An aqueous graphene electric heating coating
By constructing a three-dimensional conductive network using amino-modified reduced graphene oxide and composite additives, the problems of oxidation corrosion and graphene agglomeration in electrothermal coatings under high temperature and high humidity environments were solved, achieving improved high-efficiency electrothermal performance and weather resistance.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- ZHONGBAOXIN TECHNOLOGY (BEIJING) CO LTD
- Filing Date
- 2026-05-12
- Publication Date
- 2026-06-09
AI Technical Summary
Existing electrothermal coatings are prone to oxidation and corrosion in high temperature and high humidity environments, which leads to increased resistivity, decreased heating performance, and shortened lifespan. Furthermore, graphene tends to agglomerate in aqueous systems, making it difficult to disperse, resulting in weak interfacial bonding, low efficiency in constructing conductive pathways, and the need to improve its electrothermal performance and weather resistance.
Amino-modified reduced graphene oxide was used as the main conductive filler, and a three-dimensional conductive network was constructed with graphene through epoxy-modified carbon nanotubes in the composite additive. Hindered phenolic antioxidants in the composite additive were used to capture free radicals, enhance interfacial bonding, and improve conductivity and weather resistance.
The graphene electrothermal coating achieves high conductivity and stability, extends service life, improves electrothermal performance and weather resistance, and ensures long-term stability of the conductive path and the coating's heat oxidation resistance.
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Figure CN122168146A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of functional coatings technology, specifically relating to a water-based graphene electrothermal coating. Background Technology
[0002] Electrothermal coatings are a new type of functional coating developed based on conductive coatings, possessing excellent electrothermal properties. With the advancement of science and technology, electrothermal coatings have broad application prospects in all aspects of production and daily life.
[0003] Traditional electrothermal coatings primarily rely on metal powders (such as silver, copper, and nickel) as conductive fillers. In high-temperature and high-humidity environments, these metals are prone to oxidation and corrosion, leading to a sharp increase in coating resistivity, decreased heating performance, and shortened lifespan. Oxidation products can also damage the coating's insulation, causing short circuits or even fires. Furthermore, metal fillers have high density, are prone to settling, and have poor compatibility with organic matrices, resulting in weak coating adhesion and easy peeling from the substrate. Graphene, as an emerging two-dimensional carbon material, is an allotrope of carbon and an inorganic non-metallic material with excellent electrical conductivity, thermal conductivity, and chemical stability. It is an ideal conductive filler to replace metals. Its inorganic non-metallic properties fundamentally eliminate the problems of oxidation and rusting. Moreover, the infrared radiation generated by graphene-based electrothermal coatings when energized is concentrated in the 3-15μm wavelength range, falling within the mid-infrared category. Besides its heating applications, this thermal radiation also has therapeutic and health benefits for the human body. Simultaneously, using graphene electrothermal materials is environmentally friendly and energy-saving, aligning with national sustainable development strategies and making it a very promising heating material.
[0004] Furthermore, traditional electrothermal coatings are mostly solvent-based, but organic solvents pose environmental pollution and safety risks, including volatile or contact toxicity, flammability, explosiveness, corrosiveness, and the generation of photochemical smog, and even significant carcinogenic risks. To meet the demands of a green and environmentally friendly era, research on water-based electrothermal coatings has gradually attracted widespread attention. However, graphene sheets exhibit strong van der Waals forces, making them prone to aggregation and dispersion in water-based systems. This results in discontinuous conductive networks and uneven coating resistance. Secondly, the interfacial bonding between graphene and polymer matrices (such as polyurethane) is weak, relying solely on physical adsorption. Under thermal or mechanical stress, interfacial delamination easily occurs, leading to conductivity failure. Finally, relying solely on graphene, the efficiency of conductive pathway construction still has room for improvement, and electrothermal performance needs enhancement. Moreover, the coating's weather resistance needs to be strengthened under long-term electrothermal cycling conditions. Summary of the Invention
[0005] To address the shortcomings of existing technologies, this invention provides a water-based graphene electrothermal coating to solve the problem that the electrothermal performance and weather resistance of existing electrothermal coatings need to be improved.
