Graphene-containing copper composite filler-containing electromagnetic shielding waterborne epoxy coating and preparation method

Abstract

The application provides an electromagnetic shielding waterborne epoxy coating containing graphene copper composite fillers and a preparation method, and belongs to the technical field of coatings. Three kinds of additives are introduced to solve the problems of poor interface combination of graphene and copper particles with an epoxy matrix, easy oxidation of copper particles and uneven distribution of conductive paths: a bridging agent realizes multi-point anchoring and interface combination of fillers through dynamic bond action, and forms a stable conductive network after curing; a biomimetic mixed protective film forms a dense barrier through the cooperation of zirconium oxychloride and methyl triethoxysilane, and combines the intelligent release function of 2-mercaptoimidazole to effectively improve the oxidation resistance of copper particles; a conductive path regulator pre-constructs a conductive network through ionic bond bridging to promote the formation of a high-efficiency and through conductive layered structure; the three cooperate to build an efficient, stable and durable conductive network, and improve the electromagnetic shielding performance of the waterborne epoxy coating.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of coatings, and relates to an electromagnetic shielding waterborne epoxy coating containing graphene copper composite fillers and a preparation method. BACKGROUND

[0002] Electromagnetic shielding coatings are widely used in electronic devices, communication technology and military fields to protect sensitive electronic components from the influence of electromagnetic interference. Due to the increasing sensitivity to electromagnetic interference, especially in high-frequency and high-density integrated circuits, traditional shielding materials gradually expose their inherent shortcomings, such as excessive weight, complex installation and limited shielding performance. In recent years, graphene, as a new type of nanomaterial, has attracted widespread attention due to its excellent electrical conductivity, strength and thermal stability. The combination of graphene and metal materials can significantly improve the electrical conductivity and electromagnetic shielding ability of the coating. However, this composite material still faces a series of technical challenges in practical application.

[0003] Firstly, the interface interaction between graphene and copper is usually weak, resulting in poor dispersibility and stability of graphene in the waterborne epoxy system. The chemical difference between graphene and the surface of copper easily leads to agglomeration and interface debonding, hindering the formation of a continuous conductive network. This limits the formation of an effective conductive path in the coating by graphene / copper composite fillers, thereby affecting the electromagnetic shielding performance; secondly, in the aqueous environment, copper powder is easily oxidized, leading to a significant decrease in its electrical conductivity. The oxide layer formed on the surface of the oxidized copper not only reduces its electrical conductivity, but also may cause interface defects, thereby causing the attenuation of shielding efficiency; in addition, during the film-forming process of the coating film, the conductive fillers may exhibit delamination or misplacement phenomena, even in the case of good initial dispersion, microphase separation may occur during curing or use, leading to the "cutting" or "weakening" of the conductive path. This uneven distribution directly affects the overall performance of the electromagnetic shielding coating. SUMMARY

[0004] In order to solve the problems of poor interface combination of graphene and copper particles with the epoxy matrix, easy oxidation of copper particles and uneven distribution of conductive paths, the application introduces an ion-dynamic bonding type micro-interface bridging agent, a biomimetic organic-inorganic hybrid protective film and a conductive path regulating agent. The bridging agent realizes multi-point anchoring and interface combination of fillers through dynamic bond, and forms a stable conductive network after curing; the biomimetic hybrid protective film forms a dense barrier by the synergistic effect of zirconium oxychloride and methyl triethoxysilane, and effectively improves the oxidation resistance of copper particles by combining the intelligent release function of 2-mercaptoimidazole; the conductive path regulating agent realizes efficient dispersion and stability of conductive fillers through its amphiphilic structure, and uses the introduced metal ions as dynamic crosslinking centers to pre-bridge the dispersed fillers into a network at the molecular level, finally promoting the formation of a high-efficiency conductive layered structure in the film forming process; the three synergistically build an efficient, stable and durable conductive network, and improve the electromagnetic shielding performance of the waterborne epoxy coating.

[0005] In order to achieve the above purpose, the application adopts the following technical solutions:

[0006] In the first aspect, the application provides a preparation method of an electromagnetic shielding waterborne epoxy coating containing graphene copper composite fillers, which comprises the following steps:

[0007] S1: dispersing polyvinylpyrrolidone in deionized water to obtain a polyvinylpyrrolidone solution, adding methacrylic acid, dimethylaminoethyl methacrylate and ammonium persulfate to obtain a reaction liquid E, and reacting to obtain a partially grafted amphiphilic block copolymer solution, adding a ferrous chloride solution to obtain a reaction liquid F, stirring and reacting, and distilling under reduced pressure to obtain a conductive path regulating agent;

[0008] S2: mixing graphene with deionized water, adding an ion-dynamic bonding type micro-interface bridging agent, and ultrasonically treating to obtain a graphene slurry; adding antioxidant / anti-corrosion composite protective copper powder, stirring and defoaming to obtain a graphene-copper composite slurry;

[0009] S3: premixing an epoxy resin emulsion with a curing agent, adding a leveling agent and a defoaming agent, and stirring uniformly to obtain a first mixed coating; adding the graphene-copper composite slurry and stirring to disperse uniformly to obtain a second mixed coating, adding the conductive path regulating agent, and mixing uniformly to obtain the electromagnetic shielding waterborne epoxy coating containing graphene copper composite fillers.

[0010] The preparation steps of the ion-dynamic bonding type micro-interface bridging agent are as follows:

[0011] N-vinylimidazole, acrylic acid, and glycidyl methacrylate are dispersed in a deionized water / ethanol mixed solution to obtain a mixed monomer dispersion solution, ammonium persulfate and tetramethyl ethylenediamine are added to obtain a reaction liquid A, after adjusting pH, stirring reaction to obtain a reaction liquid B, after adding potassium dihydrogen phosphate solution, adding triethanolamine to obtain a reaction liquid C, stirring reaction, filtering, and vacuum distillation to obtain an ion-dynamic bonding type micro-interface bridging agent;

[0012] The preparation steps of the anti-oxidation / corrosion composite protective copper powder are as follows:

[0013] A zirconium oxychloride solution and an ethanol solution of methyl triethoxysilane are prepared, the zirconium oxychloride solution and the ethanol solution of methyl triethoxysilane are mixed, ammonia water is added dropwise while stirring to adjust pH to obtain an organic-inorganic precursor solution; copper powder is added to the organic-inorganic precursor solution to obtain a reaction liquid D, stirring reaction, adding 2-mercaptoimidazole and continuing to stir to obtain a pretreatment liquid, rotary evaporation, and drying to obtain the anti-oxidation / corrosion composite protective copper powder;

[0014] As a preferred technical solution of the present application, in step S1, the mass / volume ratio of polyvinylpyrrolidone to deionized water is (10-15):(90-100) g / mL;

[0015] The mass ratio of polyvinylpyrrolidone to methacrylic acid, dimethylaminoethyl methacrylate, and ammonium persulfate is (10-15):(5-10):(1-3):(0.1-0.3).

[0016] In some optional embodiments, the temperature of the reaction of the reaction liquid E is 70-80℃, for example, it can be 70℃, 71℃, 72℃, 73℃, 74℃, 75℃, 76℃, 77℃, 78℃, 79℃, or 80℃, but is not limited to the listed values, and other values not listed in this range are also applicable.

[0017] In some optional embodiments, the reaction time of the reaction liquid E is 2-4h, for example, it can be 2h, 2.2h, 2.4h, 2.6h, 2.8h, 3h, 3.2h, 3.4h, 3.6h, 3.8h, or 4h, but is not limited to the listed values, and other values not listed in this range are also applicable.

[0018] In some optional embodiments, the mass fraction of the ferrous chloride solution is 1-2wt.%, for example, it can be 1wt.%, 1.1wt.%, 1.2wt.%, 1.3wt.%, 1.4wt.%, 1.5wt.%, 1.6wt.%, 1.7wt.%, 1.8wt.%, 1.9wt.%, or 2wt.%, but is not limited to the listed values, and other values not listed in this range are also applicable.

