Preparation method of flame retardant and epoxy resin composite material

Abstract

The invention discloses a preparation method of a flame retardant and an epoxy resin composite material. The preparation method of the flame retardant comprises the following steps: carrying out silane modification on MXene; preparing an MXene dispersion liquid; dissolving a certain amount of a modifier rich in phosphorus-chlorine bonds and an acid-binding agent into tetrahydrofuran, and adding into the MXene dispersion liquid after the modifier and the acid-binding agent are completely dissolved; dissolving a certain amount of phosphonitrilic chloride trimer and organic amine into tetrahydrofuran, and slowly dropwise adding into the mixed solution after dissolving; and after the reaction is finished, filtering to obtain a product, washing the product with tetrahydrofuran and water for multiple times, and drying the product in a vacuum oven to obtain the flame retardant. The flame retardant prepared by the preparation method disclosed by the invention can achieve better flame retardant property with a smaller addition amount, and under the condition of the same addition amount, the peak value of the smoke production rate and the peak value of the CO production rate of the epoxy resin composite material prepared by the preparation method disclosed by the invention are obviously reduced.

Description

Technical Field

[0001] The invention belongs to the technical field of flame retardant composite materials, and particularly relates to a method for preparing a flame retardant and epoxy resin composite material. Background Art

[0002] Epoxy resin (EP) is a typical thermosetting polymer. After curing, EP has good chemical stability, mechanical properties, electrical insulation properties and high adhesion. Due to its excellent comprehensive performance, it is widely used in the fields of electronics, coatings, transportation, civil construction, etc. However, EP, like most polymers, is mainly composed of three elements: C, H, and O. It is very easy to burn and produce a lot of heat and toxic smoke.

[0003] Titanium carbide nanosheets (MXene) are a new type of two-dimensional nanomaterial similar to graphene. They have a unique layered structure and excellent thermal stability, showing good flame retardant potential. However, when MXene is used as a flame retardant polymer, there are problems such as secondary aggregation, decreased flame retardant efficiency, and decreased mechanical properties of composite materials. Therefore, it is of great significance to modify MXene and improve the compatibility of MXene in the polymer matrix, which can further improve the fire safety performance of the polymer without affecting other properties such as mechanical properties. Summary of the invention

[0004] The present invention designs a functionalized MXene flame retardant (H-MX) and uses nanocomposite technology to prepare epoxy resin composite materials, so as to reduce the heat and toxic smoke release during the combustion process of the composite materials.

[0005] A method for preparing a flame retardant comprises the following steps: Step 1, silane modification of MXene; Step 2, dispersing the modified MXene prepared in step 1 in tetrahydrofuran to obtain a MXene dispersion; Step 3, dissolving a certain amount of a modifier rich in phosphorus-chlorine bonds and an acid-binding agent in tetrahydrofuran, and adding the mixture to the MXene dispersion of step 2 after the mixture is completely dissolved; Step 4, dissolving a certain amount of hexachlorocyclotriphosphazene and an organic amine in tetrahydrofuran, and then slowly dropping the dissolved mixture into the mixed solution of step 3; Step 5, after the reaction is completed, the product is filtered and washed with tetrahydrofuran and water for multiple times, and then the product is dried in a vacuum oven to obtain a flame retardant.

[0006] Preferably, the phosphorus-chlorine bond-rich modifier described in step 3 is one or two of hexachlorocyclotriphosphazene, phosphorus oxychloride, phosphorus pentachloride, pyrophosphoryl chloride, diphenyl phosphoryl chloride, phenyl phosphoryl dichloride, and diethylphosphite.

[0007] Preferably, the organic amine compound described in step 4 is one or two of p-phenylenediamine, diphenylthiophenol, melamine, 4,4-diaminodiphenyl ether, 4,4-diaminodiphenyl sulfone, and trimethoxypyrimidine.

[0008] Preferably, the modifier rich in phosphorus-chlorine bonds in step 3 is hexachlorocyclotriphosphazene, the acid binding agent is triethylamine, and the organic amine compound in step 4 is p-phenylenediamine.

