A method for preparing rare-earth modified graphene coatings for electromagnetic wave shielding and their application.

Abstract

This invention belongs to the field of polymer coating preparation technology, and discloses a method for preparing and applying a rare-earth modified graphene coating for electromagnetic wave shielding. First, rare-earth functionalized graphene is prepared using an electrochemical exfoliation method. Then, waterborne polyurethane resin is synthesized. Next, the rare-earth functionalized graphene, waterborne polyurethane resin, and water are uniformly mixed, and leveling agents, defoamers, and thickeners are added. Finally, the mixture is passed through a nylon mesh to prepare the rare-earth modified graphene coating. This invention achieves the following beneficial effects: coating an aluminum substrate with the rare-earth modified graphene coating of this invention imparts high battery shielding efficiency to the substrate, with an electromagnetic shielding efficiency greater than 40 dB in the 8–12 GHz (X-band) range.

Description

Technical Field

[0001] This invention relates to the field of polymer coating preparation technology, specifically to a method for preparing and applying a rare earth-modified graphene coating for electromagnetic wave shielding. Background Technology

[0002] With the rapid development of science and technology, various electronic devices have been successfully applied to people's lives and work. However, electronic devices generate electromagnetic radiation during operation, which can seriously affect people's health and lead to carcinogenic diseases. Furthermore, electromagnetic interference between devices can cause signal interception and data loss, severely impacting the performance and normal operation of electronic devices. Especially with the development of the Internet of Things, autonomous driving, and wearable devices, electronic devices are becoming increasingly complex, smaller, and more precise. To ensure the normal operation of these highly integrated, high-power electronic devices, electromagnetic interference shielding is crucial. Therefore, electromagnetic shielding materials have emerged. These materials are used to create shielding bodies that surround interference sources in electronic components, circuits, assemblies, cables, and even the entire electronic system, preventing the outward spread of interfering electromagnetic fields or external interference. Common electromagnetic shielding materials include conductive adhesives, conductive cloths, conductive foams, conductive tapes, and absorbing materials. Among these, absorbing materials are an important type of electromagnetic shielding material. They are applied as a coating to electronic components or assemblies and the system casing to shield electromagnetic radiation and can be used in civilian or military electronic devices.

[0003] This invention utilizes a self-developed rare-earth modified graphene coating, applied to the electromagnetic shielding coating of electronic components or assemblies and system shells in electronic devices. The rare-earth nano-oxides contained in the coating exhibit localized surface plasmon resonance (LSPR) effect. Rare-earth functionalized graphene prepared by electrochemical exfoliation is uniformly dispersed in water-based polyurethane resin to form a long-lasting and stable rare-earth nano-thermal insulating agent, effectively shielding against ultraviolet, infrared, and microwave radiation, possessing numerous advantages such as excellent thermal insulation, transparency, and weather resistance. If used as a stealth coating for electronic equipment in weaponry, it can also prevent targets from being detected by radar. (See "Li Sufang, Chen Zongzhang. Nano-graphene-based composite microwave absorbing materials and their preparation method [P]. Chinese Patent: CN")

[0004] "101550003A, 2009-4-22.", "Xing Honglong, Yin Qing, Liu Zhenfeng, Wang Lei. A microwave absorbing material composed of reduced graphene oxide and nano-cerium oxide and its preparation method [P]. Chinese Patent: CN 105255446 A, 2015-11-06." In the prior art, rare earth functionalized graphene is prepared by hydrothermal methods, electrodeposition methods, etc., while the preparation of this material by electrochemical exfoliation has not been reported. Another effective component, graphene, with its ultra-high specific surface area, is itself an excellent microwave absorbing material, and when combined with rare earth nano-oxides, it achieves a good electromagnetic shielding effect for equipment. Summary of the Invention

[0005] To achieve electromagnetic wave shielding, this invention uniformly disperses rare-earth functionalized graphene prepared by electrochemical exfoliation into water-based polyurethane resin to prepare a rare-earth modified graphene coating. This coating, when applied to electronic components, circuits, assemblies, and system casings of electronic devices, can shield against infrared and other electromagnetic radiation without hindering the normal operation of the electronic devices.

