A halogen-free flame-retardant benzoxazine-epoxy / aramid fiber composite material and its preparation method

Abstract

The present invention discloses a halogen-free flame retardant benzoxazine-epoxy / aramid fiber composite material and its preparation method, and belongs to the technical field of polymer composite materials. The composite material is obtained by heat curing by main chain type phosphorus-containing benzoxazine, epoxy resin and aramid fiber according to a mass fraction ratio of 1%~50%:40%~70%:30%~70%; the main chain type phosphorus-containing benzoxazine is formed by phosphorus-containing diamine, bisphenol and paraformaldehyde according to a molar ratio of 1:1:4.1~4.4 through Mannich condensation reaction. The composite material prepared by the present invention is based on main chain type phosphorus-containing benzoxazine modified epoxy resin, and is prepared by heat curing with aramid fiber. When benzoxazine undergoes ring-opening polymerization, it cross-links with aramid fiber and epoxy resin, and can significantly improve the interfacial bonding performance between aramid fiber and epoxy resin, and can effectively improve the mechanical properties of the composite material; simultaneously, due to the presence of phosphorus in benzoxazine, the flame retardant performance of the composite material can be improved, and the application field of aramid fiber composite material is expanded.

Description

Technical Field

[0001] The present invention relates to the technical field of polymer composite materials, and in particular to a halogen-free flame-retardant benzoxazine-epoxy / aramid fiber composite material and a preparation method thereof. Background Art

[0002] Epoxy-aramid fiber composites, thanks to their lightweight, high-strength, high-temperature resistance, and excellent fatigue resistance, have become core structural materials in cutting-edge fields such as aerospace, military equipment, and new energy vehicles. In the aviation field, this material is widely used in solid rocket motor casings, radar fairings, and load-bearing components such as aircraft wings and flaps. In the military field, aramid-aluminum composite armor made from it has a specific modulus that exceeds 10 times that of aluminum alloy, and its ballistic resistance is improved by 40%. In the field of new energy vehicles, battery pack casings made from this material can meet the requirements of electromagnetic shielding and lightweighting. However, traditional epoxy-aramid composites exhibit high heat release rates and high total heat release during combustion, which can easily lead to fire risks. Therefore, improving their flame retardant properties has become a hot research topic.

[0003] Traditional flame retardant methods mainly use halogen flame retardants, such as bromine and chlorine. Although these flame retardants can improve the flame retardancy of materials, they release toxic halogenated gases, dioxins and other toxic substances when burned, causing serious harm to the environment and human health. Therefore, the development of halogen-free flame retardant composite materials is of great practical significance.

[0004] Because benzoxazine contains nitrogen in its structure, the addition of flame-retardant elements (such as phosphorus, boron, silicon, and sulfur) to its molecular structure can achieve a multi-element synergistic flame retardant effect, making it a novel halogen-free flame retardant. Phosphorus-containing benzoxazine, due to its environmentally friendly, highly effective, and low-toxic properties, can be used to modify epoxy-aramid fiber composites, effectively improving their flame retardancy.

[0005] The present invention synthesizes a main-chain phosphorus-containing benzoxazine based on molecular design, then uniformly mixes it with an epoxy resin. This resin system is then pressed into a composite material with aramid fiber. The benzoxazine undergoes ring-opening polymerization, cross-linking with the aramid fiber and epoxy resin, enhancing the interfacial bonding between the aramid fiber and epoxy resin, thereby optimizing the overall performance of the composite material. Furthermore, the introduction of the main-chain phosphorus-containing benzoxazine can meet the urgent demand for high-performance halogen-free flame-retardant composite materials in various fields. Therefore, this material has broad application prospects in aerospace, electronics, defense, sports equipment, automotive, and other fields. Summary of the Invention

[0006] The present invention mainly improves the interfacial bonding strength between aramid fiber and matrix material and simultaneously enhances the flame retardant performance of the composite material, and proposes a halogen-free flame retardant benzoxazine-epoxy / aramid fiber composite material and a preparation method thereof.

