Electromagnetic shielding water-based epoxy coating containing graphene copper composite filler and preparation method of electromagnetic shielding water-based epoxy coating

Abstract

The invention provides an electromagnetic shielding waterborne epoxy coating containing a graphene copper composite filler and a preparation method, and belongs to the technical field of coatings. According to the invention, three additives are introduced to solve the problems of poor interface bonding of graphene, copper particles and an epoxy matrix, easy oxidation of the copper particles and non-uniform distribution of conductive paths; the bridging agent realizes multi-point anchoring and interface bonding of the filler through dynamic bond action, and a stable conductive network is formed after curing; according to the bionic mixed protective film, zirconium oxychloride and methyltriethoxysilane cooperate to form a compact barrier, and the oxidation resistance of copper particles is effectively improved in combination with the intelligent release function of 2-mercaptoimidazole; the conductive path regulating agent pre-constructs a conductive network through an ionic bond bridging effect, and formation of an efficient through conductive layered structure is promoted; the three components cooperate to construct an efficient, stable and durable conductive network, and the electromagnetic shielding performance of the waterborne epoxy coating is improved.

Description

Technical Field

[0001] This invention belongs to the field of coating technology and relates to an electromagnetic shielding waterborne epoxy coating containing graphene copper composite filler and its preparation method. Background Technology

[0002] Electromagnetic shielding coatings are widely used in electronic devices, communication technologies, and the military to protect sensitive electronic components from electromagnetic interference. However, due to increasing sensitivity to electromagnetic interference, particularly in high-frequency and high-density integrated circuits, traditional shielding materials are increasingly revealing their inherent shortcomings, such as excessive weight, complex installation, and limited shielding performance. In recent years, graphene, as a novel nanomaterial, has attracted widespread attention due to its excellent electrical conductivity, strength, and thermal stability. Combining graphene with metallic materials can significantly improve the conductivity and electromagnetic shielding capabilities of coatings. However, this composite material still faces a series of technical challenges in practical applications.

[0003] First, the interfacial interaction between graphene and copper is typically weak, resulting in poor dispersibility and stability in aqueous epoxy systems. The surface chemical differences between graphene and metallic copper easily lead to agglomeration and interfacial debonding, hindering the formation of a continuous conductive network. This limits the formation of effective conductive paths in the coating by the graphene / copper composite filler, thus affecting electromagnetic shielding performance. Second, in aqueous environments, copper powder is easily oxidized, leading to a significant decrease in conductivity. The oxide layer formed on the oxidized copper surface not only reduces conductivity but may also cause interfacial defects, further reducing shielding efficiency. Furthermore, during film formation, conductive fillers may exhibit delamination or misalignment. Even with good initial dispersion, micro-phase separation may occur during curing or use, resulting in the "cutting off" or "weakening" of conductive pathways. This uneven distribution directly affects the overall performance of the electromagnetic shielding coating. Summary of the Invention

[0004] To address the aforementioned problems, the present invention aims to provide an electromagnetic shielding waterborne epoxy coating containing graphene-copper composite filler and its preparation method. This application solves the problems of poor interfacial bonding between graphene, copper particles, and epoxy matrix, easy oxidation of copper particles, and uneven distribution of conductive paths by introducing an ion-dynamic bonding micro-interface bridging agent, a biomimetic organic-inorganic hybrid protective film, and a conductive path regulator. The bridging agent achieves multi-point anchoring and interfacial bonding of the filler through dynamic bonding, forming a stable conductive network after curing. The biomimetic hybrid protective film forms a dense barrier through the synergistic formation of zirconium oxychloride and methyltriethoxysilane, and effectively enhances the oxidation resistance of copper particles by combining the intelligent release function of 2-mercaptoimidazole. The conductive path regulator achieves efficient dispersion and stabilization of the conductive filler through its amphiphilic structure, and utilizes the introduced metal ions as dynamic crosslinking centers to pre-bridge the dispersed filler into a network at the molecular level, ultimately promoting the formation of a highly efficient and interconnected conductive layered structure during film formation. These three components synergistically construct a highly efficient, stable, and durable conductive network, improving the electromagnetic shielding performance of the waterborne epoxy coating.

[0005] To achieve this objective, the present invention adopts the following technical solution:

[0006] In a first aspect, the present invention provides a method for preparing an electromagnetic shielding waterborne epoxy coating containing graphene copper composite filler, the method comprising:

[0007] 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.

[0008] 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.

[0009] S3: Premix epoxy resin emulsion with curing agent, add leveling agent and defoamer, stir evenly to obtain the first mixed coating; add graphene-copper composite slurry and stir to disperse evenly to obtain the second mixed coating; add conductive path modifier and mix evenly to obtain an electromagnetic shielding waterborne epoxy coating containing graphene copper composite filler.

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

[0011] 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.

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

[0013] 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.

[0014] As a preferred technical solution of the present invention, in step S1, the mass-to-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 reaction temperature of the reaction solution E is 70-80°C, for example, it can be 70°C, 71°C, 72°C, 73°C, 74°C, 75°C, 76°C, 77°C, 78°C, 79°C or 80°C, but is not limited to the listed values, other unlisted values ​​within this range are also applicable.

