Nanometer flame retardant, flame retardant thermoplastic polyurethane composite material

Abstract

The application belongs to the technical field of flame-retardant composite materials, and particularly relates to a nano flame retardant and a flame-retardant thermoplastic polyurethane composite material. The nano flame retardant is prepared by growing bimetallic selenide vertically on the surface of graphene oxide in situ, and at the same time, using a reducing agent to dope heteroatoms to the graphene oxide. The nano flame retardant has been proved to be able to reduce the heat release rate, total heat release, and the generation rate and yield of toxic smoke of the thermoplastic polyurethane as a modified flame retardant of the thermoplastic polyurethane material.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of flame-retardant composites, and particularly relates to a nano flame retardant and a flame-retardant thermoplastic polyurethane composite material. BACKGROUND

[0002] Thermoplastic polyurethane elastomer (TPU) is a kind of heat-plasticized elastic polyurethane. The molecular structure is a block linear polymer obtained by copolymerization of diisocyanate and polyol, and there is no chemical crosslinking, but it has certain physical crosslinking characteristics at the use temperature. TPU has excellent wear resistance, aging resistance, high resilience, etc., and is widely used in industry, life, medical treatment, military industry and other aspects.

[0003] However, TPU is a flammable material, and the limiting oxygen index (LOI) is only 16% to 18%, which will rapidly burn and decompose to produce a large amount of toxic smoke when on fire. This shortcoming also seriously affects the application of TPU in some fields with high fire safety requirements, and therefore, the research on flame-retardant modified TPU material is very important.

[0004] For example, the published patent CN202010623398.X, a low-smoke thermoplastic polyurethane elastomer composite material and a preparation method thereof, when the amount of the flame retardant added is 2wt%, the peak value of the heat release rate increases, and the peak value of the smoke release rate decreases by 37.72%; the published patent CN202010678113.2, a halogen-free flame-retardant thermoplastic polyurethane nanocomposite material and a preparation method thereof, when the amount of the flame retardant added is 2wt%, the peak value of the smoke release rate decreases by 43.80%; the published patent CN201510686290.4, a montmorillonite composite flame retardant and a preparation method thereof, when the amount of the flame retardant added is 3wt% to 30wt%, when the amount of the flame retardant added is 3wt%, the peak value of the heat release rate and the total amount of heat release decrease by 26% and 7.8%, respectively. The above-mentioned composite materials disclosed in the prior art have certain effects on the heat release rate and the smoke release rate, but still have great room for improvement. SUMMARY

[0005] The present application provides a nano flame retardant, which is prepared based on double-metal selenide and heteroatom-doped graphene, and has been confirmed to be able to reduce the heat release rate, total heat release, and generation rate and yield of toxic smoke of TPU as a modified flame retardant for TPU material.

[0006] The heteroatom-doped graphene refers to a graphene derivative in which carbon atoms in a graphene sheet are replaced by or covalently combined with other atoms including boron, nitrogen, oxygen, sulfur, fluorine, phosphorus, etc.

[0007] MoSe2 is a gray-black covalent substance with a hexagonal crystal structure, has a sandwich-like sheet structure, and the layers are loosely combined together through weak van der Waals force, the adjacent two molecular layers can slide relative to each other, has a low friction coefficient, is commonly used as a solid lubricant, has the functions of reducing material wear, reducing mechanical equipment running resistance, reducing energy consumption, and prolonging service life; in addition, it has stable chemical properties, can be used for high-temperature and high-pressure lubricants, at the same time, each molybdenum atom in MoSe2 is surrounded by six selenium atoms, forming a triangular prism, the Mo-Se edge surface is relatively large, the specific surface area is large, the surface activity is high, and the catalytic activity is excellent. Considering the sheet structure and catalytic properties, the molybdenum selenide is used as a flame retardant, which can improve the safety performance of the material and reduce the generation of smoke and harmful gases. In addition, by introducing cobalt atoms to form a double metal selenide, the catalytic sites can be enriched, and the flame retardant effect can be further improved.

[0008] The flame retardant is a double metal selenide vertically grown in situ on the surface of graphene oxide, and the presence of a reducing agent simultaneously realizes heteroatom doping of graphene oxide.

