Wear-resistant flame-retardant polyurea coating and preparation method thereof

Abstract

The invention relates to the technical field of coatings, in particular to a wear-resistant flame-retardant polyurea coating and a preparation method thereof. The coating is prepared from a component A and a component B according to the weight ratio of 1: 1, the component A contains hexamethylene diisocyanate tripolymer and isophorone diisocyanate tripolymer butyl acetate solution, and the component B contains polyether diamine, DOPO-lignin grafted diamine, an aspartate chain extender, a lignin grafted amphoteric copolymer, gamma-aminopropyltriethoxysilane and the like. Through the synergistic effect of a phosphorus-containing aromatic structure and a nitrogen-containing chain segment, a compact carbon-rich protective layer is formed during combustion, free radicals are inhibited, and excellent flame-retardant and smoke-inhibiting effects are achieved; an isocyanurate hard segment network and an aspartate slow-release curing system improve the wear resistance and the crack resistance; the amphoteric chain segment and silane coupling structure enhances the interfacial adhesion and reduces the curing stress. The coating comprehensively has high flame retardance, excellent wear resistance, strong adhesive force and good constructability.

Description

Technical Field

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

[0002] Polyurea coatings, with their high reactivity, rapid curing, corrosion resistance, and erosion resistance, are widely used in bridges, storage tanks, flooring, and protective facilities. However, the polyurea system, formed by the rapid reaction of highly polar isocyanates and polyamines, has a flexible main chain and low aromaticity, making it prone to decomposition and the generation of flammable debris under high temperatures or flame environments, resulting in poor flame retardant properties. To improve flame retardancy, existing technologies often employ inorganic fillers (such as aluminum hydroxide, magnesium hydroxide, and phosphates) or halogen-phosphorus-containing organic flame retardants. However, a high proportion of inorganic fillers leads to increased system viscosity, poor leveling, and decreased interfacial bonding, while also disrupting the elastic network structure of the polyurea. On the other hand, small-molecule organic flame retardants suffer from migration, precipitation, and incomplete reaction with isocyanates, resulting in coating surfaces that are prone to stickiness, loss of gloss, or chalking under long-term service, failing to meet the long-term protection requirements of thick films. Thus, improving flame retardant performance often comes at the cost of sacrificing mechanical properties, creating a structural contradiction that is difficult to reconcile.

[0003] On the other hand, although polyurea coatings possess high elongation at break and good adhesion, the wear resistance of traditional formulations still falls short of requirements in high-friction environments such as heavy-load wear, sandblasting, or vehicle traffic. The flexible matrix of polyurea exhibits a discontinuous phase structure at the microscopic level, dominated by soft segments and dispersed with hard segments. When external shear and wear concentrate at the hard segment interface, microcracks easily form and propagate, leading to increased wear and surface failure. Existing research attempts to improve wear resistance by increasing crosslinking density or the proportion of hard segments; however, excessively high crosslinking can introduce embrittlement risks, accelerating crack propagation under temperature cycling or impact loading.

[0004] Furthermore, polyurea bonds with substrates such as metals and concrete primarily through physical intercalation or polar adsorption, lacking a stable chemical anchoring layer. Under humid, salt spray, or thermal cycling conditions, the mismatch between the hydration reaction and thermal expansion at the interface can cause stress concentration, leading to problems such as blistering and delamination. Interface failure becomes the main durability bottleneck for thick-film polyurea systems. Some literature attempts to improve adhesion through primer tackification or roughening treatments, but the stress gradient and rapid curing of thick-film systems can still cause microcracks and delamination.

[0005] A more prominent problem is the extremely rapid curing rate of polyurea, with concentrated exothermic reaction and a rapid rise in internal temperature, making it difficult to effectively release curing shrinkage and internal stress. In thick-film applications, the surface layer cures rapidly while the interior remains under high stress, easily leading to edge warping, cracking, or interface separation. While the use of highly reactive aromatic diamines can accelerate drying time, their high exothermic peak and rapid gelation further amplify internal stress. As a result, the inorganic or organic components added to improve flame retardancy alter the thermomechanical balance of the system, exacerbating residual stress and embrittlement tendencies within the coating.

[0006] In summary, existing polyurea protective systems generally suffer from the following common technical challenges: flame retardant modification and wear resistance enhancement are difficult to achieve simultaneously, often resulting in a counterproductive effect of flame retardant enhancement and mechanical degradation; insufficient interfacial anchoring, with damp heat and cold heat cycles under thick film conditions leading to decreased adhesion; and intense curing reaction and concentrated internal stress, which easily cause thick film cracks and peeling.