[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows: A water-based graphene electrothermal coating, comprising component A, component B, and component C; Component A, by weight, comprises the following raw materials: 30-40 parts of aqueous hydroxy acrylic acid dispersion; 6-10 parts deionized water; 3-5 parts wetting and dispersing agent; Leveling agent 0.5-1 part; 0.5-1 part defoamer; Component B, by weight, comprises the following raw materials: 40-60 parts of water-based isocyanate curing agent; 30-50 parts of co-solvent; Component C, by weight, comprises the following raw materials: 30-50 parts of amino-modified reduced graphene oxide; 30-50 parts of compound additives; Dispersant 0.5-1 part; 80-120 parts deionized water; The composite additive is prepared by the following steps: 3,5-Bis(tert-butyl)-4-hydroxyphenylpropionyl chloride was reacted with triethylenetetramine to prepare an amino-modified hindered phenolic antioxidant; the amino-modified hindered phenolic antioxidant was reacted with epoxy-modified carbon nanotubes to obtain a composite additive.
[0007] Preferably, in component B, the co-solvent includes ethylene glycol butyl ether acetate.
[0008] Preferably, the preparation method of the composite additive specifically includes: S11. Dissolve 3,5-bis(tert-butyl)-4-hydroxyphenylpropionyl chloride in benzene to obtain a 3,5-bis(tert-butyl)-4-hydroxyphenylpropionyl chloride solution; dissolve triethylenetetramine in deionized water to obtain a triethylenetetramine solution; add the triethylenetetramine solution dropwise to the 3,5-bis(tert-butyl)-4-hydroxyphenylpropionyl chloride solution. After the addition is complete, add alkali solution to adjust the pH value to 9-10. Allow the reaction to proceed. After the reaction is complete, separate and purify the solution to obtain an amino-modified hindered phenolic antioxidant. S12. Dissolve the amino-modified hindered phenolic antioxidant in benzene, add epoxy-modified carbon nanotubes, and react. After the reaction is complete, filter, wash, and dry to obtain the composite additive.
[0009] Preferably, in S11, the molar ratio of 3,5-bis(tert-butyl)-4-hydroxyphenylpropionyl chloride to triethylenetetramine is 1:(1.05-1.1); in the 3,5-bis(tert-butyl)-4-hydroxyphenylpropionyl chloride solution, the mass-to-volume ratio of 3,5-bis(tert-butyl)-4-hydroxyphenylpropionyl chloride to benzene is 1 g / (8-12) mL; in the triethylenetetramine solution, the mass-to-volume ratio of triethylenetetramine to deionized water is 1 g / (20-30) mL, and the reaction conditions are at room temperature (25°C) for 20-30 h.
[0010] Preferably, the alkaline solution comprises an aqueous solution of potassium carbonate.
[0011] Preferably, in S12, the mass ratio of amino-modified hindered phenolic antioxidant, benzene, and epoxy-modified carbon nanotubes is 40.7:(200-300):(10-20), and the reaction conditions are under a nitrogen atmosphere and at a temperature of 50-60°C for 10-15 hours.
[0012] Preferably, the epoxy-modified carbon nanotubes are prepared by the following steps: Carbon nanotubes (CNTs) were added to a mixed acid prepared from concentrated sulfuric acid and concentrated nitric acid, dispersed by ultrasonication, and then reacted. After the reaction was completed, the mixture was filtered, washed, and dried to obtain acidified carbon nanotubes. γ-(2,3-epoxypropoxy)propyltrimethoxysilane (silane coupling agent KH560) was added to ethanol, the pH was adjusted to 4.5-5.5, acidified carbon nanotubes were added, and the mixture was ultrasonically dispersed and reacted. After the reaction was completed, the mixture was filtered, washed, and dried to obtain epoxy-modified carbon nanotubes.
[0013] Preferably, when preparing the acidified carbon nanotubes, the mass ratio of carbon nanotubes to mixed acid is 1:(10-20), and the reaction conditions are stirring at 40-50℃ for 10-15 hours; in the mixed acid, the volume ratio of concentrated sulfuric acid to concentrated nitric acid is 3:1, the concentration of concentrated sulfuric acid is 98wt%, and the concentration of concentrated nitric acid is 68wt%; when preparing the epoxy-modified carbon nanotubes, the mass ratio of γ-(2,3-epoxypropoxy)propyltrimethoxysilane, ethanol, and acidified carbon nanotubes is (2-3):(100-200):1, and the reaction conditions are stirring at 50-70℃ for 4-8 hours.
