Flame-retardant HP-RTM epoxy resin and preparation method thereof

Abstract

The invention relates to the technical field of high polymer materials, and particularly discloses flame-retardant HP-RTM epoxy resin and a preparation method thereof. The flame-retardant HP-RTM epoxy resin comprises a resin mixture, a curing agent and a release agent in a weight ratio of 100: (10-25): (2-4), and the resin mixture comprises the following raw materials in percentage by weight based on the total weight of the resin mixture: 45-85% of epoxy resin; 7%-40% of a flame retardant mixture; the flame-retardant mixture is prepared from the following raw materials in parts by weight according to the total weight of the flame-retardant mixture: 10 to 15 parts of ammonium polyphosphate, 8 to 12 parts of melamine cyanurate and 5 to 8 parts of nano magnesium hydroxide. The carbon layer framework, the porous foam structure and the compact ceramic outer layer are sequentially formed by constructing the temperature gradient correspondence, and the flame retardant property of the HP-RTM epoxy resin material can be improved.

Description

Technical Field

[0001] The present invention relates to the technical field of polymer materials, and in particular to a flame-retardant HP-RTM epoxy resin and a preparation method thereof. Background Art

[0002] With the rapid development of the new energy industry and the wide popularization of new energy vehicles, the lightweight and low cost of new energy vehicles have become the focus of people's attention. Fiber-reinforced epoxy resin composites have many advantages such as high specific modulus, high specific strength, low density, low curing shrinkage rate, heat resistance, low temperature resistance, and designable properties, and have become the preferred materials for the lightweight of new energy vehicles.

[0003] HP-RTM (High Pressure Resin Transfer Molding) is the abbreviation of high-pressure resin transfer molding process. It refers to a molding process in which resin is mixed by impact and injected into a vacuum-sealed mold pre-laid with fiber-reinforced materials and pre-embedded parts under high-pressure, and then the composite product is obtained through resin flow filling, impregnation, curing, and demolding. Compared with the RTM molding process, HP-RTM uses high-pressure to mix and inject resin into a vacuum-sealed mold pre-laid with fiber-reinforced materials and preforms, and then the composite product is obtained through resin flow filling, impregnation, curing, and demolding. HP-RTM often uses preforms, and the infiltration and rapid curing of resin are completed through high-pressure injection, the infiltration effect and product performance are significantly improved, and the mixing process of the HP-RTM process is fast, so high-reactivity resins can be used, and complex-structured samples can be produced in a short time, solving the bottlenecks of injection and curing, and becoming one of the resin molding processes widely used in multiple industries currently.

[0004] However, when applied to the battery upper cover, it is necessary to be able to cope with accidents such as battery combustion. Therefore, the HP-RTM epoxy resin material is required to have higher flame retardancy. Summary of the Invention

[0005] In order to improve the flame retardancy of the HP-RTM epoxy resin material, the present application provides a flame-retardant HP-RTM epoxy resin and a preparation method thereof.

[0006] In the first aspect, a flame-retardant HP-RTM epoxy resin provided by the present application adopts the following technical solution:

[0007] A flame-retardant HP-RTM epoxy resin, comprising a resin mixture, a curing agent and a release agent with a weight ratio of 100:(10-25):(2-4). Based on the total weight of the resin mixture, the resin mixture comprises raw materials with the following weight percentages: 45%-85% of epoxy resin; 7%-40% of flame-retardant mixture; 5-20% of diluent. Based on the total weight of the flame-retardant mixture, the flame-retardant mixture comprises raw materials with the following weight parts: 10-15 parts of ammonium polyphosphate, 8-12 parts of melamine cyanurate and 5-8 parts of nano magnesium hydroxide.