[0007] These issues limit the overall performance of polyurea coatings in engineering applications such as fire resistance, abrasion resistance, and structural protection. Systematic improvements are urgently needed to coordinate the balance between flame retardancy, abrasion resistance, adhesion, and curing stability. Summary of the Invention

[0008] In view of this, the purpose of this invention is to propose a wear-resistant and flame-retardant polyurea coating and its preparation method, so as to solve the problems of the contradiction between the flame retardant and wear-resistant properties of polyurea coatings, easy interface failure and high curing stress.

[0009] To achieve the above objectives, the present invention provides a wear-resistant and flame-retardant polyurea coating, comprising component A and component B, wherein component A and component B are formulated in a weight ratio of 1:1. By weight, component A comprises: 600-800 parts of hexamethylene diisocyanate trimer, and 200-400 parts of isophorone diisocyanate trimer butyl acetate solution; component B comprises: 580-660 parts of polyether diamine, 80-120 parts of DOPO (9,10-dihydro-9-oxo-10-phosphenanthroline-10-oxide)-lignin grafted diamine, 80-120 parts of diethyltoluene diamine, 60-80 parts of aspartic acid ester chain extender, 2-5 parts of lignin grafted amphoteric copolymer, 8-12 parts of γ-aminopropyltriethoxysilane, 4-6 parts of polyether-modified polysiloxane leveling agent, and 23-25 ​​parts of potassium 2-ethylhexanoate solution.

[0010] Preferably, the hexamethylene diisocyanate trimer is of the type Desmodur N3300A.

[0011] Preferably, the solid content of the isophorone diisocyanate trimer butyl acetate solution is 65-75%, and the preferred model is Desmodur Z 4470 BA.

[0012] Preferably, the polyether diamine is of the type JEFFAMINE D-2000.

[0013] Preferably, the polyether-modified polysiloxane leveling agent is of model BYK-306.

[0014] Preferably, the potassium 2-ethylhexanoate solution is prepared by potassium 2-ethylhexanoate and propylene glycol methyl ether acetate in a weight ratio of 3.0-3:20.0-21.7.

[0015] Preferably, the DOPO-lignin-grafted diamine is prepared by the following method: glycidyl etherified lignin and DOPO are reacted in N,N-dimethylformamide at 80°C for 180 min, and then reacted with ethylenediamine at 60°C for 60 min; the weight ratio of glycidyl etherified lignin, DOPO, N,N-dimethylformamide and ethylenediamine is 100:120:300:60.

[0016] Preferably, the glycidyl etherified lignin is prepared by reacting alkali lignin with epichlorohydrin at 60°C for 120 min under the catalysis of tetrabutylammonium bromide and in the presence of sodium hydroxide; the weight ratio of the alkali lignin, epichlorohydrin, tetrabutylammonium bromide and sodium hydroxide aqueous solution is 50:200:5:100.

[0017] Preferably, the concentration of the sodium hydroxide aqueous solution is 50 wt%.

[0018] Preferably, the lignin-grafted amphoteric copolymer is prepared by polymerizing glycidyl etherified lignin with dodecyl methacrylate and dimethylaminoethyl methacrylate in the presence of 4-cyano-4-(thiobenzoyl)valerate and potassium carbonate, with 2,2'-azobisisobutyronitrile as an initiator, at 70°C for 240 min. The weight ratio of glycidyl etherified lignin, dodecyl methacrylate, dimethylaminoethyl methacrylate, 4-cyano-4-(thiobenzoyl)valerate, potassium carbonate, and 2,2'-azobisisobutyronitrile is 80:100:50:20:5:1.

[0019] Preferably, the aspartic acid ester chain extender is prepared by reacting isophorone diamine with diethyl maleate under nitrogen protection at 60°C for 300 min; the weight ratio of isophorone diamine to diethyl maleate is 200:400.

[0020] Furthermore, the present invention also provides a method for preparing a wear-resistant and flame-retardant polyurea coating, comprising the following steps: (1) Preparation of DOPO-lignin-grafted diamine, lignin-grafted amphoteric copolymer and aspartic acid ester chain extender; (2) Preparation of component A: Mix hexamethylene diisocyanate trimer with isophorone diisocyanate trimer butyl acetate solution and stir at room temperature for 30 min; (3) Preparation of component B: Mix polyether diamine, DOPO-lignin grafted diamine, diethyltoluene diamine, aspartic acid ester chain extender, lignin grafted amphoteric copolymer, γ-aminopropyltriethoxysilane, polyether modified polysiloxane leveling agent and potassium 2-ethylhexanoate solution and stir for 10 min; (4) Prepare a wear-resistant and flame-retardant polyurea coating by mixing component A and component B in a weight ratio of 1:1.

[0021] Furthermore, the present invention also provides a method for preparing a wear-resistant and flame-retardant polyurea coating, comprising the following steps: mixing and stirring component A and component B for 2 minutes, coating the mixture onto the surface of a substrate, leveling it at room temperature for 15 minutes, then curing it at 60°C for 90-150 minutes, raising the temperature to 80°C and continuing to cure it for 60-120 minutes, and then cooling it to room temperature to obtain a wear-resistant and flame-retardant polyurea coating.

