Microwave-absorbing prepreg and its preparation method and composite microwave-absorbing materials

Abstract

This invention relates to the field of microwave absorbing materials, specifically to microwave absorbing prepregs, their preparation methods, and composite microwave absorbing materials. The composite microwave absorbing material comprises two layers of adhesive film of equal thickness, and a fiber cloth sandwiched between the two layers. One layer of adhesive film has a microwave absorbing film disposed on its surface. The adhesive film comprises a first resin, which is one or more of high-temperature epoxy resin and bismaleimide resin. The microwave absorbing film comprises a microwave absorbing material and a second resin, which is one or more of high-temperature epoxy resin and bismaleimide resin. The composite microwave absorbing material provided by this invention has high peel strength, effectively avoiding the problems of delamination and peeling of composite microwave absorbing materials.

Description

Technical Field

[0001] This invention relates to the field of microwave absorbing materials technology, and more specifically, to microwave absorbing prepregs, their preparation methods, and composite microwave absorbing materials. Background Technology

[0002] With the technological advancements in the aerospace field, the performance requirements for microwave absorbing materials are gradually increasing. Combining electromagnetic microwave absorbing materials with prepreg manufacturing processes yields composite microwave absorbing materials that meet the requirements of being lightweight, thin, and strong. This is achieved by combining microwave absorbing materials with high-temperature resistant polymers to form an absorbing film, which is then coated onto the surface of a prepreg possessing high temperature resistance, high strength, and high toughness, resulting in a composite microwave absorbing material that combines microwave absorption performance with mechanical strength. However, in practical applications, insufficient interfacial bonding between the absorbing film and the prepreg can easily occur, leading to delamination and peeling between layers, ultimately causing the composite microwave absorbing material to fail.

[0003] In view of this, the present invention is proposed. Summary of the Invention

[0004] The purpose of this invention is to provide microwave absorbing prepreg, its preparation method, and composite microwave absorbing materials to improve the bonding strength between the microwave absorbing film and the prepreg.

[0005] This invention is implemented as follows: In a first aspect, the present invention provides a composite microwave absorbing material, which includes two layers of adhesive film and a fiber cloth sandwiched between the two layers of adhesive film, wherein a microwave absorbing film is disposed on the surface of one layer of adhesive film. The film includes a first resin, which is one or both of high-temperature epoxy resin and bismaleimide resin; The microwave absorbing film includes a microwave absorbing material and a second resin, wherein the second resin is one or both of high-temperature epoxy resin and bismaleimide resin.

[0006] In an optional embodiment, the first resin is a bismaleimide resin or a high-temperature epoxy resin; the second resin is a high-temperature epoxy resin. In an optional embodiment, the fiber cloth is one of quartz fiber cloth, aramid fiber cloth, or hybrid fiber cloth.

[0007] In an optional embodiment, the thickness of the fiber cloth is less than 0.1 mm; Optionally, the thickness of the adhesive film is 0.02mm to 0.04mm; Optionally, the thickness of the composite absorbing material is 10μm~20μm.

[0008] In an optional embodiment, the absorbing material is selected from one or two of carbon-based absorbing fillers and metal-based absorbing materials.

[0009] Secondly, the present invention provides a method for preparing the above-mentioned composite microwave absorbing material, comprising the following steps: (1) Preparation of prepreg: A first resin is used to form a first adhesive film and a second adhesive film; a fiber cloth is sandwiched between the first adhesive film and the second adhesive film to form a prepreg. (2) Preparation of composite absorbing materials: After mixing the second resin and the microwave absorbing material, a conductive paste is obtained, which is then screen-printed or inkjet-printed onto the prepreg and cured to obtain the composite microwave absorbing material. The first resin is selected from one or two of high-temperature epoxy resin and bismaleimide resin; the second resin is selected from one or two of high-temperature epoxy resin and bismaleimide resin.

[0010] In an optional embodiment, the areal density of the first and second adhesive films is 32.5-34.5 g / m³. 2 .

[0011] In an optional implementation, step (2), curing includes: Hold at 110~130℃ for 30~90 min, then hold at 180~200℃ for 150~200 min.

