A high-temperature-resistant polymer-based electromagnetic shielding composite material and a preparation method thereof

Abstract

The application discloses a kind of high-temperature-resistant polymer-based electromagnetic shielding composite material and preparation method thereof, in-situ growth polypyrrole on the surface of magnetic metal powder, obtain composite filler with good magnetic performance and conductivity, then the obtained composite filler is introduced into polyimide matrix, and high-performance electromagnetic shielding material is obtained.The material obtained by the application has good electromagnetic shielding performance, and the electromagnetic shielding performance in L wave band can reach up to 39dB, and the shielding efficiency in X wave band can reach up to 35dB, and good electromagnetic shielding characteristics are exhibited in low-frequency wave band and high-frequency wave band.The lowest thermal decomposition temperature of the material obtained by the application is 500 DEG C, and it can be used in 350 DEG C environment for a long time, and it has important value in the field of polymer-based high-temperature-resistant electromagnetic shielding materials.

Description

Technical Field

[0001] This invention belongs to the field of electromagnetic shielding composite material technology, and relates to a high-temperature resistant polymer-based electromagnetic shielding composite material and its preparation method. Background Technology

[0002] Magnetic metal powders are a crucial type of electromagnetic shielding material, primarily referring to microparticles of Fe, Co, Ni metals and their alloys. These powders possess high imaginary permeability and high magnetic loss tangent, absorbing and attenuating electromagnetic waves mainly through mechanisms such as hysteresis loss, eddy current loss, and natural resonance loss. Generally, eliminating electromagnetic interference and protecting against electromagnetic radiation can be achieved through both reflection and absorption of electromagnetic waves. For magnetic materials with high permeability, absorption shielding plays a primary role; for materials with high conductivity, reflection shielding is the main function. Magnetic materials generally provide highly efficient shielding against low-frequency electromagnetic waves, while conductive materials provide highly efficient shielding against high-frequency electromagnetic waves.

[0003] Therefore, to achieve efficient multi-band shielding for both low and high frequencies, combining magnetic and conductive materials is an ideal method. Polypyrrole, a common conductive polymer, possesses advantages such as high conductivity, ease of processing, and corrosion resistance, making it a promising candidate for electromagnetic shielding materials. However, there are no publicly available reports on preparing composite fillers with both magnetic and conductive properties using polypyrrole and magnetic metal microparticles, followed by the fabrication of polyimide-based high-temperature resistant electromagnetic shielding composite materials. Summary of the Invention

[0004] This invention relates to a high-temperature resistant polymer-based electromagnetic shielding composite material and its preparation method, obtaining a composite material with good electromagnetic shielding performance in both the L-band and X-band, and the obtained material has excellent high-temperature resistance.

[0005] The present invention is achieved through the following technical solution.

[0006] This invention provides a high-temperature resistant polymer-based electromagnetic shielding composite material and its preparation method, comprising the following process: polypyrrole coating magnetic metal microparticle composite filler, the composite filler being filled into polyimide to form a high-temperature resistant polymer-based electromagnetic shielding composite material.

[0007] A high-temperature resistant polymer-based electromagnetic shielding composite material and its preparation method, the preparation method comprising the following steps:

[0008] Step 1: Disperse 50g of magnetic metal particles and 50-80mL of pyrrole monomer in 100-150mL of ethanol aqueous solution (volume ratio 1:1) to prepare a mixed solution. Then add 20-30g of ammonium persulfate to the mixed solution and react with mechanical stirring at 0℃ ice bath for 12-20h. After that, filter, wash and vacuum dry the product at 50-60℃ to obtain polypyrrole-coated magnetic metal particle composite filler.

[0009] Step 2: Add 4,4-diaminodiphenyl ether and aromatic dianhydride to dimethylformamide at a molar ratio of 1.0 to 1.5 and stir mechanically at 45 to 55°C until fully dissolved. Then, heat to 70 to 80°C and react for 4 to 5 hours to obtain a polyamic acid solution.

