Flame-retardant polyurea coating, and preparation method and application thereof

Abstract

The application provides a kind of flame-retardant polyurea coating and its preparation method and application, it relates to high polymer material technical field.The flame-retardant polyurea coating includes the following components by weight: A component includes 350~450 parts of polyether amine, 80~120 parts of terminal amine chain extender, 5~20 parts of two-dimensional transition metal carbide grafted with flame retardant on the surface, 50~150 parts of boron nitride nanosheet modified by silane coupling agent, 50~100 parts of solvent;The flake diameter of two-dimensional transition metal carbide is d1 mu m, the flake diameter of boron nitride nanosheet is d2 mu m, and d1 < d2 is satisfied;B component includes isocyanate prepolymer.The application constructs 3D network in polyurea matrix through the synergistic effect of "two-dimensional transition metal carbide grafted with flame retardant on the surface + boron nitride nanosheet modified by silane coupling agent", and overcomes the core problem that heat conduction, insulation and flame retardant cannot be considered together.

Description

Technical Field

[0001] This invention relates to the field of polymer materials technology, and in particular to a flame-retardant polyurea coating, its preparation method, and its application. Background Technology

[0002] Polyurea is a high-performance elastomer formed by the rapid reaction polymerization of an isocyanate component (component B) and an amino compound component (component A). The urea bonds (-NH-CO-NH-) in its molecular structure endow the material with extremely high reactivity (allowing for instant drying after spraying), excellent mechanical properties (high strength, high elongation), outstanding resistance to various media (acids, alkalis, salt spray), and weather resistance. Therefore, polyurea is widely used in protective coatings, waterproofing projects, military equipment, and infrastructure.

[0003] However, with the rapid development of new energy vehicles, 5G communication base stations, and advanced electronic packaging, extreme requirements have been placed on the comprehensive performance of protective materials, and the shortcomings of traditional polyurea materials are becoming increasingly prominent: (1) Traditional polyurea has extremely low thermal conductivity (approximately 0.2 W / m·K). When used as a thermal interface material or for packaging shells of electronic devices, it cannot dissipate the heat generated by internal components such as chips and batteries in a timely manner, leading to heat accumulation and seriously affecting the stability and service life of the equipment. (2) To solve the thermal conductivity problem, high thermal conductivity fillers such as graphene, carbon nanotubes, or two-dimensional transition metal carbides (MXene) are usually added. However, these thermally conductive materials are all electrical conductors. Their addition will cause the volume resistivity of the polyurea composite material to drop sharply, resulting in insulation failure and making it unsuitable for insulation protection of high-voltage or precision electronic equipment. (3) In addition, polyurea is an organic polymer material that is flammable and has a low limiting oxygen index (LOI). When burning, it releases a large amount of heat and toxic fumes (such as HCN). Under conditions of battery thermal runaway or external fire source, the polyurea protective layer is easily ignited, leading to the spread of fire and causing serious safety accidents.

[0004] Therefore, there is a dilemma: high thermal conductivity and high electrical insulation are mutually exclusive. In existing modified systems, high thermal conductivity and high electrical insulation properties are severely conflicting. High thermal conductivity MXene is an electrical conductor, which can lead to insulation failure; while the thermal conductivity of highly insulating nano-boron nitride (BNN) is limited by high interfacial thermal resistance and high filler content. How to construct an efficient three-dimensional thermally conductive network in a polyurea matrix while ensuring the overall electrical insulation of this network is the most critical bottleneck in this field.

[0005] In view of this, the present invention is proposed, which provides a polyurea material that has excellent flame retardant properties, high thermal conductivity and high insulation properties. Summary of the Invention

[0006] The purpose of this invention is to provide a polyurea material that combines excellent flame retardant properties, high thermal conductivity, and high insulation properties, addressing the aforementioned deficiencies in the prior art.

[0007] To achieve the above objectives, the present invention adopts the following technical solution: A first aspect of the present invention provides a flame-retardant polyurea coating comprising the following components in parts by weight: Component A: 350-450 parts polyetheramine, 80-120 parts terminal amine chain extender, 5-20 parts two-dimensional transition metal carbides with flame retardant grafted on the surface, 50-150 parts silane coupling agent modified boron nitride nanosheets, and 50-100 parts solvent. Wherein, the sheet diameter of the two-dimensional transition metal carbide is d1μm, and the sheet diameter of the boron nitride nanosheet is d2μm, satisfying: d1<d2; Component B: Isocyanate prepolymer.

[0008] As an embodiment of the present invention, in the two-dimensional transition metal carbide with flame retardant grafted on the surface, the weight ratio of flame retardant to two-dimensional transition metal carbide is (10~30):100.

[0009] As an embodiment of the present invention, the flame retardant includes a DOPO type flame retardant, which includes at least one of DOPO-Cl and DOPO-OH.

[0010] As an embodiment of the present invention, the two-dimensional transition metal carbide includes at least one compound having the following chemical formula: Ti3C2T x V2CT x Ti2CT x T x The functional groups representing the surface of the two-dimensional transition metal carbide include at least one of -OH and -F.

[0011] As an embodiment of the present invention, the sheet diameter d1μm of the two-dimensional transition metal carbide is 0.2~1μm, and the sheet thickness is 1~5nm.

[0012] As an embodiment of the present invention, the boron nitride nanosheets have a sheet diameter d2μm = 1~5μm and a sheet thickness of 10~50nm.

[0013] As an embodiment of the present invention, in the silane coupling agent modified boron nitride nanosheets, the weight of the silane coupling agent accounts for 2 to 5% of the weight of the boron nitride nanosheets.

[0014] As an embodiment of the present invention, the silane coupling agent includes at least one of KH550 and KH560.

[0015] As an embodiment of the present invention, the weight-average molecular weight of the polyetheramine is 400-2000.

[0016] As an embodiment of the present invention, the terminal amine chain extender includes at least one of diethyltoluenediamine, 4,4′-diaminodiphenylmethane (MDA), 1,4-butanediamine, and 1,6-hexanediamine.

[0017] As an embodiment of the present invention, the isocyanate prepolymer includes at least one of MDI prepolymer, IPDI prepolymer, HMDI prepolymer, and TDI prepolymer.

[0018] As an embodiment of the present invention, the viscosity of the isocyanate prepolymer at 25°C is 2000~8000 cps.

[0019] A second aspect of the present invention provides a method for preparing the flame-retardant polyurea coating described in the first aspect of the present invention, comprising the following steps: (1) Raw material pretreatment After etching and stripping, the two-dimensional transition metal carbide is dissolved in a non-aqueous solvent, a flame retardant is added, and a grafting reaction is carried out in a catalyst and an inert atmosphere to obtain a two-dimensional transition metal carbide with a flame retardant grafted on its surface. Silane coupling agent and boron nitride nanosheets were dispersed in a hydrophilic solvent and stirred at 50-70℃ for 3-6 h to obtain silane coupling agent modified boron nitride nanosheets. (2) Preparation of component A According to the weight ratio, polyetheramine, two-dimensional transition metal carbides with flame retardant grafted on the surface, and boron nitride nanosheets modified with silane coupling agent were dispersed in a solvent and sheared to obtain a dispersion. Add a terminal amine chain extender to the dispersion, stir, and obtain component A; (3) Preparation of component B The monomers of the isocyanate prepolymer undergo a copolymerization reaction to obtain the isocyanate prepolymer.

[0020] A third aspect of the present invention provides the application of the flame-retardant polyurea coating described in the first aspect of the present invention, wherein the flame-retardant polyurea coating is used to prepare a protective coating.

