Graphene composite substrate flexible electric heating sheet

Abstract

The application belongs to the field of graphene composite heating material and application, and particularly discloses a graphene composite base material flexible electric heating sheet; the heating sheet is a sandwich structure, comprising upper and lower two layers of water-repellent fabric layers which constitute outer layers, a graphene composite base material coating heating strip located between the upper and lower water-repellent fabric layers, copper foil electrode strips, and power supply lines; the graphene composite base material coating heating strip is attached to the inner surface of at least one of the upper and lower water-repellent fabric layers; a plurality of graphene composite base material coating heating strips are arranged into graphene coating strips in an array with intervals, three copper foil electrode strips are arranged at the upper and lower ends and the middle position of the graphene coating strips; a fourth copper foil electrode strip is connected in series with the copper foil electrode strips at the upper and lower ends; after the copper foil electrode strips at the upper and lower ends are connected in series, the copper foil electrode strip at the middle is connected in parallel with the copper foil electrode strips at the upper and lower ends; and two power supply lines are respectively welded with the electrode connectors of the electrode strips at the middle and the two ends. The electric heating sheet prepared by the application has good heating effect.

Description

Technical Field

[0001] This invention relates to graphene composite heating materials and their applications, specifically to a flexible electric heating element based on graphene composite substrate. Background Technology

[0002] Traditional thermal clothing is already well-known, but with technological advancements and improved living standards, the demand for electrically heated garments is increasing daily. As a type of functional clothing, electrically heated garments provide warmth to people working or living in cold environments. They attracted attention and research from scholars both domestically and internationally as early as the mid-20th century. Their main principle involves attaching electric heating elements to the garment, using portable power sources such as power banks to generate heat, which then radiates to the skin for warmth. With breakthroughs in technologies such as sustainable power sources and washability, electrically heated garments have found applications in civilian, military, cold-environment operations, and clinical treatment fields.

[0003] Most existing electric heating element products on the market use materials such as copper wire, stainless steel blended yarn, silver-plated filament, and graphite with carbon black, which have problems such as low resistance, uneven heating, and low heating efficiency, and need further improvement. Summary of the Invention

[0004] Based on the above background technology, the purpose of this invention is to provide a flexible electric heating sheet with graphene composite substrate, which has uniform heating, high thermal efficiency, flexible size control, and is easy to industrialize.

[0005] The present invention adopts the following technical solution:

[0006] A graphene composite substrate flexible electric heating element, wherein the heating element has a sandwich structure, comprising an outer layer of water-repellent fabric composed of two upper and lower layers, a graphene composite substrate coated heating strip, a copper foil electrode strip, and a power cord located between the upper and lower water-repellent fabric layers.

[0007] The graphene composite substrate coated heating strip is attached to at least one inner surface of the upper and lower water-repellent fabric layers.

[0008] Several graphene composite substrate coated heating strips are arranged in an array of graphene coated strips with intervals, and three copper foil electrode strips are inserted at the top, bottom and middle positions of the graphene coated strips.

[0009] The fourth copper foil electrode strip connects the copper foil electrode strips at both ends in series;

[0010] The copper foil electrode strips at the top and bottom ends are connected in series and then connected in parallel with the copper foil electrode strip in the middle. The two power lines are welded to the electrode joints of the middle and the two ends of the electrode strip, respectively.

[0011] Preferably, the array of graphene coating strips is a rectangular array, wherein the graphene composite substrate coating heating strips are parallel to each other.

[0012] Furthermore, in the aforementioned graphene composite substrate flexible electric heating sheet, the outer surface of the water-repellent fabric layer is water-repellent, and the inner surface is either water-repellent or non-water-repellent. Setting the inner surface as non-water-repellent can reduce costs and facilitate the application of graphene coating strips.

[0013] Furthermore, in the above-mentioned graphene composite substrate flexible electric heating sheet, two power lines are led out of the heating sheet and connected to a mobile power supply, and a switch is provided between the power lines and the mobile power supply.

[0014] Furthermore, in the above-mentioned flexible electric heating sheet with graphene composite substrate, the width of the graphene composite substrate coating heating strip is 0.1-1cm, and the width between the graphene composite substrate coating heating strips is 0.1-1cm.