[0009] The nano flame retardant provided by the application is a double metal selenide / heteroatom-doped graphene nano flame retardant Mo-Co-Se / G, which is obtained by the following preparation process: dispersing graphene oxide powder in deionized water, adding a surfactant, the mass ratio of the graphene oxide and the surfactant is between (1:5) and (1:30); ultrasonic stirring for 1-4h, the reaction temperature is 30-60 DEG C. Then, potassium molybdate and cobalt salt are added, the mass ratio of the potassium molybdate and the cobalt salt is between (1:1) and (1:5), and the stirring is continued for 1-3h; then selenium powder and a reducing agent are added, the mass ratio of the selenium powder and the reducing agent is (1:1) to (1:40), and the stirring is continued for 0.5-2.5h; the mixed solution is added into an autoclave for treatment for 12-36h, the hydrothermal temperature is 160-240 DEG C; the primary product is collected by centrifugation, washed, and dried under vacuum conditions to obtain the final product Mo-Co-Se / G powder.

[0010] The graphene oxide is prepared by 50-1200 mesh graphite powder through Hummers method, and preferably, the mesh number of the graphite powder is 50 mesh, 80 mesh, 100 mesh, 200 mesh, 325 mesh, 400 mesh, 500 mesh, 800 mesh or 1200 mesh; the surfactant is one or more of tetradecyl trimethyl ammonium bromide, tetradecyl trimethyl ammonium chloride, dodecyl trimethyl ammonium bromide, dodecyl trimethyl ammonium chloride, hexadecyl trimethyl ammonium chloride, sodium dodecyl diphenyl ether disulfonate, polysorbate-80; the cobalt salt is one or more of cobalt sulfate, cobalt nitrate, cobalt nitrite, cobalt acetate, cobalt chloride.

[0011] When the heteroatom-doped graphene is boron-doped graphene, the reducing agent is one or more of boric acid, boric anhydride, phenyl boronic acid.

[0012] When the heteroatom-doped graphene is sulfur-doped graphene, the reducing agent is one or more of sulfur powder, hydrogen sulfide, dibenzyl disulfide, cystine, NaS2.

[0013] When the heteroatom-doped graphene is phosphorus-doped graphene, the reducing agent is one or more of red phosphorus, triphenylphosphine, ammonium dihydrogen phosphate, ammonium phosphate, phosphoric acid.

[0014] When the heteroatom-doped graphene is fluorine-doped graphene, the reducing agent is one or more of HF, diethylamine sulfur trifluoride, BF3, ammonium fluoride.

[0015] When the heteroatom-doped graphene is nitrogen-doped graphene, the reducing agent is one or more of hydrazine hydrate, ethanolamine, thiourea, dicyanediamine, cyclen.

[0016] Preferably, the washing process of the primary product is specifically: washing with distilled water for 3 times, and washing with ethanol for 2 times.

[0017] Preferably, the drying process of the primary product after washing under vacuum conditions is specifically: drying in a vacuum oven at 60-100 DEG C for 12-48 hours to obtain the final product Mo-Co-Se / G powder.

[0018] The application also provides the application of the above-mentioned nano flame retardant Mo-Co-Se / G as a modification flame retardant of thermoplastic polyurethane elastomer TPU, that is, a flame-retardant thermoplastic polyurethane composite material is provided, which is prepared by adding the nano flame retardant to TPU, and the addition amount of the nano flame retardant is 2wt% of the total mass after mixing the nano flame retardant and TPU, and then solution compounding and banburying are carried out to prepare the flame-retardant thermoplastic polyurethane composite material, so as to improve the flame-retardant property of the thermoplastic polyurethane material.

[0019] As a preferred embodiment of the present application, the preparation method of the flame-retardant thermoplastic polyurethane composite material specifically comprises the following steps:

[0020] After ultrasonic stirring for 2-8 h, TPU is added, and the addition amount of the nano flame retardant is 2 wt% of the total mass of the mixture of the nano flame retardant and TPU, the temperature is raised to 45-65℃, and stirring is maintained for 3-8 h to obtain a composite solution;

[0021] The composite solution is added to deionized water, and after the composite material is precipitated, it is dried at 70-100℃ for 12-48 h, and then subjected to internal mixing and pressurization at 180-190℃ to obtain the flame-retardant thermoplastic polyurethane composite material.

