Graphene modified flame-retardant polyurethane material and preparation method thereof

Abstract

The invention relates to the technical field of flame-retardant materials, and particularly discloses a graphene-modified flame-retardant polyurethane material and a preparation method thereof.The graphene-modified flame-retardant polyurethane material is prepared from, by weight, 60-70 parts of polyhydric alcohols, 30-40 parts of isophorone diisocyanate, 0.4-0.8 part of dibutyltin dilaurate, 3-6 parts of dimethylolpropionic acid, 15-20 parts of composite flame retardant, 2-4 parts of 1, 3-butanediol, 2-4 parts of 1, 3-butanediol, 2-4 parts of 1, 3-butanediol, 2-4 parts of 1, 3-butanediol, 2-4 parts of 1, 3-butanediol, 2 and 1 to 3 parts of 1, 4-butanediol and 1 to 3 parts of perfluorooctyltriethoxysilane. The preparation method comprises the following steps: 1) preparing castor oil-based polyester polyol through hydroxylation reaction and polycondensation; 2) taking graphene oxide as a core, grafting phosphorus and nitrogen flame-retardant groups and carrying out silane-titanate synergistic modification to prepare a composite flame retardant; 3, polyhydric alcohol and isocyanate are pre-polymerized, then the chain extender, the composite flame retardant and the auxiliaries are sequentially added, and curing molding.The material has low smoke and excellent flame retardance, mechanical property and hydrophobic stability through the synergistic effect of graphene and a phosphorus-nitrogen flame-retardant system, and is suitable for the field of flame-retardant high polymer materials for buildings, electronic packaging and the like.

Description

Technical Field

[0001] The present invention relates to the technical field of flame - retardant materials, and more specifically, it relates to a graphene - modified flame - retardant polyurethane material and a preparation method thereof. Background Art

[0002] Due to its excellent mechanical properties, processing adaptability, and adjustable chemical structure, polyurethane materials are widely used in fields such as construction, electronic packaging, and transportation. However, the traditional polyurethane molecular chain is rich in carbon - hydrogen structures, with a limiting oxygen index usually lower than 20%, high flammability, and a large amount of toxic smoke and gases released during combustion, seriously threatening life and property safety. In addition, polyurethane materials are prone to hydrolysis degradation in a humid environment, resulting in a decline in mechanical properties, which is particularly significant under high - temperature and high - humidity working conditions. Therefore, improving the flame - retardant performance, hydrolysis resistance, and reducing the combustion smoke toxicity of polyurethane materials have become urgent technical problems in this field.

[0003] Currently, flame - retardant polyurethanes are mainly achieved by adding flame retardants, but the traditional flame - retardant systems have significant limitations. Although halogen - based flame retardants have high flame - retardant efficiency, they release toxic substances such as hydrogen halide and dioxins during thermal decomposition and have been restricted by regulations such as EU RoHS. Inorganic flame retardants such as aluminum hydroxide and expanded graphite require high addition amounts to achieve the flame - retardant effect, resulting in deterioration of the mechanical properties of the material and a decrease in processing fluidity. The phosphorus - nitrogen intumescent flame - retardant system has relatively good environmental protection performance, but its interfacial compatibility with the matrix is poor, it is easy to migrate and precipitate, and its long - term stability is insufficient. In recent years, due to its two - dimensional sheet structure, high specific surface area, and thermal stability, graphene has been used to construct a physical - barrier - type flame - retardant system. However, the rich oxygen - containing groups on the surface of graphene oxide are prone to cause agglomeration, making it difficult to be evenly dispersed in the polyurethane matrix, and problems such as the directional loading efficiency of flame - retardant active groups and the stability of the carbon layer structure during combustion still need to be optimized through molecular design. Therefore, the present invention provides a graphene - modified flame - retardant polyurethane material and a preparation method thereof to solve the above - mentioned technical problems. Summary of the Invention

[0004] The purpose of the present invention is to provide a graphene - modified flame - retardant polyurethane material and a preparation method thereof. The flame - retardant polyurethane material prepared by the present invention has low smoke, excellent flame - retardant properties, mechanical properties, and hydrophobic stability through the synergistic effect of graphene and the phosphorus - nitrogen flame - retardant system, and is suitable for flame - retardant polymer material fields such as construction and electronic packaging.