[0015] Furthermore, in the above-mentioned flexible electric heating sheet with graphene composite substrate, the graphene composite substrate coating heating strip is formed by coating the graphene composite substrate into lines using a printing method.

[0016] Furthermore, in the above-mentioned graphene composite substrate flexible electric heating sheet, the water-repellent fabric is at least one side coated with a silver film of polyester plain weave woven fabric.

[0017] Furthermore, the above-mentioned flexible electric heating sheet with graphene composite substrate is prepared by the following steps:

[0018] 1) Preparation of Slurry A

[0019] Raw materials: by mass parts, ① water-based carbon nanotube slurry 1-1.1 parts, ② graphene filter cake 1-1.1 parts, ③ resin 0.4-0.5 parts, ④ water 1-1.1 parts;

[0020] Steps: a. Mix ①②③④ in sequence and stir in a mixer with a speed of 4000-4200 r / min for 1-3 hours to obtain 01# slurry;

[0021] (2) Preparation of B slurry

[0022] Raw materials: by weight parts, ①A slurry 100-105 parts, ②thickener 1-1.05 parts;

[0023] Steps: a. Mix ① and ② and stir in a mixer at a speed of 600-620 r / min for 5-6 min to obtain slurry B, which is the graphene composite substrate.

[0024] Furthermore, the process of attaching the graphene composite substrate coated heating strip to at least one inner surface of two water-repellent fabric layers in the above-mentioned flexible electric heating sheet includes the following steps:

[0025] (1) Cut the water-repellent fabric into the required shape and treat it with plasma for 5-6 minutes;

[0026] (2) Use a screen printing plate to scrape the B paste separately, so that there is a gap between each graphene composite substrate coating heating strip. Scrape the paste several times, and dry the sample after each scraping.

[0027] (3) After the coating is applied, copper strips are attached as electrodes along both sides and the middle of the long side using conductive silver paste, and then dried.

[0028] Furthermore, in the above-mentioned flexible electric heating sheet with graphene composite substrate, the graphene composite substrate coating heating strip forms the heating area of ​​the graphene composite substrate, which is bonded and covered by two water-repellent fabric layers through a thermal adhesive.

[0029] Furthermore, in the above-mentioned flexible electric heating sheet with graphene composite substrate, the adhesive coating includes the following steps:

[0030] 1) Apply PU film to the electrode connector: First, fix the cut hot melt adhesive at the connector with a steam iron. The surface temperature of the steam iron should be 110-120℃, the steam temperature should be 98-100℃, the pressure should be 0.3-0.5Mpa, and the dwell time should be 10-20s. After the hot melt adhesive is fixed, immediately cover it with the PU film and fix it with a steam iron.

[0031] 2) Adhere the graphene coated strip area: First, fix the cut hot melt double-sided tape with a steam iron, using the same time, temperature, and pressure as in step 1); after fixing, cover the hot melt adhesive with water-repellent fabric and fix it with a steam iron to make an electric heating element assembly.

[0032] 3) Pressing: Press the electric heating element assembly prepared in step 2) using a semi-automatic pneumatic press: Set the press temperature to 140-160℃, the pressing time to 10-15s, and the pressing pressure to 3-5Mpa.

[0033] 4) Further fixation: After the heat pressing is completed, the electric heating element assembly is further fixed by a fully automatic heat pressing machine. Parameter settings: pressure is 3-4 MPa, time is 15-16 seconds, and temperature is 175-180℃.

[0034] The beneficial effects of this invention are:

[0035] This invention uses graphene composite material as a substrate, takes advantage of its ultra-high conductivity, and coats it onto water-repellent fabric in a strip shape using a printing method. The heating area is enclosed by a "sandwich" structure and connected to a temperature control switch via a power cord, thereby preparing an electric heating element.

[0036] Compared with existing technologies, this invention has the following advantages: 1. This technology uses multiple graphene heating strips connected in parallel, resulting in lower overall resistance and lower heating drive voltage of the heating element. 2. Because the heating strips are connected in parallel, the heating effect of a single heating strip being open-circuited or failing has little impact on the overall heating effect of the heating element. 3. The heating strip coating method avoids the problem of poor air permeability caused by overall coating. 4. The composite coating of graphene and carbon nanotubes has excellent electrothermal characteristics and adhesion. 5. Uniform heating, high thermal efficiency, flexible size control, and easy industrial application. Attached Figure Description

[0037] Figure 1 This is a schematic diagram of the structure of the flexible electric heating sheet based on the graphene composite substrate described in this invention;

[0038] Figure 2 This is a schematic diagram of flexible electric heating sheets of different sizes made of graphene composite substrate in Example 4;

[0039] Figure 3 The temperature curves of sample 1# in Example 4 at voltages of 5V, 4V, and 3V are shown.

