Preparation method of nano flame retardant and flame retardant thermoplastic polyurethane composite material

Abstract

The application discloses a kind of nano flame retardant, the preparation method of flame-retardant thermoplastic polyurethane composite material, modified boron nitride is placed in deionized water, then buffer solution is added, and dopamine hydrochloride is weighed and added to mixed solution to react;After reaction, product is obtained by suction filtration, washed to neutral, and dried to obtain P@BN;P@BN is taken and dispersed in deionized water, and mixed metal salt is added to form dispersion liquid two;At the same time, selenium powder is placed in hydrazine hydrate solution to form selenium solution;Selenium solution is added to dispersion liquid two, and hydrothermal reaction is carried out;The primary product is sequentially collected by centrifugation, washed, dried, to obtain nano flame retardant P@BN-BMSe.Nano flame retardant P@BN-BMSe is taken and placed in organic solvent, ultrasonic stirring is carried out, thermoplastic polyurethane elastomer rubber is added, to obtain composite solution;Composite solution is added to deionized water, and after separation, drying is carried out, and ban, compression plate are obtained to prepare flame-retardant thermoplastic polyurethane composite 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 preparation method of a flame-retardant thermoplastic polyurethane composite. 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%-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 it is very important to modify TPU materials by flame retardation.

[0004] For example, the published patent CN202010623398.X discloses a low-smoke thermoplastic polyurethane elastomer composite and a preparation method thereof. When the amount of the flame retardant is 2wt%, the peak value of the heat release rate increases, and the peak value of the smoke release rate decreases by 37.7%. The published patent CN202010678113.2 discloses a halogen-free flame-retardant thermoplastic polyurethane nanocomposite and a preparation method thereof. When the amount of the flame retardant is 2wt%, the peak value of the smoke release rate decreases by 43.8%. The published patent CN201510686290.4 discloses a montmorillonite composite flame retardant and a preparation method thereof. When the amount of the flame retardant is 3wt%, the peak value of the heat release rate and the total amount of heat release decrease by 26.0% and 7.8%, respectively. The above-mentioned composites disclosed in the prior art have a certain reduction in the heat release rate, the smoke release rate and other parameters, but there is still a large space for improvement. SUMMARY

[0005] The purpose of the present application is to provide a preparation method of a nano flame retardant and a flame-retardant thermoplastic polyurethane composite. In view of the problem that TPU will rapidly burn and decompose to produce a large amount of toxic smoke when on fire, the nano flame retardant provided by the present application is prepared based on double metal selenide and modified boron nitride, and as a modified flame retardant for TPU materials, it can reduce the heat release rate, total heat release, and the generation rate and yield of toxic smoke of TPU.

[0006] In order to solve the above technical problems, the present application is implemented in the following manner:

[0007] The preparation method of the double metal selenide / modified boron nitride nano flame retardant comprises the following steps:

[0008] Step 1: Put modified boron nitride into deionized water, and obtain a uniform dispersion solution I by ultrasonic; take a buffer solution, add it into the dispersion solution I, and then take dopamine hydrochloride, add it into the mixed solution for reaction; after the reaction is completed, the product is obtained by suction filtration, then washed with deionized water until the pH is neutral, dried and collected to obtain P@BN;

[0009] Step 2: take P@BN dispersed in deionized water, then add mixed metal salt, ultrasonic stirring, form dispersion solution II; at the same time, take selenium powder into hydrazine hydrate solution, magnetic stirring to dissolve, form selenium solution; add the selenium solution into the dispersion solution II, continue to ultrasonic stirring, then carry out hydrothermal reaction; the initial product after reaction is collected by centrifugation, washed, dried to obtain the final product nanometer flame retardant P@BN-BMSe.

[0010] Further optimization, in step 1, the boron and the modifier are placed in a high-energy ball mill for synchronous peeling and modification to obtain modified boron nitride.