[0009] Preferably, the mass ratio of modified MXene to hexachlorocyclotriphosphazene, p-phenylenediamine and triethylamine is 1:(5-7):(5-7):(9.5-13.5).

[0010] A method for preparing a flame retardant, specifically comprising: Step 1, weigh 1 g of MXene and disperse it in a mixed solution of 60 ml of ethanol and 240 ml of water, maintain ultrasonic stirring at low temperature, then add 20 ml of 3-aminopropyltriethoxysilane, and continue to stir; after the reaction is completed, centrifuge and wash with water and ethanol respectively to obtain modified MXene; Step 2, weigh 1 g of the modified MXene prepared in step 1 and disperse it in 50 ml of tetrahydrofuran, maintain low temperature ultrasonic stirring to obtain a MXene dispersion; Step 3, dissolve 4 g of hexachlorocyclotriphosphazene and 11.5 g of triethylamine in 20 ml of tetrahydrofuran, add them to the above MXene dispersion after they are completely dissolved, and continue ultrasonic stirring; Step 4, dissolve 2.0 g of hexachlorocyclotriphosphazene and 6.0 g of p-phenylenediamine in 30 ml of tetrahydrofuran, and slowly add the mixture to the mixed solution of step 3 while continuing to maintain ultrasonic stirring; after the ultrasonic stirring is completed, place the mixed solution in an oil bath and react at 50 °C for 12 h; Step 5: After the reaction is completed, the product is filtered and washed three times with tetrahydrofuran and water respectively, and then the product is dried in a vacuum oven at 50°C to obtain a flame retardant. The surface modifier used to modify MXene can be one of 3-aminopropyltriethoxysilane, tributylaminomethylsilane, 3-aminopropyltrihydroxysilane, (3-aminopropyl)trimethoxysilane, and 3-aminopropylmethyldimethoxysilane.

[0011] A method for preparing an epoxy resin composite material comprises the following steps: Step 1, silane modification of MXene; Step 2, dispersing the modified MXene prepared in step 1 in tetrahydrofuran to obtain a MXene dispersion; Step 3, dissolving a certain amount of a modifier rich in phosphorus-chlorine bonds and an acid-binding agent in tetrahydrofuran, and adding the mixture to the MXene dispersion of step 2 after the mixture is completely dissolved; Step 4, dissolving a certain amount of a modifier rich in phosphorus-chlorine bonds and an organic amine in tetrahydrofuran, and then slowly dropping the dissolved modifier into the mixed solution of step 3; Step 5, after the reaction is completed, the product is filtered to obtain the product, washed with tetrahydrofuran and water for multiple times, and then dried in a vacuum oven to obtain a flame retardant; Step 6, taking a certain amount of flame retardant and acetone and adding them into a flask and mixing; Step 7, heating the epoxy resin until it melts, weighing a certain amount of the melted epoxy resin and adding it to the flask in step 6, placing the flask in an oil bath, and stirring to evaporate the acetone; Step 8, take a certain amount of curing agent, put it into a beaker and heat it until it melts, then add it to the flask in step 7 and mix it evenly, then pour it into a mold, put it into an oven for drying, and obtain a composite material.

[0012] The curing agent may be selected from the group consisting of 4,4-diaminodiphenylmethane, phthalic anhydride, trimellitic anhydride, pyromellitic dianhydride, and methyltetrahydrophthalic anhydride.

[0013] Preferably, the added amount of the flame retardant is 2-4 wt % of the total mass of the epoxy resin composite material.