[0019] In some optional embodiments, the amount of ferrous chloride is 0.5-1% of the mass of the partially grafted amphiphilic block copolymer solution, for example, it can be 0.5%, 0.55%, 0.6%, 0.65%, 0.7%, 0.75%, 0.8%, 0.85%, 0.9%, 0.95% or 1%, but not limited to the listed values, and other values not listed in the range are also applicable.

[0020] In some optional embodiments, the temperature for stirring the reaction solution F is 30-40℃, for example, it can be 30℃, 31℃, 32℃, 33℃, 34℃, 35℃, 36℃, 37℃, 38℃, 39℃ or 40℃, but not limited to the listed values, and other values not listed in the range are also applicable.

[0021] In some optional embodiments, the stirring time of the reaction solution F is 1-2h, for example, it can be 1h, 1.1h, 1.2h, 1.3h, 1.4h, 1.5h, 1.6h, 1.7h, 1.8h, 1.9h or 2h, but not limited to the listed values, and other values not listed in the range are also applicable.

[0022] In some optional embodiments, the solid content of the conductive path regulating agent is 10-15%, for example, it can be 10%, 10.5%, 11%, 11.5%, 12%, 12.5%, 13%, 13.5%, 14%, 14.5% or 15%, but not limited to the listed values, and other values not listed in the range are also applicable.

[0023] As a preferred technical solution of the present application, in step S2, the mass ratio of graphene to deionized water is 1:20-30, for example, it can be 1:20, 1:21, 1:22, 1:23, 1:24, 1:25, 1:26, 1:27, 1:28, 1:29 or 1:30, but not limited to the listed values, and other values not listed in the range are also applicable.

[0024] In some optional embodiments, the amount of ion-dynamic bonding type micro-interface bridging agent is 2-5% of the mass of graphene, for example, it can be 2%, 2.3%, 2.6%, 2.9%, 3.2%, 3.5%, 3.8%, 4.1%, 4.4%, 4.7% or 5%, but not limited to the listed values, and other values not listed in the range are also applicable.

[0025] In some optional embodiments, the power of the ultrasonic treatment is 300-500 W, for example, can be 300 W, 320 W, 340 W, 360 W, 380 W, 400 W, 420 W, 440 W, 460 W, 480 W or 500 W, but not limited to the listed values, and other values not listed in this range are also applicable.

[0026] In some optional embodiments, the time of the ultrasonic treatment is 15-30 min, for example, can be 15 min, 16 min, 17 min, 18 min, 19 min, 20 min, 21 min, 22 min, 23 min, 24 min, 25 min, 26 min, 27 min, 28 min, 29 min or 30 min, but not limited to the listed values, and other values not listed in this range are also applicable.

[0027] In some optional embodiments, the mass ratio of graphene to anti-oxidation / anti-corrosion composite protective copper powder is 1:3-5, for example, can be 1:3, 1:3.2, 1:3.4, 1:3.6, 1:3.8, 1:4.0, 1:4.2, 1:4.4, 1:4.6, 1:4.8 or 1:5, but not limited to the listed values, and other values not listed in this range are also applicable.

[0028] As a preferred technical solution of the present application, in step S3, the curing agent is Anquamine 287 or Anquamine 401.

[0029] In some optional embodiments, the mass ratio of the epoxy resin emulsion to the curing agent is 100:40-60, for example, can be 100:40, 100:42, 100:44, 100:46, 100:48, 100:50, 100:52, 100:54, 100:56, 100:58 or 100:60, but not limited to the listed values, and other values not listed in this range are also applicable.

[0030] In some optional embodiments, the addition amount of the leveling agent BYK-348 is 0.1-0.3% of the mass of the epoxy resin emulsion, for example, can be 0.1%, 0.12%, 0.14%, 0.16%, 0.18%, 0.20%, 0.22%, 0.24%, 0.26%, 0.28% or 0.3%, but not limited to the listed values, and other values not listed in this range are also applicable.

[0031] In some optional embodiments, the antifoaming agent BYK-024 is added in an amount of 0.1-0.3% by mass of the epoxy resin emulsion, for example, can be 0.1%, 0.12%, 0.14%, 0.16%, 0.18%, 0.20%, 0.22%, 0.24%, 0.26%, 0.28% or 0.3%, but not limited to the listed values, other values not listed in the range are also applicable.

[0032] In some optional embodiments, the graphene-copper composite slurry is added in an amount of 20-30% by mass of the first mixed coating, for example, can be 20%, 21%, 22%, 23%, 24%, 25%, 26%, 27%, 28%, 29% or 30%, but not limited to the listed values, other values not listed in the range are also applicable.

[0033] In some optional embodiments, the conductive path regulating agent is added in an amount of 1-3% by mass of the first mixed coating, for example, can be 1%, 1.2%, 1.4%, 1.6%, 1.8%, 2%, 2.2%, 2.4%, 2.6%, 2.8% or 3%, but not limited to the listed values, other values not listed in the range are also applicable.

[0034] As a preferred technical solution of the present application, in the preparation step of the ion-dynamic bonding type micro-interface bridging agent, the volume ratio of deionized water to ethanol is 1:1-2, for example, can be 1:1, 1:1.1, 1:1.2, 1:1.3, 1:1.4, 1:1.5, 1:1.6, 1:1.7, 1:1.8, 1:1.9 or 1:2, but not limited to the listed values, other values not listed in the range are also applicable.

[0035] In some optional embodiments, the total mass fraction of the mixed monomer dispersion is 10-20wt.%, for example, can be 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19% or 20%, but not limited to the listed values, other values not listed in the range are also applicable.

[0036] In some optional embodiments, the mass ratio of N-vinylimidazole to acrylic acid is 1:(0.3-0.5), for example, can be 1:0.3, 1:0.32, 1:0.34, 1:0.36, 1:0.38, 1:0.4, 1:0.42, 1:0.44, 1:0.46, 1:0.48 or 1:0.5, but not limited to the listed values, other values not listed in the range are also applicable.

[0037] In some alternative embodiments, the mass ratio of the N-vinylimidazole to glycidyl methacrylate is 1 : (0.2-0.4), for example, it can be 1 :0.2, 1 :0.22, 1 :0.24, 1 :0.26, 1 :0.28, 1 :0.3, 1 :0.32, 1 :0.34, 1 :0.36, 1 :0.38, or 1 :0.4, but is not limited to the listed values, and other values not listed in the range are also applicable.

[0038] In some alternative embodiments, the total mole ratio of the ammonium persulfate to the mixed monomers is 0.01-0.02:1, for example, it can be 0.01:1, 0.011:1, 0.012:1, 0.013:1, 0.014:1, 0.015:1, 0.016:1, 0.017:1, 0.018:1, 0.019:1, or 0.02:1, but is not limited to the listed values, and other values not listed in the range are also applicable.

[0039] In some alternative embodiments, the mole ratio of the tetramethylethylenediamine to the ammonium persulfate is 1-2:1, for example, it can be 1:1, 1.1:1, 1.2:1, 1.3:1, 1.4:1, 1.5:1, 1.6:1, 1.7:1, 1.8:1, 1.9:1, or 2:1, but is not limited to the listed values, and other values not listed in the range are also applicable.

[0040] In some alternative embodiments, the pH of the reaction solution A is adjusted to 5-7, for example, it can be 5, 5.2, 5.4, 5.6, 5.8, 6, 6.2, 6.4, 6.6, or 7, but is not limited to the listed values, and other values not listed in the range are also applicable.

[0041] In some alternative embodiments, the temperature of the reaction solution A after adjusting the pH is stirred at 60-70°C, for example, it can be 60°C, 61°C, 62°C, 63°C, 64°C, 65°C, 66°C, 67°C, 68°C, 69°C, or 70°C, but is not limited to the listed values, and other values not listed in the range are also applicable.

