Preparation process and application of high-temperature-resistant flame-retardant carbon fiber prepreg

Abstract

The application relates to the technical field of composite material manufacturing, and discloses a preparation process and application of a high-temperature-resistant and flame-retardant carbon fiber prepreg, which is prepared from bisphenol A type benzoxazine resin, bisphenol A type cyanate ester resin, a reactive hydroxyl phosphazene carrier, a metal salt catalyst and linear phenolic resin micro powder. The reactive hydroxyl phosphazene carrier contains active phenolic hydroxyl groups on a molecular chain, and the phenolic resin micro powder is in a solid state dispersion phase at a preparation temperature. The preparation process adopts a solvent-free hot melting method, and is realized through catalyst pre-complexing, low-temperature dispersion of the micro powder and gradient temperature control impregnation. The application utilizes the phase change characteristics of the phenolic micro powder and the complexation of the phosphazene carrier, solves the contradiction between high activity and long storage period of the solvent-free system, and eliminates the plasticizing effect through the participation of the reactive phosphazene in curing and crosslinking. The obtained prepreg has excellent heat resistance, flame retardancy and dielectric performance.

Description

Technical Field

[0001] This invention relates to the field of composite material manufacturing technology, specifically to a preparation process and application of a high-temperature resistant and flame-retardant carbon fiber prepreg. Background Technology

[0002] Carbon fiber reinforced resin matrix composites occupy an important position in the fields of electronic communications, rail transportation, and high-end industrial manufacturing due to their excellent specific strength, corrosion resistance, and designability. In the selection of high-performance resin matrices, blends of benzoxazine resins and cyanate ester resins are ideal matrix materials for manufacturing high-temperature resistant electronic circuit boards and high-performance structural components due to their near-zero curing shrinkage, good dimensional stability, low moisture absorption, and excellent dielectric properties.

[0003] This resin system presents a challenge in balancing process stability and curing activity during the preparation of carbon fiber prepregs. The ring-opening polymerization of benzoxazine and cyanate esters typically requires high activation energy. Industrially, transition metal salt catalysts are often introduced to lower the curing temperature and shorten the molding cycle. If an environmentally friendly and dense solvent-free hot-melt method is used to prepare the prepreg, the resin needs to be melted under heating to wet the fibers. In this case, the highly active metal catalyst is prone to triggering premature resin reactions during the high-temperature mixing or coating stages, leading to a sharp increase in adhesive viscosity, a shortened pot life, and difficulty in meeting the requirements of continuous production and long-term room-temperature storage. While solvent methods can adjust the process viscosity, solvent evaporation easily introduces micropores into the composite material, which not only reduces the interlaminar shear strength but also degrades the dielectric properties of the material under high-frequency environments.

[0004] To meet the stringent flame-retardant standards in the electronics and electrical industries, flame retardants are often added to the resin matrix. Currently, widely used additive phosphorus- or nitrogen-based flame retardants are mostly chemically inert small-molecule compounds. These non-reactive components cannot enter the cross-linked network of the resin and are prone to plasticizing effects at high temperatures, leading to a decrease in the glass transition temperature of the cured product. Simultaneously, the lack of chemical bonding between the inert flame retardant and the polymer matrix results in weak interfacial adhesion, easily inducing microphase separation, thus causing a decrease in the modulus of the composite material and a deterioration in its resistance to humid heat aging. Therefore, developing a benzoxazine and cyanate ester-based carbon fiber prepreg that can adapt to solvent-free hot-melt processes, possesses excellent storage stability, and balances heat resistance and mechanical properties is a current technical challenge that needs to be addressed. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides a preparation process and application of high-temperature flame-retardant carbon fiber prepreg, which solves the problems of existing benzoxazine and cyanate ester resin systems in the preparation of solvent-free hot-melt prepregs, which are difficult to balance low viscosity processability and long room temperature storage period, as well as the reduction of matrix heat resistance and mechanical properties by adding flame retardants.

[0006] To achieve the above objectives, the present invention provides the following technical solution: In a first aspect, the present invention provides a high-temperature resistant and flame-retardant carbon fiber prepreg, employing the following technical solution: A high-temperature resistant and flame-retardant carbon fiber prepreg, comprising a carbon fiber reinforcing material and a resin composition impregnated in the carbon fiber reinforcing material; the resin composition is made from raw materials comprising the following parts by weight: 40-60 parts of bisphenol A type benzoxazine resin; 40-60 parts of bisphenol A type cyanate ester resin; 15-30 parts of reactive hydroxyphosphazene support; 0.5-2.5 parts of metal salt catalyst; 5-15 parts of linear phenolic resin micro powder; wherein, the reactive hydroxyphosphazene support is a modified phosphazene compound with reactive activity, and the linear phenolic resin micro powder is a solid dispersed phase at the preparation temperature of the resin composition.

[0007] By adopting the above technical solution, this invention utilizes the phase change characteristics of linear phenolic resin micropowder and the complexation effect of reactive hydroxyphosphazene carrier to construct a latent catalytic curing system and an intrinsic flame-retardant network. The specific mechanism of action is as follows: During the prepreg preparation and room temperature storage stages, because the softening point of the linear phenolic resin micropowder is higher than the preparation temperature of the resin composition, the micropowder maintains a solid dispersed phase in the liquid benzoxazine and cyanate ester resin matrix, thereby physically isolating the phenolic hydroxyl proton source that could accelerate the ring-opening reaction. Simultaneously, the metal salt catalyst dissolves and complexes within the reactive hydroxyphosphazene support. The nitrogen atoms in the phosphazene structure and the oxygen atoms on the side groups form coordination bonds with the metal ions, inhibiting the catalytic activity of the metal ions. This dual control mechanism ensures that the resin system exhibits extremely low reactivity at low temperatures, endowing the prepreg with storage stability exceeding 30 days at room temperature.

[0008] During the high-temperature curing stage, when the temperature rises above the softening point of the linear phenolic resin micropowder, the micropowder undergoes a phase change and melts. The uniformly dispersed active phenolic hydroxyl groups are released into the resin phase, providing protons required for ring-opening polymerization. Simultaneously, the high temperature causes the coordination bonds between the metal salt catalyst and the reactive hydroxyphosphazene support to break, releasing highly active metal ions. At this point, the proton source and the metal catalyst work synergistically to initiate the ring-opening polymerization of benzoxazine and the trimerization reaction of the cyanate ester, achieving rapid curing.

[0009] The active functional groups on the reactive hydroxyphosphazene carrier molecular chain directly participate in the crosslinking reaction of the resin, chemically bonding the rigid phosphazene ring skeleton into the polymer crosslinking network. This structure not only improves the crosslinking density and glass transition temperature of the resin matrix, but also avoids the decrease in mechanical properties caused by the precipitation or plasticization of traditional small molecule flame retardants, achieving a balance between high temperature resistance, high flame retardancy, and excellent dielectric properties.