[0040] Figure 4 The temperature curves of sample 2# in Example 4 at 5V and 3V voltages;

[0041] Figure 5 The temperature curves of sample 3# in Example 4 at 5V and 3V voltages are shown. Detailed Implementation

[0042] The present invention will now be described in detail with reference to the accompanying drawings:

[0043] like Figure 1 The diagram shows a flexible electric heating element made of graphene composite substrate. The heating element has a sandwich structure, including an outer layer of water-repellent fabric composed of two upper and lower layers, a graphene composite substrate coated heating strip, a copper foil electrode strip, and a power cord located between the upper and lower water-repellent fabric layers.

[0044] The graphene composite substrate coated heating strip is attached to at least one inner surface of the upper and lower water-repellent fabric layers.

[0045] Several graphene composite substrate coated heating strips are arranged in an array of graphene coated strips with intervals, and three copper foil electrode strips are inserted at the top, bottom and middle positions of the graphene coated strips.

[0046] The fourth copper foil electrode strip connects the copper foil electrode strips at both ends in series;

[0047] The copper foil electrode strips at the top and bottom ends are connected in series and then connected in parallel with the copper foil electrode strip in the middle. The two power lines are welded to the electrode joints of the middle and the two ends of the electrode strip, respectively.

[0048] The outer surface of the water-repellent fabric layer is a water-repellent surface, and the inner surface is a non-water-repellent surface;

[0049] The array of graphene coating strips is a rectangular array, in which the graphene composite substrate coating heating strips are parallel to each other;

[0050] The width of the graphene composite substrate coated heating strip is 0.1-1cm, and the width between the graphene composite substrate coated heating strips is 0.1-1cm;

[0051] The graphene composite substrate coated heating strip is formed by coating the graphene composite substrate into lines using a printing method;

[0052] The water-repellent fabric is a plain weave polyester fabric with a silver film coated on one side;

[0053] The graphene composite substrate is prepared by the following steps:

[0054] 1) Preparation of Slurry A

[0055] Raw materials: by mass parts, ① water-based carbon nanotube slurry 1-1.1 parts, ② graphene filter cake 1-1.1 parts, ③ resin 0.4-0.5 parts, ④ water 1-1.1 parts;

[0056] Steps: a. Mix ①②③④ in sequence and stir in a mixer with a speed of 4000-4200 r / min for 1-3 hours to obtain 01# slurry;

[0057] (2) Preparation of B slurry

[0058] Raw materials: by weight parts, ①A slurry 100-105 parts, ②thickener 1-1.05 parts;

[0059] Steps: a. Mix ① and ② and stir in a mixer at a speed of 600-620 r / min for 5-6 min to obtain slurry B, which is the graphene composite substrate.

[0060] The process of attaching the graphene composite substrate coated heating strip to at least one inner surface of two water-repellent fabric layers includes the following steps:

[0061] (1) Cut the water-repellent fabric into the required shape and treat it with plasma for 5-6 minutes;

[0062] (2) Use a screen printing plate to scrape the B paste separately, so that there is a gap between each graphene composite substrate coating heating strip. Scrape the paste several times, and dry the sample after each scraping.

[0063] (3) After the coating is applied, copper strips are attached as electrodes along both sides and the middle of the long side using conductive silver paste, and then dried.

[0064] The graphene composite substrate coating heating strip forms the heating area of ​​the graphene composite substrate, which is bonded and covered by two water-repellent fabric layers through a thermal adhesive.

[0065] The adhesive coating includes the following steps:

[0066] 1) Apply PU film to the electrode connector: First, fix the cut hot melt adhesive at the connector with a steam iron. The surface temperature of the steam iron should be 110-120℃, the steam temperature should be 98-100℃, the pressure should be 0.3-0.5Mpa, and the dwell time should be 10-20s. After the hot melt adhesive is fixed, immediately cover it with the PU film and fix it with a steam iron.