[0021] As an embodiment of the present invention, the method for preparing the protective coating includes the following steps: After mixing components A and B, the mixture is heat-cured at 25~80℃ for 0.5~2h and dried to obtain the protective coating; wherein the molar ratio of amine groups in component A to isocyanate groups in component B is 1.05~1.1.

[0022] Compared with the prior art, the beneficial effects of the present invention are: This invention overcomes the core problem of the inability to simultaneously achieve thermal conductivity, insulation, and flame retardancy by constructing a 3D network in a polyurea matrix through the synergistic effect of "two-dimensional transition metal carbides with flame retardants grafted on their surfaces + boron nitride nanosheets modified with silane coupling agents". Attached Figure Description

[0023] Figure 1 This is a SEM image of the flame-retardant polyurea material of Example 1 of the present invention. Detailed Implementation

[0024] To better illustrate the purpose, technical solution, and advantages of this invention, the invention will be further described below with reference to specific embodiments and accompanying drawings. However, the embodiments do not limit the invention in any way. Unless otherwise specified, the reagents, methods, and equipment used in this invention are conventional reagents, methods, and equipment in this technical field. Unless otherwise specified, all reagents and materials used in this invention are commercially available.

[0025] In this invention, the technical features described in an open-ended manner include both closed-ended technical solutions composed of the listed features and open-ended technical solutions that include the listed features.

[0026] In this invention, numerical ranges are involved. Unless otherwise specified, the numerical ranges are considered continuous and include the minimum and maximum values ​​of the range, as well as every value between the minimum and maximum values. Furthermore, when the range refers to integers, it includes every integer between the minimum and maximum values ​​of the range. Additionally, when multiple ranges are provided to describe features or characteristics, the ranges may be merged. In other words, unless otherwise specified, all ranges disclosed herein should be understood to include any and all subranges to which they are included.

[0027] Unless otherwise specified, all reagents or instruments used in this invention are commercially available products.

[0028] A first aspect of the present invention provides a flame-retardant polyurea coating comprising the following components in parts by weight: Component A: 350-450 parts polyetheramine, 80-120 parts terminal amine chain extender, 5-20 parts two-dimensional transition metal carbides with flame retardant grafted on the surface, 50-150 parts silane coupling agent modified boron nitride nanosheets, and 50-100 parts solvent. Wherein, the sheet diameter of the two-dimensional transition metal carbide is d1μm, and the sheet diameter of the boron nitride nanosheet is d2μm, satisfying: d1<d2; Component B: Isocyanate prepolymer.

[0029] In coatings, the amine groups in component A and the isocyanate groups in component B react to form urea groups, resulting in polyurea materials. Adding functional fillers can improve the performance of polyurea materials. Adding flame retardants enhances the flame retardancy of polyurea, while adding thermally conductive and insulating fillers improves its thermal conductivity and insulation properties. For example, two-dimensional transition metal carbides (MXene) are excellent thermally conductive fillers, and nano-boron nitride (BNN) has excellent insulation properties. However, the thermally conductive filler MXene has poor insulation properties. To compensate for the decrease in insulation performance caused by MXene, a large amount of insulating filler BNN needs to be added. Inorganic fillers have poor compatibility with the polyurea matrix, and the interfacial thermal resistance is significantly increased. In order to reduce the impact of the interfacial difference between "inorganic filler-organic polyurea" on flame retardancy and insulation performance, two-dimensional MXene and boron nitride nanosheets (abbreviated as BNNS) are selected. By utilizing their layered structure, a thermally conductive and insulating network can be constructed in the polyurea matrix, further improving the thermal conductivity and insulation performance of polyurea. However, the large-scale addition of the above-mentioned two-dimensional thermally conductive and insulating fillers will lead to a sharp increase in the viscosity of the coating, resulting in uneven dispersion and agglomeration of the fillers in the coating, thus failing to improve the thermal conductivity and insulation performance. It will also lead to a decrease in the mechanical properties of the cured polyurea material. In addition, it is difficult to achieve spraying or high-precision potting, increasing the processing difficulty and limiting its application.

[0030] This invention, through specific screening and matching of the morphology and particle size of flame retardants, thermally conductive fillers, and insulating fillers, can construct a three-dimensional synergistic network of "BNNS (insulating and thermally conductive) - MXene (bridging and thermally conductive) - flame retardant / interface modification" in a polyurea matrix, fundamentally solving the conflict between thermal conductivity, insulation, and flame retardancy. Specifically: (1) grafting flame retardants onto MXene can make MXene inherently flame retardant, and the flame retardant can also act as an "isolation barrier," inhibiting the electrical conductivity of MXene to a certain extent; (2) in coatings, high filler content BNNS forms the "skeleton" of the thermally conductive network. By using a combination of smaller-diameter MXene and larger-diameter BNNS, smaller-diameter MXene with flame retardant grafted on its surface can fill the gaps in the BNNS "skeleton". The highly thermally conductive MXene acts as a "bridge" to connect the BNNS. The BNNS plays an "insulating and blocking" role in the thermally conductive network. Heat (phonons) can be efficiently transferred through the "BNNS-MXene-BNNS" path, while electrons cannot jump, thus realizing an insulating thermally conductive network that allows phonons to pass but blocks electrons.

[0031] In some embodiments of the present invention, the two-dimensional transition metal carbide (abbreviated as MXene) comprises at least one compound having the following chemical formula: Ti3C2T x V2CT x Ti2CT x Tx The functional groups on the surface of the two-dimensional transition metal carbide include at least one of -OH and -F. The functional groups on the MXene surface can undergo chemical grafting reactions with the active functional groups in the flame retardant, thereby grafting the flame retardant onto the MXene surface.

[0032] In some embodiments of the present invention, the two-dimensional transition metal carbide (abbreviated as MXene) has a sheet diameter d1μm=0.2~1μm and a sheet thickness of 1~5nm.

[0033] In some embodiments of the present invention, the flame retardant is selected as an organic flame retardant, specifically including a DOPO type flame retardant, which is "9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide or its derivatives", and the DOPO type flame retardant includes at least one of DOPO-Cl and DOPO-OH. DOPO (9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide), as a traditional organic flame retardant, can improve the interfacial compatibility between MXene and the polyurea matrix. Its flame retardant properties mainly play a role in the early stage of combustion in the gas phase or condensed phase. It has a negligible effect on improving the thermal conductivity of polyurea materials. However, when DOPO is grafted onto the surface of MXene (abbreviated as D-MXene) and embedded into the gaps in the skeleton of BNNS along with MXene, on the one hand, DOPO acts as an "isolation barrier" and inhibits the electrical conductivity of MXene to a certain extent; on the other hand, it also allows the flame retardant DOPO to participate in the construction of the thermally conductive network or char-forming network, achieving "multi-functionality" and improving the comprehensive performance of polyurea materials in terms of flame retardancy, thermal conductivity, and insulation.

[0034] In some embodiments of the present invention, the weight ratio of the flame retardant to the two-dimensional transition metal carbide (abbreviated as D-MXene in the present invention) grafted with flame retardant is (10~30):100.

[0035] In some embodiments of the present invention, the boron nitride nanosheets (abbreviated as BNNS) have a sheet diameter d2μm=1~5μm and a sheet thickness of 10~50nm.

[0036] In some embodiments of the present invention, the silane coupling agent accounts for 2-5% of the weight of the boron nitride nanosheets modified with the silane coupling agent. Modifying the boron nitride nanosheets with a silane coupling agent can improve the interfacial compatibility between the boron nitride nanosheets and the polyurea matrix, further enhancing the insulation and mechanical properties of the polyurea material.

