Wave-absorbing prepreg, method for preparing the same and use thereof

Abstract

The application discloses a wave-absorbing prepreg and a preparation method thereof. The wave-absorbing prepreg comprises two layers of wave-absorbing adhesive films, two layers of wave-transparent adhesive films and one layer of a fiber fabric, and is sequentially the wave-absorbing adhesive film layer, the wave-transparent adhesive film layer, the fiber fabric layer, the wave-transparent adhesive film layer and the wave-absorbing adhesive film layer. The method for preparing the wave-absorbing prepreg provided by the application is characterized in that the wave-transparent resin film is first compounded with the fiber fabric, and then the wave-absorbing adhesive film is compounded with the prepreg fabric, so that the wave-absorbing prepreg with the oriented arrangement of the absorbing agent is obtained. The wave-absorbing prepreg provided by the application can reduce the reflectivity of the wave-absorbing composite material in the frequency range of 1-18 GHz, and has excellent wave-absorbing performance.

Description

Technical Field

[0001] The invention relates to a wave-absorbing prepreg and a preparation method and application thereof. Background Art

[0002] Absorbing materials absorb and attenuate incident electromagnetic waves by converting electromagnetic wave energy into heat or other forms of energy dissipation. Absorbing materials have been widely used in various fields, such as electromagnetic interference protection in communications and human electromagnetic protection. Resin-based absorbing materials have become a key material for stealth applications in the aerospace industry due to their simple processing, strong designability, and ability to form large, integral surfaces.

[0003] The performance of absorbing materials depends on a variety of factors, including the absorber type, such as magnetic absorbers, carbon-based absorbers, and alloy powders. The performance of absorbing materials is also related to the absorber's morphology, such as spherical absorbers, sheet absorbers, and rod-shaped absorbers. Furthermore, the performance of absorbing materials is also related to the dispersion state of the absorber in the system, such as its uniformity and the degree of alignment of the absorber within the system. Generally, the orientation of sheet-shaped absorbers within the system helps to improve the overall magnetic loss of the material.

[0004] Absorbing prepreg is an absorbing material that can be integrally molded with structural materials. Compared to conventional coating materials (which are formed using a spray coating process), the integrated co-curing process for absorbing prepreg is simpler and more efficient. Absorbing prepreg is typically prepared using a hot melt method, which involves first applying an absorbing resin to form a film using a coater, and then laminating the film with a fiber fabric to produce the absorbing prepreg. However, its absorbing performance is limited. Summary of the Invention

[0005] To further optimize the absorbing performance of absorbing prepregs and broaden the selection of absorbing prepregs, the present invention provides a absorbing prepreg and a method for preparing the same. The method comprises first laminating a transparent resin film with a fiber fabric, allowing the resin to fill the interstices of the fabric to form a prepreg. The prepreg is then laminarized with an absorbing adhesive film to produce an absorbing prepreg with oriented absorbents. This solves the problem of random absorbent alignment caused by the flow of the absorbing resin during the lamination process, thereby improving the absorbing performance of the absorbing prepreg.

[0006] As one aspect of the present invention, it relates to an absorbing prepreg, comprising two layers of absorbing adhesive films, two layers of transparent adhesive films and a layer of fiber fabric, which are the absorbing adhesive film layer, the transparent adhesive film layer, the fiber fabric layer, the transparent adhesive film layer and the absorbing adhesive film layer in sequence.

[0007] In a specific embodiment, the fiber fabric is one of a quartz fiber fabric, an aramid fiber fabric, and a basalt fiber fabric, or a mixed fabric of any combination thereof; the thickness of the fiber fabric is 0.05-0.1 mm.

[0008] As another aspect of the present application, a method for preparing a wave-absorbing prepreg is provided, the method comprising:

[0009] a) mixing a base resin, a curing agent, and an absorber at 60-85°C to obtain a crude mixed wave-absorbing resin; and then refining the crude mixed wave-absorbing resin at 60-85°C to obtain a refined mixed wave-absorbing resin;

[0010] b) mixing a base resin and a curing agent at 60-75°C to obtain a crude mixed resin; and then refining the crude mixed wave-absorbing resin at 65-75°C to obtain a refined mixed wave-absorbing resin;

[0011] c) coating the refined mixed wave-absorbing resin obtained in step a) on a release paper at a film coating temperature of 75-95°C to obtain a wave-absorbing film; and coating the refined mixed wave-absorbing resin obtained in step b) on a release paper at a film coating temperature of 75-95°C to obtain a wave-absorbing film;

[0012] d) combining a fiber fabric between two layers of the wave-absorbing film at a combining temperature of 65-85°C to obtain a primary prepreg fabric, and then curing the primary prepreg fabric at 70-90°C to obtain a prepreg fabric.

[0013] e) combining the prepreg fabric between two layers of the wave-absorbing film at a combining temperature of 65-80°C to obtain a wave-absorbing prepreg, the wave-absorbing prepreg comprising, from top to bottom, the wave-absorbing film, the wave-absorbing film, the fiber fabric, the wave-absorbing film, and the wave-absorbing film.

[0014] In a specific embodiment, in step a), the mass ratio of the absorber, the base resin, and the curing agent is 5-13.5:3-4:0-1.

[0015] In a specific embodiment, in step b), the mass ratio of the base resin and the curing agent is 3-4:1.

[0016] In a specific embodiment, the absorber is one of a flaky carbonyl iron, a flaky iron-silicon-aluminum, a flaky iron-silicon-chromium, a flaky iron-silicon-nickel, and a chopped carbon fiber, or any combination thereof, and the particle size of the absorber is 5-100 microns.

[0017] In a specific embodiment, the base resin is one or any combination of epoxy resin, cyanate ester resin, bismaleimide resin and phenolic resin; and the curing agent is one or any combination of dicyandiamide, diallyl bisphenol A, phthalic anhydride, p-phenylenediamine and p-toluene sulfonic acid.

[0018] In a specific embodiment, the fiber fabric is one or any combination of a mixed fabric of quartz fiber fabric, aramid fiber fabric and basalt fiber fabric, and the thickness of the fiber fabric is 0.05-0.1 mm.

[0019] In a specific embodiment, the thickness of the wave-transparent adhesive film is 40%-60% of the thickness of the fiber fabric; and the thickness of the wave-absorbing adhesive film is 120%-166.7% of the thickness of the fiber fabric.

[0020] As another aspect of the present application, it relates to the use of the wave-absorbing prepreg in a wave-absorbing device.

[0021] Compared with the prior art, the present application has at least the following advantages:

[0022] (1) The method for preparing the wave-absorbing prepreg provided by the present application first uses a wave-transparent adhesive film to be combined with a fiber fabric, and then uses a wave-absorbing adhesive film to be combined, thereby improving the bonding force between the resin and the fiber and improving the process reliability of the wave-absorbing prepreg.