[0005] To achieve the above purpose, the present invention provides the following technical solutions: A graphene-modified flame-retardant polyurethane material is composed of the following raw materials in parts by weight: 60 - 70 parts of polyol, 30 - 40 parts of isophorone diisocyanate, 0.4 - 0.8 parts of dibutyltin dilaurate, 3 - 6 parts of dimethylolpropionic acid, 15 - 20 parts of composite flame retardant, 2 - 4 parts of 1,4-butanediol, and 1 - 3 parts of perfluorooctyltriethoxysilane.

[0006] Preferably, the polyol is composed of polytetrahydrofuran ether diol and castor oil-based polyester polyol in a mass ratio of 6 - 9:1 - 4.

[0007] Preferably, the preparation method of the castor oil-based polyester polyol is as follows: Add castor oil, triethanolamine, and sodium methoxide into a reaction kettle, continuously stir at 105 - 115 °C for 2 - 4 h, then wash, extract, and dry to obtain hydroxylated castor oil. Then mix it with dibasic anhydride and tetrabutyl titanate, and continuously stir at 140 - 160 °C for 6 - 10 h, and then wash, extract, and dry to obtain castor oil-based polyester polyol.

[0008] Preferably, the method is 6 - 9 parts of castor oil, 1 - 4 parts of triethanolamine, and 0.4 - 0.8 parts of sodium methoxide by weight ratio.

[0009] Preferably, the dibasic anhydride is composed of maleic anhydride and phthalic anhydride in a molar ratio of 1:1 - 3.

[0010] Preferably, the method is 8 - 12 parts of hydroxylated castor oil, 3 - 6 parts of dibasic anhydride, and 0.3 - 0.8 parts of tetrabutyl titanate by weight ratio.

[0011] Preferably, the preparation steps of the composite flame retardant are as follows: S1. Disperse graphene oxide in deionized water, after ultrasonic treatment for 35 - 50 min, add polyethyleneimine, 9,10-dihydro-9-oxa-10-phosphaphenanthrene, and 2-amino-1,3,5-triazine. Under nitrogen protection, continuously stir at 80 - 90 °C for 6 - 9 h, and then centrifuge, wash to obtain the grafted product; S2. Disperse the grafted product in toluene, add octaaminopropyl polyhedral oligomeric silsesquioxane and titanate coupling agent, continuously stir at 115 - 125 °C for 10 - 14 h, and then filter, wash, and dry to obtain the composite flame retardant.

[0012] Preferably, in step S1, it is 1 - 5 parts of graphene oxide, 50 - 60 parts of deionized water, 2 - 4 parts of polyethyleneimine, 8 - 12 parts of 9,10-dihydro-9-oxa-10-phosphaphenanthrene, and 4 - 6 parts of 2-amino-1,3,5-triazine by weight.

[0013] Preferably, the titanate coupling agent in step S2 is at least one of triisostearoyl titanate isopropyl ester, triisostearic acid titanate isopropyl ester, and isopropyl tris(dioctylpyrophosphoryl) titanate.

[0014] Preferably, in step S2, by weight, it is 1 part of graft product, 5 - 8 parts of toluene, 0.5 - 0.9 part of octaaminopropyl polyhedral oligomeric silsesquioxane, and 0.02 - 0.05 part of titanate coupling agent.