[0037] In some embodiments of the present invention, the performance of the silane coupling agent is not particularly limited, as long as it can improve the compatibility between BNNS and the polyurea matrix. Silane coupling agents used in the art to improve the compatibility of organic-inorganic interfaces can be used in the present invention to modify boron nitride nanosheets (BNNS). The silane coupling agent includes, but is not limited to, at least one of KH550 (γ-aminopropyltrimethoxysilane) and KH560 (γ-glycidoxypropyltrimethoxysilane).

[0038] In some embodiments of the present invention, the weight-average molecular weight of the polyetheramine is 400-2000. By controlling the molecular weight of the polyetheramine, polyurea materials with different mechanical properties, especially flexibility, can be prepared. To prepare a highly flexible polyurea material, the polyetheramine can be a mixture of a first polyetheramine with a lower molecular weight (D1) and a second polyetheramine with a higher molecular weight (D2), where D1 < D2, and the weight ratio of the first polyetheramine to the second polyetheramine is (1-4):1.

[0039] In some embodiments of the present invention, the terminal amine chain extender includes at least one of diethyltoluene diamine (DETDA), 4,4′-diaminodiphenylmethane (MDA), 1,4-butanediamine, and 1,6-hexanediamine.

[0040] In some embodiments of the present invention, the isocyanate prepolymer includes at least one of MDI prepolymer, IPDI prepolymer, HMDI prepolymer, and TDI prepolymer. The monomer corresponding to the MDI prepolymer is diphenylmethane diisocyanate (MDI), the monomer corresponding to the IPDI prepolymer is isophorone diisocyanate (IPDI), the monomer corresponding to the HMDI prepolymer is dicyclohexylmethane diisocyanate (HMDI), and the monomer corresponding to the TDI prepolymer is toluene diisocyanate (TDI).

[0041] In some embodiments of the present invention, the viscosity of the isocyanate prepolymer at 25°C is 2000~8000 cps. This viscosity range is beneficial for mixing or spraying the coating, facilitating rapid, uniform mixing, crosslinking, and curing.

[0042] It should be noted that the present invention does not specifically limit the type of polyurea matrix for polyurea materials. The mechanical properties of polyurea matrices prepared by using different polyetheramines and isocyanate prepolymers will vary, but they can all be used in the present invention. The fillers of the present invention (especially two-dimensional transition metal carbides with flame retardants grafted on their surfaces and boron nitride nanosheets modified with silane coupling agents) can improve the performance of common polyurea matrix materials in the art. They can improve the flame retardant properties, insulation properties, and thermal conductivity of polyurea matrix without reducing its mechanical properties.

[0043] In some embodiments of the present invention, the solvent in component A is not particularly limited. The solvent will evaporate during the process of mixing and curing components A and B into a polyurea coating. Therefore, the solvent only needs to be able to dissolve or disperse the raw material components in component A. The solvent includes, but is not limited to, at least one solvent selected from N-methylpyrrolidone (NMP), N,N-dimethylformamide (DMF), and N,N-dimethylacetamide (DMAc).

[0044] A second aspect of the present invention provides a method for preparing the flame-retardant polyurea coating described in the first aspect of the present invention, comprising the following steps: (1) Raw material pretreatment After etching and stripping, the two-dimensional transition metal carbide is dissolved in a non-aqueous solvent, a flame retardant is added, and a grafting reaction is carried out in a catalyst and an inert atmosphere to obtain a two-dimensional transition metal carbide with a flame retardant grafted on its surface. Silane coupling agent and boron nitride nanosheets were dispersed in a hydrophilic solvent and stirred at 50-70℃ for 3-6 h to obtain silane coupling agent modified boron nitride nanosheets. (2) Preparation of component A According to the weight ratio, polyetheramine, two-dimensional transition metal carbides with flame retardant grafted on the surface, and boron nitride nanosheets modified with silane coupling agent were dispersed in a solvent and sheared to obtain a dispersion. Add a terminal amine chain extender to the dispersion, stir, and obtain component A; (3) Preparation of component B The monomers of the isocyanate prepolymer undergo a copolymerization reaction to obtain the isocyanate prepolymer.

[0045] In some embodiments of the present invention, the temperature of the grafting reaction in step (1) is 60~100°C and the time is 10~15h.

[0046] In some embodiments of the present invention, the non-aqueous solvent described in step (1) is not specifically limited. Common non-aqueous solvents in the art that can be used to dissolve or disperse two-dimensional transition metal carbides and flame retardants can be used in the present invention. The non-aqueous solvents specifically include, but are not limited to, at least one of N,N-dimethylformamide (DMF) and N,N-dimethylacetamide (DMA).

[0047] In some embodiments of the present invention, the catalyst described in step (1) includes, but is not limited to, at least one of triethylamine, diethylamine, and pyridine. The amount of catalyst used is 0.5 to 5% of the total mass of the flame retardant and the two-dimensional transition metal carbide.

[0048] In some embodiments of the present invention, the inert atmosphere described in step (1) includes at least one gas selected from nitrogen, helium, and argon.

[0049] In some embodiments of the present invention, the hydrophilic solvent mentioned in step (1) includes, but is not limited to, an alcohol-water mixed solvent, wherein the volume ratio of the alcohol compound to water is (8~10):1. The alcohol compound is preferably ethanol.

[0050] In some embodiments of the present invention, the specific process of shear dispersion in step (2) is as follows: using a high-speed shear disperser to shear at a speed of 1000~5000 r / min for 1~3h, and then intermittently treating in a 40kHz, 500W ultrasonic cell disruptor for 30min (working for 5s, stopping for 5s) to obtain a dispersion with no agglomeration and high viscosity.

[0051] In some embodiments of the present invention, the stirring speed in step (2) is 250~350 r / min and the stirring time is 15~30 min.

[0052] In some embodiments of the present invention, the copolymerization reaction of the isocyanate prepolymer in step (3) can be prepared using common copolymerization reactions in the art, as long as polymerization can be carried out. The isocyanate prepolymer is obtained by condensation copolymerization of isocyanate monomers and polyols. Among them, the polymerizing monomers corresponding to the MDI prepolymer are diphenylmethane diisocyanate (MDI) and polyol, the polymerizing monomers corresponding to the IPDI prepolymer are isophorone diisocyanate (IPDI) and polyol, the polymerizing monomers corresponding to the HMDI prepolymer are dicyclohexylmethane diisocyanate (HMDI) and polyol, and the polymerizing monomers corresponding to the TDI prepolymer are toluene diisocyanate (TDI) and polyol.

[0053] In a third aspect, the present invention provides the application of the flame-retardant polyurea coating described in the first aspect of the present invention, wherein the flame-retardant polyurea coating is used to prepare a protective coating, specifically for: (1) protection of the outer shell of a new energy vehicle battery pack: as a sprayed protective layer (thickness 2~3mm) on the lower protective plate of the battery pack (PACK), providing impact resistance, waterproofing, flame retardancy (preventing thermal runaway propagation) and insulation performance; (2) thermal management of power batteries: prepared as a thermally conductive insulating pad, used between the battery cell and the liquid cooling plate (operating temperature -40~120℃), with a thermal conductivity >1.0 W / m·K and a volume resistivity >10 13 Ω·cm, effectively transfers heat while ensuring electrical insulation between cells; (3) 5G base station and high voltage equipment encapsulation: used for potting or shell protection of high voltage inverters and 5G base station antennas (AAU) to prevent equipment overheating and eliminate electrical faults caused by moisture and electric arc.