[0022] The organic solvent is one or more of tetrahydrofuran, acetone, N,N-dimethylformamide, N,N-dimethylacetamide, and 1,4-dioxane.

[0023] Invention principle: In-situ growth of molybdenum selenide nanosheets on graphene nanomaterials is generally used for electrocatalysis. Good catalytic performance is required if it is used as a flame retardant. Based on the existing in-situ growth of molybdenum selenide nanosheets on graphene nanomaterials, if it is directly used as a flame retardant, there will be problems of poor dispersibility and low flame retardant efficiency. Based on the existing material, the present application combines heteroatom-doped graphene and double-metal selenide to obtain a new flame retardant through material structure and interface assembly strategies, and plays the synergistic flame-retardant effect of physical barrier, free radical capture, and catalytic carbonization, significantly improves the flame-retardant performance of the material, and reduces the generation of toxic and harmful smoke. The specific improvements include the following points:

[0024] 1. A milder hydrothermal selenization reaction is used instead of a high-temperature selenization reaction to obtain a double-metal selenide, so that the double-metal selenide has more defects, and the presence of defects helps to improve the catalytic activity of the nano flame retardant. The flame-retardant catalysis of the nano flame retardant is different from electrocatalysis. The specific process of flame-retardant catalysis is to promote the condensation, polymerization, and aromatization reactions of the pyrolysis products of the polymer matrix material, and catalyze the generation of crosslinked carbon layers. Therefore, the nano flame retardant provided by the present application can promote the crosslinking and carbonization process during the polymer combustion process when used for flame-retardant modification of thermoplastic polyurethane, and generate more protective carbon layers. At the same time, the double-metal selenide formed by introducing cobalt atoms has more redox reaction sites than single-metal compounds. The construction of two-phase heterostructures can lead to the generation of phase interfaces, which often have rich lattice defects and hetero-electronic states, making the material have more catalytic sites, which helps to crosslink and carbonize, and the generated carbon layer can act as a barrier layer for external heat and pyrolysis products, inhibiting their diffusion and transmission, and further improving the flame-retardant effect;

[0025] 2、The nanometer flame retardant provided by the application is prepared from a raw material of heteroatom-doped graphene, the heteroatom-doped graphene has more lattice defects, has better thermal conductivity and free radical capturing effect than undoped graphene, and improves the overall flame retardant performance of the nanometer flame retardant;

[0026] 3. The use of a surfactant as a structure-directing agent helps to enhance the contact area of the nanometer flame retardant and the polymer, improve the material dispersibility and interfacial force, form a continuous physical barrier and chemical catalysis network, and help to improve the flame retardant performance of the flame-retardant thermoplastic polyurethane composite material.

[0027] 4、The flame-retardant thermoplastic polyurethane composite material provided by the application converts metal selenide into metal oxide during combustion, and the metal oxide has Lewis acid characteristics, promoting catalytic charring.

[0028] Compared with the prior art, the beneficial effects of the application are embodied in:

[0029] 1、The existing technology 1, namely the published patent CN202010623398.X, a low-smoke thermoplastic polyurethane elastomer composite material and a preparation method thereof, when the amount of the flame retardant added is 2wt%, the heat release rate peak value rises and the smoke release rate peak value decreases by 37.7%. The nanometer flame retardant of double metal selenide / heteroatom-doped graphene provided by the application has the advantage of high flame retardant efficiency. When 2wt% of the nanometer flame retardant is added, the heat release rate peak value and the smoke release rate peak value of the TPU decrease by 48.6% and 49.0%, respectively, which is significantly better than the existing technology 1.

[0030] 2、The existing technology 2, namely the published patent CN202010678113.2, a halogen-free flame-retardant thermoplastic polyurethane nanocomposite material and a preparation method thereof, when the amount of the flame retardant added is 2wt%, the smoke release rate peak value decreases by 43.8%. The nanometer flame retardant of double metal selenide / heteroatom-doped graphene provided by the application has the advantage of high flame retardant efficiency. When 2wt% of the nanometer flame retardant is added, the smoke release rate peak value of the TPU decreases by 49.0%, which is significantly better than the existing technology 2.