[0015] A preparation method of a graphene - modified flame - retardant polyurethane material, comprising the following steps: adding polyol, isophorone diisocyanate, and dibutyltin dilaurate into a reaction kettle, stirring at 70 - 80 °C for 1 - 2 h to generate a prepolymer, adding dimethylolpropionic acid and 1,4 - butanediol thereto, continuing the reaction for 30 - 60 min, then adding a composite flame retardant and perfluorooctyltriethoxysilane, reacting at 60 - 70 °C for 1 - 2 h, pouring the mixed solution into a mold, and curing at 80 - 100 °C for 24 - 48 h to obtain the graphene - modified flame - retardant polyurethane material.

[0016] In summary, the present invention has the following beneficial effects: 1. The present invention uses graphene oxide as a carrier, constructs a dual - effect flame - retardant system by chemically grafting phosphorus - nitrogen flame - retardant groups and combining silane - titanate synergistic modification. The lamellar structure of graphene forms a continuous and dense physical barrier during the combustion process, effectively blocking heat and mass transfer and the diffusion of combustible gases; the phosphorus - nitrogen system promotes the rapid formation of an expanded carbon layer through catalytic char - forming and free - radical capture mechanisms, significantly improving the flame - retardant grade of the material and greatly reducing the release amount of combustion smoke and toxins. A compound system of polytetrahydrofuran ether diol and castor oil - based polyester polyol is used, and the molecular chain cross - linked network is regulated by polycondensation reaction, balancing the rigidity and toughness of the material while introducing renewable components. The interface modification of silane - titanate in the composite flame retardant and the introduction of perfluorooctyltriethoxysilane endow the material with excellent hydrophobicity and hydrolysis resistance stability, effectively inhibiting the breakage of molecular chains and performance attenuation in a humid environment, and expanding its application range in complex working conditions.

[0017] 2. The present invention realizes the high - density loading of phosphorus - nitrogen flame - retardant groups on the surface of graphene through a covalent grafting strategy mediated by polyethyleneimine, avoiding the component migration problem caused by traditional physical doping; the silane - titanate synergistic modification significantly improves the dispersion of graphene oxide in the polyurethane matrix, reduces the stress defects caused by nanoparticle agglomeration, and ensures the long - term stability of the mechanical properties of the material. Perfluorooctyltriethoxysilane enhances the surface hydrophobic function through chemical bonding, overcoming the defect of easy shedding of conventional coatings. The castor oil - based polyester polyol partially replaces petroleum - based raw materials, reducing the dependence on non - renewable resources, and the composite flame - retardant system abandons halogen components, meeting the requirements of environmental protection regulations. Detailed implementation manners

[0018] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0019] The experimental methods in the following examples are conventional methods unless otherwise specified, and the experimental materials used are purchased from conventional biochemical reagent stores unless otherwise specified. The quantitative tests in the following examples were repeated three times, and the data are the average or average ± standard deviation of the three repeated experiments.

[0020] Perfluorooctyltriethoxysilane was purchased from Shanghai Yuanye Biotechnology Co., Ltd., product number S25162; Polytetramethylenetetrahydrofuran ether glycol was purchased from Shandong Suihua Biotechnology Co., Ltd., catalog number 20210666321; Castor oil, purchased from Shanghai Yuanye Biotechnology Co., Ltd., product number S24344; Graphene oxide was purchased from Shanghai Keraman Reagent Co., Ltd., brand: Keraman; Polyethyleneimine, purchased from Shanghai Yihe Biotechnology Co., Ltd., CAS9002-98-6; 9,10-Dihydro-9-oxa-10-phosphaphenanthrene, purchased from Shanghai Yuanye Biotechnology Co., Ltd., catalog number S46419; Octaaminopropyl polysilsesquioxane was purchased from Xi'an Qiyue Biotechnology Co., Ltd., brand name Xi'an Qiyue Biotechnology; Isopropyl triisostearyl titanate was purchased from Shanghai Myrel Biochemical Technology Co., Ltd., CAS 61417-49-0. Example