[0054] In some embodiments of the present invention, the method for preparing the protective coating includes the following steps: After mixing components A and B, the mixture is heat-cured at 25~80℃ for 0.5~2h and dried to obtain the protective coating; wherein the molar ratio of amine groups in component A to isocyanate groups in component B (i.e., isocyanate index R) is 1.05~1.1.

[0055] The following are specific embodiments of the present invention.

[0056] The following is some information about the raw materials used in the embodiments and comparative examples of the present invention. It should be noted that, unless otherwise specified, all reagents and materials used in the present invention are commercially available.

[0057] Table 1 Composition information of D-MXene Note: In Table 1, the grafting rate of the flame retardant for D-MXene is "the percentage of the mass of the flame retardant relative to the mass of MXene".

[0058] The D-MXene in Table 1 was prepared according to the following steps: Two-dimensional transition metal carbides MXene (see Table 1) were etched and peeled off, then dissolved in DMF to prepare a dispersion with a flame retardant concentration of 10 wt%. Then, flame retardant (see Table 1) was added, and under the protection of nitrogen and the catalyst triethylamine (added at 1 wt% of the total mass of flame retardant and two-dimensional transition metal carbides), the grafting reaction was carried out at 80°C for 12 h with stirring to obtain two-dimensional transition metal carbides with flame retardant grafted on the surface, denoted as D-MXene.

[0059] Fourier transform infrared spectroscopy (FTIR) confirmed that D-MXene, compared to the original MXene, showed differences at 1200 cm⁻¹. -1 (P=O stretching vibration) and 920 cm -1 The characteristic peak of DOPO appears at (PO-Ph stretching vibration), and at 550 cm⁻¹. -1 The formation of PO-Ti bonds can be observed nearby, proving that the DOPO-type flame retardant was successfully grafted. X-ray photoelectron spectroscopy (XPS) analysis showed that the P 2p spectrum had a peak around 133.5 eV, which was attributed to the PO-Ti bond, further confirming the chemical grafting.

[0060] Table 2. Silane Coupling Agent Modified BNNS Note: In Table 2, the grafting rate of the silane coupling agent in the silane coupling agent modified BNNS is "the percentage of the mass of the silane coupling agent to the mass of BNNS".

[0061] The silane coupling agent-modified BNNS in Table 2 was prepared according to the following steps: Silane coupling agent (see Table 2) and boron nitride nanosheets (see Table 2) were dispersed in a hydrophilic solvent (ethanol and water volume ratio of 9:1) to prepare a dispersion of boron nitride nanosheets with a mass concentration of 25 wt%. The dispersion was stirred at 60 °C for 4 h to obtain silane coupling agent modified boron nitride nanosheets, denoted as BNNS-NH2 or BNNS-Ep.

[0062] Table 3 Isocyanate prepolymers The isocyanate prepolymers in Table 3 were prepared according to the following steps: (1) At 100°C and under stirring conditions, dehydrated polyols were added dropwise to a compound solvent containing isocyanate monomers for 2.5 h. After the addition, the reaction was continued by stirring. The lower layer was a highly free isocyanate prepolymer. The compound solvent is obtained by mixing ethyl acetate and hexane in a 1:1 molar ratio; The dehydrated polyol is a polycaprolactone diol with a molecular weight of 500 g / mol; (2) Collect the upper layer solution from step (1), and distill the upper layer solution at 85°C to obtain the first compound solvent and isocyanate monomer; (3) At 60°C, the lower precipitate product of step (1) – high free isocyanate prepolymer – is injected into the tower from the top of the extraction tower, and the compound solvent obtained in step (2) is injected into the tower from the bottom of the extraction tower. The mixture is stirred and mixed, and the extract is removed to obtain a mixture. The mixture is then distilled and separated to obtain low free isocyanate prepolymer and a second compound solvent. The low free isocyanate prepolymer is used as component B in the preparation of flame-retardant polyurea coatings in this invention.

[0063] By replacing the type of isocyanate monomer in step (1), the corresponding type of isocyanate prepolymer in Table 3 can be obtained; by adjusting the stirring reaction time in step (1), the viscosity of the prepared isocyanate prepolymer can be controlled. The viscosity of the isocyanate prepolymer is detailed in Table 3.

[0064] Example 1 A flame-retardant polyurea coating is provided, and its preparation method includes the following steps: (1) Preparation of component A Weigh out 400 parts of polyetheramine D-2000, 10 parts of D-MXene 2#, and 100 parts of modified BNNS 2# according to the weight ratio, and add them together to NMP solvent (80 parts); The mixture was placed in a high-speed shear disperser, with a rotation speed of 5000 r / min, and sheared for 1 hour to initially break up the filler agglomerates. Then it was transferred to a 40kHz, 500W ultrasonic cell disruptor, using an intermittent working mode (5 seconds on, 5 seconds off), with a total ultrasonic treatment time of 30 minutes, to completely remove the filler agglomerates and improve the dispersion uniformity, finally obtaining a non-agglomerated, high-viscosity filler-amine mixed dispersion. Add 100 parts of terminal amine chain extender DETDA to the above filler-amine mixed dispersion, turn on mechanical stirring (300~500 r / min), stir at room temperature for 30 min until the system is completely mixed and there is no layering, thus obtaining component A of Example 1 (as shown in Table 4). (3) Component B 445 parts of MDI prepolymer; Tests showed that the molar ratio of amine groups in component A to isocyanate groups in component B of MDI prepolymer in Example 1 was R=1.07, which meets the requirement of 1.05~1.1.

[0065] Example 2 A flame-retardant polyurea coating is provided, and its preparation method includes the following steps: (1) Preparation of component A Weigh out 350 parts of polyetheramine D-2000, 5 parts of D-MXene 2#, and 50 parts of modified BNNS 2# according to the weight ratio, and add them together to 50 parts of NMP solvent; The mixture was placed in a high-speed shear disperser, with a rotation speed of 5000 r / min, and sheared for 1 hour to initially break up the filler agglomerates. Then it was transferred to a 40kHz, 500W ultrasonic cell disruptor, using an intermittent working mode (5 seconds on, 5 seconds off), with a total ultrasonic treatment time of 30 minutes, to completely remove the filler agglomerates and improve the dispersion uniformity, finally obtaining a non-agglomerated, high-viscosity filler-amine mixed dispersion. Add 120 parts of terminal amine chain extender DETDA to the above filler-amine mixed dispersion, turn on mechanical stirring (300~500 r / min), stir at room temperature for 30 min until the system is completely mixed and there is no layering, thus obtaining component A of Example 2 (as shown in Table 4). (3) Component B 445 parts of MDI prepolymer; Tests showed that the molar ratio of amine groups in component A to isocyanate groups in component B of MDI prepolymer in Example 2 was R=1.06, which meets the requirement of 1.05~1.1.

[0066] Example 3 A flame-retardant polyurea coating is provided, and its preparation method includes the following steps: (1) Preparation of component A Weigh out 450 parts of polyetheramine D-2000, 20 parts of D-MXene 2#, and 150 parts of modified BNNS 2# according to the weight ratio, and add them together to 100 parts of NMP solvent; The mixture was placed in a high-speed shear disperser, with a rotation speed of 5000 r / min, and sheared for 1 hour to initially break up the filler agglomerates. Then it was transferred to a 40kHz, 500W ultrasonic cell disruptor, using an intermittent working mode (5 seconds on, 5 seconds off), with a total ultrasonic treatment time of 30 minutes, to completely remove the filler agglomerates and improve the dispersion uniformity, finally obtaining a non-agglomerated, high-viscosity filler-amine mixed dispersion. Add 80 parts of terminal amine chain extender DETDA to the above filler-amine mixed dispersion, turn on mechanical stirring (300~500 r / min), stir at room temperature for 30 min until the system is completely mixed and there is no layering, thus obtaining component A of Example 3 (as shown in Table 4). (3) Component B 445 parts of MDI prepolymer; Tests showed that the molar ratio of amine groups in component A to isocyanate groups in component B of MDI prepolymer in Example 3 was R=1.09, which meets the requirement of 1.05~1.1.

