Absorbing Wave Prepreg with High Carbon Series Absorbing Agent Content and Its Preparation Method

Abstract

The present invention discloses a wave-absorbing prepreg with a high content of carbon-based wave-absorbing agent and a preparation method thereof, which relates to the technical field of wave-absorbing prepregs. The preparation method includes the following steps: mixing a carbon-based wave-absorbing agent, a volatile solvent, and an active monomer diluent to obtain adhesive solution I-1; coating the adhesive solution I-1 on the surface of a fiber cloth and drying it to form a film to obtain fiber cloth I-2; taking two layers of fiber cloth I-2, laminating them face to face, and stitching and reinforcing them to obtain three-dimensional cloth I-3; adding a carbon-based wave-absorbing agent to a resin matrix and mixing to obtain a mixed resin matrix II-1; using a hot melt impregnation method to impregnate the mixed resin matrix II-1 into the three-dimensional cloth I-3 to obtain a wave-absorbing prepreg with a high content of carbon-based wave-absorbing agent. This method significantly improves the content of the carbon-based wave-absorbing agent and the wave-absorbing efficiency in the wave-absorbing prepreg. At the same time, there is also an obvious operable space for the ply thickness, thus greatly broadening the application range of the wave-absorbing prepreg and meeting the diverse product requirements.

Description

Technical Field

[0001] The present invention relates to the technical field of microwave absorbing prepregs, and particularly to a microwave absorbing prepreg with a high content of carbon-based microwave absorbing agent and a preparation method thereof. Background Art

[0002] With the development of aerospace technology and electronic information technology, high-speed aircraft, low-altitude unmanned aerial vehicles, warships, and special vehicles all have requirements for stealth functions to improve the survivability of military equipment in complex battlefield environments, so as to adapt to the development trend of modern electronic information warfare. Therefore, microwave absorbing materials are becoming a hot topic in the field of materials at present.

[0003] A microwave absorbing material is a material that realizes "stealth" by absorbing and attenuating incident electromagnetic waves and converting them into heat energy dissipation or interference cancellation; the microwave absorbing ability of a microwave absorbing material mainly depends on the microwave absorbing medium, that is, the absorption efficiency of the microwave absorbing agent. Microwave absorbing agents can be classified into magnetic loss type microwave absorbing agents, resistance loss type microwave absorbing agents, and dielectric loss type microwave absorbing agents according to the loss mechanism; traditional iron powders, iron alloy powders, ferrites, and carbonyl iron powders mainly absorb and attenuate electromagnetic waves through hysteresis loss, etc., and are typical magnetic loss type microwave absorbing agents, which have the advantages of strong absorption efficiency and low price, but also have disadvantages such as large density, poor thermal stability, and poor chemical resistance; carbon-based microwave absorbing agents such as carbon black, graphene, carbon nanotubes, chopped carbon fibers, silicon carbide, etc. mainly absorb and dissipate electromagnetic waves through eddy current loss, etc., and are typical resistance type microwave absorbing agents, which have the advantages of small density, wide absorption frequency band, good temperature resistance, and good corrosion and oxidation resistance.

[0004] Compared with iron-based microwave absorbing agents, carbon-based microwave absorbing agents have the advantages of small density, less weight gain, and good chemical resistance, and are more suitable for the field of aircraft; however, carbon-based microwave absorbing agents have high oil absorption, large specific surface area, and high surface energy, resulting in a very small addition amount in the resin formulation system. For example, it has been reported that the addition amount of carbon-based microwave absorbing agent in the formulation is 40% by volume fraction, but its mass fraction is actually <4 wt%; experiments show that in a solvent-free resin formulation system, the addition amount of carbon-based microwave absorbing agent is difficult to exceed 5 wt% while maintaining good processability; when the content of carbon-based microwave absorbing agent in the resin system is too high, the viscosity of the system increases significantly, the thixotropy is obvious, the fluidity is poor, the gluing processability is poor, and at the same time, it will lead to a decrease in the crosslinking density during molding and a reduction in mechanical properties. In contrast, the addition amount of iron-based microwave absorbing agent can even exceed 70 wt% while maintaining good processing performance; thus, it is difficult to compare the microwave absorbing performance of carbon-based microwave absorbing materials with that of iron-based microwave absorbing materials.

[0005] How to increase the content of microwave absorbing agent in the prepreg and prepare a microwave absorbing prepreg with a high content of carbon-based microwave absorbing agent, so as to effectively improve the microwave absorbing performance, is the problem to be solved by the present invention. Summary of the Invention

[0006] To solve the above technical problems, the object of the present invention is to provide a wave-absorbing prepreg with a high content of carbon-based wave-absorbing agents and a preparation method thereof. This method significantly improves the content of carbon-based wave-absorbing agents and the wave-absorbing efficiency in the wave-absorbing prepreg. At the same time, there is an obvious operable space for the ply thickness, thus greatly broadening the application range of the wave-absorbing prepreg and meeting the diverse product requirements.