[0021] A graphene-modified flame-retardant polyurethane material, comprising the following raw materials in parts by weight: 68 parts of polyol, 36 parts of isophorone diisocyanate, 0.8 parts of dibutyltin dilaurate, 5 parts of dimethylolpropionic acid, 20 parts of a composite flame retardant, 4 parts of 1,4-butanediol and 3 parts of perfluorooctyltriethoxysilane, wherein the polyol comprises polytetramethylene glycol and castor oil-based polyester polyol in a mass ratio of 8:3; The preparation method of castor oil-based polyester polyol is as follows: Add 8 parts of castor oil, 3 parts of triethanolamine and 0.8 part of sodium methoxide into a reaction kettle, control the stirring rate at 350 rpm, continuously stir at 115 °C for 2.5 h, then wash, extract and dry to obtain hydroxylated castor oil. Then, mix 12 parts of hydroxylated castor oil with 5 parts of dibasic anhydride and 0.6 part of tetrabutyl titanate, continuously stir at 155 °C for 8 h, and then wash, extract and dry to obtain castor oil-based polyester polyol, wherein the dibasic anhydride is composed of maleic anhydride and phthalic anhydride with a molar ratio of 1:3.

[0022] The preparation steps of the composite flame retardant are as follows: S1. Disperse 5 parts of graphene oxide in 60 parts of deionized water, ultrasonically treat at 60 KHz for 35 min, then add 4 parts of polyethyleneimine, 12 parts of 9,10-dihydro-9-oxa-10-phosphaphenanthrene and 6 parts of 2-amino-1,3,5-triazine. Under nitrogen protection, control the stirring rate at 400 rpm, continuously stir at 90 °C for 6 h, and then centrifuge, wash to obtain the grafted product; S2. Disperse 1 part of the grafted product in 7 parts of toluene, add 0.8 part of octaaminopropyl polyhedral oligomeric silsesquioxane and 0.04 part of triisostearoyl titanate isopropyl ester, continuously stir at 120 °C for 10 h, and then filter, wash and dry to obtain the composite flame retardant.

[0023] A preparation method of a graphene-modified flame-retardant polyurethane material includes the following steps: Weigh each raw material according to the formula amount, add polyol, isophorone diisocyanate and dibutyltin dilaurate into a reaction kettle, control the stirring rate at 400 rpm, stir at 80 °C for 1 h to generate a prepolymer, add dimethylolpropionic acid and 1,4-butanediol thereto, continue to react for 40 min, then add the composite flame retardant and perfluorooctyltriethoxysilane, react at 70 °C for 1.5 h, pour the mixed solution into a mold, and cure at 100 °C for 24 h to obtain the graphene-modified flame-retardant polyurethane material.

[0024] Example 2

[0025] A graphene-modified flame-retardant polyurethane material is composed of the following raw materials in parts by weight: 60 parts of polyol, 30 parts of isophorone diisocyanate, 0.4 part of dibutyltin dilaurate, 3 parts of dimethylolpropionic acid, 15 parts of composite flame retardant, 2 parts of 1,4-butanediol and 1 - 3 parts of perfluorooctyltriethoxysilane, wherein the polyol is composed of polytetrahydrofuran ether diol and castor oil-based polyester polyol with a mass ratio of 6:1; The preparation method of castor oil-based polyester polyol is as follows: Add 6 parts of castor oil, 1 part of triethanolamine and 0.4 part of sodium methoxide into a reaction kettle, control the stirring rate at 260 rpm, continuously stir at 105 °C for 4 h, then wash, extract and dry to obtain hydroxylated castor oil. Then, mix 8 parts of hydroxylated castor oil with 3 parts of dibasic anhydride and 0.3 part of tetrabutyl titanate, continuously stir at 140 °C for 10 h, and then wash, extract and dry to obtain castor oil-based polyester polyol, where the dibasic anhydride is composed of maleic anhydride and phthalic anhydride with a molar ratio of 1:1.