[0014] A method for preparing an epoxy resin composite material comprises the following steps: Step 1, weigh 1 g of MXene and disperse it in a mixed solution of 60 ml of ethanol and 240 ml of water, maintain ultrasonic stirring at low temperature, then add 20 ml of 3-aminopropyltriethoxysilane, and continue to stir; after the reaction is completed, centrifuge and wash with water and ethanol respectively to obtain modified MXene; Step 2, weigh 1 g of the modified MXene prepared in step 1 and disperse it in 50 ml of tetrahydrofuran, maintain low temperature ultrasonic stirring to obtain a MXene dispersion; Step 3, dissolve 4 g of hexachlorocyclotriphosphazene and 11.5 g of triethylamine in 20 ml of tetrahydrofuran, add them to the above MXene dispersion after they are completely dissolved, and continue ultrasonic stirring; Step 4, dissolve 2.0 g of hexachlorocyclotriphosphazene and 6.0 g of p-phenylenediamine in 30 ml of tetrahydrofuran, and slowly add the mixture to the mixed solution of step 3 while continuing to maintain ultrasonic stirring; after the ultrasonic stirring is completed, place the mixed solution in an oil bath and react at 50 °C for 12 h; Step 5, after the reaction is completed, the product is filtered to obtain the product, washed with tetrahydrofuran and water for three times respectively, and then dried in a vacuum oven at 50° C. to obtain a flame retardant; Step 6, add 2 g of the flame retardant prepared in step 5 and a certain amount of acetone into a flask and keep ultrasonic stirring; Step 7, put the epoxy resin into an oven, heat it at 80°C until it melts, weigh 80.4 g of the melted epoxy resin and add it to the flask in step 6, continue ultrasonic stirring, and after the ultrasonication ends, place the flask in an oil bath at 90°C to stir and volatilize the acetone; Step 8, take 17.6 g of 4,4-diaminodiphenylmethane, grind it into fine powder and put it into a beaker, heat it at 120°C until it melts, and add it to the flask in step 7; after mixing evenly, pour it into a mold, put it into an oven and dry it at 100°C and 150°C respectively to obtain a composite material, wherein the amount of flame retardant added is 2wt% of the total mass of the epoxy resin composite material.

[0015] The beneficial effects of the present invention are:

[0016] The flame retardant prepared by the present invention can achieve better flame retardant performance with less addition amount. Under the same addition amount conditions, the peak smoke generation rate and CO generation rate of the epoxy resin composite material prepared by the present invention are significantly reduced. The flame retardant composite material prepared by the present invention not only has more excellent fire safety performance, but also has more excellent mechanical properties. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 These are the mechanical property test results of pure EP and the epoxy resin composite material prepared by the present invention. DETAILED DESCRIPTION

[0018] In order to further illustrate the technical solution of the present invention, the preferred embodiments of the present invention are described below in conjunction with examples, but it should be understood that these descriptions are only for further illustrating the features and advantages of the present invention, rather than limiting the claims of the present invention. Based on the examples in the present invention, all other embodiments obtained by ordinary technicians in the field without creative work are within the scope of protection of the present invention.

[0019] The raw materials or reagents mentioned below that are not described in detail are all commercially available products, and the process steps or methods that are not described in detail are all process steps or methods known to those skilled in the art.

[0020] The sources of some raw materials and reagents involved in the following examples, test examples and comparative examples are as follows: MXene, purchased from Jilin Yiyi Technology Co., Ltd.; 3-Aminopropyltriethoxysilane was purchased from Shanghai MacLean Biochemical Technology Co., Ltd.; Hexachlorocyclotriphosphazene was purchased from Shanghai MacLean Biochemical Technology Co., Ltd.; Triethylamine was purchased from Sinopharm Chemical Reagent Co., Ltd.; p-phenylenediamine was purchased from Shanghai MacLean Biochemical Technology Co., Ltd.; Tetrahydrofuran was purchased from Shanghai MacLean Biochemical Technology Co., Ltd.; Epoxy resin was purchased from Shandong Tianmao New Materials Technology Co., Ltd.; 4,4-Diaminodiphenylmethane (DDM) was purchased from Shanghai MacLean Biochemical Technology Co., Ltd.; Acetone was purchased from Sinopharm Chemical Reagent Co., Ltd.