[0014] Preferably, the amino-modified reduced graphene oxide in component C is prepared by the following steps: S21. Add graphene oxide to an ethanol aqueous solution, disperse it by ultrasonication, add triethylamine and N-aminoethyl-3-aminopropylmethyldimethoxysilane, react, filter and wash after the reaction is completed to obtain amino-modified graphene oxide. S22. Add amino-modified graphene oxide to deionized water, disperse it by ultrasonication, add ammonia and alkaline solution, and react. After the reaction is completed, filter, wash, and dry to obtain amino-modified reduced graphene oxide.
[0015] Preferably, in S21, the mass ratio of graphene oxide, aqueous ethanol solution, triethylamine, and N-aminoethyl-3-aminopropylmethyldimethoxysilane is 1:(20-30):(0.8-1.2):(6-10), and the reaction condition is stirring at room temperature for 20-30 hours.
[0016] Preferably, the ethanol aqueous solution is a 90wt% ethanol aqueous solution.
[0017] Preferably, in S22, the mass ratio of amino-modified graphene oxide, deionized water, ammonia, and alkaline solution is 1:(400-600):(100-200):(20-30), and the reaction conditions are reflux reaction at 75-85℃ for 20-30h under a nitrogen atmosphere.
[0018] Preferably, the concentration of the ammonia solution is 25 wt%, and the alkaline solution is a 1 mol / L potassium hydroxide aqueous solution.
[0019] Preferably, in component C, the dispersant includes polyethylene glycol.
[0020] Preferably, the mass ratio of component A, component B and component C is 100:25:(15-20).
[0021] Compared with the prior art, the beneficial effects of the present invention are as follows: In this invention, by introducing amino-modified reduced graphene oxide as the main conductive filler, not only is the high conductivity of graphene itself retained, but the amino functional groups on its surface can also chemically react with the water-based isocyanate curing agent in component B, thereby firmly bonding it to the polyurethane resin matrix. This effectively prevents interfacial peeling and migration of graphene due to weak physical adsorption during use, ensuring the long-term stability of the conductive pathway. At the same time, the composite additive in component C (composed of antioxidant-grafted carbon nanotubes) and graphene can synergistically construct a point-to-surface three-dimensional conductive network in the coating. The carbon nanotubes act as bridges, connecting the dispersed graphene sheets, significantly reducing the percolation threshold of the coating and improving the conductivity efficiency, thereby obtaining higher and more stable heating power and heating temperature. The composite additive in component C is prepared by grafting hindered phenolic antioxidants onto epoxy-modified carbon nanotubes as the backbone and triethylenetetramine as the bridging agent through chemical bonds. When the electrothermal coating is working, the highly efficient hindered phenolic antioxidant molecules grafted onto the carbon nanotubes can continuously and stably capture and eliminate free radicals generated by the resin matrix due to heat and electric field, effectively inhibiting the thermal oxidative degradation of the polymer chain, thereby delaying the aging and performance degradation of the coating and improving the service life and reliability of the electrothermal coating under long-term electric thermal cycling conditions. Furthermore, the triethylenetetramine reacts with 3,5-bis(tert-butyl)-4-hydroxyphenylpropionyl chloride and epoxy-modified carbon nanotubes through the amino groups at the terminal positions to achieve chemical bonding between the carbon nanotubes and the hindered phenolic antioxidants. At the same time, the introduced secondary amino groups can also react chemically with the water-based isocyanate curing agent in component B, thereby firmly bonding to the polyurethane resin matrix, which can further improve the electrothermal performance and weather resistance of the coating. Attached Figure Description
[0022] Figure 1 This is a schematic diagram of the reaction for preparing the composite additive in this invention. Detailed Implementation
[0023] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.
[0024] Example 1 This embodiment discloses a method for preparing epoxy-modified carbon nanotubes, including the following steps: Carbon nanotubes were added to a mixed acid prepared by mixing 98wt% concentrated sulfuric acid and 68wt% concentrated nitric acid in a volume ratio of 3:1, with a mass ratio of carbon nanotubes to mixed acid of 1:15. After ultrasonic dispersion at 50kHz for 1 hour, the mixture was stirred at 200r / min for 12 hours at 45℃. After the reaction was completed, the mixture was filtered, washed three times with 0.1mol / L sodium hydroxide aqueous solution, and then washed with deionized water until neutral. The mixture was then dried in a vacuum drying oven at 50℃ until constant weight to obtain acidified carbon nanotubes. γ-(2,3-epoxypropoxy)propyltrimethoxysilane was added to ethanol, and the pH was adjusted to 5 with 0.5 mol / L hydrochloric acid solution. Acidified carbon nanotubes were then added. The mass ratio of γ-(2,3-epoxypropoxy)propyltrimethoxysilane, ethanol, and acidified carbon nanotubes was 2.5:150:1. After ultrasonic dispersion at 50 kHz for 1 h, the mixture was stirred at 200 r / min for 6 h at 60 °C. After the reaction was completed, the mixture was filtered, and excess γ-(2,3-epoxypropoxy)propyltrimethoxysilane was removed by washing with ethanol. The mixture was then dried in a vacuum drying oven at 50 °C until constant weight was obtained to obtain epoxy-modified carbon nanotubes.