[0026] The preparation steps of the composite flame retardant are as follows: S1. Disperse 1 part of graphene oxide in 50 parts of deionized water, ultrasonically treat at 40 KHz for 50 min, then add 2 parts of polyethyleneimine, 8 parts of 9,10-dihydro-9-oxa-10-phosphaphenanthrene and 4 parts of 2-amino-1,3,5-triazine. Under nitrogen protection, control the stirring rate at 300 rpm, continuously stir at 80 °C for 9 h, and then centrifuge, wash to obtain the grafted product; S2. Disperse 1 part of the grafted product in 5 parts of toluene, add 0.5 part of octaaminopropyl polyhedral oligomeric silsesquioxane and 0.02 part of isopropyltri(dioctylpyrophosphato)titanate, continuously stir at 115 °C for 14 h, and then filter, wash and dry to obtain the composite flame retardant.

[0027] A preparation method of a graphene-modified flame-retardant polyurethane material includes the following steps: Weigh each raw material according to the formula amount, add polyol, isophorone diisocyanate and dibutyltin dilaurate into a reaction kettle, control the stirring rate at 300 rpm, stir at 70 °C for 2 h to generate a prepolymer, add dimethylolpropionic acid and 1,4-butanediol thereto, continue to react for 60 min, then add the composite flame retardant and perfluorooctyltriethoxysilane, react at 60 °C for 2 h, pour the mixed liquid into a mold, and cure at 80 °C for 48 h to obtain the graphene-modified flame-retardant polyurethane material.

[0028] Example 3

[0029] A graphene-modified flame-retardant polyurethane material is composed of the following raw materials in parts by weight: 63 parts of polyol, 35 parts of isophorone diisocyanate, 0.5 part of dibutyltin dilaurate, 5 parts of dimethylolpropionic acid, 16 parts of composite flame retardant, 3 parts of 1,4-butanediol and 2 parts of perfluorooctyltriethoxysilane, where the polyol is composed of polytetrahydrofuran ether diol and castor oil-based polyester polyol with a mass ratio of 7:2; The preparation method of castor oil-based polyester polyol is as follows: Add 8 parts of castor oil, 3 parts of triethanolamine and 0.5 part of sodium methoxide into a reaction kettle, control the stirring rate at 300 rpm, continuously stir at 110 °C for 3.5 h, then wash, extract and dry to obtain hydroxylated castor oil. Then mix 10 parts of hydroxylated castor oil with 5 parts of dianhydride and 0.4 part of tetrabutyl titanate, continuously stir at 150 °C for 9.5 h, and then wash, extract and dry to obtain castor oil-based polyester polyol, wherein the dianhydride is composed of maleic anhydride and phthalic anhydride with a molar ratio of 1:2.

[0030] The preparation steps of the composite flame retardant are as follows: S1. Disperse 4 parts of graphene oxide in 55 parts of deionized water, ultrasonically treat at 50 KHz for 45 min, then add 3 parts of polyethyleneimine, 11 parts of 9,10-dihydro-9-oxa-10-phosphaphenanthrene and 5 parts of 2-amino-1,3,5-triazine. Under nitrogen protection, control the stirring rate at 440 rpm, continuously stir at 85 °C for 8.5 h, and then centrifuge and wash to obtain the grafted product; S2. Disperse 1 part of the grafted product in 7 parts of toluene, add 0.7 part of octaaminopropyl polyhedral oligomeric silsesquioxane and 0.04 part of isopropyl triisostearoyl titanate, continuously stir at 120 °C for 13 h, and then wash and dry to obtain the composite flame retardant.

[0031] A preparation method of a graphene-modified flame-retardant polyurethane material includes the following steps: Weigh each raw material according to the formula amount, add polyol, isophorone diisocyanate and dibutyltin dilaurate into a reaction kettle, control the stirring rate at 350 rpm, stir at 75 °C for 1.8 h to generate a prepolymer, add dimethylolpropionic acid and 1,4-butanediol thereto, continue the reaction for 55 min, then add the composite flame retardant and perfluorooctyltriethoxysilane, react at 65 °C for 1.5 h, pour the mixed solution into a mold, and cure at 90 °C for 40 h to obtain the graphene-modified flame-retardant polyurethane material.