[0011] The boron nitride is a crystal composed of nitrogen atoms and boron atoms, and the boron nitride has four different variants, each variant having a unique crystal structure. It has high thermal conductivity, high hardness, high chemical stability and excellent lubricity, etc. Due to its excellent thermal conductivity and electrical insulation performance, it is often used as a chip carrier, heat sink and other high-temperature electronic packaging materials; in addition, due to its high corrosion resistance and high temperature stability, it is often used as a high corrosion resistant material, a release agent and a lubricant. The boron nitride surface has few functional groups, and it is easy to form agglomeration in the polymer matrix, which is not conducive to performance improvement. Therefore, the modification agent is added to the high-energy ball mill for synchronous peeling to obtain modified boron nitride by interface engineering strategy, which significantly improves the dispersibility.

[0012] Further optimization, the boron nitride is one of hexagonal boron nitride (h-BN), rhombohedral boron nitride (r-BN), cubic boron nitride (c-BN) or wurtzite boron nitride (w-BN).

[0013] The modifier is a mixture of one or more of urea, dicyandiamide, melamine and hexamethylene tetramine.

[0014] Further optimization, in step 2, the mass ratio of P@BN to mixed metal salt is (1:3)~(1:10), the mixed metal salt is composed of two metal salts, and the mass ratio of the two is 1:1.

[0015] Further optimization, in step 2, the dosage ratio of P@BN, selenium powder and hydrazine hydrate is 1g:(1-5)g:(10-30)ml.

[0016] There are three types of chemical bonds in metal selenides: M-M (metal-metal), M-Se (metal-selenium), and Se-Se (selenium-selenium). The formation of these chemical bonds allows metal selenides to have multiple crystal structures and exhibit unique physical and chemical properties. Certain transition metal selenides have large specific surface areas, high surface activities, and excellent catalytic activities. Considering their lamellar structure and catalytic properties, metal selenides can be used as flame retardants to improve the safety performance of materials and reduce the generation of smoke and harmful gases. The two metal elements in double metal selenides can produce synergistic catalytic effects, enhance charge transport, and improve catalytic activity. Double metal selenides also generally have high electrical conductivity, which is beneficial for electron transport and the progress of catalytic reactions. Double metal selenides can form more active sites due to the coexistence of two metal elements, which is conducive to the progress of catalytic reactions. This flame retardant is a double metal selenide grown in situ on the surface of modified boron nitride, obtaining a multi-level flame-retardant nanostructure.

[0017] Further optimization, the buffer solution is one or more of Tris-HCl buffer, acetic acid / sodium acetate buffer solution, citrate buffer solution, phosphate buffer solution, glycine / HCl buffer solution, tartaric acid / tartaric acid sodium buffer solution.

[0018] The metal salt is two of sodium molybdate, calcium molybdate, zinc molybdate, cobalt sulfate, cobalt nitrate, cobalt acetate, cobalt chloride, nickel nitrate, nickel acetate, nickel chloride, iron nitrate, iron acetate, iron chloride, copper nitrate, copper acetate, copper chloride.

[0019] Further optimization, in step 2, the initial product is washed with distilled water 3 times and ethanol 2 times; the initial product is dried in a vacuum oven at 50-70 ℃ for 12-48 h after washing to obtain the final product P@BN-BMSe powder.

[0020] The preparation method of the flame-retardant thermoplastic polyurethane composite material is based on the nanometer flame-retardant P@BN-BMSe prepared above, and specifically includes the following steps:

[0021] Step 1: Put the nanometer flame retardant P@BN-BMSe into an organic solvent, and after ultrasonic stirring for 2-8 h, add a thermoplastic polyurethane elastomer rubber, heat to 45-65 ℃, and keep stirring for 3-8 h to obtain a composite solution;

[0022] Step 2: Add the composite solution to deionized water, and after the composite material is precipitated, dry at 70-100 ℃ for 48-96 h, and then perform internal mixing and platen at 180-190 ℃ to obtain the preparation of the flame-retardant thermoplastic polyurethane composite material.