[0067] 2) Adhere the graphene coated strip area: First, fix the cut hot melt double-sided tape with a steam iron, using the same time, temperature, and pressure as in step 1); after fixing, cover the hot melt adhesive with water-repellent fabric and fix it with a steam iron to make an electric heating element assembly.

[0068] 3) Pressing: Press the electric heating element assembly prepared in step 2) using a semi-automatic pneumatic press: Set the press temperature to 140-160℃, the pressing time to 10-15s, and the pressing pressure to 3-5Mpa.

[0069] 4) Further fixation: After the heat pressing is completed, the electric heating element assembly is further fixed by a fully automatic heat pressing machine. Parameter settings: pressure is 3-4 MPa, time is 15-16 seconds, and temperature is 175-180℃.

[0070] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0071] In this embodiment, the materials include:

[0072] Aqueous carbon nanotube paste: purchased from Suqian Xigu Nanotechnology Co., Ltd., model NCT-CZ02, carbon nanotube content 10%, carbon nanotube diameter 15-30um, dispersant content <0.5%, solvent is deionized water;

[0073] Graphene filter cake: purchased from Suqian Xigu Nanotechnology Co., Ltd.; model NCT-YS2E, graphene solid content 20%, particle size less than 15um, number of layers 1-10, dispersant content <0.5%, solvent is deionized water;

[0074] The resin used is SMB-3020 acrylic resin from Bengbu Sany Resin Technology Co., Ltd.

[0075] The thickener used is Qingdao Bateng Chemical Co., Ltd., model QB-53B, which is an aqueous emulsion of polyacrylate.

[0076] Example 1

[0077] Preparation of graphene composite substrates

[0078] The graphene composite substrate is prepared by the following steps:

[0079] 1) Preparation of Slurry A

[0080] Raw materials: ① 1 kg of water-based carbon nanotube slurry, ② 1.1 kg of graphene filter cake, ③ 0.4 kg of resin, ④ 1 kg of water;

[0081] Steps: a. Mix ①②③④ in sequence and stir in a mixer with a speed of 4000-4200 r / min for 1 hour to obtain 01# slurry;

[0082] (2) Preparation of B slurry

[0083] Ingredients: ① 100g of slurry A, ② 1g of thickener;

[0084] Steps: a. Mix ① and ② and stir for 5 minutes in a mixer with a speed of 600-620 r / min to obtain slurry B, which is the graphene composite substrate.

[0085] Example 2

[0086] Preparation of graphene composite substrates

[0087] The graphene composite substrate is prepared by the following steps:

[0088] 1) Preparation of Slurry A

[0089] Raw materials: ① 1.05 kg of water-based carbon nanotube slurry, ② 1.05 kg of graphene filter cake, ③ 0.45 kg of resin, ④ 1.05 kg of water;

[0090] Steps: a. Mix ①②③④ in sequence and stir in a mixer with a speed of 4000-4200 r / min for 2 hours to obtain 01# slurry;

[0091] (2) Preparation of B slurry

[0092] Raw materials: by weight parts, ①A slurry 102g, ②thickener 1.05g;

[0093] Steps: a. Mix ① and ② and stir in a mixer at a speed of 600-620 r / min for 5.5 min to obtain slurry B, which is the graphene composite substrate.

[0094] Example 3

[0095] Preparation of graphene composite substrates

[0096] The graphene composite substrate is prepared by the following steps:

[0097] 1) Preparation of Slurry A

[0098] Raw materials: by mass parts, ① 1.1 kg of water-based carbon nanotube slurry, ② 1.1 kg of graphene filter cake, ③ 0.5 kg of resin, ④ 1.1 kg of water;

[0099] Steps: a. Mix ①②③④ in sequence and stir in a mixer with a speed of 4000-4200 r / min for 2 hours to obtain 01# slurry;

[0100] (2) Preparation of B slurry

[0101] Raw materials: by weight parts, ①A slurry 105g, ②thickener 1.02g;

[0102] Steps: a. Mix ① and ② and stir for 6 minutes in a mixer with a speed of 600-620 r / min to obtain slurry B, which is the graphene composite substrate.