[0010] Step 3: Slowly add 10-15g of acetic anhydride solution to 100mL of polyamic acid solution obtained in Step 2, and add 10-15g of polypyrrole-coated magnetic metal microparticle composite filler obtained in Step 1. Stir evenly and cool to room temperature. Then, use a coater to coat the mold.

[0011] Step 4: Place the mixture obtained in Step 3 and the mold together in a vacuum oven and dehydrate and imide at 180-250°C to form a high-temperature resistant polymer-based electromagnetic shielding composite material.

[0012] Preferably, the magnetic metal particles include one or more of carbonyl Fe powder, carbonyl Ni powder, and carbonyl Co powder.

[0013] Preferably, the aromatic dianhydride comprises one or more of pyromellitic dianhydride, 3,3',4,4'-benzophenone tetracarboxylic dianhydride, 3,3',4,4'-diphenyl methyl ether tetracarboxylic dianhydride, 2,2-bis(3,4-phthalic anhydride)hexafluoropropane, or 1,3-bis(3,4-phthalic anhydride)hexafluoropropane. The material obtained by this invention exhibits good electromagnetic shielding performance in both low-frequency and high-frequency bands, and also possesses excellent high-temperature resistance.

[0014] The composite material obtained by this invention not only has good electromagnetic shielding performance in both low-frequency and high-frequency bands, but also has excellent high-temperature resistance and can be used for a long time at 350°C, demonstrating good adaptability to extreme environments and further broadening the application of polymer-based high-performance electromagnetic shielding materials.

[0015] The beneficial effects of this invention are:

[0016] (1) The material obtained in this invention exhibits good electromagnetic shielding performance in both the L-band and X-band. The electromagnetic shielding performance in the L-band can reach up to 39 dB, and the shielding effectiveness in the X-band can reach up to 35 dB, demonstrating multi-band electromagnetic shielding characteristics. A composite filler is obtained by combining highly conductive polypyrrole with magnetic metal particles using an in-situ polymerization method. The magnetic metal particles are beneficial for the absorption and attenuation of low-frequency electromagnetic waves, mainly due to magnetic loss; the highly conductive polypyrrole is beneficial for the absorption and loss of high-frequency electromagnetic waves, mainly due to dielectric loss; the difference in conductivity between the polypyrrole-coated magnetic metal particles creates an interface effect at the interface, forming a capacitor-like structure, which is beneficial for the absorption and loss of electromagnetic waves within the material.

[0017] (2) This invention uses high-performance polyimide as the matrix to obtain a composite material with excellent high-temperature resistance. Polyimide, due to the presence of an imide ring in its molecular structure, possesses excellent high-temperature resistance, self-flame retardancy, and corrosion resistance, making it one of the best-performing organic polymer materials. Therefore, this invention uses polyimide as the matrix to prepare a high-temperature resistant electromagnetic shielding composite material with a long-term operating temperature up to 350℃, which is of great significance for the application of high-temperature polymer-based shielding materials. Detailed Implementation

[0018] To provide a clearer understanding of the technical features of the present invention, the technical solution of the present invention will now be described in detail below, but this should not be construed as limiting the scope of implementation of the present invention. Example 1

[0019] (1) 50g of carbonyl Fe powder and 50mL of pyrrole monomer were dispersed in 100mL of ethanol aqueous solution to prepare a mixed solution. Then, 20g of ammonium persulfate was added to the mixed solution. After mechanical stirring for 12h under 0℃ ice bath conditions, the resulting product was filtered, washed and vacuum dried at 60℃ to obtain polypyrrole-coated magnetic metal microparticle composite filler.

[0020] (2) 4,4-Diaminodiphenyl ether and pyromellitic dianhydride were added to dimethylformamide at a molar ratio of 1.2 and dissolved completely by mechanical stirring at 55°C. The mixture was then heated to 80°C and reacted for 5 hours to obtain a polyamic acid solution.

[0021] (3) Slowly add 15g of acetic anhydride solution to the 100mL polyamic acid solution obtained in step (2), and add 10g of polypyrrole-coated magnetic metal microparticle composite filler obtained in step (1). Stir evenly and cool to room temperature. Then coat the mold with a coating tool.