[0010] Preferably, the bisphenol A type benzoxazine resin is 6,6 ' -(1-methylethylidene)bis(3-phenyl-3,4-dihydro-2H-1,3-benzoxazine); the bisphenol A cyanate resin is 2,2-bis(4-cyanoacetophenyl)propane; the metal salt catalyst is selected from one or a combination of zinc acetylacetonate and cobalt acetylacetonate.

[0011] By adopting the above technical solution and selecting a specific bisphenol A type skeleton resin, good interfacial wettability and mechanical properties with carbon fibers can be ensured. The acetylacetone metal salt and phosphazene support have suitable complexation constants, which can accurately control the release temperature range of catalytic activity.

[0012] Preferably, the reactive hydroxyphosphazene support is prepared by the following method: using hexachlorocyclotriphosphazene as the backbone and a mixture of phenol and hydroquinone as the substituent precursor, a nucleophilic substitution reaction is carried out under alkaline conditions; wherein the molar ratio of phenol to hydroquinone is controlled between 0.5 and 5.0, and the reaction endpoint is controlled to be the disappearance of the characteristic P-Cl absorption peak in the infrared spectrum; the molecular structure of this reactive hydroxyphosphazene support contains both phenoxy side groups and reactive phenolic hydroxy side groups.

[0013] By adopting the above technical solution, phenol and hydroquinone are mixed and substituted. The polarity and viscosity of the phosphazene support are adjusted by introducing phenoxy side groups, so that it can be completely miscible with benzoxazine and cyanate resin. Hydroquinone introduces terminal active phenolic hydroxyl groups to provide complexation sites for metal catalysts and participate in subsequent curing and crosslinking as reactive sites. Controlling the disappearance of P-Cl bonds is to prevent residual chloride ions from corroding equipment or increasing dielectric loss under high-frequency electric fields.

[0014] Preferably, the linear phenolic resin micro powder has a softening point range of 115°C to 125°C; an average particle size D50 of less than 10 μm; and the micro powder does not chemically react or dissolve with bisphenol A type benzoxazine resin or bisphenol A type cyanate ester resin in a temperature range of 25°C to 80°C, and undergoes phase change melting and participates in the curing reaction at temperatures above 115°C.

[0015] By adopting the above technical solution, limiting the softening point to 115℃ to 125℃ is the key to realizing the solvent-free hot melt process. This temperature range is higher than the preparation temperature of the prepreg, i.e., 70℃ to 80℃, ensuring that the micro powder does not melt or react during processing, maintaining the low viscosity of the system to facilitate fiber impregnation. At the same time, this temperature range is lower than the conventional curing temperature, i.e., 130℃ to 180℃, ensuring that the micro powder can melt and participate in the reaction in time during the initial stage of curing, avoiding stress concentration defects caused by micro powder residue. Controlling the particle size to less than 10μm is conducive to the penetration and uniform distribution of micro powder between fiber bundles, ensuring the homogeneity of the cured product.

[0016] Secondly, the present invention provides a preparation process for a high-temperature resistant and flame-retardant carbon fiber prepreg, employing the following technical solution: A process for preparing a high-temperature resistant and flame-retardant carbon fiber prepreg includes the following steps: S1. Add the metal salt catalyst to the heated reactive hydroxyphosphazene support and stir until the metal salt is completely dissolved to obtain a transparent catalyst complex solution. Cool it down for later use. S2. The bisphenol A type benzoxazine resin and bisphenol A type cyanate ester resin are heated and melted together, and then cooled to the first temperature; S3. At the first temperature, the catalyst complex liquid obtained in S1 is added to the molten resin obtained in S2, and after mixing evenly, linear phenolic resin micro powder is added. The mixture is then subjected to high shear dispersion and vacuum degassing to obtain a resin solution. The first temperature is lower than the softening point of the linear phenolic resin micro powder. S4. Prepare a resin film from the resin solution obtained in S3 using a coating machine; S5. The resin film is transferred to the carbon fiber reinforced material by hot-melt method, and the prepreg is obtained after hot-press impregnation and cooling.

[0017] By adopting the above technical solution, this invention establishes a solvent-free hot-melt preparation process suitable for highly active benzoxazine and cyanate ester systems. The contradiction between process viscosity and reactivity is resolved through stepwise control and gradient temperature control strategies. The specific process mechanism is as follows: Step S1 involves the pre-dissolution and pre-complexation of the catalyst. A reactive hydroxyphosphazene support is used as a solvent to pre-dissolve the solid metal salt catalyst at a suitable temperature. This step avoids the risk of localized overheating or explosive polymerization that might occur when highly active metal salt particles are directly added to the high-temperature molten matrix resin. Simultaneously, the pre-formed complex liquid achieves uniform dispersion of the catalyst at the molecular level, preventing performance fluctuations in the cured product due to uneven catalyst dispersion.

[0018] Gradient temperature control and latent assembly are implemented through steps S2 and S3. First, a high-viscosity or solid matrix resin is melt-mixed at a higher temperature, then cooled to a specific first temperature plateau. At this first temperature plateau, a catalyst complexing liquid and high-softening-point linear phenolic resin micropowder are introduced. Controlling the first temperature below the softening point of the micropowder is crucial to the process. This ensures that the micropowder remains in a solid granular state throughout mixing and dispersion, preventing melting and miscibility, thus avoiding premature release of active hydroxyl groups. This process window ensures that the resin system has suitable flowability for coating while maintaining it in a chemically latent state.

[0019] Steps S4 and S5 achieve solvent-free, high-density impregnation. Since no volatile organic solvents are used throughout the process, microporous defects caused by solvent evaporation are eliminated. In the hot-press impregnation stage, mechanical pressure and appropriate heating are used to fully impregnate the carbon fiber bundles with the resin solution, followed by rapid cooling and setting to fix the microstructure of the resin, ultimately yielding a prepreg with uniform thickness, excellent surface quality, and a long shelf life.

[0020] Preferably, the specific preparation process of the reactive hydroxyphosphazene support is as follows: phenol and hydroquinone are dissolved in tetrahydrofuran solvent, and anhydrous potassium carbonate is added to prepare a mixed phenol salt; the mixed phenol salt is added dropwise to the tetrahydrofuran solution of hexachlorocyclotriphosphazene, and the mixture is refluxed at 50°C to 70°C for 16 to 24 hours; after the reaction is completed, the insoluble salt and solvent are removed, and the mixture is washed with water and dried.