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

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

[0019] In some optional embodiments, the amount of ferrous chloride added 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 is not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0020] In some optional embodiments, the reaction temperature of the reaction liquid F is 30-40°C, for example, it can be 30°C, 31°C, 32°C, 33°C, 34°C, 35°C, 36°C, 37°C, 38°C, 39°C or 40°C, but is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0021] In some optional embodiments, the reaction time of the reaction solution F is 1-2 hours, for example, it can be 1 hour, 1.1 hours, 1.2 hours, 1.3 hours, 1.4 hours, 1.5 hours, 1.6 hours, 1.7 hours, 1.8 hours, 1.9 hours or 2 hours, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0022] In some optional embodiments, the solid content of the conductive path modifier 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 is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0023] As a preferred technical solution of the present invention, 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 it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0024] In some optional embodiments, the amount of the ion-dynamically bonded micro-interface bridging agent is 2-5% of the graphene mass, 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 is not limited to the listed values, other unlisted values ​​within this range are also applicable.

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

[0026] In some optional embodiments, the duration of the ultrasonic treatment is 15-30 min, for example, it 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 is not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0027] In some optional embodiments, the mass ratio of graphene to antioxidant / corrosion-resistant composite protective copper powder is 1:3-5, for example, it 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 is not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0028] As a preferred technical solution of the present invention, 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, it 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 is not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0030] In some optional embodiments, the leveling agent BYK-348 is added at a rate of 0.1-0.3% of the epoxy resin emulsion mass, for example, 0.1%, 0.12%, 0.14%, 0.16%, 0.18%, 0.20%, 0.22%, 0.24%, 0.26%, 0.28%, or 0.3%, but is not limited to the listed values; other unlisted values ​​within this range are also applicable.

[0031] In some optional embodiments, the amount of defoamer BYK-024 added is 0.1-0.3% of the mass of the epoxy resin emulsion, for example, it 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 is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0032] In some optional embodiments, the amount of graphene-copper composite slurry added is 20-30% of the mass of the first mixed coating, 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 unlisted values ​​within this range are also applicable.

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

[0034] As a preferred technical solution of the present invention, in the preparation step of the ion-dynamic bonded micro-interface bridging agent, the volume ratio of deionized water to ethanol is 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 it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

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

[0036] In some alternative embodiments, the mass ratio of N-vinylimidazole to acrylic acid is 1:(0.3-0.5), for example, it 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 is not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0037] In some alternative embodiments, the mass ratio of 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, other unlisted values ​​within this range are also applicable.

[0038] In some optional embodiments, the total molar ratio of 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, other unlisted values ​​within this range are also applicable.

[0039] In some alternative embodiments, the molar ratio of tetramethylethylenediamine to 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, other unlisted values ​​within this 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, other unlisted values ​​within this range are also applicable.

[0041] In some optional embodiments, the reaction temperature after adjusting the pH of the reaction solution A and stirring is 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. Other unlisted values ​​within this range are also applicable.

[0042] In some optional embodiments, the reaction time after adjusting the pH of the reaction solution A is 3-5 hours, for example, 3 hours, 3.2 hours, 3.4 hours, 3.6 hours, 3.8 hours, 4 hours, 4.2 hours, 4.4 hours, 4.6 hours, 4.8 hours or 5 hours, but not limited to the listed values, other unlisted values ​​within this 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; other unlisted values ​​within this range are also applicable.

[0044] In some optional embodiments, the total molar ratio of 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, other unlisted values ​​within this range are also applicable.

[0045] In some optional embodiments, after adding potassium dihydrogen phosphate solution to reaction solution B, triethanolamine is added until the solution pH is 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, other unlisted values ​​within this range are also applicable.

[0046] In some optional embodiments, the reaction temperature 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, other unlisted values ​​within this range are also applicable.

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

[0048] In some optional embodiments, the solid content of the ion-dynamically bonded 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 unlisted values ​​within this range are also applicable.

[0049] As a preferred technical solution of the present invention, in the preparation step of the antioxidant / corrosion-resistant 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 it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0050] In some optional embodiments, the ethanol solution of methyltriethoxysilane has a mass fraction of 5-10 wt.%, for example, it may 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; other unlisted values ​​within this range are also applicable.

[0051] In some alternative embodiments, the zirconium oxychloride solution is mixed with the ethanol solution of methyltriethoxysilane at a volume ratio of 1:1-2, for example, 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; other unlisted values ​​within this range are also applicable.

[0052] In some optional embodiments, the mass fraction of the ammonia solution 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; other unlisted values ​​within this range are also applicable.

[0053] In some alternative embodiments, the addition of ammonia to adjust the pH to 3-4 can be, for example, 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; other unlisted values ​​within this range are also applicable.

[0054] In some optional embodiments, the solid-liquid mass ratio of the copper powder to 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 is not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0055] In some optional embodiments, the reaction temperature of the reaction liquid D is 30-40°C, for example, it can be 30°C, 31°C, 32°C, 33°C, 34°C, 35°C, 36°C, 37°C, 38°C, 39°C or 40°C, but is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0056] In some optional embodiments, the reaction time of the reaction solution D 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 is not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0057] In some optional embodiments, the amount of 2-mercaptoimidazole fed is 0.1-0.5% of the mass of 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 is not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0058] In some optional embodiments, after the reaction solution D is stirred, 2-mercaptoimidazole is added and stirring is continued for 30-40 min, for example, 30 min, 31 min, 32 min, 33 min, 34 min, 35 min, 36 min, 37 min, 38 min, 39 min or 40 min, but not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0059] Secondly, the present invention provides an electromagnetic shielding waterborne epoxy coating containing graphene copper composite filler, which is prepared according to the above-described preparation method.