[0023] (2) The method for preparing the wave-absorbing prepreg provided by the present application avoids the disorderly orientation of the absorber caused by the flow of the wave-absorbing resin in the fiber gap, thereby improving the wave-absorbing performance of the wave-absorbing prepreg. BRIEF DESCRIPTION OF DRAWINGS

[0024] Figure 1 Figure 1 is a schematic diagram of the preparation process of the wave-absorbing prepreg according to the present application;

[0025] Figure 2 Figure 5 is a cross-sectional micrograph of the cyanate ester wave-absorbing composite prepared in Example 3;

[0026] Figure 3 Figure 6 is a cross-sectional micrograph of the cyanate ester wave-absorbing composite prepared in Comparative Example 3;

[0027] In the pictures, the relatively large and continuous black area is the fabric, denoted as 1; the white area is the absorber, denoted as 2; and the relatively scattered black area existing in the absorber gap is the resin, denoted as 3. DETAILED DESCRIPTION

[0028] The inventors prepared a microwave-absorbing epoxy resin with reference to CN 113801437 B, and also prepared a microwave-absorbing cyanate ester resin and a microwave-absorbing cyanate ester resin composite with reference to CN 113755013 B. However, during the preparation process, when the microwave-absorbing adhesive film and fiber fabric are composited, the resin will flow and fill the gaps in the fiber fabric, and the absorbent will also be randomly arranged as the resin flows, reducing the microwave-absorbing effect.

[0029] Referring to CN 118744542 A, the inventors prepared a low-frequency absorbing prepreg for the P and L bands, using a secondary hot pressing method to improve the orientation of the absorber. However, the effect of the secondary molding is affected by multiple factors such as temperature, speed, pressure, and the fabric itself, and it cannot solve the problem of resin flowing into the gaps, resulting in limited effect.

[0030] Since the above existing technologies cannot meet the inventor's expectations, the inventor has made the present invention after further research and development. The method provided by the present invention can prepare a microwave absorbing prepreg capable of maintaining the orientation of the absorber.

[0031] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions of the present invention. Obviously, the embodiments described are part of the embodiments of the present invention, but not all of them. 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.

[0032] Example 1:

[0033] A microwave absorbing prepreg and a preparation method thereof, comprising the following steps:

[0034] S1. Preparation of a finely mixed absorbing resin: A mixed absorbent, bisphenol A epoxy resin E51, and dicyandiamide (curing agent) in a mass ratio of 8:3:1 were added to a three-roll mill. The mixed absorbent consisted of 45 μm flake sendust and 5 μm chopped carbon fibers in a mass ratio of 4:1. The mixture was then mixed in a GS-100 three-roll mill at 60°C for 30 minutes to obtain a coarsely mixed absorbing resin. The coarsely mixed absorbing resin was then milled and finely mixed in an SXHJ-100 dual planetary mixer to obtain a finely mixed absorbing resin. The milling temperature was 60°C, the milling time was 45 minutes, and the rotor speed was 25 rpm.

[0035] S2. Preparation of a finely mixed wave-transmitting resin: Add bisphenol A epoxy resin E44 and dicyandiamide (curing agent) in a mass ratio of 3:1 to a three-roll mill and mix at 60°C for 30 minutes using a GS-100 three-roll mill to obtain a coarsely mixed wave-transmitting resin. This coarsely mixed wave-transmitting resin is then milled and fine-mixed using an SXHJ-100 dual planetary mixer to obtain a finely mixed wave-transmitting resin. The milling temperature is 65°C, the milling time is 30 minutes, and the rotor speed is 40 rpm.

[0036] S3. Preparation of film: Use a coating machine to coat the finely mixed absorbing resin obtained in step S1 on the release paper at a coating temperature of 75°C and a coating speed of 3 m / min to obtain a 0.08 mm thick absorbing film; use a coating machine to coat the finely mixed transparent resin obtained in step S2 on the release paper at a coating temperature of 75°C and a coating speed of 4 m / min to obtain a 0.03 mm thick transparent film.

[0037] S4. Preparation of preimpregnated fabric: Select 0.06mm aramid fiber plain weave fabric, use a compounding machine, a compounding temperature of 65°C, and a compounding speed of 3m / min to compound the aramid fiber plain weave fabric between two layers of wave-transmitting adhesive film to obtain a primary preimpregnated fabric, and then maintain the primary preimpregnated fabric at 70°C for 0.5h (curing) to obtain a preimpregnated fabric.

[0038] S5. Preparation of absorbing prepreg: Using a compounding machine, the compounding temperature is 65℃, and the compounding speed is 3m / min. The prepreg fabric is compounded between two layers of absorbing films to obtain an absorbing prepreg composed of absorbing film, transparent film, aramid fiber plain fabric, transparent film and absorbing film from top to bottom. The process of preparing absorbing prepreg is as follows: Figure 1 .

[0039] The absorbing prepreg of this embodiment was used to prepare epoxy absorbing composites and perform performance tests:

[0040] Preparation of epoxy absorbing composites: The absorbing prepreg prepared in step S5 is used to prepare epoxy absorbing composites according to the following autoclave curing procedure: 4 layers of absorbing prepreg are laid flat on a flat tooling mold, wherein polytetrafluoroethylene cloth is laid on the flat tooling mold, and then a vacuum bag is assembled, which is composed of a vacuum bag film, a breathable felt, an isolation film, a peelable cloth, 4 layers of absorbing prepreg, polytetrafluoroethylene cloth and a flat tooling mold from top to bottom, one end of the vacuum tube is inserted into the vacuum bag film and fixed with sealing tape, and the sealing tape is used to seal along the edge of the vacuum bag film, and then a vacuum pump is connected. Vacuum is evacuated at room temperature with a vacuum degree of 0.085 MPa to form a preform. The preform was then placed in an autoclave, pressurized to 0.6 MPa, heated to 130°C at a rate of 1°C / min, kept warm for 2 hours, and cooled to below 60°C at a cooling rate of 1.5°C / min. The preform was then taken out of the autoclave. After the temperature of the preform dropped to room temperature, the vacuum bag, breathable felt, isolation film, peelable cloth and polytetrafluoroethylene cloth were removed to obtain an epoxy absorbing composite material consisting of four layers of absorbing prepreg cured. The average thickness of the epoxy absorbing composite material was 0.81 mm.

[0041] The epoxy absorbing composite material was processed into 500mm×500mm and 300mm×300mm flat plates. The vertical reflectivity of the samples was tested at 1-18GHz using a 1-18GHz bow method reflectivity tester. The test results are shown in Table 1.

[0042] As can be seen from Table 1, the epoxy absorbing composite material prepared in this embodiment has an average reflectivity absorption peak of -1.65 dB at 1-2 GHz, an average reflectivity absorption peak of -4.06 dB at 2-4 GHz, an average reflectivity absorption peak of -7.39 dB at 4-8 GHz, an average reflectivity absorption peak of -10.67 dB at 8-12 GHz, and an average reflectivity absorption peak of -5.51 dB at 12-18 GHz.