[0021] By employing the above technical solution, the degree of substitution reaction can be precisely controlled using a solution synthesis route. Reflux conditions of 50°C to 70°C ensure the kinetic rate of the substitution reaction, and a reaction time of 16 to 24 hours ensures that the chlorine atoms on hexachlorocyclotriphosphazene are completely replaced by phenoxy and hydroxyphenoxy groups, eliminating the negative impact of residual chlorine on resin curing and final dielectric properties.

[0022] Preferably, in step S1, the heating temperature of the reactive hydroxyphosphazene support is 80°C to 90°C, and the dissolution time of the metal salt catalyst is 30 minutes to 60 minutes; in step S2, the heating and melting temperature is 100°C to 110°C; and the first temperature is controlled at 70°C to 75°C.

[0023] By adopting the above technical solution and setting a dissolution temperature of 80°C to 90°C, it is possible to ensure that the high-viscosity phosphazene carrier has sufficient fluidity to accelerate the dissolution of metal salts, while also preventing the carrier itself from undergoing thermal polymerization. Setting a melting temperature of 100°C to 110°C ensures thorough blending of benzoxazine and cyanate ester resin. Strictly controlling the first temperature at 70°C to 75°C, which is far below the initial softening temperature of 115°C for phenolic micropowder, provides a stable process window for subsequent mixing and degassing operations, preventing the risk of gelation during processing.

[0024] Preferably, in step S3, the high-shear dispersion speed is 1000 rpm to 2000 rpm, the dispersion time is 5 minutes to 15 minutes, the vacuum degassing time is 3 minutes to 10 minutes, and the material temperature is maintained at 70°C to 75°C during the dispersion and degassing process.

[0025] By employing the above technical solution, high shear force is used to break up agglomerated phenolic resin micropowder, suspending it in the matrix as monodisperse particles, thus ensuring a uniform distribution of curing trigger points. Controlling the dispersion time and temperature prevents material temperature runaway due to shear heat. The vacuum degassing step further removes air trapped in the resin solution, which is crucial for preparing composite materials with low porosity and high dielectric properties.

[0026] Preferably, in step S4, the coating temperature is 70°C to 75°C; in step S5, the hot pressing impregnation temperature is 80°C to 85°C, the hot pressing roller pressure is 3 bar to 5 bar, the production speed is 2 m / min to 5 m / min, and the cooling and setting temperature is below 20°C.

[0027] By adopting the above technical solution, the coating temperature is kept consistent with that in step S3, maintaining the stability of the resin viscosity. During the hot-press impregnation stage, the temperature is finely adjusted to 80°C to 85°C, slightly higher than the coating temperature to further reduce the resin viscosity and promote resin penetration and wetting of the carbon fiber bundles, while still significantly lower than the softening point of the micropowder, ensuring that no chemical cross-linking occurs during impregnation. After impregnation, rapid cooling to below 20°C inhibits resin flow and weak reactivity, facilitating the winding and storage of the prepreg.

[0028] Application of a high-temperature resistant and flame-retardant carbon fiber prepreg in the manufacture of aerospace structural components, radar transparent antenna radomes, or high-temperature resistant electronic circuit boards.

[0029] This invention provides a preparation process and application of a high-temperature resistant, flame-retardant carbon fiber prepreg. It offers the following advantages: 1. This invention solves the contradiction between high reactivity and long shelf life in solvent-free hot-melt systems by introducing linear phenolic resin micropowder with a softening point of 115℃-125℃ as a latent curing agent and using reactive hydroxyphosphazene carrier to complex metal salt catalysts. During the prepreg preparation and room temperature storage stages, the phenolic micropowder is in a solid dispersed phase to achieve physical isolation, and the metal catalyst is complexed to inhibit its activity, keeping the resin system chemically inert and significantly extending its pot life. During the high-temperature molding stage, the micropowder undergoes phase change melting to release active hydroxyl groups, the catalyst decomplexes, and synergistically initiates the rapid copolymerization of benzoxazine and cyanate ester, achieving a balance between molding processability and storage stability. 2. This invention employs a reactive phosphazene carrier with active phenolic hydroxyl groups on its molecular chain, allowing it to directly participate in the crosslinking and curing of the resin matrix as a reactive monomer. This overcomes the negative impact of traditional additive flame retardants on the heat resistance and mechanical properties of the matrix. The reactive phosphazene carrier chemically bonds the rigid phosphazene ring skeleton into the polymer network, imparting excellent flame retardant properties to the material while maintaining the high glass transition temperature and modulus of the cured product. It also eliminates interfacial defects caused by the release or precipitation of small molecule flame retardants, thereby improving the overall mechanical properties of the composite material. 3. This invention prepares prepregs through a solvent-free hot-melt impregnation process, eliminating microscopic pore defects caused by solvent evaporation and obtaining a composite material with high density and excellent dielectric properties. Combined with the low dielectric loss characteristics of cyanate resin itself and the low polarizability of phosphazene structure, the cured composite material exhibits excellent dielectric properties while maintaining high density. Attached Figure Description

[0030] Figure 1 This is a flowchart of the preparation method of the present invention; Figure 2 This is a comparison curve of the resin rheological properties of the present invention; Figure 3 The graph shows the DMA storage modulus versus loss factor of the composite laminate of the present invention. Figure 4 This is a viscosity evolution curve of the prepreg of the present invention during room temperature storage. Figure 5 This is a thermogravimetric curve of the cured resin product of the present invention. Detailed Implementation

[0031] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0032] Please see the appendix Figure 1 The present invention will be further described in detail below.

[0033] The main raw materials and reagents used in the following examples and comparative examples have the following sources and specifications. Reagents not specifically mentioned are all commercially available analytical grade or higher grade products.

[0034] Bisphenol A type benzoxazine resin, chemical name 6,6 ' -(1-Methylethylidene)bis(3-phenyl-3,4-dihydro-2H-1,3-benzoxazine), CAS No. 18632-69-0. Bisphenol A type cyanate resin, chemical name 2,2-bis(4-cyanate-phenyl)propane, CAS No. 1156-51-0, cyanate equivalent 139 g / eq.

[0035] Linear phenolic resin micro powder, CAS No. 9003-35-4, softening point range 115℃ to 125℃, average particle size D50 less than 10μm.

[0036] Zinc acetylacetonate, CAS No. 14024-63-6.

[0037] Cobalt acetylacetonate, CAS No. 14024-48-7.

[0038] Hexachlorocyclotriphosphazene, CAS No. 940-71-6. Hexaphenoxycyclotriphosphazene, CAS No. 1184-10-7. Phenol, CAS No. 108-95-2. Hydroquinone, CAS No. 123-31-9.

[0039] Polyacrylonitrile-based carbon fiber, equivalent to T700 grade, tensile strength 4900MPa, tensile modulus 230GPa, 12K tow.