[0060] In waterborne epoxy coatings for electromagnetic shielding, graphene and metallic copper are prone to interfacial agglomeration or debonding due to differences in surface chemistry, making it difficult to form a stable and interconnected conductive network. Simultaneously, the interfacial contact between graphene, copper particles, and the epoxy matrix is ​​not tight, and traditional dispersants fail after coating curing, failing to maintain the integrity and stability of the conductive network. Furthermore, copper particles are easily oxidized in waterborne systems, leading to a significant decrease in conductivity and shielding effectiveness. In waterborne coating systems, due to limitations in surface tension and solid content, conductive fillers are also prone to stratification or random distribution, further weakening the continuity of conductive paths and shielding performance. To address these issues, this application designs three synergistic functional additives, including an ion-dynamic bonding micro-interface bridging agent, an antioxidant / corrosion-resistant composite protective copper powder, and a conductive path modifier, to achieve efficient and stable construction of the conductive network.

[0061] The introduction of ion-dynamic bonding micro-interface bridging agents aims to improve the interfacial bonding between graphene, copper particles, and epoxy groups. By dynamically adjusting the filler distribution, the uniformity and stability of the conductive network are ensured. The core components of the bridging agent include N-vinylimidazole, acrylic acid, and glycidyl methacrylate. The imidazole group in N-vinylimidazole contains cationic sites, which can bind to the π-electron cloud of graphene through π-π interactions, and simultaneously bind to the active sites on the copper surface through coordination complexation, thereby achieving multi-point anchoring. The carboxylic acid groups provided by acrylic acid can bind to the hydroxyl or amino groups in the epoxy group through hydrogen bonds, and enhance the interfacial bonding strength between the bridging agent and the filler through electrostatic interactions. The glycidyl methacrylate contains epoxy groups at the end, which can chemically crosslink with the epoxy group during the epoxy coating curing process, thereby achieving permanent fixation of the bridging agent to the matrix. During the flow and curing stages of coating formation, the bridging agent adjusts the distribution of graphene and copper particles according to local stress changes through dynamic bonding interactions such as hydrogen bonds and ionic bonds, ensuring the uniformity of the conductive network. After curing, the dynamic bonds are partially converted into covalent bonds or stronger hydrogen bonds, thereby improving the long-term stability of the conductive network.

[0062] To address the issue of copper particles being easily oxidized or corroded in aqueous systems, this application achieves long-lasting antioxidant and corrosion-resistant properties while preserving the conductivity of the copper particles by introducing a biomimetic organic-inorganic hybrid protective film and a smart-release antioxidant ligand onto the surface of the copper particles. The formation of the organic-inorganic hybrid protective film relies on the synergistic effect of zirconium oxychloride and methyltriethoxysilane. During hydrolysis, zirconium oxychloride generates zirconium hydroxyl groups, which form a three-dimensional cross-linked inorganic framework film through a condensation reaction, effectively isolating oxygen and moisture. The siloxane groups of methyltriethoxysilane hydrolyze and condense under pH 3-4 conditions, synergistically forming an organic-inorganic hybrid film with zirconium oxychloride. The introduction of methyl groups further enhances the hydrophobicity of the film, thereby strengthening its antioxidant properties. Furthermore, 2-mercaptoimidazole, as a smart-release antioxidant ligand, binds its thiol groups to the copper surface through Cu-S bonds, while the imidazole groups further stabilize the binding through coordination. This dual effect effectively prevents copper oxidation. When pH changes or corrosive ions occur in the environment, mercaptoimidazole can be triggered to release, filling localized damaged areas and delaying the spread of corrosion.

[0063] The biomimetic membrane, as a primary protective layer, provides a dense barrier to isolate oxygen and moisture; the antioxidant ligand, as a secondary protective layer, provides dynamic repair function, significantly improving the antioxidant performance of copper particles while retaining their conductivity.

[0064] To address the problems of high surface energy leading to agglomeration of conductive fillers in waterborne coatings, and poor interfacial compatibility with epoxy resin matrices, resulting in discontinuous conductive paths and low electromagnetic shielding effectiveness, this application presents a conductive path modifier. This bridging agent, as an amphiphilic block copolymer, utilizes its polyvinylpyrrolidone hydrophilic segments to provide strong steric stabilization in the aqueous system, enabling uniform and efficient dispersion of graphene and copper powder in the initial mixing stage and inhibiting irreversible agglomeration. Simultaneously, its methacrylic acid and dimethylaminoethyl methacrylate functional segments are anchored to the surface of the conductive filler through various interactions such as hydrogen bonding, acid-base interactions, and coordination bonds. The introduced ferrous ions act as crosslinking centers for ionic bonding, complexing with carboxyl groups in polymer chains adsorbed on different filler particles to form a flexible bridging structure. This ionic bridging effect pre-connects isolated conductive units into a dynamic, primary conductive network at the molecular level. Finally, during the coating application and curing process, as moisture evaporates and the coating shrinks, these two-dimensional sheet-like filler networks, pre-connected by the bridging agent, more easily achieve optimized orientation parallel to the substrate surface under the combined effects of shear force and laminar flow, compared to disordered individual particles. This synergistic effect based on molecular self-assembly promotes the spontaneous formation of a highly interconnected and structurally stable layered conductive network, thereby improving the overall electromagnetic shielding performance of the coating.