[0007] In order to achieve the above object, the present invention adopts the following technical solutions:

[0008] A halogen-free flame-retardant benzoxazine-epoxy / aramid fiber composite material, characterized in that the composite material is obtained by heat-curing a main-chain phosphorus-containing benzoxazine, an epoxy resin, and an aramid fiber, wherein the mass fraction ratio of the main-chain phosphorus-containing benzoxazine, the epoxy resin, and the aramid fiber is 1%-50%: 40%-70%: 30%-70%, and the sum of the three masses is 100%. The main-chain phosphorus-containing benzoxazine is formed by a Mannich condensation reaction of a phosphorus-containing diamine, a dihydric phenol, and paraformaldehyde in a molar ratio of 1:1:4.1-4.4. The general structural formula is as follows:

[0009] ;

[0010] Wherein, the structure of R1 is one or more of the following:

[0011] ;

[0012] Among them, the value range of m is 1-40;

[0013] Wherein, the structure of R2 is one or more of the following:

[0014] .

[0015] Furthermore, the halogen-free flame-retardant benzoxazine-epoxy / aramid fiber composite material is characterized in that the aramid fiber is selected from one or more of meta-aramid, aramid II and aramid III.

[0016] Furthermore, the halogen-free flame-retardant benzoxazine-epoxy / aramid fiber composite material is characterized in that the epoxy resin is selected from one or more of bisphenol A epoxy resin, glycidylamine epoxy resin and alicyclic epoxy resin with a degree of polymerization of 4 to 10; and the heat-curing curing agent is methyltetrahydrophthalic anhydride.

[0017] Furthermore, the method for preparing the halogen-free flame-retardant benzoxazine-epoxy / aramid fiber composite material is characterized by comprising the following steps:

[0018] S1 Preparation of Main-Chain Phosphorus-Containing Benzoxazine: Under inert gas protection, dihydric phenol, phosphorus-containing diamine, and paraformaldehyde were added in a molar ratio of 1:1:4.1-4.4 to a three-necked flask equipped with a stirrer, a thermometer, and a condenser. The mixture was uniformly mixed in a mixed solvent of toluene and ethanol in a volume ratio of 2:1 or in 1,4-dioxane. The mixture was heated to 90-110 °C and reacted for 10-36 h. After the reaction, the main-chain phosphorus-containing benzoxazine was obtained by post-treatment.

[0019] S2 Preparation of benzoxazine-modified epoxy / aramid fiber composites: Main-chain phosphorus-containing benzoxazine and epoxy resin were evenly mixed at room temperature, and then the resin system was evenly impregnated on the aramid fiber, wherein the mass fraction ratio of benzoxazine, epoxy resin and aramid fiber was 1%~50%: 40%~70%: 30%~70%, and the total mass of the three was 100%. Then, it was placed in a mold and heated and cured at 120~240 ℃ and 5~20 MPa for 6~12 h to obtain a composite material.

[0020] Compared with the prior art, the present invention is beneficial in that:

[0021] First, the present invention synthesizes a main-chain phosphorus-containing benzoxazine from the perspective of molecular design, which has the characteristics of PN synergistic flame retardancy. It is modified into an epoxy-aramid fiber composite material. The resulting composite material has excellent halogen-free flame retardant properties, meets the requirements of green chemistry and sustainable development, and provides an innovative solution for safety upgrades in aerospace, electronic packaging, automotive industry, building materials and other fields.

[0022] Secondly, the present invention uses a main-chain phosphorus-containing benzoxazine to modify the epoxy-aramid fiber composite material. During temperature curing, the benzoxazine undergoes a ring-opening reaction and cross-links with the benzene rings in the aramid fiber and the epoxy resin, significantly improving the interfacial bonding strength between the aramid fiber and the epoxy resin, thereby enhancing the overall performance and service life of the composite material.

[0023] Other advantages, objectives and features of the present invention will be reflected in part from the following description and will be understood by those skilled in the art through study and practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 Implementation Case 1 Main Chain Phosphorus-Containing Benzoxazine (BA-SSiO) main )’s FTIR curve;

[0025] Figure 2 Implementation Case 1 Main Chain Phosphorus-Containing Benzoxazine (BA-SSiO) main )of 1 H-NMR graph;

[0026] Figure 3 Implementation Case 1 Main Chain Phosphorus-Containing Benzoxazine (BA-SSiO) main )’s DSC curve;

[0027] Figure 4 . Implementation Case 1 Main Chain Phosphorus-Containing Benzoxazine (BA-SSiO) main ) Stress-strain curve of modified epoxy-aramid fiber composite material;