[0025] Example 2 This embodiment discloses a method for preparing a composite additive, including the following steps: S11. Take 3,5-bis(tert-butyl)-4-hydroxyphenylpropionyl chloride and triethylenetetramine, with a molar ratio of 1:1.08. Dissolve 3,5-bis(tert-butyl)-4-hydroxyphenylpropionyl chloride in benzene, with a mass-to-volume ratio of 1 g / 10 mL, to obtain a 3,5-bis(tert-butyl)-4-hydroxyphenylpropionyl chloride solution. Dissolve triethylenetetramine in deionized water, with a mass-to-volume ratio of 1 g / 25 mL, to obtain a triethylenetetramine solution. Under ice-water bath conditions, add the triethylenetetramine solution dropwise to the 3,5-bis(tert-butyl)-4-hydroxyphenylpropionyl chloride solution over a period of 30 min. Afterwards, 20wt% potassium carbonate aqueous solution was added dropwise to adjust the pH to 9.5, and the reaction was carried out at room temperature for 24 hours. After the reaction was completed, the reaction mixture was obtained. The reaction mixture was separated and purified. The separation and purification process included: adding 1mol / L hydrochloric acid solution dropwise to the reaction mixture until the pH of the reaction mixture was 3, allowing it to stand, separating the layers, taking the lower acidic aqueous phase, adding saturated potassium carbonate aqueous solution dropwise to the acidic aqueous phase to adjust the pH to 10, obtaining the alkalized aqueous phase, adding 1 / 2 volume of dichloromethane to the alkalized aqueous phase for extraction, taking the organic phase, repeating the extraction process of the alkalized aqueous phase 3 times, combining the organic phases, adding anhydrous sodium sulfate to the organic phase for drying, filtering, and rotary evaporating the filtrate at 30℃ to remove the solvent, obtaining the amino-modified hindered phenol antioxidant. S12. Dissolve the amino-modified hindered phenolic antioxidant in benzene, add epoxy-modified carbon nanotubes, and the mass ratio of amino-modified hindered phenolic antioxidant, benzene, and epoxy-modified carbon nanotubes is 40.7:250:15. React at 55°C for 12 hours under a nitrogen atmosphere. After the reaction is complete, filter, wash with ethanol, and dry in a vacuum drying oven at 50°C to constant weight to obtain the composite additive. Among them, the epoxy-modified carbon nanotubes are the epoxy-modified carbon nanotubes prepared in Example 1.
[0026] Example 3 This embodiment discloses a method for preparing amino-modified reduced graphene oxide, including the following steps: S21. Graphene oxide was added to a 90wt% ethanol aqueous solution and ultrasonically dispersed. Then, triethylamine and N-aminoethyl-3-aminopropylmethyldimethoxysilane were added. The mass ratio of graphene oxide, 90wt% ethanol aqueous solution, triethylamine, and N-aminoethyl-3-aminopropylmethyldimethoxysilane was 1:25:1:8. The mixture was stirred and reacted at room temperature for 24 hours. After the reaction was completed, the mixture was filtered and washed three times with ethanol to obtain amino-modified graphene oxide. S22. Add amino-modified graphene oxide to deionized water and ultrasonically disperse it at 50 kHz for 30 min. Then add 25 wt% ammonia and 1 mol / L potassium hydroxide aqueous solution. The mass ratio of amino-modified graphene oxide, deionized water, 25 wt% ammonia, and 1 mol / L potassium hydroxide aqueous solution is 1:500:150:25. Reflux the reaction at 80 ℃ for 24 h under a nitrogen atmosphere. After the reaction is complete, filter the solution, wash it with deionized water until neutral, and dry it in a vacuum drying oven at 50 ℃ until constant weight to obtain amino-modified reduced graphene oxide.