[0007] The technical solution of the present invention to solve the above technical problems is as follows: providing a preparation method of a wave-absorbing prepreg with a high content of carbon-based wave-absorbing agents, including the following steps:

[0008] (1) Stir, mix and grind and disperse a carbon-based wave-absorbing agent, a volatile solvent and an active monomer diluent to obtain adhesive solution I-1;

[0009] (2) Coat the adhesive solution I-1 obtained in step (1) on the surface of a fiber cloth, and then dry it to form a film to obtain fiber cloth I-2;

[0010] (3) Take two layers of the fiber cloth I-2 obtained in step (2), bond the sides coated with the adhesive solution "face to face", and then reinforce it by stitching technology to obtain three-dimensional cloth I-3;

[0011] (4) Add a carbon-based wave-absorbing agent to a resin matrix, stir, mix and grind and disperse to obtain a mixed resin matrix II-1;

[0012] (5) Use the hot melt impregnation method to impregnate the mixed resin matrix II-1 obtained in step (4) into the three-dimensional cloth I-3 obtained in step (3) to obtain a wave-absorbing prepreg with a high content of carbon-based wave-absorbing agents.

[0013] Further, in steps (1) and (4), the carbon-based wave-absorbing agent is at least one of graphene, carbon nanotubes, carbon black and silicon carbide.

[0014] Among them, the graphene is a reduced graphene oxide powder with a conductivity of 1000 - 50000 S / m, a particle size of 1 - 100 μm and a specific surface area of 100 - 300 m 2 / g, and further a reduced graphene oxide powder with a conductivity of 5000 - 10000 S / m, a particle size of 10 - 20 μm and a specific surface area of 200 - 250 m 2 / g; the carbon nanotubes are multi-walled carbon nanotubes with a diameter of 5 - 20 nm, a length of 50 - 500 μm and a specific surface area of 200 - 400 m 2 / g, and further multi-walled carbon nanotubes with a diameter of 10 - 15 nm, a length of 50 - 100 μm and a specific surface area of 250 - 300 m 2 / g; the carbon black has a resistivity of 0.1 - 1 Ω∙m, a particle size of 5 - 20 μm and a specific surface area of 500 - 1000 m 2Conductive carbon black of / g, and further select conductive carbon black with a resistivity of 0.5 - 0.8 Ω∙m, a particle size of 10 - 15 μm, and a specific surface area of 600 - 800 m 2 / g; select silicon carbide with a purity of ≥99.9%, a particle size of ≤0.5 μm, a density of 3.21 g / cm 3 and a resistivity of 0.3 - 0.5 Ω∙m.

[0015] Furthermore, the volatile solvent is a low-boiling solvent, including but not limited to conventional solvents such as alcohols, ketones, esters, deionized water, etc.

[0016] Furthermore, the volatile solvent is at least one of ethanol, isopropanol, n-butanol, acetone, butanone, cyclohexanone, ethyl acetate, butyl acetate, ethyl lactate, and pure water.

[0017] Furthermore, in step (1), the reactive monomer diluent corresponds to the resin matrix in step (4). For example, the monomer diluents for epoxy resin systems include but are not limited to aliphatic epoxy resin monomers such as GE-5, GE-8, GE-13, GE-20, and GE-22 from Huntsman; alicyclic epoxy resin monomers such as TTA-21 and TTA-26 from Tetra; the monomer diluents for cyanate ester resin systems can also use the above epoxy resin monomers, etc.; the monomer diluents for acrylate resin systems, acrylate monomers such as methyl (meth)acrylate, butyl (meth)acrylate, lauryl (meth)acrylate, norbornene (meth)acrylate, and hexanediol diacrylate, etc.

[0018] Furthermore, in steps (1) and (4), grind to a fineness of less than 20 μm.

[0019] Furthermore, in step (1), stir at 10 - 500 r / min for 20 - 60 min.

[0020] Furthermore, in step (1), the concentration of the carbon-based wave-absorbing agent in the adhesive solution I-1 is 20 - 60 wt%, and the concentration of the reactive monomer diluent is 5 - 20 wt%.

[0021] Furthermore, in step (2), the coating amount of the adhesive solution I-1 is 50 - 3000 g / m 2 .

[0022] The fiber cloth surface is one of glass fiber, quartz fiber, aramid fiber, ultra-high molecular weight polyethylene fiber, and polyimide fiber. The surface density of the fiber cloth is 40 - 400 g / m 2 , and further 50 - 200 g / m 2 .

[0023] Furthermore, in step (2), the drying temperature is 60 - 100 °C.

[0024] Further, in step (4), the concentration of the carbon-based wave-absorbing agent in the mixed resin matrix II-1 is 0.5-5 wt%.

[0025] Further, in step (4), the resin matrix is one of epoxy resin, cyanate resin, and acrylate resin. The resin matrix includes resin, curing agent, and additives, etc.

[0026] Further, in step (4), stir at 50-1000 r / min for 10-30 min.

[0027] Further, in step (5), the steps of the hot melt impregnation method are as follows: uniformly apply the mixed resin matrix II-1 obtained in step (4) at 50-1000 g / m 2 onto the release paper, then cover the three-dimensional fabric I-3 obtained in step (3), and perform hot pressing and impregnation at 50-150 °C to obtain a wave-absorbing prepreg with a high carbon-based wave-absorbing agent content.