[0023] Further optimization, the addition amount of the nano flame retardant P@BN-BMSe is 2wt% of the total mass of the mixture of the nano flame retardant P@BN-BMSe and the thermoplastic polyurethane elastomer rubber.

[0024] Further optimization, the organic solvent is one or more of tetrahydrofuran, acetone, N, N-dimethylformamide, N, N-dimethylacetamide, 1, 4-dioxane.

[0025] The present application relates to the principle and improvement point analysis:

[0026] The in-situ growth of bimetallic selenide on the modified boron nitride nanosheet has good catalytic performance, and is generally applied to electrocatalysis. If used as a flame retardant, its flame retardant performance needs to be considered. Based on the existing in-situ growth of bimetallic selenide on the boron nitride nanosheet, if directly used as a flame retardant, there will be problems of poor dispersibility and low flame retardant efficiency. Based on the existing material, the modified boron nitride nanosheet and the bimetallic selenide are combined to obtain a new flame retardant through interface engineering strategy, which plays a synergistic flame retardant effect of physical barrier, free radical capture and catalytic carbon formation, 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:

[0027] 1. During the synthesis of boron nitride, in addition to trace amounts of -OH and -NH2 groups remaining on the edges, there are almost no other functional groups, so it is easy to form agglomeration in the matrix. In the present application, boron nitride powder and a modifier are placed in a high-energy ball mill to carry out synchronous peeling and modification to obtain boron nitride nanosheets. Then, through a design strategy, a polydopamine modification layer is formed on the surface of the boron nitride. The modification layer has abundant amine groups, which can effectively form a chelate structure with metal ions.

[0028] 2. A bimetallic selenide is obtained by using a milder hydrothermal selenization reaction instead of a high-temperature selenization reaction, so that the bimetallic selenide has more defects, and the existence 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, and the specific process is as follows: promoting the condensation, polymerization and aromatization reactions of the pyrolysis products of the polymer matrix material, and catalyzing the generation of a crosslinked carbon layer. The carbon layer can block the diffusion and transmission of external heat and pyrolysis products, further improving the flame retardant effect.

[0029] Therefore, the nano flame retardant prepared in the present application can promote the crosslinking and carbonization process during the polymer combustion process when used for TPU flame retardant modification, and generate more protective carbon layers. Compared with single-metal selenide, bimetallic selenide has more redox reaction sites and phase interfaces. The existence of abundant lattice defects, heterogeneous electronic states and other defects at the phase interface makes the material have more catalytic sites, which helps to crosslink and carbonize.

[0030] 3、The prepared flame-retardant TPU composite in the combustion process, the metal selenide will be converted into metal oxide, and the metal oxide has chemical catalysis and Lewis acid characteristics, which promotes carbonization.

[0031] The beneficial effects of the present application are as follows:

[0032] The prepared bimetallic selenide / modified boron nitride nanometer flame retardant has the advantages of high flame-retardant efficiency. BRIEF DESCRIPTION OF DRAWINGS

[0033] Figure 1 The scanning electron microscope image of BN in Example 1 is shown in the figure.

[0034] Figure 2 The scanning electron microscope image of the intermediate product P@BN of the nanometer flame retardant prepared in Example 1 is shown in the figure.

[0035] Figure 3 The scanning electron microscope image of the nanometer flame retardant P@BN-BMSe prepared in Example 1 is shown in the figure.

[0036] Figure 4 The transmission electron microscope image of the nanometer flame retardant P@BN-BMSe prepared in Example 1 is shown in the figure.

[0037] Figure 5 The transmission electron microscope image of the nanometer flame retardant P@BN-BMSe prepared in Example 2 is shown in the figure.

[0038] Figure 6 The transmission electron microscope image of the nanometer flame retardant P@BN-BMSe prepared in Example 3 is shown in the figure.

[0039] Figure 7 The heat release rate curve of the commercial TPU and the prepared flame-retardant TPU is shown in the figure.

[0040] Figure 8 The total heat release curve of the commercial TPU and the prepared flame-retardant TPU is shown in the figure.