[0043] Example 2:

[0044] A microwave absorbing prepreg and a preparation method thereof, comprising the following steps:

[0045] S1. Preparation of a finely mixed absorbing resin: Add an absorbent, T-type bisphenol A resin, and diallyl bisphenol A (curing agent) in a mass ratio of 5:4:1 to a three-roll mill. The absorbent is 100 μm flake iron, silicon, and chromium. Mix for 30 minutes at 70°C using a GS-100 three-roll mill to obtain a coarsely mixed absorbing resin. The coarsely mixed absorbing resin is then milled and finely mixed using an SXHJ-100 dual planetary mixer to obtain a finely mixed absorbing resin. The milling temperature is 70°C, the milling time is 30 minutes, and the rotor speed is 15 rpm.

[0046] S2. Preparation of a finely mixed wave-transmitting resin: HVA-2 m-phenylene bismaleimide resin and p-phenylenediamine (curing agent) were added to a three-roll mill at a mass ratio of 4:1. Mixing was performed using a GS-100 three-roll mill at 70°C for 40 minutes to obtain a coarsely mixed wave-transmitting resin. This coarsely mixed wave-transmitting resin was then subjected to open-mixing and fine-mixing using an SXHJ-100 dual planetary mixer to obtain a finely mixed wave-transmitting resin. The open-mixing temperature was 65°C, the open-mixing time was 30 minutes, and the rotor speed was 35 rpm.

[0047] S3. Preparation of film: Use a coating machine to coat the finely mixed absorbing resin obtained in step S1 on the release paper at a coating temperature of 80°C and a coating speed of 2 m / min to obtain a 0.08 mm thick absorbing film; use a coating machine to coat the finely mixed transparent resin obtained in step S2 on the release paper at a coating temperature of 80°C and a coating speed of 3 m / min to obtain a 0.025 mm thick transparent film.

[0048] S4. Preparation of preimpregnated fabric: Select 0.05mm quartz fiber twill fabric, use a compounding machine, a compounding temperature of 70°C, and a compounding speed of 2m / min to compound the quartz fiber twill fabric between two layers of wave-transmitting adhesive film to obtain a primary preimpregnated fabric, and then maintain the primary preimpregnated fabric at 85°C for 0.5h (curing) to obtain a preimpregnated fabric.

[0049] S5. Preparation of absorbing prepreg: Using a compounding machine, the compounding temperature is 70℃, and the compounding speed is 2m / min. The prepreg fabric is compounded between two layers of absorbing films to obtain an absorbing prepreg composed of absorbing film, transparent film, quartz fiber twill fabric, transparent film and absorbing film from top to bottom. The process of preparing absorbing prepreg is as follows: Figure 1 .

[0050] The absorbing prepreg of this embodiment is used to prepare a double-stranded absorbing composite material and perform testing:

[0051] Preparation of double-layer absorbing composites: The absorbing prepreg prepared in step S5 is used to prepare double-layer absorbing composites according to the following autoclave curing procedure: 4 layers of absorbing prepreg are laid flat on a flat tooling mold, wherein polytetrafluoroethylene cloth is laid on the flat tooling mold, and then a vacuum bag is assembled, which is composed of a vacuum bag film, a breathable felt, an isolation film, a peelable cloth, 4 layers of absorbing prepreg, polytetrafluoroethylene cloth and a flat tooling mold from top to bottom. One end of the vacuum tube is inserted into the vacuum bag film and fixed with sealing tape. The sealing tape is used to seal along the edge of the vacuum bag film, and then a vacuum pump is connected. Vacuum is evacuated at room temperature with a vacuum degree of 0.085 MPa to form a preform. The preform was then placed in an autoclave, pressurized to 0.6 MPa, heated to 180°C at a rate of 1°C / min, kept warm for 1 hour, and then heated to 210°C and kept warm for 2 hours. The pressure was maintained and the preform was cooled to below 60°C at a cooling rate of 1.5°C / min. The preform was taken out of the autoclave, and after the temperature of the preform dropped to room temperature, the vacuum bag, breathable felt, isolation film, peelable cloth and polytetrafluoroethylene cloth were removed to obtain a BMI absorbing composite material cured from 4 layers of absorbing prepreg. The average thickness of the BMI absorbing composite material was 0.75 mm.

[0052] The above-mentioned double-stranded wave absorbing composite material was processed into 500mm×500mm and 300mm×300mm flat plates. The vertical reflectivity of the samples from 1 to 18 GHz was tested using a 1 to 18 GHz bow method reflectivity test equipment. The test results are shown in Table 1.

[0053] The average reflectivity absorption peak of the bismuth absorbing composite material prepared in this embodiment is -1.38 dB at 1-2 GHz, -3.96 dB at 2-4 GHz, -6.89 dB at 4-8 GHz, -9.75 dB at 8-12 GHz, and -5.42 dB at 12-18 GHz. The results are shown in Table 1.

[0054] Example 3:

[0055] A microwave absorbing prepreg and a preparation method thereof, comprising the following steps:

[0056] S1. Preparation of a finely mixed absorbing resin: Add an absorbent, bisphenol S cyanate ester resin, and phthalic anhydride (curing agent) in a mass ratio of 27:7:2 to a three-roll mill. The absorbent is 20 μm flake carbonyl iron. Mix the mixture using a GS-100 three-roll mill at 70°C for 30 minutes to obtain a coarsely mixed absorbing resin. The coarsely mixed absorbing resin is then milled and finely mixed using an SXHJ-100 dual planetary mixer to obtain a finely mixed absorbing resin. The milling temperature is 70°C, the milling time is 30 minutes, and the rotor speed is 25 rpm.

[0057] S2. Preparation of fine mixed wave-transparent resin: Bisphenol S cyanate resin and phthalic anhydride (curing agent) with a mass ratio of 7:2 were added to a three-roll mill, and mixed at 70°C for 30 min using a three-roll mill with a model of GS-100 to obtain a crude mixed wave-transparent resin. Then the crude mixed wave-transparent resin was refined using a double planetary mixer with a model of SXHJ-100 to obtain a fine mixed wave-transparent resin: the refining temperature was 70°C, the refining time was 30 min, and the rotor speed was 35 rpm.

[0058] S3. Preparation of adhesive film: the fine mixed wave-absorbing resin obtained in step S1 was coated on release paper using a film coater, the coating temperature was 85°C, the coating speed was 3 m / min, and a wave-absorbing adhesive film with a thickness of 0.12 mm was obtained; the fine mixed wave-transparent resin obtained in step S2 was coated on release paper using a film coater, the coating temperature was 85°C, the coating speed was 4 m / min, and a wave-transparent adhesive film with a thickness of 0.05 mm was obtained.

[0059] S4. Preparation of pre-impregnated fabric: a quartz aramid hybrid fiber plain fabric with a thickness of 0.1 mm was selected, and the quartz aramid hybrid fiber plain fabric was compounded between two layers of wave-transparent adhesive film using a compounding machine at a compounding temperature of 75°C and a compounding speed of 3 m / min to obtain a primary pre-impregnated fabric, and then the primary pre-impregnated fabric was kept at 80°C for 0.5 h (curing) to obtain a pre-impregnated fabric.