[0006] To achieve the above objectives, the technical solution of the present invention is as follows: A method for preparing rare earth modified graphene coating for electromagnetic wave shielding, the specific preparation steps of which are as follows:

[0007] Step (1): Preparation of rare earth functionalized graphene:

[0008] Step (a) Electrochemical exfoliation to prepare rare earth functionalized graphene: Graphite paper is used as the anode and platinum sheet as the cathode. The electrolyte system is a mixed solution of 0.5-1.5 mol / L H2SO4, 0.1-1 mol / L rare earth sulfate and 0.1-0.4 mol / L KNO3. The graphite paper is pre-immersed in the above mixed solution for 15-20 min, and then pre-electrolyzed at 3-5 V for 20-40 min. The voltage is then increased to 8-10 V until the graphene is completely exfoliated to obtain a primary product suspension.

[0009] Step (b) Vacuum filtration: The above primary product suspension is subjected to vacuum filtration 5 to 6 times to obtain a secondary product suspension.

[0010] Step (c) Ultrasonic treatment: The above-mentioned secondary product suspension is ultrasonically treated to obtain a tertiary product suspension.

[0011] Step (d) Freeze-drying: The suspension of the three products obtained in step (c) above is freeze-dried for 46-72 hours. Then, it is pulverized by a pulverizer and passed through a 60-mesh sieve to obtain rare earth functionalized graphene.

[0012] Step (2): Preparation of waterborne polyurethane resin:

[0013] Place 1–3 parts of 2,2-dimethylolpropionic acid (DMPA) in a vacuum drying oven and dry at 60–80°C for 30–50 min. Dissolve it in 5–10 parts of N-methylpyrrolidone using a water bath stirrer. Then, place 1–3 parts of polytetrahydrofuran (PTMEG), 1–3 parts of isophorone diisocyanate (IPDI), and the dissolved 2,2-dimethylolpropionic acid into a three-necked flask, purge with nitrogen, and incubate in a water bath at 70–90°C. The reaction is carried out at ℃ for 3-6 hours with a stirring speed of 300-400 r / pm. The temperature is then lowered to 30-40℃, and 1-3 parts of triethylamine (TEA) are added for neutralization reaction, with a reaction time of 30-50 minutes. The stirring speed is then increased to 600-900 r / pm, and 10-20 parts of deionized water are added. Then, 0.5-1 parts of ethylenediamine (EDA) are added for chain extension reaction, and the reaction is carried out for 1-3 hours. Finally, the waterborne polyurethane resin is obtained after passing through a nylon mesh.

[0014] Step (3): Preparation of rare earth modified graphene coating:

[0015] Disperse 0.5–1 part rare earth functionalized graphene, 1–3 parts waterborne polyurethane resin, and 20–50 parts water using a high-speed disperser at 5000–6000 r / min for 30–50 min. After standing for 10–30 min, add 0.1–0.5 parts leveling agent, 0.1–0.5 parts defoamer, and 0.1–0.5 parts thickener in sequence, and continue dispersing and stirring for 30–60 min to obtain rare earth modified graphene coating.

[0016] The electrolyte system is a mixed solution of 1 mol / L H2SO4, 0.5 mol / L rare earth sulfate, and 0.2 mol / L KNO3.

[0017] The rare earth sulfates in the electrolyte are rare earth elements selected from any one of cerium, lanthanum, praseodymium, neodymium, promethium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, lutetium, scandium, and yttrium.

[0018] The ultrasonic treatment process parameters are: ultrasonic time of 30-60 min and frequency of 40-90 Hz.

[0019] The leveling agent is any one of acrylates, cellulose acetate, nitrocellulose, diphenylpolysiloxane, methylphenylpolysiloxane, organic-modified polysiloxane, polyether organosilicon, or organofluorine compounds.

[0020] The defoamer is any one of silicone oil, polyether, higher alcohol, mineral oil, vegetable oil, nonylphenol polyoxyethylene ether, soap salt, OP series emulsifier, Tween series emulsifier, and Span series emulsifier.

[0021] The thickener is any one of the following: organic bentonite, sodium bentonite, diatomaceous earth, silica gel, cellulose ethers, starch, gelatin, sodium alginate, casein, guar gum, chitosan, gum arabic, xanthan gum, soybean protein gum, natural rubber, lanolin, and agar.

[0022] An application of rare earth modified graphene coating for electromagnetic wave shielding, used for electromagnetic wave shielding of electronic devices or as a stealth coating.