[0028] Furthermore, the coating amount is 40-2000 g / m 2 , further 100-500 g / m 2 ; the coating temperature is 20-80 °C, further 30-70 °C; the coating speed is 1-10 m / min, further 2-5 m / min.

[0029] The present invention also provides a wave-absorbing prepreg with a high carbon-based wave-absorbing agent content prepared by the preparation method of the above wave-absorbing prepreg with a high carbon-based wave-absorbing agent content.

[0030] The present invention has the following beneficial effects:

[0031] 1. The method of the present invention divides the carbon-based wave-absorbing agent into two parts: most of it is formulated into a high-concentration slurry and first coated onto the fiber cloth, so that the addition amount of the wave-absorbing agent is no longer limited by the resin adsorption amount and processability, greatly improving the controllable range of the wave-absorbing agent addition amount. And the fiber cloth coated with the wave-absorbing agent on one side is "face to face" bonded, and then the two layers of fiber cloth are stitched together with fiber filaments to form a three-dimensional "sandwich" structure, improving the interlayer force and reducing the loss of the wave-absorbing agent at the same time; a small part of the carbon-based wave-absorbing agent is added to the mixed resin and used in combination with the resin matrix. Since the content of the wave-absorbing agent in the resin formula no longer has a major impact on the total amount of the wave-absorbing agent, the resin viscosity can be adjusted to a suitable range for easy construction.

[0032] 2. The present invention is composed of a small amount of active monomer and a large amount of carbon-based absorbent in the glue solution. During the preparation process of the prepreg, the monomer can adsorb the carbon-based wave-absorbing agent and improve its adhesion to the fiber cloth. And during the hot pressing and curing process of the material, the monomer can cross-link with the curing agent or resin permeating from the resin matrix, making the material cross-layer cured into a three-dimensional continuous whole.

[0033] 3. Carbon-based wave-absorbing agents have the characteristics of low density, large specific surface area, and strong oil absorption. It is very difficult to achieve a high content addition in the resin formulation system. However, in the method of the present invention, the content of the carbon-based wave-absorbing agent after the glue solution is dried can actually exceed 90 wt%, and the total content of the carbon-based wave-absorbing agent in the prepreg can also reach 70 wt%. This makes the prepared wave-absorbing prepreg have the advantages of both light weight and high wave-absorbing performance, and has great application value in the field of aircraft.

[0034] 4. The center of the wave-absorbing prepreg of the present invention is a wave-absorbing layer with a high content of wave-absorbing agent, and the outer side is a wave-absorbing layer with a low content of wave-absorbing agent, showing a gradient wave-absorbing effect. This wave-absorbing prepreg can be laid with several layers of a single grade, or multiple grades can be combined for laying. Even a wave-transmitting layer and a reflecting layer can be added to prepare a stealth material, so as to meet the application requirements of diversified products.

[0035] 5. The production process of the wave-absorbing prepreg of the present invention can be carried out step by step on different equipment. The operation is flexible, and the requirements for equipment functions are relatively simple. The components of the slurry formulation and the resin formulation can be flexibly adjusted within a certain range. Thus, a series of prepregs that meet different functional requirements can be produced according to actual needs, and can be quickly switched on the step-by-step production line equipment, and can further meet the application requirements of diversified products. Description of the Drawings

[0036] Figure 1 It is a schematic structural diagram of the wave-absorbing prepreg with a high content of carbon-based wave-absorbing agent in Example 1;

[0037] Figure 2 It is a schematic structural diagram of the three-dimensional fabric I-3 in Example 1;

[0038] Figure 3 It is a schematic diagram of the preparation process of the three-dimensional fabric in Example 1;

[0039] Figure 4 It is a schematic diagram of sewing in Example 1;

[0040] Figure 5 It is a schematic structural diagram of the stealth composite material prepared using the wave-absorbing prepreg with a high content of carbon-based wave-absorbing agent in Test Example 1. Detailed Embodiments

[0041] The principles and features of the present invention are described below. The examples given are only used to explain the present invention and are not intended to limit the scope of the present invention. For those not specified in the examples, the conventional conditions or the conditions recommended by the manufacturer are followed. For the reagents or instruments not specified by the manufacturer, they are all conventional products that can be obtained through commercial purchase.