[0060] S5. Preparation of wave-absorbing pre-impregnated material: the pre-impregnated fabric was compounded between two layers of wave-absorbing adhesive film using a compounding machine at a compounding temperature of 75°C and a compounding speed of 3 m / min to obtain a wave-absorbing pre-impregnated material composed of wave-absorbing adhesive film, wave-transparent adhesive film, quartz aramid hybrid fiber plain fabric, wave-transparent adhesive film, and wave-absorbing adhesive film from top to bottom. The process for preparing the wave-absorbing pre-impregnated material is shown in Figure 1 .

[0061] The wave-absorbing pre-impregnated material of the present embodiment was used to prepare a cyanate wave-absorbing composite material and detect it:

[0062] Preparation of cyanate ester wave-absorbing composite: the wave-absorbing prepreg prepared in step S5 is used to prepare a cyanate ester wave-absorbing composite according to the following autoclave curing procedure: 4 layers of the wave-absorbing prepreg are laid flat on a flat tooling mold, wherein polytetrafluoroethylene cloth is laid on the flat tooling mold, then a vacuum bag is assembled, and the vacuum bag film, air-permeable felt, release film, strippable cloth, 4 layers of the wave-absorbing prepreg, polytetrafluoroethylene cloth, and flat tooling mold are sequentially arranged from top to bottom, one end of a vacuum pipe is inserted into the vacuum bag film and fixed with sealing tape, the edge of the vacuum bag film is sealed with sealing tape, then a vacuum pump is connected, vacuum is drawn at room temperature, and the vacuum degree is 0.085 MPa to form a preform. Then the preform is placed in an autoclave, pressurized to 0.6 MPa, heated to 100°C at a rate of 1°C / min, kept at 100°C for 1 h, continuously heated to 150°C and kept at 150°C for 2 h, continuously heated to 200°C and kept at 200°C for 2 h, kept at pressure, and cooled to below 60°C at a cooling rate of 1.5°C / min, taken out of the autoclave, and after the temperature of the preform decreases to room temperature, the vacuum bag, air-permeable felt, release film, strippable cloth, and polytetrafluoroethylene cloth are removed to obtain a cyanate ester wave-absorbing composite cured from 4 layers of the wave-absorbing prepreg, and the total thickness of the cyanate ester wave-absorbing composite is 1.22 mm.

[0063] The cross-sectional micro-morphology of the cyanate ester wave-absorbing composite prepared in this example is shown in FIG. 1, wherein ① is fabric, ② is absorbent, and ③ is resin. It can be seen that the absorbent is arranged in an oriented manner in the horizontal direction in the figure. Figure 2

[0064] The cyanate ester wave-absorbing composite is processed into a 500 mm x 500 mm and a 300 mm x 300 mm flat plate, a 1-18 GHz arc method reflectivity test device is used to test the vertical reflectivity of the sample at 1-18 GHz, and the test results are shown in Table 1.

[0065] The average reflectivity absorption peak of the cyanate ester wave-absorbing composite prepared in this example is -1.45 dB at 1-2 GHz, -3.22 dB at 2-4 GHz, -8.92 dB at 4-8 GHz, -15.1 dB at 8-12 GHz, and -7.84 dB at 12-18 GHz, and the results are shown in Table 1.

[0066] Example 4:

[0067] A wave-absorbing prepreg and a preparation method thereof, which comprises the following steps:

[0068] ​S1. Preparation of fine mixed wave-absorbing resin: an absorber and magnesium phenolic resin with a mass ratio of 10:4 were added to a three-roll mill, wherein the absorber was flaky iron-silicon-nickel with a particle size of 50 μm; the three-roll mill with a model number of GS-100 was used for mixing at 85 °C for 30 min to obtain a crude mixed wave-absorbing resin. Then, the crude mixed wave-absorbing resin was refined using a double planetary mixer with a model number of SXHJ-100 to obtain a fine mixed wave-absorbing resin: the temperature of refining and mixing was 85 °C, the time of refining and mixing was 30 min, and the rotor speed of refining and mixing was 20 rpm.

[0069] S2. Preparation of fine mixed wave-transparent resin: barium phenolic resin and p-toluenesulfonic acid (curing agent) with a mass ratio of 3:1 were added to a three-roll mill, and the three-roll mill with a model number of GS-100 was used for mixing at 75 °C for 30 min to obtain a crude mixed wave-transparent resin. Then, the crude mixed wave-transparent resin was refined using a double planetary mixer with a model number of SXHJ-100 to obtain a fine mixed wave-transparent resin: the temperature of refining and mixing was 75 °C, the time of refining and mixing was 30 min, and the rotor speed of refining and mixing was 35 rpm.

[0070] S3. Preparation of adhesive film: the fine mixed wave-absorbing resin obtained in step S1 was coated on release paper using a film coating machine, the film coating temperature was 90 °C, and the film coating speed was 1 m / min to obtain a wave-absorbing adhesive film with a thickness of 0.15 mm; the fine mixed wave-transparent resin obtained in step S2 was coated on release paper using a film coating machine, the film coating temperature was 90 °C, and the film coating speed was 2 m / min to obtain a wave-transparent adhesive film with a thickness of 0.05 mm.

[0071] S4. Preparation of pre-impregnated fabric: basalt fiber plain fabric with a thickness of 0.1 mm was selected, and the basalt fiber plain fabric was compounded between two layers of wave-transparent adhesive film using a composite machine at a compounding temperature of 75 °C and a compounding speed of 3 m / min to obtain a primary pre-impregnated fabric, and then the primary pre-impregnated fabric was kept at 85 °C for 0.5 h (curing) to obtain a pre-impregnated fabric.

[0072] S5. Preparation of wave-absorbing prepreg: the pre-impregnated fabric was compounded between two layers of wave-absorbing adhesive film using a composite machine at a compounding temperature of 80 °C and a compounding speed of 2 m / min to obtain a wave-absorbing prepreg composed of, from top to bottom, a wave-absorbing adhesive film, a wave-transparent adhesive film, a basalt fiber plain fabric, a wave-transparent adhesive film, and a wave-absorbing adhesive film. The process for preparing the wave-absorbing prepreg is shown in Figure 1 .

[0073] A phenolic wave-absorbing composite was prepared using the wave-absorbing prepreg of the present embodiment and was detected:

[0074] Preparation of phenolic wave-absorbing composite: the wave-absorbing prepreg prepared in S5 was used to prepare the phenolic wave-absorbing composite according to the following autoclave curing procedure: 3 layers of wave-absorbing prepreg were laid flat on a flat tooling mold, wherein polytetrafluoroethylene cloth was laid on the flat tooling mold, then a vacuum bag was assembled, from top to bottom in order: vacuum bag film, air-permeable felt, release film, strippable cloth, 3 layers of wave-absorbing prepreg, polytetrafluoroethylene cloth and flat tooling mold, one end of a vacuum tube was inserted into the vacuum bag film and fixed with sealing tape, the edge of the vacuum bag film was sealed with sealing tape, then a vacuum pump was connected, vacuum was drawn at room temperature, the vacuum degree was 0.085 MPa, and a preform was formed. Then the preform was placed in an autoclave, pressurized to 0.6 MPa, heated to 130℃ at a rate of 1℃ / min, kept for 1 h, continued to heat to 180℃ for 2 h, kept the pressure, cooled to below 60℃ at a cooling rate of 1.5℃ / min, and taken out of the tank. After the temperature of the preform dropped to room temperature, the vacuum bag, air-permeable felt, release film, strippable cloth and polytetrafluoroethylene cloth were removed, and a phenolic wave-absorbing composite cured from 4 layers of wave-absorbing prepreg was obtained. The total thickness of the phenolic wave-absorbing composite was 1.03 mm.

