Flame-retardant polyurea composite material, and preparation method and application thereof

Abstract

The application discloses a kind of flame-retardant polyurea composite material and its preparation method and application, belong to polyurea elastomer material preparation technical field.The raw material of flame-retardant polyurea composite material of the present application comprises component A and component B;The component A is obtained by the reaction of aromatic isocyanate and polyether polyol, and the aromatic isocyanate comprises diphenylmethane diisocyanate and isophorone diisocyanate;Component B comprises polyether amine and bisamine chain extender.The synergistic effect of aromatic and alicyclic structure produced by MDI and IPDI compounding significantly improves the thermal stability of polyurea material of the present application at high temperature.The limiting oxygen index of the product is further improved by the modification of MgAl-LDHs nanoparticles, and the finally obtained polyurea composite material with excellent flame retardancy and good mechanical properties has wide application prospect in the protection field under severe fire hazard environment.

Description

Technical Field

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

[0002] With the continuous advancement of industrialization, the requirements for flame-retardant fire protection technology are also increasing. The hazards caused by combustion accidents are multidimensional and interconnected. In addition to direct personal injury and property damage, they can further lead to a series of secondary disasters, such as fires, poisoning, and environmental pollution. These secondary disasters have long-term and profound impacts on society and the ecological environment. Therefore, taking effective preventative measures against combustion accidents is particularly crucial.

[0003] From the perspective of combustion characteristics, effectively resisting the damage caused by high combustion temperatures can greatly reduce or even eliminate the overall harm caused by combustion accidents. Polyurea materials are widely used in the field of protection due to their excellent mechanical properties, but due to their inherent chemical structure and all-organic framework characteristics, they exhibit poor flame retardancy, with a limiting oxygen index (LOI) typically below 20%. This inherent flammability makes them extremely easy to ignite in combustion environments, severely limiting the applicability of polyurea materials in applications with high fire safety standards.

[0004] Therefore, further enhancing the fire resistance and flame retardancy of polyurea materials is of great significance for expanding their applicability in harsh fire environments. Summary of the Invention

[0005] The purpose of this invention is to provide a flame-retardant polyurea composite material, its preparation method, and its applications, thereby addressing the aforementioned problems in the background art. This invention significantly improves the thermal stability of the polyurea material at high temperatures through the synergistic effect of the aromatic and alicyclic structures produced by the compounding of MDI and IPDI. The limiting oxygen index of the product is further improved through the modification effect of MgAl-LDHs nanoparticles. The resulting polyurea composite material possesses both excellent flame retardancy and good mechanical properties, showing broad application prospects in the field of protection against harsh fire environments.

[0006] To achieve the above objectives, the present invention provides the following technical solution: One of the technical solutions of this invention is to provide a flame-retardant polyurea composite material, wherein the raw material contains component A and component B; Component A is prepared by reacting aromatic isocyanate with polyether polyol, wherein the aromatic isocyanate contains diphenylmethane diisocyanate and isophorone diisocyanate. Component B contains polyetheramine and diamine chain extender.

[0007] When diphenylmethane diisocyanate (MDI) is used alone to prepare polyurea, the system's reactivity is too high and the gel time is too short, resulting in a significant decrease in material flowability. This makes it difficult to cast and mold, and obtain samples with regular dimensions. Furthermore, poor reaction uniformity leads to obvious defects inside the product. Conversely, when isophorone diisocyanate (IPDI) is used alone, although the flowability is good, the system's reaction rate is slow, and the cured product is prone to cracking after standing for several days. Moreover, its mechanical properties are significantly reduced compared to MDI-based polyurea.

[0008] Preferably, the raw materials of the flame-retardant polyurea composite material also contain magnesium aluminum hydrotalcite (MgAl-LDHs).

[0009] Preferably, the amount of magnesium aluminum hydrotalcite added to the flame-retardant polyurea composite material is 1.0-2.0 wt%.

[0010] Preferably, the mass ratio of component A to component B is 59-60.9:36.7.

[0011] Preferably, the mass ratio of the aromatic isocyanate to the polyether polyol is 30.8-40:35-43.

[0012] Preferably, the mass ratio of diphenylmethane diisocyanate to isophorone diisocyanate is 1:1.