[0042] Example 1

[0043] A wave-absorbing prepreg with a high-carbon series wave-absorbing agent content has a structure as shown in Figure 1 and its preparation method includes the following steps:

[0044] (1) Mix reduced graphene oxide powder, methyl ethyl ketone, and aliphatic bifunctional epoxy resin GE-20 in a mass ratio of 50:45:5, stir at 150 r / min for 40 min, and grind to a fineness less than 20 μm to obtain adhesive solution I-1; among them, the reduced graphene oxide powder has a conductivity of 8500 S / m, a particle size of 15 μm, and a specific surface area of 240 m 2 / g;

[0045] (2) Coating the adhesive solution I-1 obtained in step (1) onto a glass fiber cloth surface with a surface density of 60 g / m 2 at 970 g / m 2 , and then drying it into a film at 80 °C to obtain fiber cloth I-2;

[0046] (3) Take two layers of the fiber cloth I-2 obtained in step (2), bond the sides coated with the adhesive solution "face to face" (as shown in Figure 2 ), and then reinforce the two layers of cloth by sewing with an industrial sewing machine (as shown in Figure 3 and 4 ), with nine sewing machine heads arranged along the weft direction, a needle weft spacing of 10 cm, and synchronous continuous sewing to obtain three-dimensional cloth I-3;

[0047] (4) Add reduced graphene oxide powder to epoxy resin, stir and mix at 500 r / min for 20 min, and grind to a fineness less than 20 μm to obtain mixed resin matrix II-1, among which the concentration of reduced graphene oxide powder is 1 wt%; the reduced graphene oxide powder has a conductivity of 8500 S / m, a particle size of 15 μm, and a specific surface area of 240 m 2 / g; the epoxy resin system is E-51:GE-20:9506 = 40:13:46;

[0048] (5) Uniformly coat the mixed resin matrix II-1 obtained in step (4) onto a release paper at 100 g / m 2 , and then cover it on both sides of the three-dimensional cloth I-3 obtained in step (3), and perform hot pressing and impregnation at 60 °C. The pressure of the hot pressing roller is 0.3 MPa, the drying length of the impregnation section is 30 m, and the hot pressing and impregnation time is 6 min to obtain a wave-absorbing prepreg with a high-carbon series wave-absorbing agent content.

[0049] Example 2

[0050] A wave-absorbing prepreg with a high-carbon series wave-absorbing agent content, and its preparation method includes the following steps:

[0051] (1) Mix reduced graphene oxide powder, carbon nanotubes, carbon black, ethyl acetate, and the active monomer diluent TTA-26 in a mass ratio of 40:10:5:40:5, stir at 50 r / min for 50 min, and grind to a fineness of less than 20 μm to obtain adhesive solution I-1;

[0052] (2) Coat the adhesive solution I-1 obtained in step (1) onto the surface of a glass fiber cloth at a rate of 60 g / m 2 Then dry it at 90 °C to form a film to obtain fiber cloth I-2;

[0053] (3) Take two layers of the fiber cloth I-2 obtained in step (2), bond the sides coated with the adhesive solution "face to face", and then reinforce it through a stitching technique to obtain three-dimensional cloth I-3;

[0054] (4) Add reduced graphene oxide powder, carbon nanotubes, and carbon black to epoxy resin, stir and mix at 400 r / min for 25 min, and grind to a fineness of less than 20 μm to obtain a mixed resin matrix II-1, where the specific component ratio is graphene:carbon nanotubes:carbon black:E-44:TTA-26:DDA-10:U-415 = 0.8:0.2:0.1:45:33.7:20:0.2;

[0055] (5) Uniformly coat the mixed resin matrix II-1 obtained in step (4) onto a release paper at a rate of 100 g / m 2 Then double-side cover it onto the three-dimensional cloth I-3 obtained in step (3), perform hot pressing and impregnation at 70 °C, the pressure of the hot pressing roller is 0.3 MPa, the drying length of the impregnation section is 30 m, and the hot pressing and impregnation time is 6 min to obtain a wave-absorbing prepreg with a high carbon-based wave-absorbing agent content.

[0056] Example 3

[0057] A wave-absorbing prepreg with a high carbon-based wave-absorbing agent content, and its preparation method includes the following steps:

[0058] (1) Mix reduced graphene oxide powder, methyl ethyl ketone, and GE-22 in a mass ratio of 30:60:10, stir at 200 r / min for 30 min, and grind to a fineness of less than 20 μm to obtain adhesive solution I-1; where the conductivity of the reduced graphene oxide powder is 8500 S / m, the particle size is 15 μm, and the specific surface area is 240 m 2 / g;

[0059] (2) Coat the adhesive solution I-1 obtained in step (1) onto the surface of a glass fiber cloth at a rate of 350 g / m 2 Then dry it at 80 °C to form a film to obtain fiber cloth I-2;

[0060] (3) Take two layers of the fiber fabric I-2 obtained in step (2), attach the sides coated with the adhesive solution "face to face", and then stitch and reinforce the two layers of fabric through an industrial sewing machine with a needle weft spacing of 10 cm and continuous synchronous stitching to obtain the three-dimensional fabric I-3;

[0061] (4) Add the reduced graphene oxide powder to the epoxy resin and stir and mix at 300 r / min for 30 min, then grind to a fineness of less than 20 μm to obtain the mixed resin matrix II-1, where the specific component ratio is reduced graphene oxide powder: E-51: GE-20: 9506 = 2:40:19:49;

[0062] (5) Apply the mixed resin matrix II-1 obtained in step (4) evenly onto the release paper at 200 g / m 2 Then double-side cover it onto the three-dimensional fabric I-3 obtained in step (3), and perform hot pressing and impregnation at 60 °C. The pressure of the hot pressing roller is 0.3 MPa, the drying length of the impregnation section is 30 m, and the hot pressing and impregnation time is 6 min to obtain the absorbent prepreg with a high carbon-based absorbent content.