[0012] In an optional embodiment, the mass ratio of the second resin to the microwave absorbing material is 35~40:16.

[0013] Thirdly, the present invention provides a prepreg prepared using the above method.

[0014] The present invention has the following beneficial effects: The prepreg provided by this invention uses two layers of adhesive film sandwiched with fiber cloth to ensure uniform resin distribution, which is beneficial for bonding with the absorbing film. Simultaneously, by matching and synergistically using the resin materials in the prepreg and absorbing film, this invention significantly improves interfacial compatibility and interlayer bonding strength, resulting in a composite absorbing material with high peel strength, effectively avoiding the problems of delamination and peeling in composite absorbing materials. Furthermore, the preparation method of the composite absorbing material provided by this invention is low-cost, fast-processing, and suitable for large-scale industrial production. Detailed Implementation

[0015] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments whose manufacturers are not specified are all conventional products that can be purchased commercially.

[0016] This invention provides a composite microwave absorbing material, comprising two layers of adhesive film and a fiber cloth sandwiched between the two layers of adhesive film, wherein a microwave absorbing film is disposed on the surface of one layer of adhesive film; the adhesive film comprises a first resin, which is one or two of high-temperature epoxy resin and bismaleimide resin; the microwave absorbing film comprises a microwave absorbing material and a second resin, which is one or two of high-temperature epoxy resin and bismaleimide resin.

[0017] The composite microwave absorbing material provided in this invention is prepared by coating a prepreg with a microwave absorbing film. The use of two layers of adhesive film sandwiching a fiber cloth improves the uniformity of the prepreg, reduces internal bubbles and defects, enhances the load-bearing capacity of the prepreg, and creates a smoother interface, which is beneficial for interfacial bonding with the microwave absorbing film. Furthermore, by coordinating the selection of the first and second resins, the interfacial compatibility between the microwave absorbing film and the adhesive film is controlled, improving the interfacial bonding strength. This results in a 90-degree peel strength of 3.4~4.2 N / mm for the obtained composite microwave absorbing material.

[0018] In an optional embodiment, the first adhesive film and the second adhesive film are of the same thickness.

[0019] In an optional embodiment, the first resin is a high-temperature epoxy resin, and the second resin is a high-temperature epoxy resin.

[0020] Optionally, the high-temperature epoxy resin is one or both of CH101 and ZYEH200.

[0021] In an optional embodiment, the first resin is a bismaleimide resin or a high-temperature epoxy resin; the second resin is a high-temperature epoxy resin.

[0022] Optionally, the first resin is a bismaleimide resin and the second resin is a high-temperature epoxy resin.

[0023] Optionally, the bismaleimide resin is one or both of XS-058 and 3503, and the high-temperature epoxy resin is one or both of CH101 and ZYEH200.

[0024] Generally speaking, films made of different types of resins may have interfacial incompatibility when bonded, resulting in low bonding strength and easy peeling. However, this invention has found that a prepreg made of high-temperature epoxy resin as the resin matrix and a microwave absorbing film made of bismaleimide resin as the resin matrix have a better interfacial bond, with a 90-degree peel strength of up to 4.2 N / mm.

[0025] In an optional embodiment, the fiber cloth is one of quartz fiber cloth, aramid fiber cloth, or hybrid fiber cloth.

[0026] Optionally, the thickness of the fiber cloth is less than 0.1 mm.

[0027] Optionally, the thickness of the adhesive film is 0.02mm to 0.04mm.

[0028] Optionally, the thickness of the composite absorbing material is 10μm~20μm.

[0029] The composite absorbing material prepared in this application has a low thickness and is suitable for aerospace structural components, automotive radar, general electromagnetic compatibility (EMC) and other fields. This requires the composite absorbing material to not only perform the function of absorbing waves, but also to bear the load in some cases. If the absorbing film and the prepreg are not well bonded, they will directly delaminate and peel off during the stress or curing process. However, this application significantly improves the overall structural stability and mechanical load-bearing capacity of the composite absorbing material by optimizing the selection of resin types for the prepreg film and the absorbing film. Its 90-degree peel strength can reach 1.9~4.2 N / mm.