[0028] Figure 5 Implementation Case 1 Main Chain Phosphorus-Containing Benzoxazine (BA-SSiO) main ) Comparison of tensile strength and tensile modulus of modified epoxy-aramid fiber composites;

[0029] Figure 6 Example 1: Vertical combustion diagram of main-chain phosphorus-containing benzoxazine ((BA-SSiO)main) modified epoxy-aramid fiber composite material;

[0030] Figure 7 Implementation Case 2 Main Chain Phosphorus-Containing Benzoxazine (BA-SD230) main )’s FTIR curve;

[0031] Figure 8 Example 2 Main chain phosphorus-containing benzoxazine (BA-SD230) main )of 1 H-NMR graph;

[0032] Figure 9 Example 2 Main chain phosphorus-containing benzoxazine (BA-SD230) main ) of the DSC curve. DETAILED DESCRIPTION

[0033] The preferred embodiments of the present invention are described below in conjunction with the accompanying drawings. It should be understood that the preferred embodiments described herein are only used to illustrate and explain the present invention and are not used to limit the present invention.

[0034] Implementation Case 1: A halogen-free flame-retardant benzoxazine-epoxy / aramid fiber composite material and a preparation method thereof, comprising the following steps:

[0035] S1. Preparation of phosphorus-containing diamine: Under N2 protection, 6.81 g of pentaerythritol and 42.17 g of phosphorus oxychloride were added to a three-necked flask equipped with a stirrer, a thermometer, a condenser, and a tail gas absorber, and heated to 110 °C for 6 h. After the reaction, a structure containing phosphorus oxychloride at both ends (SPDPC) was obtained by post-treatment. Then, 5.94 g of SPDPC, 9.94 g of 1,3-bis(3-aminopropyl)-1,1,3,3-tetramethyldisiloxane, and 5.5 mL of triethylamine were added to a three-necked flask equipped with a stirrer, a thermometer, and a condenser, and heated to 80 °C for 8 h. After the reaction, a phosphorus-containing diamine (SSiO) was obtained by post-treatment. The reaction equation is as follows:

[0036] ;

[0037] S2. Preparation of main-chain phosphorus-containing benzoxazine: Under N2 protection, 2.28 g of bisphenol A, 7.21 g of phosphorus-containing diamine (SSiO) and 1.32 g of paraformaldehyde were added to a three-necked flask equipped with a stirrer, a thermometer and a condenser, and uniformly mixed in a solvent of toluene and ethanol with a volume ratio of 2:1. The mixture was heated to 110 °C and reacted for 20 h. After the reaction was completed, the main-chain phosphorus-containing benzoxazine (BA-SSiO) was obtained by post-treatment. main ), the reaction equation is as follows:

[0038] ;

[0039] Figure 1 、 Figure 2 、 Figure 3 They are main chain phosphorus-containing benzoxazine (BA-SSiO main ) of FTIR, 1 H-NMR and DSC spectra, by Figure 1 It can be seen that 916 cm -1 The characteristic peak of oxazine ring is 1074 cm -1 and 1224 cm -1 The characteristic peak of COC is 1178 cm -1 is the characteristic peak of CNC, 1313 cm -1 is the characteristic peak of P=O, 1022 cm -1 is the characteristic peak of POC, 1121 cm -1 The characteristic peak of Si-O-Si is 966 cm -1 The characteristic peak of Si-O-Si is 2961 cm -1 and 2899 cm -1 Characteristic peaks of -CH3 and -CH2-; Figure 2It can be seen that 4.61~4.68 ppm is the chemical shift of N-CH2-O in the oxazine ring, and 3.83~3.98 ppm is the chemical shift of Ar-CH2-N in the oxazine ring. 1 The H-NMR spectra can jointly prove that the main chain phosphorus-containing benzoxazine (BA-SSiO main ) were successfully synthesized; Figure 3 for (BA-SSiO) main The DSC curve of the solidification product shows that the curing peak is around 290 °C.

[0040] S3. Preparation of benzoxazine modified epoxy / polyester fiber composites: 30 wt.% of main chain phosphorus-containing benzoxazine (BA-SSiO) main ) was mixed evenly with 70 wt.% of epoxy resin, and then the resin system was uniformly impregnated on aramid II fiber, with the mass ratio of resin to aramid fiber being 60%:40%. The fiber was then placed in a mold and heated and cured in a hot press at 120-260°C and 10 MPa for 10 h to obtain a composite material. At the same time, aramid II fiber was impregnated with epoxy resin, and a blank control group was prepared according to the above process.

