A dynamic cross-linking self-repairing electromagnetic shielding material and its preparation method

Abstract

The present invention discloses a dynamic cross-linked self-repairing electromagnetic shielding material and a preparation method thereof, relating to the technical field of electromagnetic shielding materials. In the preparation of anti-collision and impact-resistant ABS material, the present invention comprises the following steps: polymerizing polypropylene glycol, cystamine, 2,5-diaminomethylfuran, and 4,4'-diphenylmethane diisocyanate to produce a self-repairing polyurethane; reacting maleic anhydride and amino silicone oil to produce a maleamide-based silicone oil; forming a magnetic coating layer on the surface of graphene oxide with ferrous sulfate and cobalt chloride, and then treating the surface of the magnetic coating layer with a maleamide-based silane coupling agent to produce a modified magnetic-coated graphene oxide; and mixing the self-repairing polyurethane, maleamide-based silicone oil, and modified magnetic-coated graphene oxide and pressing them together to produce a dynamic cross-linked self-repairing electromagnetic shielding material. The dynamic cross-linked self-repairing electromagnetic shielding material prepared by the present invention has good tensile strength, self-repairing properties, flame retardancy, and electromagnetic shielding properties.

Description

Technical Field

[0001] The present invention relates to the technical field of polymer materials, and in particular to a dynamically cross-linked self-repairing electromagnetic shielding material and a preparation method thereof. Background Art

[0002] With the rapid development of 5G communications and the widespread use of smart interconnected technologies, electromagnetic pollution has become the fourth largest source of pollution, following noise, air, and water pollution. Electromagnetic waves can disrupt the normal operation of electronic equipment, causing problems such as signal interference and data loss. Furthermore, long-term exposure to electromagnetic waves on large precision instruments can reduce their service life. Furthermore, electromagnetic waves can affect biological growth and endanger human life and health. Currently, electromagnetic radiation pollution is unavoidable in most parts of the world. Therefore, the most effective way to mitigate electromagnetic radiation pollution is to use electromagnetic shielding materials, which attenuate or even block the electromagnetic waves generated by high-frequency circuits. Electromagnetic shielding materials not only eliminate interference with adjacent electronic equipment and radiation to the human body, but also protect the electronic equipment itself from external interference.

[0003] In recent years, researchers have discovered that combining inorganic functional components with polymers to create electromagnetic shielding composites not only effectively shields electromagnetic radiation but also offers advantages such as lightweight and easy processing. Consequently, conductive polymer-based electromagnetic shielding composites have garnered widespread attention from both academia and industry. However, in actual use, mechanical stimuli from the environment can damage electromagnetic shielding materials, with cracks or microcracks impairing their macroscopic performance. Therefore, there is a need to develop magnetic shielding materials with excellent self-healing properties to improve their long-term stability. Summary of the Invention

[0004] The purpose of the present invention is to provide a dynamically cross-linked self-repairing electromagnetic shielding material and a preparation method thereof, so as to solve the problems existing in the prior art.

[0005] In order to solve the above technical problems, the present invention provides the following technical solutions:

[0006] A dynamically cross-linked self-repairing electromagnetic shielding material comprises the following components, measured by mass: 100 parts of self-repairing polyurethane, 20-25 parts of maleimide silicone oil, and 8-10 parts of modified magnetically coated graphene oxide.

[0007] As an optimization, the self-healing polyurethane is polymerized from polypropylene glycol, cystamine, 2,5-diaminomethylfuran, and 4,4'-diphenylmethane diisocyanate.

[0008] As an optimization, the maleamide silicone oil is prepared by reacting maleic anhydride and amino silicone oil.

[0009] As an optimization, the modified magnetically coated graphene oxide is prepared by forming a magnetic coating layer on the surface of graphene oxide with ferrous sulfate and cobalt chloride, and then treating the surface of the magnetic coating layer with a maleimide silane coupling agent.

[0010] A method for preparing a dynamically cross-linked self-repairing electromagnetic shielding material comprises the following steps:

[0011] (1) The reaction raw materials were weighed according to the ratio of hydroxyl group molar amount in polypropylene glycol, amino group molar amount in cystamine, amino group molar amount in 2,5-diaminomethylfuran, and isocyanate group molar amount in 4,4'-diphenylmethane diisocyanate of 1:0.6:0.6:2.2, polypropylene glycol was vacuum dried at 100-120 ° C for 30-40 min, and then 4,4'-diphenylmethane diisocyanate was added at 70-80 ° C in a nitrogen atmosphere, stirred for 40-50 min, and then 4,4'-diphenylmethane diisocyanate was added. 0.003-0.004 times of dibutyltin dilaurate was added, and the mixture was stirred and reacted for 60-80 minutes to obtain a prepolymer; the prepolymer and N,N-dimethylformamide were mixed uniformly at a mass ratio of 1:10-15, and cystamine and 2,5-diaminomethylfuran were added at a uniform rate within 30 minutes under stirring conditions at 0°C. After the addition, the mixture was stirred and reacted for 20-30 minutes, the temperature was raised to 80-90°C, the mixture was stirred and reacted for 2-3 hours, and vacuum dried at 70-80°C for 20-24 hours to obtain a self-healing polyurethane;

[0012] (2) Maleic anhydride and toluene are mixed uniformly in a mass ratio of 1:15-20 to prepare a maleic anhydride solution; γ-aminopropyltriethoxysilane and toluene in a mass ratio of 1:2.5-3 are mixed uniformly and added to the maleic anhydride solution at a uniform speed within 10-12 minutes. After the addition is completed, the mixture is stirred and reacted at room temperature for 40-60 minutes. Then, zinc chloride in an amount equal to the mass of maleic anhydride is added, the temperature is raised to 80-90°C, the mixture is stirred and reacted for 4-6 hours, and the mixture is vacuum dried at 30-40°C for 20-24 hours to prepare a maleic amide silane coupling agent; the above process is repeated for amino silicone oil to prepare maleic amide silicone oil;

[0013] (3) The metal ion mixture and the graphene oxide dispersion are mixed in a mass ratio of 1:2-3, ultrasonically dispersed at room temperature for 80-90 minutes in a nitrogen atmosphere, and then heated to 80-90°C. A hydrazine hydrate mixture of 0.5-0.6 times the mass of the metal ion mixture is added at a uniform rate within 20-30 minutes. After the addition is completed, stirring and reacting are continued for 6-8 hours. The mixture is collected by magnetic decantation and washed with pure water for 3-5 times. The mixture is vacuum dried at 70-80°C for 20-24 hours to obtain magnetically coated graphene oxide; maleimide silane coupling agent, pure water and anhydrous ethanol are mixed in a mass ratio of 1:10-12:1, the pH is adjusted to 10 with tetraethylammonium hydroxide, stirred at room temperature for 10-15 minutes, and then the magnetically coated graphene oxide is added. The stirring reaction is continued for 60-80 minutes, centrifuged, and vacuum dried at 70-80°C for 20-24 hours to obtain modified magnetically coated graphene oxide.

[0014] (4) Weigh 100 parts of self-repairing polyurethane, 20-25 parts of maleimide silicone oil, and 8-10 parts of modified magnetically coated graphene oxide according to their mass fractions; place the self-repairing polyurethane in an internal mixer, and mix it at 180-190°C and 30r / min for 25-30min, then add maleimide silicone oil and modified magnetically coated graphene oxide and continue mixing for 8-10min, then put it into a mold, press it at 180-190°C and 8-10MPa for 10-12min, keep the pressure constant, cool it naturally to room temperature, and then release the pressure to obtain a dynamic cross-linked self-repairing electromagnetic shielding material.

