An outer heat-proof load-bearing and inner heat-insulating integrated cover body and a preparation method thereof

Abstract

The application provides an outer heat-proof load-bearing and inner heat-insulating integrated cover body and a preparation method thereof, and belongs to the technical field of load-bearing and heat-proof integrated composite materials. The cover body comprises an outermost heat-proof load-bearing layer, an innermost heat-insulating layer and an intermediate adhesive film layer. The heat-proof load-bearing layer is made of fiber reinforced benzoxazine resin, the heat-insulating layer is made of phosphazene rubber, silicone rubber or nitrile rubber, and the adhesive film layer is made of modified benzoxazine adhesive film. The application realizes co-curing of the outer heat-proof load-bearing layer and the inner heat-insulating layer, and solves the interface problem of the outer heat-proof load-bearing layer and the inner heat-insulating layer through preparation and coating of the modified benzoxazine adhesive film.

Description

An integrated heat-resistant and heat-insulating cover with external heat protection and internal heat insulation, and its preparation method. Technical Field

[0001] This invention relates to an integrated heat-resistant and heat-insulating cover and its preparation method, belonging to the technical field of load-bearing heat-resistant integrated composite materials. Background Technology

[0002] Traditional metal structures are heavy and have long processing cycles, making it difficult to meet the lightweight and high-strength requirements of the aerospace industry in some aspects. In recent years, advanced resin-based composite materials have flourished, and composite materials are being used more and more widely in the aerospace field. However, current aerospace composite material products are still mainly single-function components and non-load-bearing structural components. Composite material components with different structures and functions still need to be molded separately and then assembled or connected to meet multi-functional usage requirements. These processes are complex and increase product weight. Therefore, under the new trend of lightweight composite material structures, integrated and lightweight design solutions are extremely important.

[0003] Traditional external heat shields with internal insulation primarily use metal materials for their outer load-bearing layer, creating a pressing need for lightweight construction. Furthermore, the molding process for these shields still suffers from numerous bonding interfaces. Under prolonged exposure to high-temperature airflow, the shield's sealing and ablation resistance properties deteriorate significantly, resulting in poor process operability. The development of multifunctional integrated products focuses on achieving product functionality and integrated production. On one hand, it requires meeting the corresponding performance indicators for each functional layer. On the other hand, the molding conditions for different functional layers generally differ, and interface issues exist between them. Achieving integrated manufacturing of different functional layers within a single product while meeting process requirements is a key challenge. Therefore, effective control and improvement of the fabrication process for external heat shields with internal insulation components are needed to achieve integrated molding and provide technical support for future development. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings of the prior art. In response to the requirements of external heat-bearing and internal heat insulation functions of products, this invention focuses on the realization of integrated molding and good processability, and provides an integrated external heat-bearing and internal heat-insulating cover and its preparation method. It realizes the co-curing of the external heat-bearing layer and the internal heat insulation layer, and solves the interface problem between the external heat-bearing layer and the internal heat insulation layer by preparing and laying a modified benzoxazine adhesive film.

[0005] The technical solution of this invention:

[0006] An integrated heat-resistant and heat-insulating cover includes an outermost heat-resistant load-bearing layer, an innermost heat-insulating layer, and an intermediate adhesive film layer. The heat-resistant load-bearing layer is made of fiber-reinforced benzoxazine resin, the heat-insulating layer is made of phosphazene rubber, silicone rubber, or nitrile rubber, and the adhesive film layer is made of modified benzoxazine adhesive film.

[0007] Furthermore, the resin matrix of the fiber-reinforced benzoxazine resin is a bifunctional benzoxazine compound, including at least one of a diphenolic benzoxazine or a diamine-type benzoxazine, with the monomer structure as follows:

[0008]

[0009] Wherein, X is one of -CH2-, -SO2-, and -O-; R1 and R2 are one of hydrogen and alkyl groups.

[0010] Furthermore, the fiber used in the fiber-reinforced benzoxazine resin is an ablation-resistant fiber with good mechanical properties at higher temperatures; the fiber type is a high-performance fiber commonly used in the field, such as glass fiber, quartz fiber, carbon fiber or aramid fiber, etc.