[0041] Figure 4 for peace Figure 5 The stress-strain curve and tensile strength and tensile modulus comparison of benzoxazine modified epoxy-aramid fiber composites are shown in the figure. The data in the figure show that the main chain phosphorus-containing benzoxazine (BA-SSiO main ) modified aramid fiber composite material (AFRP-Bz) has a tensile strength increased by 80 MPa and a tensile modulus increased by 869 MPa compared to the unmodified aramid fiber composite material (AFRP); this indicates that the use of main-chain phosphorus-containing benzoxazine-modified epoxy-aramid fiber composite material can effectively improve the mechanical engagement and chemical bonding between aramid fiber and resin matrix, and also significantly improve the interfacial bonding performance between the two. Figure 6 Main chain phosphorus-containing benzoxazine (BA-SSiO main ) vertical combustion diagram of aramid fiber composite material (AFRP-Bz) modified by AFRP. It can be seen from the figure that the first ignition lasts for 10 seconds and the fire is extinguished 4 seconds after leaving the fire source. At the same time, the second ignition lasts for 10 seconds and the fire is extinguished 3 seconds after leaving the fire source without any material dripping, so it is UL94 V-0 flame retardant.

[0042] Implementation Case 2: A halogen-free flame-retardant benzoxazine-epoxy / aramid fiber composite material and a preparation method thereof, comprising the following steps:

[0043] S1. Preparation of phosphorus-containing diamine: The preparation of SPDPC was the same as in Example 1; 5.94 g of SPDPC, 9.2 g of polyetheramine D230, and 5.5 mL of triethylamine were added to a three-necked flask equipped with a stirrer, a thermometer, and a condenser, heated to 80 °C, and reacted for 8 h. After the reaction, phosphorus-containing diamine (SD230) was obtained by post-treatment. The reaction equation is as follows:

[0044] ;

[0045] S2. Preparation of main-chain phosphorus-containing benzoxazine: Under N2 protection, 2.28 g of bisphenol A, 6.83 g of phosphorus-containing diamine (SD230) and 1.32 g of paraformaldehyde were added to a three-necked flask equipped with a stirrer, a thermometer and a condenser, and uniformly mixed in a solvent of toluene and ethanol with a volume ratio of 2:1. The mixture was heated to 110 °C and reacted for 20 h. After the reaction, the main-chain phosphorus-containing benzoxazine (BA-SD230) was obtained by post-treatment. main ), the reaction equation is as follows:

[0046] ;

[0047] Figure 7 、 Figure 8 、 Figure 9 They are main chain phosphorus-containing benzoxazine (BA-SD230) main ) of FTIR, 1 H-NMR and DSC spectra, by Figure 7 It can be seen that 921 cm -1 The characteristic peak of oxazine ring is 1084 cm -1 and 1228 cm -1 The characteristic peak of COC is 1187 cm -1 is the characteristic peak of CNC, 1313 cm -1 is the characteristic peak of P=O, 1022 cm -1 is the characteristic peak of POC, 2971 cm -1 and 2894 cm -1 Characteristic peaks of -CH3 and -CH2-; Figure 8 It can be seen that 4.61~4.63 ppm is the chemical shift of N-CH2-O in the oxazine ring, and 3.86~3.95 ppm is the chemical shift of Ar-CH2-N in the oxazine ring. 1 The H-NMR spectra can jointly prove that the main chain phosphorus-containing benzoxazine (BA-SSiO main ) were successfully synthesized; Figure 9 For (BA-SD230) main The DSC curve of the solidification product shows that the curing peak is around 270 °C.

[0048] S3. Preparation of benzoxazine modified epoxy / polyester fiber composites: 30 wt.% of main chain phosphorus-containing benzoxazine (BA-SD230) main ) was mixed evenly with 70 wt.% of epoxy resin, and then the resin system was evenly impregnated on aramid II fiber, with the mass ratio of resin to aramid fiber being 60%:40%. The fiber was then placed in a mold and heated and cured in a hot press at 120-260°C and 10 MPa for 8 h to obtain a composite material.