[0067] Example 4 A flame-retardant polyurea coating is provided, and its preparation method includes the following steps: (1) Preparation of component A Weigh out 300 parts of polyetheramine D-2000, 100 parts of polyetheramine D-400, 10 parts of D-MXene 2#, and 100 parts of modified BNNS 2# according to the weight ratio, and add them together to NMP solvent (80 parts); The mixture was placed in a high-speed shear disperser, with a rotation speed of 5000 r / min, and sheared for 1 hour to initially break up the filler agglomerates. Then it was transferred to a 40kHz, 500W ultrasonic cell disruptor, using an intermittent working mode (5 seconds on, 5 seconds off), with a total ultrasonic treatment time of 30 minutes, to completely remove the filler agglomerates and improve the dispersion uniformity, finally obtaining a non-agglomerated, high-viscosity filler-amine mixed dispersion. Add 100 parts of terminal amine chain extender DETDA to the above filler-amine mixed dispersion, turn on mechanical stirring (300~500 r / min), stir at room temperature for 30 min until the system is completely mixed and there is no layering, thus obtaining component A of Example 4 (as shown in Table 4). (3) Component B 445 parts of MDI prepolymer; Tests showed that the molar ratio of amine groups in component A to isocyanate groups in component B of MDI prepolymer in Example 4 was R=1.08, which meets the requirement of 1.05~1.1.

[0068] Example 5 A flame-retardant polyurea coating is provided, and its preparation method includes the following steps: (1) Preparation of component A Weigh out 350 parts of polyetheramine D-2000, 50 parts of polyetheramine D-400, 10 parts of D-MXene 2#, and 100 parts of modified BNNS 2# according to the weight ratio, and add them together to NMP solvent (80 parts); The mixture was placed in a high-speed shear disperser, with a rotation speed of 5000 r / min, and sheared for 1 hour to initially break up the filler agglomerates. Then it was transferred to a 40kHz, 500W ultrasonic cell disruptor, using an intermittent working mode (5 seconds on, 5 seconds off), with a total ultrasonic treatment time of 30 minutes, to completely remove the filler agglomerates and improve the dispersion uniformity, finally obtaining a non-agglomerated, high-viscosity filler-amine mixed dispersion. Add 100 parts of terminal amine chain extender DETDA to the above filler-amine mixed dispersion, turn on mechanical stirring (300~500 r / min), stir at room temperature for 30 min until the system is completely mixed and there is no layering, thus obtaining component A of Example 5 (as shown in Table 4). (3) Component B 445 parts of MDI prepolymer; Tests showed that the molar ratio of amine groups in component A to isocyanate groups in component B of MDI prepolymer in Example 5 was R=1.08, which meets the requirement of 1.05~1.1.

[0069] Example 6 A flame-retardant polyurea coating is provided, and its preparation method includes the following steps: (1) Preparation of component A Weigh out 400 parts of polyetheramine D-2000, 10 parts of D-MXene 2#, and 100 parts of modified BNNS 2# according to the weight ratio, and add them together to NMP solvent (80 parts); The mixture was placed in a high-speed shear disperser, with a rotation speed of 5000 r / min, and sheared for 1 hour to initially break up the filler agglomerates. Then it was transferred to a 40kHz, 500W ultrasonic cell disruptor, using an intermittent working mode (5 seconds on, 5 seconds off), with a total ultrasonic treatment time of 30 minutes, to completely remove the filler agglomerates and improve the dispersion uniformity, finally obtaining a non-agglomerated, high-viscosity filler-amine mixed dispersion. Add 100 parts of terminal amine chain extender EDA to the above filler-amine mixed dispersion, turn on mechanical stirring (300~500 r / min), stir at room temperature for 30 min until the system is completely mixed and there is no layering, thus obtaining component A of Example 6 (as shown in Table 4). (3) Component B 445 parts of MDI prepolymer; Tests showed that the molar ratio of amine groups in component A to isocyanate groups in component B of MDI prepolymer in Example 6 was R=1.06, which meets the requirement of 1.05~1.1.

[0070] Example 7 A flame-retardant polyurea coating is provided, and its preparation method includes the following steps: (1) Preparation of component A Weigh out 400 parts of polyetheramine D-2000, 10 parts of D-MXene 1#, and 100 parts of modified BNNS 2# according to the weight ratio, and add them together to NMP solvent (80 parts); The mixture was placed in a high-speed shear disperser, with a rotation speed of 5000 r / min, and sheared for 1 hour to initially break up the filler agglomerates. Then it was transferred to a 40kHz, 500W ultrasonic cell disruptor, using an intermittent working mode (5 seconds on, 5 seconds off), with a total ultrasonic treatment time of 30 minutes, to completely remove the filler agglomerates and improve the dispersion uniformity, finally obtaining a non-agglomerated, high-viscosity filler-amine mixed dispersion. Add 100 parts of terminal amine chain extender DETDA to the above filler-amine mixed dispersion, turn on mechanical stirring (300~500 r / min), stir at room temperature for 30 min until the system is completely mixed and there is no layering, thus obtaining component A of Example 7 (as shown in Table 4). (3) Component B 445 parts of MDI prepolymer; Tests showed that the molar ratio of amine groups in component A to isocyanate groups in component B of MDI prepolymer in Example 7 was R=1.07, which meets the requirement of 1.05~1.1.

[0071] Example 8 A flame-retardant polyurea coating is provided, and its preparation method includes the following steps: (1) Preparation of component A Weigh out 400 parts of polyetheramine D-2000, 10 parts of D-MXene 3#, and 100 parts of modified BNNS 2# according to the weight ratio, and add them together to NMP solvent (80 parts); The mixture was placed in a high-speed shear disperser, with a rotation speed of 5000 r / min, and sheared for 1 hour to initially break up the filler agglomerates. Then it was transferred to a 40kHz, 500W ultrasonic cell disruptor, using an intermittent working mode (5 seconds on, 5 seconds off), with a total ultrasonic treatment time of 30 minutes, to completely remove the filler agglomerates and improve the dispersion uniformity, finally obtaining a non-agglomerated, high-viscosity filler-amine mixed dispersion. Add 100 parts of terminal amine chain extender DETDA to the above filler-amine mixed dispersion, turn on mechanical stirring (300~500 r / min), stir at room temperature for 30 min until the system is completely mixed and there is no layering, thus obtaining component A of Example 8 (as shown in Table 4). (3) Component B 445 parts of MDI prepolymer; Tests showed that the molar ratio of amine groups in component A to isocyanate groups in component B of MDI prepolymer in Example 8 was R=1.07, which meets the requirement of 1.05~1.1.