[0041] Figure 9 The smoke production rate curve of the commercial TPU and the prepared flame-retardant TPU is shown in the figure.

[0042] Figure 10 The CO release rate curve of the commercial TPU and the prepared flame-retardant TPU is shown in the figure.

[0043] Figure 11 The TG-IR curve of the hydroxyl product of the commercial TPU and the prepared flame-retardant TPU is shown in the figure.

[0044] Figure 12 The TG-IR curve of the ester product of the commercial TPU and the prepared flame-retardant TPU is shown in the figure.

[0045] Figure 13 TG-IR curve of aromatic compound of the commercial TPU and the prepared flame-retardant TPU;

[0046] Figure 14 TG-IR curve of ether compound product of the commercial TPU and the prepared flame-retardant TPU;

[0047] Figure 15 TG-IR curve of aromatic ether product of the commercial TPU and the prepared flame-retardant TPU;

[0048] Figure 16 TG-IR curve of hydrogen cyanide product of the commercial TPU and the prepared flame-retardant TPU;

[0049] Figure 17 Tensile strength and elongation at break test results of the commercial TPU and the prepared flame-retardant TPU. DETAILED DESCRIPTION

[0050] In order to further illustrate the technical solutions of the present application, the preferred embodiments of the present application 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 application, and are not limitations on the claims of the present application. Based on the examples in the present application, all other examples obtained by those of ordinary skill in the art without making creative efforts fall within the scope of protection of the present application.

[0051] 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.

[0052] The sources of some raw materials and reagents involved in the following examples and test examples are shown as follows:

[0053] Tris-hydroxymethyl aminomethane / hydrochloric acid buffer, purchased from Sinopharm Chemical Reagent Co., Ltd.;

[0054] Citrate buffer, Shanghai McLean Biotechnology Co., Ltd.;

[0055] Glycine / hydrochloric acid buffer, Shanghai McLean Biotechnology Co., Ltd.;

[0056] Dopamine hydrochloride, purchased from Tianjin Xinsen Aoptek Technology Co., Ltd.;

[0057] Sodium molybdate dihydrate, purchased from Sinopharm Chemical Reagent Co., Ltd.;

[0058] Magnesium molybdate, Shanghai Bailingwei Chemical Technology Co., Ltd.;

[0059] Calcium molybdate, Shanghai Bailingwei Chemical Technology Co., Ltd.

[0060] Selenium powder, purchased from National Pharmaceutical Group Chemical Reagent Co., Ltd.

[0061] Hydrazine hydrate, purchased from National Pharmaceutical Group Chemical Reagent Co., Ltd.

[0062] N,N-dimethylformamide, purchased from National Pharmaceutical Group Chemical Reagent Co., Ltd.

[0063] TPU is polyester type 85E85, purchased from Baoding Bangtai High Polymer New Material Co., Ltd. Example 1

[0064] This example 1 is a specific preparation process of the P@BN-BMSe powder described in the application: first, 5g boron nitride and 0.5g urea are placed in a high-energy ball mill, and ball-milled at a speed of 1600rpm for 12h, and then exfoliated boron nitride is obtained. As shown in the electron microscope image of the exfoliated boron nitride, it can be seen that the BN sheet layer profile is clear and the surface is smooth. Figure 1

[0065] Take 1g exfoliated boron nitride and disperse it in deionized water, ultrasonic for 4h to obtain a uniform solution, add 400ml tris-hydroxymethyl aminomethane / hydrochloric acid buffer solution, ultrasonic for 1h, then take 0.4g dopamine hydrochloride and add it to the solution, room temperature magnetic stirring for 6h, after the reaction is completed, suction filtration to obtain the product, wash with deionized water until the pH is neutral, dry at 70 degrees, and collect the product, which is modified boron nitride P@BN. As shown in the electron microscope image of P@BN, the doped boron nitride is in block shape and the surface is rough. Figure 2

[0066] Take 0.5g P@BN and disperse it in deionized water, add 0.75g sodium molybdate and 0.75g cobalt nitrate, continue to ultrasonic stirring for 1h; at the same time, take 0.5g Se powder and place it in 5ml hydrazine hydrate solution, keep stirring for 1h, add Se solution to P@BN solution, continue to ultrasonic stirring for 1h; then hydrothermal reaction at 200 degrees for 24h, cool and centrifuge, wash with deionized water for 3 times, ethanol for 2 times, and finally dry in a vacuum oven for 24h to obtain P@BN-BMSe-1 powder.