[0031] 3、The existing technology 3, namely the published patent CN201510686290.4, a montmorillonite composite flame retardant and a preparation method thereof, when the amount of the flame retardant added is 3-30wt%, the heat release rate peak value and the total heat release amount decrease by 26.0% and 7.8%, respectively, when the amount of the flame retardant added is 3wt%. The nanometer flame retardant of double metal selenide / heteroatom-doped graphene provided by the application has the advantage of high flame retardant efficiency. When 2wt% of the nanometer flame retardant is added, the heat release rate peak value and the total heat release amount of the TPU decrease by 48.6% and 21.3%, respectively, which is significantly better than the existing technology 3. BRIEF DESCRIPTION OF DRAWINGS

[0032] Figure 1a Scanning electron microscope image of the intermediate product, graphene oxide, prepared for the nanoflame retardant of Example 1 ;

[0033] Figure 1b Scanning electron microscope image of the intermediate product, nitrogen-doped graphene, prepared for the nanoflame retardant of Example 1 ;

[0034] Figure 1c Scanning electron microscope image of the nanoflame retardant Mo-Co-Se / G;

[0035] Figure 2 Transmission electron microscope image of the nanoflame retardant Mo-Co-Se / G is shown;

[0036] Figure 3a is the heat release rate curve of the commercial TPU and the prepared flame retardant TPU;

[0037] Figure 3b is the total heat release curve of the commercial TPU and the prepared flame retardant TPU;

[0038] Figure 3c is the smoke production rate curve of the commercial TPU and the prepared flame retardant TPU;

[0039] Figure 3d is the specific extinction area curve of the commercial TPU and the prepared flame retardant TPU;

[0040] Figure 4a is the TG-IR curve of the hydrocarbon products of the commercial TPU and the prepared flame retardant TPU;

[0041] Figure 4b is the TG-IR curve of the ester products of the commercial TPU and the prepared flame retardant TPU;

[0042] Figure 4c is the TG-IR curve of the aromatic compounds of the commercial TPU and the prepared flame retardant TPU;

[0043] Figure 4d is the TG-IR curve of the CO products of the commercial TPU and the prepared flame retardant TPU;

[0044] Figure 4e is the TG-IR curve of the NO products of the commercial TPU and the prepared flame retardant TPU;

[0045] Figure 4f is the TG-IR curve of the hydrogen cyanide products of the commercial TPU and the prepared flame retardant TPU;

[0046] Figure 5The mechanical tensile property test of the commercially available TPU and the prepared flame-retardant TPU material is carried out. DETAILED DESCRIPTION

[0047] In order to further illustrate the technical solutions of the present application, the preferred embodiments of the present application are described below in combination with examples, but it should be understood that these descriptions are only for further illustrating the features and advantages of the present application, and are not a limitation on the claims of the present application. Based on the examples in the present application, all other examples obtained by those skilled in the art without creative labor are within the scope of protection of the present application.

[0048] Meanwhile, the raw materials or reagents mentioned below without detailed description are all commercially available products, and the process steps or methods without detailed description are all known process steps or methods to those skilled in the art.

[0049] The sources of some raw materials and reagents involved in the following examples and test examples are shown as follows:

[0050] Tetradecyl trimethyl ammonium bromide was purchased from National Pharmaceutical Group Chemical Reagent Co., Ltd.;

[0051] Potassium molybdate was purchased from National Pharmaceutical Group Chemical Reagent Co., Ltd.;

[0052] Cobalt sulfate was purchased from National Pharmaceutical Group Chemical Reagent Co., Ltd.;

[0053] Cobalt nitrate was purchased from National Pharmaceutical Group Chemical Reagent Co., Ltd.;

[0054] Cobalt chloride was purchased from National Pharmaceutical Group Chemical Reagent Co., Ltd.;

[0055] Selenium powder was purchased from National Pharmaceutical Group Chemical Reagent Co., Ltd.;

[0056] Hydrazine hydrate was purchased from National Pharmaceutical Group Chemical Reagent Co., Ltd.;

[0057] Ethanolamine was purchased from National Pharmaceutical Group Chemical Reagent Co., Ltd.;

[0058] Thiourea was purchased from National Pharmaceutical Group Chemical Reagent Co., Ltd.;

[0059] Acetone was purchased from National Pharmaceutical Group Chemical Reagent Co., Ltd.;

[0060] TPU was polyester type 85E85, purchased from Baoding Bangtai High Polymer New Material Co., Ltd.;