[0103] Example 4

[0104] Experiment on the coating process of graphene composite substrate heating strip

[0105] This embodiment uses the graphene composite substrate prepared in Example 2.

[0106] This experiment includes the following steps:

[0107] 1) Water-repellent fabric is selected as waterproof membrane: the composition is 100% polyester plain weave woven fabric, the water-repellent surface is coated with silver film, the weight is 60g / m2, and the fabric is waterproof and heat-resistant.

[0108] 2) Cut 6 pieces of waterproof membrane fabric into sizes of 12×10cm, 17×12cm and 24×14cm respectively. Cut two pieces of each size and treat the 6 sample fabrics with plasma for 5-6 minutes.

[0109] 3) such as Figure 2As shown in AC, slurry B was applied using a screen printing plate, with a 0.5cm gap between each graphene heating strip. The dimensions were 8×6cm, 13×7.5cm, and 20×10cm, labeled as samples 1#, 1-1#, 2#, 2-2#, 3#, and 3-1#, respectively. Samples 1# and 1-1# were applied once using the screen printing plate, samples 2# and 2-1# were applied twice, and samples 3# and 3-1# were applied three times. After each application, the samples were dried in a 60℃ oven for 0.5 hours.

[0110] 4) After the soil is scraped and coated on each sample, copper strips are attached as electrodes along both sides and the middle of the long side using conductive silver paste. The samples are then dried in a 60℃ oven for 4 hours. Preparation is now complete.

[0111] This embodiment also includes verifying the prepared sample by resistance testing.

[0112] Includes the following steps:

[0113] Solder the a and b terminals of samples 1#, 2#, and 3# to the positive and negative terminals of the switch using a soldering iron, and test the resistance value. Connect samples 1-1#, 2-1#, and 3-1# in parallel with a wire and connect them to the switch, and perform resistance testing to verify the results. The results are shown in Table 1 (weight gain and resistance after each coating application) and Table 2 (resistance of the samples after soldering the switch).

[0114] Table 1 Weight gain and resistance per coat application

[0115]

[0116] Note: The resistance is the resistance over a 1cm length of the heating strip.

[0117] Table 2 shows the resistance of samples after the switches were welded.

[0118] sample resistance 1# 2.7 1-1# 2.8 2# 2.5 2-1# 2.8 3# 2.5 3-1# 2.6

[0119] As shown in Tables 1 and 2, different coating processes can be applied according to different fabric sizes to ensure resistance stability. Furthermore, the resistance values ​​of the three heating elements connected in parallel also meet the consistency requirements after testing. This allows for the production of products with multiple parts heating simultaneously.

[0120] Example 5

[0121] Experiment on bonding process of graphene composite substrate flexible electric heating sheet

[0122] (1) Purpose: To prevent the graphene composite substrate from slipping during use and causing heating problems, and to prevent injury from direct contact with the human body and damage to the heating element during washing and cleaning, the heating area needs to be encapsulated to isolate it from the outside environment. Considering that the heating element is used in the field of smart wearable clothing, the encapsulation material must be soft, thin, waterproof, breathable, high temperature resistant, non-allergenic, highly elastic, and corrosion resistant, and also have a certain strength. Textile adhesives are soft, thin, easy to prepare, and have a certain strength after ironing. Therefore, waterproof membrane cloth, textile hot melt double-sided adhesive, and PU film are selected as encapsulation materials for this electric heating element. At the same time, during the preparation process, the ironing temperature, time, and pressure, as well as the pressing temperature, time, and pressure, need to be repeatedly tested to select the optimal temperature, time, and pressure. The prepared electric heating element is then washed and its strength is tested.

[0123] (2) Equipment selection: Semi-automatic double-station pneumatic ironing machine, steam iron, Oshima fully automatic ironing machine

[0124] (3) Model: According to the requirements of the subsequent heating parts, the waterproof membrane and hot melt double-sided tape are cut into three sizes: 12×10cm, 17×12cm and 24×14cm. The hot melt adhesive and PU film are cut into rectangles of 4x10cm, 5x12cm and 6x14cm.