[0042] In some alternative embodiments, the time of the reaction solution A after adjusting the pH is stirred for 3-5h, for example, it can be 3h, 3.2h, 3.4h, 3.6h, 3.8h, 4h, 4.2h, 4.4h, 4.6h, 4.8h, or 5h, but is not limited to the listed values, and other values not listed in the range are also applicable.

[0043] In some optional embodiments, the mass fraction of the potassium dihydrogen phosphate solution is 5-8 wt.%, for example, it can be 5 wt.%, 5.3 wt.%, 5.6 wt.%, 5.9 wt.%, 6.2 wt.%, 6.5 wt.%, 6.8 wt.%, 7.1 wt.%, 7.4 wt.%, 7.7 wt.%, or 8 wt.%, but is not limited to the listed values, and other values not listed in the range are also applicable.

[0044] In some optional embodiments, the total molar ratio of the potassium dihydrogen phosphate to the mixed monomers is 0.05-0.15:1, for example, it can be 0.05:1, 0.06:1, 0.07:1, 0.08:1, 0.09:1, 0.10:1, 0.11:1, 0.12:1, 0.13:1, 0.14:1, or 0.15:1, but is not limited to the listed values, and other values not listed in the range are also applicable.

[0045] In some optional embodiments, after the potassium dihydrogen phosphate solution is added to the reaction solution B, triethanolamine is added to the solution to a pH of 6-8, for example, it can be 6, 6.2, 6.4, 6.6, 6.8, 7, 7.2, 7.4, 7.6, 7.8, or 8, but is not limited to the listed values, and other values not listed in the range are also applicable.

[0046] In some optional embodiments, the temperature of the stirring reaction of the reaction solution C is 50-55°C, for example, it can be 50°C, 50.5°C, 51°C, 51.5°C, 52°C, 52.5°C, 53°C, 53.5°C, 54°C, 54.5°C, or 55°C, but is not limited to the listed values, and other values not listed in the range are also applicable.

[0047] In some optional embodiments, the stirring reaction time of the reaction solution C is 2-3h, for example, it can be 2h, 2.1h, 2.2h, 2.3h, 2.4h, 2.5h, 2.6h, 2.7h, 2.8h, 2.9h, or 3h, but is not limited to the listed values, and other values not listed in the range are also applicable.

[0048] In some optional embodiments, the solid content of the ion-dynamic bonding type micro-interface bridging agent is 20-30%, for example, it can be 20%, 21%, 22%, 23%, 24%, 25%, 26%, 27%, 28%, 29%, or 30%, but is not limited to the listed values, and other values not listed in the range are also applicable.

[0049] As a preferred technical solution of the present application, in the preparation step of the anti-oxidation / anti-corrosion composite protective copper powder, the mass fraction of the zirconium oxychloride solution is 1-5 wt.%, for example, it can be 1 wt.%, 1.4 wt.%, 1.8 wt.%, 2.2 wt.%, 2.6 wt.%, 3 wt.%, 3.4 wt.%, 3.8 wt.%, 4.2 wt.%, 4.6 wt.%, or 5 wt.%, but is not limited to the listed values, and other values not listed in this range are also applicable.

[0050] In some optional embodiments, the mass fraction of the methyl triethoxysilane ethanol solution is 5-10 wt.%, for example, it can be 5 wt.%, 5.5 wt.%, 6 wt.%, 6.5 wt.%, 7 wt.%, 7.5 wt.%, 8 wt.%, 8.5 wt.%, 9 wt.%, 9.5 wt.%, or 10 wt.%, but is not limited to the listed values, and other values not listed in this range are also applicable.

[0051] In some optional embodiments, the zirconium oxychloride solution and the methyl triethoxysilane ethanol solution are mixed in a volume ratio of 1:1-2, for example, it can be 1:1, 1:1.1, 1:1.2, 1:1.3, 1:1.4, 1:1.5, 1:1.6, 1:1.7, 1:1.8, 1:1.9, or 1:2, but is not limited to the listed values, and other values not listed in this range are also applicable.

[0052] In some optional embodiments, the mass fraction of the ammonia water is 10-15 wt.%, for example, it can be 10 wt.%, 10.5 wt.%, 11 wt.%, 11.5 wt.%, 12 wt.%, 12.5 wt.%, 13 wt.%, 13.5 wt.%, 14 wt.%, 14.5 wt.%, or 15 wt.%, but is not limited to the listed values, and other values not listed in this range are also applicable.

[0053] In some optional embodiments, the ammonia water is added dropwise to adjust the pH to 3-4, for example, it can be 3, 3.1, 3.2, 3.3, 3.4, 3.5, 3.6, 3.7, 3.8, 3.9, or 4, but is not limited to the listed values, and other values not listed in this range are also applicable.

[0054] In some alternative embodiments, the solid-liquid mass ratio of the copper powder and the organic-inorganic precursor solution is 1:5-8, for example, it can be 1:5, 1:5.3, 1:5.6, 1:5.9, 1:6.2, 1:6.5, 1:6.8, 1:7.1, 1:7.4, 1:7.7 or 1:8, but not limited to the listed values, other values not listed in the range are also applicable.

[0055] In some alternative embodiments, the temperature of the reaction liquid D stirring reaction is 30-40℃, for example, it can be 30℃, 31℃, 32℃, 33℃, 34℃, 35℃, 36℃, 37℃, 38℃, 39℃ or 40℃, but not limited to the listed values, other values not listed in the range are also applicable.

[0056] In some alternative embodiments, the time of the reaction liquid D stirring reaction is 1-1.5h, for example, it can be 1h, 1.05h, 1.1h, 1.15h, 1.2h, 1.25h, 1.3h, 1.35h, 1.4h, 1.45h or 1.5h, but not limited to the listed values, other values not listed in the range are also applicable.

[0057] In some alternative embodiments, the feeding amount of the 2-mercaptoimidazole is 0.1-0.5% of the mass of the copper powder, for example, it can be 0.1%, 0.14%, 0.18%, 0.22%, 0.26%, 0.30%, 0.34%, 0.38%, 0.42%, 0.46% or 0.5%, but not limited to the listed values, other values not listed in the range are also applicable.

[0058] In some alternative embodiments, after the reaction liquid D stirring reaction, 2-mercaptoimidazole is added and continues to stir for 30-40min, for example, it can be 30min, 31min, 32min, 33min, 34min, 35min, 36min, 37min, 38min, 39min or 40min, but not limited to the listed values, other values not listed in the range are also applicable.

[0059] In a second aspect, the present application provides an electromagnetic shielding waterborne epoxy coating containing graphene copper composite filler, which is prepared according to the above preparation method.

[0060] In the electromagnetic shielding waterborne epoxy coating, due to the difference in surface chemical properties, graphene and copper are prone to interface agglomeration or debonding, and it is difficult to form a stable and through conductive network; at the same time, the interface contact between graphene, copper particles and epoxy matrix is not tight, and the traditional dispersant is invalid after the coating is cured, and cannot maintain the integrity and stability of the conductive network. In addition, copper particles are easily oxidized in the waterborne system, which leads to a significant decrease in conductive performance and shielding effectiveness. In the waterborne coating system, due to the limitation of surface tension and solid content, the conductive filler is also prone to delamination or random distribution, which further weakens the continuity of the conductive path and the shielding performance. In view of these problems, three kinds of synergistic functional additives are designed, including ion-dynamic bonding type micro-interface bridging agent, antioxidant / anti-corrosion composite protective copper powder and conductive path regulator, to realize the efficient and stable construction of the conductive network.