[0067] As shown in the electron microscope image of the nanometer flame retardant P@BN-BMSe-1 prepared in this example, it can be seen that flower-shaped selenium nanosheets grow on the doped P@BN. Figure 3 Figure 4 As shown in the transmission electron microscope image of the nanometer flame retardant P@BN-BMSe prepared in this example, the TEM image further illustrates the uniform distribution of the flower-shaped nanosheets. Example 2 ​​​

[0068] This embodiment 2 is a specific preparation process of the P@BN-BMSe powder described in the present application: first, 5 g of boron nitride and 1 g of melamine are placed in a high-energy ball mill, and ball-milled at a speed of 1400 rpm for 16 h to obtain modified boron nitride.

[0069] Take 1 g of modified boron nitride and disperse it in deionized water, ultrasonic for 4 h to obtain a uniform solution, then add 400 ml of citrate buffer solution, ultrasonic for 1 h, then take 0.2 g of dopamine hydrochloride and add it to the solution, magnetic stirring at room temperature for 6 h, after the reaction is completed, dry the product, wash it with deionized water until the pH is neutral, dry at 50°C, and collect the product P@BN.

[0070] Take 0.5 g of P@BN and disperse it in deionized water, add 1.6 g of cobalt nitrate and 1.6 g of nickel nitrate, continue to ultrasonic stirring for 1 h; at the same time, take 1.3 g of Se powder and place it in 10 ml of hydrazine solution, keep stirring for 1 h, add the Se solution to the P@BN solution, continue to ultrasonic stirring for 1 h; then hydrothermal reaction at 200 degrees for 24 h, after cooling and centrifugation, wash with deionized water for 3 times, ethanol for 2 times, and finally dry in a vacuum oven for 24 h to obtain P@BN-BMSe-2 powder. Figure 5 The transmission electron microscope image of the nano flame retardant P@BN-BMSe prepared in this embodiment. Embodiment 3:

[0071] This embodiment 3 is a specific preparation process of the P@BN-BMSe powder described in the present application: 5 g of boron nitride and 0.3 g of hexamethylenetetramine are placed in a high-energy ball mill, and ball-milled at a speed of 1200 rpm for 20 h to obtain modified boron nitride.

[0072] Take 1 g of modified boron nitride and disperse it in deionized water, ultrasonic for 4 h to obtain a uniform solution, then add 400 ml of glycine / hydrochloric acid buffer solution, ultrasonic for 1 h, then take 0.2 g of dopamine hydrochloride and add it to the solution, magnetic stirring at room temperature for 6 h, after the reaction is completed, dry the product, wash it with deionized water until the pH is neutral, dry at 60°C, and collect the product P@BN.

[0073] Take 0.5 g of P@BN and disperse it in deionized water, add 2.5 g of iron chloride and 2.5 g of copper nitrate, continue to ultrasonic stirring for 2 h; at the same time, take 2.5 g of Se powder and place it in 15 ml of hydrazine solution, keep stirring for 1 h, add the Se solution to the P@BN solution, continue to ultrasonic stirring for 1 h; then hydrothermal reaction at 200 degrees for 24 h, after cooling and centrifugation, wash with deionized water for 3 times, ethanol for 2 times, and finally dry in a vacuum oven for 24 h to obtain P@BN-BMSe-3 powder. Figure 6Transmission electron microscope image of the nano flame retardant P@BN-BMSe prepared in this example. Example 4:

[0074] The preparation method of the flame-retardant thermoplastic polyurethane composite material comprises the following steps: Step 1: 2g of P@BN-BMSe-1 prepared according to the method described in Example 1 is ultrasonically stirred and dispersed in 100ml of N,N-dimethylformamide (DMF) for 2 hours, and then 98g of TPU masterbatch is added and ultrasonically stirred for 4h to completely dissolve the polyurethane elastomer. Step 2: The solution obtained in Step 1 is slowly dropped into deionized water to obtain a precipitate, which is taken out and kneaded to remove water. Then it is dried in a 100℃ oven (72h). After that, the composite is pressed into a 100*100*3mm shape using a press machine to obtain a flame-retardant thermoplastic polyurethane composite material TPU / 2.0P@BN-BMSe-1 with an addition amount of 2%. Example 5:

[0075] 2g of P@BN-BMSe-2 prepared according to the method described in Example 2 is taken and a flame-retardant thermoplastic polyurethane composite material with an addition amount of 2% is prepared according to the same method as Example 4, which is denoted as TPU / 2.0P@BN-BMSe-2. Example 6:

[0076] 2g of P@BN-BMSe-3 prepared according to the method described in Example 3 is taken and a flame-retardant thermoplastic polyurethane composite material with an addition amount of 2% is prepared according to the same method as Example 4, which is denoted as TPU / 2.0P@BN-BMSe-3.

[0077] Test Example 1: Cone calorimeter test of commercially available TPU and flame-retardant TPU prepared in Examples 4, 5 and 6

[0078] The specific test process is as follows: according to the ISO 5660 standard, a cone calorimeter (UK, Fire Testing Technology) is used to test the combustion of the sample, and the sample is commercially available TPU and flame-retardant TPU prepared in Examples 4, 5 and 6, with a sample size of 100×100×3mm 3 , with electric spark ignition and a heat flux of 35 kW / m 2 , the heat release curve is calculated based on the oxygen consumption principle, and parameters such as smoke release rate and specific extinction area are monitored. Figure 7 The heat release rate curve is shown; Figure 8 The total heat release curve is shown; Figure 9 The smoke production rate curve is shown; Figure 10 The specific extinction area curve is shown.

[0079] It can be seen that the peak heat release rate, total heat release, peak flue gas release rate, and peak CO release rate of pure TPU are 1236.5 kW / m³. 2 87.1 MJ / m 2 0.159 m 2 / s and 0.0135g / s. After adding 2.0wt% flame retardant, the peak heat release rate and total heat release of TPU both decreased. Specifically, after adding P@BN-BMSe-2, the peak heat release rate and total heat release decreased by 51.9% and 33.4%, respectively. The peak smoke release rate and peak CO release rate decreased by 45.8% and 43.8%, respectively, indicating that P@BN-BMSe-2 can significantly inhibit the release of heat and toxic fumes during TPU combustion. The flame retardant effect of P@BN-BMSe-2 is better than that of P@BN-BMSe-1 and P@BN-BMSe-3. Excessive BMSe will enhance the catalytic degradation of particles and exacerbate polymer pyrolysis. Insufficient BMSe will weaken the catalytic char formation of particles, which is not conducive to the formation of a protective char layer.

[0080] Test Example 2: Thermogravimetric Infrared (TG-IR) Tests of Commercially Available TPU and Flame-Retardant TPU Prepared in Examples 4, 5, and 6

[0081] The specific testing process is as follows: The Nicolet 6700 FTIR spectrophotometer and TGA Q5000 thermogravimetric analyzer were used to obtain TGIR results. The test atmosphere was nitrogen and the heating rate was 20℃ / min. The sample mass of commercially available TPU and the flame-retardant TPU prepared in Examples 4, 5 and 6 were all about 10mg. After thermogravimetric and infrared spectroscopy were combined, the gaseous components decomposed during the thermal weight loss of the sample under programmed temperature control were transferred to the infrared gas detection cell through a constant temperature delivery tube. The escaped gases were qualitatively and quantitatively analyzed.