[0022] (4) The mixture obtained in step (3) is placed together with the mold in a vacuum oven and dehydrated and imidized at 220°C to form a high-temperature resistant polymer-based electromagnetic shielding composite material. Example 2

[0023] (1) 50g of carbonyl Ni powder and 50mL of pyrrole monomer were dispersed in 100mL of ethanol aqueous solution to prepare a mixed solution. Then, 20g of ammonium persulfate was added to the mixed solution. After mechanical stirring for 12h under 0℃ ice bath conditions, the resulting product was filtered, washed and vacuum dried at 60℃ to obtain polypyrrole-coated magnetic metal microparticle composite filler.

[0024] (2) 4,4-Diaminodiphenyl ether and pyromellitic dianhydride were added to dimethylformamide at a molar ratio of 1.2 and dissolved completely by mechanical stirring at 55°C. The mixture was then heated to 80°C and reacted for 5 hours to obtain a polyamic acid solution.

[0025] (3) Slowly add 15g of acetic anhydride solution to the 100mL polyamic acid solution obtained in step (2), and add 10g of polypyrrole-coated magnetic metal microparticle composite filler obtained in step (1). Stir evenly and cool to room temperature. Then coat the mold with a coating tool.

[0026] (4) The mixture obtained in step (3) is placed together with the mold in a vacuum oven and dehydrated and imidized at 220°C to form a high-temperature resistant polymer-based electromagnetic shielding composite material. Example 3

[0027] (1) 50g of carbonyl Co powder and 50mL of pyrrole monomer were dispersed in 100mL of ethanol aqueous solution to prepare a mixed solution. Then, 20g of ammonium persulfate was added to the mixed solution. After mechanical stirring for 12h under 0℃ ice bath conditions, the resulting product was filtered, washed and vacuum dried at 60℃ to obtain polypyrrole-coated magnetic metal microparticle composite filler.

[0028] (2) 4,4-Diaminodiphenyl ether and pyromellitic dianhydride were added to dimethylformamide at a molar ratio of 1.2 and dissolved completely by mechanical stirring at 55°C. The mixture was then heated to 80°C and reacted for 5 hours to obtain a polyamic acid solution.

[0029] (3) Slowly add 15g of acetic anhydride solution to the 100mL polyamic acid solution obtained in step (2), and add 10g of polypyrrole-coated magnetic metal microparticle composite filler obtained in step (1). Stir evenly and cool to room temperature. Then coat the mold with a coating tool.

[0030] (4) The mixture obtained in step (3) is placed together with the mold in a vacuum oven and dehydrated and imidized at 220°C to form a high-temperature resistant polymer-based electromagnetic shielding composite material. Example 4

[0031] (1) 50g of carbonyl Ni powder and 50mL of pyrrole monomer were dispersed in 100mL of ethanol aqueous solution to prepare a mixed solution. Then, 20g of ammonium persulfate was added to the mixed solution. After mechanical stirring for 12h under 0℃ ice bath conditions, the resulting product was filtered, washed and vacuum dried at 60℃ to obtain polypyrrole-coated magnetic metal microparticle composite filler.

[0032] (2) 4,4-diaminodiphenyl ether and 3,3',4,4'-benzophenone tetracarboxylic dianhydride were added to dimethylformamide at a molar ratio of 1.2 and dissolved completely by mechanical stirring at 55°C. The mixture was then heated to 80°C and reacted for 5 hours to obtain a polyamic acid solution.

[0033] (3) Slowly add 15g of acetic anhydride solution to the 100mL polyamic acid solution obtained in step (2), and add 15g of polypyrrole-coated magnetic metal microparticle composite filler obtained in step (1). Stir evenly and cool to room temperature. Then use a coater to coat the mold.