[0013] DMTDA contains thioether groups, and although it is an aromatic amine, its reactivity is relatively lower than that of conventional materials such as DETDA (diethyltoluene diamine). Its sulfur atoms provide weak polarity, promoting microphase separation while preventing excessively rapid curing. MDBA, as a sterically hindered aromatic secondary amine, has lower reactivity than DETDA and DMTDA, and can be used in the synthesis of polyurea to reduce the reaction rate, increase the gel time, and achieve better leveling properties. Therefore, by using these two amine chain extenders specified in this invention, the curing speed of polyurea can be adjusted and the microstructure optimized.

[0014] Preferably, the polyetheramine is polyoxypropylene diamine.

[0015] Preferably, the mass ratio of the polyetheramine to the diamine chain extender is 30:17.

[0016] Preferably, the diamine chain extender comprises dimethylthiotoluenediamine and 4,4'-methylenebis(N-(sec-butyl)aniline); the mass ratio of dimethylthiotoluenediamine to 4,4'-methylenebis(N-(sec-butyl)aniline) is 10:7.

[0017] The second technical solution of the present invention provides a method for preparing the above-mentioned flame-retardant polyurea composite material, comprising the following steps: Magnesium aluminum hydrotalcite was mixed with polyether polyol, and then aromatic isocyanate was added. The mixture was reacted under a protective atmosphere at 80°C to obtain component A. Component B is obtained by mixing polyetheramine and diamine chain extender; Components A and B are mixed and cured to prepare the flame-retardant polyurea composite material.

[0018] Preferably, the preparation method includes the following steps: Magnesium aluminum hydrotalcite was added to polyether polyol, and the mixture was ultrasonically dispersed for 10 min using a high-speed homogenizer to ensure that the nanoparticles were fully and uniformly dispersed in the polyol, with no obvious particle aggregation or precipitation in the mixture. The mixture was then transferred to a dry three-necked flask equipped with a vacuum interface, heated to 120°C, and stirred uniformly (magnetic stirrer speed 400-500 r / min). The vacuum pump was then turned on, and water was removed under a vacuum of -0.1 MPa for 2-3 h until the water content was ≤0.05wt%. The raw material system was cooled to 60°C, the vacuum was released with dry nitrogen, aromatic isocyanate was added, stirred evenly, and the temperature was raised to 80°C and reacted under nitrogen protection. During the reaction, the isocyanate content of the system was measured every 1 h using the di-n-butylamine-toluene method. The reaction was stopped when the isocyanate content approached 15%. The system was then evacuated for 0.5 h to remove residual bubbles and low-boiling substances, cooled to room temperature, and sealed and stored under a nitrogen atmosphere to obtain component A. Polyetheramine and diamine chain extender were added to a dry three-necked flask, heated to 90°C and stirred for 1.5 h to obtain a mixed system; the mixed system was heated to 120°C, a vacuum pump was turned on, and water was removed under a vacuum of -0.1 MPa for 2 h (water content ≤0.05 wt%), and then cooled to room temperature to obtain component B; Add components A and B to a beaker and stir rapidly with a glass rod for 15-20 seconds. Then pour the mixture into a polytetrafluoroethylene mold and gently shake the mold to evenly spread the polyurea solution across the mold surface. Allow the mixture to stand at room temperature for 48-72 hours to cure, thus completing the preparation.

[0019] The MgAl-LDHs were first dispersed in the reaction raw material of component A using ultrasonic dispersion. The prepolymer component A containing urethane groups was used as a modifier for the MgAl-LDHs to further improve its dispersion uniformity in polyurea.

[0020] The second technical solution of the present invention provides an application of the above-mentioned flame-retardant polyurea composite material in the field of flame retardancy.

[0021] The beneficial technical effects of the present invention are as follows: This invention utilizes a blend of MDI and IPDI to prepare polyurea. The rigid benzene rings in the MDI molecule facilitate the formation of a dense and continuous char layer during high-temperature pyrolysis. This char layer acts as a physical barrier, effectively inhibiting heat transfer into the matrix and blocking the diffusion paths of oxygen and combustible volatiles. Simultaneously, the cyclohexyl structure in the IPDI molecule possesses high thermo-oxidative stability, which can slow down the thermal decomposition process of the polyurea matrix. The synergistic effect of the aromatic and alicyclic structures produced by the blend significantly enhances the thermal stability of the polyurea material at high temperatures and exhibits excellent flame retardant properties.

[0022] This invention uses MgAl-LDHs nanoparticles to composite modify polyurea. When heated, the polyurea can dilute the flammable decomposition products to a certain extent, and the inorganic residues formed after decomposition help to further improve the integrity and stability of the char layer, thereby giving the material excellent synergistic flame retardant effect. The limiting oxygen index increases continuously with the increase of the amount added.