[0008] By adopting the above technical solution, ammonium polyphosphate decomposes at 250-300°C to generate polyphosphoric acid, which can catalyze the dehydration crosslinking of epoxy resin to form an expanded carbon layer. The released phosphoric acid reacts with melamine cyanurate to generate a phosphorus-nitrogen complex, improving the graphitization degree of the carbon layer. Melamine cyanurate decomposes at 300-350°C to release inert gases such as NH3 and HCNO, diluting the oxygen concentration, and at the same time generating an expansion pressure to foam the carbon layer. NH3 reacts with the PO· free radicals released by ammonium polyphosphate to block the combustion chain reaction. Nano magnesium hydroxide decomposes endothermically at 340-430°C, releasing H2O to lower the system temperature, and generating a MgO coating to isolate oxygen. The MgO nanoparticles fill the pores of the carbon layer, reducing the thermal conductivity of the carbon layer, and reacting with the decomposition products of ammonium polyphosphate to generate a Mg2P2O7 ceramic phase, improving the high-temperature stability of the carbon layer. The diluent is used to reduce the viscosity and ensure the uniform dispersion of the flame-retardant mixture. The curing agent prolongs the gel time to ensure that the resin fully infiltrates the fibers.

[0009] Therefore, the present application can form the following temperature gradient response: at 250-300°C, ammonium polyphosphate acid-catalyzes the crosslinking of epoxy resin to form a phosphate ester network, initially establishing a carbon layer skeleton. At 300-350°C, the decomposed gas of melamine cyanurate causes the volume of the carbon layer to expand by 5-8 times, forming a porous foam structure. At 340-430°C, the MgO nanoparticles generated by nano magnesium hydroxide accumulate on the surface of the carbon layer, forming a dense ceramicized outer layer, which helps to improve the flame-retardant performance of the HP-RTM epoxy resin material.

[0010] In a specific feasible embodiment, the flame-retardant mixture further comprises the following weight parts of raw materials: 3-5 parts of pentaerythritol.

[0011] By adopting the above technical solution, during the curing process, the hydroxyl groups of pentaerythritol can participate in the epoxy resin curing reaction, adjust the crosslinking density, and increase the glass transition temperature. Ammonium polyphosphate decomposes at high temperature to generate polyphosphoric acid, catalyzing the dehydration crosslinking of pentaerythritol to form a three-dimensional crosslinked dense carbon layer, increasing the char residue rate, and forming a stable graphitized carbon layer at high temperature, effectively isolating oxygen and heat, thereby further improving the flame-retardant performance of the HP-RTM epoxy resin material.

[0012] In a specific feasible embodiment, the flame retardant mixture further comprises the following raw materials in parts by weight: 4-6 parts of phosphorylated starch.

[0013] By adopting the above technical solution, phosphorylated starch decomposes at 200-250 °C, releasing phosphoric acid and polyphosphoric acid, catalyzing the dehydration crosslinking of epoxy resin and pentaerythritol, forming a dense phosphorus-rich carbon layer, increasing the char residue rate, and improving the graphitization degree of the carbon layer. The phosphoric acid released by phosphorylated starch reacts with cyanuric acid decomposed from melamine cyanurate to generate thermally stable cyanuryl phosphate, inhibiting smoldering combustion. After carbonization, phosphorylated starch generates nano-carbon spheres, filling the pores of the expanded carbon layer of ammonium polyphosphate / melamine cyanurate, reducing the thermal conductivity of the carbon layer, and enhancing the high-temperature stability of the carbon layer.

[0014] In a specific feasible embodiment, the flame retardant mixture further comprises the following raw materials in parts by weight: 1-3 parts of sulfonated lignin.

[0015] By adopting the above technical solution, sulfonated lignin contains a large number of aromatic structures and forms a highly graphitized carbon layer upon carbonization at high temperature, increasing the char residue rate. The sulfonic acid groups release sulfuric acid at 200-300 °C, synergistically catalyzing the dehydration of epoxy resin to form carbon with ammonium polyphosphate, and improving the density of the carbon layer.

[0016] In a specific feasible embodiment, the flame retardant mixture further comprises the following raw materials in parts by weight: 1-3 parts of polyamide microspheres.

[0017] By adopting the above technical solution, polyamide microspheres expand upon heating at the initial stage of resin combustion, forming a closed-cell foam structure, reducing the heat transfer efficiency. When the microsphere shell layer decomposes, it releases CO2 and N2, diluting the concentrations of oxygen and combustible gases and inhibiting the combustion chain reaction. The expanded microsphere remnants fill the pores of the expanded carbon layer formed by ammonium polyphosphate / melamine cyanurate, reducing the thermal conductivity of the carbon layer. The amine groups released by the microspheres react with the phosphate groups of phosphorylated starch to form a phosphorus-nitrogen crosslinked network, increasing the char residue rate. The fragments decomposed from the microspheres combine with the cyanuric acid of melamine cyanurate to form a nitrogen-containing carbon layer with higher thermal stability.