[0011] Furthermore, the total thickness of the heat-resistant load-bearing layer is 5-10 mm. A greater thickness results in better ablation resistance of the outer heat-resistant layer, but it increases the weight of the aircraft and affects its payload. The thickness of the insulation layer is 3-5 mm. A greater thickness results in better insulation performance and lower temperatures when transferred to the heat-resistant load-bearing layer, but it also increases the weight. Moreover, the overall thickness of the enclosure is also affected by factors such as aerodynamic conditions. Those skilled in the art select the thickness of the heat-resistant load-bearing layer and the insulation layer based on the specific requirements for load-bearing, heat protection, and insulation performance.

[0012] Furthermore, the thickness of the adhesive film layer is 0.4–0.8 mm.

[0013] Furthermore, the inner rubber insulation layer uses phosphazene rubber, silicone rubber, or nitrile rubber raw sheets as raw materials.

[0014] Furthermore, the raw materials used in the modified benzoxazine film, by weight, include 20-40 parts of a bifunctional benzoxazine compound, 20-40 parts of a monofunctional benzoxazine compound, 15-25 parts of an auxiliary toughening agent, 5-10 parts of a curing agent, 5-12 parts of a vulcanizing agent, and 1-4 parts of a filler.

[0015] A method for preparing an integrated heat-resistant and heat-insulating cover includes the following steps:

[0016] 1) Place raw phosphazene rubber, silicone rubber or nitrile rubber sheets between two gaskets and preform them on a plate vulcanizing machine to obtain preformed rubber sheets;

[0017] Fiber-reinforced benzoxazine resin is prepared into fiber-reinforced benzoxazine resin prepreg by hot melt method, which is then laid up and placed in an oven for prepolymerization treatment to obtain pre-formed prepreg layup parts;

[0018] The modified benzoxazine resin system was prepared into a liquid, and then prepolymerized and pressed into a film to obtain a modified benzoxazine film.

[0019] 2) Lay the pre-formed rubber sheet onto the cover mold and use vacuuming to make the rubber sheet adhere tightly;

[0020] The modified benzoxazine film was laid on the rubber sheet;

[0021] The pre-formed prepreg layup is bonded onto the modified benzoxazine film to form a three-layer structure;

[0022] 3) The three-layer structure is cured in an autoclave, then cooled and demolded;

[0023] 4) The obtained integrated heat protection and internal insulation cover is processed by drilling, trimming and polishing according to the standard external surface dimensions to obtain a high-precision integrated heat protection and internal insulation cover.

[0024] Furthermore, the preparation steps of the modified benzoxazine film include:

[0025] a) Weigh 20-40 parts by weight of a difunctional benzoxazine compound, 20-40 parts by weight of a monofunctional benzoxazine compound, 15-25 parts by weight of an auxiliary toughening agent, 5-10 parts by weight of a curing agent, 5-12 parts by weight of a vulcanizing agent and 1-4 parts by weight of a filler, and mix them to obtain a modified benzoxazine resin system.

[0026] b) The above modified benzoxazine resin system is stirred at a stirring rate of 1000-5000 r / min and at a temperature of 80-150°C for 1-5 h until it is uniformly mixed to obtain a glue solution.

[0027] c) Preheat the above adhesive solution in an oven at 40-70°C for 30 minutes, and then press it into a film on a calender at a roll temperature of 70-90°C to obtain a modified benzoxazine film.

[0028] Furthermore, the hot-press curing conditions in step 3) include heat preservation at 100±3℃ for 0.5h, pressure curing at 140±3℃ for 4h with a curing pressure not lower than 0.8Mpa, and then post-treatment at 160±℃ for 1h; the demolding conditions are demolding when the temperature drops to below 40℃.

[0029] The beneficial effects of this invention compared to the prior art are as follows:

[0030] 1. The modified benzoxazine adhesive film material used in this invention has good self-adhesion and excellent adhesion to insulation layers composed of phosphazene rubber, silicone rubber, or nitrile rubber. At the same time, the film thickness is uniform and the unit area mass is precisely controllable, ensuring the stability and reliability of the co-curing and bonding of fiber-reinforced benzoxazine resin prepreg and insulation layer. In addition, during the temperature curing process, there is no uncontrolled adhesive layer phenomenon caused by aggregation as with traditional paste adhesives, ensuring the stability and reliability of the co-curing and bonding of the composite material shell (i.e., the heat-resistant load-bearing layer) of the high-speed aircraft housing and the insulation layer.

[0031] 2. The integrated external heat-resistant and internal heat-insulating cover component of this invention adopts a composite structure with different functional layers, resulting in a lower weight compared to components made of metal. The heat-resistant load-bearing layer and the heat-insulating layer work together to achieve a balance between the heat-resistant load-bearing capacity and the heat-insulating performance of the cover component while reducing structural weight.