[0021] Example 1

[0022] This embodiment 1 is the specific preparation process of the flame retardant of the present invention: Step 1: Weigh 1 g of MXene and disperse it in a mixed solution of 60 ml ethanol and 240 ml water. After ultrasonic stirring for 1 hour at low temperature, add 20 ml of 3-aminopropyltriethoxysilane and continue stirring for 24 hours. After the reaction is completed, centrifuge and wash with water and ethanol to obtain modified MXene.

[0023] Step 2: Weigh 1 g of the modified MXene prepared in step 1 and disperse it in 50 ml of tetrahydrofuran, and stir it at low temperature and ultrasonically for 20 min to obtain a MXene dispersion.

[0024] Step 3: Dissolve 4 g of hexachlorocyclotriphosphazene and 11.5 g of triethylamine in 20 ml of tetrahydrofuran, add them to the above MXene dispersion after they are completely dissolved, and continue ultrasonic stirring for 20 min.

[0025] Step 4: Dissolve 2.0 g of hexachlorocyclotriphosphazene and 6.0 g of p-phenylenediamine in 30 ml of tetrahydrofuran, and slowly add them to the mixed solution in step 3, and continue to stir ultrasonically for 1 h. After the ultrasonic stirring is completed, place the mixed solution in an oil bath and react at 50 °C for 12 h.

[0026] Hexachlorocyclotriphosphazene is grafted to the modified MXene by substitution reaction, and triethylamine is used as an acid-binding agent. p-phenylenediamine is added to react with the grafted hexachlorocyclotriphosphazene, and hexachlorocyclotriphosphazene is added again to completely react with p-phenylenediamine to form a macromolecular structure.

[0027] Step 5, after the reaction is completed, the product is filtered and washed three times with tetrahydrofuran and water respectively, and then the product is dried in a vacuum oven at 50° C. to obtain the flame retardant H-MX-1.

[0028] Among them, the mass ratio of modified MXene and hexachlorocyclotriphosphazene, p-phenylenediamine, and triethylamine is 1 g:6 g:6 g:11.5 g.

[0029] Example 2

[0030] The only difference between Example 2 and Example 1 is that the mass ratio of modified MXene and hexachlorocyclotriphosphazene, p-phenylenediamine, and triethylamine is 1 g:5 g:5 g:9.5 g, that is, 3.4 g of hexachlorocyclotriphosphazene and 9.5 g of triethylamine are added in step 3, and 1.6 g of hexachlorocyclotriphosphazene and 5.0 g of p-phenylenediamine are added in step 4, and the prepared flame retardant is H-MX-2.

[0031] Example 3

[0032] The only difference between Example 3 and Example 1 is that the mass ratio of modified MXene and hexachlorocyclotriphosphazene, p-phenylenediamine, and triethylamine is 1 g:7 g:7 g:13.5 g, that is, 4.7 g of hexachlorocyclotriphosphazene and 13.5 g of triethylamine are added in step 3, and 2.3 g of hexachlorocyclotriphosphazene and 7.0 g of p-phenylenediamine are added in step 4, and the prepared flame retardant is H-MX-3.

[0033] Comparative Example 1

[0034] The only difference between Comparative Example 1 and Example 1 is that the mass ratio of modified MXene and hexachlorocyclotriphosphazene, p-phenylenediamine, and triethylamine is 1 g:3 g:3 g:5.8 g, that is, 2.0 g of hexachlorocyclotriphosphazene and 5.8 g of triethylamine are added in step 3, and 1.0 g of hexachlorocyclotriphosphazene and 3.0 g of p-phenylenediamine are added in step 4, and the prepared flame retardant is H-MX-4.

[0035] Comparative Example 2

[0036] The only difference between Comparative Example 2 and Example 1 is that the mass ratio of modified MXene and hexachlorocyclotriphosphazene, p-phenylenediamine, and triethylamine is 1 g:8 g:8 g:15.4 g, that is, 5.4 g of hexachlorocyclotriphosphazene and 15.4 g of triethylamine are added in step 3, and 2.6 g of hexachlorocyclotriphosphazene and 8.0 g of p-phenylenediamine are added in step 4, and the prepared flame retardant is H-MX-5.