[0018] In a specific feasible embodiment, the curing agent comprises phenolic amine with an amine value of 300-350 mgKOH / g.

[0019] By adopting the above technical solutions, the amino group of the phenolic amine reacts with the phosphoric acid generated by the decomposition of ammonium polyphosphate to form a phosphorus-nitrogen cross-linked structure, promoting the graphitization of the carbon layer. The cross-linked network captures nano magnesium hydroxide particles to form an MgO-phosphorus-nitrogen ceramic phase, enhancing the char residue rate. The rigid benzene ring structure of the phenolic amine forms a dense three-dimensional network with the epoxy resin, increasing the glass transition temperature. Moreover, the phenolic amine with the above amine value has moderate reactivity in the temperature range of 80-130 °C, and the gel time is controlled within 8-12 minutes, which is more suitable for the injection-molding-curing time window of the HP-RTM process.

[0020] In a specific feasible embodiment, the curing agent further includes 2-ethyl-4-methylimidazole.

[0021] By adopting the above technical solutions, 2-ethyl-4-methylimidazole promotes the homopolymerization reaction of the epoxy resin, forming a more uniform cross-linked network and increasing the glass transition temperature. 2-ethyl-4-methylimidazole reduces the reaction activation energy by nucleophilic attacking the epoxy group, lowering the curing starting temperature. At 80 °C, it shortens the gel time, and the molding time window is more suitable for high-pressure injection.

[0022] In a specific feasible embodiment, the diluent is phenyl glycidyl ether.

[0023] By adopting the above technical solutions, phenyl glycidyl ether can reduce the overall viscosity of the epoxy resin mixture, making it more suitable for the HP-RTM high-pressure injection process. The benzene ring structure of phenyl glycidyl ether is compatible with the polar surface of the flame retardant, capable of reducing the proportion of agglomerates and ensuring the uniform distribution of the flame retardant. Moreover, the carbonized product of phenyl glycidyl ether synergizes with the polyphosphoric acid of ammonium polyphosphate and the nitrogen of melamine cyanurate to form an expanded carbon layer, further improving the flame retardancy.

[0024] In a second aspect, a preparation method of a flame-retardant HP-RTM epoxy resin provided by the present application adopts the following technical solutions:

[0025] A preparation method of a flame-retardant HP-RTM epoxy resin includes the following steps:

[0026] Heat the epoxy resin to 60-65 °C, add the diluent, and stir evenly to obtain a resin matrix;

[0027] Mix ammonium polyphosphate, melamine cyanurate, and nano magnesium hydroxide evenly to obtain a flame-retardant mixture. Add the flame-retardant mixture to the resin matrix, disperse evenly, and perform vacuum degassing treatment until the bubble volume is <0.3% to obtain a standby resin;

[0028] Preheat the mold to 78 - 85 °C, spray the release agent, lay the carbon fiber preform, close the mold, flush and mix the spare resin and curing agent in a weight ratio of 100:(20 - 25) and inject them into the mold, then carry out flow filling, impregnation, curing and demolding to obtain the flame-retardant HP-RTM epoxy resin.

[0029] By adopting the above technical solution, in this method, the resin viscosity is reduced by adding a diluent, so as to inject at a low viscosity, and by adopting the flame-retardant mixture and the HP-RTM process, flame-retardant synergy and rapid curing are achieved, and an epoxy resin material with both flame retardancy, high mechanical properties and industrial mass production efficiency is obtained.

[0030] In summary, the present application has the following beneficial effects:

[0031] 1. By constructing a temperature gradient response in the present application, a carbon layer skeleton, a porous foam structure and a dense ceramicized outer layer are sequentially formed, which helps to improve the flame-retardant performance of the HP-RTM epoxy resin material.

[0032] 2. In the present application, pentaerythritol, phosphorylated starch and sulfonated lignin are preferably used, which can further improve the flame-retardant performance of the HP-RTM epoxy resin material.