[0061] The graphene oxide used in the following examples 1, 3 and 4 is prepared by Hummers method. Specifically, it is prepared by the following process: 230 ml of concentrated sulfuric acid is added into a beaker and stirred until the temperature drops below 5 degrees; then 10 g of graphite powder and 5 g of sodium nitrate are slowly added, wherein the graphite powder is 400 mesh and purchased from the National Pharmaceutical Group Chemical Reagent Co., Ltd., and stirring is performed while adding; after the graphite powder and sodium nitrate are added, 30 g of potassium permanganate is slowly added, and after the potassium permanganate is added, low-temperature oxidation is maintained for 1 hour; the oil bath is heated to 35 degrees, and 460 ml of deionized water is added, then the oil bath is heated to 90 degrees, and after 20 min, 700 ml of warm water is poured in, and after another 15 min, 25 ml of hydrogen peroxide is added, and then the reaction is carried out for another 30 min. The product is obtained by suction filtration, washed with hydrochloric acid twice, and finally washed with deionized water until neutral, and dried to obtain graphene oxide powder.

[0062] Example 1

[0063] This example 1 is a specific preparation process of the Mo-Co-Se / G powder described in the present application: 0.2 g of graphene oxide powder is dispersed in deionized water, and 1 g of tetradecyl trimethyl ammonium bromide is added; ultrasonic stirring is performed for 2 h, and the reaction temperature is 50°C; then, 1 g of potassium molybdate and 1 g of cobalt sulfate are added, and stirring is continued for 2 h; then, 1 g of selenium powder and 1 g of hydrazine hydrate are added, and stirring is continued for 0.5 h. The mixture is added to an autoclave and treated for 12 h at a hydrothermal temperature of 160°C; the product is collected by centrifugation, washed with distilled water 3 times, washed with ethanol 2 times, and finally dried in a vacuum oven at 60°C for 12 hours to obtain the Mo-Co-Se / G powder.

[0064] Example 2

[0065] This example 2 is a preparation method of a flame-retardant TPU, which comprises the following steps: step 1: 2 g of Mo-Co-Se / G powder is added to 150 ml of acetone, and ultrasonic stirring is performed for 2 h. Then, 98 g of TPU is added, the temperature is raised to 50°C, and stirring is maintained for 5 h. Step 2: The solution obtained in step 1 is added to deionized water, and after the composite material is precipitated, it is cut into blocks, dried at 100°C for 12 h, and then subjected to internal mixing and compression at 180°C to obtain a TPU composite material.

[0066] Example 3

[0067] This embodiment 3 is a specific preparation process of Mo-Co-Se / G powder according to the present application: 0.2 g of graphene oxide powder is dispersed in deionized water, and 1.2 g of dodecyl trimethyl ammonium bromide is added. Ultrasonic stirring for 2 h, the reaction temperature is 50℃. Subsequently, 1 g of potassium molybdate and 1.2 g of cobalt nitrate are added, and stirring is continued for 2 h. Then 0.8 g of selenium powder and 1.6 g of ethanolamine are added, and stirring is continued for 0.5 h. The mixture is added to an autoclave for treatment for 12 h, and the hydrothermal temperature is 160℃; the product is collected by centrifugation, washed with distilled water for 3 times, washed with ethanol for 2 times, and finally dried in a vacuum oven at 80℃ for 12 hours to obtain Mo-Co-Se / G powder.

[0068] Embodiment 4

[0069] This embodiment 4 is a specific preparation process of Mo-Co-Se / G powder according to the present application: 0.3 g of graphene oxide powder is dispersed in deionized water, and 1.5 g of hexadecyl trimethyl ammonium chloride is added. Ultrasonic stirring for 2 h, the reaction temperature is 50℃. Subsequently, 1.5 g of potassium molybdate and 1.5 g of cobalt chloride are added, and stirring is continued for 2 h. Then 0.7 g of selenium powder and 1.4 g of thiourea are added, and stirring is continued for 0.5 h. The mixture is added to an autoclave for treatment for 12 h, and the hydrothermal temperature is 160℃; the product is collected by centrifugation, washed with distilled water for 3 times, washed with ethanol for 2 times, and finally dried in a vacuum oven at 60℃ for 24 hours to obtain Mo-Co-Se / G powder.