[0040] Preparation Example 1: This preparation example provides a reactive phosphazene support, including the following steps: In a reaction vessel equipped with a mechanical stirrer, a reflux condenser and a constant pressure dropping funnel, add 100 parts by weight of hexachlorocyclotriphosphazene and 850 parts by weight of anhydrous tetrahydrofuran, and stir until the solid is completely dissolved. In another container, 85.2 parts by weight of phenol and 99.7 parts by weight of hydroquinone were dissolved in 600 parts by weight of anhydrous tetrahydrofuran, and 180 parts by weight of anhydrous potassium carbonate were added. The mixture was stirred at high speed for 30 minutes at room temperature to obtain a mixed phenol salt suspension. The temperature inside the reactor was raised to 50°C. The mixed phenolate suspension was slowly added dropwise to the hexachlorocyclotriphosphazene solution over 60-90 minutes using a dropping funnel. After the addition was complete, the temperature was raised to 66°C and kept under reflux for 18 hours, until infrared spectroscopy showed a value of 360 cm⁻¹. -1 The characteristic absorption peak of P-Cl in the vicinity has completely disappeared; After the reaction was completed, the mixture was cooled to room temperature, and the insoluble potassium salt was removed by filtration. The solvent was recovered by rotary evaporation of the filtrate. The resulting viscous substance was washed four times with deionized water at 60°C to remove residual salt and trace amounts of unreacted monomers. Finally, it was dried in a vacuum drying oven at 80°C for 12 hours to obtain a high-viscosity liquid product.

[0041] Preparation Example 2: This preparation example provides a reactive phosphazene support, including the following steps: In a reaction vessel equipped with a mechanical stirrer, a reflux condenser and a constant pressure dropping funnel, add 100 parts by weight of hexachlorocyclotriphosphazene and 850 parts by weight of anhydrous tetrahydrofuran, and stir until the solid is completely dissolved. In another container, 25.6 parts by weight of phenol and 169.5 parts by weight of hydroquinone were dissolved in 700 parts by weight of anhydrous tetrahydrofuran, and 180 parts by weight of anhydrous potassium carbonate were added. The mixture was stirred at high speed for 30 minutes at room temperature to obtain a mixed phenol salt suspension. The temperature inside the reactor was raised to 50°C. The mixed phenol salt suspension was slowly added dropwise to the hexachlorocyclotriphosphazene solution over 60-90 minutes through a dropping funnel. After the addition was complete, the temperature was raised to 66°C and kept under reflux for 24 hours until the reaction was observed to be complete. The subsequent processing steps were the same as in Preparation Example 1. After vacuum drying at 80°C for 12 hours, a semi-solid product (with low fluidity at room temperature, but good fluidity after heating to 60°C) was obtained.

[0042] Preparation Example 3: This preparation example provides a reactive phosphazene support, including the following steps: In a reaction vessel equipped with a mechanical stirrer, a reflux condenser and a constant pressure dropping funnel, add 100 parts by weight of hexachlorocyclotriphosphazene and 850 parts by weight of anhydrous tetrahydrofuran, and stir until the solid is completely dissolved. In another container, 144.8 parts by weight of phenol and 29.9 parts by weight of hydroquinone were dissolved in 600 parts by weight of anhydrous tetrahydrofuran, and 180 parts by weight of anhydrous potassium carbonate were added. The mixture was stirred at high speed for 30 minutes at room temperature to obtain a mixed phenol salt suspension. The temperature inside the reactor was raised to 50°C. The mixed phenol salt suspension was slowly added dropwise to the hexachlorocyclotriphosphazene solution over 60-90 minutes through a dropping funnel. After the addition was complete, the temperature was raised to 66°C and kept under reflux for 16 hours until the reaction was monitored to be complete. The subsequent processing steps were the same as in Preparation Example 1. After vacuum drying at 80°C for 12 hours, a low-viscosity liquid product was obtained.

[0043] Example 1: This example provides a method for preparing a high-temperature resistant and flame-retardant carbon fiber prepreg, including the following steps: (1) 22 parts by weight of the reactive hydroxyphosphazene support obtained in Preparation Example 1 were added to a premixing vessel, heated to 85°C, 1.5 parts by weight of zinc acetylacetonate were added, and stirred for 45 minutes until the metal salt was completely dissolved to form a transparent complex solution. Then the temperature was lowered to 60°C for later use. (2) Add 50 parts by weight of bisphenol A type benzoxazine resin and 50 parts by weight of bisphenol A type cyanate resin to the main reactor, heat to 105°C and stir to melt and mix for 20 minutes, then force cool to 73°C; add the complex liquid prepared in step (1) at this temperature, stir for 10 minutes to make it uniform, add 10 parts by weight of high softening point linear phenolic resin micro powder, turn on the high shear disperser and disperse at 1500 rpm for 8 minutes, then vacuum degas at 73°C for 5 minutes to obtain resin colloid; (3) The resin solution is coated onto release paper at 73°C using a hot melt coating machine to prepare a surface density of 50 g / m². 2 Resin film; (4) Hot melt impregnation is carried out by sandwiching a layer of T700 grade 12K carbon fiber bundle with two layers of adhesive film. The temperature of the impregnation zone is controlled at 83℃, the pressure of the hot press roller is 4 bar, the production speed is 3m / min, and after impregnation, it is quickly cooled by a 15℃ cooling plate and wound up to obtain a unidirectional carbon fiber prepreg with a resin content of 35%.

[0044] Example 2: This example provides a method for preparing a high-temperature resistant and flame-retardant carbon fiber prepreg, including the following steps: (1) Add 15 parts by weight of the highly active hydroxyphosphazene carrier obtained in Preparation Example 2 into a premixing vessel, heat to 90°C, add 2.5 parts by weight of cobalt acetylacetone, stir for 60 minutes until dissolved, and cool for later use. (2) Add 40 parts by weight of bisphenol A type benzoxazine resin and 60 parts by weight of bisphenol A type cyanate resin to the main reactor, heat to 110°C to melt and mix, and cool to 75°C; add the complexing liquid from step (1) and stir evenly, then add 15 parts by weight of high softening point linear phenolic resin micro powder, disperse at 75°C under high shear for 10 minutes and degas to obtain resin colloid; (3) The coating temperature is controlled at 75℃ to prepare a film with an areal density of 50 g / m³. 2 The adhesive film; (4) The temperature of the impregnation zone is controlled at 85℃ (the high-activity carrier can maintain viscosity balance even with a small amount, and 85℃ is still far below the softening point of the trigger), the hot press roller pressure is 5 bar, and the prepreg with a resin content of 33% is obtained after cooling and winding.