[0033] 3. The method of the present application, by injecting at a low viscosity and adopting the flame-retardant mixture and the HP-RTM process, achieves flame-retardant synergy and rapid curing, and obtains an epoxy resin material with both flame retardancy, high mechanical properties and industrial mass production efficiency. Specific Embodiments

[0034] Except as otherwise specified, the raw materials used in the present application are all purchased from the market. Among them, the release agent is Shin-Etsu KM-9782. The phosphorylated starch is prepared by mixing corn starch and ammonium dihydrogen phosphate in a ratio of 1:0.6 and reacting at 120 °C for 2 hours. The polyamide microspheres are of model TR-1.

[0035] The following further details the present application with reference to examples and comparative examples.

[0036] Examples

[0037] Example 1

[0038] In this example, a flame-retardant mixture is prepared, including the following raw materials: 13 kg of ammonium polyphosphate, 10 kg of melamine cyanurate and 7 kg of nano magnesium hydroxide. Mix the ammonium polyphosphate, melamine cyanurate and nano magnesium hydroxide evenly to obtain the flame-retardant mixture.

[0039] This embodiment provides a flame-retardant HP-RTM epoxy resin, which includes 100 kg of resin mixture, 18 kg of curing agent, and 3 kg of release agent. Among them, the resin mixture includes the following raw materials: 65 kg of bisphenol A epoxy resin, 23 kg of flame-retardant mixture, and 12 kg of phenyl glycidyl ether. The curing agent is a phenolic amine with an amine value of 300-350 mgKOH / g.

[0040] This application also provides a preparation method of a flame-retardant HP-RTM epoxy resin, which includes the following steps:

[0041] Heat the epoxy resin to 63°C, add phenyl glycidyl ether, and stir until uniform to obtain a resin matrix.

[0042] Add the flame-retardant mixture to the resin matrix, stir until evenly dispersed, and perform vacuum degassing treatment until the bubble volume is <0.3% to obtain a standby resin.

[0043] Preheat the mold to 80°C, spray the release agent, lay the carbon fiber preform, close the mold, and flush and mix the standby resin and the curing agent in a weight ratio of 100:22 and inject them into the mold, and perform flow filling, impregnation, curing, and demolding to obtain a flame-retardant HP-RTM epoxy resin.

[0044] Example 2

[0045] The difference between this embodiment and Example 1 is only that the flame-retardant mixture includes the following raw materials: 10 kg of ammonium polyphosphate, 12 kg of melamine cyanurate, and 5 kg of nano magnesium hydroxide.

[0046] Example 3

[0047] The difference between this embodiment and Example 1 is only that the flame-retardant mixture includes the following raw materials: 15 kg of ammonium polyphosphate, 10 kg of melamine cyanurate, and 12 kg of nano magnesium hydroxide.

[0048] Example 4

[0049] The difference between this embodiment and Example 1 is only that the flame-retardant mixture includes the following raw materials: 13 kg of ammonium polyphosphate, 10 kg of melamine cyanurate, 7 kg of nano magnesium hydroxide, and 3 kg of pentaerythritol. Mix ammonium polyphosphate, melamine cyanurate, nano magnesium hydroxide, and pentaerythritol evenly to obtain a flame-retardant mixture.

[0050] Example 5

[0051] The difference between this example and Example 1 is only that the flame retardant mixture comprises the following raw materials: 13 kg of ammonium polyphosphate, 10 kg of melamine cyanurate, 7 kg of nano magnesium hydroxide, and 5 kg of pentaerythritol. The ammonium polyphosphate, melamine cyanurate, nano magnesium hydroxide, and pentaerythritol are mixed evenly to obtain the flame retardant mixture.

[0052] Example 6

[0053] The difference between this example and Example 1 is only that the flame retardant mixture comprises the following raw materials: 13 kg of ammonium polyphosphate, 10 kg of melamine cyanurate, 7 kg of nano magnesium hydroxide, 5 kg of pentaerythritol, and 4 kg of phosphorylated starch. The ammonium polyphosphate, melamine cyanurate, nano magnesium hydroxide, pentaerythritol, and phosphorylated starch are mixed evenly to obtain the flame retardant mixture.