[0015] As an optimization, the preparation method of cystamine in step (1) is as follows: cystamine dihydrochloride and pure water are uniformly mixed in a mass ratio of 1:10-15, and then potassium hydroxide with a mass of 0.7-0.8 times that of cystamine dihydrochloride is added, stirring and reacting for 10-12 minutes, extracting with dichloromethane 3-5 times, adding dichloromethane with a mass of 8-10 times that of cystamine dihydrochloride each time, combining the extracted organic phases, drying with anhydrous sodium sulfate, filtering, and standing at 0.1-0.3 kPa and 20-30° C. for 6-8 hours to prepare the product.

[0016] As an optimization, the model of the polypropylene glycol in step (1) is PPG2000.

[0017] As an optimization, the model of the amino silicone oil in step (2) is N323.

[0018] As an optimization, the graphene oxide dispersion in step (3) is prepared by mixing graphene oxide and pure water in a mass ratio of 1:500-600 and ultrasonically dispersing for 30-40 minutes; the metal ion mixture is prepared by adding ferrous sulfate and cobalt chloride in a molar ratio of 1:1 to pure water 30-40 times the mass of ferrous sulfate and ferrous sulfate, and mixing them uniformly; the hydrazine hydrate mixture is prepared by mixing sodium hydroxide and hydrazine hydrate in a mass ratio of 1:10-15.

[0019] As an optimization, the graphene oxide was purchased from Changzhou Sixth Element Materials Technology Co., Ltd.

[0020] Compared with the prior art, the present invention has the following beneficial effects:

[0021] When preparing a dynamic cross-linked self-repairing electromagnetic shielding material, the present invention comprises the following steps: reacting maleic anhydride and γ-aminopropyltriethoxysilane to obtain a maleimide silane coupling agent; forming a magnetic coating layer on the surface of graphene oxide by adding ferrous sulfate and cobalt chloride; and treating the surface of the magnetic coating layer with the maleimide silane coupling agent to obtain a modified magnetically coated graphene oxide; and mixing and pressing self-repairing polyurethane, maleimide silicone oil, and the modified magnetically coated graphene oxide to form a dynamic cross-linked self-repairing electromagnetic shielding material.

[0022] First, polypropylene glycol, cystamine, 2,5-diaminomethylfuran, and 4,4'-diphenylmethane diisocyanate are polymerized to prepare self-healing polyurethane. Cystamine is used to participate in the polymerization to prepare the self-healing polyurethane. The disulfide bonds in cystamine can make the molecular backbone of the self-healing polyurethane have a good self-healing effect, thereby improving the overall self-healing performance; 2,5-diaminomethylfuran is used to participate in the polymerization to prepare the self-healing polyurethane. 2,5-diaminomethylfuran can cross-link with maleimide silicone oil and the maleimide group on the modified magnetic-coated graphene oxide through a thermally reversible cycloaddition reaction to form a cross-linked network structure, thereby improving the tensile strength and can self-heal through thermally reversible cycloaddition.

[0023] Secondly, maleic anhydride and amino silicone oil are reacted to produce maleimide silicone oil, which generates silicon-oxygen and silicon-carbon composite layers under high temperature, thereby playing the role of heat insulation, oxygen isolation and prevention of harmful gas escape, improving the flame retardant effect. In addition, the maleimide group on the maleimide silicone oil can participate in the cross-linking network formed by the thermally reversible cycloaddition reaction, thereby improving the tensile strength and self-healing properties.

[0024] Finally, ferrous sulfate and cobalt chloride are used to form a magnetic coating layer on the surface of graphene oxide, and then the surface of the magnetic coating layer is treated with a maleimide silane coupling agent to obtain a modified magnetically coated graphene oxide. After magnetic coating, the graphene oxide has electromagnetic dual functions and can effectively capture incident electromagnetic waves, thereby improving the electromagnetic shielding performance; after modification with a maleimide silane coupling agent, the dispersibility of the modified magnetically coated graphene oxide can be improved, and the effect of the modified magnetically coated graphene oxide can be better exerted. DETAILED DESCRIPTION

[0025] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0026] In order to more clearly illustrate the method provided by the present invention, the following examples are described in detail.

[0027] Example 1

[0028] A method for preparing a dynamically cross-linked self-repairing electromagnetic shielding material mainly comprises the following preparation steps:

[0029] (1) Cystamine dihydrochloride and pure water were mixed in a mass ratio of 1:10, and then potassium hydroxide with a mass of 0.7 times that of cystamine dihydrochloride was added, stirred and reacted for 12 minutes, extracted with dichloromethane for 3 times, and dichloromethane with a mass of 8 times that of cystamine dihydrochloride was added each time. The extracted organic phases were combined, dried with anhydrous sodium sulfate, and filtered. The mixture was allowed to stand at 0.1 kPa and 20°C for 8 hours to obtain cystamine. The reaction raw materials were weighed according to the ratio of hydroxyl molar amount in polypropylene glycol PPG2000, amino molar amount in cystamine, amino molar amount in 2,5-diaminomethylfuran, and isocyanate molar amount in 4,4'-diphenylmethane diisocyanate of 1:0.6:0.6:2.2. PPG2000 was vacuum dried at 100°C for 40 minutes, and then 4,4'-diphenylmethane diisocyanate was added at 70°C in a nitrogen atmosphere and stirred for 40 minutes. Then, dibutyltin dilaurate (0.003 times the mass of 4,4'-diphenylmethane diisocyanate) was added and stirred for 80 minutes to obtain a prepolymer. The prepolymer and N,N-dimethylformamide were mixed at a mass ratio of 1:10, and cystamine and 2,5-diaminomethylfuran were added at a uniform rate within 30 minutes under stirring at 0°C. After the addition, the mixture was stirred for 20 minutes, the temperature was raised to 80°C, the mixture was stirred for 3 hours, and vacuum dried at 70°C for 24 hours to obtain a self-healing polyurethane.

[0030] (2) Maleic anhydride and toluene were mixed in a mass ratio of 1:15 to prepare a maleic anhydride solution; γ-aminopropyltriethoxysilane and toluene in a mass ratio of 1:2.5 were mixed and added to the maleic anhydride solution at a uniform speed within 10 minutes. After the addition was completed, the mixture was stirred at room temperature for 60 minutes. Then, zinc chloride in a mass equal to that of maleic anhydride was added, the temperature was raised to 80°C, the mixture was stirred for 6 hours, and vacuum dried at 30°C for 24 hours to prepare a maleic amide silane coupling agent; the above process was repeated with amino silicone oil N323 to prepare maleic amide silicone oil;