[0023] Furthermore, the introduction of MgAl-LDHs transforms the polyurea material of this invention from a brittle fracture mechanism to a ductile deformation mechanism, significantly increasing the elongation at break and improving the material's plastic deformation capability while maintaining a certain mechanical strength.

[0024] The preparation process of this invention is simple and the raw materials are readily available. The resulting composite material has both excellent flame retardancy and good mechanical properties, and has broad application prospects in the field of protection in harsh fire environments. Attached Figure Description

[0025] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0026] Figure 1 The stress-strain curves are for the polyurea composite materials of Examples 3 and 6-8.

[0027] Figure 2 The limiting oxygen index test results are for the polyurea composite materials of Examples 3 and 6-8. Detailed Implementation

[0028] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention. It should be understood that the terminology used in this invention is merely for describing particular embodiments and is not intended to limit the present invention.

[0029] Furthermore, regarding the numerical ranges in this invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Any stated value or intermediate value within a stated range, as well as each smaller range between any other stated value or intermediate value within said range, are also included in this invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0030] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. While only preferred methods and materials have been described herein, any methods and materials similar or equivalent to those described herein may be used in the implementation or testing of this invention. It should be noted that any aspects of this invention not described in detail are conventional practices in the art and are not the focus of this invention.

[0031] The terms “comprising,” “including,” “having,” “containing,” etc., used in this invention are all open-ended terms, meaning that they include but are not limited to.

[0032] The main raw materials used in the following embodiments and comparative examples of the present invention and their sources are shown below: Liquefied MDI: WANNATE ® MDI-50 (diphenylmethane diisocyanate), purity ≥99.6%, a commercially available product of Wanhua Chemical Group Co., Ltd. Isophorone diisocyanate (IPDI): 99% purity, commercially available product from Shanghai Maclean Biochemical Technology Co., Ltd. Polyether polyol (PPG): PPG-2000, a commercially available product of Shanghai Aladdin Biochemical Technology Co., Ltd. Polypropylene diamine: D2000, a commercially available product of Shanghai Aladdin Biochemical Technology Co., Ltd.; 4,4'-Methylenebis(N-(sec-butyl)aniline) (MDBA): Purity ≥97%, commercially available product of Shanghai Aladdin Biochemical Technology Co., Ltd. Dimethylthiotoluene diamine (DMTDA): 99.5% purity, commercially available product of Shanghai Maclean Biochemical Technology Co., Ltd. Antioxidant 1135: Purity ≥98%, commercially available product from Shanghai Yuanye Biotechnology Co., Ltd. Isopropanol: 99.9% purity, commercially available product from Shanghai Maclean Biochemical Technology Co., Ltd. Di-n-butylamine: Purity ≥ 99.0%, commercially available product from Sinopharm Chemical Reagent Co., Ltd.; Toluene: Purity ≥ 99.0%, commercially available product from Sinopharm Chemical Reagent Co., Ltd. Bromocresol green-ethanol solution: 0.1 wt%, commercially available product from Beijing Chemical Glass Station Bioanalytical Technology Co., Ltd.

[0033] Prepolymer isocyanate content (NCO%) titration: The basic principle of isocyanate content (NCO%) determination is that isocyanates in the sample react with di-n-butylamine solution to form urea, and then excess di-n-butylamine is titrated with standard hydrochloric acid solution. The specific steps are as follows: First, place 1.0 g of the prepolymer sample to be tested into an Erlenmeyer flask. Then, measure 20.00 mL of a 1 mol / L di-n-butylamine-toluene solution into the Erlenmeyer flask, mix thoroughly, and let stand for 25-30 min. Next, add 40-50 mL of isopropanol to the Erlenmeyer flask, followed by 2-3 drops of a 0.1 wt% bromocresol green-ethanol solution. Finally, titrate with a standard hydrochloric acid solution (1 mol / L). The titration endpoint is reached when the solution changes from blue to yellow. A blank control group should be set up and titrated using the same procedure. The formula for calculating the isocyanate content (NCO%) is shown below: In the formula, V1 is the amount of standard hydrochloric acid solution consumed by the prepolymer sample to be tested (mL); V0 is the amount of standard hydrochloric acid solution consumed by the blank sample (mL); C is the actual concentration of the standard hydrochloric acid solution (mol / L); and m is the sample mass (g), accurate to 0.001 g when weighing.