[0065] In this application, an ion-dynamic bonding bridging agent is used to improve the interfacial bonding between graphene, copper particles, and epoxy matrix. A biomimetic organic-inorganic hybrid protective film and intelligent release antioxidant ligands are used to protect the antioxidant properties of copper particles. At the same time, a conductive path regulator guides the directional arrangement of conductive fillers, thereby constructing a highly efficient, stable, and durable conductive network and improving the electromagnetic shielding performance of waterborne epoxy coatings.

[0066] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0067] The introduction of ion-dynamically bonded micro-interface bridging agents improves the interfacial bonding between graphene, copper particles, and epoxy groups. The imidazole groups in N-vinylimidazolium achieve multi-point anchoring through π-π interactions and coordination complexation, while the carboxylic acid groups provided by acrylic acid enhance interfacial bonding through hydrogen bonding and electrostatic interactions. The epoxy groups of glycidyl methacrylate achieve permanent fixation by cross-linking with the matrix during curing. During the coating formation stage, the bridging agent regulates filler distribution through dynamic bonds, ensuring the uniformity of the conductive network. After curing, some of these dynamic bonds are converted into more stable covalent bonds or strong hydrogen bonds, further enhancing the long-term stability of the conductive network.

[0068] By introducing a biomimetic organic-inorganic hybrid protective film and a smart-release antioxidant ligand onto the surface of copper particles, the problem of copper's easy oxidation or corrosion in aqueous systems is solved while preserving its conductivity. The organic-inorganic hybrid film is synergistically formed by zirconium oxychloride and methyltriethoxysilane, whose dense structure isolates oxygen and moisture, enhancing antioxidant performance; 2-mercaptoimidazole, as an antioxidant ligand, binds to copper through Cu-S bonds and dynamically releases to repair localized damage under corrosive conditions. This dual-layer protective system significantly improves the antioxidant capacity and long-term stability of copper particles.

[0069] The conductive path modifier introduced in this application is an amphiphilic copolymer that utilizes the steric hindrance effect of hydrophilic segments to achieve efficient and uniform dispersion of conductive fillers, and anchors itself to the filler surface by functional segments. The introduced ferrous ions serve as ionic crosslinking centers, bridging the polymer chains adsorbed on different fillers to pre-construct a flexible conductive network at the molecular level. During the coating curing process, this pre-formed two-dimensional network structure is more easily arranged into a layered structure parallel to the substrate under physical action, ultimately forming a highly permeable and structurally stable conductive pathway, thereby significantly improving the electromagnetic shielding performance of the coating. Detailed Implementation

[0070] The technical solution of the present invention will be described in detail below with reference to specific embodiments. The embodiments described herein are specific implementations of the present invention and are used to illustrate the concept of the present invention; these descriptions are explanatory and exemplary and should not be construed as limiting the implementation of the present invention or the scope of protection of the present invention. In addition to the embodiments described herein, those skilled in the art can also adopt other obvious technical solutions based on the content disclosed in the claims and the specification of this application. These technical solutions include technical solutions that employ any obvious substitutions and modifications made to the embodiments described herein.

[0071] The chemical reagents used in the embodiments and comparative examples of this invention are all commercially available products and have not undergone further purification or processing.

[0072] Example 1

[0073] This embodiment provides an electromagnetic shielding waterborne epoxy coating containing graphene copper composite filler and its preparation method. The preparation method of the electromagnetic shielding waterborne epoxy coating containing graphene copper composite filler specifically includes the following steps:

[0074] S1: Polyvinylpyrrolidone (PVP) is dispersed in deionized water to obtain a PPVP solution, wherein the mass-to-volume ratio of PPVP to deionized water is 12:95 g / mL. Methacrylic acid, dimethylaminoethyl methacrylate, and ammonium persulfate are added to obtain reaction solution E, wherein the mass ratio of PPVP to methacrylic acid, dimethylaminoethyl methacrylate, and ammonium persulfate is 12:8:2:0.2. The reaction is carried out at 70°C for 2 h to obtain a partially grafted amphiphilic block copolymer solution. A 1 wt.% ferrous chloride solution is added to obtain reaction solution F, wherein the amount of ferrous chloride added is 0.8% of the mass of the partially grafted amphiphilic block copolymer solution. The reaction is carried out at 30°C with stirring for 1.7 h. The conductive path modifier with a solid content of 12% is obtained by vacuum distillation.

[0075] S2: Graphene and deionized water are mixed at a mass ratio of 1:27, and an ion-dynamic bonding micro-interface bridging agent is added, wherein the amount of the ion-dynamic bonding micro-interface bridging agent is 4% of the mass of graphene. The mixture is ultrasonically treated at 400W for 20 minutes to obtain a graphene slurry. Antioxidant / corrosion-resistant composite protective copper powder is added, wherein the mass ratio of graphene to antioxidant / corrosion-resistant composite protective copper powder is 1:4. The mixture is stirred and defoamed to obtain a graphene-copper composite slurry.