[0031] (3) Graphene oxide was mixed with pure water at a mass ratio of 1:600 ​​and ultrasonically dispersed for 30 minutes to prepare a graphene oxide dispersion; ferrous sulfate and cobalt chloride were added to pure water 40 times the mass of ferrous sulfate in a molar ratio of 1:1 and mixed evenly to prepare a metal ion mixture; sodium hydroxide and hydrazine hydrate were mixed evenly at a mass ratio of 1:15 to prepare a hydrazine hydrate mixture; the metal ion mixture and the graphene oxide dispersion were mixed evenly at a mass ratio of 1:3, ultrasonically dispersed at room temperature in a nitrogen atmosphere for 90 minutes, then heated to 90°C and homogenized within 30 minutes. A hydrazine hydrate mixture with a mass of 0.5 times that of the metal ion mixture was quickly added, and after the addition was completed, the mixture was stirred and reacted for 8 hours, collected by magnetic decantation, washed with pure water 3 times, and vacuum dried at 70°C for 24 hours to obtain magnetically coated graphene oxide; a maleimide silane coupling agent, pure water, and anhydrous ethanol were uniformly mixed in a mass ratio of 1:12:1, the pH was adjusted to 10 with tetraethylammonium hydroxide, and stirred at room temperature for 15 minutes, and then the magnetically coated graphene oxide was added, and the stirring reaction was continued for 80 minutes, centrifuged, and vacuum dried at 80°C for 24 hours to obtain modified magnetically coated graphene oxide;

[0032] (4) Weigh 100 parts of self-repairing polyurethane, 20 parts of maleimide silicone oil, and 8 parts of modified magnetically coated graphene oxide according to their mass fractions; place the self-repairing polyurethane in an internal mixer, and mix at 180°C, 30 r / min for 25 minutes, then add maleimide silicone oil and modified magnetically coated graphene oxide and continue mixing for 10 minutes, then put it into a mold, press at 180°C, 8 MPa for 12 minutes, keep the pressure constant, cool naturally to room temperature, and then release the pressure to obtain a dynamic cross-linked self-repairing electromagnetic shielding material.

[0033] Example 2

[0034] A method for preparing a dynamically cross-linked self-repairing electromagnetic shielding material mainly comprises the following preparation steps:

[0035] (1) Cystamine dihydrochloride and pure water were mixed in a mass ratio of 1:12, and potassium hydroxide with a mass of 0.75 times that of cystamine dihydrochloride was added, and the mixture was stirred for 11 minutes. The mixture was extracted with dichloromethane for 4 times, and dichloromethane with a mass of 9 times that of cystamine dihydrochloride was added each time. The extracted organic phases were combined, dried with anhydrous sodium sulfate, and filtered. The mixture was allowed to stand at 0.2 kPa and 25°C for 7 hours to obtain cystamine. The reaction raw materials were weighed according to the ratio of hydroxyl molar amount in polypropylene glycol PPG2000, amino molar amount in cystamine, amino molar amount in 2,5-diaminomethylfuran, and isocyanate molar amount in 4,4'-diphenylmethane diisocyanate of 1:0.6:0.6:2.2. The reaction mixture was stirred for 1 minute. PG2000 was vacuum dried at 110°C for 35 minutes, and then 4,4'-diphenylmethane diisocyanate was added at 75°C in a nitrogen atmosphere, stirred for 45 minutes, and then dibutyltin dilaurate (0.0035 times the mass of 4,4'-diphenylmethane diisocyanate) was added, and the stirring reaction was continued for 70 minutes to obtain a prepolymer; the prepolymer and N,N-dimethylformamide were evenly mixed in a mass ratio of 1:12, and cystamine and 2,5-diaminomethylfuran were added at a uniform rate within 30 minutes under stirring conditions at 0°C. After the addition, the stirring reaction was continued for 25 minutes, the temperature was raised to 85°C, the stirring reaction was continued for 2.5 hours, and the self-healing polyurethane was vacuum dried at 75°C for 22 hours to obtain a self-healing polyurethane;

[0036] (2) Maleic anhydride and toluene were mixed in a mass ratio of 1:18 to prepare a maleic anhydride solution; γ-aminopropyltriethoxysilane and toluene in a mass ratio of 1:2.8 were mixed evenly and added to the maleic anhydride solution at a uniform speed within 11 minutes. After the addition was completed, the mixture was stirred at room temperature for 50 minutes. Then, zinc chloride in a mass equal to that of maleic anhydride was added, the temperature was raised to 85°C, the mixture was stirred for 5 hours, and vacuum dried at 35°C for 22 hours to prepare a maleic amide silane coupling agent; the above process was repeated with amino silicone oil N323 to prepare maleic amide silicone oil;

[0037] (3) Graphene oxide was mixed with pure water at a mass ratio of 1:550 and ultrasonically dispersed for 35 minutes to prepare a graphene oxide dispersion; ferrous sulfate and cobalt chloride were added to pure water 35 times the mass of ferrous sulfate in a molar ratio of 1:1 and mixed evenly to prepare a metal ion mixture; sodium hydroxide and hydrazine hydrate were mixed evenly at a mass ratio of 1:12 to prepare a hydrazine hydrate mixture; the metal ion mixture and the graphene oxide dispersion were mixed evenly at a mass ratio of 1:2.5, ultrasonically dispersed at room temperature in a nitrogen atmosphere for 85 minutes, then heated to 85°C and homogenized within 25 minutes. A hydrazine hydrate mixture with a mass of 0.55 times that of the metal ion mixture was quickly added, and after the addition was completed, the mixture was stirred and reacted for 7 hours, collected by magnetic decantation, washed with pure water 4 times, and vacuum dried at 75°C for 22 hours to obtain magnetically coated graphene oxide; a maleimide silane coupling agent, pure water, and anhydrous ethanol were uniformly mixed in a mass ratio of 1:11:1, the pH was adjusted to 10 with tetraethylammonium hydroxide, stirred at room temperature for 12 minutes, and then the magnetically coated graphene oxide was added, and the stirring reaction was continued for 70 minutes, centrifuged, and vacuum dried at 75°C for 22 hours to obtain modified magnetically coated graphene oxide;

[0038] (4) Weigh 100 parts of self-repairing polyurethane, 22 parts of maleimide silicone oil, and 9 parts of modified magnetically coated graphene oxide according to their mass fractions; place the self-repairing polyurethane in an internal mixer, and mix it at 185°C and 30 r / min for 28 minutes. Then add maleimide silicone oil and modified magnetically coated graphene oxide and continue mixing for 9 minutes. Then, put it into a mold and press it at 185°C and 9 MPa for 11 minutes. Keep the pressure constant and cool it naturally to room temperature. Then, release the pressure and take it out to obtain a dynamic cross-linked self-repairing electromagnetic shielding material.

[0039] Example 3

[0040] A method for preparing a dynamically cross-linked self-repairing electromagnetic shielding material mainly comprises the following preparation steps:

[0041] (1) Cystamine dihydrochloride and pure water were mixed in a mass ratio of 1:15, and then potassium hydroxide with a mass of 0.8 times that of cystamine dihydrochloride was added, stirred and reacted for 12 minutes, extracted with dichloromethane 5 times, and dichloromethane with a mass of 10 times that of cystamine dihydrochloride was added each time, the extracted organic phases were combined, dried with anhydrous sodium sulfate and filtered, and allowed to stand at 0.3 kPa and 30°C for 6 hours to obtain cystamine; the reaction raw materials were weighed according to the ratio of hydroxyl molar amount in polypropylene glycol PPG2000, amino molar amount in cystamine, amino molar amount in 2,5-diaminomethylfuran, and isocyanate molar amount in 4,4'-diphenylmethane diisocyanate of 1:0.6:0.6:2.2, and polypropylene glycol was added. PPG2000 was vacuum dried at 120°C for 30 minutes, and then 4,4'-diphenylmethane diisocyanate was added at 80°C in a nitrogen atmosphere, stirred for 40 minutes, and then dibutyltin dilaurate (0.004 times the mass of 4,4'-diphenylmethane diisocyanate) was added, and the stirring reaction continued for 60 minutes to obtain a prepolymer; the prepolymer and N,N-dimethylformamide were evenly mixed at a mass ratio of 1:15, and cystamine and 2,5-diaminomethylfuran were added at a uniform rate within 30 minutes under stirring conditions at 0°C. After the addition was completed, the stirring reaction continued for 20 minutes, the temperature was raised to 90°C, the stirring reaction continued for 2 hours, and the self-healing polyurethane was vacuum dried at 80°C for 20 hours to obtain a self-healing polyurethane;