[0075] The above phenolic wave-absorbing composite was processed into 500mm×500mm and 300mm×300mm flat plates, and the vertical reflectivity of the sample at 1-18GHz was tested using a 1-18GHz arc-shaped reflectivity test device. The test results are shown in Table 1.

[0076] The average reflectivity absorption peak of the phenolic wave-absorbing composite prepared in this embodiment at 1-2GHz was -1.02dB, the average reflectivity absorption peak at 2-4GHz was -3.95dB, the average reflectivity absorption peak at 4-8GHz was -6.85dB, the average reflectivity absorption peak at 8-12GHz was -12.11dB, and the average reflectivity absorption peak at 12-18GHz was -5.76dB. The results are shown in Table 1.

[0077] Example 5:

[0078] A wave-absorbing prepreg and a method for preparing the same, comprising the following steps:

[0079] S1. Preparation of fine mixed wave-absorbing resin: absorbent, HVA-2 m-phenylene bismaleimide and p-phenylenediamine (curing agent) with a mass ratio of 8:4:1 were added to a three-roll mill, wherein the absorbent was flaky iron silicon aluminum with a particle size of 50μm; the three-roll mill with a model of GS-100 was used for mixing at 70℃ for 30min to obtain a coarse mixed wave-absorbing resin. Then the coarse mixed wave-absorbing resin was refined using a double-planetary mixer with a model of SXHJ-100 to obtain a fine mixed wave-absorbing resin: the refining temperature was 70℃, the refining time was 30min, and the rotor speed was 30rpm.

[0080] S2. Preparation of fine mixed wave-transparent resin: T-shaped bismaleimide resin, diallyl bisphenol A (curing agent) with a mass ratio of 4:1 were added into a three-roll mill, and mixed at 75°C for 30 min using a three-roll mill with a model of GS-100 to obtain a crude mixed wave-transparent resin. Then the crude mixed wave-transparent resin was refined using a double planetary mixer with a model of SXHJ-100 to obtain a fine mixed wave-transparent resin: the temperature of refining and mixing was 75°C, the time of refining and mixing was 30 min, and the rotor speed of refining and mixing was 35 rpm.

[0081] S3. Preparation of adhesive film: the fine mixed wave-absorbing resin obtained in step S1 was coated on release paper using a film coating machine, the coating temperature was 80°C, the coating speed was 3 m / min, and a wave-absorbing adhesive film with a thickness of 0.1 mm was obtained; the fine mixed wave-transparent resin obtained in step S2 was coated on release paper using a film coating machine, the coating temperature was 80°C, the coating speed was 4 m / min, and a wave-transparent adhesive film with a thickness of 0.036 mm was obtained.

[0082] S4. Preparation of pre-impregnated fabric: a 0.06 mm quartz fiber twill fabric was selected, and the quartz fiber twill fabric was compounded between two layers of wave-transparent adhesive film using a composite machine at a compounding temperature of 75°C and a compounding speed of 3 m / min to obtain a primary pre-impregnated fabric, and then the primary pre-impregnated fabric was kept at 90°C for 0.5 h (curing) to obtain a pre-impregnated fabric.

[0083] S5. Preparation of wave-absorbing pre-impregnated material: the pre-impregnated fabric was compounded between two layers of wave-absorbing adhesive film using a composite machine at a compounding temperature of 70°C and a compounding speed of 3 m / min to obtain a wave-absorbing pre-impregnated material composed of wave-absorbing adhesive film, wave-transparent adhesive film, quartz fiber twill fabric, wave-transparent adhesive film and wave-absorbing adhesive film from top to bottom. The process for preparing the wave-absorbing pre-impregnated material is shown in Figure 1 .

[0084] A bismaleimide wave-absorbing composite material was prepared using the wave-absorbing pre-impregnated material of the present embodiment and was detected:

[0085] Preparation of double-layer absorbing composites: The absorbing prepreg prepared in step S5 is used to prepare double-layer absorbing composites according to the following autoclave curing procedure: 4 layers of absorbing prepreg are laid flat on a flat tooling mold, wherein polytetrafluoroethylene cloth is laid on the flat tooling mold, and then a vacuum bag is assembled, which is composed of a vacuum bag film, a breathable felt, an isolation film, a peelable cloth, 4 layers of absorbing prepreg, polytetrafluoroethylene cloth and a flat tooling mold from top to bottom. One end of the vacuum tube is inserted into the vacuum bag film and fixed with sealing tape. The sealing tape is used to seal along the edge of the vacuum bag film, and then a vacuum pump is connected. Vacuum is evacuated at room temperature with a vacuum degree of 0.085 MPa to form a preform. The preform was then placed in an autoclave, pressurized to 0.6 MPa, heated to 180°C at a rate of 1°C / min, kept warm for 1 hour, and then heated to 210°C and kept warm for 2 hours. The pressure was maintained and the preform was cooled to below 60°C at a cooling rate of 1.5°C / min. The preform was taken out of the autoclave, and after the temperature of the preform dropped to room temperature, the vacuum bag, breathable felt, isolation film, peelable cloth and polytetrafluoroethylene cloth were removed to obtain a BMI absorbing composite material cured from 4 layers of absorbing prepreg. The total thickness of the BMI absorbing composite material was 0.89 mm.

[0086] The above-mentioned double-stranded wave absorbing composite material was processed into 500mm×500mm and 300mm×300mm flat plates. The vertical reflectivity of the samples from 1 to 18 GHz was tested using a 1 to 18 GHz bow method reflectivity test equipment. The test results are shown in Table 1.

[0087] The average reflectivity absorption peak of the bismuth absorbing composite material prepared in this embodiment is -1.93dB at 1-2GHz, -4.84dB at 2-4GHz, -8.71dB at 4-8GHz, -8.19dB at 8-12GHz, and -9.66dB at 12-18GHz. The results are shown in Table 1.

[0088] Example 6:

[0089] A microwave absorbing prepreg and a preparation method thereof, comprising the following steps:

[0090] S1. Preparation of a finely mixed absorbing resin: Add an absorbent, barium phenolic resin, and p-toluenesulfonic acid (curing agent) in a mass ratio of 7:3:1 to a three-roll mill. The absorbent is 55 μm flake iron, silicon, and chromium. Mix for 30 minutes at 75°C using a GS-100 three-roll mill to obtain a coarsely mixed absorbing resin. The coarsely mixed absorbing resin is then milled and fine-mixed using an SXHJ-100 dual planetary mixer to obtain a finely mixed absorbing resin. The milling temperature is 75°C, the milling time is 30 minutes, and the rotor speed is 15 rpm.