[0034] The test conditions for the flame retardant and mechanical properties of flame-retardant polyurea materials are as follows: Mechanical property tests were conducted using a Shimadzu universal testing machine (AGS-X-50N) from Japan. In accordance with the GB / T528-2009 standard, the polyurea was prepared into a dumbbell shape for tensile property testing, with a loading rate of 100 mm / min. Flame retardant performance testing was conducted using the limiting oxygen index of British FTT0077, according to GB / T 2406.2-2009 standard. The polyurea sample was cut into 15 80-degree segments. 10 5mm 3 Limiting oxygen index test of splines All raw materials used in the following embodiments and comparative examples of the present invention are commercially available products.

[0035] Example 1 A method for preparing a flame-retardant polyurea material, comprising the following steps: (1) Add 35 g of PPG-2000 to a dry three-necked flask equipped with a vacuum port, heat to 120°C and stir evenly (magnetic speed of 500 r / min), then turn on the vacuum pump and remove water under vacuum conditions of -0.1 MPa for 2~3 h (so that the water content is ≤0.05 wt%). (2) Cool the raw material system to 60°C, remove the vacuum with dry nitrogen, add 29.5 g of MDI-50, stir evenly, heat to 80°C and react under nitrogen protection; during the reaction, the isocyanate content (NCO%) of the system is measured every 1 h using the di-n-butylamine-toluene method. When the NCO% is close to the theoretical value (15%), stop the reaction. Then, vacuum the system for 0.5 h to remove residual bubbles and low-boiling substances, cool to room temperature and remove, seal and store under nitrogen atmosphere to obtain component A; (3) Weigh 30 g D2000, 10 g DMTDA, 7 g MDBA and 1 g antioxidant 1135, add them to a dry three-necked flask, heat to 90℃ and stir evenly for 1.5 h to obtain a mixed system; (4) Heat the mixture from step (3) to 120°C, turn on the vacuum pump, remove water for 2 h under a vacuum of -0.1 MPa (water content ≤0.05 wt%), and then cool to room temperature to obtain component B; (5) Measure 59 g of component A and 36.7 g of component B and add them to a beaker. Stir rapidly with a glass rod for 15-20 s, then pour into a polytetrafluoroethylene mold and let it stand at room temperature for 72 h to cure, obtaining the M100-I0 type polyurea product using only MDI-50. The limiting oxygen index (LOI) of the product in this example was measured to be 19.9%.

[0036] Example 2 A method for preparing a flame-retardant polyurea material, comprising the following steps: (1) Add 35 g of PPG-2000 to a dry three-necked flask equipped with a vacuum port, heat to 120°C and stir evenly (magnetic speed of 500 r / min), then turn on the vacuum pump and remove water under vacuum conditions of -0.1 MPa for 2~3 h (so that the water content is ≤0.05 wt%). (2) The raw material system was cooled to 60°C, the vacuum was released with dry nitrogen, 7.7 g of MDI-50 and 23.1 g of IPDI were added, stirred evenly, and the temperature was raised to 80°C and reacted under nitrogen protection. During the reaction, the isocyanate content (NCO%) of the system was measured every 1 h using the di-n-butylamine-toluene method. The reaction was stopped when the NCO% was close to the theoretical value (15%). The system was then evacuated for 0.5 h to remove residual bubbles and low-boiling substances. After cooling to room temperature, the system was sealed and stored under a nitrogen atmosphere to obtain component A. (3) Weigh 30 g D2000, 10 g DMTDA, 7 g MDBA and 1 g antioxidant 1135, add them to a dry three-necked flask, heat to 90℃ and stir evenly for 1.5 h to obtain a mixed system; (4) Heat the mixture from step (3) to 120°C, turn on the vacuum pump, remove water for 2 h under a vacuum of -0.1 MPa (water content ≤0.05 wt%), and then cool to room temperature to obtain component B; (5) Measure 59 g of component A and 36.7 g of component B and add them to a beaker. Stir quickly with a glass rod for 15-20 s, then pour into a polytetrafluoroethylene mold and let it stand at room temperature for 72 h to cure, thus obtaining the M25-I75 type polyurea product.