[0042] (2) Maleic anhydride and toluene were mixed in a mass ratio of 1:20 to prepare a maleic anhydride solution; γ-aminopropyltriethoxysilane and toluene in a mass ratio of 1:3 were mixed and added to the maleic anhydride solution at a uniform speed within 12 minutes. After the addition was completed, the mixture was stirred and reacted at room temperature for 40 minutes. Then, zinc chloride in a mass equal to that of maleic anhydride was added, the temperature was raised to 90°C, the mixture was stirred and reacted for 4 hours, and vacuum dried at 40°C for 20 hours to prepare a maleic amide silane coupling agent; the above process was repeated with amino silicone oil N323 to prepare maleic amide silicone oil;

[0043] (3) Graphene oxide was mixed with pure water at a mass ratio of 1:600 ​​and ultrasonically dispersed for 30 minutes to prepare a graphene oxide dispersion; ferrous sulfate and cobalt chloride were added to pure water 40 times the mass of ferrous sulfate in a molar ratio of 1:1 and mixed evenly to prepare a metal ion mixture; sodium hydroxide and hydrazine hydrate were mixed evenly at a mass ratio of 1:15 to prepare a hydrazine hydrate mixture; the metal ion mixture and the graphene oxide dispersion were mixed evenly at a mass ratio of 1:3, ultrasonically dispersed at room temperature in a nitrogen atmosphere for 90 minutes, then heated to 90°C and homogenized within 30 minutes. A hydrazine hydrate mixture with a mass of 0.6 times that of the metal ion mixture was quickly added, and after the addition was completed, the mixture was stirred and reacted for 6 hours, collected by magnetic decantation, washed with pure water 5 times, and vacuum dried at 80°C for 20 hours to obtain magnetically coated graphene oxide; a maleimide silane coupling agent, pure water, and anhydrous ethanol were uniformly mixed in a mass ratio of 1:12:1, the pH was adjusted to 10 with tetraethylammonium hydroxide, and stirred at room temperature for 10 minutes, and then the magnetically coated graphene oxide was added, and the stirring reaction was continued for 60 minutes, centrifuged, and vacuum dried at 80°C for 20 hours to obtain modified magnetically coated graphene oxide;

[0044] (4) Weigh 100 parts of self-repairing polyurethane, 25 parts of maleimide silicone oil, and 10 parts of modified magnetically coated graphene oxide according to their mass fractions; place the self-repairing polyurethane in an internal mixer, and mix it at 190°C and 30 r / min for 25 minutes. Then add maleimide silicone oil and modified magnetically coated graphene oxide and continue mixing for 10 minutes. Then, put it into a mold and press it at 190°C and 10 MPa for 10 minutes. Keep the pressure constant, cool it naturally to room temperature, and then release the pressure to take it out to obtain a dynamic cross-linked self-repairing electromagnetic shielding material.

[0045] Comparative Example 1

[0046] A method for preparing a dynamically cross-linked self-repairing electromagnetic shielding material mainly comprises the following preparation steps:

[0047] (1) The reaction raw materials were weighed according to the ratio of 1:1.2:2.2 of the molar amount of hydroxyl group in polypropylene glycol PPG2000, the molar amount of amino group in 2,5-diaminomethylfuran, and the molar amount of isocyanate group in 4,4'-diphenylmethane diisocyanate. Polypropylene glycol PPG2000 was vacuum dried at 110 °C for 35 min, and then 4,4'-diphenylmethane diisocyanate was added at 75 °C in a nitrogen atmosphere and stirred for 45 min. Then 4,4'-diphenylmethane diisocyanate was added. The prepolymer was prepared by adding 0.0035 times the mass of dibutyltin dilaurate to the diisocyanate and stirring for 70 minutes. The prepolymer and N,N-dimethylformamide were mixed at a mass ratio of 1:12, and 2,5-diaminomethylfuran was added at a uniform rate within 30 minutes under stirring at 0°C. After the addition, the stirring reaction was continued for 25 minutes. The temperature was raised to 85°C and the stirring reaction was continued for 2.5 hours. The self-healing polyurethane was obtained by vacuum drying at 75°C for 22 hours.

[0048] (2) Maleic anhydride and toluene were mixed in a mass ratio of 1:18 to prepare a maleic anhydride solution; γ-aminopropyltriethoxysilane and toluene in a mass ratio of 1:2.8 were mixed evenly and added to the maleic anhydride solution at a uniform speed within 11 minutes. After the addition was completed, the mixture was stirred at room temperature for 50 minutes. Then, zinc chloride in a mass equal to that of maleic anhydride was added, the temperature was raised to 85°C, the mixture was stirred for 5 hours, and vacuum dried at 35°C for 22 hours to prepare a maleic amide silane coupling agent; the above process was repeated with amino silicone oil N323 to prepare maleic amide silicone oil;

[0049] (3) Graphene oxide was mixed with pure water at a mass ratio of 1:550 and ultrasonically dispersed for 35 minutes to prepare a graphene oxide dispersion; ferrous sulfate and cobalt chloride were added to pure water 35 times the mass of ferrous sulfate in a molar ratio of 1:1 and mixed evenly to prepare a metal ion mixture; sodium hydroxide and hydrazine hydrate were mixed evenly at a mass ratio of 1:12 to prepare a hydrazine hydrate mixture; the metal ion mixture and the graphene oxide dispersion were mixed evenly at a mass ratio of 1:2.5, ultrasonically dispersed at room temperature in a nitrogen atmosphere for 85 minutes, then heated to 85°C and homogenized within 25 minutes. A hydrazine hydrate mixture with a mass of 0.55 times that of the metal ion mixture was quickly added, and after the addition was completed, the mixture was stirred and reacted for 7 hours, collected by magnetic decantation, washed with pure water 4 times, and vacuum dried at 75°C for 22 hours to obtain magnetically coated graphene oxide; a maleimide silane coupling agent, pure water, and anhydrous ethanol were uniformly mixed in a mass ratio of 1:11:1, the pH was adjusted to 10 with tetraethylammonium hydroxide, stirred at room temperature for 12 minutes, and then the magnetically coated graphene oxide was added, and the stirring reaction was continued for 70 minutes, centrifuged, and vacuum dried at 75°C for 22 hours to obtain modified magnetically coated graphene oxide;

[0050] (4) Weigh 100 parts of self-repairing polyurethane, 22 parts of maleimide silicone oil, and 9 parts of modified magnetically coated graphene oxide according to their mass fractions; place the self-repairing polyurethane in an internal mixer, and mix it at 185°C and 30 r / min for 28 minutes. Then add maleimide silicone oil and modified magnetically coated graphene oxide and continue mixing for 9 minutes. Then, put it into a mold and press it at 185°C and 9 MPa for 11 minutes. Keep the pressure constant and cool it naturally to room temperature. Then, release the pressure and take it out to obtain a dynamic cross-linked self-repairing electromagnetic shielding material.