[0091] S2. Preparation of a finely mixed wave-transmitting resin: Add barium phenolic resin and p-toluenesulfonic acid (curing agent) in a mass ratio of 3:1 to a three-roll mill and mix at 75°C for 30 minutes using a GS-100 three-roll mill to obtain a coarsely mixed wave-transmitting resin. This coarsely mixed wave-transmitting resin is then subjected to open-mixing and fine-mixing using an SXHJ-100 dual planetary mixer to obtain a finely mixed wave-transmitting resin. The open-mixing and fine-mixing temperature is 75°C, the open-mixing and fine-mixing time is 30 minutes, and the rotor speed during the open-mixing and fine-mixing is 30 rpm.

[0092] S3. Preparation of film: Use a coating machine to coat the finely mixed absorbing resin obtained in step S1 on the release paper at a coating temperature of 95°C and a coating speed of 1 m / min to obtain a 0.1 mm thick absorbing film; use a coating machine to coat the finely mixed transparent resin obtained in step S2 on the release paper at a coating temperature of 95°C and a coating speed of 2 m / min to obtain a 0.032 mm thick transparent film.

[0093] S4. Preparation of preimpregnated fabric: Select 0.08 mm aramid fiber forging fabric, use a compounding machine, a compounding temperature of 85 ° C, a compounding speed of 2 m / min, and compound the aramid fiber forging fabric between two layers of wave-transmitting adhesive film to obtain a primary preimpregnated fabric. Then, maintain the primary preimpregnated fabric at 90 ° C for 0.5 h (curing) to obtain a preimpregnated fabric.

[0094] S5. Preparation of absorbing prepreg: Using a compounding machine, the compounding temperature is 80℃, and the compounding speed is 2m / min. The prepreg fabric is compounded between two layers of absorbing films to obtain an absorbing prepreg composed of absorbing film, transparent film, aramid fiber forging fabric, transparent film and absorbing film from top to bottom. The process of preparing absorbing prepreg is as follows: Figure 1 .

[0095] The phenolic absorbing composite was prepared using the absorbing prepreg of this embodiment and tested:

[0096] Preparation of phenolic wave-absorbing composite: the wave-absorbing prepreg prepared in S5 was used to prepare the phenolic wave-absorbing composite according to the following autoclave curing procedure: 4 layers of the wave-absorbing prepreg were laid flat on a flat tooling mold, wherein polytetrafluoroethylene cloth was laid on the flat tooling mold, then a vacuum bag was assembled, and the vacuum bag film, air-permeable felt, separation film, strippable cloth, 4 layers of the wave-absorbing prepreg, polytetrafluoroethylene cloth and flat tooling mold were sequentially arranged from top to bottom, one end of a vacuum pipe was inserted into the vacuum bag film and fixed with sealing tape, the edge of the vacuum bag film was sealed with sealing tape, then a vacuum pump was connected, vacuum was drawn at room temperature, the vacuum degree was 0.085 MPa, and a preform was formed. Then the preform was placed in an autoclave, pressurized to 0.6 MPa, heated to 130℃ at a rate of 1℃ / min, kept for 1 h, continuously heated to 180℃ and kept for 2 h, the pressure was kept, and cooled to below 60℃ at a cooling rate of 1.5℃ / min, taken out of the autoclave, and after the temperature of the preform decreased to room temperature, the vacuum bag, air-permeable felt, separation film, strippable cloth and polytetrafluoroethylene cloth were removed, to obtain the phenolic wave-absorbing composite cured from 4 layers of the wave-absorbing prepreg, and the total thickness of the phenolic wave-absorbing composite was 0.97 mm.

[0097] The phenolic wave-absorbing composite was processed into 500 mm x 500 mm and 300 mm x 300 mm flat plates, the vertical reflectivity of the sample was tested by using a 1-18 GHz arc-shaped reflectivity test device, and the test results are shown in Table 1.

[0098] The average reflectivity absorption peak of the phenolic wave-absorbing composite prepared in this embodiment was -1.32 dB at 1-2 GHz, -4.75 dB at 2-4 GHz, -7.35 dB at 4-8 GHz, -11.18 dB at 8-12 GHz, and -5.01 dB at 12-18 GHz, and the results are shown in Table 1.

[0099] The beneficial effects of the present application are illustrated by the following comparative experiments:

[0100] Comparative Example 1

[0101] S1. Preparation of fine mixed wave-absorbing resin: the same as step S1 of Example 1.

[0102] S2. Preparation of wave-absorbing adhesive film: the fine mixed wave-absorbing resin obtained in step S1 was coated on release paper using a film coating machine to obtain a wave-absorbing adhesive film, wherein the film coating temperature was 75℃ and the film coating speed was 3 m / min, and the thickness of the wave-absorbing adhesive film was 0.09 mm.

[0103] S3. Preparation of absorbing prepreg: Select 0.06mm aramid fiber plain weave fabric, use a composite machine, composite temperature of 65 ° C, composite speed of 3m / min, the aramid fiber fabric composite between two layers of absorbing film to obtain an absorbing prepreg.

[0104] The absorbing prepreg of this comparative example was used to prepare an epoxy absorbing composite material and tested:

[0105] Preparation of epoxy absorbing composites: The absorbing prepreg prepared in step S3 is used to prepare epoxy absorbing composites according to the following autoclave curing procedure: 4 layers of absorbing prepreg are laid flat on a flat tooling mold, wherein polytetrafluoroethylene cloth is laid on the flat tooling mold, and then a vacuum bag is assembled, which is composed of a vacuum bag film, a breathable felt, an isolation film, a peelable cloth, 4 layers of absorbing prepreg, polytetrafluoroethylene cloth and a flat tooling mold from top to bottom, one end of the vacuum tube is inserted into the vacuum bag film and fixed with sealing tape, and the sealing tape is used to seal along the edge of the vacuum bag film, and then a vacuum pump is connected. Vacuum is evacuated at room temperature with a vacuum degree of 0.085 MPa to form a preform. The preform was then placed in an autoclave, pressurized to 0.6 MPa, heated to 130°C at a rate of 1°C / min, kept warm for 1 hour to maintain pressure, cooled to below 60°C at a cooling rate of 1.5°C / min, and taken out of the autoclave. After the temperature of the preform dropped to room temperature, the vacuum bag, breathable felt, isolation film, peelable cloth and polytetrafluoroethylene cloth were removed to obtain an epoxy absorbing composite material consisting of four layers of cured absorbing prepreg.

[0106] The epoxy absorbing composite material was processed into 500mm×500mm and 300mm×300mm flat plates. The vertical reflectivity of the samples was tested at 1-18GHz using a 1-18GHz bow method reflectivity tester. The test results are shown in Table 1.