[0027] Example 4 This embodiment discloses an aqueous graphene electrothermal coating, comprising component A, component B, and component C; Component A, by weight, comprises the following raw materials: 30 parts of aqueous hydroxy acrylic acid dispersion; 6 parts deionized water; 3 parts wetting and dispersing agent; 0.5 parts leveling agent; 0.5 parts of defoamer; Component B, by weight, comprises the following raw materials: 40 parts of water-based isocyanate curing agent; 30 parts of ethylene glycol butyl ether acetate; Component C, by weight, comprises the following raw materials: 30 parts of amino-modified reduced graphene oxide; 30 parts of compound additives; 0.5 parts polyethylene glycol; 80 parts deionized water; The mass ratio of component A, component B and component C is 100:25:20; The composite additive is the composite additive prepared in Example 2, and the amino-modified reduced graphene oxide is the amino-modified reduced graphene oxide prepared in Example 3.
[0028] Example 5 This embodiment discloses an aqueous graphene electrothermal coating, comprising component A, component B, and component C; Component A, by weight, comprises the following raw materials: 40 parts of aqueous hydroxy acrylic acid dispersion; 10 parts deionized water; 5 parts wetting and dispersing agent; 1 part leveling agent; 1 part defoamer; Component B, by weight, comprises the following raw materials: 60 parts of water-based isocyanate curing agent; 50 parts of ethylene glycol butyl ether acetate; Component C, by weight, comprises the following raw materials: 50 parts of amino-modified reduced graphene oxide; 50 parts of compound additives; 1 part polyethylene glycol; 120 parts deionized water; The mass ratio of component A, component B and component C is 100:25:15; The composite additive is the composite additive prepared in Example 2, and the amino-modified reduced graphene oxide is the amino-modified reduced graphene oxide prepared in Example 3.
[0029] Example 6 This embodiment discloses an aqueous graphene electrothermal coating, comprising component A, component B, and component C; Component A, by weight, comprises the following raw materials: 35 parts of aqueous hydroxy acrylic acid dispersion; 8 parts deionized water; 4 parts wetting and dispersing agent; 0.75 parts leveling agent; 0.75 parts of defoamer; Component B, by weight, comprises the following raw materials: 50 parts of water-based isocyanate curing agent; 40 parts of ethylene glycol butyl ether acetate; Component C, by weight, comprises the following raw materials: 40 parts of amino-modified reduced graphene oxide; 40 parts of compound additives; 0.75 parts of polyethylene glycol; 100 parts deionized water; The mass ratio of component A, component B and component C is 100:25:17; The composite additive is the composite additive prepared in Example 2, and the amino-modified reduced graphene oxide is the amino-modified reduced graphene oxide prepared in Example 3.
[0030] Comparative Example 1 This comparative example discloses a method for preparing a composite additive, comprising the following steps: S11. Carbon nanotubes were added to a mixed acid prepared by mixing 98wt% concentrated sulfuric acid and 68wt% concentrated nitric acid in a volume ratio of 3:1, with a mass ratio of carbon nanotubes to mixed acid of 1:15. After ultrasonic dispersion at 50kHz for 1 hour, the mixture was stirred at 200r / min at 45℃ for 12 hours. After the reaction was completed, the mixture was filtered, washed three times with 0.1mol / L sodium hydroxide aqueous solution, and then washed with deionized water until neutral. The mixture was then dried in a vacuum drying oven at 50℃ until constant weight to obtain acidified carbon nanotubes. 3-Aminopropyltriethoxysilane (silane coupling agent KH550) was added to ethanol, and the pH was adjusted to 5 with 0.5 mol / L hydrochloric acid solution. Acidified carbon nanotubes were then added. The mass ratio of 3-aminopropyltriethoxysilane, ethanol, and acidified carbon nanotubes was 2.5:150:1. After ultrasonic dispersion at 50 kHz for 1 h, the mixture was stirred at 200 r / min at 60 °C for 6 h. After the reaction was completed, the mixture was filtered, and excess 3-aminopropyltriethoxysilane was removed by washing with ethanol. The mixture was then dried in a vacuum drying oven at 50 °C until constant weight to obtain amino-modified carbon nanotubes. S12. Dissolve 3,5-bis(tert-butyl)-4-hydroxyphenylpropionyl chloride in benzene, add amino-modified carbon nanotubes, the mass ratio of 3,5-bis(tert-butyl)-4-hydroxyphenylpropionyl chloride, benzene, and amino-modified carbon nanotubes is 29.7:250:15, add 20wt% potassium carbonate aqueous solution to adjust the pH to 9.5, react at room temperature for 24 h, after the reaction is completed, filter, wash with ethanol, and dry in a vacuum drying oven at 50℃ to constant weight to obtain the composite additive.