[0045] Example 3: This example provides a method for preparing a high-temperature resistant and flame-retardant carbon fiber prepreg, including the following steps: (1) Add 30 parts by weight of the low viscosity hydroxyphosphazene carrier obtained in Preparation Example 3 into a premixing kettle, heat to 80°C, add 0.5 parts by weight of zinc acetylacetone, stir for 30 minutes to dissolve, and cool for later use; (2) Add 60 parts by weight of bisphenol A type benzoxazine resin and 40 parts by weight of bisphenol A type cyanate resin to the main reactor, heat to 100°C to melt and mix, and cool to 70°C; add the complexing liquid from step (1) and stir evenly, then add 5 parts by weight of high softening point linear phenolic resin micro powder, disperse at 70°C under high shear for 5 minutes and degas to obtain resin colloid; (3) The coating temperature is controlled at 70℃ to prepare a film with an areal density of 50 g / m³. 2 The adhesive film; (4) The temperature of the impregnation zone is controlled at 80°C, the pressure of the hot press roller is 3 bar, and the prepreg with a resin content of 37% is obtained after cooling and winding.

[0046] Example 4: This example provides a method for preparing a high-temperature resistant and flame-retardant carbon fiber prepreg, including the following steps: (1) Prepare a complex solution by mixing and dissolving 18 parts by weight of the reactive hydroxyphosphazene support obtained in Preparation Example 1 with 1.0 parts by weight of zinc acetylacetonate at 85°C; (2) 45 parts by weight of bisphenol A type benzoxazine resin and 55 parts by weight of bisphenol A type cyanate resin were melted at 105°C and cooled to 72°C; complexing liquid and 8 parts by weight of high softening point linear phenolic resin micro powder were added, and the mixture was dispersed evenly and degassed at 72°C. (3) Coating temperature: 72℃; (4) The impregnation temperature is 82°C, and the rest of the process is the same as in Example 1.

[0047] Example 5: This example provides a method for preparing a high-temperature resistant and flame-retardant carbon fiber prepreg, including the following steps: (1) 28 parts by weight of the reactive hydroxyphosphazene support obtained in Preparation Example 1 were mixed and dissolved with 2.0 parts by weight of zinc acetylacetonate at 85°C to prepare a complex solution; (2) 55 parts by weight of bisphenol A type benzoxazine resin and 45 parts by weight of bisphenol A type cyanate resin were melted at 105°C and cooled to 74°C; complexing liquid and 12 parts by weight of high softening point linear phenolic resin micro powder were added, and the mixture was dispersed evenly and degassed at 74°C. (3) Coating temperature: 74℃; (4) The impregnation temperature is 84°C, and the rest of the process is the same as in Example 1.

[0048] Comparative Example 1: Compared with Example 1, the difference is that bisphenol A type benzoxazine resin, bisphenol A type cyanate resin, reactive hydroxyphosphazene carrier obtained in Preparation Example 1, zinc acetylacetonate, and high softening point linear phenolic resin micro powder are added to the reactor at one time, heated to 120°C for melting and mixing, and after the solid is completely melted and dispersed, the material is cooled and discharged. The remaining steps and raw material amounts are the same.

[0049] Comparative Example 2: Compared with Example 1, the difference is that an equal mass of commercially available hexaphenoxycyclotriphosphazene (chemically inert, without active hydroxyl groups) was used to replace the reactive hydroxyphosphazene support obtained in Example 1, while the remaining steps and raw material amounts are the same.

[0050] Comparative Example 3: Compared with Example 1, the difference lies in the composition of the raw materials: no high softening point linear phenolic resin micro powder is added, while the remaining steps and raw material amounts are the same.

[0051] Comparative Example 4: Compared with Example 1, the difference is that an equal mass of ordinary linear phenolic resin (softening point range 85℃-95℃) is used instead of high softening point linear phenolic resin micro powder, while the remaining steps and raw material amounts are the same.

[0052] Comparative Example 5: Compared with Example 1, the difference lies in the preparation technique: instead of using a reactive hydroxyphosphazene carrier, acetone is used as a solvent. Bisphenol A type benzoxazine resin, bisphenol A type cyanate resin, zinc acetylacetonate, and high softening point linear phenolic resin micro powder are dissolved / dispersed in acetone to prepare a 65% solid content adhesive solution. A solvent impregnation process is used to prepare the prepreg, which is then dried to remove the solvent. The remaining steps and raw material amounts are the same.

[0053] Test Example 1: This test case aims to verify the process stability (potential life) and feasibility of the heat-triggered curing mechanism of the resin system described in this invention. The test subjects are the resin liquid prepared in Example 1, Comparative Example 1 (high-temperature fully mixed process), Comparative Example 3 (without phenolic micro powder), and Comparative Example 4 (using low softening point phenolic resin).

[0054] Experimental steps: The isothermal viscosity characteristics of the resin solution were tested using a rotational rheometer equipped with a 40mm parallel plate clamp. The freshly prepared resin sample was placed on the lower electrode, the test gap was set to 1mm, and the shear rate was kept constant at 10s. -1 The test temperature was kept constant at 80℃, and the initial viscosity of the resin system and the time required for the viscosity to double to the initial value were recorded.

[0055] The curing reaction characteristics of the resin system were tested using a differential scanning calorimeter. 5 mg to 10 mg of sample was weighed and packaged in an aluminum crucible. Non-isothermal scanning was performed under a nitrogen atmosphere. The heating range was 40 °C to 300 °C and the heating rate was 10 °C / min. The curing onset temperature and curing peak temperature of the curing exothermic curve were recorded.

[0056] The experimental data are shown in Table 1: .

[0057] Experimental conclusion: According to Table 1 and Appendix Figure 2 Data shows that the resin system of Example 1 had an initial viscosity of 2.14 Pa·s at 80°C and a viscosity doubling time of 268 minutes. At temperatures below the softening point of phenolic resin powder, the curing reaction within the system was suppressed because the curing agent was dispersed in the form of solid particles and the metal catalyst formed a complex with the phosphazene support, thus exhibiting the storage stability required for the process.

[0058] Compared to Example 1, Comparative Example 1 showed an initial viscosity of 45.30 Pa·s and lost its fluidity within 5 minutes. Comparative Example 1 was prepared using a melt-mixing process at 120°C, exceeding the softening point of the phenolic resin micropowder and the system's reaction initiation temperature. This caused the phenolic resin to melt and release active hydroxyl groups, disrupting the complexation state of the metal catalyst and leading to prepolymerization of the resin during the preparation stage. This result verifies the necessity of low-temperature dispersion and physical isolation of solid micropowder for controlling the reaction process.

[0059] Comparing Example 1 and Comparative Example 4, both had similar curing initiation temperatures, but Comparative Example 4 showed a viscosity doubling time of only 42 minutes at 80°C. The common phenolic resin used in Comparative Example 4 had a softening point of 85°C to 95°C, close to the test temperature of 80°C. Under prolonged shearing, it underwent localized softening or dissolution, leading to the release of active groups. Example 1 used high-softening-point phenolic resin micropowder, which maintained the solid-phase interface at the impregnation temperature, ensuring latent stability.