[0030] Optionally, the absorbing material is selected from one or two of carbon-based fillers and metal-based absorbing materials.

[0031] Optionally, the carbon-based filler is one or more of carbon nanotubes, carbon black, and graphite; the metal-based microwave absorbing material is one or more of metallic silver and silver-clad copper.

[0032] This invention provides a method for preparing composite microwave absorbing materials, comprising the following steps: (1) Preparation of prepreg: A first resin is used to form a first adhesive film and a second adhesive film; a fiber cloth is sandwiched between the first adhesive film and the second adhesive film to form a prepreg. (2) Preparation of composite absorbing materials: After mixing the second resin and the microwave absorbing material, a conductive paste is obtained, which is then screen-printed onto the prepreg and cured to obtain a composite microwave absorbing material. The first resin is selected from one or two of high-temperature epoxy resin and bismaleimide resin; the second resin is selected from one or two of high-temperature epoxy resin and bismaleimide resin.

[0033] In an optional embodiment, the method for preparing the prepreg is as follows: Break the first resin into small pieces, place them in the resin bath for dissolution, and thread the release cloth through. Start the process, and once the release cloth is straightened, close the roller gap. The initial roller gap is 0 mm. After coating for 1.5-1.6 m, open the roller gap. At the end, use a tool to sample and test the areal density, and adjust the roller gap to ensure the average areal density of the coating tip reaches 32.5-34.5 g / m². 2After the areal density meets the standard, the heating roller is started to begin coating, and a PE film is pasted onto the surface of the adhesive film. The length of the film is observed; once the specified length is reached, a sample is taken to test the areal density and thickness. The process continues for another 14-14.1 m on the blank release cloth before stopping. Using the above method, the first and second adhesive films are coated onto the release paper and release cloth respectively. Then, the fiber cloth is precisely placed between the two adhesive films, and resin impregnation is achieved by pressing with a hot roller to obtain the prepreg.

[0034] In an optional embodiment, after the prepreg is prepared, the prepreg is pretreated, specifically as follows: Using a cutting machine, cut the prepreg to a size of 500 mm * 600 mm. Pull the prepreg onto the cutting table, with the release liner facing down, and cut it into sheets. First, lay another layer of release liner on a metal plate fixture. Remove the PE film from each sheet of prepreg, placing it with the release liner facing down, stacking each sheet (≤200pcs). Ensure the edges of the prepreg are aligned as much as possible. Then, stack the peelable fabric, non-porous release film, breathable felt, and vacuum bag in sequence. Place two vacuum nozzles diagonally on the fixture. Apply vacuum to 0.9 bar, ensuring the vacuum pressure drops only 0.008 bar per minute. Place the stacked prepreg material in an oven for curing. Separate each sheet of material, ensuring the prepreg and release liner remain in place.

[0035] In an optional embodiment, the method for preparing the composite absorbing material is as follows: The second resin and the microwave absorbing material were initially mixed at a mass ratio of (35~40):16 using a constant speed stirrer, and then ball-milled at 200 RPM / min~300 RPM / min for 1~3 h to obtain a conductive paste. The uniformly mixed conductive paste was placed above the screen of a screen printing machine, and the printing squeegee of the screen printing machine was moved in contact with the screen to print the conductive paste on the screen onto the prepreg substrate below the screen. Finally, the printed film was kept at 110~130℃ for 30~90 min, followed by 180~200℃ for 150~200 min to obtain the composite microwave absorbing material.

[0036] Optionally, the release fabric is a polytetrafluoroethylene release fabric.

[0037] Optionally, the polytetrafluoroethylene release fabric is G234TFNP-145 release fabric.

[0038] This invention also provides prepreg prepared using the above method.

[0039] The features and performance of the present invention will be further described in detail below with reference to embodiments.

[0040] Example 1 In this embodiment, the first resin is cyanate ester resin M1205, the second resin is cyanate ester resin CO1MO, and the fiber cloth is twill quartz glass fiber cloth.