[0023] The principle of rare earth functionalized graphene preparation of the present invention is as follows: Under the action of electric field, sulfate anions are intercalated into the anode graphite layer and exfoliated to form graphene, while rare earth cations migrate to the cathode platinum electrode surface and form rare earth metal oxides on the cathode surface under the action of KNO3 catalyst. Subsequently, the metal oxides are desorbed under the action of electric field and combined with graphene to form rare earth functionalized graphene.

[0024] The beneficial effects of this invention are as follows: Coating the rare-earth modified graphene coating of this invention onto an aluminum carrier endows the carrier with high battery shielding efficiency, with an electromagnetic shielding efficiency greater than 40dB in the 8-12GHz (X-band) range. The rare-earth functionalized graphene in the coating of this invention has a simple and environmentally friendly preparation process. Compared with laboratory synthesis methods such as hydrothermal synthesis, it facilitates large-scale production of the product and meets the production needs of raw materials in the coating industry. Attached Figure Description

[0025] Figure 1 This is a SEM image of the rare-earth functionalized graphene of the present invention.

[0026] Figure 2 Raman diagram of the rare-earth functionalized graphene of the present invention;

[0027] Figure 3 Comparison of battery shielding effectiveness test results between Examples 1-3 and Comparative Examples 1-2. Specific Implementation

[0028] The present invention will be further described below with reference to specific embodiments.

[0029] Example 1:

[0030] A method for preparing a rare-earth modified graphene coating for electromagnetic wave shielding, the specific preparation steps are as follows:

[0031] (1) Preparation of rare earth functionalized graphene:

[0032] (a) Electrochemical exfoliation to prepare rare earth functionalized graphene: graphite paper was used as the anode and platinum sheet as the cathode. The electrolyte system was a mixed solution of 0.5 mol / L H2SO4, 0.1 mol / L Ce(SO4)2 and 0.1 mol / L KNO3. The graphite paper was pre-immersed in the above mixed solution for 15 min, and then pre-electrolyzed at 3V for 20 min. The voltage was then increased to 8V until the graphene was completely exfoliated to obtain a primary product suspension.

[0033] (b) Vacuum filtration: The above primary product suspension is subjected to five vacuum filtration processes using a circulating filter to obtain a secondary product suspension.

[0034] (c) Ultrasonic treatment: The above secondary product suspension is ultrasonically treated using an ultrasonic cleaner to obtain a tertiary product suspension.

[0035] (d) Freeze-drying: The suspension of the three products obtained in step (c) above is freeze-dried for 46 hours, and then pulverized by a pulverizer and passed through a 60-mesh sieve to obtain rare earth functionalized graphene.

[0036] (2) Preparation of waterborne polyurethane resin:

[0037] One part of 2,2-dimethylolpropionic acid (DMPA) was placed in a vacuum drying oven and dried at 60°C for 30 min. Then, it was dissolved in 5 parts of N-methylpyrrolidone using a water bath stirrer. Subsequently, one part of polytetrahydrofuran (PTMEG), one part of isophorone diisocyanate (IPDI), and the dissolved 2,2-dimethylolpropionic acid were placed in a three-necked flask, nitrogen gas was introduced, and the mixture was reacted in a water bath at 70–90°C for 3 h with a stirring speed of 300 rpm. The temperature was then lowered to 30°C, and one part of triethylamine (TEA) was added for neutralization reaction, with a reaction time of 30 min. Next, the stirring speed was increased to 600 rpm, and 10 parts of deionized water were added, followed by 0.5 parts of ethylenediamine (EDA) for chain extension reaction, which was carried out for 1 h. Finally, the mixture was passed through a 400-mesh nylon mesh to obtain a waterborne polyurethane resin.

[0038] (3) Preparation of rare earth modified graphene coatings

[0039] Disperse 0.5 parts of rare earth functionalized graphene, 1 part of waterborne polyurethane resin and 20 parts of water using a high-speed disperser at 5000 r / min for 30 min. After standing for 10 min, add 0.1 parts of leveling agent, 0.1 parts of defoamer and 0.1 parts of thickener in sequence, and continue to disperse and stir for 30 min to obtain rare earth modified graphene coating.

[0040] The ultrasonic treatment process parameters are an ultrasonic time of 30 min and a frequency of 40 Hz.

[0041] The leveling agent is any one of acrylates, cellulose acetate, nitrocellulose, diphenylpolysiloxane, methylphenylpolysiloxane, organic-modified polysiloxane, polyether organosilicon, or organofluorine compounds.