[0070] As Figure 1a shown in the TEM image of graphene oxide prepared in Example 1, the outline of the graphene oxide sheet is clear, and the surface is smooth;

[0071] As Figure 1b shown in the TEM image of graphene oxide prepared in Example 1, the outline of the graphene oxide sheet is clear, and the surface is smooth;

[0072] As Figure 2 shown in the TEM image of graphene oxide prepared in Example 1, the outline of the graphene oxide sheet is clear, and the surface is smooth;

[0073] Test Example 1: Cone calorimeter test of commercially available TPU and flame-retardant TPU prepared in Example 2

[0074] The specific test process is as follows: according to ISO5660 standard, the cone calorimeter (UK, Fire Testing Technology) is used for combustion test of the sample, and the specific sample is commercially available TPU and flame-retardant TPU prepared in Example 2, and the sample size is 100×100×3mm 3, the heat flux is 35 kW / m 2 The heat release curve was calculated based on the oxygen consumption principle, while monitoring the smoke release rate and specific extinction area parameters.

[0075] Figure 3a The heat release rate curve is shown. Figure 3b The total heat release curve is shown. Figure 3c The smoke production rate curve is shown. Figure 3d The specific extinction area curve is shown. It can be seen that the peak heat release rate, total heat release, peak smoke release rate and peak specific extinction area of pure TPU are 1468 kW / m 2 , 122 MJ / m 2 , 0.312 m 2 / s and 0.076 m 2 / kg. After adding 2.0 wt% flame retardant, the peak heat release rate and total heat release of TPU are reduced by 48.6% and 21.3% respectively, indicating that Mo-Co-Se / G has good flame retardant effect. The peak smoke release rate and peak specific extinction area are also reduced, by 49.0% and 50.0% respectively, indicating that Mo-Co-Se / G can significantly inhibit the release of heat and toxic smoke during the combustion process of TPU.

[0076] Test Example 2: Thermogravimetric Infrared TG-IR Test of Commercial TPU and Flame Retardant TPU Prepared in Example 2

[0077] The specific test process is as follows: TGIR results are obtained by using Nicolet6700 FTIR spectrophotometer and TGA Q5000 thermogravimetric analyzer, the test atmosphere is nitrogen, the heating rate is 20℃ / min, the sample mass of commercial TPU and flame retardant TPU prepared in Example 2 is about 20mg, after the combination of thermogravimetric and infrared, the gas components decomposed by the sample during the process of programmed temperature weight loss are transmitted to the infrared gas detection cell through the constant temperature conveying pipe, and the escaped gas is analyzed qualitatively and quantitatively.

[0078] Figure 4a is the test result of hydrocarbon products, after adding 2.0 wt% flame retardant, the absorbance peak of TPU is reduced by 46.8%;

[0079] Figure 4b is the test result of ester products, after adding 2.0 wt% flame retardant, the absorbance peak of TPU is reduced by 51.4%;

[0080] Figure 4c is the test result of aromatic compounds, after adding 2.0 wt% flame retardant, the absorbance peak of TPU is reduced by 49.1%;

[0081] Figure 4d The test results for CO products show that after adding 2.0 wt% flame retardant, the peak absorbance of TPU decreased by 36.1%.

[0082] Figure 4e The test results for NO products show that after adding 2.0 wt% flame retardant, the peak absorbance of TPU decreased by 49.2%.

[0083] Figure 4f The test results for hydrogen cyanide products show that after adding 2.0 wt% flame retardant, the peak absorbance of TPU decreased by 45.9%.

[0084] The above results indicate that the generation of both flammable and toxic gases is suppressed after using Mo-Co-Se / G.

[0085] Test Example 3: Mechanical tensile property testing of commercially available TPU and flame-retardant TPU prepared in Example 2

[0086] The specific testing process is as follows: Mechanical properties were tested and recorded using a universal tensile tester (CMT4204, China MTS Systems Co., Ltd.). The samples were commercially available TPU and flame-retardant TPU prepared in Example 2. Five specimens were tested for each sample and the specimens were prepared according to the national standard GB / T1040. The tensile strength and elongation at break data were obtained from the test.

[0087] like Figure 5 As shown, the flame-retardant TPU prepared in Example 2 did not have reduced tensile properties due to the addition of flame retardants. Compared with commercially available TPU, its tensile strength increased from 35.5 MPa to 46.7 MPa, and its elongation at break increased from 620.01% to 660.84%.