[0049] Implementation Case 3: A halogen-free flame-retardant benzoxazine-epoxy / aramid fiber composite material and a preparation method thereof, comprising the following steps:

[0050] S1. Preparation of phosphorus-containing diamine: The preparation of SPDPC was the same as in Example 1. 5.94 g of SPDPC, 6.89 g of decanediamine, and 5.5 mL of triethylamine were added to a three-necked flask equipped with a stirrer, a thermometer, and a condenser. The mixture was heated to 50 °C and reacted for 6 h. After the reaction, phosphorus-containing diamine (SDDA) was obtained by post-treatment. The reaction equation is as follows:

[0051] ;

[0052] S2. Preparation of main-chain phosphorus-containing benzoxazine: Under N2 protection, 2.28 g of bisphenol A, 5.69 g of phosphorus-containing diamine (SDDA) and 1.32 g of paraformaldehyde were added to a three-necked flask equipped with a stirrer, a thermometer and a condenser, and uniformly mixed in a solvent of toluene and ethanol with a volume ratio of 2:1. The mixture was heated to 110 °C and reacted for 20 h. After the reaction, the main-chain phosphorus-containing benzoxazine (BA-ESiO) was obtained by post-treatment. main ), the reaction equation is as follows:

[0053] ;

[0054] S3. Preparation of benzoxazine modified epoxy / polyester fiber composites: 40 wt.% of main chain phosphorus-containing benzoxazine (BA-SDDA) main ) was mixed evenly with 60 wt.% of epoxy resin, and then the resin system was evenly impregnated on aramid II fiber, with the mass ratio of resin to aramid fiber being 60%:40%. The fiber was then placed in a mold and heated and cured in a hot press at 120-240°C and 10 MPa for 12 h to obtain a composite material.

[0055] Implementation Case 4: A halogen-free flame-retardant benzoxazine-epoxy / aramid fiber composite material and a preparation method thereof, comprising the following steps:

[0056] S1. Preparation of phosphorus-containing diamine: The preparation of SPDPC was the same as in Example 1; 5.66 g of SPDPC, 16 g of polyetheramine D400, and 5.5 mL of triethylamine were added to a three-necked flask equipped with a stirrer, a thermometer, and a condenser, and the mixture was heated to 80 °C and reacted for 6 h. After the reaction, the phosphorus-containing diamine (SD400) was obtained by post-treatment.

[0057] S2. Preparation of main-chain phosphorus-containing benzoxazine: Under N2 protection, 2.28 g of bisphenol S, 7.07 g of phosphorus-containing diamine (SD400) and 1.32 g of paraformaldehyde were added to a three-necked flask equipped with a stirrer, a thermometer and a condenser, and uniformly mixed in a solvent of toluene and ethanol with a volume ratio of 2:1. The mixture was heated to 110 °C and reacted for 20 h. After the reaction, the main-chain phosphorus-containing benzoxazine (BS-SD400) was obtained by post-treatment. main ), the reaction equation is as follows:

[0058] ;

[0059] S3. Preparation of benzoxazine modified epoxy / polyester fiber composites: 35 wt.% of main chain phosphorus-containing benzoxazine (BS-SD400) main ) was mixed evenly with 65 wt.% of epoxy resin, and then the resin system was evenly impregnated on aramid II fiber, with the mass ratio of resin to aramid fiber being 55%:45%. The fiber was then placed in a mold and heated and cured in a hot press at 120-260°C and 10 MPa for 10 h to obtain a composite material.

[0060] Implementation Case 5: A halogen-free flame-retardant benzoxazine-epoxy / aramid fiber composite material and a preparation method thereof, comprising the following steps:

[0061] S1. Preparation of phosphorus-containing diamine: Same as Example 1

[0062] S2. Preparation of main-chain phosphorus-containing benzoxazine: Under N2 protection, 2.5 g of bisphenol S, 7.21 g of phosphorus-containing diamine (SSiO) and 1.32 g of paraformaldehyde were added to a three-necked flask equipped with a stirrer, a thermometer and a condenser, and uniformly mixed in a solvent of toluene and ethanol with a volume ratio of 2:1. The mixture was heated to 110 °C and reacted for 20 h. After the reaction, the main-chain phosphorus-containing benzoxazine (BS-SSiO) was obtained by post-treatment. main ), the reaction equation is as follows:

[0063] ;

[0064] S3. Preparation of benzoxazine modified epoxy / polyester fiber composites: 45 wt.% of main chain phosphorus-containing benzoxazine (BS-SSiO)main ) was mixed evenly with 55 wt.% of epoxy resin, and then the resin system was evenly impregnated on aramid II fiber, with the mass ratio of resin to aramid fiber being 55%:45%. The fiber was then placed in a mold and heated and cured in a hot press at 120-260°C and 10 MPa for 12 h to obtain a composite material.