[0076] S3: Premix epoxy resin emulsion and curing agent Anquamine287 at a mass ratio of 100:50. Add leveling agent BYK-348 at 0.2% of the mass of epoxy resin emulsion and defoamer BYK-024 at 0.26% of the mass of epoxy resin emulsion. Stir evenly to obtain a first mixed coating. Add graphene-copper composite slurry and stir evenly to obtain a second mixed coating, wherein the amount of graphene-copper composite slurry added is 27% of the mass of the first mixed coating. Add conductive path modifier at 2% of the mass of the first mixed coating. Mix evenly to obtain an electromagnetic shielding waterborne epoxy coating containing graphene copper composite filler.

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

[0078] N-vinylimidazole, acrylic acid, and glycidyl methacrylate were dispersed in a deionized water / ethanol mixed solution to obtain a mixed monomer dispersion with a total mass fraction of 18 wt.%, wherein the volume ratio of deionized water to ethanol was 1:1.5, the mass ratio of N-vinylimidazole to acrylic acid was 1:0.4, and the mass ratio of N-vinylimidazole to glycidyl methacrylate was 1:0.2. Ammonium persulfate and tetramethylethylenediamine were added to obtain reaction solution A, wherein the molar ratio of ammonium persulfate to the total mixed monomers was [missing information]. The molar ratio of tetramethylethylenediamine to ammonium persulfate was 1.6:1. After adjusting the pH to 6, the reaction was stirred at 60°C for 3 hours to obtain reaction solution B. A 7.6 wt.% potassium dihydrogen phosphate solution was added, followed by triethanolamine until the pH of the solution reached 7.5 to obtain reaction solution C. The total molar ratio of potassium dihydrogen phosphate to the mixed monomers was 0.1:1. The reaction was stirred at 52°C for 2 hours, filtered, and distilled under reduced pressure to obtain an ion-dynamic bonded micro-interface bridging agent with a solid content of 25%.

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

[0080] A 3 wt.% zirconium oxychloride solution and an 8 wt.% methyltriethoxysilane ethanol solution were prepared. The zirconium oxychloride solution and the 8 wt.% methyltriethoxysilane ethanol solution were mixed at a volume ratio of 1:1. While stirring, 12 wt.% ammonia water was added dropwise to adjust the pH to 3 to obtain an organic-inorganic precursor solution. Copper powder was added to the organic-inorganic precursor solution to obtain reaction solution D, wherein the solid-liquid mass ratio of copper powder to the organic-inorganic precursor solution was 1:7. The reaction was stirred at 30℃ for 1 h. 2-mercaptoimidazole was added and stirring was continued for 30 min to obtain a pretreatment solution, wherein the amount of 2-mercaptoimidazole added was 0.3% of the mass of copper powder. The solution was rotary evaporated and dried to obtain an antioxidant / corrosion-resistant composite protective copper powder.

[0081] Example 2

[0082] This embodiment provides an electromagnetic shielding waterborne epoxy coating containing graphene copper composite filler and its preparation method. The preparation method of the electromagnetic shielding waterborne epoxy coating containing graphene copper composite filler specifically includes the following steps:

[0083] S1: Polyvinylpyrrolidone (PVP) is dispersed in deionized water to obtain a PPVP solution, wherein the mass-to-volume ratio of PPVP to deionized water is 13:97 g / mL. Methacrylic acid, dimethylaminoethyl methacrylate, and ammonium persulfate are added to obtain reaction solution E, wherein the mass ratio of PPVP to methacrylic acid, dimethylaminoethyl methacrylate, and ammonium persulfate is 13:7:1:0.1. The reaction is carried out at 75°C for 3 h to obtain a partially grafted amphiphilic block copolymer solution. A 1.6 wt.% ferrous chloride solution is added to obtain reaction solution F, wherein the amount of ferrous chloride added is 0.7% of the mass of the partially grafted amphiphilic block copolymer solution. The reaction is carried out at 35°C with stirring for 1 h, and vacuum distillation is performed to obtain a conductive path modifier with a solid content of 10%.

[0084] S2: Graphene and deionized water are mixed at a mass ratio of 1:24, and an ion-dynamic bonding micro-interface bridging agent is added, wherein the amount of the ion-dynamic bonding micro-interface bridging agent is 2% of the mass of graphene. The mixture is ultrasonically treated at 450W for 22 minutes to obtain a graphene slurry. Antioxidant / corrosion-resistant composite protective copper powder is added, wherein the mass ratio of graphene to antioxidant / corrosion-resistant composite protective copper powder is 1:4.5. The mixture is stirred and defoamed to obtain a graphene-copper composite slurry.

[0085] S3: Premix epoxy resin emulsion and curing agent Anquamine401 at a mass ratio of 100:55. Add leveling agent BYK-348 at 0.25% of the mass of epoxy resin emulsion and defoamer BYK-024 at 0.1% of the mass of epoxy resin emulsion. Stir evenly to obtain a first mixed coating. Add graphene-copper composite slurry and stir evenly to obtain a second mixed coating, wherein the amount of graphene-copper composite slurry added is 20% of the mass of the first mixed coating. Add conductive path modifier at 2.4% of the mass of the first mixed coating. Mix evenly to obtain an electromagnetic shielding waterborne epoxy coating containing graphene copper composite filler.