[0032] 3. The cover component of the present invention is made of composite material. The thickness and material of the heat-resistant bearing layer and the heat insulation layer can be adjusted as needed, and each functional layer can better play its respective role, with strong design flexibility. Attached Figure Description

[0033] Figure 1 is a structural schematic diagram of an integrated outer heat-resistant and inner heat-insulating cover according to the present invention.

[0034] In the diagram: 1-heat-resistant bearing layer, 2-adhesive film layer, 3-heat insulation layer. Detailed Implementation

[0035] To make the various technical features, advantages, or effects of the present invention more apparent and understandable, a detailed description is provided below in conjunction with the accompanying drawings.

[0036] The structure of the integrated heat-resistant and heat-insulating cover proposed in this invention is shown in Figure 1. It consists of a heat-resistant layer as the outermost layer and an insulation layer as the inner layer, which are bonded together by an adhesive film. The heat-resistant layer is made of fiber-reinforced benzoxazine resin material, in which the high-performance fiber is an ablation-resistant fiber with good mechanical properties at high temperatures. The insulation layer is made of phosphazene rubber, silicone rubber, or nitrile rubber. The adhesive film layer is mainly composed of benzoxazine, and undergoes toughening and formulation modification to provide good formability, lay-up properties, and strength.

[0037] Example 1:

[0038] The heat-bearing layer of an integrated external heat-bearing and internal heat-insulating cover is 10mm thick and is reinforced with T300 plain weave carbon cloth and bisphenol A benzoxazine resin; the heat insulation layer is a 5mm thick phosphazene rubber layer; the adhesive film layer is 0.8mm thick, and the total thickness of the cover is 15.8mm.

[0039] The specific manufacturing steps of an integrated heat-resistant and heat-insulating cover are as follows:

[0040] 1. Preparation of phosphazene rubber preforms:

[0041] 1.1. Roll the phosphazene rubber raw material into sheets with a thickness of 1.0mm and 0.5mm, and cut them into 400mm*400mm pieces;

[0042] 1.2. A sandwich structure is formed by sandwiching the raw phosphazene rubber sheet between the upper and lower gaskets. The gaskets are used to control the thickness of the pre-formed rubber. The sandwich structure is placed on a flat vulcanizing machine for pre-forming (1.0 MPa, 80℃, 60 min) to ensure that the phosphazene rubber material is relatively flat and wrinkle-free.

[0043] 1.3. Cut the pre-formed phosphazene rubber sheet to the required dimensions for later use.

[0044] 2. Preparation of modified benzoxazine film:

[0045] 2.1. Weigh 40 parts by weight of a difunctional benzoxazine compound, 40 parts by weight of a monofunctional benzoxazine compound, 25 parts by weight of an auxiliary toughening agent, 10 parts by weight of a curing agent, 12 parts by weight of a vulcanizing agent and 4 parts by weight of a filler, and mix them to obtain a modified benzoxazine resin system.

[0046] 2.2. The modified benzoxazine resin system was stirred at a stirring rate of 1000 r / min at a constant temperature of 150°C for 1 h until it was uniformly mixed to obtain a glue solution.

[0047] 2.3. The above adhesive solution is preheated in an oven at 40°C for 30 minutes, and then pressed into a film on a calender at a roll temperature of 90°C to obtain a modified benzoxazine adhesive film.

[0048] 3. Preparation of prepreg layup components:

[0049] 3.1. Bisphenol A type benzoxazine resin was used to prepare T300 plain weave carbon cloth reinforced bisphenol A type benzoxazine resin prepreg by hot melt method.

[0050] 3.2. The obtained T300 plain weave carbon cloth reinforced bisphenol A type benzoxazine resin prepreg is cut according to the cover structure dimensions to obtain prepreg, and then laid up to obtain a prepreg layup part of about 12mm;

[0051] 3.3. The obtained prepreg layup is placed in an oven for prepolymerization treatment at 90℃ for 2 hours to obtain a preformed prepreg layup.