[0061] The introduction of ion-dynamic bonding type micro-interface bridging agent is to improve the interface bonding between graphene and copper particles and epoxy matrix, and to ensure the uniformity and stability of the conductive network by dynamically adjusting the distribution of fillers. The core components of the bridging agent include N-vinylimidazole, acrylic acid and glycidyl methacrylate. The imidazole group in N-vinylimidazole contains a cationic site, which can combine the π-electron cloud of graphene through π-π interaction, and at the same time combine with the active sites on the surface of copper through coordination action, so as to realize multi-point anchoring. The carboxylic acid group provided by acrylic acid can be combined with the hydroxyl or amine group in the epoxy matrix through hydrogen bond, and the interface bonding strength between the bridging agent and the filler is enhanced through electrostatic action. The terminal of glycidyl methacrylate contains an epoxy group, which can chemically cross-link with the epoxy matrix during the curing process of the epoxy coating, so as to realize the permanent fixation of the bridging agent to the matrix. During the flow and curing stage of the coating formation, the bridging agent adjusts the distribution of graphene and copper particles by dynamic bond action such as hydrogen bond and ionic bond with the change of local stress, so as to ensure the uniformity of the conductive network. After curing, the dynamic bond part is converted into covalent bond or more firm hydrogen bond, so as to improve the long-term stability of the conductive network.

[0062] In order to solve the problem that copper particles are easy to be oxidized or corroded in aqueous system, the application realizes long-acting anti-oxidation and anti-corrosion by introducing a biomimetic organic-inorganic hybrid protective film and an intelligent release antioxidant ligand on the surface of copper particles, while retaining the conductive properties of copper particles. The formation of the organic-inorganic hybrid protective film depends on the synergistic effect of zirconium oxychloride and methyl triethoxysilane. Zirconium oxychloride generates zirconium hydroxyl groups during hydrolysis, and forms a three-dimensionally cross-linked inorganic skeleton film layer through condensation reaction, effectively isolating oxygen and moisture. The siloxane groups of methyl triethoxysilane hydrolyze and condense under pH 3-4 conditions, and cooperate with zirconium oxychloride to form an organic-inorganic hybrid film, and the introduction of methyl groups further enhances the hydrophobicity of the film layer, thereby enhancing the anti-oxidation performance. In addition, 2-mercaptoimidazole as an intelligent release antioxidant ligand, the mercapto group in the molecule is combined with the copper surface through Cu-S bond, and the imidazole group is further stabilized by coordination. This dual effect effectively prevents the oxidation of copper. When there is a change in pH or corrosive ions in the environment, the mercaptoimidazole can be triggered to release, filling the local damaged area and delaying the expansion of corrosion.

[0063] The biomimetic film provides a dense barrier as a primary protective layer, isolating oxygen and moisture; the antioxidant ligand provides a dynamic repair function as a secondary protective layer, significantly improving the anti-oxidation performance of the copper particles, while retaining their conductive properties.

[0064] In order to solve the problem that the conductive filler in the water-based paint is easy to agglomerate due to high surface energy, and the interface compatibility with the epoxy resin matrix is poor, thereby leading to discontinuous conductive path and low electromagnetic shielding efficiency, the application prepares a conductive path regulator. The bridge linking agent as an amphiphilic block copolymer, its polyvinylpyrrolidone hydrophilic segment provides strong steric hindrance stabilization in the aqueous system, so that graphene and copper powder can achieve uniform and efficient dispersion at the initial mixing stage, and irreversible agglomeration is inhibited. At the same time, its methacrylic acid and methacrylic acid dimethylaminoethyl ester functional segment is anchored on the surface of the conductive filler through various interaction forces such as hydrogen bond, acid-base interaction and coordination bond. The introduced ferrous ion acts as an ionic bonded crosslinking center, which can complex with the carboxyl groups in the polymer chains adsorbed on different filler particles, forming a flexible bridging structure. This ionic bond bridging effect pre-connects isolated conductive units into a dynamic and primary conductive network at the molecular level. Finally, during the coating construction and curing process, with the evaporation of water and the volume shrinkage of the coating film, these two-dimensional sheet filler networks pre-connected by the bridging agent are more easily oriented in parallel to the substrate surface under the combined action of shear force and laminar flow effect than the disordered individual particles. This synergistic effect based on molecular self-assembly promotes the spontaneous formation of a high-penetration and structurally stable layered conductive network, thereby improving the overall electromagnetic shielding performance of the coating.

[0065] In the present application, the interface bonding between graphene and copper particles and the epoxy matrix is improved by ion-dynamic bonding type bridging agent, the antioxidant performance of copper particles is protected by biomimetic organic-inorganic hybrid protective film and intelligent release antioxidant ligand, and a high-efficiency, stable and durable conductive network is constructed by guiding the directional arrangement of conductive fillers through the conductive path regulator, thereby improving the electromagnetic shielding performance of the waterborne epoxy coating.

[0066] Compared with the prior art, the present application has the following beneficial effects:

[0067] The introduction of the ion-dynamic bonding type micro-interface bridging agent improves the interface bonding between graphene, copper particles and the epoxy matrix. The imidazole group in N-vinylimidazole realizes multi-point anchoring through π-π interaction and coordination complexation, the carboxylic acid group provided by acrylic acid enhances the interface bonding through hydrogen bonding and electrostatic interaction, and the epoxy group of glycidyl methacrylate realizes permanent fixation by crosslinking with the matrix during the curing process. During the coating film forming stage, the bridging agent adjusts the filler distribution by dynamic bonds to ensure the uniformity of the conductive network; after curing, these dynamic bonds are partially converted into more stable covalent bonds or firm hydrogen bonds, thereby further improving the long-term stability of the conductive network.

[0068] By introducing a biomimetic organic-inorganic hybrid protective film and an intelligent release antioxidant ligand on the surface of copper particles, the problem of easy oxidation or corrosion of copper in the waterborne system is solved, while its conductive performance is retained. The organic-inorganic hybrid film is formed by zirconium oxychloride and methyl triethoxysilane, and its dense structure isolates oxygen and moisture, thereby enhancing the antioxidant performance; 2-mercaptoimidazole as an antioxidant ligand is combined with copper through Cu-S bond and dynamically releases to repair local damage in a corrosive environment. The double-layer protection system significantly improves the antioxidant ability and long-term stability of the copper particles.

[0069] The conductive path regulator introduced in the present application is an amphiphilic copolymer, which utilizes the steric hindrance effect of the hydrophilic segment to realize efficient and uniform dispersion of conductive fillers, and anchors itself on the surface of the fillers by the functional segment; the introduced ferrous ions act as ion crosslinking centers, bridging the polymer chains adsorbed on different fillers, and pre-constructing a flexible conductive network at the molecular level. During the curing process of the coating to form a film, this pre-formed two-dimensional network structure is more easily arranged into a layered structure parallel to the substrate under physical action, and finally forms a conductive path with high throughness and stable structure, thereby significantly improving the electromagnetic shielding performance of the coating. DETAILED DESCRIPTION

[0070] The technical solutions of the present application will be described in detail below with specific examples. The examples described herein are specific embodiments of the present application, which are used to illustrate the concept of the present application; all the descriptions are explanatory and exemplary, and should not be understood as limiting the embodiments of the present application and the protection scope of the present application. In addition to the examples described herein, those skilled in the art can also employ other technical solutions based on the content disclosed in the claims and the description of the present application, which include technical solutions employing any obvious substitutions and modifications to the examples described herein.

[0071] The chemical reagents used in the examples and comparative examples of the present application are all commercially available products without further purification or treatment.