[0086] The preparation steps of the ion-dynamic bonded 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 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, and the mass ratio of N-vinylimidazole to glycidyl methacrylate was 1:0.3. Ammonium persulfate and tetramethylethylenediamine were added to obtain reaction solution A, wherein the molar ratio of ammonium persulfate to the total mixed monomers was 0. The molar ratio of tetramethylethylenediamine to ammonium persulfate was 1.7:1. After adjusting the pH to 6.5, the mixture was stirred at 68°C for 4.5 hours to obtain reaction solution B. A 5 wt.% potassium dihydrogen phosphate solution was added, followed by triethanolamine until the pH of the solution reached 6 to obtain reaction solution C. The total molar ratio of potassium dihydrogen phosphate to the mixed monomers was 0.12:1. The mixture was stirred at 53°C for 2.5 hours, filtered, and distilled under reduced pressure to obtain an ion-dynamic bonded 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 4 wt.% zirconium oxychloride solution and a 6 wt.% methyltriethoxysilane ethanol solution were prepared. The zirconium oxychloride solution and the 7 wt.% methyltriethoxysilane ethanol solution were mixed at a volume ratio of 1:1.5. While stirring, 14 wt.% ammonia water was added dropwise 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 reaction solution D, wherein the solid-liquid mass ratio of copper powder to the organic-inorganic precursor solution was 1:6. The reaction was stirred at 35℃ for 1.2 h. 2-mercaptoimidazole was added and stirring was continued for 35 min to obtain a pretreatment solution, wherein the amount of 2-mercaptoimidazole added was 0.4% of the mass of copper powder. The solution was rotary evaporated and dried to obtain an antioxidant / corrosion-resistant composite protective copper powder.

[0090] Example 3

[0091] This embodiment provides an electromagnetic shielding waterborne epoxy coating containing graphene copper composite filler and its preparation method. The preparation method of the electromagnetic shielding waterborne epoxy coating containing graphene copper composite filler specifically includes the following steps:

[0092] S1: Polyvinylpyrrolidone (PVP) is dispersed in deionized water to obtain a PPVP solution, wherein the mass-to-volume ratio of PPVP to deionized water is 10:90 g / mL. Methacrylic acid, dimethylaminoethyl methacrylate, and ammonium persulfate are added to obtain reaction solution E, wherein the mass ratio of PPVP to methacrylic acid, dimethylaminoethyl methacrylate, and ammonium persulfate is 10:5:2.5:0.3. The reaction is carried out at 77°C for 3.5 h to obtain a partially grafted amphiphilic block copolymer solution. A 1.8 wt.% ferrous chloride solution is added to obtain reaction solution F, wherein the amount of ferrous chloride added is 0.5% of the mass of the partially grafted amphiphilic block copolymer solution. The reaction is carried out at 38°C with stirring for 1.5 h. The conductive path modifier with a solid content of 13% is obtained by vacuum distillation.

[0093] S2: Graphene and deionized water are mixed at a mass ratio of 1:20, and an ion-dynamic bonding micro-interface bridging agent is added, wherein the amount of the ion-dynamic bonding micro-interface bridging agent is 5% of the mass of graphene. The mixture is ultrasonically treated at 300W for 15 minutes to obtain a graphene slurry. Antioxidant / corrosion-resistant composite protective copper powder is added, wherein the mass ratio of graphene to antioxidant / corrosion-resistant composite protective copper powder is 1:3. The mixture is stirred and defoamed to obtain a graphene-copper composite slurry.

[0094] S3: Premix epoxy resin emulsion and curing agent Anquamine287 at a mass ratio of 100:40. Add leveling agent BYK-348 at 0.1% of the mass of epoxy resin emulsion and defoamer BYK-024 at 0.2% of the mass of epoxy resin emulsion, and stir evenly to obtain a first mixed coating. Add graphene-copper composite slurry and stir to disperse evenly to obtain a second mixed coating, wherein the amount of graphene-copper composite slurry added is 25% of the mass of the first mixed coating. Add conductive path modifier at 1% of the mass of the first mixed coating, and mix evenly to obtain an electromagnetic shielding waterborne epoxy coating containing graphene copper composite filler.

[0095] The preparation steps of the ion-dynamic bonded 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 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 reaction solution A, wherein the total molar ratio of ammonium persulfate to the mixed monomers was... The ratio of tetramethylethylenediamine to ammonium persulfate was 0.018:1, and the molar ratio of tetramethylethylenediamine to ammonium persulfate was 1:1. After adjusting the pH to 5, the reaction was stirred at 65℃ for 5 hours to obtain reaction solution B. A 7 wt.% potassium dihydrogen phosphate solution was added, followed by triethanolamine until the pH of the solution was 7 to obtain reaction solution C. The total molar ratio of potassium dihydrogen phosphate to the mixed monomers was 0.05:1. The reaction was stirred at 50℃ for 2.8 hours, filtered, and distilled under reduced pressure to obtain an ion-dynamic bonded 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.% methyltriethoxysilane ethanol solution were prepared. The zirconium oxychloride solution and the 5 wt.% methyltriethoxysilane ethanol solution were mixed at a volume ratio of 1:1.7. While stirring, 10 wt.% ammonia water was added dropwise 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 reaction solution D, wherein the solid-liquid mass ratio of copper powder to the organic-inorganic precursor solution was 1:5. The reaction was stirred at 38℃ for 1.3 h. 2-mercaptoimidazole was added and stirring was continued for 38 min to obtain a pretreatment solution, wherein the amount of 2-mercaptoimidazole added was 0.1% of the mass of copper powder. The solution was rotary evaporated and dried to obtain an antioxidant / corrosion-resistant composite protective copper powder.