[0037] Example 3 A method for preparing a flame-retardant polyurea material, comprising the following steps: (1) Add 35 g of PPG-2000 to a dry three-necked flask equipped with a vacuum port, heat to 120°C and stir evenly (magnetic speed of 500 r / min), then turn on the vacuum pump and remove water under vacuum conditions of -0.1 MPa for 2~3 h (so that the water content is ≤0.05 wt%). (2) The raw material system was cooled to 60°C, the vacuum was released with dry nitrogen, 16.2 g of MDI-50 and 16.2 g of IPDI were added, stirred evenly, and the temperature was raised to 80°C and reacted under nitrogen protection. During the reaction, the isocyanate content (NCO%) of the system was measured every 1 h using the di-n-butylamine-toluene method. The reaction was stopped when the NCO% was close to the theoretical value (15%). The system was then evacuated for 0.5 h to remove residual bubbles and low-boiling substances. After cooling to room temperature, the system was sealed and stored under a nitrogen atmosphere to obtain component A. (3) Weigh 30 g D2000, 10 g DMTDA, 7 g MDBA and 1 g antioxidant 1135, add them to a dry three-necked flask, heat to 90℃ and stir evenly for 1.5 h to obtain a mixed system; (4) Heat the mixture from step (3) to 120°C, turn on the vacuum pump, remove water for 2 h under a vacuum of -0.1 MPa (water content ≤0.05 wt%), and then cool to room temperature to obtain component B; (5) Measure 59 g of component A and 36.7 g of component B and add them to a beaker. Stir quickly with a glass rod for 15-20 s, then pour into a polytetrafluoroethylene mold and let it stand at room temperature for 72 h to cure, thus obtaining M50-I50 type polyurea product.

[0038] Example 4 A method for preparing a flame-retardant polyurea material, comprising the following steps: (1) Add 35 g of PPG-2000 to a dry three-necked flask equipped with a vacuum port, heat to 120°C and stir evenly (magnetic speed of 500 r / min), then turn on the vacuum pump and remove water under vacuum conditions of -0.1 MPa for 2~3 h (so that the water content is ≤0.05 wt%). (2) The raw material system was cooled to 60°C, the vacuum was released with dry nitrogen, 25.7 g of MDI-50 and 8.6 g of IPDI were added, stirred evenly, and the temperature was raised to 80°C and reacted under nitrogen protection. During the reaction, the isocyanate content (NCO%) of the system was measured every 1 h using the di-n-butylamine-toluene method. The reaction was stopped when the NCO% was close to the theoretical value (15%). The system was then evacuated for 0.5 h to remove residual bubbles and low-boiling substances, cooled to room temperature, and sealed and stored under a nitrogen atmosphere to obtain component A. (3) Weigh 30 g D2000, 10 g DMTDA, 7 g MDBA and 1 g antioxidant 1135, add them to a dry three-necked flask, heat to 90℃ and stir evenly for 1.5 h to obtain a mixed system; (4) Heat the mixture from step (3) to 120°C, turn on the vacuum pump, remove water for 2 h under a vacuum of -0.1 MPa (water content ≤0.05 wt%), and then cool to room temperature to obtain component B; (5) Measure 59 g of component A and 36.7 g of component B and add them to a beaker. Stir quickly with a glass rod for 15-20 s, then pour into a polytetrafluoroethylene mold and let it stand at room temperature for 72 h to cure, thus obtaining the M75-I25 type polyurea product.

[0039] Example 5 A method for preparing a flame-retardant polyurea material, comprising the following steps: (1) Add 35 g of PPG-2000 to a dry three-necked flask equipped with a vacuum port, heat to 120°C and stir evenly (magnetic speed of 500 r / min), then turn on the vacuum pump and remove water under vacuum conditions of -0.1 MPa for 2~3 h (so that the water content is ≤0.05 wt%). (2) The raw material system was cooled to 60°C, the vacuum was released with dry nitrogen, 36.2 g of IPDI was added, stirred evenly, and the temperature was raised to 80°C and reacted under nitrogen protection. During the reaction, the isocyanate content (NCO%) of the system was measured every 1 h using the di-n-butylamine-toluene method. The reaction was stopped when the NCO% was close to the theoretical value (15%). The system was then evacuated for 0.5 h to remove residual bubbles and low-boiling substances. After cooling to room temperature, the system was sealed and stored under a nitrogen atmosphere to obtain component A. (3) Weigh 30 g D2000, 10 g DMTDA, 7 g MDBA and 1 g antioxidant 1135, add them to a dry three-necked flask, heat to 90℃ and stir evenly for 1.5 h to obtain a mixed system; (4) Heat the mixture from step (3) to 120°C, turn on the vacuum pump, remove water for 2 h under a vacuum of -0.1 MPa (water content ≤0.05 wt%), and then cool to room temperature to obtain component B; (5) Measure 59 g of component A and 36.7 g of component B and add them to a beaker. Stir quickly with a glass rod for 15-20 s, then pour into a polytetrafluoroethylene mold and let it stand at room temperature for 72 h to cure, thus obtaining the MO-I100 type polyurea product using only IPDI.