[0072] Example 9 A flame-retardant polyurea coating is provided, and its preparation method includes the following steps: (1) Preparation of component A Weigh out 400 parts of polyetheramine D-2000, 10 parts of D-MXene 4#, and 100 parts of modified BNNS 2# according to the weight ratio, and add them together to NMP solvent (80 parts); The mixture was placed in a high-speed shear disperser, with a rotation speed of 5000 r / min, and sheared for 1 hour to initially break up the filler agglomerates. Then it was transferred to a 40kHz, 500W ultrasonic cell disruptor, using an intermittent working mode (5 seconds on, 5 seconds off), with a total ultrasonic treatment time of 30 minutes, to completely remove the filler agglomerates and improve the dispersion uniformity, finally obtaining a non-agglomerated, high-viscosity filler-amine mixed dispersion. Add 100 parts of terminal amine chain extender DETDA to the above filler-amine mixed dispersion, turn on mechanical stirring (300~500 r / min), stir at room temperature for 30 min until the system is completely mixed and there is no layering, thus obtaining component A of Example 9 (as shown in Table 4). (3) Component B 445 parts of MDI prepolymer; Tests showed that the molar ratio of amine groups in component A to isocyanate groups in component B of MDI prepolymer in Example 9 was R=1.07, which meets the requirement of 1.05~1.1.

[0073] Example 10 A flame-retardant polyurea coating is provided, and its preparation method includes the following steps: (1) Preparation of component A Weigh out 400 parts of polyetheramine D-2000, 10 parts of D-MXene 5#, and 100 parts of modified BNNS 2# according to the weight ratio, and add them together to NMP solvent (80 parts); The mixture was placed in a high-speed shear disperser, with a rotation speed of 5000 r / min, and sheared for 1 hour to initially break up the filler agglomerates. Then it was transferred to a 40kHz, 500W ultrasonic cell disruptor, using an intermittent working mode (5 seconds on, 5 seconds off), with a total ultrasonic treatment time of 30 minutes, to completely remove the filler agglomerates and improve the dispersion uniformity, finally obtaining a non-agglomerated, high-viscosity filler-amine mixed dispersion. Add 100 parts of terminal amine chain extender DETDA to the above filler-amine mixed dispersion, turn on mechanical stirring (300~500 r / min), stir at room temperature for 30 min until the system is completely mixed and there is no layering, and thus obtain component A of Example 10 (as shown in Table 4). (3) Component B 445 parts of MDI prepolymer; Tests showed that the molar ratio of amine groups in component A to isocyanate groups in component B of MDI prepolymer in Example 10 was R=1.07, which meets the requirement of 1.05~1.1.

[0074] Example 11 A flame-retardant polyurea coating is provided, and its preparation method includes the following steps: (1) Preparation of component A Weigh out 400 parts of polyetheramine D-2000, 10 parts of D-MXene 6#, and 100 parts of modified BNNS 4# according to the weight ratio, and add them together to NMP solvent (80 parts); The mixture was placed in a high-speed shear disperser, with a rotation speed of 5000 r / min, and sheared for 1 hour to initially break up the filler agglomerates. Then it was transferred to a 40kHz, 500W ultrasonic cell disruptor, using an intermittent working mode (5 seconds on, 5 seconds off), with a total ultrasonic treatment time of 30 minutes, to completely remove the filler agglomerates and improve the dispersion uniformity, finally obtaining a non-agglomerated, high-viscosity filler-amine mixed dispersion. Add 100 parts of terminal amine chain extender DETDA to the above filler-amine mixed dispersion, turn on mechanical stirring (300~500 r / min), stir at room temperature for 30 min until the system is completely mixed and there is no layering, and thus obtain component A of Example 11 (as shown in Table 4). (3) Component B 445 parts of MDI prepolymer; Tests showed that the molar ratio of amine groups in component A to isocyanate groups in component B of MDI prepolymer in Example 11 was R=1.07, which meets the requirement of 1.05~1.1.

[0075] Example 12 A flame-retardant polyurea coating is provided, and its preparation method includes the following steps: (1) Preparation of component A Weigh out 400 parts of polyetheramine D-2000, 10 parts of D-MXene 7#, and 100 parts of modified BNNS 5# according to the weight ratio, and add them together to NMP solvent (80 parts); The mixture was placed in a high-speed shear disperser, with a rotation speed of 5000 r / min, and sheared for 1 hour to initially break up the filler agglomerates. Then it was transferred to a 40kHz, 500W ultrasonic cell disruptor, using an intermittent working mode (5 seconds on, 5 seconds off), with a total ultrasonic treatment time of 30 minutes, to completely remove the filler agglomerates and improve the dispersion uniformity, finally obtaining a non-agglomerated, high-viscosity filler-amine mixed dispersion. Add 100 parts of terminal amine chain extender DETDA to the above filler-amine mixed dispersion, turn on mechanical stirring (300~500 r / min), stir at room temperature for 30 min until the system is completely mixed and there is no layering, thus obtaining component A of Example 12 (as shown in Table 4). (3) Component B 445 parts of MDI prepolymer; Tests showed that the molar ratio of amine groups in component A to isocyanate groups in component B of MDI prepolymer in Example 12 was R=1.07, which meets the requirement of 1.05~1.1.

[0076] Example 13 A flame-retardant polyurea coating is provided, and its preparation method includes the following steps: (1) Preparation of component A Weigh out 400 parts of polyetheramine D-2000, 10 parts of D-MXene 2#, and 100 parts of modified BNNS 1# according to the weight ratio, and add them together to NMP solvent (80 parts); The mixture was placed in a high-speed shear disperser, with a rotation speed of 5000 r / min, and sheared for 1 hour to initially break up the filler agglomerates. Then it was transferred to a 40kHz, 500W ultrasonic cell disruptor, using an intermittent working mode (5 seconds on, 5 seconds off), with a total ultrasonic treatment time of 30 minutes, to completely remove the filler agglomerates and improve the dispersion uniformity, finally obtaining a non-agglomerated, high-viscosity filler-amine mixed dispersion. Add 100 parts of terminal amine chain extender DETDA to the above filler-amine mixed dispersion, turn on mechanical stirring (300~500 r / min), stir at room temperature for 30 min until the system is completely mixed and there is no layering, thus obtaining component A of Example 13 (as shown in Table 4). (3) Component B 445 parts of MDI prepolymer; Tests showed that the molar ratio of amine groups in component A to isocyanate groups in component B of MDI prepolymer in Example 13 was R=1.07, which meets the requirement of 1.05~1.1.

[0077] Example 14 A flame-retardant polyurea coating is provided, and its preparation method includes the following steps: (1) Preparation of component A Weigh out 400 parts of polyetheramine D-2000, 10 parts of D-MXene 2#, and 100 parts of modified BNNS 3# according to the weight ratio, and add them together to NMP solvent (80 parts); The mixture was placed in a high-speed shear disperser, with a rotation speed of 5000 r / min, and sheared for 1 hour to initially break up the filler agglomerates. Then it was transferred to a 40kHz, 500W ultrasonic cell disruptor, using an intermittent working mode (5 seconds on, 5 seconds off), with a total ultrasonic treatment time of 30 minutes, to completely remove the filler agglomerates and improve the dispersion uniformity, finally obtaining a non-agglomerated, high-viscosity filler-amine mixed dispersion. Add 100 parts of terminal amine chain extender DETDA to the above filler-amine mixed dispersion, turn on mechanical stirring (300~500 r / min), stir at room temperature for 30 min until the system is completely mixed and there is no layering, thus obtaining component A of Example 14 (as shown in Table 4). (3) Component B 445 parts of MDI prepolymer; Tests showed that the molar ratio of amine groups in component A to isocyanate groups in component B of MDI prepolymer in Example 14 was R=1.07, which meets the requirement of 1.05~1.1.