[0072] Example 1

[0073] The present example provides an electromagnetic shielding waterborne epoxy coating containing graphene copper composite filler and a preparation method thereof. The preparation method of the electromagnetic shielding waterborne epoxy coating containing graphene copper composite filler specifically comprises the following steps:

[0074] S1: Disperse polyvinylpyrrolidone in deionized water to obtain a polyvinylpyrrolidone solution, wherein the mass-volume ratio of polyvinylpyrrolidone to deionized water is 12:95 g / mL, add methacrylic acid, dimethylaminoethyl methacrylate and ammonium persulfate to obtain a reaction solution E, wherein the mass ratio of polyvinylpyrrolidone to methacrylic acid, dimethylaminoethyl methacrylate and ammonium persulfate is 12:8:2:0.2, and react at 70°C for 2h to obtain a partially grafted amphiphilic block copolymer solution, add a 1wt.% ferrous chloride solution to obtain a reaction solution F, wherein the amount of ferrous chloride is 0.8% of the mass of the partially grafted amphiphilic block copolymer solution, and stir at 30°C for 1.7h, and then distill under reduced pressure to obtain a conductive path regulator with a solid content of 12%;

[0075] S2: Mix graphene and deionized water at a mass ratio of 1:27, and add an ionic-dynamic bonding type micro-interface bridging agent, wherein the amount of ionic-dynamic bonding type micro-interface bridging agent is 4% of the mass of graphene, and ultrasonically treat at 400W for 20min to obtain a graphene slurry; add antioxidant / anti-corrosion composite protected copper powder, wherein the mass ratio of graphene to antioxidant / anti-corrosion composite protected copper powder is 1:4, and stir and defoam to obtain a graphene-copper composite slurry;

[0076] S3: The epoxy resin emulsion is premixed with the curing agent Anquamine 287 at a mass ratio of 100:50, 0.2% of the leveling agent BYK-348 based on the mass of the epoxy resin emulsion is added, and 0.26% of the defoaming agent BYK-024 based on the mass of the epoxy resin emulsion is added, and stirred uniformly to obtain a first mixed coating; the graphene-copper composite slurry is added and stirred to disperse uniformly to obtain a second mixed coating, wherein the addition amount of the graphene-copper composite slurry is 27% of the mass of the first mixed coating, and 2% of the conductive path regulator based on the mass of the first mixed coating is added, and mixed uniformly to obtain an electromagnetic shielding water-based epoxy coating containing graphene copper composite fillers.

[0077] The preparation steps of the ion-dynamic bonding type micro-interface bridging agent are as follows:

[0078] N-vinylimidazole, acrylic acid, and glycidyl methacrylate are dispersed in a deionized water / ethanol mixed solution to obtain a mixed monomer dispersion liquid with a total mass fraction of 18 wt.%, wherein the volume ratio of deionized water to ethanol is 1:1.5, the mass ratio of N-vinylimidazole to acrylic acid is 1:0.4, and the mass ratio of N-vinylimidazole to glycidyl methacrylate is 1:0.2; ammonium persulfate and tetramethyl ethylenediamine are added to obtain reaction liquid A, wherein the total mole ratio of ammonium persulfate to mixed monomers is 0.015:1, and the mole ratio of tetramethyl ethylenediamine to ammonium persulfate is 1.6:1; after adjusting the pH to 6, reaction liquid B is obtained by stirring at 60°C for 3h; after adding a 7.6 wt.% potassium dihydrogen phosphate solution, triethanolamine is added to adjust the solution pH to 7.5 to obtain reaction liquid C, wherein the total mole ratio of potassium dihydrogen phosphate to mixed monomers is 0.1:1; stirring is carried out at 52°C for 2h; filtration and reduced pressure distillation are performed to obtain an ion-dynamic bonding type micro-interface bridging agent with a solid content of 25%;

[0079] The preparation steps of the antioxidant / anti-corrosion composite protected copper powder are as follows:

[0080] A zirconium oxychloride solution with a mass fraction of 3 wt.% and an ethanol solution of methyl triethoxysilane with a mass fraction of 8 wt.% are prepared; the zirconium oxychloride solution and the ethanol solution of methyl triethoxysilane with a mass fraction of 8 wt.% are mixed at a volume ratio of 1:1; while stirring, 12 wt.% ammonia water is added dropwise to adjust the pH to 3 to obtain an organic-inorganic precursor solution; copper powder is added to the organic-inorganic precursor solution to obtain reaction liquid D, wherein the solid-liquid mass ratio of copper powder to organic-inorganic precursor solution is 1:7; stirring is carried out at 30°C for 1h; 2-mercaptoimidazole is added and stirring is continued for 30min to obtain a pretreatment liquid, wherein the amount of 2-mercaptoimidazole added is 0.3% of the mass of the copper powder; rotary evaporation and drying are performed to obtain an antioxidant / anti-corrosion composite protected copper powder.

[0081] Example 2

[0082] The embodiment provides an electromagnetic shielding waterborne epoxy coating containing graphene copper composite filler and a preparation method.

[0083] S1: polyvinylpyrrolidone is dispersed in deionized water to obtain a polyvinylpyrrolidone solution, wherein the mass-volume ratio of polyvinylpyrrolidone to deionized water is 13:97 g / mL, methacrylic acid, dimethylaminoethyl methacrylate and ammonium persulfate are added to obtain a reaction liquid E, wherein the mass ratio of polyvinylpyrrolidone to methacrylic acid, dimethylaminoethyl methacrylate and ammonium persulfate is 13:7:1:0.1, and the reaction is carried out at 75°C for 3h to obtain a partially grafted amphiphilic block copolymer solution, a 1.6wt.% ferrous chloride solution is added to obtain a reaction liquid F, wherein the feeding amount of ferrous chloride is 0.7% of the mass of the partially grafted amphiphilic block copolymer solution, and the stirring reaction is carried out at 35°C for 1h, and the conductive path regulator with a solid content of 10% is obtained by reduced pressure distillation;

[0084] S2: graphene and deionized water are mixed in a mass ratio of 1:24, and an ionic-dynamic bonding type micro-interface bridging agent is added, wherein the feeding amount of the ionic-dynamic bonding type micro-interface bridging agent is 2% of the mass of the graphene, and the graphene slurry is obtained by ultrasonic treatment at 450W for 22min; antioxidant / anti-corrosion composite protective copper powder is added, wherein the mass ratio of graphene to antioxidant / anti-corrosion composite protective copper powder is 1:4.5, and the graphene-copper composite slurry is obtained by stirring and defoaming;

[0085] S3: the epoxy resin emulsion and the curing agent Anquamine 401 are premixed in a mass ratio of 100:55, the leveling agent BYK-348 is added in an amount of 0.25% of the mass of the epoxy resin emulsion, and the defoaming agent BYK-024 is added in an amount of 0.1% of the mass of the epoxy resin emulsion, and the first mixed coating is obtained by stirring uniformly; the graphene-copper composite slurry is added and uniformly dispersed to obtain the second mixed coating, wherein the addition amount of the graphene-copper composite slurry is 20% of the mass of the first mixed coating, the conductive path regulator is added in an amount of 2.4% of the mass of the first mixed coating, and the electromagnetic shielding waterborne epoxy coating containing graphene copper composite filler is obtained by uniformly mixing.

[0086] The preparation steps of the ionic-dynamic bonding type micro-interface bridging agent are as follows:

[0087] N-vinylimidazole, acrylic acid, and glycidyl methacrylate were dispersed in a deionized water / ethanol mixed solution to obtain a mixed monomer dispersion solution with a total mass fraction of 10 wt.%, wherein the volume ratio of deionized water to ethanol was 1:1.8, the mass ratio of N-vinylimidazole to acrylic acid was 1:0.3, the mass ratio of N-vinylimidazole to glycidyl methacrylate was 1:0.3, ammonium persulfate and tetramethylethylenediamine were added to obtain a reaction solution A, wherein the total mole ratio of ammonium persulfate to mixed monomers was 0.01:1, the mole ratio of tetramethylethylenediamine to ammonium persulfate was 1.7:1, the pH was adjusted to 6.5, and then the solution was stirred at 68°C for 4.5h to obtain a reaction solution B, then a 5wt.% potassium dihydrogen phosphate solution was added, followed by the addition of triethanolamine to adjust the pH of the solution to 6 to obtain a reaction solution C, wherein the total mole ratio of potassium dihydrogen phosphate to mixed monomers was 0.12:1, the solution was stirred at 53°C for 2.5h, and then filtered and distilled under reduced pressure to obtain an ion-dynamic bonding type micro-interface bridging agent with a solid content of 27%;