[0037] The addition amount of each component of the flame retardant in the above examples and comparative examples is shown in Table 1: Table 1 Addition amount of each component of the flame retardant in the above examples and comparative examples

[0038] Example 4 This embodiment 4 is a method for preparing the epoxy resin composite material of the present invention. For the convenience of description, the epoxy resin is replaced by EP. The specific process is as follows: Step 1: 2 g of H-MX-1 prepared in Example 1 and a certain amount of acetone were added into a flask and ultrasonic stirring was maintained for 1 hour.

[0039] Step 2: Place EP in an oven and heat it at 80°C until it melts. Weigh 80.4 g of the melted EP and add it to the flask in step 1. Continue ultrasonic stirring for 1 h. After the ultrasonication, place the flask in an oil bath and stir at 90°C to evaporate the acetone for 3 h.

[0040] Step 3, grind 17.6 g of 4,4-diaminodiphenylmethane (DDM) into fine powder and put it into a beaker, heat it at 120°C until it melts, and then add it to the flask in step 2. After mixing evenly, pour it into a mold, put it into an oven and dry it at 100°C and 150°C for 2 h, that is, dry it at 100°C for 2 h, then heat it to 150°C and dry it for another 2 h to obtain the composite material EP / 2.0 H-MX-1, and the addition amount of H-MX-1 flame retardant is 2 wt% of the total mass of the epoxy resin composite material.

[0041] Example 5

[0042] The only difference between Example 5 and Example 4 is that H-MX-2 prepared in Example 2 is used instead of H-MX-1 prepared in Example 1 to obtain an EP composite material.

[0043] Example 6

[0044] The only difference between Example 6 and Example 4 is that H-MX-3 prepared in Example 3 is used instead of H-MX-1 prepared in Example 1 to obtain an EP composite material.

[0045] Comparative Example 3

[0046] The difference between Comparative Example 3 and Example 4 is that H-MX-4 prepared in Comparative Example 1 is used instead of H-MX-1 prepared in Example 1 to obtain an EP composite material.

[0047] Comparative Example 4

[0048] The difference between Comparative Example 4 and Example 4 is that H-MX-5 prepared in Comparative Example 2 is used instead of H-MX-1 prepared in Example 1 to obtain an EP composite material.

[0049] Example 7

[0050] The difference between Example 7 and Example 4 is that the amount of H-MX-1 flame retardant prepared in Example 1 added is 3 wt% of the total mass of the epoxy resin composite material.

[0051] Example 8

[0052] The difference between Example 8 and Example 4 is that the amount of H-MX-1 flame retardant prepared in Example 1 added is 4 wt% of the total mass of the epoxy resin composite material.

[0053] Comparative Example 5

[0054] The difference between Comparative Example 5 and Example 4 is that the amount of H-MX-1 flame retardant prepared in Example 1 added is 1 wt% of the total mass of the epoxy resin composite material.

[0055] Comparative Example 6

[0056] The difference between Comparative Example 6 and Example 4 is that the amount of H-MX-1 flame retardant prepared in Example 1 added is 6 wt% of the total mass of the EP composite material.

[0057] Comparative Example 7

[0058] Comparative Example 7 is a method for preparing pure EP without flame retardant addition, and the specific process is as follows: put EP into an oven, heat it at 80°C until it melts, take 82.1 g of EP and add it to a flask, and stir it at 90°C. Take 17.9 g of DDM and grind it into fine powder and put it into a beaker, heat it at 120°C until it melts, and then add it to the flask. After mixing evenly, pour it into a mold, put it into an oven and dry it at 100°C and 150°C for 2 hours, respectively, to obtain EP without flame retardant.

[0059] Test Example 1: Limiting Oxygen Index Test

[0060] The specific test process is as follows: an oxygen index meter is used to test samples, and the specific samples are Examples 4 to 8 and Comparative Examples 3 to 7.