[0052] 4. Preparation of a three-layer structure of carbon fiber reinforced benzoxazine prepreg / film / phosphazene rubber:

[0053] 4.1. Adhere the pre-formed phosphazene rubber sheet from step 1.3 onto the metal mold of the cover, and use vacuuming to ensure the rubber sheet adheres tightly;

[0054] 4.2 Cut the modified benzoxazine film obtained in step 2.3 into the required size, lay it on the rubber sheet, and iron it properly with an electric iron to ensure good laying;

[0055] 4.3. The prepreg layup from step 3.3 is bonded to the adhesive film to form a three-layer structure of carbon fiber reinforced benzoxazine prepreg / adhesive film / phosphazene rubber;

[0056] 4.4. Perform autoclave curing. The curing regime is to keep at 100℃ for 0.5h, pressurize at 140℃ for 4h with a curing pressure of 0.8MPa, then post-treat at 160℃ for 1h, and then cool down to below 40℃ to demold and obtain the blank.

[0057] 4.5. The outer heat protection and inner heat insulation integrated cover blank obtained in the previous step is processed by drilling, trimming and polishing according to the standard outer surface dimensions to obtain a high-precision outer heat protection and inner heat insulation integrated cover component.

[0058] Example 2:

[0059] The heat-bearing layer of an integrated external heat-bearing and internal heat-insulating cover is 5mm thick and is made of quartz cloth reinforced with bisphenol A benzoxazine resin; the heat insulation layer is made of 3mm thick nitrile rubber; the adhesive film layer is 0.4mm thick, and the total thickness of the cover is 8.4mm.

[0060] The specific manufacturing steps of an integrated heat-resistant and heat-insulating cover are as follows:

[0061] 1. Preparation of nitrile rubber preforms:

[0062] 1.1. Roll the nitrile rubber raw material into sheets with a thickness of 1.0mm and 0.5mm, and cut them into 400mm*400mm pieces;

[0063] 1.2. A sandwich structure is formed by sandwiching a raw nitrile rubber sheet between two layers of gaskets. The gaskets are used to control the thickness of the pre-formed rubber. The sandwich structure is placed on a flat vulcanizing machine for pre-forming (1.0 MPa, 80℃, 60 min) to ensure that the nitrile rubber material is relatively flat and wrinkle-free.

[0064] 1.3. Cut the pre-formed nitrile rubber sheet to the required dimensions for later use.

[0065] 2. Preparation of modified benzoxazine film:

[0066] 2.1. Weigh 20 parts by weight of a difunctional benzoxazine compound, 20 parts by weight of a monofunctional benzoxazine compound, 15 parts by weight of an auxiliary toughening agent, 5 parts by weight of a curing agent, 5 parts by weight of a vulcanizing agent and 1 part by weight of a filler, and mix them to obtain a modified benzoxazine resin system.

[0067] 2.2. The above modified benzoxazine resin system was stirred at a stirring rate of 5000 r / min at a constant temperature of 80°C for 5 h until it was uniformly mixed to obtain a glue solution;

[0068] 2.3. The above adhesive solution is preheated in an oven at 70°C for 30 minutes, and then pressed into a film on a calender with a roll temperature of 70°C to obtain a modified benzoxazine adhesive film.

[0069] 3. Preparation of prepreg layup components:

[0070] 3.1. Bisphenol A type benzoxazine resin resin was used to prepare quartz cloth reinforced bisphenol A type benzoxazine resin prepreg by hot melt method, and quartz cloth reinforced bisphenol A type benzoxazine resin prepreg was obtained;

[0071] 3.2. The obtained quartz cloth reinforced bisphenol A type benzoxazine resin prepreg is cut according to the cover structure dimensions to obtain prepreg, and then laid up to obtain a prepreg layup part of about 7mm;

[0072] 3.3. The obtained prepreg layup is placed in an oven for prepolymerization treatment at 90℃ for 2 hours to obtain a preformed prepreg layup.

[0073] 4. Preparation of a three-layer structure of quartz fiber reinforced benzoxazine prepreg / film / nitrile rubber:

[0074] 4.1. Adhere the pre-formed nitrile rubber sheet from step 1.3 to the metal mold of the cover, and use vacuuming to ensure the rubber sheet adheres tightly;

[0075] 4.2 Cut the modified benzoxazine film obtained in step 2.3 into the required size, lay it on the rubber sheet, and iron it properly with an electric iron to ensure good laying;

[0076] 4.3. The prepreg layer preformed in step 3.3 is bonded to the adhesive film to form a three-layer structure of quartz fiber reinforced benzoxazine prepreg / adhesive film / nitrile rubber;

[0077] 4.4. Perform autoclave curing. The curing regime is to keep at 100℃ for 0.5h, pressurize at 140℃ for 4h with a curing pressure of 0.8MPa, then post-treat at 160℃ for 1h, and then cool down to below 40℃ to demold and obtain the blank.