[0088] The preparation steps of the antioxidant / corrosion-resistant composite protective copper powder are as follows:

[0089] A 4wt.% zirconium oxychloride solution and a 6wt.% methyl triethoxysilane ethanol solution were prepared, the zirconium oxychloride solution and the 7wt.% methyl triethoxysilane ethanol solution were mixed at a volume ratio of 1:1.5, and a 14wt.% ammonia water was added dropwise while stirring to adjust the pH to 3.5 to obtain an organic-inorganic precursor solution; copper powder was added to the organic-inorganic precursor solution to obtain a reaction solution D, wherein the solid-liquid mass ratio of copper powder to organic-inorganic precursor solution was 1:6, the solution was stirred at 35°C for 1.2h, and then 2-mercaptoimidazole was added and stirred for 35min to obtain a pretreatment solution, wherein the amount of 2-mercaptoimidazole added was 0.4% of the mass of the copper powder, and then rotary evaporation and drying were performed to obtain an antioxidant / corrosion-resistant composite protective copper powder.

[0090] Example 3

[0091] The embodiment provides an electromagnetic shielding waterborne epoxy coating containing graphene copper composite filler and a preparation method thereof, and the preparation method of the electromagnetic shielding waterborne epoxy coating containing graphene copper composite filler specifically comprises the following steps:

[0092] S1: polyvinylpyrrolidone was dispersed in deionized water to obtain a polyvinylpyrrolidone solution, wherein the mass-volume ratio of polyvinylpyrrolidone to deionized water was 10:90 g / mL, methacrylic acid, dimethylaminoethyl methacrylate and ammonium persulfate were added to obtain a reaction liquid E, wherein the mass ratio of polyvinylpyrrolidone to methacrylic acid, dimethylaminoethyl methacrylate and ammonium persulfate was 10:5:2.5:0.3, and the reaction was carried out at 77°C for 3.5h to obtain a partially grafted amphiphilic block copolymer solution, and a 1.8wt.% ferrous chloride solution was added to obtain a reaction liquid F, wherein the amount of ferrous chloride was 0.5% of the mass of the partially grafted amphiphilic block copolymer solution, and the reaction was carried out at 38°C for 1.5h under stirring, and the product was obtained by distillation under reduced pressure, and the solid content of the product was 13% conductive path regulator;

[0093] S2: graphene and deionized water were mixed in a mass ratio of 1:20, and an ionic-dynamic bonding type micro-interface bridging agent was added, wherein the amount of ionic-dynamic bonding type micro-interface bridging agent was 5% of the mass of graphene, and the graphene slurry was obtained by ultrasonic treatment at 300W for 15min; antioxidant / anticorrosion composite protective copper powder was added, wherein the mass ratio of graphene to antioxidant / anticorrosion composite protective copper powder was 1:3, and the graphene-copper composite slurry was obtained by stirring and defoaming;

[0094] S3: the epoxy resin emulsion and the curing agent Anquamine 287 were premixed in a mass ratio of 100:40, the leveling agent BYK-348 was added in an amount of 0.1% of the mass of the epoxy resin emulsion, and the defoaming agent BYK-024 was added in an amount of 0.2% of the mass of the epoxy resin emulsion, and the first mixed paint was obtained by stirring uniformly; the graphene-copper composite slurry was added and dispersed uniformly to obtain the second mixed paint, wherein the addition amount of the graphene-copper composite slurry was 25% of the mass of the first mixed paint, and the conductive path regulator was added in an amount of 1% of the mass of the first mixed paint, and the electromagnetic shielding water-based epoxy paint containing graphene-copper composite filler was obtained by mixing uniformly.

[0095] The preparation steps of the ionic-dynamic bonding type micro-interface bridging agent are as follows:

[0096] N-vinylimidazole, acrylic acid, and glycidyl methacrylate were dispersed in a deionized water / ethanol mixed solution to obtain a mixed monomer dispersion solution with a total mass fraction of 15 wt.%, wherein the volume ratio of deionized water to ethanol was 1:1, the mass ratio of N-vinylimidazole to acrylic acid was 1:0.47, and the mass ratio of N-vinylimidazole to glycidyl methacrylate was 1:0.35; ammonium persulfate and tetramethylethylenediamine were added to obtain a reaction solution A, wherein the total mole ratio of ammonium persulfate to mixed monomers was 0.018:1, and the mole ratio of tetramethylethylenediamine to ammonium persulfate was 1:1; after adjusting the pH to 5, the reaction solution B was obtained by stirring at 65°C for 5h; after adding a 7 wt.% potassium dihydrogen phosphate solution, triethanolamine was added to adjust the pH of the solution to 7 to obtain a reaction solution C, wherein the total mole ratio of potassium dihydrogen phosphate to mixed monomers was 0.05:1; the reaction solution was stirred at 50°C for 2.8h; filtration and reduced pressure distillation were performed to obtain an ionic-dynamic bonding type micro-interface bridging agent with a solid content of 20%;

[0097] The preparation steps of the antioxidant / corrosion-resistant composite protective copper powder are as follows:

[0098] A 1 wt.% zirconium oxychloride solution and a 5 wt.% methyl triethoxysilane ethanol solution were prepared, the zirconium oxychloride solution and the 5 wt.% methyl triethoxysilane ethanol solution were mixed at a volume ratio of 1:1.7, and a 10 wt.% ammonia water was added dropwise while stirring to adjust the pH to 3.8 to obtain an organic-inorganic precursor solution; copper powder was added to the organic-inorganic precursor solution to obtain a reaction solution D, wherein the solid-liquid mass ratio of copper powder to the organic-inorganic precursor solution was 1:5, the reaction solution was stirred at 38°C for 1.3h, and 2-mercaptoimidazole was added and continued to be stirred for 38min to obtain a pretreatment solution, wherein the amount of 2-mercaptoimidazole was 0.1% of the mass of the copper powder; rotary evaporation and drying were performed to obtain the antioxidant / corrosion-resistant composite protective copper powder.

[0099] Example 4

[0100] The embodiment provides an electromagnetic shielding waterborne epoxy coating containing a graphene copper composite filler and a preparation method thereof, and the preparation method of the electromagnetic shielding waterborne epoxy coating containing the graphene copper composite filler specifically comprises the following steps:

[0101] S1: polyvinylpyrrolidone was dispersed in deionized water to obtain a polyvinylpyrrolidone solution, wherein the mass-volume ratio of polyvinylpyrrolidone to deionized water was 15:100 g / mL, methacrylic acid, dimethylaminoethyl methacrylate and ammonium persulfate were added to obtain a reaction liquid E, wherein the mass ratio of polyvinylpyrrolidone to methacrylic acid, dimethylaminoethyl methacrylate and ammonium persulfate was 15:10:3:0.26, and the reaction was carried out at 80°C for 4h to obtain a partially grafted amphiphilic block copolymer solution, a 2wt.% ferrous chloride solution was added to obtain a reaction liquid F, wherein the amount of ferrous chloride was 1% of the mass of the partially grafted amphiphilic block copolymer solution, and the reaction was carried out at 40°C for 2h under stirring, and a conductive path regulator with a solid content of 15% was obtained by distillation under reduced pressure;

[0102] S2: graphene and deionized water were mixed in a mass ratio of 1:30, and an ionic-dynamic bonding type micro-interface bridging agent was added, wherein the amount of ionic-dynamic bonding type micro-interface bridging agent was 3% of the mass of graphene, and the graphene slurry was obtained by ultrasonic treatment at 500W for 30min; antioxidant / anti-corrosion composite protective copper powder was added, wherein the mass ratio of graphene to antioxidant / anti-corrosion composite protective copper powder was 1:5, and the graphene-copper composite slurry was obtained by stirring and defoaming;

[0103] S3: the epoxy resin emulsion and the curing agent Anquamine 287 were premixed in a mass ratio of 100:60, the leveling agent BYK-348 was added in an amount of 0.3% of the mass of the epoxy resin emulsion, and the defoaming agent BYK-024 was added in an amount of 0.3% of the mass of the epoxy resin emulsion, and the first mixed paint was obtained by stirring uniformly; the graphene-copper composite slurry was added and dispersed uniformly to obtain the second mixed paint, wherein the addition amount of the graphene-copper composite slurry was 30% of the mass of the first mixed paint, and the conductive path regulator was added in an amount of 3% of the mass of the first mixed paint, and the electromagnetic shielding water-based epoxy paint containing graphene-copper composite filler was obtained by mixing uniformly.