[0107] The epoxy absorbing composite material prepared in this comparative example has an average reflectivity absorption peak of -0.85 dB at 1-2 GHz, an average reflectivity absorption peak of -2.40 dB at 2-4 GHz, an average reflectivity absorption peak of -6.63 dB at 4-8 GHz, an average reflectivity absorption peak of -8.79 dB at 8-12 GHz, and an average reflectivity absorption peak of -4.30 dB at 12-18 GHz. The total thickness of the epoxy absorbing composite material is 0.81 mm. The results are shown in Table 1.

[0108] Comparative Example 2:

[0109] S1. Preparation of finely mixed absorbing resin: the same as step S1 of Example 2.

[0110] S2. Preparing the wave-absorbing adhesive film: using a film coating machine, the fine mixed wave-absorbing resin obtained in step S1 is coated on a release paper to obtain a wave-absorbing adhesive film, wherein the film coating temperature is 80°C, the film coating speed is 2 m / min, and the thickness of the wave-absorbing adhesive film is 0.09 mm.

[0111] S3. Preparing the wave-absorbing prepreg: selecting 0.05 mm quartz fiber twill fabric, using a composite machine, the composite temperature is 70°C, and the composite speed is 2 m / min, the quartz fiber twill fabric is compounded between two layers of wave-absorbing adhesive film to obtain a wave-absorbing prepreg.

[0112] Using the wave-absorbing prepreg of the present comparative example, a double-matrix wave-absorbing composite is prepared and detected:

[0113] Preparing the double-matrix wave-absorbing composite: the wave-absorbing prepreg prepared in step S3 is used to prepare a double-matrix wave-absorbing composite according to the following autoclave curing procedure: 4 layers of wave-absorbing prepreg are laid flat on a flat tooling mold, wherein polytetrafluoroethylene cloth is laid on the flat tooling mold, then a vacuum bag is assembled, from top to bottom in order: vacuum bag film, air-permeable felt, separation film, strippable cloth, 4 layers of wave-absorbing prepreg, polytetrafluoroethylene cloth, and flat tooling mold, one end of the vacuum pipe is inserted into the vacuum bag film and fixed with sealing tape, the edge of the vacuum bag film is sealed with sealing tape, then the vacuum pump is connected, vacuum is drawn at room temperature, the vacuum degree is 0.085 MPa, and a preform is formed. Then the preform is placed in an autoclave, pressurized to 0.6 MPa, heated to 180°C at a rate of 1°C / min, kept for 1 h, continuously heated to 210°C for 2 h, kept the pressure, cooled to below 60°C at a cooling rate of 1.5°C / min, taken out of the autoclave, and after the preform temperature drops to room temperature, the vacuum bag, air-permeable felt, separation film, strippable cloth, and polytetrafluoroethylene cloth are removed to obtain a double-matrix wave-absorbing composite cured from 4 layers of wave-absorbing prepreg.

[0114] The above double-matrix wave-absorbing composite is processed into 500 mm x 500 mm and 300 mm x 300 mm flat plates, and the vertical reflectivity of the sample from 1 to 18 GHz is tested using a 1-18 GHz arc-shaped reflectivity test device, and the test results are shown in Table 1.

[0115] The double-matrix wave-absorbing composite prepared in the present comparative example has an average reflectivity absorption peak of -0.97 dB at 1-2 GHz, an average reflectivity absorption peak of -2.25 dB at 2-4 GHz, an average reflectivity absorption peak of -6.12 dB at 4-8 GHz, an average reflectivity absorption peak of -7.86 dB at 8-12 GHz, and an average reflectivity absorption peak of -3.42 dB at 12-18 GHz, and the total thickness of the double-matrix wave-absorbing composite is 0.75 mm, and the results are shown in Table 1.

[0116] Comparative Example 3:

[0117] S1. Preparation of finely mixed absorbing resin: the same as step S1 of Example 3.

[0118] S2. Preparation of an absorbing film: Using a coating machine, the finely mixed absorbing resin obtained in step S1 is coated on a release paper to obtain an absorbing film, wherein the coating temperature is 85°C, the coating speed is 3m / min, and the thickness of the absorbing film is 0.13mm.

[0119] S3. Preparation of absorbing prepreg: Select 0.1mm quartz aramid blended fiber plain fabric, use a composite machine, composite temperature of 75 ° C, composite speed of 3m / min, composite the quartz aramid blended fiber plain fabric between two layers of absorbing film to obtain an absorbing prepreg.

[0120] The absorbing prepreg of this comparative example was used to prepare an epoxy absorbing composite material and tested:

[0121] Preparation of cyanate ester absorbing composites: The absorbing prepreg prepared in step S3 is used to prepare a cyanate ester absorbing composite according to the following autoclave curing procedure: 4 layers of absorbing prepreg are laid flat on a flat tooling mold, wherein polytetrafluoroethylene cloth is laid on the flat tooling mold, and then a vacuum bag is assembled, which is composed of a vacuum bag film, a breathable felt, an isolation film, a peelable cloth, 4 layers of absorbing prepreg, polytetrafluoroethylene cloth and a flat tooling mold from top to bottom, one end of the vacuum tube is inserted into the vacuum bag film and fixed with sealing tape, and the sealing tape is used to seal along the edge of the vacuum bag film, and then a vacuum pump is connected. Vacuum is evacuated at room temperature with a vacuum degree of 0.085 MPa to form a preform. The preform was then placed in an autoclave, pressurized to 0.6 MPa, heated to 100°C at a rate of 1°C / min, kept warm for 1 hour, then heated to 150°C and kept warm for 2 hours, then heated to 200°C and kept warm for 2 hours, while maintaining the pressure. The preform was cooled to below 60°C at a cooling rate of 1.5°C / min, and then taken out of the autoclave. After the temperature of the preform dropped to room temperature, the vacuum bag, breathable felt, isolation film, peelable cloth and polytetrafluoroethylene cloth were removed to obtain a cyanate absorbing composite material consisting of four layers of cured absorbing prepreg.

[0122] The cross-sectional microstructure of the cyanate ester wave absorbing composite prepared in this comparative example is as follows: Figure 3 As shown, ① is fabric, ② is absorbent, and ③ is resin. It can be seen that the absorbent is arranged in disorder in the figure.

[0123] The cyanate ester absorbing composite was processed into 500mm×500mm and 300mm×300mm flat plates. The vertical reflectivity of the samples was tested at 1-18GHz using a 1-18GHz bow method reflectivity tester. The test results are shown in Table 1.

[0124] The cyanate ester absorbing composite prepared in this comparative example has an average reflectivity absorption peak of -1.02 dB at 1-2 GHz, an average reflectivity absorption peak of -2.35 dB at 2-4 GHz, an average reflectivity absorption peak of -7.69 dB at 4-8 GHz, an average reflectivity absorption peak of -13.26 dB at 8-12 GHz, and an average reflectivity absorption peak of -6.33 dB at 12-18 GHz. The total thickness of the cyanate ester absorbing composite is 1.22 mm. The results are shown in Table 1.