[0031] Comparative Example 2 This comparative example discloses an aqueous graphene electrothermal coating, comprising component A, component B, and component C; Component A, by weight, comprises the following raw materials: 30 parts of aqueous hydroxy acrylic acid dispersion; 6 parts deionized water; 3 parts wetting and dispersing agent; 0.5 parts leveling agent; 0.5 parts of defoamer; Component B, by weight, comprises the following raw materials: 40 parts of water-based isocyanate curing agent; 30 parts of ethylene glycol butyl ether acetate; Component C, by weight, comprises the following raw materials: 30 parts of amino-modified reduced graphene oxide; 30 parts of compound additives; 0.5 parts polyethylene glycol; 80 parts deionized water; The mass ratio of component A, component B and component C is 100:25:20; The composite additive is the composite additive prepared in Comparative Example 1, and the amino-modified reduced graphene oxide is the amino-modified reduced graphene oxide prepared in Example 3.
[0032] Comparative Example 3 This comparative example discloses an aqueous graphene electrothermal coating, comprising component A, component B, and component C; Component A, by weight, comprises the following raw materials: 30 parts of aqueous hydroxy acrylic acid dispersion; 6 parts deionized water; 3 parts wetting and dispersing agent; 0.5 parts leveling agent; 0.5 parts of defoamer; Component B, by weight, comprises the following raw materials: 40 parts of water-based isocyanate curing agent; 30 parts of ethylene glycol butyl ether acetate; Component C, by weight, comprises the following raw materials: 30 parts graphene; 30 parts of compound additives; 0.5 parts polyethylene glycol; 80 parts deionized water; The mass ratio of component A, component B and component C is 100:25:20; The composite additive is the composite additive prepared in Comparative Example 1.
[0033] In the above embodiments and comparative examples, the carbon nanotubes are multi-walled carbon nanotubes with a diameter of 10-15 nm and a length of 40-50 μm; the graphene oxide is multilayer graphene oxide with an average thickness of 1-3 nm and a diameter of 4-7 μm; the graphene is single-layer graphene with a thickness of 0.34 nm and a sheet diameter of 1 μm; the pH value of the aqueous hydroxyl acrylic dispersion is 7-8, the ester content is 11-15 mg KOH / g, and the hydroxyl content is 3.9 wt%; the wetting and dispersing agent is BYK-190 wetting and dispersing agent; the leveling agent is BYKETOL-WS leveling agent; the defoamer is BYK-011 defoamer; the isocyanate group (-NCO) content in the aqueous isocyanate curing agent is 18.0 ± 0.5%; and the polyethylene glycol is polyethylene glycol-2000.
[0034] Test case The aqueous graphene electrothermal coatings prepared in Examples 4-6 and Comparative Examples 2-3 were respectively coated onto heat-resistant single-sided cardboard, with a coating size of 250mm × 80mm and a coating thickness of 0.12mm. The coatings were cured at 80℃ for 5 hours to form an electrothermal coating. The performance of the electrothermal coatings was then tested. (1) Electrothermal performance: Under the test conditions of 19±2℃, 220V, and 10min, the heating power and heating temperature of the electrothermal coating were measured. The test results are shown in Table 1. Table 1
[0035] As shown in Table 1, the waterborne graphene electrothermal coating prepared by this invention exhibits excellent electrothermal performance. The amino-modified reduced graphene oxide surface contains a large number of amino functional groups (primary and secondary amines), which can chemically react with the waterborne isocyanate curing agent in component B to form strong covalent bonds. This effectively prevents interfacial peeling and migration of graphene due to weak physical adsorption during use, ensuring the long-term stability of the conductive pathway. The epoxy-modified carbon nanotubes in the composite additive synergistically construct a point-to-surface three-dimensional conductive network with graphene in the coating. The carbon nanotubes act as bridges, connecting the dispersed graphene sheets, significantly reducing the percolation threshold of the coating and improving conductivity. The electrothermal coating formed by curing the electrothermal coating exhibits good electrothermal performance. Furthermore, the composite additive can bond the secondary amino groups introduced by the bridging agent triethylenetetramine with the waterborne isocyanate curing agent in component B, thereby further improving the electrothermal performance of the coating. Compared to Example 4, in Comparative Example 2, although amino-modified reduced graphene oxide was used, the bridging agent was replaced by 3-aminopropyltriethoxysilane instead of triethylenetetramine when preparing the composite additive. This resulted in the lack of groups that could bond with the waterborne isocyanate curing agent, leading to a decrease in the uniformity of the composite additive's dispersion in the polyurethane resin matrix and a reduction in its electrothermal performance. Compared to Comparative Example 2, in Comparative Example 3, unmodified graphene was used, which was prone to agglomeration and difficult to form a continuous and stable conductive network, resulting in a further decrease in electrothermal performance.