[0078] Table 4. Components (parts by weight) of flame-retardant polyurea coatings Table 4 (continued) Example 15 A flame-retardant polyurea coating is provided, and its preparation method includes the following steps: (1) Preparation of component A Weigh out 400 parts of polyetheramine D-2000, 10 parts of D-MXene 2#, and 100 parts of modified BNNS 2# according to the weight ratio, and add them together to NMP solvent (80 parts); The mixture was placed in a high-speed shear disperser, with a rotation speed of 5000 r / min, and sheared for 1 hour to initially break up the filler agglomerates. Then it was transferred to a 40kHz, 500W ultrasonic cell disruptor, using an intermittent working mode (5 seconds on, 5 seconds off), with a total ultrasonic treatment time of 30 minutes, to completely remove the filler agglomerates and improve the dispersion uniformity, finally obtaining a non-agglomerated, high-viscosity filler-amine mixed dispersion. Add 100 parts of terminal amine chain extender DETDA to the above filler-amine mixed dispersion, turn on mechanical stirring (300~500 r / min), stir at room temperature for 30 min until the system is completely mixed and there is no layering, and thus obtain component A of Example 15 (as shown in Example 1 in Table 4). (3) Component B 500 parts of IPDI prepolymer; Tests showed that the molar ratio of amine groups in component A to isocyanate groups in component B of IPDI prepolymer in Example 15 was R=1.06, which meets the requirement of 1.05~1.1.

[0079] Example 16 A flame-retardant polyurea coating is provided, and its preparation method includes the following steps: (1) Preparation of component A Weigh out 400 parts of polyetheramine D-2000, 10 parts of D-MXene 2#, and 100 parts of modified BNNS 2# according to the weight ratio, and add them together to NMP solvent (80 parts); The mixture was placed in a high-speed shear disperser, with a rotation speed of 5000 r / min, and sheared for 1 hour to initially break up the filler agglomerates. Then it was transferred to a 40kHz, 500W ultrasonic cell disruptor, using an intermittent working mode (5 seconds on, 5 seconds off), with a total ultrasonic treatment time of 30 minutes, to completely remove the filler agglomerates and improve the dispersion uniformity, finally obtaining a non-agglomerated, high-viscosity filler-amine mixed dispersion. Add 100 parts of terminal amine chain extender DETDA to the above filler-amine mixed dispersion, turn on mechanical stirring (300~500 r / min), stir at room temperature for 30 min until the system is completely mixed and there is no layering, and thus obtain component A of Example 16 (as shown in Example 1 in Table 4). (3) Component B 480 parts HMDI prepolymer; Tests showed that the molar ratio of amine groups in component A to isocyanate groups in component B of HMDI prepolymer in Example 16 was R=1.09, which meets the requirement of 1.05~1.1.

[0080] Example 17 A flame-retardant polyurea coating is provided, and its preparation method includes the following steps: (1) Preparation of component A Weigh out 400 parts of polyetheramine D-2000, 10 parts of D-MXene 2#, and 100 parts of modified BNNS 2# according to the weight ratio, and add them together to NMP solvent (80 parts); The mixture was placed in a high-speed shear disperser, with a rotation speed of 5000 r / min, and sheared for 1 hour to initially break up the filler agglomerates. Then it was transferred to a 40kHz, 500W ultrasonic cell disruptor, using an intermittent working mode (5 seconds on, 5 seconds off), with a total ultrasonic treatment time of 30 minutes, to completely remove the filler agglomerates and improve the dispersion uniformity, finally obtaining a non-agglomerated, high-viscosity filler-amine mixed dispersion. Add 100 parts of terminal amine chain extender DETDA to the above filler-amine mixed dispersion, turn on mechanical stirring (300~500 r / min), stir at room temperature for 30 min until the system is completely mixed and there is no layering, and thus obtain component A of Example 17 (as shown in Example 1 in Table 4). (3) Component B 460 parts of TDI prepolymer; Tests showed that the molar ratio of amine groups in component A to isocyanate groups in component B of TDI prepolymer in Example 17 was R=1.1, which meets the requirement of 1.05~1.1.

[0081] Comparative Example 1 A flame-retardant polyurea coating is provided, and its preparation method includes the following steps: (1) Preparation of component A Weigh out 400 parts of polyetheramine D-2000, 10 parts of D-MXene 8#, and 100 parts of modified BNNS 6# according to the weight ratio, and add them together to NMP solvent (80 parts); that is, in this comparative example, the sheet diameter d1 (3μm) of the two-dimensional transition metal carbide "D-MXene 8#" is greater than the sheet diameter d2 (1μm) of the boron nitride nanosheet "modified BNNS 6#"; The mixture was placed in a high-speed shear disperser, with a rotation speed of 5000 r / min, and sheared for 1 hour to initially break up the filler agglomerates. Then it was transferred to a 40kHz, 500W ultrasonic cell disruptor, using an intermittent working mode (5 seconds on, 5 seconds off), with a total ultrasonic treatment time of 30 minutes, to completely remove the filler agglomerates and improve the dispersion uniformity, finally obtaining a non-agglomerated, high-viscosity filler-amine mixed dispersion. Add 100 parts of terminal amine chain extender DETDA to the above filler-amine mixed dispersion, turn on mechanical stirring (300~500 r / min), stir at room temperature for 30 min until the system is completely mixed and there is no layering, thus obtaining component A of Comparative Example 1 (as shown in Table 4). (3) Component B 445 parts of MDI prepolymer; Tests showed that the molar ratio of amine groups in component A to isocyanate groups in component B of MDI prepolymer in Example 1 was R=1.07, which meets the requirement of 1.05~1.1.

[0082] Comparative Example 2 A flame-retardant polyurea coating is provided. The preparation method is described in Example 1, except that 10 parts by weight of D-MXene (2#) is replaced with 1.67 parts by weight of flame retardant DOPO and 8.33 parts by weight of MXene (Ti3C2T). x (d1 is 1 μm, and the sheet thickness is 3 nm).

[0083] Comparative Example 3 A flame-retardant polyurea coating is provided. The preparation method is described in Example 1. The difference from Example 1 is that no silane coupling agent-modified BNNS is added.

[0084] Comparative Example 4 A flame-retardant polyurea coating is provided. The preparation method is described in Example 1. The difference from Example 1 is that D-MXene is not added.

[0085] Comparative Example 5 A flame-retardant polyurea coating is provided. The preparation method is described in Example 1, except that 10 parts by weight of D-MXene in Example 1 are replaced with 10 parts by weight of MXene (Ti3C2T). x (d1 is 1 μm, and the sheet thickness is 3 nm).

[0086] Comparative Example 6 A flame-retardant polyurea coating is provided. The preparation method is described in Example 1. The difference from Example 1 is that the silane coupling agent modified BNNS is replaced with an equal part by weight of silane coupling agent modified nano alumina (alumina particle size Dv50=50nm), wherein the grafting rate of the silane coupling agent is the same as that of 2# BNNS-NH2.

[0087] Comparative Example 7 A flame-retardant polyurea coating is provided. The preparation method is described in Example 1. The difference from Example 1 is that 2# D-MXene and 2# BNNS-NH2 are not added to component A.