[0022] Preferably, the thickness of the wet film after coating onto the substrate surface is 1.5-2.5 mm.

[0023] The beneficial effects of this invention are: Flame retardant and smoke suppressant effects: This solution achieves a dual-phase synergistic flame retardant mechanism by precisely introducing phosphorus-containing aromatic structures and nitrogen-containing active sites into the polyurea matrix. During combustion, these functional components rapidly construct a continuous and dense carbon-rich, phosphorus-containing glassy protective layer in the condensed phase, effectively blocking heat transfer and combustible gas diffusion; simultaneously, they efficiently capture active free radicals such as ·H and ·OH in the gas phase, significantly reducing flame energy density and smoke generation rate. This dual protection mechanism ensures that the material meets self-extinguishing standards while effectively preventing molten dripping, creating favorable conditions for personnel evacuation and fire control.

[0024] Wear and scratch resistance: A precise blending strategy of hexamethylene diisocyanate trimer and isophorone diisocyanate trimer was employed to successfully construct a continuous hard segment network structure of isocyanurate. This design allows the coating to maintain the integrity and stability of its micro-structure even under harsh conditions such as gravel erosion or wheel crushing. The introduction of aspartic ester components enables precise control of curing shrinkage and crosslinking density, ensuring the material possesses the ideal properties of being hard yet not brittle. It exhibits slow and uniform wear characteristics in long-term erosion environments, significantly extending its service life.

[0025] Interface durability: The amphoteric segment design significantly improves the compatibility and dispersion uniformity between the matrix and biomass components, effectively preventing performance degradation caused by phase separation. γ-aminopropyltriethoxysilane forms a stable chemical anchoring layer on the metal substrate surface, establishing a covalent-hydrogen hybrid anchoring mechanism. The catalytic effect of trace amounts of potassium 2-ethylhexanoate induces a moderate trimerization reaction, increasing the crosslinking density without affecting flexibility. This multi-interface design strategy ensures that the coating effectively maintains excellent adhesion strength after water resistance, damp heat resistance, and thermal shock tests, significantly reducing the risk of blistering and peeling.

[0026] Environmental benefits of the process: By constructing phosphorus- and nitrogen-containing functional structures in situ, the amount of added powder is significantly reduced, simplifying the construction process while ensuring coating leveling performance and thick coating curing quality. The biomass-derived aromatic skeleton structure effectively reduces the proportion of migratable small molecules, inhibiting the leaching of harmful substances and the toxicity of flue gas from the source, significantly improving the environmental characteristics of the material, and providing new ideas for the development of green protective coatings. Attached Figure Description

[0027] To more clearly illustrate the technical solutions in this invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only for this invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0028] Figure 1 A flowchart illustrating the preparation process of the wear-resistant and flame-retardant polyurea coating provided by this invention; Figure 2 The infrared spectra of alkali lignin, glycidyl etherified lignin, DOPO-lignin-grafted diamine, and lignin-grafted amphoteric copolymer in Example 2 of the present invention are shown. Detailed Implementation

[0029] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to specific embodiments.

[0030] Example 1:

[0031] Step 1: Preparation of glycidyl etherified lignin Add 200g epichlorohydrin to a 500mL three-necked flask, stir at 60℃, add 50g alkali lignin powder (supplier Sigma-Aldrich, catalog number L330880), then add 5g tetrabutylammonium bromide as a phase transfer catalyst, stir for 60min, add 100g sodium hydroxide aqueous solution (concentration 50wt%) dropwise, maintain reaction at 60℃ for 120min, cool to room temperature, add deionized water to separate the phases, discard the aqueous phase, and recover unreacted epichlorohydrin under reduced pressure to obtain glycidyl etherified lignin; Step 2: Preparation of DOPO-lignin-grafted diamine 300g of N,N-dimethylformamide and 100g of glycidyl etherified lignin were placed in a dry three-necked flask, heated to 80℃, 120g of DOPO was added, stirred for 180min, cooled to 60℃, 60g of ethylenediamine was added, reacted for 60min, cooled with ice water, precipitated with ethanol, filtered, and dried under vacuum at 60℃ for 12h to obtain DOPO-lignin-grafted diamine. Step 3: Preparation of lignin-grafted amphoteric copolymer In a 500 mL three-necked flask, 80 g glycidyl etherified lignin, 20 g 4-cyano-4-(thiobenzoyl)valerate and 5 g potassium carbonate were added. The mixture was stirred at 60 °C for 180 min, and then heated to 70 °C. 100 g dodecyl methacrylate, 50 g dimethylaminoethyl methacrylate and 1 g 2,2'-azobisisobutyronitrile were added sequentially. The mixture was polymerized at 70 °C for 240 min under nitrogen protection. After the reaction was completed, the precipitate was separated and dried to obtain the lignin-grafted amphoteric copolymer. Step 4: Preparation of aspartic acid ester chain extender 200g of isophorone diamine and 400g of diethyl maleate were added to a dry three-necked flask and reacted at 60°C for 300 min under nitrogen protection to obtain aspartic acid ester chain extender. Step 5: Preparation of Component A Under a dry nitrogen atmosphere, 600g of hexamethylene diisocyanate trimer (Desmodur N3300A) and 200g of isophorone diisocyanate trimer butyl acetate solution (Desmodur Z 4470 BA, solid content approximately 70%) were mixed and stirred at room temperature for 30 minutes to obtain component A. Step 6: Preparation of Component B Under a dry nitrogen atmosphere, 580g of polyether diamine (JEFFAMINE D-2000), 80g of DOPO-lignin-grafted diamine, 80g of diethyltoluene diamine, 60g of aspartic acid ester chain extender, 2g of lignin-grafted amphoteric copolymer, 8g of γ-aminopropyltriethoxysilane, 5g of polyether-modified polysiloxane leveling agent (BYK-306), and 23g of potassium 2-ethylhexanoate solution (containing 3.0g of potassium 2-ethylhexanoate and 20.0g of propylene glycol methyl ether acetate) were stirred for 10 minutes to obtain component B. Component A and component B were mixed in a 1:1 weight ratio to obtain a wear-resistant and flame-retardant polyurea coating.

[0032] Coating preparation: Mix 1000g of component A and 1000g of component B, stir for 2 minutes, and apply to the surface of a clean Q235 steel substrate. Form a wet film with a thickness of 1.5mm using a roller coating method. After coating, level at room temperature for 15 minutes, then place in a 60℃ oven to cure for 90 minutes. Increase the temperature to 80℃ and continue curing for 60 minutes. Cool down to room temperature to obtain a wear-resistant and flame-retardant polyurea coating.

[0033] Example 2:

[0034] Step 1: Preparation of glycidyl etherified lignin Add 200g epichlorohydrin to a 500mL three-necked flask, stir at 60℃, add 50g alkali lignin powder (supplier Sigma-Aldrich, catalog number L330880), then add 5g tetrabutylammonium bromide as a phase transfer catalyst, stir for 60min, add 100g sodium hydroxide aqueous solution (concentration 50wt%) dropwise, maintain reaction at 60℃ for 120min, cool to room temperature, add deionized water to separate the phases, discard the aqueous phase, and recover unreacted epichlorohydrin under reduced pressure to obtain glycidyl etherified lignin; Step 2: Preparation of DOPO-lignin-grafted diamine 300g of N,N-dimethylformamide and 100g of glycidyl etherified lignin were placed in a dry three-necked flask, heated to 80℃, 120g of DOPO was added, stirred for 180min, cooled to 60℃, 60g of ethylenediamine was added, reacted for 60min, cooled with ice water, precipitated with ethanol, filtered, and dried under vacuum at 60℃ for 12h to obtain DOPO-lignin-grafted diamine. Step 3: Preparation of lignin-grafted amphoteric copolymer In a 500 mL three-necked flask, 80 g glycidyl etherified lignin, 20 g 4-cyano-4-(thiobenzoyl)valerate and 5 g potassium carbonate were added. The mixture was stirred at 60 °C for 180 min, and then heated to 70 °C. 100 g dodecyl methacrylate, 50 g dimethylaminoethyl methacrylate and 1 g 2,2'-azobisisobutyronitrile were added sequentially. The mixture was polymerized at 70 °C for 240 min under nitrogen protection. After the reaction was completed, the precipitate was separated and dried to obtain the lignin-grafted amphoteric copolymer. Step 4: Preparation of aspartic acid ester chain extender 200g of isophorone diamine and 400g of diethyl maleate were added to a dry three-necked flask and reacted at 60°C for 300 min under nitrogen protection to obtain aspartic acid ester chain extender. Step 5: Preparation of Component A Under a dry nitrogen atmosphere, 700g of hexamethylene diisocyanate trimer (Desmodur N3300A) and 300g of isophorone diisocyanate trimer butyl acetate solution (Desmodur Z 4470 BA, solid content approximately 70%) were mixed and stirred at room temperature for 30 minutes to obtain component A. Step 6: Preparation of Component B Under a dry nitrogen atmosphere, 620g of polyether diamine (JEFFAMINE D-2000), 100g of DOPO-lignin-grafted diamine, 100g of diethyltoluene diamine, 70g of aspartic acid ester chain extender, 3g of lignin-grafted amphoteric copolymer, 10g of γ-aminopropyltriethoxysilane, 5g of polyether-modified polysiloxane leveling agent (BYK-306), and 23g of potassium 2-ethylhexanoate solution (containing 3g of potassium 2-ethylhexanoate and 20g of propylene glycol methyl ether acetate) were stirred for 10 minutes to obtain component B. Component A and component B were mixed in a 1:1 weight ratio to obtain a wear-resistant and flame-retardant polyurea coating.