[0063] Example 4

[0064] An absorbent prepreg with a high carbon-based absorbent content, and its preparation method includes the following steps:

[0065] (1) Mix the reduced graphene oxide powder, methyl ethyl ketone and GE-22 in a mass ratio of 40:50:10, stir at 200 r / min for 30 min, and grind to a fineness of less than 20 μm to obtain the adhesive solution I-1; among them, the reduced graphene oxide powder has a conductivity of 8500 S / m, a particle size of 15 μm and a specific surface area of 240 m 2 / g;

[0066] (2) Apply the adhesive solution I-1 obtained in step (1) onto the glass fiber cloth surface at 350 g / m 2 Then dry it into a film at 80 °C to obtain the fiber fabric I-2;

[0067] (3) Take two layers of the fiber fabric I-2 obtained in step (2), attach the sides coated with the adhesive solution "face to face", and then stitch and reinforce the two layers of fabric through an industrial sewing machine with a needle weft spacing of 10 cm and continuous synchronous stitching to obtain the three-dimensional fabric I-3;

[0068] (4) Add the reduced graphene oxide powder to the epoxy resin and stir and mix at 300 r / min for 30 min, then grind to a fineness of less than 20 μm to obtain the mixed resin matrix II-1, where the specific component ratio is reduced graphene oxide powder: E-51: GE-20: 9506 = 2.5:40:19:49;

[0069] (5) Apply the mixed resin matrix II-1 obtained in step (4) at 180 g / m 2 evenly onto the release paper, then cover it on both sides onto the three-dimensional fabric I-3 obtained in step (3), and perform hot pressing and impregnation at 60 °C. The pressure of the hot pressing roller is 0.3 MPa, the drying length of the impregnation section is 30 m, and the hot pressing and impregnation time is 6 min to obtain a wave-absorbing prepreg with a high carbon-based wave-absorbing agent content.

[0070] Example 5

[0071] A wave-absorbing prepreg with a high carbon-based wave-absorbing agent content, and its preparation method includes the following steps:

[0072] (1) Mix reduced graphene oxide powder, methyl ethyl ketone, and GE-29 in a mass ratio of 50:45:5, stir at 10 r / min for 20 min, and grind to a fineness of less than 20 μm to obtain adhesive solution I-1; among them, the reduced graphene oxide powder has a conductivity of 8500 S / m, a particle size of 15 μm, and a specific surface area of 240 m 2 / g;

[0073] (2) Apply the adhesive solution I-1 obtained in step (1) at 1800 g / m 2 onto the surface of the quartz fiber cloth, and then dry it into a film at 80 °C to obtain fiber fabric I-2;

[0074] (3) Take two layers of the fiber fabric I-2 obtained in step (2), stick the sides coated with the adhesive solution "face to face", and then reinforce the two layers of fabric by sewing with an industrial sewing machine. Nine sewing machine heads are arranged along the weft direction, the needle spacing in the weft direction is 10 cm, and continuous sewing is performed synchronously to obtain three-dimensional fabric I-3;

[0075] (4) Add reduced graphene oxide powder to the cyanate resin, stir and mix at 400 r / min for 20 min, and grind to a fineness of less than 20 μm to obtain a mixed resin matrix II-1, where the specific component ratio is reduced graphene oxide powder: cyanate resin: GE-29: DBTDL = 1:70:28.9:0.1;

[0076] (5) Apply the mixed resin matrix II-1 obtained in step (4) at 200 g / m 2 evenly onto the release paper, then cover it on both sides onto the three-dimensional fabric I-3 obtained in step (3), and perform hot pressing and impregnation at 90 °C. The pressure of the hot pressing roller is 0.3 MPa, the drying length of the impregnation section is 30 m, and the hot pressing and impregnation time is 6 min to obtain a wave-absorbing prepreg with a high carbon-based wave-absorbing agent content.

[0077] Example 6

[0078] A wave-absorbing prepreg with a high carbon-based wave-absorbing agent content, and its preparation method includes the following steps:

[0079] (1) Mix reduced graphene oxide powder, ethyl acetate, and norbornene acrylate (IBOA) in a mass ratio of 60:35:5, stir at 100 r / min for 40 min, and grind to a fineness of less than 20 μm to obtain adhesive solution I-1;

[0080] (2) Coat the adhesive solution I-1 obtained in step (1) onto the surface of quartz fiber cloth at a rate of 1440 g / m 2 and then dry it at 85 °C to form a film to obtain fiber cloth I-2;

[0081] (3) Take two layers of the fiber cloth I-2 obtained in step (2), bond the sides coated with the adhesive solution "face to face", and then reinforce it by stitching technology to obtain three-dimensional cloth I-3;

[0082] (4) Add reduced graphene oxide powder to acrylate resin, stir and mix at 350 r / min for 20 min, and grind to a fineness of less than 20 μm to obtain mixed resin matrix II-1, where the specific component ratio is reduced graphene oxide powder: 6157B-80: IBOA: TMPTA: BPO = 2:60:32:5:1;

[0083] (5) Uniformly coat the mixed resin matrix II-1 obtained in step (4) onto the release paper at a rate of 100 g / m 2 and then double-sidedly cover it on the three-dimensional cloth I-3 obtained in step (3), perform hot pressing and impregnation at 70 °C, the pressure of the hot pressing roller is 0.3 MPa, the drying length of the impregnation section is 30 m, and the hot pressing and impregnation time is 6 min to obtain a wave-absorbing prepreg with a high carbon-based wave-absorbing agent content.