[0060] Comparing Example 1 and Comparative Example 3, the curing initiation temperature of Comparative Example 3 was 235.4℃, and the curing peak temperature was 268.1℃, significantly higher than that of Example 1. This indicates that without the addition of phenolic resin, the metal-phosphazene complex alone cannot effectively initiate the copolymerization reaction of benzoxazine and cyanate ester at conventional molding temperatures. Data from Example 1 shows that when the temperature increases, causing a phase change in the phenolic resin micropowder, the released phenolic hydroxyl groups lower the system's curing activation energy, achieving thermally triggered curing.

[0061] In summary, this invention utilizes a metal-phosphazene complex system combined with high softening point phenolic resin micro powder, and leverages phase changes and complexation-dissociation equilibrium at different temperatures to achieve the rheological stability of the resin system at processing temperatures and the reactivity at molding temperatures.

[0062] Test Example 2: This test case aims to evaluate the heat resistance, interfacial bonding strength, and mechanical load-bearing capacity of composite laminates obtained by curing the prepregs prepared in the examples and comparative examples, in order to verify the synergistic effect of the network structure of the resin matrix and the reinforcing fibers.

[0063] Experimental steps: The prepreg to be tested was cut into 300mm×300mm sizes and stacked in 12 layers in a unidirectional layup manner. It was then cured using an autoclave process: a vacuum was applied to -0.098MPa, the temperature was increased to 180℃ at a rate of 2℃ / min, the pressure was increased to 0.6MPa and held at that temperature for 2 hours, followed by a post-curing treatment at 220℃ for 2 hours, and then allowed to cool naturally to below 60℃ before being removed from the autoclave.

[0064] The glass transition temperature was tested using a dynamic thermomechanical analyzer with a sample size of 50 mm × 10 mm × 2 mm. The double cantilever beam mode was used with a frequency of 1 Hz, a heating rate of 5 °C / min, and a scanning range of 50 °C to 300 °C. The initial point of decrease in storage modulus was taken as the glass transition temperature.

[0065] Mechanical properties were tested using a universal testing machine. Bending properties were tested according to ASTM D790 standard. The testing speed was 2 mm / min, the specimen span ratio was 4:1, and the loading speed was 1 mm / min. Five valid data points were collected for each group of samples and the average value was taken.

[0066] A vertical burning test was conducted with a sample thickness of 3.0 mm, and the afterflame time and dripping were recorded.

[0067] The experimental data are shown in Table 2: .

[0068] Experimental conclusion: According to Table 2 and Appendix Figure 3 Data shows that the composite laminate prepared in Example 1 has a glass transition temperature of 248.5℃, a flexural strength of 1654 MPa, an interlaminar shear strength of 115.2 MPa, and a flame retardancy rating of V-0. The data indicate that bisphenol A-type benzoxazine and cyanate ester resin form a crosslinked network under the action of high-softening-point phenolic resin micropowder, and the reactive hydroxyphosphazene carrier participates in the network construction.

[0069] Comparing Example 1 and Comparative Example 2, Comparative Example 2 used chemically inert hexaphenoxycyclotriphosphazene, resulting in a glass transition temperature of 231.4°C and an interlaminar shear strength of 92.3 MPa. Hexaphenoxycyclotriphosphazene lacks active functional groups and acts as a plasticizer in the cured network, increasing free volume and leading to reduced heat resistance. Simultaneously, the inert molecules do not form chemical bonds with the matrix resin, reducing interfacial bonding strength. In Example 1, the reactive carrier participates in crosslinking through phenolic hydroxyl groups, integrating the phosphazene backbone into the resin network and maintaining rigidity and interfacial adhesion.

[0070] Compared with Comparative Example 3, Comparative Example 3 had a glass transition temperature of 196.2°C and lower mechanical properties. Based on the data from Test Example 1, this system lacked the active protons provided by the phenolic resin, the reaction between benzoxazine and cyanate ester was insufficient under standard processes, the crosslinking density was low, and a complete high-temperature polymer backbone was not formed.

[0071] Compared to Example 1, Comparative Example 5, prepared using a solvent method, showed a decrease in flexural strength and interlaminar shear strength of approximately 8.5% and 10%, respectively, compared to Example 1. The solvent evaporation process creates micropores within the laminate, forming stress concentration points and reducing the material's load-bearing capacity. Example 1, using a solvent-free hot-melt method, resulted in dense resin impregnation of the fibers, leading to fewer internal defects.

[0072] By employing a reactive phosphazene carrier in conjunction with a solid phenolic triggering system, the heat resistance and mechanical strength of the material are maintained while ensuring flame retardancy, thus solving the problem of porosity caused by inert flame retardant plasticization and solvent methods.

[0073] Test Example 3: This test case aims to evaluate the performance retention rate of composite laminates under humid and hot conditions and the material's ability to resist crack propagation, in order to verify the effect of the introduction of reactive hydroxyphosphazene carrier on the moisture resistance and toughness of the resin matrix.

[0074] Experimental steps: According to ASTM D570 standard, cut composite material samples with dimensions of 50mm × 50mm × 2mm. Immerse the samples in boiling water at 100℃ for 48 hours, remove them, wipe off the surface moisture, and weigh them immediately. Calculate the percentage increase in weight after moisture absorption.

[0075] After being immersed in boiling water, the sample was placed in an environment of 120°C and the interlaminar shear strength was tested according to the ASTM D2344 standard. The ratio of the wet-heat strength to the normal strength was calculated as the strength retention rate.

[0076] The Type I interlaminar fracture toughness was tested using the double cantilever beam method according to ASTM D5528. A polytetrafluoroethylene (PTFE) film was pre-embedded in the plane of the intermediate layer during ply layup as a pre-crack initiation point. The specimen size was 125 mm × 25 mm, the loading rate was 1 mm / min, the load-displacement curves were recorded, and the Type I interlaminar fracture toughness value was calculated.

[0077] The experimental data are shown in Table 3: .

[0078] Experimental conclusion: According to the data in Table 3, after immersion in boiling water for 48 hours, the moisture absorption rate of the composite material in Example 1 was 0.68%, the retention rate of interlaminar shear strength in the wet-heat state was 88.4%, and the type I interlaminar fracture toughness was 0.42 kJ / m. 2 Data shows that the reactive hydroxyphosphazene support participates in the chemical reaction during the curing process and transforms into network nodes, without significantly increasing the material's hygroscopicity, and the phosphazene ring structure endows the material with good toughness.