[0078] 4.5. The outer heat protection and inner heat insulation integrated cover blank obtained in the previous step is processed by drilling, trimming and polishing according to the standard outer surface dimensions to obtain a high-precision outer heat protection and inner heat insulation integrated cover component.

[0079] Example 3:

[0080] The heat-bearing layer of an integrated external heat-bearing and internal heat-insulating cover is 8mm thick and is made of glass cloth reinforced bisphenol A benzoxazine resin; the heat insulation layer is a 4mm thick silicone rubber layer; the adhesive film layer is 0.6mm thick, and the total thickness of the cover is 12.6mm.

[0081] The specific manufacturing steps of an integrated heat-resistant and heat-insulating cover are as follows:

[0082] 1. Preparation of silicone rubber preforms:

[0083] 1.1. Roll the raw silicone rubber into sheets with a thickness of 1.0mm and 0.5mm, and cut them into 400mm*400mm pieces;

[0084] 1.2. A sandwich structure is formed by sandwiching a silicone rubber sheet between two layers of gaskets. The gaskets are used to control the thickness of the pre-formed rubber. The sandwich structure is placed on a flat vulcanizing machine for pre-forming (1.0MPa, 80℃, 60min) to ensure that the silicone rubber material is relatively flat and wrinkle-free.

[0085] 1.3. Cut the pre-formed silicone rubber sheet to the required dimensions for later use.

[0086] 2. Preparation of modified benzoxazine film:

[0087] 2.1. Weigh 30 parts by weight of a difunctional benzoxazine compound, 30 parts by weight of a monofunctional benzoxazine compound, 20 parts by weight of an auxiliary toughening agent, 8 parts by weight of a curing agent, 8 parts by weight of a vulcanizing agent and 3 parts by weight of a filler, and mix them to obtain a modified benzoxazine resin system.

[0088] 2.2. The modified benzoxazine resin system was stirred at a stirring rate of 3000 r / min at a constant temperature of 100℃ for 3 hours until it was uniformly mixed to obtain a glue solution.

[0089] 2.3. The above adhesive solution is preheated in an oven at 50°C for 30 minutes, and then pressed into a film on a calender at a roll temperature of 80°C to obtain a modified benzoxazine adhesive film.

[0090] 3. Preparation of prepreg layup components:

[0091] 3.1. Bisphenol A type benzoxazine resin is used to prepare glass cloth reinforced bisphenol A type benzoxazine resin prepreg by hot melt method, and glass cloth reinforced bisphenol A type benzoxazine resin prepreg is obtained;

[0092] 3.2. The obtained glass cloth reinforced bisphenol A type benzoxazine resin prepreg is cut according to the cover structure dimensions to obtain prepreg, and then laid up to obtain a prepreg layup of about 10mm;

[0093] 3.3. The obtained prepreg layup is placed in an oven for prepolymerization treatment at 90℃ for 2 hours to obtain a preformed prepreg layup.

[0094] 4. Preparation of a three-layer structure of glass fiber reinforced benzoxazine prepreg / film / silicone rubber:

[0095] 4.1. Adhere the pre-formed silicone rubber sheet from step 1.3 to the metal mold of the cover, and use vacuuming to ensure the rubber sheet adheres tightly;

[0096] 4.2 Cut the modified benzoxazine film obtained in step 2.3 into the required size, lay it on the rubber sheet, and iron it properly with an electric iron to ensure good laying;

[0097] 4.3. The prepreg layup from step 3.3 is bonded to the adhesive film to form a three-layer structure of carbon fiber reinforced benzoxazine prepreg / adhesive film / silicone rubber;

[0098] 4.4. Perform autoclave curing. The curing regime is to keep at 100℃ for 0.5h, pressurize at 140℃ for 4h with a curing pressure of 0.8MPa, then post-treat at 160℃ for 1h, and then cool down to below 40℃ to demold and obtain the blank.

[0099] 4.5. The outer heat protection and inner heat insulation integrated cover blank obtained in the previous step is processed by drilling, trimming and polishing according to the standard outer surface dimensions to obtain a high-precision outer heat protection and inner heat insulation integrated cover component.

[0100] The performance of the cover components prepared in Examples 1 to 3 was tested, and the test results are shown in Table 1.

[0101] Table 1. Test results of structural performance of each layer of the enclosure.