[0035] Coating preparation: Mix 1000g of component A and 1000g of component B, stir for 2 minutes, and coat the mixture onto the surface of a clean Q235 steel substrate. Form a 2mm thick wet film using a roller coating method. After coating, level the film at room temperature for 15 minutes, then place it in a 60℃ oven to cure for 120 minutes. Increase the temperature to 80℃ and continue curing for 90 minutes. Cool down to room temperature to obtain a wear-resistant and flame-retardant polyurea coating.

[0036] Example 3:

[0037] Step 1: Preparation of glycidyl etherified lignin Add 200g epichlorohydrin to a 500mL three-necked flask, stir at 60℃, add 50g alkali lignin powder (supplier Sigma-Aldrich, catalog number L330880), then add 5g tetrabutylammonium bromide as a phase transfer catalyst, stir for 60min, add 100g sodium hydroxide aqueous solution (concentration 50wt%) dropwise, maintain reaction at 60℃ for 120min, cool to room temperature, add deionized water to separate the phases, discard the aqueous phase, and recover unreacted epichlorohydrin under reduced pressure to obtain glycidyl etherified lignin; Step 2: Preparation of DOPO-lignin-grafted diamine 300g of N,N-dimethylformamide and 100g of glycidyl etherified lignin were placed in a dry three-necked flask, heated to 80℃, 120g of DOPO was added, stirred for 180min, cooled to 60℃, 60g of ethylenediamine was added, reacted for 60min, cooled with ice water, precipitated with ethanol, filtered, and dried under vacuum at 60℃ for 12h to obtain DOPO-lignin-grafted diamine. Step 3: Preparation of lignin-grafted amphoteric copolymer In a 500 mL three-necked flask, 80 g glycidyl etherified lignin, 20 g 4-cyano-4-(thiobenzoyl)valerate and 5 g potassium carbonate were added. The mixture was stirred at 60 °C for 180 min, and then heated to 70 °C. 100 g dodecyl methacrylate, 50 g dimethylaminoethyl methacrylate and 1 g 2,2'-azobisisobutyronitrile were added sequentially. The mixture was polymerized at 70 °C for 240 min under nitrogen protection. After the reaction was completed, the precipitate was separated and dried to obtain the lignin-grafted amphoteric copolymer. Step 4: Preparation of aspartic acid ester chain extender 200g of isophorone diamine and 400g of diethyl maleate were added to a dry three-necked flask and reacted at 60°C for 300 min under nitrogen protection to obtain aspartic acid ester chain extender. Step 5: Preparation of Component A Under a dry nitrogen atmosphere, 800g of hexamethylene diisocyanate trimer (Desmodur N3300A) and 400g of isophorone diisocyanate trimer butyl acetate solution (Desmodur Z 4470 BA, solid content approximately 70%) were mixed and stirred at room temperature for 30 minutes to obtain component A. Step 6: Preparation of Component B Under a dry nitrogen atmosphere, 660g of polyether diamine (JEFFAMINE D-2000), 120g of DOPO-lignin-grafted diamine, 120g of diethyltoluene diamine, 80g of aspartic acid ester chain extender, 5g of lignin-grafted amphoteric copolymer, 12g of γ-aminopropyltriethoxysilane, 5g of polyether-modified polysiloxane leveling agent (BYK-306), and 25g of potassium 2-ethylhexanoate solution (containing 3.3g of potassium 2-ethylhexanoate and 21.7g of propylene glycol methyl ether acetate) were stirred for 10 minutes to obtain component B. Component A and component B were mixed in a 1:1 weight ratio to obtain a wear-resistant and flame-retardant polyurea coating.

[0038] Coating preparation: Mix 1000g of component A and 1000g of component B, stir for 2 minutes, and apply to the surface of a clean Q235 steel substrate. Form a wet film with a thickness of 2.5mm using a roller coating method. After coating, level at room temperature for 15 minutes, then place in a 60℃ oven to cure for 150 minutes, raise the temperature to 80℃ and continue curing for 120 minutes, and then cool to room temperature to obtain a wear-resistant and flame-retardant polyurea coating.

[0039] Comparative Example 1: The difference between Comparative Example 1 and Example 2 is that 100g of DOPO-lignin grafted diamine in component B was replaced by 100g of polyether diamine (JEFFAMINE D-2000) in equal mass, while the other conditions were the same as in Example 2.