[0099] Example 4

[0100] This embodiment provides an electromagnetic shielding waterborne epoxy coating containing graphene copper composite filler and its preparation method. The preparation method of the electromagnetic shielding waterborne epoxy coating containing graphene copper composite filler specifically includes the following steps:

[0101] S1: Polyvinylpyrrolidone (PVP) is dispersed in deionized water to obtain a PPVP solution, wherein the mass-to-volume ratio of PPVP to deionized water is 15:100 g / mL. Methacrylic acid, dimethylaminoethyl methacrylate (DMCA), and ammonium persulfate are added to obtain reaction solution E, wherein the mass ratio of PPVP to methacrylic acid, DMCA, and ammonium persulfate is 15:10:3:0.26. The reaction is carried out at 80°C for 4 h to obtain a partially grafted amphiphilic block copolymer solution. A 2 wt.% ferrous chloride solution is added to obtain reaction solution F, wherein the amount of ferrous chloride added is 1% of the mass of the partially grafted amphiphilic block copolymer solution. The reaction is carried out at 40°C with stirring for 2 h, and vacuum distillation is performed to obtain a conductive path modifier with a solid content of 15%.

[0102] S2: Graphene and deionized water are mixed at a mass ratio of 1:30, and an ion-dynamic bonding micro-interface bridging agent is added, wherein the amount of the ion-dynamic bonding micro-interface bridging agent is 3% of the mass of graphene. The mixture is ultrasonically treated at 500W for 30 minutes to obtain a graphene slurry. Antioxidant / corrosion-resistant composite protective copper powder is added, wherein the mass ratio of graphene to antioxidant / corrosion-resistant composite protective copper powder is 1:5. The mixture is stirred and defoamed to obtain a graphene-copper composite slurry.

[0103] S3: Premix epoxy resin emulsion and curing agent Anquamine287 at a mass ratio of 100:60. Add leveling agent BYK-348 and defoamer BYK-024 at a mass ratio of 0.3% of the epoxy resin emulsion. Stir evenly to obtain a first mixed coating. Add graphene-copper composite slurry and stir evenly to obtain a second mixed coating, wherein the amount of graphene-copper composite slurry added is 30% of the mass of the first mixed coating. Add conductive path modifier at a mass ratio of 3% of the first mixed coating. Mix evenly to obtain an electromagnetic shielding waterborne epoxy coating containing graphene copper composite filler.

[0104] The preparation steps of the ion-dynamic bonded 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 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, and the mass ratio of N-vinylimidazole to glycidyl methacrylate was 1:0.4. Ammonium persulfate and tetramethylethylenediamine were added to obtain reaction solution A, wherein the molar ratio of ammonium persulfate to the total mixed monomers was 0.02:1, and the molar ratio of tetramethylethylenediamine to ammonium persulfate was 2:1. After adjusting the pH to 7, the reaction was stirred at 70℃ for 4.8 h to obtain reaction solution B. After adding 8 wt.% potassium dihydrogen phosphate solution, triethanolamine was added until the pH of the solution was 8 to obtain reaction solution C, wherein the molar ratio of potassium dihydrogen phosphate to the total mixed monomers was 0.15:1. The reaction was stirred at 55℃ for 3 h, filtered, and distilled under reduced pressure to obtain an ion-dynamic bonded 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.% methyltriethoxysilane ethanol solution were prepared. The zirconium oxychloride solution and the 10 wt.% methyltriethoxysilane ethanol solution were mixed at a volume ratio of 1:2. While stirring, 15 wt.% ammonia water was added dropwise 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 reaction solution D, wherein the solid-liquid mass ratio of copper powder to the organic-inorganic precursor solution was 1:8. The reaction was stirred at 40℃ for 1.5 h. 2-mercaptoimidazole was added and stirring was continued for 40 min to obtain a pretreatment solution, wherein the amount of 2-mercaptoimidazole added was 0.5% of the mass of copper powder. The solution was rotary evaporated and dried 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. The difference from Example 1 is that no ion-dynamic bonding micro-interface bridging agent is added in S2. Graphene is directly mixed with antioxidant / corrosion-resistant composite protective copper powder. Other operating steps and process parameters are exactly the same as in Example 1.

[0110] Comparative Example 2

[0111] This comparative example provides an electromagnetic shielding waterborne epoxy coating containing graphene copper composite filler. The difference from Example 1 is that ordinary copper powder without anti-oxidation / anti-corrosion composite protection is used. Other operating steps and process parameters are exactly the same as in Example 1.

[0112] Comparative Example 3

[0113] This comparative example provides an electromagnetic shielding waterborne epoxy coating containing graphene copper composite filler. The difference from Example 1 is that methyltriethoxysilane is not added in the preparation steps of the antioxidant / corrosion-resistant composite protective copper powder. Other operating steps and process parameters are exactly the same as in Example 1.

[0114] Comparative Example 4

[0115] This comparative example provides an electromagnetic shielding waterborne epoxy coating containing graphene copper composite filler. The difference from Example 1 is that no conductive path modifier is used; the conductive filler is dispersed only by mechanical stirring. Other operating steps and process parameters are exactly the same as in Example 1.

