetrate into the interface of adjacent materials, thereby achieving a strong and flexible composite between the layers. The core purpose is interlayer composite rather than secondary densification of the aerogel, so a lower pressure is used.

[0025] The insulating layer can be a thin polyimide or silicone insulating film with a thickness of approximately 0.1 mm.

[0026] Among them, silicone-coated fiberglass cloth can also be a heat-resistant fabric.

[0027] Among them, the weight per unit area of ​​the electric blanket shall not exceed 1.8 kg / m². 2 .

[0028] (2) Highly conductive and flexible conductive silver paste is used to solder silver-plated copper core soft wires to the silver nanowire composite electrode of the heating layer. Subsequently, flexible flame-retardant silicone rubber is coated on the solder joints and the root of the wires for potting insulation, and a stress-relief structure is molded. Finally, the lead bundle is connected to the IP69K waterproof quick-connect connector. Optionally, in order to facilitate cooperation with an external temperature control system for precise temperature management, after completing the electrode connection and protection, at least two PT100 thin-film temperature control sensors can be pre-encapsulated between the conductive heating layer and the gradient insulation layer before the composite layer is stacked. This allows for faster and more accurate surface temperature feedback and control in conjunction with the intelligent temperature control system. The sensor signal leads are led out with the stack and eventually converge into the waterproof connector. The integrated heating blanket body is rolled to the specified diameter for final aging test and functional verification.

[0029] The electric blanket prepared by this invention exhibits the following technical performance indicators after testing: the biomimetic outer protective layer achieves a contact angle of 162°±3° with liquid epoxy resin, demonstrating superhydrophobic resin properties; its peel strength with the cured epoxy resin is only 3.2 N / cm, maintaining 3.8 N / cm after 50 repeated uses, achieving extremely low adhesion and durable peeling. The conductive heating layer exhibits excellent sheet resistance uniformity, with an average value of 3.78 Ω / sq and a coefficient of variation of less than 3.2%, and a surface temperature uniformity of ±1.8℃ during steady-state operation at 85℃. The gradient insulation layer has an overall thermal conductivity as low as 0.016 W / (m·K), and when maintaining the working surface temperature at 85℃ in an extremely cold environment of -20℃, the system heat loss rate is effectively controlled within 10.8%. The integrated electric blanket heats up in no more than 20 minutes at 25°C, has a minimum conformable curvature radius of 0.2 meters, and exhibits a power attenuation rate of less than 1.7% after 2880 hours of equivalent operation in an accelerated aging test at 110°C, verifying its long-term reliability. All electrical safety performance meets standard requirements, and its insulation withstand voltage passes the 3750V AC test.

[0030] Although preferred embodiments of the invention have been described, those skilled in the art, upon learning the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including both the preferred embodiments and all changes and modifications falling within the scope of the invention.

[0031] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. Therefore, if these modifications and variations fall within the scope of the claims of this invention and their equivalents, this invention also intends to include these modifications and variations.

Claims

1. A flexible electrocaloric blanket for complex surfaces, wherein, From the side close to the surface to be heated to the side away from it, in turn, laminated including: Bionic outer protective layer, the bionic outer protective layer is a micropit and nanoprotrusion composite rough structure of silica gel coating glass cloth; Laminated on the bionic outer protective layer of conductive heating layer, the conductive heating layer is a polyimide film as a base film, and a carbon nanotube and graphene mixed network formed on the surface of the polyimide film base film by transfer process; A gradient heat-insulating layer stacked on the conductive heating layer, the gradient heat-insulating layer being formed by hot-pressing and compounding of multiple layers of SiO2 aerogel composite felt with different densities, the densities being gradient-distributed and ranging from 80 kg / m 3 to 180 kg / m 3 . Laminated on the conductive heating layer of insulating layer; And outer protective layer.

2. A flexible electrocaloric blanket for complex surfaces as claimed in claim 1, characterized in that, The micropit and nanoprotrusion composite rough structure is also grafted with a nanoscale thickness of perfluoroalkylsilicon low surface energy coating.

3. A flexible electrocaloric blanket for complex surfaces as claimed in claim 1, wherein, The sheet resistance of the conductive heating layer is 3.5-4.0 Ω / sq.

4. A flexible electrocaloric blanket for complex surfaces as claimed in claim 1, wherein, The thickness of the gradient heat preservation layer is 3.0±0.2mm.

5. A flexible electrocaloric blanket for complex surfaces as claimed in claim 1, wherein, The weight per unit area of the electric blanket is not more than 1.8 kg / m 2 .

6. A method of manufacturing a flexible heating mat as claimed in any one of claims 1 to 5, characterised in that, Including the following steps: Step one: preparing a bionic outer protective layer, hot pressing a micropit array on a single-sided impregnated silica rubber glass cloth, and then using plasma treatment to build a micropit and nanoprotrusion composite rough structure; Step two: preparing a conductive heating layer, first growing carbon nanotubes and graphene on a high-temperature resistant metal foil substrate to form a mixed network by chemical vapor deposition, then transferring the mixed network to the surface of a plasma treated polyimide film base film, then printing a composite electrode paste and curing; Step three: preparing a gradient heat preservation layer, laminating three or more different density SiO2 aerogel felt and then gradient hot pressing to form a composite felt with gradient density change; Step four: electric heating blanket packaging, laminating the bionic outer protective layer, the conductive heating layer, the gradient heat preservation layer, the insulating layer and the outer protective layer in turn, and integrating them by hot pressing composite process.

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