[0061] The limiting oxygen index refers to the volume fraction concentration of oxygen that a polymer can sustain combustion in a mixture of oxygen and nitrogen. It is an index that characterizes the combustion behavior of a material. Materials with a large limiting oxygen index are difficult to burn. It is generally believed that materials with a limiting oxygen index of more than 27% are difficult to burn, and materials with a limiting oxygen index of less than 20% are easy to burn. The test results are shown in Table 2 below: Table 2 Limiting oxygen index test results

[0062] As can be seen from Table 2, the LOI of pure EP is only 22.15%, indicating that EP is flammable. After adding 2 wt% of H-MX-1, the LOI value of the composite material prepared in Example 4 rises to 27.20%, indicating that it has excellent flame retardant properties. The composite materials prepared in Examples 5 and 6 also exhibit excellent flame retardant properties. In contrast, the composite materials prepared in Comparative Examples 3 and 4 have poor flame retardant properties. For Comparative Example 1, the amount of hexachlorocyclotriphosphazene, triethylamine and p-phenylenediamine added is too small, resulting in too few macromolecules grafted on the surface of the modified MXene, which cannot improve the agglomeration of MXene, resulting in uneven distribution of the flame retardant in the EP matrix and poor flame retardant effect. For Comparative Example 2, the amount of hexachlorocyclotriphosphazene, triethylamine and p-phenylenediamine added is too large, resulting in too many macromolecules grafted on the surface of the modified MXene. However, too many macromolecules will promote the decomposition of the EP matrix, aggravate combustion, and make the composite material exhibit poor flame retardant effect. Therefore, in comparison, the flame retardants H-MX-1, H-MX-2 and H-MX-3 prepared in Example 1, Example 2 and Example 3 have better flame retardant effects.

[0063] For different amounts of flame retardant added, the composite material also shows different effects. In Comparative Example 5, due to too little H-MX-1 added, its limiting oxygen index is less than 27.0%. In Comparative Example 6, due to too much H-MX-1 added, it may not be evenly dispersed in the EP matrix, resulting in an oxygen index less than 27.0%, and a poor flame retardant effect. In contrast, after adding 2 wt%, 3 wt% and 4 wt% H-MX-1, the corresponding composite materials prepared in Examples 4, 7 and 8 have LOI values ​​greater than 27.0%, showing a good flame retardant effect.

[0064] Test Example 2: Cone Calorimetry Test

[0065] The specific test process is as follows: According to ISO 5660 standard, a cone calorimeter (UK, Fire Testing Technology) was used to conduct a combustion test on the sample, and the sample size was 100×100×3 mm 3 , the specific samples are Example 4, Example 7, Example 8 and Comparative Example 7. The test results are shown in Table 3 below: Table 3 Cone calorimetry test results

[0066] PHHR refers to the peak heat release rate, PSPR refers to the peak smoke generation rate, and PCOP refers to the peak CO generation rate.

[0067] As can be seen from Table 3, after EP is ignited, it quickly releases a large amount of heat, reaches the peak heat release rate in a short time, and is accompanied by the release of a large amount of smoke. With the addition of 2 wt% H-MX-1, the release of heat, smoke and CO of the composite material has been significantly reduced. Compared with pure EP, the peak release rates of heat, smoke and CO of EP / 2.0 H-MX-1 decreased by 22.4%, 69.4% and 63.3%, respectively. When 4 wt% H-MX-1 was added, the peak release rates of heat, smoke and CO of EP / 4.0 H-MX-1 decreased by 31.6%, 62.9% and 57.1%, respectively. The above results all show that the fire safety performance of EP composites is significantly improved after adding H-MX-1.

[0068] After adding 6 wt% CLMXene to the prior art 1 (patent number ZL202111188005.8, the invention name is a ternary nano-composite flame retardant, flame-retardant epoxy resin and its preparation method), the peak smoke generation rate of the composite material decreased by 41.3%, while after adding 2 wt% H-MX in the present invention, the peak smoke generation rate of the composite material decreased by 69.4%, which is significantly better than the prior art 1. After adding 2 wt% MX-Fe@LDH to the prior art 2 (patent number ZL202210697803.1, the fam name is the preparation of a functionalized titanium carbide nano-flame retardant and its application in epoxy resin), the peak CO generation rate of the composite material decreased by 40.6%, while after adding 2 wt% H-MX in the present invention, the peak CO generation rate of the composite material decreased by 63.3%, which is significantly better than the prior art 2.