[0082] Figure 11 The test results for hydroxyl products show that after adding 2.0 wt% of P@BN-BMSe-1, P@BN-BMSe-2, and P@BN-BMSe-3 flame retardants, the peak absorbance decreased by 17.1%, 24.9%, and 24.3%, respectively.

[0083] Figure 12 The test results for ester products show that after adding 2.0 wt% of P@BN-BMSe-1, P@BN-BMSe-2, and P@BN-BMSe-3 flame retardants, the peak absorption values ​​decreased by 11.7%, 33.0%, and 19.1%, respectively.

[0084] Figure 13The test results of aromatic compounds show that, after adding 2.0wt% of P@BN-BMSe-1, P@BN-BMSe-2 and P@BN-BMSe-3 flame retardants, the peak absorbance is reduced by 32.7%, 45.1% and 33.9%, respectively.

[0085] Figure 14 The test results of ether compounds show that, after adding 2.0wt% of P@BN-BMSe-1, P@BN-BMSe-2 and P@BN-BMSe-3 flame retardants, the peak absorbance is reduced by 7.7%, 24.8% and 14.3%, respectively.

[0086] Figure 15 The test results of aromatic ether compounds show that, after adding 2.0wt% of P@BN-BMSe-1, P@BN-BMSe-2 and P@BN-BMSe-3 flame retardants, the peak absorbance is reduced by 19.3%, 48.1% and 31.8%, respectively.

[0087] Figure 16 The test results of hydrogen cyanide show that, after adding 2.0wt% of P@BN-BMSe-1, P@BN-BMSe-2 and P@BN-BMSe-3 flame retardants, the peak absorbance is reduced by 6.3%, 25.1% and 8.3%, respectively.

[0088] The above results show that, after using P@BN-BMSe, the generation of flammable gas and toxic gas is inhibited. Among them, P@BN-BMSe-2 has the best inhibitory effect.

[0089] Test Example 3: Mechanical tensile property test of commercially available TPU and flame-retardant TPU prepared in Examples 4, 5 and 6

[0090] The specific test process is as follows: the mechanical properties are tested and recorded by a universal tensile tester (CMT4204, China MTS System Co., Ltd.), and the samples are commercially available TPU and flame-retardant TPU prepared in Examples 4, 5 and 6. Each sample is tested for 5 samples and is prepared according to the national standard GB / T 1040. The tensile strength and elongation at break data are obtained.

[0091] As shown in Table 3, the tensile strength of the commercially available TPU is 18.5 MPa, and the tensile strength of the flame-retardant TPU prepared in Example 4 is 19.2 MPa, which is increased by 3.8%. The tensile strength of the flame-retardant TPU prepared in Example 5 is 19.3 MPa, which is increased by 4.3%. The tensile strength of the flame-retardant TPU prepared in Example 6 is 19.4 MPa, which is increased by 4.9%. Figure 17As shown, the flame-retardant TPU prepared in Examples 4, 5, and 6 did not reduce the tensile properties due to the addition of the flame retardant, and compared to the commercially available TPU, after the addition of 2.0wt% P@BN-BMSe-1, P@BN-BMSe-2, P@BN-BMSe-3 flame retardant, the tensile strength was increased from 31.2MPa to 35.4MPa, 42.1MPa, 38.2MPa, respectively, and the elongation at break was increased from 578.8% to 589.3%, 624.3%, 314.4%, respectively.

[0092] The unexplained parts involved in the present application are the same as or realized by using the prior art.

[0093] The above is only the preferred embodiment of the present application, and the present application is not limited to the content of the embodiment. For those skilled in the art, various changes and modifications can be made within the scope of the technical solutions of the present application, and any changes and modifications made are within the protection scope of the present application.