[0041] (1) Preparation of prepreg S1: Break the first resin into small pieces, place them in the mortar for dissolution, and thread the release cloth through. Start the process, and once the release cloth is straightened, close the roller gap. The initial gap between the left and right rollers is 0 mm. After coating for 1.5-1.6 m, open the roller gap. At the end, use a tool to sample and test the areal density, and adjust the roller gap to ensure that the average areal density of the coating at the front end reaches 32.5-34.5 g / m². 2 Once the areal density meets the standard, start the heating roller to begin coating, and then attach the PE film to the surface of the adhesive film. Observe the length of the film; after reaching the specified length, take a sample to test the areal density and thickness, and continue running the blank release cloth for 14-14.1 m before stopping.

[0042] The second adhesive film is obtained by coating the release paper in the same manner as described above.

[0043] S2: Composite of adhesive film and fiber cloth After the laminating equipment reaches the set temperature, maintain the temperature for 60-70 minutes. After the maintenance period, calibrate the gap between the three sets of heating rollers to ensure it is 0.40 mm. Place the upper and lower adhesive films onto the machine, threading the release paper film and the release cloth film onto the upper and lower parts respectively. Use high-temperature tape to splice and pull the upper and lower adhesive films to the release paper at the tail end of the machine, and then peel off the PE film. Turn off the fiber cloth tension, lay the fiber cloth flat, turn on the winding tension and unwinding tension, and close the traction roller. When the adhesive film passes the heating roller, slowly place the fiber cloth between the upper and lower adhesive films. Once the fiber cloth is straightened, turn on the tension, close the heating roller, and mark this point. When the mark passes the cooling table, lift the release paper of the upper adhesive film from the mark and begin the paper winding. Align the PE flat film left and right, attach it above the release cloth, and pass it through the laminating roller. Once the PE flat film is straightened, close the laminating roller, and finally, rewind the finished product.

[0044] (2) Pretreatment of prepreg Using a cutting machine, cut the prepreg to a size of 500 mm x 600 mm. Pull the prepreg onto the cutting table, with the release liner facing down, and cut it into sheets. First, lay another layer of release liner on a metal plate fixture. Remove the PE film from each sheet of prepreg, placing it with the release liner facing down, stacking up to 200 sheets. Ensure the edges of the prepreg are aligned as much as possible. Then, stack the peelable fabric, non-porous release film, breathable felt, and vacuum bag in sequence. Place two vacuum nozzles diagonally on the fixture. Apply vacuum to 0.9 bar, ensuring the vacuum pressure drops only 0.008 bar per minute. Place the stacked prepreg in an oven for curing. Separate each sheet of material, ensuring the prepreg and release liner remain in place.

[0045] (3) Preparation of composite absorbing materials S1: Mix cyanate ester resin and carbon black filler at a mass ratio of 36:16 using a constant speed stirrer, and then ball mill at 300 RPM / min for 2 hours before use.

[0046] S2: Place the uniformly mixed conductive paste above the screen of a screen printing machine. Move the squeegee of the screen printing machine in contact with the screen to transfer the conductive paste from the screen to the prepreg substrate below the screen. Finally, cure the printed absorbing film at 120℃ for 60 min and then at 190℃ for 180 min to obtain the composite absorbing material. The thickness of the electromagnetic absorbing films coated in the same batch ranges from 10 μm to 20 μm; the total thickness of the resulting composite absorbing material is between 0.16 mm and 0.20 mm.

[0047] The composite absorbing material prepared in this embodiment has an average peel strength of 1.9 N / mm at 90 degrees.

[0048] Example 2 In this embodiment, the first resin is high-temperature epoxy resin CH101, the second resin is high-temperature epoxy resin ZYEH200, and the fiber cloth is twill quartz glass fiber cloth.

[0049] The composite absorbing material prepared in this embodiment has an average peel strength of 3.4 N / mm at 90 degrees.

[0050] Example 3 This embodiment is basically the same as Embodiment 1, except that the first resin is bismaleimide resin XS-058 and the second resin is high-temperature epoxy resin ZYEH200.