[0042] The defoamer is any one of silicone oil, polyether, higher alcohol, mineral oil, vegetable oil, nonylphenol polyoxyethylene ether, soap salt, OP series emulsifier, Tween series emulsifier, and Span series emulsifier.

[0043] The thickener is any one of the following: organic bentonite, sodium bentonite, diatomaceous earth, silica gel, cellulose ethers, starch, gelatin, sodium alginate, casein, guar gum, chitosan, gum arabic, xanthan gum, soybean protein gum, natural rubber, lanolin, and agar.

[0044] An application of a rare-earth modified graphene coating for electromagnetic wave shielding, wherein the rare-earth modified graphene coating for electromagnetic wave shielding is used for electromagnetic wave shielding of electronic devices or as a stealth coating.

[0045] The electromagnetic shielding effectiveness of the coating was tested using an Agilent E8363 network analyzer in the 8–12 GHz (X-band) range. First, the coating was applied to an aluminum sheet using a scraping method. Then, the coated aluminum sheet was placed in a drying oven and dried at 180°C for 12 hours. Finally, the electromagnetic shielding effectiveness was tested. The electromagnetic wave shielding effectiveness test results showed that the electromagnetic wave shielding effectiveness of Example 1 was 41.2 dB.

[0046] Example 2:

[0047] A method for preparing a rare-earth modified graphene coating for electromagnetic wave shielding, the specific preparation steps are as follows:

[0048] (1) Preparation of rare earth functionalized graphene:

[0049] (a) Electrochemical exfoliation to prepare rare earth functionalized graphene: graphite paper was used as the anode and platinum sheet as the cathode. The electrolyte system was a mixed solution of 1 mol / L H2SO4, 0.5 mol / L La2(SO4)3 and 0.2 mol / L KNO3. The graphite paper was pre-immersed in the above mixed solution for 18 min, and then pre-electrolyzed at 4 V for 30 min. The voltage was then increased to 9 V until the graphene was completely exfoliated to obtain a primary product suspension.

[0050] (b) Vacuum filtration: The above primary product suspension is subjected to six vacuum filtration processes using a circulating filter to obtain a secondary product suspension.

[0051] (c) Ultrasonic treatment: The above secondary product suspension is ultrasonically treated using an ultrasonic cleaner to obtain a tertiary product suspension.

[0052] (d) Freeze-drying: The suspension of the three products obtained in step (c) above is freeze-dried for 59 hours. Then, it is pulverized by a pulverizer and passed through a 60-mesh sieve to obtain rare earth functionalized graphene.

[0053] (2) Preparation of waterborne polyurethane resin:

[0054] Two parts of 2,2-dimethylolpropionic acid (DMPA) were placed in a vacuum drying oven and dried at 70°C for 40 min. Then, DMPA was dissolved in 5–10 parts of N-methylpyrrolidone using a water bath stirrer. Subsequently, 1.5 parts of polytetrahydrofuran (PTMEG), 1.5 parts of isophorone diisocyanate (IPDI), and the dissolved DMPA were placed in a three-necked flask. Nitrogen gas was introduced, and the mixture was reacted in a water bath at 70–90°C for 3–6 h with a stirring speed of 300–400 rpm. The temperature was then lowered to 30–40°C, and two parts of triethylamine (TEA) were added for neutralization reaction, with a reaction time of 40 min. Next, the stirring speed was increased to 700 rpm, and 15 parts of deionized water were added, followed by 0.75 parts of ethylenediamine (EDA) for chain extension reaction, which was carried out for 2 h. Finally, the mixture was passed through a 400-mesh nylon mesh to obtain a waterborne polyurethane resin.

[0055] (3) Preparation of rare earth modified graphene coatings

[0056] 0.75 parts of rare earth functionalized graphene, 2 parts of waterborne polyurethane resin and 35 parts of water are dispersed in a high-speed disperser at 5500 r / min for 40 min. After standing for 20 min, 0.3 parts of leveling agent, 0.3 parts of defoamer and 0.3 parts of thickener are added in sequence, and dispersion and stirring are continued for 45 min to obtain rare earth modified graphene coating.

[0057] The ultrasonic treatment process parameters are an ultrasonic time of 45 min and a frequency of 60 Hz.

[0058] The leveling agent is any one of acrylates, cellulose acetate, nitrocellulose, diphenylpolysiloxane, methylphenylpolysiloxane, organic-modified polysiloxane, polyether organosilicon, or organofluorine compounds.