[0104] The preparation steps of the ionic-dynamic bonding type micro-interface bridging agent are as follows:

[0105] N-vinylimidazole, acrylic acid, and glycidyl methacrylate were dispersed in a deionized water / ethanol mixed solution to obtain a mixed monomer dispersion solution with a total mass fraction of 20 wt.%, wherein the volume ratio of deionized water to ethanol was 1:2, the mass ratio of N-vinylimidazole to acrylic acid was 1:0.5, the mass ratio of N-vinylimidazole to glycidyl methacrylate was 1:0.4, ammonium persulfate and tetramethylethylenediamine were added to obtain a reaction solution A, wherein the total mole ratio of ammonium persulfate to mixed monomers was 0.02:1, the mole ratio of tetramethylethylenediamine to ammonium persulfate was 2:1, the pH was adjusted to 7, and then the reaction solution was stirred at 70°C for 4.8h to obtain a reaction solution B, then an 8 wt.% potassium dihydrogen phosphate solution was added, followed by the addition of triethanolamine to adjust the pH of the solution to 8 to obtain a reaction solution C, wherein the total mole ratio of potassium dihydrogen phosphate to mixed monomers was 0.15:1, and the reaction was stirred at 55°C for 3h, then filtered and distilled under reduced pressure to obtain an ion-dynamic bonding type micro-interface bridging agent with a solid content of 30%;

[0106] The preparation steps of the antioxidant / corrosion-resistant composite protective copper powder are as follows:

[0107] A 5 wt.% zirconium oxychloride solution and a 10 wt.% methyl triethoxysilane ethanol solution were prepared, and the zirconium oxychloride solution and the 10 wt.% methyl triethoxysilane ethanol solution were mixed at a volume ratio of 1:2, and then 15 wt.% ammonia water was added dropwise while stirring to adjust the pH to 4 to obtain an organic-inorganic precursor solution; copper powder was added to the organic-inorganic precursor solution to obtain a reaction solution D, wherein the solid-liquid mass ratio of copper powder to organic-inorganic precursor solution was 1:8, and the reaction was stirred at 40°C for 1.5h, then 2-mercaptoimidazole was added and stirring was continued for 40min to obtain a pretreatment solution, wherein the amount of 2-mercaptoimidazole added was 0.5% of the mass of the copper powder, and then rotary evaporation and drying were performed to obtain an antioxidant / corrosion-resistant composite protective copper powder.

[0108] Comparative Example 1

[0109] This comparative example provides an electromagnetic shielding waterborne epoxy coating containing graphene copper composite filler, which is different from Example 1 in that no ion-dynamic bonding type micro-interface bridging agent is added in S2, and graphene is directly mixed with antioxidant / corrosion-resistant composite protective copper powder, and other operation steps and process parameters are exactly the same as those of Example 1.

[0110] Comparative Example 2

[0111] This comparative example provides an electromagnetic shielding waterborne epoxy coating containing graphene copper composite filler, which is different from Example 1 in that ordinary copper powder without antioxidant / corrosion-resistant composite protection is used, and other operation steps and process parameters are exactly the same as those of Example 1.

[0112] Comparative Example 3

[0113] The comparative example provides an electromagnetic shielding waterborne epoxy coating containing graphene copper composite filler, which is different from Example 1 in that no methyl triethoxysilane is added in the preparation step of the anti-oxidation / anti-corrosion composite protective copper powder, and other operation steps and process parameters are exactly the same as those of Example 1.

[0114] Comparative Example 4

[0115] The comparative example provides an electromagnetic shielding waterborne epoxy coating containing graphene copper composite filler, which is different from Example 1 in that no conductive path regulator is used, and the conductive filler is only dispersed by mechanical stirring, and other operation steps and process parameters are exactly the same as those of Example 1.

[0116] The electromagnetic shielding waterborne epoxy coatings containing graphene copper composite fillers of Examples 1-4 and Comparative Examples 1-4 are tested for performance, and the specific process is as follows:

[0117] The electromagnetic shielding efficiency of the coating is tested according to GB / T 30142-2013;

[0118] The impact resistance performance of the coating is tested according to GB / T 1732-2020;

[0119] The volume resistivity of the coating is tested according to GB / T 16906-1997;

[0120] The adhesion of the coating is tested according to GB / T 1720-2020;

[0121] Heat resistance: the coating is placed in a blast oven and treated at 300℃ for 24h, and then the electromagnetic shielding efficiency of the coating after high temperature treatment is tested according to GB / T 30142-2013.

[0122] The test results are shown in Table 1.

[0123] Table 1: Shielding efficiency of electromagnetic shielding waterborne epoxy coatings containing graphene copper composite fillers of Examples 1-4 and Comparative Examples 1-4

[0124] Electromagnetic shielding effectiveness dB Electromagnetic shielding effectiveness dB after heat resistance Impact resistance strength kg-cm Volume resistivity mΩ-cm Adhesion level Example 1 83 73 51 4 1 Example 2 81 71 50 5 1 Example 3 80 69 48 6 1 Example 4 82 70 49 5 1 Comparative Example 1 65 52 45 10 2 Comparative Example 2 50 35 47 15 1 Comparative Example 3 58 45 50 12 1 Comparative Example 4 55 40 56 11 1

[0125] From the test results of Example 1 and Comparative Example 1, it can be seen that the absence of the ion-dynamic bonding type micro-interface bridging agent leads to a decrease in the dispersibility and interface bonding force of graphene and copper powder, uneven distribution of fillers in the matrix, a decrease in the construction efficiency of the conductive network, and a significant decrease in the shielding performance; the absence of the effect of the dynamic bond of the bridging agent being converted into a stable bond after solidification leads to the conductive network being more easily damaged due to thermal expansion and contraction or matrix softening at high temperatures, and a decrease in the shielding performance; the absence of the bridging agent leads to a decrease in the interface bonding force of the fillers and the matrix, and the fillers are easily detached under impact load, resulting in a decrease in the impact resistance; uneven distribution of the fillers and poor interface contact weaken the continuity of the conductive path, and the overall electrical conductivity decreases; the absence of the chemical cross-linking and multi-point anchoring effects of the bridging agent leads to a decrease in the interface bonding strength and adhesion.

[0126] From the test results of Example 1 and Comparative Example 2, it can be seen that unprotected copper powder is easily oxidized in the aqueous system, the high resistivity of the oxidation layer significantly decreases the conductive performance of the copper powder, destroys the conductive network, and leads to a significant decrease in the electromagnetic shielding performance; the copper powder is further oxidized at high temperatures, a thicker oxidation layer is formed, the conductive network is severely damaged, and the shielding performance is greatly decreased; although the copper powder is oxidized, its particle morphology is not significantly affected, and therefore the impact on the mechanical properties is small. However, due to the decrease in the interface bonding force, the impact resistance performance is slightly decreased; the high resistivity of the oxidation layer on the surface of the copper powder greatly increases the contact resistance between the fillers, and the conductive performance is significantly deteriorated; the oxidation of the copper powder mainly affects the electrical conductivity, and has a small impact on the adhesion between the coating film and the substrate.