[0040] Comparative Example 2: The difference between Comparative Example 2 and Example 2 is that only 1000g of hexamethylene diisocyanate trimer (Desmodur N3300A) was used for component A, and the isophorone diisocyanate trimer butyl acetate solution was not added. The other conditions were the same as in Example 2.

[0041] Comparative Example 3: The difference between Comparative Example 3 and Example 2 is that 3g of lignin-grafted amphoteric copolymer was not added to component B, while the other conditions were the same as in Example 2.

[0042] Comparative Example 4: The difference between Comparative Example 4 and Example 2 is that 10g of γ-aminopropyltriethoxysilane was not added to component B, while the other conditions were the same as in Example 2.

[0043] Comparative Example 5: The difference between Comparative Example 5 and Example 2 is that 23g of potassium 2-ethylhexanoate solution was not added to component B, while the other conditions were the same as in Example 2.

[0044] Comparative Example 6: The difference between Comparative Example 6 and Example 2 is that 70g of aspartic acid ester chain extender in component B was replaced by 70g of diethyltoluene diamine in equal mass, while the other conditions were the same as in Example 2.

[0045] Performance testing: Test item 1: Infrared spectroscopy, using KBr pellets, scanning 4000-400cm. -1 .

[0046] Test Item 2: Thermogravimetric analysis. The coating is heated to 800℃ at a nitrogen gas flow rate of 50 mL / min and the temperature is increased by 10℃ / min. The temperature at which the mass loss is 5% is recorded. 5% The carbon residue at 700℃ was calculated, and the results are shown in Table 1.

[0047] Test item 3: Oxygen index and vertical combustion. The oxygen index was tested according to GB / T2406.2-2009, and the vertical combustion rating was tested according to GB / T2408-2021. The results are shown in Table 1.

[0048] Test item four: wear resistance. According to GB / T1768-2006, CS-17 grinding wheel, load 1kg, 1000 revolutions each, the mass loss was tested by weighing method to measure wear resistance. The results are shown in Table 1.

[0049] Test item 5: Pencil hardness, tested according to GB / T6739-2022, and the results are shown in Table 1.

[0050] Test item six: Adhesion, tested according to GB / T9286-2021, the results are shown in Table 1.

[0051] Table 1 Performance Test Results Sample T5% / ℃ 700℃ carbon residue rate / % Oxygen Index / % Vertical flammability rating Mass loss per 1000 revolutions / mg Pencil hardness Adhesion rating Example 1 290 18.9 28.6 V-1 32 2H Level 0 Example 2 288 21.4 31.2 V-0 21 3H Level 0 Example 3 283 23 30.5 V-0 24 3H Level 0 Comparative Example 1 291 0.8 21.8 No level 52 2H Level 1 Comparative Example 2 289 20.7 29.4 V-1 28 2H Level 0 Comparative Example 3 287 19.8 28.9 V-1 29 2H Level 0 Comparative Example 4 287 20.6 29.3 V-1 30 2H Level 2 Comparative Example 5 286 20.1 28.7 V-1 35 H Level 1 Comparative Example 6 293 19.6 28.9 V-2 38 4H Level 1 Data Analysis: The data from Examples 1-3 in Table 1 show that, with the enhanced synergistic effect of the phosphorus-containing aromatic structure and tertiary amine sites, the flame retardancy index and char residue of the material exhibit an overall upward trend. Simultaneously, a slight decrease in the initial thermal decomposition temperature was observed, reflecting a typical early weight loss-for-high-temperature char formation energy transfer mechanism. Regarding mechanical properties, abrasion resistance and hardness are optimal when the hard segment compound ratio is reached, indicating that the continuity of the isocyanurate structure and the phase micro-region size can be effectively controlled through fine adjustment of the ratio. The interface performance index remains consistently high, demonstrating that the amphoteric segments and silane coupling agent achieve good wettability and strong chemical anchoring on the metal substrate surface. Example 2 successfully achieved the optimal balance in the formulation design across char formation, hard segments, and interface: during the combustion stage, a complete expanded carbon layer provides flame retardant protection; during the abrasion stage, the hard segments fully bear the load without brittle fracture; and during environmental application, the interface exhibits excellent resistance to hydrolysis and thermal shock.

[0052] A comparison of data from Example 2 and Comparative Example 1 shows that after removing DOPO-lignin-grafted diamine, the self-extinguishing ability of the material significantly decreased, with the char residue almost dropping to zero. The fundamental reason for this significant deterioration is that the matrix lost its condensed-phase phosphorus-aromatic framework structure, making it unable to form a stable protective char layer at high temperatures; simultaneously, the lack of an effective gas-phase free radical capture pathway makes it difficult to interrupt the combustion chain reaction. Furthermore, the absence of the aromatic filling structure leads to a more concentrated and rapid thermal decomposition process, further increasing smoke density and dripping tendency. This confirms that the phosphorus-containing aromatic structure and nitrogen-containing active sites have a significant synergistic effect in smoke suppression and self-extinguishing.