[0079] Compared with Comparative Example 2, Comparative Example 2 had a moisture absorption rate of 1.15%, a strength retention rate of 72.3%, and a fracture toughness of 0.28 kJ / m. 2 In Comparative Example 2, the inert phosphazene used did not participate in crosslinking and existed in a free state, forming free volumes in the network and providing channels for moisture penetration. Simultaneously, the inert particles had weak interfacial bonding with the matrix, failing to effectively transfer stress during crack propagation. Example 1 eliminated free volumes through chemical bonding, improving network integrity, inhibiting moisture diffusion, and enhancing crack propagation resistance.

[0080] Compared with Comparative Example 5, Comparative Example 5 had a moisture absorption rate of 0.96%, which was higher than that of Example 1. During the solvent-based preparation process, solvent evaporation leaves micropores that accumulate moisture under high temperature and humidity conditions, damaging the resin-fiber interface and leading to a decrease in the retention rate of damp heat strength. The matrix obtained by the solvent-free process in Example 1 is dense and effectively prevents environmental corrosion.

[0081] Compared to Comparative Example 3, Comparative Example 3 had the worst performance, with a moisture absorption rate of 1.42%. Due to the lack of an active proton source, the cyanate ester resin was not completely cured, and the remaining unreacted cyanate ester groups were prone to hydrolysis with water, leading to chemical degradation of the matrix under humid and hot conditions. Example 1 utilized phenolic resin micropowder to ensure complete curing, forming a stable triazine ring structure and guaranteeing chemical stability.

[0082] This invention combines a reactive carrier structure with a solvent-free process to improve flame retardancy while maintaining resistance to damp heat, and improves the toughness of the resin system through chemical modification.

[0083] Test Example 4: This test case aims to evaluate the volatile content, resin flowability, and shelf life (or storage life) of carbon fiber prepregs prepared with different resin systems, in order to verify the effectiveness of the technical solution's process adaptability and latent mechanism in industrial manufacturing.

[0084] Experimental steps: The volatile content was tested according to ASTM D3530 standard. A 100mm × 100mm prepreg sample was cut, the initial mass was weighed, and the sample was placed in a 163℃ forced-air oven for 15 minutes and heated. After cooling to room temperature, the sample was weighed and the mass loss rate was calculated.

[0085] The resin flowability was tested according to ASTM D3531 standard. Two 100mm × 100mm pieces of prepreg were cut and laid in a cross shape, weighed, and then sandwiched in a hot press plate preheated to 177°C. A pressure of 0.7MPa was applied and held for 15 minutes. After cooling, the excess resin flash was cut off, the remaining mass was weighed, and the percentage of resin loss was calculated.

[0086] Test room temperature storage life. Place the prepreg in an open environment at 25°C and 50% relative humidity. Check the tackiness and sag of the prepreg every 24 hours and record the number of days it takes for the matrix to fracture brittlely when the prepreg surface loses tackiness or bends.

[0087] The experimental data are shown in Table 4: .

[0088] Experimental conclusion: According to Table 4 and Appendix Figure 4 The data shows that the volatile content of the prepreg in Example 1 was 0.32%, the resin fluidity was 24.5%, and the shelf life at 25°C was 38 days. The data indicate that the hot-melt process controlled the volatile content, the resin system maintained fluidity before curing, and had chemical stability at room temperature.

[0089] Comparing Example 1 and Comparative Example 5, Comparative Example 5 (solvent method) had a volatile content of 2.15%. During the solvent method preparation process, some solvent is difficult to completely remove during the drying stage and remains in the resin system. Although the residual solvent initially increased the resin fluidity (29.8%), it vaporizes during high-temperature curing, forming pores and causing a decrease in the density of the composite material. Example 1 used a solvent-free process, eliminating the pore defects caused by solvent evaporation.

[0090] Compared to Comparative Example 1, Comparative Example 1 showed a resin flowability of only 3.2% and a shelf life of less than 3 days. Comparative Example 1 underwent high-temperature mixing at 120°C during preparation, causing premature cross-linking and gelation of the resin system. This restricted the movement of polymer chain segments and resulted in a loss of thermal flowability. Such prepregs cannot expel interlayer gases during molding, easily leading to molding defects. Example 1 employed a low-temperature dispersion process to ensure the resin remained unreacted before molding.

[0091] Comparing Example 1 and Comparative Example 4, Comparative Example 4 had a storage life of 8 days. The ordinary phenolic resin used in Comparative Example 4 had a softening point of 85°C to 95°C. During storage at room temperature, the phenolic hydroxyl groups diffused into the cyanate ester / benzoxazine phase, initiating a slow curing reaction and resulting in loss of viscosity. Example 1 used high-softening-point phenolic resin micropowder, which is solid and glassy at room temperature, forming a two-phase interface with the liquid resin matrix. This blocked the chemical reaction pathway, allowing phase change and reaction to occur only during the high-temperature molding stage, thus achieving control over storage stability and molding reactivity.

[0092] This invention prepares a prepreg with low volatile content, suitable fluidity, and long shelf life by using a solvent-free hot-melt process and phase control of high softening point components.

[0093] Test Example 5: The dielectric response characteristics of the cured resin system under high-frequency conditions and its thermal decomposition behavior under high-temperature conditions were evaluated.

[0094] Experimental steps: To test the dielectric constant and dielectric loss factor, the cured resin board was processed into 10mm×2.5mm×1.2mm samples. A vector network analyzer was used in conjunction with a resonant cavity perturbation method fixture to test at a frequency of 10GHz. The average value of 3 test points was taken for each sample.

[0095] Thermogravimetric analysis was performed by weighing 5 mg to 8 mg of cured resin powder into an alumina crucible and testing it under a nitrogen atmosphere using a thermogravimetric analyzer with a gas flow rate of 50 mL / min, a heating rate of 20 °C / min, and a scanning range from room temperature to 800 °C. The temperature at which the weight loss was 5% and the char residue at 800 °C were recorded.

[0096] The experimental data are shown in Table 5.

[0097] .

[0098] Experimental conclusion: According to Table 5 and Appendix Figure 5Data from Example 1 shows that at a frequency of 10 GHz, the dielectric constant is 2.84, the dielectric loss factor is 0.0042, the 5% weight loss temperature is 412°C, and the char residue at 800°C is 58.4%. These data indicate that after curing, the resin system forms a low-polarity, high-density cross-linked network, and the phosphazene skeleton enhances thermal stability.

[0099] Compared to Example 1, Comparative Example 3 has a dielectric constant of 3.45, a dielectric loss factor of 0.0138, and a 5% weight loss temperature of 332°C. Comparative Example 3 lacks the active protons provided by the phenolic resin, resulting in incomplete reaction between the cyanate ester and benzoxazine, leaving residual hydroxyl and cyanate ester groups. The polar groups undergo dipole orientation polarization under an alternating electric field, increasing the dielectric constant and loss. Unreacted small molecules and oligomers exhibit poor thermal stability, lowering the thermal decomposition temperature. Example 1 utilizes a high softening point phenolic resin to initiate curing, transforming the polar groups into more symmetrical triazine and oxazine ring structures, thus reducing molecular polarizability.