[0069] Test Example 3: Mechanical bending performance test

[0070] The specific testing process is as follows: a universal tensile tester (CMT4204, China MTS Systems Co., Ltd.) is used to test the mechanical properties. The samples are long strips and the experiment is carried out at a bending rate of 2 mm / min according to the standard. The specific samples are Example 4, Example 7, Example 8 and Comparative Example 7.

[0071] from Figure 1 It can be seen that the addition of H-MX-1 can enhance the flexural properties of the composite material. Compared with pure EP, the flexural strength and flexural modulus of EP / 4.0 H-MX-1 increased by 20.9% and 29.0%, respectively.

Claims

1. A method for preparing a flame retardant, characterized in that: The steps include: Step 1, silane modification of MXene; Step 2, dispersing the modified MXene prepared in step 1 in tetrahydrofuran to obtain a MXene dispersion; Step 3, dissolving a certain amount of a modifier rich in phosphorus-chlorine bonds and an acid-binding agent in tetrahydrofuran, and adding the mixture to the MXene dispersion of step 2 after the mixture is completely dissolved; Step 4, dissolving a certain amount of hexachlorocyclotriphosphazene and an organic amine in tetrahydrofuran, and then slowly dropping the dissolved mixture into the mixed solution of step 3; Step 5, after the reaction is completed, the product is filtered and washed with tetrahydrofuran and water for multiple times, and then the product is dried in a vacuum oven to obtain a flame retardant.

2. The method for preparing a flame retardant according to claim 1, characterized in that: The modifier rich in phosphorus-chlorine bonds described in step 3 is one or two of hexachlorocyclotriphosphazene, phosphorus oxychloride, phosphorus pentachloride, pyrophosphoryl chloride, diphenyl phosphoryl chloride, phenyl phosphoryl dichloride, and diethylphosphite.

3. The method for preparing a flame retardant according to claim 2, characterized in that: The organic amine compound described in step 4 is one or two of p-phenylenediamine, diphenylthiophenol, melamine, 4,4-diaminodiphenyl ether, 4,4-diaminodiphenyl sulfone, and trimethoxypyrimidine.

4. The method for preparing a flame retardant according to claim 3, characterized in that: The modifier rich in phosphorus-chlorine bonds described in step 3 is hexachlorocyclotriphosphazene, the acid binding agent is triethylamine, and the organic amine compound described in step 4 is p-phenylenediamine.

5. The method for preparing a flame retardant according to claim 4, characterized in that: The mass ratio of modified MXene to hexachlorocyclotriphosphazene, p-phenylenediamine, and triethylamine is 1:(5~7):(5~7):(9.5~13.5).

6. A method for preparing a flame retardant, characterized in that: Specifically include: Step 1, weigh 1 g of MXene and disperse it in a mixed solution of 60 ml of ethanol and 240 ml of water, maintain ultrasonic stirring at low temperature, then add 20 ml of 3-aminopropyltriethoxysilane, and continue to stir; after the reaction is completed, centrifuge and wash with water and ethanol respectively to obtain modified MXene; Step 2, weigh 1 g of the modified MXene prepared in step 1 and disperse it in 50 ml of tetrahydrofuran, maintain low temperature ultrasonic stirring to obtain a MXene dispersion; Step 3, dissolve 4 g of hexachlorocyclotriphosphazene and 11.5 g of triethylamine in 20 ml of tetrahydrofuran, add them to the above MXene dispersion after they are completely dissolved, and continue ultrasonic stirring; Step 4, dissolve 2.0 g of hexachlorocyclotriphosphazene and 6.0 g of p-phenylenediamine in 30 ml of tetrahydrofuran, and slowly add the mixture to the mixed solution of step 3 while continuing to maintain ultrasonic stirring; after the ultrasonic stirring is completed, place the mixed solution in an oil bath and react at 50 °C for 12 h; Step 5, after the reaction is completed, the product is filtered to obtain the product, washed with tetrahydrofuran and water for three times respectively, and then dried in a vacuum oven at 50° C. to obtain a flame retardant.