[0059] The defoamer is any one of silicone oil, polyether, higher alcohol, mineral oil, vegetable oil, nonylphenol polyoxyethylene ether, soap salt, OP series emulsifier, Tween series emulsifier, and Span series emulsifier.

[0060] The thickener is any one of the following: organic bentonite, sodium bentonite, diatomaceous earth, silica gel, cellulose ethers, starch, gelatin, sodium alginate, casein, guar gum, chitosan, gum arabic, xanthan gum, soybean protein gum, natural rubber, lanolin, and agar.

[0061] An application of a rare-earth modified graphene coating for electromagnetic wave shielding, wherein the rare-earth modified graphene coating for electromagnetic wave shielding is used for electromagnetic wave shielding of electronic devices or as a stealth coating.

[0062] The electromagnetic wave shielding effectiveness test results show that the electromagnetic wave shielding effectiveness of the best embodiment 2 is 49.7dB.

[0063] Example 3:

[0064] A method for preparing rare earth modified graphene coating for electromagnetic wave shielding, the specific preparation steps are as follows: (1) Preparation of rare earth functionalized graphene:

[0065] (a) Electrochemical exfoliation to prepare rare earth functionalized graphene: graphite paper was used as the anode and platinum sheet as the cathode. The electrolyte system was a mixed solution of 1.5 mol / L H2SO4, 1 mol / L Pr2(SO4)3 and 0.4 mol / L KNO3. The graphite paper was pre-immersed in the above mixed solution for 20 min, and then pre-electrolyzed at 5 V for 40 min. The voltage was then increased to 10 V until the graphene was completely exfoliated, and a primary product suspension was obtained.

[0066] (b) Vacuum filtration: The above primary product suspension is subjected to six vacuum filtration processes using a circulating filter to obtain a secondary product suspension.

[0067] (c) Ultrasonic treatment: The above secondary product suspension is ultrasonically treated using an ultrasonic cleaner to obtain a tertiary product suspension.

[0068] (d) Freeze-drying: The suspension of the three products obtained in step (c) above is freeze-dried for 72 hours. Then, it is pulverized by a pulverizer and passed through a 60-mesh sieve to obtain rare earth functionalized graphene.

[0069] (2) Preparation of waterborne polyurethane resin:

[0070] Three parts of 2,2-dimethylolpropionic acid (DMPA) were placed in a vacuum drying oven and dried at 80°C for 50 min. Then, DMPA was dissolved in 10 parts of N-methylpyrrolidone using a water bath stirrer. Subsequently, three parts of polytetrahydrofuran (PTMEG), three parts of isophorone diisocyanate (IPDI), and the dissolved DMPA were placed in a three-necked flask. Nitrogen gas was introduced, and the mixture was reacted in a water bath at 90°C for 6 h with a stirring speed of 400 rpm. The temperature was then lowered to 40°C, and three parts of triethylamine (TEA) were added for neutralization reaction, which lasted for 50 min. Next, the stirring speed was increased to 900 rpm, and 20 parts of deionized water were added, followed by one part of ethylenediamine (EDA) for chain extension reaction, which lasted for 3 h. Finally, the mixture was passed through a 400-mesh nylon mesh to obtain a waterborne polyurethane resin.

[0071] (3) Preparation of rare earth modified graphene coatings

[0072] Three parts of rare earth functionalized graphene, three parts of waterborne polyurethane resin, and 50 parts of water are dispersed in a high-speed disperser at 6000 r / min for 50 min. After standing for 30 min, 0.5 parts of leveling agent, 0.5 parts of defoamer, and 0.5 parts of thickener are added in sequence, and dispersion and stirring are continued for 60 min to obtain rare earth modified graphene coating.

[0073] The ultrasonic treatment process parameters are an ultrasonic time of 60 min and a frequency of 90 Hz.

[0074] The leveling agent is any one of acrylates, cellulose acetate, nitrocellulose, diphenylpolysiloxane, methylphenylpolysiloxane, organic-modified polysiloxane, polyether organosilicon, or organofluorine compounds.

[0075] The defoamer is any one of silicone oil, polyether, higher alcohol, mineral oil, vegetable oil, nonylphenol polyoxyethylene ether, soap salt, OP series emulsifier, Tween series emulsifier, and Span series emulsifier.