Claims

1. A method for preparing a bimetallic selenide / modified boron nitride nanoflame retardant, characterized in that, Includes the following steps: Step 1: Place the modified boron nitride in deionized water and sonicate to obtain a homogeneous dispersion 1; take a buffer solution and add it to dispersion 1, then weigh dopamine hydrochloride and add it to the mixture for reaction; after the reaction is completed, filter to obtain the product, then wash with deionized water until the pH is neutral, dry and collect to obtain P@BN; Step 2: Disperse P@BN in deionized water, then add mixed metal salts and ultrasonically stir to form dispersion II; simultaneously, place selenium powder in hydrazine hydrate solution and magnetically stir to dissolve it, forming selenium solution; add selenium solution to dispersion II, continue ultrasonic stirring, and then carry out hydrothermal reaction; collect the initial product after reaction by centrifugation, wash, and dry to obtain the final product, nano flame retardant P@BN-BMSe; In step 1, boron nitride and a modifier are placed in a high-energy ball mill for simultaneous exfoliation and modification to obtain modified boron nitride. The modifier is one or a mixture of urea, dicyandiamide, melamine, and hexamethylenetetramine. The metal salt is two of the following: sodium molybdate, calcium molybdate, zinc molybdate, cobalt sulfate, cobalt nitrate, cobalt acetate, cobalt chloride, nickel nitrate, nickel acetate, nickel chloride, ferric nitrate, ferric acetate, ferric chloride, copper nitrate, copper acetate, and copper chloride.

2. The preparation method of the bimetallic selenide / modified boron nitride nanoflame retardant according to claim 1, characterized in that, The boron nitride is one of hexagonal boron nitride, rhombohedral boron nitride, cubic boron nitride, or wurtzite boron nitride.

3. The method for preparing the bimetallic selenide / modified boron nitride nanoflame retardant according to any one of claims 1 and 2, characterized in that, In step 2, the mass ratio of P@BN to the mixed metal salt is (1:3) to (1:10), and the mixed metal salt is composed of two metal salts with a mass ratio of 1:

1.

4. The preparation method of the bimetallic selenide / modified boron nitride nanoflame retardant according to claim 3, characterized in that, In step 2, the ratio of P@BN, selenium powder and hydrazine hydrate is 1g:(1~5)g:(10-30)ml.

5. The preparation method of the bimetallic selenide / modified boron nitride nanoflame retardant according to claim 4, characterized in that, The buffer solution is one or more of the following: tris(hydroxymethyl)aminomethane / hydrochloric acid buffer solution, acetic acid / sodium acetate buffer solution, citrate buffer solution, phosphate buffer solution, glycine / hydrochloric acid buffer solution, and tartaric acid / sodium tartrate buffer solution.

6. The preparation method of the bimetallic selenide / modified boron nitride nanoflame retardant according to claim 5, characterized in that, In step 2, the initial product is washed three times with distilled water and twice with ethanol. After washing, the primary product was dried in a vacuum oven at 50-70 ℃ for 12-48 h to obtain the final product P@BN-BMSe powder.

7. A method for preparing flame-retardant thermoplastic polyurethane composite materials, characterized in that, The nano flame retardant P@BN-BMSe prepared based on any one of claims 1-6 specifically includes the following steps: Step 1: Place the nano flame retardant P@BN-BMSe in an organic solvent, stir ultrasonically for 2-8 h, then add thermoplastic polyurethane elastomer rubber, heat to 45-65 ℃, and keep stirring for 3-8 h to obtain a composite solution. Step 2: Add the composite solution to deionized water. After the composite material precipitates, dry it at 70-100 ℃ for 48-96 h, and then mix and press it at 180-190 ℃ to obtain the flame-retardant thermoplastic polyurethane composite material.

8. The method for preparing the flame-retardant thermoplastic polyurethane composite material according to claim 7, characterized in that, The amount of nano flame retardant P@BN-BMSe added is 2wt% of the total mass of the nano flame retardant P@BN-BMSe and the thermoplastic polyurethane elastomer rubber.

9. The method for preparing the flame-retardant thermoplastic polyurethane composite material according to claim 8, characterized in that, The organic solvent is one or more of tetrahydrofuran, acetone, N,N-dimethylformamide, N,N-dimethylacetamide, and 1,4-dioxane.

Images