[0053] The comparison between Example 2 and Comparative Example 2 shows that when only hexamethylene diisocyanate trimer is used, the wear resistance and vertical burning rating of the material both decline significantly. The underlying mechanism lies in the cyclic structure and asymmetric molecular configuration contributed by the isophorone diisocyanate trimer, which helps to construct a continuous hard segment microphase structure and enhance resistance to UV degradation. When this structural component is missing, although the hard segments maintain high hardness, their brittleness increases, microcracks propagate faster under wear stress, and the char layer formed during combustion is more prone to fracture failure.

[0054] A comparison of data from Example 2 and Comparative Example 3 shows that after removing the lignin-grafted amphoteric copolymer, the oxygen index and char residue decreased slightly, while the abrasion loss increased significantly. The mechanism lies in the fact that the presence of the amphoteric segments significantly improves the compatibility and dispersion uniformity between the matrix and filler components, which is beneficial for forming a denser pore structure and a continuous char layer during combustion. When this key component is missing, phase separation and stress concentration areas appear within the system, making it more susceptible to abrasion damage under external forces.

[0055] The comparison between Example 2 and Comparative Example 4 shows that without the addition of γ-aminopropyltriethoxysilane, the coating adhesion dropped sharply from excellent to poor. The mechanism of this significant difference lies in the fact that the absence of the silane coupling agent leads to a substantial reduction in the participation of hydroxyl groups on the metal substrate surface, insufficient interfacial chemical bonding strength, and incomplete construction of the inorganic-organic transition layer. Under the influence of thermal cycling and shear stress, the coating is more prone to peeling failure, thus affecting the continuity and protective effect of the char layer during combustion.

[0056] Data from Example 2 and Comparative Example 5 show that removing the potassium 2-ethylhexanoate catalyst resulted in insufficient hard segment trimerization, leading to decreased surface hardness and significantly increased wear. The fundamental mechanism is that the absence of the catalyst limits the self-trimerization process of the isocyanate, resulting in a decrease in both the density of the network structure and the glass transition temperature. During the wear stage, the material exhibits more plastic flow characteristics, and its wear resistance is significantly weakened.

[0057] The comparison between Example 2 and Comparative Example 6 reveals a typical negative synergistic effect of hardness without toughness: replacing aspartic acid ester with diethyltoluene diamine in equal amounts improves the apparent hardness, but simultaneously deteriorates the vertical burning rating and abrasion performance. The underlying mechanism lies in the introduction of the highly reactive component, which generates significant internal stress and obvious phase separation, further amplifying the resulting embrittlement microcracks during frictional stress and combustion expansion. This comparison fully demonstrates the crucial regulatory role of aspartic acid ester in the formation of slow-release hard segments and the control of interfacial stress.

[0058] from Figure 2 It can be seen that alkali lignin is at 3350cm -1 Broad peak and 1600 / 1510cm -1 Aromatic rings predominate; glycidyl etherified lignin appears at 1250 cm⁻¹ -1 1100cm -1 and 910 / 850cm -1 Epoxy characteristics and weakened OH; DOPO-lignin grafted diamine 910 / 850 cm -1 Significantly reduced to invisible, and 1205cm appeared. -1 (P=O), 980cm -1 (PO-Ar) and NH-related peaks; lignin-grafted amphoteric copolymer at 1730 cm⁻¹ -1 Ester carbonyl group and 2920 / 2850cm -1 The alkyl CH groups are significantly enhanced, with a length of 1160-1190 cm⁻¹. -1 The simultaneous enhancement of the CO band demonstrates the successful synthesis of glycidyl etherified lignin, DOPO-lignin-grafted diamine, and lignin-grafted amphoteric copolymers.

[0059] Those skilled in the art should understand that the discussion of any of the above embodiments is merely exemplary and is not intended to imply that the scope of the invention is limited to these examples; within the framework of the invention, the technical features of the above embodiments or different embodiments can also be combined, the steps can be implemented in any order, and there are many other variations of the different aspects of the invention as described above, which are not provided in detail for the sake of brevity.