[0051] Comparative Example 2

[0052] A method for preparing a dynamically cross-linked self-repairing electromagnetic shielding material mainly comprises the following preparation steps:

[0053] (1) Cystamine dihydrochloride and pure water were mixed in a mass ratio of 1:12, and potassium hydroxide with a mass of 0.75 times that of cystamine dihydrochloride was added, and the mixture was stirred for 11 minutes. The mixture was extracted with dichloromethane for 4 times, and dichloromethane with a mass of 9 times that of cystamine dihydrochloride was added each time. The organic phases were combined, dried with anhydrous sodium sulfate, and filtered. The mixture was allowed to stand at 0.2 kPa and 25 ° C for 7 hours to obtain cystamine. The reaction raw materials were weighed according to the ratio of hydroxyl molar amount in polypropylene glycol PPG2000, amino molar amount in cystamine, and isocyanate molar amount in 4,4'-diphenylmethane diisocyanate of 1:1.2:2.2. The mixture was added with dichloromethane. 0 was vacuum dried at 110°C for 35 minutes, and then 4,4'-diphenylmethane diisocyanate was added at 75°C in a nitrogen atmosphere, stirred for 45 minutes, and then 0.0035 times the mass of dibutyltin dilaurate of 4,4'-diphenylmethane diisocyanate was added, and the stirring reaction was continued for 70 minutes to obtain a prepolymer; the prepolymer and N,N-dimethylformamide were evenly mixed in a mass ratio of 1:12, and cystamine was added at a uniform rate within 30 minutes under stirring conditions at 0°C. After the addition was completed, the stirring reaction was continued for 25 minutes, the temperature was raised to 85°C, the stirring reaction was continued for 2.5 hours, and the self-healing polyurethane was vacuum dried at 75°C for 22 hours to obtain a self-healing polyurethane;

[0054] (2) Maleic anhydride and toluene were mixed in a mass ratio of 1:18 to prepare a maleic anhydride solution; γ-aminopropyltriethoxysilane and toluene in a mass ratio of 1:2.8 were mixed evenly and added to the maleic anhydride solution at a uniform speed within 11 minutes. After the addition was completed, the mixture was stirred at room temperature for 50 minutes. Then, zinc chloride in a mass equal to that of maleic anhydride was added, the temperature was raised to 85°C, the mixture was stirred for 5 hours, and vacuum dried at 35°C for 22 hours to prepare a maleic amide silane coupling agent; the above process was repeated with amino silicone oil N323 to prepare maleic amide silicone oil;

[0055] (3) Graphene oxide was mixed with pure water at a mass ratio of 1:550 and ultrasonically dispersed for 35 minutes to prepare a graphene oxide dispersion; ferrous sulfate and cobalt chloride were added to pure water 35 times the mass of ferrous sulfate in a molar ratio of 1:1 and mixed evenly to prepare a metal ion mixture; sodium hydroxide and hydrazine hydrate were mixed evenly at a mass ratio of 1:12 to prepare a hydrazine hydrate mixture; the metal ion mixture and the graphene oxide dispersion were mixed evenly at a mass ratio of 1:2.5, ultrasonically dispersed at room temperature in a nitrogen atmosphere for 85 minutes, then heated to 85°C and homogenized within 25 minutes. A hydrazine hydrate mixture with a mass of 0.55 times that of the metal ion mixture was quickly added, and after the addition was completed, the mixture was stirred and reacted for 7 hours, collected by magnetic decantation, washed with pure water 4 times, and vacuum dried at 75°C for 22 hours to obtain magnetically coated graphene oxide; a maleimide silane coupling agent, pure water, and anhydrous ethanol were uniformly mixed in a mass ratio of 1:11:1, the pH was adjusted to 10 with tetraethylammonium hydroxide, stirred at room temperature for 12 minutes, and then the magnetically coated graphene oxide was added, and the stirring reaction was continued for 70 minutes, centrifuged, and vacuum dried at 75°C for 22 hours to obtain modified magnetically coated graphene oxide;

[0056] (4) Weigh 100 parts of self-repairing polyurethane, 22 parts of maleimide silicone oil, and 9 parts of modified magnetically coated graphene oxide according to their mass fractions; place the self-repairing polyurethane in an internal mixer, and mix it at 185°C and 30 r / min for 28 minutes. Then add maleimide silicone oil and modified magnetically coated graphene oxide and continue mixing for 9 minutes. Then, put it into a mold and press it at 185°C and 9 MPa for 11 minutes. Keep the pressure constant and cool it naturally to room temperature. Then, release the pressure and take it out to obtain a dynamic cross-linked self-repairing electromagnetic shielding material.

[0057] Comparative Example 3

[0058] A method for preparing a dynamically cross-linked self-repairing electromagnetic shielding material mainly comprises the following preparation steps:

[0059] (1) Cystamine dihydrochloride and pure water were mixed in a mass ratio of 1:12, and potassium hydroxide with a mass of 0.75 times that of cystamine dihydrochloride was added, and the mixture was stirred for 11 minutes. The mixture was extracted with dichloromethane for 4 times, and dichloromethane with a mass of 9 times that of cystamine dihydrochloride was added each time. The extracted organic phases were combined, dried with anhydrous sodium sulfate, and filtered. The mixture was allowed to stand at 0.2 kPa and 25°C for 7 hours to obtain cystamine. The reaction raw materials were weighed according to the ratio of hydroxyl molar amount in polypropylene glycol PPG2000, amino molar amount in cystamine, amino molar amount in 2,5-diaminomethylfuran, and isocyanate molar amount in 4,4'-diphenylmethane diisocyanate of 1:0.6:0.6:2.2. The reaction mixture was stirred for 1 minute. PG2000 was vacuum dried at 110°C for 35 minutes, and then 4,4'-diphenylmethane diisocyanate was added at 75°C in a nitrogen atmosphere, stirred for 45 minutes, and then dibutyltin dilaurate (0.0035 times the mass of 4,4'-diphenylmethane diisocyanate) was added, and the stirring reaction was continued for 70 minutes to obtain a prepolymer; the prepolymer and N,N-dimethylformamide were evenly mixed in a mass ratio of 1:12, and cystamine and 2,5-diaminomethylfuran were added at a uniform rate within 30 minutes under stirring conditions at 0°C. After the addition, the stirring reaction was continued for 25 minutes, the temperature was raised to 85°C, the stirring reaction was continued for 2.5 hours, and the self-healing polyurethane was vacuum dried at 75°C for 22 hours to obtain a self-healing polyurethane;

[0060] (2) Maleic anhydride and toluene were mixed in a mass ratio of 1:18 to prepare a maleic anhydride solution; γ-aminopropyltriethoxysilane and toluene in a mass ratio of 1:2.8 were mixed and added to the maleic anhydride solution at a uniform speed within 11 minutes. After the addition was completed, the mixture was stirred at room temperature for 50 minutes. Then, zinc chloride in a mass equal to that of maleic anhydride was added, the temperature was raised to 85°C, the mixture was stirred for 5 hours, and the mixture was dried in vacuo at 35°C for 22 hours to obtain a maleamide silane coupling agent;