[0125] Table 1 Performance comparison of Examples 1 to 6 and Comparative Examples 1 to 3

[0126]

[0127] By comparing the reflectivity of Example 1 and Comparative Example 1, the reflectivity of Example 2 and Comparative Example 2, and the reflectivity of Example 3 and Comparative Example 3 in Table 1, it can be seen that the reflectivity of the absorbing composite material prepared in the embodiment of the present invention is reduced in the frequency range of 1-18 GHz, that is, the absorbing performance is improved.

[0128] The methods for preparing the microwave absorbing prepregs in Examples 1-6 can be summarized as follows:

[0129] a) preparing a finely mixed absorbing resin: mixing a base resin, a curing agent and an absorbent at 60-85° C. to obtain a coarsely mixed absorbing resin; then finely mixing the coarsely mixed absorbing resin at 60-85° C. to obtain a finely mixed absorbing resin;

[0130] b) preparing a finely mixed wave-transmitting resin: mixing a base resin and a curing agent at 60-75° C. to obtain a coarsely mixed resin; then finely mixing the coarsely mixed wave-transmitting resin at 65-75° C. to obtain a finely mixed wave-transmitting resin;

[0131] c) preparing an adhesive film: coating the finely mixed absorbing resin obtained in step a) on release paper at a coating temperature of 75° C. to 95° C. and a coating speed of 1 to 4 m / min to obtain an absorbing adhesive film; coating the finely mixed transparent resin obtained in step b) on release paper at a coating temperature of 75° C. to 95° C. and a coating speed of 1 to 4 m / min to obtain a transparent adhesive film;

[0132] d) Preparing preimpregnated fabric: laminating the fiber fabric between two layers of wave-transmitting adhesive films at a laminating temperature of 65-85° C. and a laminating speed of 2-3 m / min to obtain a primary preimpregnated fabric, and then curing the primary preimpregnated fabric at 70-90° C. to obtain a preimpregnated fabric.

[0133] e) preparing the wave-absorbing prepreg: the prepreg fabric is compounded between two layers of wave-absorbing adhesive films, the compounding temperature is 65-80 DEG C, the compounding speed is 2-3 m / min, and the wave-absorbing prepreg is obtained, wherein the wave-absorbing prepreg is sequentially from top to bottom: the wave-absorbing adhesive film, the wave-transparent adhesive film, the fiber fabric, the wave-transparent adhesive film and the wave-absorbing adhesive film.

[0134] In step a), the mass ratio of the absorbent, the matrix resin and the curing agent is 5-13.5:3-4:0-1;

[0135] In step b), the mass ratio of the matrix resin and the curing agent is 3-4:1;

[0136] The absorbent is one or any combination of flaky carbonyl iron, flaky iron silicon aluminum, flaky iron silicon chromium, flaky iron silicon nickel and short carbon fibers; the particle size of the absorbent is 5-100 microns;

[0137] The matrix resin is one or any combination of epoxy resin, cyanate ester resin, bismaleimide resin and phenolic resin; the curing agent is one or any combination of dicyandiamine, diallyl bisphenol A, phthalic anhydride, p-phenylenediamine and p-toluene sulfonic acid;

[0138] In step d), the fiber fabric is one or any combination of mixed fabric of quartz fiber fabric, aramid fiber fabric and basalt fiber fabric; the thickness of the fiber fabric is 0.05-0.1 mm;

[0139] The thickness of the wave-transparent adhesive film is 40%-60% of the thickness of the fiber fabric;

[0140] The thickness of the wave-absorbing adhesive film is 120%-166.7% of the thickness of the fiber fabric

[0141] The part not described in detail in the present application is the technology known to those skilled in the art.

[0142] Finally, it should be pointed out that: the above examples are only used to illustrate the technical solutions of the present application, and not to limit them; although the present application has been described in detail with reference to the foregoing examples, those skilled in the art should understand that: it can still modify the technical solutions recorded in the foregoing examples, or make equivalent replacement for part of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present application.

Claims

1. A method for preparing a microwave absorbing prepreg, characterized in that: include: a) mixing a base resin, a curing agent and an absorbent at 60-85° C. to obtain a coarsely mixed absorbing resin; then finely mixing the coarsely mixed absorbing resin at 60-85° C. to obtain a finely mixed absorbing resin; b) mixing the base resin and the curing agent at 60-75° C. to obtain a coarsely mixed wave-transparent resin; and then finely mixing the coarsely mixed wave-transparent resin at 65-75° C. to obtain a finely mixed wave-transparent resin; c) coating the finely mixed absorbing resin obtained in step a) on release paper at a coating temperature of 75° C. to 95° C. to obtain an absorbing adhesive film; coating the finely mixed transparent resin obtained in step b) on release paper at a coating temperature of 75° C. to 95° C. to obtain a transparent adhesive film; d) laminating the fiber fabric between two layers of the wave-transmitting adhesive film at a laminating temperature of 65-85° C. to obtain a primary prepreg fabric, and then curing the primary prepreg fabric at 70-90° C. to obtain a prepreg fabric; e) compounding the preimpregnated fabric between two layers of the absorbing adhesive film at a compounding temperature of 65° C. to 80° C. to obtain an absorbing prepreg, wherein the absorbing prepreg comprises, from top to bottom, the absorbing adhesive film, the transparent adhesive film, the fiber fabric, the transparent adhesive film, and the absorbing adhesive film.

2. The method according to claim 1, characterized in that In step a), the mass ratio of the absorbent, the matrix resin and the curing agent is 5-13.5: 3-4: 0-1.

3. The method according to claim 1, wherein In step b), the mass ratio of the base resin to the curing agent is 3-4:

1.

4. The method according to claim 1, wherein The absorbent is one of flaky carbonyl iron, flaky sendust, flaky iron silicon chromium, flaky iron silicon nickel and chopped carbon fiber, or any combination thereof, and the particle size of the absorbent is 5 to 100 microns.

5. The method according to claim 1, wherein The matrix resin is one of epoxy resin, cyanate resin, bismaleimide resin and phenolic resin or any combination thereof; the curing agent is one of dicyandiamide, diallyl bisphenol A, phthalic anhydride, p-phenylenediamine and p-toluenesulfonic acid or any combination thereof.

6. The method according to claim 1, wherein The fiber fabric is a mixed fabric of one of quartz fiber fabric, aramid fiber fabric and basalt fiber fabric or any combination thereof, and the thickness of the fiber fabric is 0.05-0.1 mm.

7. The method according to claim 1, wherein The thickness of the wave-transmitting adhesive film is 40% to 60% of the thickness of the fiber fabric; the thickness of the wave-absorbing adhesive film is 120% to 166.7% of the thickness of the fiber fabric.

8. A microwave-absorbing prepreg, characterized in that: The wave-absorbing prepreg is a wave-absorbing prepreg prepared according to the method according to any one of claims 1 to 7.

9. Use of the microwave absorbing prepreg prepared by the method according to any one of claims 1 to 7 in microwave absorbing equipment.

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