[0032] Example 4

[0033] A graphene-modified flame-retardant polyurethane material is composed of the following raw materials in parts by weight: 70 parts of polyol, 40 parts of isophorone diisocyanate, 0.8 part of dibutyltin dilaurate, 6 parts of dimethylolpropionic acid, 20 parts of composite flame retardant, 4 parts of 1,4-butanediol and 3 parts of perfluorooctyltriethoxysilane, wherein the polyol is composed of polytetrahydrofuran ether diol and castor oil-based polyester polyol with a mass ratio of 9:4; The preparation method of castor oil-based polyester polyol is as follows: Add 9 parts of castor oil, 4 parts of triethanolamine and 0.8 part of sodium methoxide into a reaction kettle, control the stirring rate at 350 rpm, continuously stir at 115 °C for 2 h, then wash, extract and dry to obtain hydroxylated castor oil. Then, mix 12 parts of hydroxylated castor oil with 6 parts of dibasic anhydride and 0.8 part of tetrabutyl titanate, continuously stir at 160 °C for 6 h, and then wash, extract and dry to obtain castor oil-based polyester polyol, where the dibasic anhydride is composed of maleic anhydride and phthalic anhydride with a molar ratio of 1:3.

[0034] The preparation steps of the composite flame retardant are as follows: S1. Disperse 5 parts of graphene oxide in 60 parts of deionized water, ultrasonically treat at 60 KHz for 35 min, then add 4 parts of polyethyleneimine, 12 parts of 9,10-dihydro-9-oxa-10-phosphaphenanthrene and 6 parts of 2-amino-1,3,5-triazine. Under nitrogen protection, control the stirring rate at 450 rpm, continuously stir at 90 °C for 6 h, and then centrifuge and wash to obtain the grafted product; S2. Disperse 1 part of the grafted product in 8 parts of toluene, add 0.9 part of isopropyl triisostearoyl titanate, continuously stir at 125 °C for 10 h, and then wash and dry to obtain the composite flame retardant.

[0035] The preparation method of a graphene-modified flame-retardant polyurethane material includes the following steps: Weigh each raw material according to the formula amount, add polyol, isophorone diisocyanate and dibutyltin dilaurate into a reaction kettle, control the stirring rate at 400 rpm, stir at 80 °C for 1 h to generate a prepolymer, add dimethylolpropionic acid and 1,4-butanediol thereto, continue the reaction for 30 min, then add the composite flame retardant and perfluorooctyltriethoxysilane, react at 70 °C for 1 h, pour the mixed solution into a mold, and cure at 100 °C for 24 h to obtain the graphene-modified flame-retardant polyurethane material.

[0036] A graphene-modified flame-retardant polyurethane material, which is different from Example 1 in that the composite flame retardant is not added, and the composition of the remaining raw materials and the preparation method are the same as those in Example 1.

[0037] A graphene-modified flame-retardant polyurethane material, which is different from Example 1 in that perfluorooctyltriethoxysilane is not added, and the composition of the remaining raw materials and the preparation method are the same as those in Example 1.

[0038] A graphene-modified flame-retardant polyurethane material, which is different from Example 1 in that the composite flame retardant is not subjected to silane-titanate synergistic modification, and the composition of the remaining raw materials and the preparation method are the same as those in Example 1.

[0039] A graphene-modified flame-retardant polyurethane material, which is different from that in Example 1 in that castor oil-based polyester polyol is not added to the polyol, and all poly-tetrahydrofuran ether glycol is used. The compositions of the remaining raw materials and the preparation method are the same as those in Example 1.