[0054] Example 7

[0055] The difference between this example and Example 1 is only that the flame retardant mixture comprises the following raw materials: 13 kg of ammonium polyphosphate, 10 kg of melamine cyanurate, 7 kg of nano magnesium hydroxide, 5 kg of pentaerythritol, and 6 kg of phosphorylated starch. The ammonium polyphosphate, melamine cyanurate, nano magnesium hydroxide, pentaerythritol, and phosphorylated starch are mixed evenly to obtain the flame retardant mixture.

[0056] Example 8

[0057] The difference between this example and Example 1 is only that the flame retardant mixture comprises the following raw materials: 13 kg of ammonium polyphosphate, 10 kg of melamine cyanurate, 7 kg of nano magnesium hydroxide, 5 kg of pentaerythritol, 6 kg of phosphorylated starch, and 1 kg of sulfonated lignin. The ammonium polyphosphate, melamine cyanurate, nano magnesium hydroxide, pentaerythritol, phosphorylated starch, and sulfonated lignin are mixed evenly to obtain the flame retardant mixture.

[0058] Example 9

[0059] The difference between this example and Example 1 is only that the flame retardant mixture comprises the following raw materials: 13 kg of ammonium polyphosphate, 10 kg of melamine cyanurate, 7 kg of nano magnesium hydroxide, 5 kg of pentaerythritol, 6 kg of phosphorylated starch, and 3 kg of sulfonated lignin. The ammonium polyphosphate, melamine cyanurate, nano magnesium hydroxide, pentaerythritol, phosphorylated starch, and sulfonated lignin are mixed evenly to obtain the flame retardant mixture.

[0060] Example 10

[0061] The difference between this example and Example 1 is only that the flame retardant mixture comprises the following raw materials: 13 kg of ammonium polyphosphate, 10 kg of melamine cyanurate, 7 kg of nano magnesium hydroxide, 5 kg of pentaerythritol, 6 kg of phosphorylated starch, 3 kg of sulfonated lignin, and 1 kg of polyamide microspheres. Mix the ammonium polyphosphate, melamine cyanurate, nano magnesium hydroxide, pentaerythritol, phosphorylated starch, sulfonated lignin, and polyamide microspheres evenly to obtain the flame retardant mixture.

[0062] Example 11

[0063] The difference between this example and Example 1 is only that the flame retardant mixture comprises the following raw materials: 13 kg of ammonium polyphosphate, 10 kg of melamine cyanurate, 7 kg of nano magnesium hydroxide, 5 kg of pentaerythritol, 6 kg of phosphorylated starch, 3 kg of sulfonated lignin, and 3 kg of polyamide microspheres. Mix the ammonium polyphosphate, melamine cyanurate, nano magnesium hydroxide, pentaerythritol, phosphorylated starch, sulfonated lignin, and polyamide microspheres evenly to obtain the flame retardant mixture.

[0064] Example 12

[0065] The difference between this example and Example 1 is only that the curing agent is a phenolic amine with an amine value of 100 - 250 mgKOH / g.

[0066] Example 13

[0067] The difference between this example and Example 1 is only that the curing agent is a phenolic amine with an amine value of 400 - 550 mgKOH / g.

[0068] Example 14

[0069] The difference between this example and Example 1 is only that the curing agent comprises a phenolic amine with an amine value of 300 - 350 mgKOH / g and 2 - ethyl - 4 - methylimidazole in a weight ratio of 1:1. Mix the phenolic amine and 2 - ethyl - 4 - methylimidazole evenly to obtain the curing agent.

[0070] Example 15

[0071] The difference between this example and Example 1 is only that an equal amount of dibutyl phthalate and phenyl glycidyl ether is used.

[0072] Example 16

[0073] The difference between this example and Example 1 is only that an equal amount of epoxidized soybean oil and phenyl glycidyl ether is used.

[0074] Example 17

[0075] The difference between this example and Example 1 is only that the flame-retardant mixture includes the following raw materials: 13 kg of ammonium polyphosphate, 10 kg of melamine cyanurate, 7 kg of nano magnesium hydroxide, 5 kg of pentaerythritol, 6 kg of phosphorylated starch, 3 kg of sulfonated lignin, and 1 kg of polyamide microspheres. Mix the ammonium polyphosphate, melamine cyanurate, nano magnesium hydroxide, pentaerythritol, phosphorylated starch, sulfonated lignin, and polyamide microspheres evenly to obtain the flame-retardant mixture. The curing agent includes phenolic amine with an amine value of 300 - 350 mgKOH / g and 2-ethyl-4-methylimidazole in a weight ratio of 1:1. Mix the phenolic amine and 2-ethyl-4-methylimidazole evenly to obtain the curing agent.