[0100] Comparing Example 1 and Comparative Example 2, Comparative Example 2 had a dielectric loss factor of 0.0075 and a 5% weight loss temperature of 384°C. The inert phosphazene used in Comparative Example 2 did not form chemical bonds with the resin network, and the movement of phosphazene molecular chain segments at high temperatures led to premature thermal decomposition. The interfacial polarization effect between the inert additive and the matrix increased dielectric loss. In Example 1, the reactive support restricted the thermal movement of molecular chain segments through chemical bonding, improving network rigidity and the thermal decomposition threshold; the homogeneous structure reduced interfacial polarization losses.

[0101] Compared to Comparative Example 5, Comparative Example 5 had a dielectric loss factor of 0.0089. The solvent-based preparation method resulted in increased dielectric loss due to residual trace amounts of polar solvent and the micropores formed by solvent evaporation. Gas ionization within the micropores and the dipole polarization of solvent molecules degraded the dielectric properties. The solvent-free process in Example 1 ensured the material's density and purity.

[0102] This invention eliminates residual polar groups and microscopic defects through chemical structure design and process optimization, and achieves low dielectric loss and high thermal stability by utilizing the synergistic effect of phosphazene and resin.

[0103] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A high-temperature resistant and flame-retardant carbon fiber prepreg, characterized in that, The prepreg is made from raw materials comprising the following parts by weight: 40-60 parts of bisphenol A type benzoxazine resin; 40-60 parts of bisphenol A cyanate resin; 15-30 parts of reactive hydroxyphosphazene carrier; 0.5-2.5 parts of metal salt catalyst; 5-15 parts of linear phenolic resin micro powder; The reactive hydroxyphosphazene support is a modified phosphazene compound with reactive activity, and the linear phenolic resin micropowder is a solid dispersed phase at the preparation temperature of the resin composition.

2. The high-temperature resistant and flame-retardant carbon fiber prepreg according to claim 1, characterized in that, The bisphenol A type benzoxazine resin is 6,6 ' -(1-Methylethylidene)bis(3-phenyl-3,4-dihydro-2H-1,3-benzoxazine); The bisphenol A cyanate resin is 2,2-bis(4-cyanoacetylphenyl)propane; The metal salt catalyst is selected from one or a combination of zinc acetylacetonate and cobalt acetylacetonate.

3. The high-temperature resistant and flame-retardant carbon fiber prepreg according to claim 1, characterized in that, The reactive hydroxyphosphazene support was prepared by the following method: Using hexachlorocyclotriphosphazene as the backbone and a mixture of phenol and hydroquinone as substituent precursors, a nucleophilic substitution reaction was carried out under basic conditions. The molar ratio of phenol to hydroquinone is controlled between (0.5-5.0):1, and the reaction endpoint is controlled by the disappearance of the characteristic absorption peak of P-Cl in the infrared spectrum. The molecular structure of the reactive hydroxyphosphazene support contains both phenoxy side groups and reactive phenolic hydroxy side groups.

4. The high-temperature resistant and flame-retardant carbon fiber prepreg according to claim 1, characterized in that, The linear phenolic resin micro powder has the following properties: The softening point ranges from 115℃ to 125℃; The average particle size D50 is less than 10 μm; Furthermore, the linear phenolic resin micro powder does not chemically react or dissolve with the bisphenol A type benzoxazine resin or bisphenol A type cyanate ester resin within a temperature range of 25℃-80℃, but undergoes phase change melting and participates in the curing reaction at temperatures above 115℃.

5. A process for preparing a high-temperature resistant and flame-retardant carbon fiber prepreg, used to prepare the high-temperature resistant and flame-retardant carbon fiber prepreg as described in any one of claims 1-4, characterized in that, Includes the following steps: S1. Add the metal salt catalyst to the heated reactive hydroxyphosphazene support and stir until the metal salt is completely dissolved to obtain a transparent catalyst complex solution. Cool it down for later use. S2. The bisphenol A type benzoxazine resin and bisphenol A type cyanate ester resin are heated and melted together, and then cooled to the first temperature; S3. At the first temperature, the catalyst complex liquid obtained in S1 is added to the molten resin obtained in S2, and after being mixed evenly, linear phenolic resin micro powder is added. The mixture is then subjected to high shear dispersion and vacuum degassing to obtain a resin solution. The first temperature is lower than the softening point of the linear phenolic resin micro powder. S4. Prepare a resin film from the resin solution obtained in S3 using a coating machine; S5. The resin film is transferred to the carbon fiber reinforced material by hot-melt method, and the prepreg is obtained after hot-press impregnation and cooling.

6. The preparation process of a high-temperature resistant and flame-retardant carbon fiber prepreg according to claim 5, characterized in that, The specific preparation process of the reactive hydroxyphosphazene support is as follows: Phenol and hydroquinone were dissolved in tetrahydrofuran solvent, and anhydrous potassium carbonate was added to prepare a mixed phenol salt. The mixed phenol salt was added dropwise to a tetrahydrofuran solution of hexachlorocyclotriphosphazene, and the mixture was refluxed at 50-70°C for 16-24 hours. After the reaction was completed, the insoluble salt and solvent were removed, and the mixture was washed with water and dried.

7. The preparation process of a high-temperature resistant and flame-retardant carbon fiber prepreg according to claim 5, characterized in that, In step S1, the heating temperature of the reactive hydroxyphosphazene support is 80℃-90℃, and the dissolution time of the metal salt catalyst is 30-60 minutes. In step S2, the heating and melting temperature is 100℃-110℃; the first temperature is controlled at 70℃-75℃.

8. The preparation process of a high-temperature resistant and flame-retardant carbon fiber prepreg according to claim 5, characterized in that, In step S3, the high-shear dispersion speed is 1000-2000 rpm, the dispersion time is 5-15 minutes, the vacuum degassing time is 3-10 minutes, and the material temperature is maintained at 70℃-75℃ during the dispersion and degassing process.

9. The preparation process of a high-temperature resistant and flame-retardant carbon fiber prepreg according to claim 5, characterized in that, In step S4, the coating temperature is 70℃-75℃; in step S5, the hot pressing impregnation temperature is 80℃-85℃, the hot pressing roller pressure is 3-5 bar, the production speed is 2-5 m / min, and the cooling and setting temperature is below 20℃.

10. The application of the high-temperature resistant and flame-retardant carbon fiber prepreg according to any one of claims 1-4 in the preparation of aerospace structural parts, radar transparent antenna radomes or high-temperature resistant electronic circuit boards.

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