[0034] (4) The mixture obtained in step (3) is placed together with the mold in a vacuum oven and dehydrated and imidized at 220°C to form a high-temperature resistant polymer-based electromagnetic shielding composite material. Example 5

[0035] (1) 50g of carbonyl Ni powder and 50mL of pyrrole monomer were dispersed in 100mL of ethanol aqueous solution to prepare a mixed solution. Then, 20g of ammonium persulfate was added to the mixed solution. After mechanical stirring for 12h under 0℃ ice bath conditions, the resulting product was filtered, washed and vacuum dried at 60℃ to obtain polypyrrole-coated magnetic metal microparticle composite filler.

[0036] (2) 4,4-Diaminodiphenyl ether and pyromellitic dianhydride were added to dimethylformamide at a molar ratio of 1.2 and dissolved completely by mechanical stirring at 55°C. The mixture was then heated to 80°C and reacted for 5 hours to obtain a polyamic acid solution.

[0037] (3) Slowly add 15g of acetic anhydride solution to the 100mL polyamic acid solution obtained in step (2), and add 15g of polypyrrole-coated magnetic metal microparticle composite filler obtained in step (1). Stir evenly and cool to room temperature. Then use a coater to coat the mold.

[0038] (4) The mixture obtained in step (3) is placed together with the mold in a vacuum oven and dehydrated and imidized at 220°C to form a high-temperature resistant polymer-based electromagnetic shielding composite material.

[0039] Table 1 shows the average electromagnetic shielding energy (SE) parameters and thermal decomposition temperature (Td) of the high-temperature resistant polymer-based electromagnetic shielding composite materials prepared in Examples 1-5 in the L-band (1-2 GHz) and X-band (8-12 GHz). The composite materials obtained in Examples 1-5 exhibit good low-frequency electromagnetic shielding with an SE between 30 dB and 39 dB in the L-band; and good high-frequency electromagnetic shielding with an SE between 28 dB and 35 dB in the X-band. This indicates that the materials obtained in this invention exhibit good electromagnetic shielding performance in both low-frequency and high-frequency bands. The thermal decomposition temperature of the composite materials obtained in Examples 1-5 is above 510 °C, indicating that the composite materials obtained in this invention have excellent high-temperature resistance.

[0040] Table 1. Electromagnetic shielding and thermal performance parameters of the composite materials obtained in the examples

[0041]

Claims

1. A method for preparing a high temperature resistant polymer-based electromagnetic shielding composite material, characterized in that, Includes the following steps: Step 1: Disperse 50g of magnetic metal microparticles and 50-80mL of pyrrole monomer in 100-150mL of ethanol-water solution to prepare a mixed solution. Then add 20-30g of ammonium persulfate to the mixed solution and react with mechanical stirring at 0℃ in an ice bath for 12-20h. After that, filter, wash and vacuum dry the product at 50-60℃ to obtain polypyrrole-coated magnetic metal microparticle composite filler. The ethanol-water solution is a mixture of ethanol and water with a volume ratio of 1:

1. Step 2: Add 4,4-diaminodiphenyl ether and aromatic dianhydride to dimethylformamide at a molar ratio of 1.0 to 1.5 and stir mechanically at 45 to 55°C until fully dissolved. Then, heat to 70 to 80°C and react for 4 to 5 hours to obtain a polyamic acid solution. Step 3: Slowly add 10-15g of acetic anhydride solution to 100mL of polyamic acid solution obtained in Step 2, and add 10-15g of polypyrrole-coated magnetic metal microparticle composite filler obtained in Step 1. Stir evenly and cool to room temperature. Then, use a coater to coat the mold. Step 4: Place the mixture obtained in Step 3 and the mold together in a vacuum oven and dehydrate and imide at 180-250°C to form a high-temperature resistant polymer-based electromagnetic shielding composite material. The magnetic metal particles are carbonyl Fe powder, carbonyl Ni powder, or carbonyl Co powder; The aromatic dianhydride is pyromellitic dianhydride or 3,3',4,4'-benzophenone tetracarboxylic dianhydride.

2. A high-temperature resistant polymer-based electromagnetic shielding composite material prepared by the method of claim 1.

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