[0088] Performance testing Components A and B of the flame-retardant polyurea coatings prepared according to the above embodiments and comparative examples were poured into a static mixing tube in proportion, quickly injected into a mold, cured in an oven at 80°C for 30 minutes, and then demolded to obtain the flame-retardant polyurea material. (It should be noted that, in this invention, for ease of testing, the coating is injected into a mold for curing. The coating of this invention can also be mixed and sprayed onto the surface of the substrate (including but not limited to battery casings, etc.) that needs protection before curing. The performance of the cured flame-retardant polyurea material was tested, and the test methods and test results (see Table 5) are as follows:) 1. Thermal conductivity: Thermal conductivity was tested using a laser flash thermal conductivity meter at a temperature of 25℃, and the unit is W / m·K. 2. Flame retardant properties: The oxygen index (LOI) was tested according to the test method in standard GB / T 2406.2-2009 using an oxygen index tester at a test temperature of 23±2℃. The unit of oxygen index (LOI) is %. 3. Insulation performance: Volume resistivity was tested using a high-resistivity meter under the conditions of 25°C and 50% relative humidity. The unit of volume resistivity is Ω·cm. The higher the volume resistivity, the better the insulation performance of the sample. 4. Mechanical properties The tensile strength (in MPa) of the flame-retardant polyurea sample was tested using a tensile testing machine at a temperature of 25±2℃ and a tensile rate of 50 mm / min. 5. Microscopic morphology confirmation: The brittle fracture section of the flame-retardant polyurea material was observed using field emission scanning electron microscopy (SEM) (magnification 10,000x; see Example 1 for details). Figure 1 It can be clearly seen that the larger BNNS sheets overlap each other to form a three-dimensional thermally conductive skeleton; the smaller D-MXene sheets are uniformly filled in the gaps of the BNNS skeleton, acting as a "bridge". Both fillers are tightly bonded to the polyurea matrix, with no obvious phase separation or agglomeration.

[0089] Table 5 The results above show that: The flame-retardant polyurea materials of the embodiments of the present invention possess excellent flame retardancy, insulation, thermal conductivity, and mechanical properties, wherein the thermal conductivity is above 0.55 W / m·K, the oxygen index is above 32%, and the volume resistivity is above 1×10⁻⁶. 11 The Ω·cm is above 26MPa and the tensile strength is above 26MPa.

[0090] Compared with Example 1, the two-dimensional transition metal carbide “D-MXene 8#” in Comparative Example 1 has a sheet diameter d1 (3 μm) larger than the sheet diameter d2 (1 μm) of the boron nitride nanosheet “modified BNNS 6#”. Therefore, it cannot form the specific filler network of the present invention, and the thermal conductivity, insulation and mechanical properties cannot be improved at the same time, especially the tensile strength is significantly reduced.

[0091] In Comparative Example 2, the flame retardant was not grafted onto MXene, resulting in significantly worse performance than in Example 1. The oxygen index was significantly reduced, and the flame retardant performance was worse than in Example 1. The interaction between the components led to differences in the dispersion of each component in the flame retardant polyurea material. Compared with Example 1, the tensile strength and insulation performance were also relatively poor.

[0092] In Comparative Examples 3 and 4, only D-MXene or silane coupling agent-modified BNNS were added, and the flame retardant and insulation properties of the prepared flame-retardant polyurea materials were significantly reduced.

[0093] In Comparative Example 5, no flame retardant was added to the polyurea flame retardant material, resulting in poor flame retardant performance. The volume conductivity of the flame retardant polyurea material in Comparative Example 5 was also reduced, further indicating that the flame retardant grafted onto MXene and dispersed in the polyurea matrix, working together with other raw materials, also helps to improve the insulation performance of the polyurea flame retardant material.

[0094] Comparative Example 6 replaced the insulating filler—modified BNNS—in Example 1 with ordinary insulating filler nano-alumina. However, it did not form a specific thermally conductive network in the flame-retardant polyurea material, resulting in a lower thermal conductivity than Example 1. Furthermore, the nano-alumina does not have a lamellar structure and cannot form a specific network structure with D-MXene, leading to poor compatibility of the organic-inorganic interface in the system. Consequently, the mechanical properties of the flame-retardant polyurea material are significantly worse than those in Example 1.

[0095] Comparative Example 7 is a polyurea material that has not undergone thermal conductivity and insulation modification. The polyurea material has poor thermal conductivity, flame retardancy and insulation properties.

[0096] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A flame-retardant polyurea coating, characterized in that, The components include the following parts by weight: Component A: 350-450 parts polyetheramine, 80-120 parts terminal amine chain extender, 5-20 parts two-dimensional transition metal carbides with flame retardant grafted on the surface, 50-150 parts silane coupling agent modified boron nitride nanosheets, and 50-100 parts solvent. Wherein, the sheet diameter of the two-dimensional transition metal carbide is d1μm, and the sheet diameter of the boron nitride nanosheet is d2μm, satisfying: d1<d2; Component B: Isocyanate prepolymer.

2. The flame-retardant polyurea coating according to claim 1, characterized in that, In the two-dimensional transition metal carbide with flame retardant grafted onto its surface, the weight ratio of flame retardant to two-dimensional transition metal carbide is (10~30):

100.

3. The flame-retardant polyurea coating according to claim 1, characterized in that, The flame retardant includes a DOPO type flame retardant, which includes at least one of DOPO-Cl and DOPO-OH.

4. The flame-retardant polyurea coating according to claim 1, characterized in that, The two-dimensional transition metal carbide includes at least one compound having the following chemical formula: Ti3C2T x V2CT x Ti2CT x T x The functional groups representing the surface of the two-dimensional transition metal carbide include at least one of -OH and -F.

5. The flame-retardant polyurea coating according to claim 1, characterized in that, The two-dimensional transition metal carbide has a sheet diameter d1μm = 0.2~1μm and a sheet thickness of 1~5nm.

6. The flame-retardant polyurea coating according to claim 1, characterized in that, The boron nitride nanosheets have a diameter d2μm = 1~5μm and a sheet thickness of 10~50nm; And / or, in the silane coupling agent modified boron nitride nanosheets, the weight of the silane coupling agent accounts for 2-5% of the weight of the boron nitride nanosheets; And / or, the silane coupling agent includes at least one of KH550 and KH560.

7. The flame-retardant polyurea coating according to claim 1, characterized in that, It satisfies at least one of the following characteristics: (1) The weight-average molecular weight of the polyetheramine is 400~2000; (2) The terminal amine chain extender includes at least one of diethyltoluenediamine, 4,4′-diaminodiphenylmethane, 1,4-butanediamine, and 1,6-hexanediamine; (3) The isocyanate prepolymer includes at least one of MDI prepolymer, IPDI prepolymer, HMDI prepolymer, and TDI prepolymer; (4) The viscosity of the isocyanate prepolymer at 25°C is 2000~8000cps.

8. The method for preparing the flame-retardant polyurea coating according to any one of claims 1 to 7, characterized in that, Includes the following steps: (1) Raw material pretreatment After etching and stripping, the two-dimensional transition metal carbide is dissolved in a non-aqueous solvent, a flame retardant is added, and a grafting reaction is carried out in a catalyst and an inert atmosphere to obtain a two-dimensional transition metal carbide with a flame retardant grafted on its surface. Silane coupling agent and boron nitride nanosheets were dispersed in a hydrophilic solvent and stirred at 50-70℃ for 3-6 h to obtain silane coupling agent modified boron nitride nanosheets. (2) Preparation of component A According to the weight ratio, polyetheramine, two-dimensional transition metal carbides with flame retardant grafted on the surface, and boron nitride nanosheets modified with silane coupling agent were dispersed in a solvent and sheared to obtain a dispersion. Add a terminal amine chain extender to the dispersion, stir, and obtain component A; (3) Preparation of component B The monomers of the isocyanate prepolymer undergo a copolymerization reaction to obtain the isocyanate prepolymer.

9. The application of the flame-retardant polyurea coating according to any one of claims 1 to 7, characterized in that, The flame-retardant polyurea coating is used to prepare a protective coating.

10. The application of the flame-retardant polyurea coating according to claim 9, characterized in that, The method for preparing the protective coating includes the following steps: After mixing components A and B, the mixture is heat-cured at 25~80℃ for 0.5~2h, and then dried to obtain the protective coating. The molar ratio of amine groups in component A to isocyanate groups in component B is 1.05 to 1.1.

Images