[0051] The composite absorbing material prepared in this embodiment has an average peel strength of 4.2 N / mm at 90 degrees.

[0052] Example 4 This embodiment is basically the same as Embodiment 1, except that the first resin is cyanate ester resin M1205 and the second resin is high-temperature epoxy resin ZYEH200.

[0053] The composite absorbing material prepared in this embodiment has an average peel strength of 2.1 N / mm at 90 degrees.

[0054] Comparative Example 1 This comparative example is basically the same as Example 1, except that it uses inkjet printing technology.

[0055] The composite absorbing material prepared in this embodiment has an average peel strength of 0.5 N / mm at 90 degrees.

[0056] Comparative Example 2 This embodiment is basically the same as Embodiment 1, except that the first resin is polyimide resin WPI-350 and the second resin is polyimide resin ZTS-350.

[0057] The composite absorbing material prepared in this embodiment has an average peel strength of 1.4 N / mm at 90 degrees.

[0058] Comparative Example 3 This embodiment is basically the same as Embodiment 1, except that the substrate does not use a prepreg type, but a high-temperature resistant polyimide film is selected; and the second resin is high-temperature epoxy resin ZYEH200.

[0059] The composite absorbing material prepared in this embodiment has an average peel strength of 0.5 N / mm at 90 degrees.

[0060] In summary, the composite absorbing material provided by this invention, through the coordinated use of the first resin and the second resin, significantly improves the interfacial bonding ability between the prepreg and the absorbing film, with a typical 90-degree peel strength of 4.2 N / mm, effectively preventing delamination and peeling of the composite absorbing material during use.

[0061] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A composite microwave absorbing material, characterized in that, The composite absorbing material includes two layers of adhesive film and a fiber cloth sandwiched between the two layers of adhesive film, wherein an absorbing film is disposed on the surface of one layer of adhesive film. The adhesive film includes a first resin, which is one or two of cyanate ester resin, high-temperature epoxy resin, and bismaleimide resin. The microwave absorbing film includes a microwave absorbing material and a second resin, wherein the second resin is one or two of cyanate ester resin, high-temperature epoxy resin, and bismaleimide resin.

2. The composite absorbing material according to claim 1, characterized in that, The first resin is a bismaleimide resin or a high-temperature epoxy resin; the second resin is a high-temperature epoxy resin.

3. The composite absorbing material according to claim 1, characterized in that, The fiber cloth is one of quartz fiber cloth, aramid fiber cloth, or mixed fiber cloth.

4. The composite microwave absorbing material according to any one of claims 1 or 3, characterized in that, The thickness of the fiber cloth is less than 0.1 mm; Optionally, the thickness of the adhesive film is 0.02mm to 0.04mm; Optionally, the thickness of the composite absorbing material is 10μm to 30μm.

5. The composite absorbing material according to claim 1, characterized in that, The microwave absorbing material is selected from one or two of carbon-based microwave absorbing fillers and metal-based microwave absorbing materials.

6. The method for preparing the composite absorbing material as described in claim 1, characterized in that, Includes the following steps: (1) Preparation of prepreg: A first resin is used to form a first adhesive film and a second adhesive film; a fiber cloth is sandwiched between the first adhesive film and the second adhesive film to form a prepreg. (2) Preparation of composite absorbing materials: After mixing the second resin and the microwave absorbing material, a conductive paste is obtained, which is then screen-printed or inkjet-printed onto a prepreg and cured to obtain the composite microwave absorbing material. The first resin is selected from one or two of high-temperature epoxy resin and bismaleimide resin; the second resin is selected from one or two of high-temperature epoxy resin and bismaleimide resin.

7. The preparation method according to claim 6, characterized in that, The areal density of the first and second adhesive films is 32.5-34.5 g / m³. 2 .

8. The preparation method according to claim 6, characterized in that, The mass ratio of the second resin to the microwave absorbing material is 35~40:

16.

9. The preparation method according to claim 6, characterized in that, In step (2), the curing includes: Hold at 110~130℃ for 30~90 min, then hold at 180~200℃ for 150~200 min.

10. The prepreg prepared by the preparation method as described in claim 6.