Claims

1. A wear-resistant and flame-retardant polyurea coating, comprising component A and component B, characterized in that, Component A and component B are prepared in a weight ratio of 1:1; by weight parts: Component A comprises: 600-800 parts of hexamethylene diisocyanate trimer and 200-400 parts of isophorone diisocyanate trimer butyl acetate solution. Component B comprises: 580-660 parts of polyether diamine, 80-120 parts of DOPO (9,10-dihydro-9-oxo-10-phosphaphenanthrene-10-oxide)-lignin grafted diamine, 80-120 parts of diethyltoluene diamine, 60-80 parts of aspartic acid ester chain extender, 2-5 parts of lignin grafted amphoteric copolymer, 8-12 parts of γ-aminopropyltriethoxysilane, 4-6 parts of polyether-modified polysiloxane leveling agent, and 23-25 ​​parts of potassium 2-ethylhexanoate solution; The DOPO-lignin-grafted diamine was prepared by the following method: glycidyl etherified lignin and DOPO were reacted in N,N-dimethylformamide at 80°C for 180 min, and then reacted with ethylenediamine at 60°C for 60 min. The lignin-grafted amphoteric copolymer was prepared by polymerizing glycidyl etherified lignin with dodecyl methacrylate and dimethylaminoethyl methacrylate in the presence of 4-cyano-4-(thiobenzoyl)valerate and potassium carbonate, with 2,2'-azobisisobutyronitrile as an initiator, at 70°C for 240 min. The aspartic acid ester chain extender was prepared by reacting isophorone diamine with diethyl maleate under nitrogen protection at 60°C for 300 min.

2. The wear-resistant and flame-retardant polyurea coating according to claim 1, characterized in that, The hexamethylene diisocyanate trimer is designated as Desmodur N3300A; the isophorone diisocyanate trimer butyl acetate solution is designated as Desmodur Z 4470 BA; the polyether diamine is designated as JEFFAMINE D-2000; and the polyether-modified polysiloxane leveling agent is designated as BYK-306.

3. The wear-resistant and flame-retardant polyurea coating according to claim 1, characterized in that, The potassium 2-ethylhexanoate solution was prepared by mixing potassium 2-ethylhexanoate and propylene glycol methyl ether acetate in a weight ratio of 3.0-3:20.0-21.

7.

4. The wear-resistant and flame-retardant polyurea coating according to claim 1, characterized in that, The glycidyl etherified lignin was prepared by reacting alkali lignin with epichlorohydrin at 60°C for 120 min under the catalysis of tetrabutylammonium bromide and in the presence of sodium hydroxide; the weight ratio of alkali lignin, epichlorohydrin, tetrabutylammonium bromide and sodium hydroxide aqueous solution was 50:200:5:100; the concentration of sodium hydroxide aqueous solution was 50 wt%.

5. The wear-resistant and flame-retardant polyurea coating according to claim 1, characterized in that, The weight ratio of glycidyl etherified lignin, DOPO, N,N-dimethylformamide and ethylenediamine in the raw materials for preparing DOPO-lignin grafted diamine is 100:120:300:

60.

6. The wear-resistant and flame-retardant polyurea coating according to claim 1, characterized in that, The weight ratio of glycidyl etherified lignin, dodecyl methacrylate, dimethylaminoethyl methacrylate, 4-cyano-4-(thiobenzoyl)valerate, potassium carbonate, and 2,2'-azobisisobutyronitrile in the raw materials for preparing the lignin graft amphoteric copolymer is 80:100:50:20:5:

1.

7. The wear-resistant and flame-retardant polyurea coating according to claim 1, characterized in that, The weight ratio of isophorone diamine and diethyl maleate in the raw materials for preparing the aspartic ester chain extender is 200:

400.

8. A method for preparing a wear-resistant and flame-retardant polyurea coating according to any one of claims 1-7, characterized in that, Includes the following steps: (1) Preparation of DOPO-lignin-grafted diamine, lignin-grafted amphoteric copolymer and aspartic acid ester chain extender; (2) Preparation of component A: Mix hexamethylene diisocyanate trimer with isophorone diisocyanate trimer butyl acetate solution and stir at room temperature for 30 min; (3) Preparation of component B: Mix polyether diamine, DOPO-lignin grafted diamine, diethyltoluene diamine, aspartic acid ester chain extender, lignin grafted amphoteric copolymer, γ-aminopropyltriethoxysilane, polyether modified polysiloxane leveling agent and potassium 2-ethylhexanoate solution and stir for 10 min; (4) Prepare a wear-resistant and flame-retardant polyurea coating by mixing component A and component B in a weight ratio of 1:

1.

9. The wear-resistant and flame-retardant polyurea coating according to claim 1, characterized in that, Mix components A and B for 2 minutes and then apply the mixture to the substrate surface. Level the mixture at room temperature for 15 minutes, then cure it at 60°C for 90-150 minutes. Increase the temperature to 80°C and continue curing for 60-120 minutes. Cool the mixture to room temperature to obtain a wear-resistant and flame-retardant polyurea coating.

10. The wear-resistant and flame-retardant polyurea coating according to claim 9, characterized in that, The thickness of the wet film after coating onto the substrate surface is 1.5-2.5 mm.

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