Claims

1. A nanoflame retardant, characterized by, The nano flame retardant is prepared by growing bimetallic selenide vertically in situ on the surface of graphene oxide, while heteroatom doping the graphene oxide with a reducing agent, and is obtained by the following preparation process: graphene oxide powder is dispersed in deionized water, a surfactant is added, the mass ratio of the graphene oxide and the surfactant is between (1:5) and (1:30); ultrasonic stirring is performed for 1-4 hours, and the reaction temperature is 30-60 DEG C; then potassium molybdate and a cobalt salt are added, the mass ratio of the potassium molybdate and the cobalt salt is between (1:1) and (1:5), and stirring is continued for 1-3 hours; then selenium powder and a reducing agent are added, the mass ratio of the selenium powder and the reducing agent is between (1:1) and (1:40), and stirring is continued for 0.5-2.5 hours; the mixture is added into an autoclave for treatment for 12-36 hours, and the hydrothermal temperature is 160-240 DEG C; the primary product is collected by centrifugation, washed, and dried under vacuum to obtain the final product Mo-Co-Se / G powder; wherein the graphene oxide is prepared by 50-1200 mesh graphite powder by Hummers method, and the surfactant is one or more of tetradecyl trimethyl ammonium bromide, tetradecyl trimethyl ammonium chloride, dodecyl trimethyl ammonium bromide, dodecyl trimethyl ammonium chloride, hexadecyl trimethyl ammonium chloride, sodium dodecyl diphenyl ether disulfonate, and polysorbate-80; the cobalt salt is one or more of cobalt sulfate, cobalt nitrate, cobalt nitrite, cobalt acetate, and cobalt chloride. The heteroatom doping refers to that the carbon atoms in the graphene sheet are replaced by nitrogen or covalently combined, and the reducing agent is one or more of hydrazine hydrate, ethanolamine, thiourea, dicyanediamine, and cyclen.

2. A nano flame retardant as claimed in claim 1, wherein, The mesh number of the graphite powder is 50 mesh, 80 mesh, 100 mesh, 200 mesh, 325 mesh, 400 mesh, 500 mesh, 800 mesh, or 1200 mesh.

3. A nano flame retardant as claimed in claim 1, wherein, The washing process of the primary product specifically comprises: washing with distilled water for 3 times, and washing with ethanol for 2 times.

4. A nano flame retardant as claimed in claim 1, wherein, The drying process of the primary product after washing under vacuum specifically comprises: drying in a vacuum oven at 60-100 DEG C for 12-48 hours to obtain the final product Mo-Co-Se / G powder.

5. A nano flame retardant as claimed in claim 1, wherein, The mass ratio of the graphene oxide and the surfactant is 1:

5.

6. A nano flame retardant as claimed in claim 1, wherein, The mass ratio of the potassium molybdate and the cobalt salt is 1:

1.

7. A nano flame retardant as claimed in claim 1, wherein, The mass ratio of the selenium powder and the reducing agent is 1:

1.

8. A flame retardant thermoplastic polyurethane composite, characterized in that, The flame-retardant thermoplastic polyurethane composite is prepared by adding the nano flame retardant of any one of claims 1-7 to TPU, the addition amount of the nano flame retardant being 2wt% of the total mass of the mixture of the nano flame retardant and the TPU, and then solution compounding and banburying.

9. A flame retardant thermoplastic polyurethane composite as in claim 8, wherein, The flame-retardant thermoplastic polyurethane composite is prepared by the following process: the nano flame retardant of any one of claims 1-7 is taken into an organic solvent, ultrasonic stirring is carried out for 2-8 h, then TPU is added, and the addition amount of the nano flame retardant is 2 wt% of the total mass after the nano flame retardant and the TPU are mixed, the temperature is raised to 45-65 DEG C, stirring is maintained for 3-8 h, and a composite solution is obtained; the composite solution is added to deionized water, after the composite material is precipitated, 70-100 DEG C drying is carried out for 12-48 h, and the flame-retardant thermoplastic polyurethane composite is obtained by banburying and pressing at 180-190 DEG C; wherein the organic solvent is one or more of tetrahydrofuran, acetone, N,N-dimethylformamide, N,N-dimethylacetamide, 1,4-dioxane.

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