[0076] The thickener is any one of the following: organic bentonite, sodium bentonite, diatomaceous earth, silica gel, cellulose ethers, starch, gelatin, sodium alginate, casein, guar gum, chitosan, gum arabic, xanthan gum, soybean protein gum, natural rubber, lanolin, and agar.

[0077] An application of a rare-earth modified graphene coating for electromagnetic wave shielding, wherein the rare-earth modified graphene coating for electromagnetic wave shielding is used for electromagnetic wave shielding of electronic devices or as a stealth coating.

[0078] The electromagnetic wave shielding effectiveness test results show that the electromagnetic wave shielding effectiveness of Example 3 is 42.3dB.

[0079] Comparative Example 1: Unlike Example 2, no rare earth functionalized graphene was added during the preparation of the coating. The specific preparation steps are as follows:

[0080] (1) Preparation of waterborne polyurethane resin:

[0081] Two parts of 2,2-dimethylolpropionic acid (DMPA) were placed in a vacuum drying oven and dried at 70°C for 40 min. Then, DMPA was dissolved in 5–10 parts of N-methylpyrrolidone using a water bath stirrer. Subsequently, 1.5 parts of polytetrahydrofuran (PTMEG), 1.5 parts of isophorone diisocyanate (IPDI), and the dissolved DMPA were placed in a three-necked flask. Nitrogen gas was introduced, and the mixture was reacted in a water bath at 70–90°C for 3–6 h with a stirring speed of 300–400 rpm. The temperature was then lowered to 30–40°C, and two parts of triethylamine (TEA) were added for neutralization reaction, with a reaction time of 40 min. Next, the stirring speed was increased to 700 rpm, and 15 parts of deionized water were added, followed by 0.75 parts of ethylenediamine (EDA) for chain extension reaction, which was carried out for 2 h. Finally, the mixture was passed through a 400-mesh nylon mesh to obtain a waterborne polyurethane resin.

[0082] (2) Preparation of rare earth modified graphene coatings

[0083] Two parts of waterborne polyurethane resin and 35 parts of water are dispersed in a high-speed disperser at 5500 r / min for 40 min. After standing for 20 min, 0.3 parts of leveling agent, 0.3 parts of defoamer and 0.3 parts of thickener are added in sequence, and dispersion and stirring are continued for 45 min to obtain rare earth modified graphene coating.

[0084] The ultrasonic treatment process parameters are an ultrasonic time of 45 min and a frequency of 60 Hz.

[0085] The leveling agent is any one of acrylates, cellulose acetate, nitrocellulose, diphenylpolysiloxane, methylphenylpolysiloxane, organic-modified polysiloxane, polyether organosilicon, or organofluorine compounds.

[0086] The defoamer is any one of silicone oil, polyether, higher alcohol, mineral oil, vegetable oil, nonylphenol polyoxyethylene ether, soap salt, OP series emulsifier, Tween series emulsifier, and Span series emulsifier.

[0087] The thickener is any one of the following: organic bentonite, sodium bentonite, diatomaceous earth, silica gel, cellulose ethers, starch, gelatin, sodium alginate, casein, guar gum, chitosan, gum arabic, xanthan gum, soybean protein gum, natural rubber, lanolin, and agar.

[0088] The electromagnetic wave shielding effectiveness test results show that the electromagnetic wave shielding effectiveness of Comparative Example 1 is 35.5dB.

[0089] Comparative Example 2: The difference from Example 2 is that KNO3 is not added to the electrolyte in step (a) of preparing rare earth functionalized graphene. This prevents the formation of rare earth metal oxides at the cathode, thus hindering the preparation of rare earth functionalized graphene and resulting in poor electromagnetic shielding performance of the coating.

[0090] The electromagnetic wave shielding effectiveness test results show that the electromagnetic wave shielding effectiveness of Comparative Example 2 is 34.9 dB.