[0084] Example 7

[0085] A wave-absorbing prepreg with a high carbon-based wave-absorbing agent content, and its preparation method includes the following steps:

[0086] (1) Mix reduced graphene oxide powder, methyl ethyl ketone, and aliphatic bifunctional epoxy resin GE-20 in a mass ratio of 20:75:5, stir at 10 r / min for 20 min, and grind to a fineness of less than 20 μm to obtain adhesive solution I-1; among them, the conductivity of the reduced graphene oxide powder is 8500 S / m, the particle size is 15 μm, and the specific surface area is 240 m 2 / g;

[0087] (2) Coat the adhesive solution I-1 obtained in step (1) onto the surface of glass fiber cloth at a rate of 50 g / m 2 and then dry it at 60 °C to form a film to obtain fiber cloth I-2;

[0088] (3) Take two layers of the fiber fabric I-2 obtained in step (2), bond the sides coated with the sizing agent "face to face", and then reinforce the two layers of fabric by sewing with an industrial sewing machine. Nine sewing machine heads are arranged along the weft direction, with a needle weft spacing of 10 cm, and continuous sewing is carried out synchronously to obtain the three-dimensional fabric I-3;

[0089] (4) Add the reduced graphene oxide powder to the epoxy resin, stir and mix at 50 r / min for 10 min, and grind to a fineness of less than 20 μm to obtain the mixed resin matrix II-1, where the concentration of the reduced graphene oxide powder is 0.5 wt%; among them, the conductivity of the reduced graphene oxide powder is 8500 S / m, the particle size is 15 μm, and the specific surface area is 240 m 2 / g, and the epoxy resin system is E-51: GE-20: 9506 = 40: 13: 46;

[0090] (5) Apply the mixed resin matrix II-1 obtained in step (4) evenly on the release paper at 50 g / m 2 Then cover it on both sides of the three-dimensional fabric I-3 obtained in step (3), and perform hot pressing and impregnation at 50 °C. The pressure of the hot pressing roller is 0.3 MPa, the drying length of the impregnation section is 30 m, and the hot pressing and impregnation time is 6 min to obtain the wave-absorbing prepreg with a high carbon-based wave-absorbing agent content.

[0091] Example 8

[0092] A preparation method of a wave-absorbing prepreg with a high carbon-based wave-absorbing agent content, comprising the following steps:

[0093] (1) Mix the reduced graphene oxide powder, carbon nanotubes, carbon black, ethyl acetate, and the active monomer diluent TTA-26 in a mass ratio of 30: 10: 10: 40: 10, stir at 200 r / min for 40 min, and grind to a fineness of less than 20 μm to obtain the sizing agent I-1;

[0094] (2) Coat the sizing agent I-1 obtained in step (1) on the glass fiber fabric surface at 800 g / m 2 Then dry it to form a film at 80 °C to obtain the fiber fabric I-2;

[0095] (3) Take two layers of the fiber fabric I-2 obtained in step (2), bond the sides coated with the sizing agent "face to face", and then reinforce it by sewing technology to obtain the three-dimensional fabric I-3;

[0096] (4) Add reduced graphene oxide powder, carbon nanotubes and carbon black into epoxy resin, stir and mix at 300 r / min for 20 min, and grind to a fineness less than 20 μm to obtain a mixed resin matrix II-1. Among them, the total concentration of reduced graphene oxide powder, carbon nanotubes and carbon black is 3 wt%, and the epoxy resin system is E-44:TTA-26:DDA-10:U-415 = 45:33.7:20:0.2;

[0097] (5) Apply the mixed resin matrix II-1 obtained in step (4) evenly onto the release paper at 800 g / m 2 Then double-sidedly cover it onto the three-dimensional fabric I-3 obtained in step (3), and perform hot pressing and impregnation at 100 °C. The pressure of the hot pressing roller is 0.3 MPa, the drying length of the impregnation section is 30 m, and the hot pressing and impregnation time is 6 min to obtain a prepreg with a high content of high-carbon absorbing agent.