[0076] Example 18

[0077] The difference between this example and Example 1 is only that the preparation method of the flame-retardant HP-RTM epoxy resin includes the following steps:

[0078] Heat the epoxy resin to 60 °C, add phenyl glycidyl ether, and stir until homogeneous to obtain the resin matrix.

[0079] Add the flame-retardant mixture to the resin matrix, stir until evenly dispersed, and perform vacuum degassing treatment until the bubble volume < 0.3% to obtain the standby resin.

[0080] Preheat the mold to 78 °C, spray the release agent, lay the carbon fiber preform, close the mold, mix and inject the standby resin and the curing agent in a weight ratio of 100:20 into the mold, and perform flow filling, impregnation, curing, and demolding to obtain the flame-retardant HP-RTM epoxy resin.

[0081] Example 19

[0082] The difference between this example and Example 1 is only that the preparation method of the flame-retardant HP-RTM epoxy resin includes the following steps:

[0083] Heat the epoxy resin to 65 °C, add phenyl glycidyl ether, and stir until homogeneous to obtain the resin matrix.

[0084] Add the flame-retardant mixture to the resin matrix, stir until evenly dispersed, and perform vacuum degassing treatment until the bubble volume < 0.3% to obtain the standby resin.

[0085] Preheat the mold to 85 °C, spray the release agent, lay the carbon fiber preform, close the mold, mix and inject the standby resin and the curing agent in a weight ratio of 100:25 into the mold, and perform flow filling, impregnation, curing, and demolding to obtain the flame-retardant HP-RTM epoxy resin.

[0086] Comparative Example

[0087] Comparative Example 1

[0088] The difference between this comparative example and Example 1 is only that in the raw materials and preparation method of the flame-retardant HP-RTM epoxy resin, the flame-retardant mixture is replaced with an equal amount of ammonium polyphosphate.

[0089] Comparative Example 2

[0090] The difference between this comparative example and Example 1 is only that in the raw materials and preparation method of the flame-retardant HP-RTM epoxy resin, the flame-retardant mixture is replaced with an equal amount of melamine cyanurate.

[0091] Comparative Example 3

[0092] The difference between this comparative example and Example 1 is only that in the raw materials and preparation method of the flame-retardant HP-RTM epoxy resin, the flame-retardant mixture is replaced with an equal amount of nano-magnesium hydroxide.

[0093] Comparative Example 4

[0094] The difference between this comparative example and Example 1 is only that in the raw materials and preparation method of the flame-retardant HP-RTM epoxy resin, the phenyl glycidyl ether is replaced with an equal amount of bisphenol A epoxy resin.

[0095] Performance detection test

[0096] For Examples 1-19 and Comparative Examples 1-4, the following performance detections were carried out:

[0097] According to ISO527, the tensile strength of the flame-retardant HP-RTM epoxy resin of each example and comparative example was detected.

[0098] According to ISO178, the flexural strength of the flame-retardant HP-RTM epoxy resin of each example and comparative example was detected.

[0099] According to the UL94 standard, the flame-retardant grade of the flame-retardant HP-RTM epoxy resin of each example and comparative example was detected.

[0100] GB / T 19466.2-2004 Plastics - Differential scanning calorimetry (DSC) - Part 2: Determination of glass transition temperature was used to detect the glass transition temperature of the flame-retardant HP-RTM epoxy resin of each example and comparative example.

[0101] The detection results are shown in Table 1.

[0102] Table 1

[0103]

[0104]

[0105] Combined with Example 1 and Comparative Examples 1-4 and Table 1, it can be seen that compared with Example 1, the flame retardant grades of Comparative Examples 1-4 are all lower, the glass transition temperature also becomes lower, and the tensile strength and flexural strength change less. This shows that by using the raw material ratio and preparation method of Example 1, the flame retardant performance of the flame retardant HP-RTM epoxy resin can be improved.