7. A method for preparing an epoxy resin composite material, characterized in that: The steps include: Step 1, silane modification of MXene; Step 2, dispersing the modified MXene prepared in step 1 in tetrahydrofuran to obtain a MXene dispersion; Step 3, dissolving a certain amount of a modifier rich in phosphorus-chlorine bonds and an acid-binding agent in tetrahydrofuran, and adding the mixture to the MXene dispersion of step 2 after the mixture is completely dissolved; Step 4, dissolving a certain amount of a modifier rich in phosphorus-chlorine bonds and an organic amine in tetrahydrofuran, and then slowly dropping the dissolved modifier into the mixed solution of step 3; Step 5, after the reaction is completed, the product is filtered to obtain the product, washed with tetrahydrofuran and water for multiple times, and then dried in a vacuum oven to obtain a flame retardant; Step 6, taking a certain amount of flame retardant and acetone and adding them into a flask and mixing; Step 7, heating the epoxy resin until it melts, weighing a certain amount of the melted epoxy resin and adding it to the flask in step 6, placing the flask in an oil bath, and stirring to evaporate the acetone; Step 8, take a certain amount of curing agent, put it into a beaker and heat it until it melts, then add it to the flask in step 7 and mix it evenly, then pour it into a mold, put it into an oven for drying, and obtain a composite material.

8. The method for preparing an epoxy resin composite material according to claim 7, characterized in that: The addition amount of flame retardant is 2~4 wt% of the total mass of epoxy resin composite material.

9. A method for preparing an epoxy resin composite material, characterized in that: The steps include: Step 1, weigh 1 g of MXene and disperse it in a mixed solution of 60 ml of ethanol and 240 ml of water, maintain ultrasonic stirring at low temperature, then add 20 ml of 3-aminopropyltriethoxysilane, and continue to stir; after the reaction is completed, centrifuge and wash with water and ethanol respectively to obtain modified MXene; Step 2, weigh 1 g of the modified MXene prepared in step 1 and disperse it in 50 ml of tetrahydrofuran, maintain low temperature ultrasonic stirring to obtain a MXene dispersion; Step 3, dissolve 4 g of hexachlorocyclotriphosphazene and 11.5 g of triethylamine in 20 ml of tetrahydrofuran, add them to the above MXene dispersion after they are completely dissolved, and continue ultrasonic stirring; Step 4, dissolve 2.0 g of hexachlorocyclotriphosphazene and 6.0 g of p-phenylenediamine in 30 ml of tetrahydrofuran, and slowly add the mixture to the mixed solution of step 3 while continuing to maintain ultrasonic stirring; after the ultrasonic stirring is completed, place the mixed solution in an oil bath and react at 50 °C for 12 h; Step 5, after the reaction is completed, the product is filtered to obtain the product, washed with tetrahydrofuran and water for three times respectively, and then dried in a vacuum oven at 50° C. to obtain a flame retardant; Step 6, add 2 g of the flame retardant prepared in step 5 and a certain amount of acetone into a flask and keep ultrasonic stirring; Step 7, put the epoxy resin into an oven, heat it at 80°C until it melts, weigh 80.4 g of the melted epoxy resin and add it to the flask in step 6, continue ultrasonic stirring, and after the ultrasonication ends, place the flask in an oil bath at 90°C to stir and volatilize the acetone; Step 8, take 17.6 g of 4,4-diaminodiphenylmethane, grind it into fine powder and put it into a beaker, heat it at 120 ° C until it melts, and add it to the flask in step 7; after mixing evenly, pour it into a mold, put it into an oven and dry it at 100 ° C and 150 ° C respectively to obtain a composite material, wherein the amount of flame retardant added is 2 wt% of the total mass of the epoxy resin composite material.

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