[0098] Example 9

[0099] A preparation method of a prepreg with a high content of high-carbon absorbing agent includes the following steps:

[0100] (1) Mix reduced graphene oxide powder, methyl ethyl ketone and GE-20 in a mass ratio of 60:20:20, stir at 500 r / min for 60 min, and grind to a fineness less than 20 μm to obtain adhesive solution I-1;

[0101] (2) Apply the adhesive solution I-1 obtained in step (1) onto the glass fiber cloth surface at 3000 g / m 2 Then dry it into a film at 100 °C to obtain fiber fabric I-2;

[0102] (3) Take two layers of the fiber fabric I-2 obtained in step (2), stick the sides coated with the adhesive solution "face to face", and then reinforce it by stitching technology to obtain three-dimensional fabric I-3;

[0103] (4) Add reduced graphene oxide powder into epoxy resin, stir and mix at 1000 r / min for 30 min, and grind to a fineness less than 20 μm to obtain a mixed resin matrix II-1. Among them, the concentration of reduced graphene oxide powder is 5 wt%;

[0104] (5) Apply the mixed resin matrix II-1 obtained in step (4) evenly onto the release paper at 1000 g / m 2 Then double-sidedly cover it onto the three-dimensional fabric I-3 obtained in step (3), and perform hot pressing and impregnation at 150 °C to obtain a prepreg with a high content of high-carbon absorbing agent.

[0105] Comparative Example 1

[0106] A preparation method of the adhesive solution of a prepreg includes the following steps:

[0107] (1) Mix reduced graphene oxide powder: methyl ethyl ketone: GE-20 at a ratio of 75:20:5, stir at 100 r / min for 50 min at 25°C.

[0108] Graphene has a large specific surface area. At this time, the addition amounts of the solvent and monomer diluent are not sufficient to completely wet the graphene, and there is a large amount of dry powder, so the formulated slurry cannot be completed.

[0109] Comparative Example 2

[0110] A composite fiber cloth with a single-sided enriched wave-absorbing agent, and its preparation method includes the following steps

[0111] (1) Mix reduced graphene oxide powder: methyl ethyl ketone: GE-20 at a ratio of 50:49:1, stir at 100 r / min for 40 min at 25°C, and grind to a fineness of less than 20 μm to obtain adhesive solution I-1;

[0112] (2) Use release paper as the substrate, and roll coat adhesive solution I-1 onto the glass fiber cloth by single-sided coating. The coating amount is 980 g / m 2 , the coating temperature is 40°C, dry and form a film at 80°C, the drying oven length is 30 m, and the production speed is 3 m / min to obtain a composite fiber cloth with a single-sided enriched wave-absorbing agent.

[0113] Wind the above-mentioned composite fiber cloth with a single-sided enriched wave-absorbing agent in the reverse direction, with the wave-absorbing agent enrichment side facing outwards. During the winding process, a large amount of the dried powder falls off, and it is impossible to ensure that the wave-absorbing agent reaches the designed content; it shows that the monomer diluent is too little to effectively adhere the wave-absorbing agent; thus, the subsequent preparation process cannot be carried out.

[0114] Test Example 1

[0115] Respectively cut the wave-absorbing prepregs with high-carbon-based wave-absorbing agent contents prepared in Examples 1-6 into sheets with a size of 300 mm×300 mm, lay 5 pieces of the cut prepregs in sequence in the mold to reach the predetermined thickness. After the laying is completed, wrap it with a vacuum bag, assemble a vacuum valve, and prepare for curing in the autoclave; use a step-by-step temperature and pressure increase curing system (70°C / 3 bar / 1 h, 90°C / 5 bar / 2 h, and 110°C / 7 bar / 2 h in sequence) for hot pressing and curing to form a stealth composite material test sample with a high-carbon-based wave-absorbing agent content (as Figure 5 shown).

[0116] Use the bow method of the national military standard GJB2038A-2011 to test the wave-absorbing efficiency of the prepared stealth composite material. According to the test requirements, trim the composite material into the size of the test sample, assemble it on the device, and measure the reflection loss in the frequency range of 2-18 GHz to characterize the wave-absorbing performance. The test results are shown in Table 1.

[0117] Table 1 Test Results of Absorbing Efficiency of Stealth Composite Materials

[0118]

[0119] As can be seen from Table 1, the test samples of stealth composite materials prepared from the absorbing prepregs with the high-carbon absorbing agent contents in Examples 1-6 all have high absorbing efficiency.

[0120] Compared with absorbing agents such as carbonyl iron absorbing agent that will significantly increase the weight of the material, the carbon-based absorbing agent has the characteristics of low density, large specific surface area and strong oil absorption, and it is very difficult to achieve high-content addition in the resin formulation system. However, after the adhesive solution is dried in this scheme, the content of the carbon-based absorbing agent can exceed 90 wt%, and the total content of the carbon-based absorbing agent in the prepreg also reaches 70 wt%. While improving the absorbing efficiency of the prepreg, it is also beneficial to reduce the weight of the material.