[0106] Combined with Examples 1-11, 18-19 and Table 1, it can be seen that the flame retardant grades of Examples 1-11, 18-19 are all higher than or equal to V0, the glass transition temperatures are all greater than 105 °C, and the tensile strength and flexural strength are both high. This shows that by using the raw material ratio within the range of Examples 1-11, 18-19, HP-RTM epoxy resins with good flame retardant performance can be prepared.

[0107] Combined with Examples 1, 12-17 and Table 1, it can be seen that compared with Example 1, the flame retardant grades of Examples 12, 15, 16 are all V1, and the glass transition temperatures are all less than 105 °C. The phenolic amine amine value of Example 13 is greater than that of Example 1, but the glass transition temperature becomes smaller. The curing agent of Example 14 also includes 2-ethyl-4-methylimidazole, and the flame retardant grade of Example 14 is V0, and the glass transition temperature increases significantly. The flame retardant grade of Example 17 is 5VB, and the glass transition temperature increases significantly. This shows that by using phenolic amine with an amine value of 300-350 mgKOH / g and the raw material ratio of Example 17, it helps to further improve the flame retardant performance of the HP-RTM epoxy resin.

[0108] This specific embodiment is only an explanation of the present application, and it is not a limitation of the present application. Those skilled in the art can make modifications without creative contributions to this embodiment after reading this specification, but as long as they are within the scope of the claims of the present application, they are protected by the patent law.

Claims

1. A flame-retardant HP-RTM epoxy resin, characterized in that, It includes a resin mixture, a curing agent, and a mold release agent with a weight ratio of 100:(10 - 25):(2 - 4). Based on the total weight of the resin mixture, the resin mixture includes raw materials with the following weight percentages: 45% - 85% of epoxy resin; 7% - 40% of a flame retardant mixture; 5 - 20% of a diluent. Based on the total weight of the flame retardant mixture, the flame retardant mixture includes raw materials with the following weight parts: 10 - 15 parts of ammonium polyphosphate, 8 - 12 parts of melamine cyanurate, and 5 - 8 parts of nano magnesium hydroxide.

2. The flame-retardant HP-RTM epoxy resin according to claim 1, wherein The flame retardant mixture further includes raw materials with the following weight parts: 3 - 5 parts of pentaerythritol.

3. The flame-retardant HP-RTM epoxy resin according to claim 2, characterized in that, The flame retardant mixture further includes raw materials with the following weight parts: 4 - 6 parts of phosphorylated starch.

4. The flame-retardant HP-RTM epoxy resin according to claim 3, characterized in that, The flame retardant mixture further includes raw materials with the following weight parts: 1 - 3 parts of sulfonated lignin.

5. The flame-retardant HP-RTM epoxy resin according to claim 4, characterized in that, The flame retardant mixture further includes raw materials with the following weight parts: 1 - 3 parts of polyamide microspheres.

6. The flame-retardant HP-RTM epoxy resin according to claim 1, characterized in that, The curing agent includes phenolic amine with an amine value of 300 - 350 mgKOH / g.

7. The flame-retardant HP-RTM epoxy resin according to claim 6, wherein, The curing agent further includes 2 - ethyl - 4 - methylimidazole.

8. The flame-retardant HP-RTM epoxy resin according to claim 1, wherein The diluent is phenyl glycidyl ether.

9. A method for preparing a flame-retardant HP-RTM epoxy resin according to any one of claims 1-8, characterized in that, It includes the following steps: Heat the epoxy resin to 60 - 65°C, add the diluent, and stir evenly to obtain a resin matrix. Mix ammonium polyphosphate, melamine cyanurate, and nano magnesium hydroxide evenly to obtain a flame retardant mixture. Add the flame retardant mixture to the resin matrix, disperse evenly, and perform vacuum degassing treatment until the bubble volume < 0.3% to obtain a standby resin. Preheat the mold to 78 - 85°C, spray the mold release agent, lay the carbon fiber preform, close the mold, and flush - mix and inject the standby resin and the curing agent into the mold according to a weight ratio of 100:(20 - 25), and perform flow filling, impregnation, curing, and demolding to obtain a flame - retardant HP - RTM epoxy resin.

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