[0102]

[0103] Although the present invention has been disclosed above with reference to embodiments, it is not intended to limit the present invention. Appropriate modifications or equivalent substitutions made by those skilled in the art to the technical solutions of the present invention should be covered within the protection scope of the present invention, which is defined by the claims.

Claims

1. An integrated heat-resistant and heat-insulating cover, characterized in that, It includes an outermost heat-resistant bearing layer, an innermost heat-insulating layer, and an intermediate adhesive film layer. The heat-resistant bearing layer is made of fiber-reinforced benzoxazine resin, the heat-insulating layer is made of phosphazene rubber, silicone rubber, or nitrile rubber with raw rubber sheet as raw material, and the adhesive film layer is made of modified benzoxazine adhesive film. The raw materials used in the modified benzoxazine film, by weight, include 20-40 parts of a bifunctional benzoxazine compound, 20-40 parts of a monofunctional benzoxazine compound, 15-25 parts of an auxiliary toughening agent, 5-10 parts of a curing agent, 5-12 parts of a vulcanizing agent, and 1-4 parts of a filler.

2. The integrated heat-resistant and heat-insulating cover as described in claim 1, characterized in that, The resin matrix of the fiber-reinforced benzoxazine resin is a bifunctional benzoxazine compound, including at least one of a diphenolic benzoxazine and a diamine-type benzoxazine, with the monomer structure as follows: Wherein, X is one of -CH2-, -SO2-, and -O-; R1 and R2 are one of hydrogen and alkyl groups.

3. The integrated heat-resistant and heat-insulating cover as described in claim 1, characterized in that, The fiber-reinforced benzoxazine resin uses glass fiber, quartz fiber, carbon fiber, or aramid fiber.

4. The integrated heat-resistant and heat-insulating cover as described in claim 1, characterized in that, The total thickness of the heat-resistant bearing layer is 5-10 mm, the thickness of the heat insulation layer is 3-5 mm, and the thickness of the adhesive film layer is 0.4-0.8 mm.

5. A method for preparing an integrated heat-resistant and heat-insulating cover as described in claim 1, characterized in that, Includes the following steps: 1) A phosphazene rubber, silicone rubber, or nitrile rubber raw sheet is sandwiched between two gaskets and preformed on a plate vulcanizing machine to obtain a preformed rubber sheet; fiber-reinforced benzoxazine resin is made into fiber-reinforced benzoxazine resin prepreg by hot melt method, laid up, and placed in an oven for prepolymerization treatment to obtain a preformed prepreg layup; the modified benzoxazine resin system is made into a liquid, prepolymerized, and pressed into a film to obtain a modified benzoxazine film; 2) The preformed rubber The rubber sheet is laid on the cover mold and the rubber sheet is tightly attached by vacuuming; the modified benzoxazine film is laid on the rubber sheet; the pre-formed prepreg layer is pasted on the modified benzoxazine film to form a three-layer structure; 3) the three-layer structure is cured in a hot autoclave and then cooled and demolded; 4) the obtained integrated heat protection and internal insulation cover is processed according to the standard external surface dimensions by drilling, trimming and polishing to obtain a high-precision integrated heat protection and internal insulation cover finished product.

6. The preparation method according to claim 5, characterized in that, The preparation steps of the modified benzoxazine film include: a) weighing 20-40 parts by weight of a bifunctional benzoxazine compound, 20-40 parts by weight of a monofunctional benzoxazine compound, 15-25 parts by weight of an auxiliary toughening agent, 5-10 parts by weight of a curing agent, 5-12 parts by weight of a vulcanizing agent, and 1-4 parts by weight of a filler to obtain a modified benzoxazine resin system; b) mixing the modified benzoxazine resin system at a stirring rate of 1000-5000 r / min at a constant temperature of 80-150°C for 1-5 hours until homogeneous to obtain a slurry; c) preheating the slurry in an oven at 40-70°C for 30 minutes, and then pressing it into a film on a calender at a roll temperature of 70-90°C to obtain a modified benzoxazine film.

7. The preparation method according to claim 5, characterized in that, In step 3), the conditions for autoclave curing include holding at 100±3℃ for 0.5h, pressurizing at 140±3℃ for 4h with a curing pressure not less than 0.8MPa, and then post-treatment at 160℃ for 1h.

8. The preparation method according to claim 5, characterized in that, In step 3), the demolding condition is to demold when the temperature drops below 40°C.

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