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

[0117] The electromagnetic shielding effectiveness of the coating was tested according to GB / T 30142-2013.

[0118] The impact strength of the coating was tested according to GB / T 1732-2020.

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

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

[0121] Heat resistance: The coating was placed in a forced-air drying oven and treated at 300℃ for 24 hours. Then, the electromagnetic shielding effectiveness of the coating after high-temperature treatment was tested in accordance with GB / T 30142-2013.

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

[0123] Table 1: Electromagnetic shielding effectiveness of waterborne epoxy coatings containing graphene copper composite fillers in Examples 1-4 and Comparative Examples 1-4

[0124] Electromagnetic shielding effectiveness dB Electromagnetic shielding effectiveness dB after heat resistance Impact 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] The test results from Example 1 and Comparative Example 1 show that the lack of ion-dynamic bonding micro-interface bridging agents leads to a decrease in the dispersibility and interfacial bonding of graphene and copper powder, uneven distribution of fillers in the matrix, reduced construction efficiency of conductive networks, and a significant decrease in shielding effectiveness. The bridging agent's function of converting dynamic bonds into stable bonds after curing is lost, making the conductive network more susceptible to damage at high temperatures due to thermal expansion and contraction or matrix softening, thus reducing shielding effectiveness. The lack of bridging agents reduces the interfacial bonding between fillers and the matrix, making fillers prone to detachment under impact loads, resulting in decreased impact resistance. Uneven filler distribution and poor interfacial contact weaken the continuity of conductive paths, leading to a decrease in overall conductivity. The lack of chemical cross-linking and multi-point anchoring effects of bridging agents reduces interfacial bonding strength and adhesion.

[0126] The test results from Example 1 and Comparative Example 2 show that unprotected copper powder is easily oxidized in an aqueous system. The high resistivity of the oxide layer significantly reduces the conductivity of the copper powder, damages the conductive network, and leads to a significant decrease in electromagnetic shielding effectiveness. Further oxidation at high temperatures forms a thicker oxide layer, severely damaging the conductive network and drastically reducing shielding effectiveness. Although the copper powder oxidizes, its particle morphology is not significantly affected, thus having little impact on mechanical properties. However, due to reduced interfacial adhesion, impact strength decreases slightly. The high resistivity of the oxide layer on the copper powder surface significantly increases the contact resistance between fillers, resulting in a marked deterioration in conductivity. The oxidation of copper powder primarily affects conductivity, with less impact on the adhesion between the coating and the substrate.

[0127] The test results from Example 1 and Comparative Example 3 show that, lacking methyltriethoxysilane, the protective film consists only of an inorganic framework formed by zirconium oxychloride, resulting in a relatively simple structure and insufficient hydrophobicity. This leads to a decrease in the antioxidant properties of copper powder, damage to the conductive network, and a reduction in shielding effectiveness. The single inorganic film has limited inhibitory effect on high-temperature oxidation, and copper powder oxidation intensifies under high-temperature conditions, further reducing shielding effectiveness. The defects of the protective film have a limited impact on interfacial adhesion, thus having a relatively small impact on the impact resistance of the coating. The reduced hydrophobicity and density of the protective film worsen the contact quality between fillers and reduce the continuity of the conductive path. The protective film mainly acts on the surface of copper powder and has a relatively small impact on the adhesion of the substrate.

[0128] The test results from Example 1 and Comparative Example 4 show that, without the dispersion and bridging effect of the conductive path modifier, graphene and copper powder are easily agglomerated and distributed disorderly in the matrix, significantly reducing the construction efficiency of the conductive network and resulting in a decrease in shielding effectiveness. This disordered conductive network, formed solely by physical bonding, is more prone to breakage at high temperatures due to thermal expansion and contraction or matrix softening, further reducing shielding effectiveness. Mechanical stirring and dispersion have little impact on the mechanical properties of the coating. The contact resistance between agglomerated and disordered fillers is high, and the conductive path is discontinuous, leading to an increase in volume resistivity. The absence of the conductive path modifier has little impact on the adhesion between the coating and the substrate.

[0129] The above description is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention fall within the protection and disclosure scope of the present invention.

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 the first mixed coating; add graphene-copper composite slurry and stir to disperse evenly to obtain the second mixed coating; add conductive path modifier and mix evenly to obtain an electromagnetic shielding waterborne epoxy coating containing graphene copper composite filler.

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):(90-100) g / 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, 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 mixture was stirred to obtain reaction solution B. Potassium dihydrogen phosphate solution was added, followed by triethanolamine to obtain reaction solution C. The mixture was stirred to obtain reaction solution C. After filtration and vacuum distillation, an ion-dynamic bonded micro-interface bridging agent was obtained.

6. The method for preparing the electromagnetic shielding waterborne epoxy coating containing graphene copper composite filler according to claim 5, 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.

7. The method for preparing the electromagnetic shielding waterborne epoxy coating containing graphene copper composite filler according to claim 5, 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%.

8. The method for preparing the electromagnetic shielding waterborne epoxy coating containing graphene copper composite filler according to claim 1, characterized in that, 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.

9. The method for preparing the electromagnetic shielding waterborne epoxy coating containing graphene copper composite filler according to claim 8, 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.

10. An electromagnetic shielding waterborne epoxy coating containing graphene copper composite filler, characterized in that, It is prepared according to any one of claims 1-9.