[0125] (4) Adhesion process:

[0126] Let's take the production of a 17×12cm size as an example:

[0127] ① To ensure the sealing and waterproof performance of the electrode and power cord interface, first apply a PU film to the electrode connector. During operation, first fix the connector with a pre-cut piece of hot melt adhesive using a steam iron. The surface temperature of the steam iron should be 110-120℃, the steam temperature 98-100℃, the pressure 0.4 MPa, and the dwell time 15 seconds. After the hot melt adhesive is fixed, immediately cover it with a 5x12cm piece of PU film and fix it with a steam iron. Do not allow the wire to deviate during ironing.

[0128] ② Use hot melt double-sided tape to fully bond the PU film and the non-printed waterproof fabric together. To do this, first use a steam iron to fix the cut hot melt double-sided tape, using the same time, temperature, and pressure as described above. After fixing, place the waterproof film over the hot melt tape and secure it with a steam iron.

[0129] ③ After the above operations are completed, the electric heating element assembly is pressed using a semi-automatic pneumatic heat press. This heat press can be set with temperature, pressing time, and pressure, thus ensuring that the "sandwich" assembly of the electric heating elements is fully bonded, has better strength, and will not peel off after repeated washing. After repeated experiments and tests, the heat press temperature was set to 150℃, the pressing time to 12s, and the pressing pressure to 4Mpa.

[0130] ④ After pressing, the electric heating element assembly is further fixed using the Osimer fully automatic pressing machine. Parameter settings: pressure is 3.5MPa, time speed is 15-16 seconds, temperature is 175-180℃. After pressing, place it in a normal temperature and pressure environment for more than 6 hours before testing.

[0131] The electric heating element prepared above was subjected to a water washing test. After 30 washes, the results showed that there was no peeling, detachment, or misalignment of the heating element components, proving that the process has good reliability.

[0132] Example 6

[0133] Temperature test

[0134] Samples 1#, 2#, and 3# prepared in Example 4 were used to prepare electric heating sheets using a graphene composite substrate flexible electric heating sheet bonding process. Temperature tests were then conducted. This invention can achieve different heating temperatures by adjusting the spacing and width of the printed strips on the graphene composite substrate. Taking a strip width of 0.5cm as an example, the temperature test results are as follows.

[0135] (1) Sample 1# reaches a temperature of approximately 45℃ at 5V, and approximately 40℃ and 36℃ at 4V and 3V respectively, as shown in the temperature curves. Figure 3 As shown.

[0136] (2) Sample 2# reaches a temperature of approximately 43℃ at 5V and approximately 35℃ at 3V, as shown in the temperature curves. Figure 4 As shown.

[0137] (3) Sample #3 reaches a temperature of approximately 41℃ at 5V and approximately 32℃ at 3V, as shown in the temperature curves. Figure 5 As shown.

[0138] Depend on Figure 3-5It is evident that the electric heating element developed and manufactured in this invention exhibits excellent heating performance, with the heating temperature continuously increasing as the voltage rises. When the width of the heating substrate coating strip is 0.5 cm, applying a 5V voltage achieves a heating temperature of 41-45 degrees Celsius, while applying a 3V voltage achieves a heating temperature of 32-36 degrees Celsius. Compared to existing technologies, it has the following advantages: 1. This technology employs multiple graphene heating strips connected in parallel, resulting in lower overall resistance and lower heating drive voltage for the heating element. 2. Due to the parallel connection of the heating strips, a single open circuit or failure of a heating strip has minimal impact on the overall heating effect of the heating element. 3. The use of a heating strip coating method avoids the problem of poor air permeability caused by an overall coating. 4. The composite coating of graphene and carbon nanotubes possesses excellent electrothermal characteristics and durability. 5. It provides uniform heating, high thermal efficiency, flexible size control, and ease of industrial application.

[0139] Of course, the above description is not intended to limit the present invention, and the present invention is not limited to the examples given above. Any changes, modifications, additions or substitutions made by those skilled in the art within the scope of the present invention should also fall within the protection scope of the present invention.

Claims

1. A flexible electric heating element based on graphene composite substrate, characterized in that, The heating element has a sandwich structure, comprising an outer layer of water-repellent fabric composed of two layers, and a layer located between the two water-repellent fabric layers. Graphene composite substrate coated heating strip, copper foil electrode strip and power cord; The graphene composite substrate coated heating strip is attached to at least one inner surface of the upper and lower water-repellent fabric layers. Several graphene composite substrate coated heating strips are arranged in an array of graphene coated strips with intervals, and three copper foil electrode strips are inserted at the top, bottom and middle positions of the graphene coated strips. The fourth copper foil electrode strip connects the copper foil electrode strips at both ends in series; The copper foil electrode strips at the top and bottom ends are connected in series and then connected in parallel with the copper foil electrode strip in the middle. The two power lines are welded to the electrode joints of the middle and the two ends of the electrode strip, respectively.