[0061] (3) Graphene oxide was mixed with pure water at a mass ratio of 1:550 and ultrasonically dispersed for 35 minutes to prepare a graphene oxide dispersion; ferrous sulfate and cobalt chloride were added to pure water 35 times the mass of ferrous sulfate in a molar ratio of 1:1 and mixed evenly to prepare a metal ion mixture; sodium hydroxide and hydrazine hydrate were mixed evenly at a mass ratio of 1:12 to prepare a hydrazine hydrate mixture; the metal ion mixture and the graphene oxide dispersion were mixed evenly at a mass ratio of 1:2.5, ultrasonically dispersed at room temperature in a nitrogen atmosphere for 85 minutes, then heated to 85°C and homogenized within 25 minutes. A hydrazine hydrate mixture with a mass of 0.55 times that of the metal ion mixture was quickly added, and after the addition was completed, the mixture was stirred and reacted for 7 hours, collected by magnetic decantation, washed with pure water 4 times, and vacuum dried at 75°C for 22 hours to obtain magnetically coated graphene oxide; a maleimide silane coupling agent, pure water, and anhydrous ethanol were uniformly mixed in a mass ratio of 1:11:1, the pH was adjusted to 10 with tetraethylammonium hydroxide, stirred at room temperature for 12 minutes, and then the magnetically coated graphene oxide was added, and the stirring reaction was continued for 70 minutes, centrifuged, and vacuum dried at 75°C for 22 hours to obtain modified magnetically coated graphene oxide;

[0062] (4) Weigh 122 parts of self-repairing polyurethane and 9 parts of modified magnetically coated graphene oxide by mass; place the self-repairing polyurethane in an internal mixer, mix at 185°C, 30 r / min for 28 minutes, then add the modified magnetically coated graphene oxide and continue mixing for 9 minutes, then put it into a mold, press at 185°C, 9 MPa for 11 minutes, keep the pressure constant, cool naturally to room temperature, and then release the pressure to obtain a dynamic cross-linked self-repairing electromagnetic shielding material.

[0063] Comparative Example 4

[0064] A method for preparing a dynamically cross-linked self-repairing electromagnetic shielding material mainly comprises the following preparation steps:

[0065] (1) Cystamine dihydrochloride and pure water were mixed in a mass ratio of 1:12, and potassium hydroxide with a mass of 0.75 times that of cystamine dihydrochloride was added, and the mixture was stirred for 11 minutes. The mixture was extracted with dichloromethane for 4 times, and dichloromethane with a mass of 9 times that of cystamine dihydrochloride was added each time. The extracted organic phases were combined, dried with anhydrous sodium sulfate, and filtered. The mixture was allowed to stand at 0.2 kPa and 25°C for 7 hours to obtain cystamine. The reaction raw materials were weighed according to the ratio of hydroxyl molar amount in polypropylene glycol PPG2000, amino molar amount in cystamine, amino molar amount in 2,5-diaminomethylfuran, and isocyanate molar amount in 4,4'-diphenylmethane diisocyanate of 1:0.6:0.6:2.2. The reaction mixture was stirred for 1 minute. PG2000 was vacuum dried at 110°C for 35 minutes, and then 4,4'-diphenylmethane diisocyanate was added at 75°C in a nitrogen atmosphere, stirred for 45 minutes, and then dibutyltin dilaurate (0.0035 times the mass of 4,4'-diphenylmethane diisocyanate) was added, and the stirring reaction was continued for 70 minutes to obtain a prepolymer; the prepolymer and N,N-dimethylformamide were evenly mixed in a mass ratio of 1:12, and cystamine and 2,5-diaminomethylfuran were added at a uniform rate within 30 minutes under stirring conditions at 0°C. After the addition, the stirring reaction was continued for 25 minutes, the temperature was raised to 85°C, the stirring reaction was continued for 2.5 hours, and the self-healing polyurethane was vacuum dried at 75°C for 22 hours to obtain a self-healing polyurethane;

[0066] (2) Maleic anhydride and toluene were mixed uniformly in a mass ratio of 1:18 to prepare a maleic anhydride solution; amino silicone oil N323 was taken according to the molar amount of maleic anhydride and the molar amount of amino groups in amino silicone oil N323 being 1:1; amino silicone oil and toluene were mixed uniformly in a mass ratio of 1:2.8, and added to the maleic anhydride solution at a uniform speed within 11 minutes. After the addition was completed, the mixture was stirred at room temperature for 50 minutes, and then zinc chloride of the same mass as maleic anhydride was added, the temperature was raised to 85°C, the mixture was stirred for 5 hours, and the mixture was dried in vacuo at 35°C for 22 hours to obtain maleamide silicone oil;

[0067] (3) Graphene oxide and pure water were mixed at a mass ratio of 1:550 and ultrasonically dispersed for 35 minutes to prepare a graphene oxide dispersion; ferrous sulfate and cobalt chloride were added to pure water 35 times the mass of ferrous sulfate in a molar ratio of 1:1 and mixed evenly to prepare a metal ion mixture; sodium hydroxide and hydrazine hydrate were mixed evenly at a mass ratio of 1:12 to prepare a hydrazine hydrate mixture; the metal ion mixture and graphene oxide dispersion were mixed evenly at a mass ratio of 1:2.5, ultrasonically dispersed at room temperature in a nitrogen atmosphere for 85 minutes, then heated to 85°C, and hydrazine hydrate mixture 0.55 times the mass of the metal ion mixture was added at a uniform rate within 25 minutes. After the addition was completed, the reaction was stirred for 7 hours, collected by magnetic decantation, washed with pure water 4 times, and vacuum dried at 75°C for 22 hours to obtain magnetically coated graphene oxide;

[0068] (4) Weigh 100 parts of self-repairing polyurethane, 22 parts of maleimide silicone oil, and 9 parts of magnetically coated graphene oxide according to their mass fractions; place the self-repairing polyurethane in an internal mixer, and mix it at 185°C and 30 r / min for 28 minutes. Then add maleimide silicone oil and magnetically coated graphene oxide and continue mixing for 9 minutes. Then, put it into a mold and press it at 185°C and 9 MPa for 11 minutes. Keep the pressure constant and cool it naturally to room temperature. Then, release the pressure and take it out to obtain a dynamic cross-linked self-repairing electromagnetic shielding material.

[0069] Comparative Example 5

[0070] A method for preparing a dynamically cross-linked self-repairing electromagnetic shielding material mainly comprises the following preparation steps:

[0071] (1) Cystamine dihydrochloride and pure water were mixed in a mass ratio of 1:12, and potassium hydroxide with a mass of 0.75 times that of cystamine dihydrochloride was added, and the mixture was stirred for 11 minutes. The mixture was extracted with dichloromethane for 4 times, and dichloromethane with a mass of 9 times that of cystamine dihydrochloride was added each time. The extracted organic phases were combined, dried with anhydrous sodium sulfate, and filtered. The mixture was allowed to stand at 0.2 kPa and 25°C for 7 hours to obtain cystamine. The reaction raw materials were weighed according to the ratio of hydroxyl molar amount in polypropylene glycol PPG2000, amino molar amount in cystamine, amino molar amount in 2,5-diaminomethylfuran, and isocyanate molar amount in 4,4'-diphenylmethane diisocyanate of 1:0.6:0.6:2.2. The reaction mixture was stirred for 1 minute. PG2000 was vacuum dried at 110°C for 35 minutes, and then 4,4'-diphenylmethane diisocyanate was added at 75°C in a nitrogen atmosphere, stirred for 45 minutes, and then dibutyltin dilaurate (0.0035 times the mass of 4,4'-diphenylmethane diisocyanate) was added, and the stirring reaction was continued for 70 minutes to obtain a prepolymer; the prepolymer and N,N-dimethylformamide were evenly mixed in a mass ratio of 1:12, and cystamine and 2,5-diaminomethylfuran were added at a uniform rate within 30 minutes under stirring conditions at 0°C. After the addition, the stirring reaction was continued for 25 minutes, the temperature was raised to 85°C, the stirring reaction was continued for 2.5 hours, and the self-healing polyurethane was vacuum dried at 75°C for 22 hours to obtain a self-healing polyurethane;