[0127] From the test results of Example 1 and Comparative Example 3, it can be seen that the absence of methyl triethoxysilane leads to the protective film being composed of only an inorganic skeleton formed by zirconium oxychloride, the structure is relatively simple, and the hydrophobicity is insufficient, leading to a decrease in the oxidation resistance of the copper powder, damage to the conductive network, and a decrease in the shielding performance; the single inorganic film has limited inhibitory effect on high-temperature oxidation, and the oxidation of the copper powder is intensified in a high-temperature environment, leading to a decrease in the shielding performance; the defects of the protective film have limited impact on the interface bonding force, and therefore have a small impact on the impact resistance of the coating film; the decrease in the hydrophobicity and compactness of the protective film leads to a decrease in the contact quality between the fillers, and the continuity of the conductive path is decreased; the protective film mainly acts on the surface of the copper powder, and has a small impact on the adhesion to the substrate.

[0128] From the test results of Example 1 and Comparative Example 4, it can be seen that the absence of the dispersion and bridging effect of the conductive path regulating agent leads to disordered distribution of graphene and copper powder in the matrix due to easy agglomeration, a significant decrease in the construction efficiency of the conductive network, and a decrease in the shielding performance; such disordered arrangement of the conductive network formed by physical lapping is more easily broken due to thermal expansion and contraction or matrix softening at high temperatures, leading to a decrease in the shielding performance; mechanical stirring dispersion has a small impact on the mechanical properties of the coating film; the contact resistance between the agglomerated and disordered distributed fillers is large, the conductive path is discontinuous, leading to an increase in the volume resistivity; the absence of the conductive path regulating agent has a small impact on the adhesion between the coating film and the substrate.

[0129] The above merely provides the specific implementation of the present application, but the protection scope of the present application is not limited thereto, and it should be understood by those skilled in the art that any change or replacement within the technical scope disclosed by the present application can be easily thought out by those skilled in the art, and falls within the protection scope and disclosure scope of the present application.

Claims

1. A method for preparing an electromagnetic shielding waterborne epoxy coating containing graphene-copper composite filler, characterized in that, The preparation method includes: S1: Polyvinylpyrrolidone is dispersed in deionized water to obtain a polyvinylpyrrolidone solution. Methacrylic acid, dimethylaminoethyl methacrylate and ammonium persulfate are added to obtain reaction solution E. The reaction yields a partially grafted amphiphilic block copolymer solution. Ferrous chloride solution is added to obtain reaction solution F. The reaction is stirred and the conductive path modifier is obtained by vacuum distillation. S2: Graphene is mixed with deionized water and an ion-dynamic bonding micro-interface bridging agent is added. The mixture is then ultrasonically treated to obtain a graphene slurry. Antioxidant / corrosion-resistant composite protective copper powder is added, and the mixture is stirred and defoamed to obtain a graphene-copper composite slurry. S3: Premix epoxy resin emulsion with curing agent, add leveling agent and defoamer, stir evenly to obtain first mixed coating; add graphene-copper composite slurry and stir to disperse evenly to obtain second mixed coating; add conductive path modifier and mix evenly to obtain electromagnetic shielding waterborne epoxy coating containing graphene copper composite filler. The preparation steps of the ion-dynamic bonded micro-interface bridging agent are as follows: N-vinylimidazolium, acrylic acid, and glycidyl methacrylate were dispersed in a deionized water / ethanol mixture to obtain a mixed monomer dispersion. Ammonium persulfate and tetramethylethylenediamine were added to obtain reaction solution A. After adjusting the pH, the reaction was stirred to obtain reaction solution B. Potassium dihydrogen phosphate solution was added, followed by triethanolamine to obtain reaction solution C. The reaction was stirred, filtered, and distilled under reduced pressure to obtain an ion-dynamic bonded micro-interface bridging agent. The preparation steps of the antioxidant / corrosion-resistant composite protective copper powder are as follows: Prepare a zirconium oxychloride solution and an ethanol solution of methyltriethoxysilane. Mix the zirconium oxychloride solution and the ethanol solution of methyltriethoxysilane, and adjust the pH by adding ammonia dropwise while stirring to obtain an organic-inorganic precursor solution. Add copper powder to the organic-inorganic precursor solution to obtain reaction solution D. Stir the reaction, add 2-mercaptoimidazole and continue stirring to obtain a pretreatment solution. Rotary evaporate and dry to obtain antioxidant / corrosion-resistant composite protective copper powder.

2. The method for preparing the electromagnetic shielding waterborne epoxy coating containing graphene copper composite filler according to claim 1, characterized in that, In S1: The mass-to-volume ratio of polyvinylpyrrolidone to deionized water is (10-15) g: (90-100) mL; The mass ratio of polyvinylpyrrolidone to methacrylic acid, dimethylaminoethyl methacrylate, and ammonium persulfate is (10-15):(5-10):(1-3):(0.1-0.3). The amount of ferrous chloride added is 0.5-1% of the mass of the partially grafted amphiphilic block copolymer solution; The solid content of the conductive path modifier is 10-15%.

3. The method for preparing the electromagnetic shielding waterborne epoxy coating containing graphene copper composite filler according to claim 1, characterized in that, In S2: The mass ratio of the graphene to deionized water is 1:20-30; The amount of the ion-dynamic bonded micro-interface bridging agent is 2-5% of the graphene mass; The mass ratio of graphene to antioxidant / corrosion-resistant composite protective copper powder is 1:3-5.

4. The method for preparing the electromagnetic shielding waterborne epoxy coating containing graphene copper composite filler according to claim 1, characterized in that, In S3: The mass ratio of the epoxy resin emulsion to the curing agent is 100:40-60; The leveling agent is added at a rate of 0.1-0.3% of the epoxy resin emulsion mass. The amount of defoamer added is 0.1-0.3% of the mass of the epoxy resin emulsion; The amount of graphene-copper composite slurry added is 20-30% of the mass of the first mixed coating. The amount of the conductive path modifier added is 1-3% of the mass of the first mixed coating.

5. The method for preparing the electromagnetic shielding waterborne epoxy coating containing graphene copper composite filler according to claim 1, characterized in that, In the preparation steps of the ion-dynamic bonded micro-interface bridging agent: The mass ratio of N-vinylimidazolium to acrylic acid is 1:(0.3-0.5). The mass ratio of N-vinylimidazolium to glycidyl methacrylate is 1:(0.2-0.4). The total molar ratio of ammonium persulfate to the mixed monomers is 0.01-0.02:1; The molar ratio of tetramethylethylenediamine to ammonium persulfate is 1-2:

1.

6. The method for preparing the electromagnetic shielding waterborne epoxy coating containing graphene copper composite filler according to claim 1, characterized in that, In the preparation steps of the ion-dynamic bonded micro-interface bridging agent: The total molar ratio of potassium dihydrogen phosphate to the mixed monomers is 0.05-0.15:1; After adding potassium dihydrogen phosphate solution to reaction solution B, triethanolamine is added until the pH of the solution is 6-8. The solid content of the ion-dynamic bonded micro-interface bridging agent is 20-30%.

7. The method for preparing the electromagnetic shielding waterborne epoxy coating containing graphene copper composite filler according to claim 1, characterized in that, In the preparation steps of the antioxidant / corrosion-resistant composite protective copper powder: The zirconium oxychloride solution has a mass fraction of 1-5 wt.%. The ethanol solution of methyltriethoxysilane has a mass fraction of 5-10 wt.%. The zirconium oxychloride solution and the ethanol solution of methyltriethoxysilane were mixed at a volume ratio of 1:1-2. The solid-liquid mass ratio of the copper powder to the organic-inorganic precursor solution is 1:5-8; The amount of 2-mercaptoimidazole added is 0.1-0.5% of the mass of copper powder.

8. An electromagnetic shielding waterborne epoxy coating containing graphene copper composite filler, characterized in that, It is prepared according to any one of claims 1-7.