[0036] (2) Weather resistance: The initial surface temperature of the coating was stabilized at (80±5)℃ by adjusting the voltage to simulate the high temperature of actual working conditions. Under this condition, the coating was continuously powered on for 1000h for aging. During the test, air circulation was maintained to provide sufficient oxygen. The sheet resistance was measured at 5 different locations on the coating surface using a four-probe tester. The average value was taken, and the sheet resistance change rate ΔR was calculated. s ΔR s The smaller the value, the more stable the conductive network of the coating is in a thermal oxidation environment, and the better its weather resistance. ΔR s The calculation formula is as follows: ΔR s =(R s(t) -R s(0) ) / R s(0) ×100%; In the formula: R s(0) Let R be the initial sheet resistance. s(t) The sheet resistor after aging; Sheet resistance change rate ΔR s The measurement results are shown in Table 2: Table 2
[0037] As shown in Table 2, the waterborne graphene electrothermal coating prepared by this invention exhibits excellent weather resistance. The introduction of hindered phenolic antioxidant molecules in the composite additive can capture and eliminate free radicals generated in the resin matrix due to heat and electric field effects, effectively inhibiting the thermal oxidative degradation of polymer chains. This protects the interface between the conductive filler graphene and carbon nanotubes and the matrix, as well as the overall three-dimensional conductive network structure, resulting in good weather resistance. Furthermore, the composite additive can bond with the waterborne isocyanate curing agent in component B through the secondary amino groups introduced by the bridging agent triethylenetetramine, thereby further improving the weather resistance of the coating. Compared to Example 4, in Comparative Example 2, the bridging agent was replaced by 3-aminopropyltriethoxysilane instead of triethylenetetramine during the preparation of the composite additive. This lack of a group capable of bonding with the waterborne isocyanate curing agent resulted in decreased dispersion uniformity of the composite additive in the polyurethane resin matrix, leading to insufficient protection of the matrix and a significant increase in the sheet resistance rate. In Comparative Example 3, unmodified graphene was used, which only physically adsorbs onto the resin matrix, resulting in weak interfacial bonding and a tendency to agglomerate. During thermo-oxidative aging, the conductive network is more easily damaged, leading to a significantly increased sheet resistance rate and the worst weather resistance.
[0038] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.
Claims
1. A water-based graphene electrothermal coating, characterized in that, Includes components A, B, and C; Component A, by weight, comprises the following raw materials: 30-40 parts of aqueous hydroxy acrylic acid dispersion; 6-10 parts deionized water; 3-5 parts wetting and dispersing agent; Leveling agent 0.5-1 part; 0.5-1 part defoamer; Component B, by weight, comprises the following raw materials: 40-60 parts of water-based isocyanate curing agent; 30-50 parts of co-solvent; Component C, by weight, comprises the following raw materials: 30-50 parts of amino-modified reduced graphene oxide; 30-50 parts of compound additives; Dispersant 0.5-1 part; 80-120 parts deionized water; The composite additive is prepared by the following steps: 3,5-Bis(tert-butyl)-4-hydroxyphenylpropionyl chloride was reacted with triethylenetetramine to prepare an amino-modified hindered phenolic antioxidant; the amino-modified hindered phenolic antioxidant was reacted with epoxy-modified carbon nanotubes to obtain a composite additive.