[0072] (2) Maleic anhydride and toluene were mixed uniformly in a mass ratio of 1:18 to prepare a maleic anhydride solution; amino silicone oil N323 was taken according to the molar amount of maleic anhydride and the molar amount of amino groups in amino silicone oil N323 being 1:1; amino silicone oil and toluene were mixed uniformly in a mass ratio of 1:2.8, and added to the maleic anhydride solution at a uniform speed within 11 minutes. After the addition was completed, the mixture was stirred at room temperature for 50 minutes, and then zinc chloride of the same mass as maleic anhydride was added, the temperature was raised to 85°C, the mixture was stirred for 5 hours, and the mixture was dried in vacuo at 35°C for 22 hours to obtain maleamide silicone oil;

[0073] (3) Weigh 100 parts of self-healing polyurethane, 22 parts of maleimide silicone oil, and 9 parts of graphene oxide by mass; place the self-healing polyurethane in an internal mixer, and mix it at 185°C and 30 r / min for 28 minutes. Then add maleimide silicone oil and magnetically coated graphene oxide and continue mixing for 9 minutes. Then put it into a mold and press it at 185°C and 9 MPa for 11 minutes. Keep the pressure constant and cool it naturally to room temperature. Then release the pressure and take it out to obtain a dynamic cross-linked self-healing electromagnetic shielding material.

[0074] Test Example 1

[0075] Testing of tensile strength and self-healing properties

[0076] Tensile Strength Test Method: The dynamically cross-linked self-healing electromagnetic shielding materials obtained in each example and comparative example were prepared into strips according to the national standard GB / T528. The samples were tensile tested using a Z005 electronic universal material testing machine at a tensile speed of 50 mm / min to determine the initial tensile strength.

[0077] Self-healing performance testing method: Cut the specimen in the middle and tightly fit the sections together. Heat the spliced ​​specimen in an oven at 130°C for 0.5 hours, then maintain it at 80°C for 8 hours. Test the repaired tensile strength again. Calculate the repair rate (post-repair tensile strength / initial tensile strength).

[0078] The results are shown in Table 1.

[0079] Table 1

[0080] Initial tensile strength Repair rate Initial tensile strength Repair rate Example 1 43.7MPa 91.2％ Comparative Example 2 28.1MPa 75.8％ Example 2 44.3MPa 91.3％ Comparative Example 3 39.2MPa 84.3％ Example 3 44.8MPa 91.5％ Comparative Example 4 40.1MPa 89.7％ Comparative Example 1 44.2MPa 73.6％ Comparative Example 5 39.8MPa 89.5％

[0081] From the comparison of the experimental data of Examples 1 to 3 and Comparative Examples 1 to 5 in Table 1, it can be found that the dynamically cross-linked self-repairing electromagnetic shielding material prepared in the present invention has good tensile strength and self-repairing performance.

[0082] By comparing the data of Examples 1 to 3 and Comparative Example 1, it can be found that the repair rates of Examples 1 to 3 are high, which shows that the self-repairing polyurethane is prepared by polymerization with cystamine. The disulfide bond in cystamine can make the molecular backbone of the self-repairing polyurethane have a good self-repairing effect, thereby improving the overall self-repairing performance.

[0083] By comparing the data of Examples 1 to 3 and Comparative Example 2, it can be found that the tensile strength and repair rate of Examples 1 to 3 are high, indicating that the self-healing polyurethane is prepared by polymerization using 2,5-diaminomethylfuran. 2,5-diaminomethylfuran can cross-link with maleamide silicone oil and maleamide groups on modified magnetic-coated graphene oxide through a thermal reversible cycloaddition reaction to form a cross-linked network structure, thereby improving the tensile strength and being able to self-heal through thermal reversible cycloaddition.

[0084] By comparing the data of Examples 1 to 3 and Comparative Example 3, it can be found that the tensile strength and repair rate of Examples 1 to 3 are high, which shows that the addition of maleinamide silicone oil can increase the molar amount of maleinamide groups involved in self-repair. Secondly, maleinamide silicone oil has better fluidity and smaller molecular level than modified magnetic-coated graphene oxide, which can make the overall cross-linked structure denser, thereby improving the tensile strength and self-repair performance.

[0085] By comparing the data of Examples 1 to 3 and Comparative Examples 4 to 5, it can be found that the tensile strength and repair rate of Examples 1 to 3 are high, which shows that the modification of the magnetic-coated graphene oxide with a maleimide silane coupling agent improves the dispersibility of the magnetic-coated graphene oxide, exerts a better tensile strength enhancement effect, and introduces maleimide groups that can participate in cross-linking, thereby improving the tensile strength and self-healing performance.

[0086] Test Example 2

[0087] Flame retardant performance test

[0088] Flame retardancy test method: The dynamically cross-linked self-healing electromagnetic shielding materials prepared in each embodiment and comparative example were tested according to GB / T 2406.2. The results are shown in Table 2.

[0089] Table 2

[0090] Limiting oxygen index Limiting oxygen index Example 1 36.9％ Comparative Example 2 37.1％ Example 2 37.1％ Comparative Example 3 30.8％ Example 3 37.4％ Comparative Example 4 35.9％ Comparative Example 1 37.2％ Comparative Example 5 36.3％

[0091] From the comparison of the experimental data of Examples 1 to 3 and Comparative Examples 1 to 5 in Table 2, it can be found that the dynamically cross-linked self-repairing electromagnetic shielding material prepared in the present invention has good flame retardant properties.

[0092] By comparing the data of Examples 1 to 3 and Comparative Example 3, it can be found that the limiting oxygen index of Examples 1 to 3 is high, which shows that the addition of maleimide silicone oil generates a silicon-oxygen and silicon-carbon composite layer under high temperature, thereby playing the role of heat insulation, oxygen isolation and prevention of harmful gas escape, thereby improving the flame retardant effect.

[0093] By comparing the data of Examples 1 to 3 and Comparative Examples 4 to 5, it can be found that the limiting oxygen index of Examples 1 to 3 is high, which shows that the modification of the magnetic-coated graphene oxide with a maleimide silane coupling agent improves the dispersibility of the magnetic-coated graphene oxide, so that the magnetic-coated graphene oxide has a better combustion barrier effect, thereby improving the limiting oxygen index.

[0094] Test Example 3

[0095] Electromagnetic shielding performance test

[0096] Electromagnetic shielding performance testing method: The shielding effectiveness of carbon black-based electromagnetic shielding composites was tested using an Agilent 4396B vector network impedance spectrum analyzer and a far-field shielding effectiveness tester. The test frequency was 1.8 GHz, and the specimen size was a small disc with a thickness of 2 mm and a diameter of 15 mm. The results are shown in Table 3.

[0097] Table 3

[0098] Shielding efficiency Shielding efficiency Example 1 18.3dB Comparative Example 2 18.6dB Example 2 18.6dB Comparative Example 3 18.4dB Example 3 18.8dB Comparative Example 4 17.0dB Comparative Example 1 18.5dB Comparative Example 5 10.7dB

[0099] From the comparison of the experimental data of Examples 1 to 3 and Comparative Examples 1 to 5 in Table 3, it can be found that the dynamically cross-linked self-repairing electromagnetic shielding material prepared in the present invention has good electromagnetic shielding performance.