[0040] A graphene-modified flame-retardant polyurethane material, which is different from that in Example 1 in that the phosphorus-nitrogen flame-retardant group is not grafted to the composite flame retardant. The compositions of the remaining raw materials and the preparation method are the same as those in Example 1.

[0041] A graphene-modified flame-retardant polyurethane material, which is different from that in Example 1 in that graphene oxide is directly blended with other raw materials by physical blending method. The compositions of the remaining raw materials and the preparation method are the same as those in Example 1.

[0042] 1. Oxygen index test: The oxygen index test was carried out on the graphene-modified flame-retardant polyurethane materials prepared in Examples 1-4 and Comparative Examples 1-6 with reference to the standard of GB / T 2406.2-2009. The test results are shown in Table 1.

[0043] 2. Vertical burning rating test: The fire rating test (vertical burning, V-0 evaluation method of UL-94) was carried out on the graphene-modified flame-retardant polyurethane materials prepared in Examples 1-4 and Comparative Examples 1-6 with reference to the standard of GB / T2408-2021. The test results are shown in Table 1.

[0044] 3. Tensile strength test: The tensile strength test was carried out on the graphene-modified flame-retardant polyurethane materials prepared in Examples 1-4 and Comparative Examples 1-6 with reference to the standard of GB / T 528-2009. The test results are shown in Table 1.

[0045] 4. Hydrophobic property test: The contact angle test was carried out on the graphene-modified flame-retardant polyurethane materials prepared in Examples 1-4 and Comparative Examples 1-6 with reference to the standard of ASTM E662-17. The test results are shown in Table 1.

[0046] Table 1 Test Items Oxygen Index / % UL-94 Rating Tensile Strength / MPa Contact Angle / ° Example 1 35.5 V-0 48.6 128 Example 2 33.2 V-0 45.2 125 Example 3 34.8 V-0 47.3 126 Example 4 34.2 V-0 46.8 124 Comparative Example 1 23.0 Failed 28.5 85 Comparative Example 2 33.8 V-1 44.5 95 Comparative Example 3 29.5 V-1 38.9 102 Comparative Example 4 31.7 V-1 42.1 105 Comparative Example 5 28.5 V-2 36.4 92 Comparative Example 6 26.1 V-2 32.1 89 The oxygen indices of Examples 1-4 are all above 33%, and the UL-94 ratings are all V-0, indicating that through the synergistic effect of graphene and the phosphorus-nitrogen flame retardant system, the flame retardant performance of the polyurethane material can be significantly improved. In the comparative examples, the flame retardant performance of the materials without the addition of the composite flame retardant or without relevant modification is significantly reduced; the tensile strengths of Examples 1-4 are all above 45 MPa, showing good mechanical properties. In contrast, the tensile strengths of the materials in the comparative examples are relatively low, especially in the comparative examples without the addition of the composite flame retardant or without chemical modification, where the tensile strength drops significantly; the contact angles of Examples 1-4 are all above 124°, having good hydrophobic properties. In the comparative examples, the contact angles of the materials without the addition of perfluorooctyltriethoxysilane or without the synergistic modification of silane-titanate are significantly reduced, and the hydrophobic properties are poor. In summary, the comprehensive performance of the graphene-modified flame retardant polyurethane materials prepared in Examples 1-4 of the present invention is far superior to that of Comparative Examples 1-6.

[0047] The above content is only an example and illustration of the present invention. Those skilled in the art of this technology can make various modifications or supplements to the described specific embodiments or use similar methods for substitution, as long as they do not deviate from the invention or exceed the scope defined by this claim book, they should all fall within the protection scope of the present invention.

Claims

1. A graphene-modified flame-retardant polyurethane material, characterized in that: The invention is composed of the following raw materials in parts by weight: 60-70 parts of polyol, 30-40 parts of isophorone diisocyanate, 0.4-0.8 parts of dibutyltin dilaurate, 3-6 parts of dimethylolpropionic acid, 15-20 parts of composite flame retardant, 2-4 parts of 1,4-butanediol and 1-3 parts of perfluorooctyltriethoxysilane; The polyol is composed of polytetrahydrofuran ether diol and castor oil-based polyester polyol in a mass ratio of 6-9:1-4.