Claims

1. A method for preparing a rare-earth modified graphene coating for electromagnetic wave shielding, characterized in that, The specific preparation steps are as follows: Step (1): Preparation of rare earth functionalized graphene: Step (a) Electrochemical exfoliation to prepare rare earth functionalized graphene: Graphite paper is used as the anode and platinum sheet is used as the cathode. The electrolyte system is a mixed solution of 0.5~1.5 mol / L H2SO4, 0.1~1 mol / L rare earth sulfate and 0.1~0.4 mol / L KNO3. The graphite paper is pre-immersed in the above mixed solution for 15~20 min, and then pre-electrolyzed at 3~5V for 20~40 min. Then the voltage is increased to 8~10V until the graphene is completely exfoliated to obtain a primary product suspension. Step (b): Vacuum filtration. The above primary product suspension is subjected to vacuum filtration 5 to 6 times to obtain a secondary product suspension. Step (c) Ultrasonic treatment: The above-mentioned secondary product suspension is ultrasonically treated to obtain a tertiary product suspension. Step (d) Freeze-drying: The suspension of the three products obtained in step (c) above is freeze-dried for 46-72 hours. Then, it is pulverized by a pulverizer and passed through a 60-mesh sieve to obtain rare earth functionalized graphene. Step (2): Preparation of waterborne polyurethane resin: Place 1-3 parts of 2,2-dimethylolpropionic acid (DMPA) in a vacuum drying oven and dry at 60-80°C for 30-50 min. Dissolve it in 5-10 parts of N-methylpyrrolidone using a water bath stirrer. Then, add 1-3 parts of polytetrahydrofuran (PTMEG), 1-3 parts of isophorone diisocyanate (IPDI), and the dissolved 2,2-dimethylolpropionic acid to a three-necked flask, purge with nitrogen, and react in a water bath at 70-90°C for 3-6 h with a stirring speed of 300-400 rpm. Cool to 30-40°C and add 1-3 parts of triethylamine (TEA) for neutralization reaction, with a reaction time of 30-50 min. Increase the stirring speed to 600-900 rpm and add 10-20 parts of [unspecified ingredient] to [unspecified ingredient]. Add 0.5-1 part of deionized water and 0.5-1 part of ethylenediamine (EDA) to carry out chain extension reaction for 1-3 hours. Finally, pass the mixture through a nylon mesh to obtain waterborne polyurethane resin. Step (3): Preparation of rare earth modified graphene coating: Disperse 0.5-1 parts of rare earth functionalized graphene, 1-3 parts of waterborne polyurethane resin, and 20-50 parts of water using a high-speed disperser at a speed of 5000-6000 r / min for 30-50 min. After standing for 10-30 min, add 0.1-0.5 parts of leveling agent, 0.1-0.5 parts of defoamer, and 0.1-0.5 parts of thickener in sequence, and continue to disperse and stir for 30-60 min to obtain rare earth modified graphene coating.

2. The method for preparing a rare-earth modified graphene coating for electromagnetic wave shielding according to claim 1, characterized in that, The electrolyte system is a mixed solution of 1 mol / L H2SO4, 0.5 mol / L rare earth sulfate, and 0.2 mol / L KNO3.

3. A method for preparing a rare-earth modified graphene coating for electromagnetic wave shielding according to claim 1 or 2, characterized in that, The rare earth sulfates in the electrolyte are rare earth elements selected from any one of cerium, lanthanum, praseodymium, neodymium, promethium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, lutetium, scandium, and yttrium.

4. The preparation method of a rare earth modified graphene coating for electromagnetic wave shielding according to claim 3, characterized in that, The ultrasonic treatment process parameters are: ultrasonic time of 30-60 min and frequency of 40-90 Hz.

5. The preparation method of a rare earth modified graphene coating for electromagnetic wave shielding according to claim 4, characterized in that, The leveling agent is any one of acrylates, acetate cellulose, nitrocellulose, organic-modified polysiloxanes, and organic fluorine compounds.

6. The method for preparing a rare-earth modified graphene coating for electromagnetic wave shielding according to claim 5, characterized in that, The defoamer is any one of silicone oil, polyether, higher alcohol, mineral oil, vegetable oil, nonylphenol polyoxyethylene ether, soap salt, Tween series emulsifiers, and Span series emulsifiers.

7. The method for preparing a rare-earth modified graphene coating for electromagnetic wave shielding according to claim 6, characterized in that, The thickener is any one of the following: organic bentonite, sodium bentonite, diatomaceous earth, silica gel, cellulose ethers, starch, gelatin, sodium alginate, casein, guar gum, chitosan, gum arabic, xanthan gum, soybean protein gum, natural rubber, lanolin, and agar.

8. An application of a rare-earth modified graphene coating for electromagnetic wave shielding, characterized in that, The rare earth modified graphene coating for electromagnetic wave shielding is prepared by any of the preparation methods described in claims 1-7, and is applied to electromagnetic wave shielding of electronic devices or as a stealth coating.

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