[0100] By comparing the data of Examples 1 to 3 and Comparative Example 3, it can be found that the limiting oxygen index of Example 4 is high, which shows that the modification of the magnetic-coated graphene oxide with a maleimide silane coupling agent improves the dispersibility of the magnetic-coated graphene oxide, so that the magnetic-coated graphene oxide exerts better electromagnetic shielding performance, thereby improving the electromagnetic shielding performance.

[0101] By comparing the data of Examples 1 to 3 and Comparative Example 3, it can be found that the limiting oxygen index of Example 5 is high, which shows that the graphene oxide has electromagnetic dual functions after magnetic coating and can effectively capture incident electromagnetic waves, thereby improving the electromagnetic shielding performance.

[0102] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above and that the invention can be embodied in other specific forms without departing from the spirit or essential characteristics of the invention. Therefore, the embodiments should be considered in all respects as illustrative and non-restrictive, and the scope of the invention is defined by the appended claims, not the foregoing description, and all variations within the meaning and range of equivalents of the claims are intended to be encompassed therein. Any reference in a claim should not be construed as limiting the claim to which it relates.

Claims

1. A dynamically cross-linked self-repairing electromagnetic shielding material, characterized in that: The composition comprises the following components by weight: 100 parts of self-repairing polyurethane, 20-25 parts of maleamide-based silicone oil, and 8-10 parts of modified magnetically coated graphene oxide; The self-repairing polyurethane is prepared by polymerization of polypropylene glycol, cystamine, 2,5-diaminomethylfuran, and 4,4'-diphenylmethane diisocyanate; The modified magnetically coated graphene oxide is prepared by forming a magnetic coating layer on the surface of the graphene oxide with ferrous sulfate and cobalt chloride, and then treating the surface of the magnetic coating layer with a maleimide silane coupling agent.

2. The dynamic cross-linked self-repairing electromagnetic shielding material according to claim 1, characterized in that: The maleamide silicone oil is prepared by reacting maleic anhydride and amino silicone oil.

3. A method for preparing a dynamically cross-linked self-repairing electromagnetic shielding material, characterized in that: The method comprises the following preparation steps: (1) Weigh the reaction raw materials according to the ratio of hydroxyl group molar amount in polypropylene glycol, amino group molar amount in cystamine, amino group molar amount in 2,5-diaminomethylfuran, and isocyanate molar amount in 4,4'-diphenylmethane diisocyanate of 1:0.6:0.6:2.2, vacuum dry the polypropylene glycol at 100-120℃ for 30-40min, then add 4,4'-diphenylmethane diisocyanate at 70-80℃ in a nitrogen atmosphere, stir for 40-50min, and then add 4,4'-diphenylmethane diisocyanate by mass. 0.003-0.004 times of dibutyltin dilaurate was added, and the mixture was stirred and reacted for 60-80 minutes to obtain a prepolymer; the prepolymer and N,N-dimethylformamide were mixed uniformly at a mass ratio of 1:10-15, and cystamine and 2,5-diaminomethylfuran were added at a uniform rate within 30 minutes under stirring conditions at 0°C. After the addition, the mixture was stirred and reacted for 20-30 minutes, the temperature was raised to 80-90°C, the mixture was stirred and reacted for 2-3 hours, and vacuum dried at 70-80°C for 20-24 hours to obtain a self-healing polyurethane; (2) Maleic anhydride and toluene are mixed uniformly in a mass ratio of 1:15-20 to prepare a maleic anhydride solution; γ-aminopropyltriethoxysilane and toluene in a mass ratio of 1:2.5-3 are mixed uniformly and added to the maleic anhydride solution at a uniform rate within 10-12 minutes. After the addition is completed, the mixture is stirred and reacted at room temperature for 40-60 minutes. Then, zinc chloride in an amount equal to the mass of maleic anhydride is added, the temperature is raised to 80-90°C, the mixture is stirred and reacted for 4-6 hours, and vacuum dried at 30-40°C for 20-24 hours to prepare a maleic amide silane coupling agent; the above process is repeated for amino silicone oil to prepare maleic amide silicone oil; (3) The metal ion mixture and the graphene oxide dispersion are mixed in a mass ratio of 1:2-3, ultrasonically dispersed at room temperature for 80-90 minutes in a nitrogen atmosphere, and then heated to 80-90°C. A hydrazine hydrate mixture of 0.5-0.6 times the mass of the metal ion mixture is added at a uniform rate within 20-30 minutes. After the addition is completed, the mixture is stirred and reacted for 6-8 hours. The mixture is collected by magnetic decantation and washed with pure water for 3-5 times. The mixture is vacuum dried at 70-80°C for 20-24 hours to obtain magnetically coated graphene oxide; maleimide silane coupling agent, pure water and anhydrous ethanol are mixed in a mass ratio of 1:10-12:1, the pH is adjusted to 10 with tetraethylammonium hydroxide, stirred at room temperature for 10-15 minutes, and then the magnetically coated graphene oxide is added. The stirring reaction is continued for 60-80 minutes, centrifuged, and vacuum dried at 70-80°C for 20-24 hours to obtain modified magnetically coated graphene oxide. (4) Weigh 100 parts of self-healing polyurethane, 20-25 parts of maleamide silicone oil, and 8-10 parts of modified magnetically coated graphene oxide by mass; place the self-healing polyurethane in an internal mixer, and mix at 180-190°C and 30 r / min for 25-30 minutes, then add maleamide silicone oil and modified magnetically coated graphene oxide and continue mixing for 8-10 minutes, then put it into a mold, press at 180-190°C and 8-10 MPa for 10-12 minutes, keep the pressure constant, cool naturally to room temperature, and then release the pressure to obtain a dynamic cross-linked self-healing electromagnetic shielding material.

4. The method for preparing a dynamically cross-linked self-repairing electromagnetic shielding material according to claim 3, characterized in that: The preparation method of the cystamine in step (1) comprises the following steps: uniformly mixing cystamine dihydrochloride and pure water in a mass ratio of 1:10-15, adding potassium hydroxide in an amount of 0.7-0.8 times the mass of cystamine dihydrochloride, stirring and reacting for 10-12 minutes, extracting with dichloromethane 3-5 times, adding dichloromethane in an amount of 8-10 times the mass of cystamine dihydrochloride each time, combining the extracted organic phases, drying with anhydrous sodium sulfate, filtering, and standing at 0.1-0.3 kPa and 20-30° C. for 6-8 hours to prepare the cystamine.

5. The method for preparing a dynamically cross-linked self-repairing electromagnetic shielding material according to claim 3, characterized in that: The model of the polypropylene glycol in step (1) is PPG2000.

6. The method for preparing a dynamically cross-linked self-repairing electromagnetic shielding material according to claim 3, characterized in that: The model of the amino silicone oil in step (2) is N323.

7. The method for preparing a dynamically cross-linked self-repairing electromagnetic shielding material according to claim 3, characterized in that: The graphene oxide dispersion in step (3) is prepared by mixing graphene oxide and pure water in a mass ratio of 1:500-600 and ultrasonically dispersing for 30-40 minutes; the metal ion mixture is prepared by adding ferrous sulfate and cobalt chloride in a molar ratio of 1:1 to pure water with a mass of 30-40 times that of ferrous sulfate and ferrous sulfate, and mixing them uniformly; the hydrazine hydrate mixture is prepared by mixing sodium hydroxide and hydrazine hydrate in a mass ratio of 1:10-15.