2. The graphene-modified flame-retardant polyurethane material according to claim 1, characterized in that: The preparation method of the castor oil-based polyester polyol is as follows: castor oil, triethanolamine and sodium methoxide are added into a reaction kettle, and the mixture is continuously stirred at 105-115° C. for 2-4 hours, and then washed, extracted and dried to obtain hydroxylated castor oil; the mixture is then mixed with dibasic acid anhydride and tetrabutyl titanate, and then continuously stirred at 140-160° C. for 6-10 hours, and then washed, extracted and dried to obtain castor oil-based polyester polyol.

3. A graphene-modified flame-retardant polyurethane material according to claim 2, characterized in that: The method comprises 6-9 parts of castor oil, 1-4 parts of triethanolamine and 0.4-0.8 parts of sodium methoxide in weight ratio.

4. The graphene-modified flame-retardant polyurethane material according to claim 2, characterized in that: The dibasic acid anhydride is composed of maleic anhydride and phthalic anhydride in a molar ratio of 1:1-3.

5. The graphene-modified flame-retardant polyurethane material according to claim 2, characterized in that: The method comprises 8-12 parts of hydroxylated castor oil, 3-6 parts of dibasic acid anhydride and 0.3-0.8 parts of tetrabutyl titanate in weight ratio.

6. The graphene-modified flame-retardant polyurethane material according to claim 1, characterized in that: The preparation steps of the composite flame retardant are: S1. Disperse graphene oxide in deionized water, ultrasonically treat for 35-50 min, add polyethyleneimine, 9,10-dihydro-9-oxa-10-phosphaphenanthrene and 2-amino-1,3,5-triazine, and stir continuously at 80-90° C. for 6-9 h under nitrogen protection, then centrifuge and wash to obtain a grafted product; S2. Disperse the grafted product in toluene, add octaaminopropyl polysilsesquioxane and titanate coupling agent, stir continuously at 115-125° C. for 10-14 hours, filter, wash and dry to obtain a composite flame retardant.

7. The graphene-modified flame-retardant polyurethane material according to claim 6, characterized in that: In the step S1, the components by weight include 1-5 parts of graphene oxide, 50-60 parts of deionized water, 2-4 parts of polyethyleneimine, 8-12 parts of 9,10-dihydro-9-oxa-10-phosphaphenanthrene and 4-6 parts of 2-amino-1,3,5-triazine.

8. The graphene-modified flame-retardant polyurethane material according to claim 6, characterized in that: In the step S2, the titanate coupling agent is at least one of triisostearoyl isopropyl titanate, triisostearoyl isopropyl titanate and isopropyl tri(dioctyl pyrophosphoryl) titanate.

9. The graphene-modified flame-retardant polyurethane material according to claim 6, characterized in that: In the step S2, the components by weight include 1 part of the grafted product, 5-8 parts of toluene, 0.5-0.9 parts of octaaminopropyl polysilsesquioxane and 0.02-0.05 parts of a titanate coupling agent.

10. A method for preparing a graphene-modified flame-retardant polyurethane material according to any one of claims 1 to 9, characterized in that: The method comprises the following steps: adding polyol, isophorone diisocyanate and dibutyltin dilaurate into a reaction kettle, stirring at 70-80°C for 1-2 hours to generate a prepolymer, adding dimethylolpropionic acid and 1,4-butanediol thereto, continuing the reaction for 30-60 minutes, adding a composite flame retardant and perfluorooctyltriethoxysilane, reacting at 60-70°C for 1-2 hours, pouring the mixed solution into a mold, and curing at 80-100°C for 24-48 hours to obtain a graphene-modified flame-retardant polyurethane material.