[0065] In summary, the present invention synthesizes main-chain phosphorus-containing benzoxazines with different structures from the perspective of molecular design, and then presses the resin system mixed with epoxy resin and aramid fiber into a composite material. The benzoxazines undergo ring-opening polymerization and cross-link with the aramid fiber and epoxy resin, thereby enhancing the interfacial bonding between the aramid fiber and the epoxy resin, thereby optimizing the overall performance of the composite material. At the same time, the introduction of the main-chain phosphorus-containing benzoxazines can meet the urgent demand for high-performance halogen-free flame-retardant composite materials in various fields, further expanding the application range of aramid fiber-epoxy resin composite materials.

[0066] The above description is merely a preferred embodiment of the present invention and does not constitute any form of limitation to the present invention. Although the present invention has been disclosed as a preferred embodiment as above, it is not intended to limit the present invention. Any technician familiar with the present profession can make some changes or modifications to equivalent embodiments of the present invention using the technical contents disclosed above without departing from the scope of the technical solution of the present invention. However, any simple modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention are still within the scope of the technical solution of the present invention.

Claims

1. A halogen-free flame-retardant benzoxazine-epoxy / aramid fiber composite material, characterized in that: The composite material is obtained by heat-curing a main-chain phosphorus-containing benzoxazine, an epoxy resin, and an aramid fiber, wherein the mass fraction ratio of the main-chain phosphorus-containing benzoxazine, the epoxy resin, and the aramid fiber is 1%-50%: 40%-70%: 30%-70%, and the total mass of the three is 100%. The main-chain phosphorus-containing benzoxazine is prepared by a Mannich condensation reaction of a phosphorus-containing diamine, a dihydric phenol, and paraformaldehyde in a molar ratio of 1:1:4.1-4.4, and the general structural formula is shown below: ； Wherein, the structure of R1 is one or more of the following: ； Among them, the value range of m is 1-40; Wherein, the structure of R2 is one or more of the following: 。 2. The halogen-free flame-retardant benzoxazine-epoxy / aramid fiber composite material according to claim 1, characterized in that: The aramid fiber is selected from one or more of meta-aramid, aramid II and aramid III.

3. The halogen-free flame-retardant benzoxazine-epoxy / aramid fiber composite material according to claim 1, characterized in that: The epoxy resin is selected from one or more of bisphenol A epoxy resin, glycidylamine epoxy resin and alicyclic epoxy resin with a polymerization degree of 4 to 10; the heat-curing curing agent is methyltetrahydrophthalic anhydride.

4. The method for preparing a halogen-free flame-retardant benzoxazine-epoxy / aramid fiber composite material according to any one of claims 1 to 3, characterized in that: The following steps are involved: S1 Preparation of Main-Chain Phosphorus-Containing Benzoxazine: Under inert gas protection, dihydric phenol, phosphorus-containing diamine, and paraformaldehyde were added in a molar ratio of 1:1:4.1-4.4 to a three-necked flask equipped with a stirrer, a thermometer, and a condenser. The mixture was uniformly mixed in a mixed solvent of toluene and ethanol in a volume ratio of 2:1 or in 1,4-dioxane. The mixture was heated to 90-110 °C and reacted for 10-36 h. After the reaction, the main-chain phosphorus-containing benzoxazine was obtained by post-treatment. S2 Preparation of benzoxazine-modified epoxy / aramid fiber composites: Main-chain phosphorus-containing benzoxazine and epoxy resin were evenly mixed at room temperature, and then the resin system was evenly impregnated on the aramid fiber, wherein the mass fraction ratio of benzoxazine, epoxy resin and aramid fiber was 1%~50%: 40%~70%: 30%~70%, and the total mass of the three was 100%. Then, it was placed in a mold and heated and cured at 120~240 ℃ and 5~20 MPa for 6~12 h to obtain a composite material.

Images