2. The graphene composite substrate flexible electric heating element according to claim 1, characterized in that, The outer surface of the water-repellent fabric layer is a water-repellent surface, and the inner surface is either a water-repellent surface or a non-water-repellent surface.

3. The graphene composite substrate flexible electric heating element according to claim 1, characterized in that, Two power cords extend from the heating element and connect to a power bank, with a switch installed between the power cords and the power bank.

4. The graphene composite substrate flexible electric heating sheet according to claim 1, characterized in that, The width of the graphene composite substrate coated heating strip is 0.5cm, and the width between the graphene composite substrate coated heating strips is 0.5cm.

5. The graphene composite substrate flexible electric heating plate according to claim 1, characterized in that, The graphene composite substrate coated heating strip is formed by printing the graphene composite substrate into lines.

6. The graphene composite substrate flexible electric heating element according to claim 1, characterized in that, The water-repellent fabric is a plain-weave polyester fabric with at least one side coated with a silver film.

7. The graphene composite substrate flexible electric heating plate according to claim 1, characterized in that, The graphene composite substrate is prepared by the following steps: 1) Preparation of Slurry A Raw materials: by mass parts, ① water-based carbon nanotube slurry 1-1.1 parts, ② graphene filter cake 1-1.1 parts, ③ resin 0.4-0.5 parts, ④ water 1-1.1 parts; Steps: a. Mix ①②③④ in sequence and stir in a mixer with a speed of 4000-4200 r / min for 1-3 hours to obtain 01# slurry; (2) Preparation of B slurry Raw materials: by weight parts, ①A slurry 100-105 parts, ②thickener 1-1.05 parts; Steps: a. Mix ① and ② and stir in a mixer at a speed of 600-620 r / min for 5-6 min to obtain slurry B, which is the graphene composite substrate.

8. A flexible electric heating element based on a graphene composite substrate according to claim 7, characterized in that, The process of attaching a graphene composite substrate coated heating strip to at least one inner surface of two water-repellent fabric layers includes the following steps: (1) Cut the water-repellent fabric into the required shape and treat it with plasma for 5-6 minutes; (2) Use a screen printing plate to scrape the B paste separately, so that there is a gap between each graphene composite substrate coating heating strip. Scrape the paste several times, and dry the sample after each scraping. (3) After the coating is applied, copper strips are attached as electrodes along both sides and the middle of the long side using conductive silver paste, and then dried.

9. A flexible electric heating element based on a graphene composite substrate according to claim 1, characterized in that, The graphene composite substrate coating heating strip forms the heating area of ​​the graphene composite substrate, which is bonded and covered by two water-repellent fabric layers through a thermal adhesive.

10. A flexible electric heating element based on a graphene composite substrate according to claim 9, characterized in that, The adhesive coating includes the following steps: 1) Apply PU film to the electrode connector: First, fix the cut hot melt adhesive at the connector with a steam iron. The surface temperature of the steam iron should be 110-120℃, the steam temperature should be 98-100℃, the pressure should be 0.3-0.5Mpa, and the dwell time should be 10-20s. After the hot melt adhesive is fixed, immediately cover it with the PU film and fix it with a steam iron. 2) Adhere the graphene coated strip area: First, fix the cut hot melt double-sided tape with a steam iron, using the same time, temperature, and pressure as in step 1); after fixing, cover the hot melt adhesive with water-repellent fabric and fix it with a steam iron to make an electric heating element assembly. 3) Pressing: Press the electric heating element assembly prepared in step 2) using a semi-automatic pneumatic press: Set the press temperature to 140-160℃, the pressing time to 10-15s, and the pressing pressure to 3-5Mpa. 4) Further fixation: After the heat pressing is completed, the electric heating element assembly is further fixed by a fully automatic heat pressing machine. Parameter settings: pressure is 3-4 MPa, time is 15-16 seconds, and temperature is 175-180℃.

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