2. The water-based graphene electrothermal coating according to claim 1, characterized in that, The preparation method of the composite additive specifically includes: S11. Dissolve 3,5-bis(tert-butyl)-4-hydroxyphenylpropionyl chloride in benzene to obtain a 3,5-bis(tert-butyl)-4-hydroxyphenylpropionyl chloride solution; dissolve triethylenetetramine in deionized water to obtain a triethylenetetramine solution; add the triethylenetetramine solution dropwise to the 3,5-bis(tert-butyl)-4-hydroxyphenylpropionyl chloride solution. After the addition is complete, add alkali solution to adjust the pH value to 9-10. Allow the reaction to proceed. After the reaction is complete, separate and purify the solution to obtain an amino-modified hindered phenolic antioxidant. S12. Dissolve the amino-modified hindered phenolic antioxidant in benzene, add epoxy-modified carbon nanotubes, and react. After the reaction is complete, filter, wash, and dry to obtain the composite additive.
3. The water-based graphene electrothermal coating according to claim 2, characterized in that, In S11, the molar ratio of 3,5-bis(tert-butyl)-4-hydroxyphenylpropionyl chloride to triethylenetetramine is 1:(1.05-1.1); in the 3,5-bis(tert-butyl)-4-hydroxyphenylpropionyl chloride solution, the mass-to-volume ratio of 3,5-bis(tert-butyl)-4-hydroxyphenylpropionyl chloride to benzene is 1 g / (8-12) mL; in the triethylenetetramine solution, the mass-to-volume ratio of triethylenetetramine to deionized water is 1 g / (20-30) mL, and the reaction conditions are 20-30 h at room temperature.
4. The water-based graphene electrothermal coating according to claim 2, characterized in that, In S12, the mass ratio of amino-modified hindered phenolic antioxidant, benzene, and epoxy-modified carbon nanotubes is 40.7:(200-300):(10-20), and the reaction conditions are under a nitrogen atmosphere and at a temperature of 50-60℃ for 10-15 hours.
5. The water-based graphene electrothermal coating according to claim 2, characterized in that, The epoxy-modified carbon nanotubes are prepared by the following steps: Carbon nanotubes were added to a mixed acid prepared from concentrated sulfuric acid and concentrated nitric acid, dispersed by ultrasonication, and reacted. After the reaction was completed, the mixture was filtered, washed, and dried to obtain acidified carbon nanotubes. γ-(2,3-epoxypropoxy)propyltrimethoxysilane was added to ethanol, the pH was adjusted to 4.5-5.5, acidified carbon nanotubes were added, and the mixture was ultrasonically dispersed and reacted. After the reaction was completed, the mixture was filtered, washed, and dried to obtain epoxy-modified carbon nanotubes.
6. The water-based graphene electrothermal coating according to claim 5, characterized in that, When preparing the acidified carbon nanotubes, the mass ratio of carbon nanotubes to mixed acid is 1:(10-20), and the reaction conditions are stirring at 40-50℃ for 10-15 h; when preparing the epoxy-modified carbon nanotubes, the mass ratio of γ-(2,3-epoxypropoxy)propyltrimethoxysilane, ethanol, and acidified carbon nanotubes is (2-3):(100-200):1, and the reaction conditions are stirring at 50-70℃ for 4-8 h.
7. The water-based graphene electrothermal coating according to claim 1, characterized in that, The amino-modified reduced graphene oxide in component C is prepared by the following steps: S21. Add graphene oxide to an ethanol aqueous solution, disperse it by ultrasonication, add triethylamine and N-aminoethyl-3-aminopropylmethyldimethoxysilane, react, filter and wash after the reaction is completed to obtain amino-modified graphene oxide. S22. Add amino-modified graphene oxide to deionized water, disperse it by ultrasonication, add ammonia and alkaline solution, and react. After the reaction is completed, filter, wash, and dry to obtain amino-modified reduced graphene oxide.
8. The water-based graphene electrothermal coating according to claim 7, characterized in that, In S21, the mass ratio of graphene oxide, aqueous ethanol solution, triethylamine, and N-aminoethyl-3-aminopropylmethyldimethoxysilane is 1:(20-30):(0.8-1.2):(6-10), and the reaction is carried out under the condition of stirring at room temperature for 20-30 hours.
9. The water-based graphene electrothermal coating according to claim 7, characterized in that, In S22, the mass ratio of amino-modified graphene oxide, deionized water, ammonia, and alkaline solution is 1:(400-600):(100-200):(20-30), and the reaction conditions are reflux reaction at 75-85℃ for 20-30h under a nitrogen atmosphere.
10. The water-based graphene electrothermal coating according to claim 1, characterized in that, The mass ratio of component A, component B and component C is 100:25:(15-20).