[0121] Test Example 2

[0122] Use different proportion components to test the effect of this preparation method. The specific steps are as follows:

[0123] (1) Mix the reduced graphene oxide powder, methyl ethyl ketone and GE-22 in different proportions as shown in Table 2, stir at 100 r / min for 40 min, and grind to a fineness less than 20 μm to obtain adhesive solution I-1;

[0124] Table 2 Mixing Ratio Table of Each Component in the Adhesive Solution

[0125]

[0126] (2) Coat the adhesive solution I-1 obtained in step (1) onto the quartz fiber cloth surface at 960 g / m 2 、450 g / m 2 、235 g / m 2 、340 g / m 2 and 110 g / m 2 respectively, and then dry and form a film at 80 °C to obtain fiber cloths 1-I-2, 2-I-2, 3-I-2, 4-I-2 and 5-I-2;

[0127] (3) Take two layers of the fiber cloths I-2 with the same number obtained in step (2), bond the sides coated with the adhesive solution "face to face", and then stitch and reinforce the two layers of cloths through an industrial sewing machine, with a needle weft spacing of 10 cm and continuous synchronous stitching to obtain three-dimensional cloths 1-I-3, 2-I-3, 3-I-3, 4-I-3 and 5-I-3;

[0128] (4)Add the reduced graphene oxide powder to the epoxy resin at the ratio shown in Table 3, stir and mix at 300 r / min for 30 min, and grind to a fineness of less than 20 μm to obtain the mixed resin matrices 1-II-1, 2-II-1, 3-II-1, 4-II-1, and 5-II-1;

[0129] Table 3 Mixing ratio table of each component in the mixed resin matrix

[0130]

[0131] (5)Apply the mixed resin matrix II-1 obtained in step (4) evenly onto the release paper at 100 g / m 2 Then, cover it on both sides onto the three-dimensional fabric I-3 obtained in step (3), and perform hot pressing and impregnation at 60 °C. The pressure of the hot pressing roller is 0.3 MPa, the drying length of the impregnation section is 30 m, and the hot pressing and impregnation time is 6 min to obtain the absorbent prepreg with a high carbon-based absorbent content.

[0132] It can be seen that the resin system, absorbent, fiber cloth, selection of the mixing ratio and type of each component, and the total addition amount of the absorbent in the prepreg can all be adjusted according to actual application requirements.

[0133] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, or improvements made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A preparation method of a microwave absorbing prepreg with a high carbon-based microwave absorbing agent content, characterized in that, It includes the following steps: (1) Stir, mix and grind and disperse a carbon-based wave-absorbing agent, a volatile solvent and an active monomer diluent to obtain adhesive solution I-1; the concentration of the carbon-based wave-absorbing agent in the adhesive solution I-1 is 20-60 wt%, and the concentration of the active monomer diluent is 5-20 wt%; (2) Coat the adhesive solution I-1 obtained in step (1) onto the surface of a fiber cloth, and then dry it into a film to obtain fiber cloth I-2; (3) Take two layers of the fiber cloth I-2 obtained in step (2), "face-to-face" bond the sides coated with the adhesive solution, and then reinforce it by stitching technology to obtain three-dimensional cloth I-3; (4) Add a carbon-based wave-absorbing agent to a resin matrix, stir, mix and grind and disperse it to obtain a mixed resin matrix II-1; the concentration of the carbon-based wave-absorbing agent in the mixed resin matrix II-1 is 0.5-5 wt%; (5) Use the hot melt impregnation method to impregnate the mixed resin matrix II-1 obtained in step (4) into the three-dimensional cloth I-3 obtained in step (3) to obtain a wave-absorbing prepreg with a high carbon-based wave-absorbing agent content; Among them, the resin matrix in step (4) is one of epoxy resin, cyanate resin and acrylate resin; the active monomer diluent used in step (1) corresponds to the resin matrix in step (4).

2. The preparation method of the microwave absorbing prepreg with the content of high-carbon series microwave absorbing agent as claimed in claim 1, characterized in that, In steps (1) and (4), the carbon-based wave-absorbing agent is at least one of graphene, carbon nanotubes, carbon black and silicon carbide.

3. The preparation method of the microwave absorbing prepreg with the content of high-carbon series microwave absorbing agent as claimed in claim 1, characterized in that, In steps (1) and (4), grind to a fineness of less than 20 μm.

4. The preparation method of the microwave absorbing prepreg with the content of high-carbon series microwave absorbing agent as claimed in claim 1, characterized in that, In step (2), the coating amount of the adhesive solution I-1 is 50-3000 g / m 2 .

5. The preparation method of the microwave absorbing prepreg with the content of high-carbon series microwave absorbing agent as claimed in claim 1, characterized in that, In step (2), the drying temperature is 60-100 °C.

6. The preparation method of the microwave absorbing prepreg with the content of high-carbon series microwave absorbing agent as claimed in claim 1, characterized in that In step (5), the steps of the hot melt impregnation method are as follows: The mixed resin matrix II-1 obtained in step (4) is uniformly coated on the release paper at 50-1000 g / m 2 Then, the three-dimensional fabric I-3 obtained in step (3) is covered, and hot pressing impregnation is carried out at 50-150 °C to obtain a prepreg with a high carbon-based wave absorber content.

7. A wave-absorbing prepreg with a high carbon-based wave-absorbing agent content prepared by the preparation method of the wave-absorbing prepreg with a high carbon-based wave-absorbing agent content according to any one of claims 1-6.

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