[0040] Example 6 A method for preparing a flame-retardant hydrotalcite polyurea composite material, comprising the following steps: (1) 1.35 g of MgAl-LDHs (purchased from Shanghai Maclean Biochemical Technology Co., Ltd.) was added to 43 g of PPG2000. The mixture was ultrasonically dispersed for 10 min using a high-speed homogenizer to ensure that the nanoparticles were fully and uniformly dispersed in the polyol and that there was no obvious particle aggregation or precipitation in the mixture. (2) Then, the mixture from step (1) is transferred to a dry three-necked flask equipped with a vacuum port, heated to 120°C and stirred evenly (magnetic spinner speed is 500 r / min), and then the vacuum pump is turned on to remove water under vacuum conditions of -0.1 MPa for 2~3 h (so that the water content is ≤0.05 wt%). (3) Cool the raw material system to 60°C, remove the vacuum with dry nitrogen, add 20 g of MDI-50 and 20 g of IPDI, stir evenly, heat to 80°C and react under nitrogen protection. During the reaction, the isocyanate content (NCO%) of the system is measured every 1 h using the di-n-butylamine-toluene method. When the NCO% is close to the theoretical value (15%), stop the reaction. Then, vacuum the system for 0.5 h to remove residual bubbles and low-boiling substances, cool to room temperature, and seal and store under nitrogen atmosphere to obtain component A; (4) Weigh 30 g D2000, 10 g DMTDA and 7 g MDBA, add them to a dry three-necked flask, heat to 90℃ and stir evenly for 1.5 h to obtain a mixed system; (5) Heat the mixture from step (4) to 120°C, turn on the vacuum pump, remove water for 2 h under a vacuum of -0.1 MPa (water content ≤0.05 wt%), and then cool to room temperature to obtain component B; (6) Measure 59 g of component A and 36.7 g of component B and add them to a beaker. Stir quickly with a glass rod for 15-20 s, then pour into a polytetrafluoroethylene mold and let stand at room temperature for 72 h to cure, to obtain 1.0wt%MgAl-LDHs modified polyurea product (denoted as 1.0%MgAl-LDHs@MIPUA).

[0041] Example 7 A method for preparing a flame-retardant hydrotalcite polyurea composite material, comprising the following steps: (1) 2.02 g of MgAl-LDHs were added to 43 g of PPG2000, and the mixture was ultrasonically dispersed for 10 min using a high-speed homogenizer to ensure that the nanoparticles were fully and uniformly dispersed in the polyol and that there was no obvious particle aggregation or precipitation in the mixture. (2) Then, the mixture from step (1) is transferred to a dry three-necked flask equipped with a vacuum port, heated to 120°C and stirred evenly (magnetic spinner speed is 500 r / min), and then the vacuum pump is turned on to remove water under vacuum conditions of -0.1 MPa for 2~3 h (so that the water content is ≤0.05 wt%). (3) Cool the raw material system to 60°C, remove the vacuum with dry nitrogen, add 20 g of MDI-50 and 20 g of IPDI, stir evenly, heat to 80°C and react under nitrogen protection. During the reaction, the isocyanate content (NCO%) of the system is measured every 1 h using the di-n-butylamine-toluene method. When the NCO% is close to the theoretical value (15%), stop the reaction. Then, vacuum the system for 0.5 h to remove residual bubbles and low-boiling substances, cool to room temperature, and seal and store under nitrogen atmosphere to obtain component A; (4) Weigh 30 g D2000, 10 g DMTDA and 7 g MDBA, add them to a dry three-necked flask, heat to 90℃ and stir evenly for 1.5 h to obtain a mixed system; (5) Heat the mixture from step (4) to 120°C, turn on the vacuum pump, remove water for 2 h under a vacuum of -0.1 MPa (water content ≤0.05 wt%), and then cool to room temperature to obtain component B; (6) Measure 60.4 g of component A and 36.7 g of component B and add them to a beaker. Stir quickly with a glass rod for 15-20 s, then pour into a polytetrafluoroethylene mold and let it stand at room temperature for 72 h to cure, to obtain a 1.5wt%MgAl-LDHs modified polyurea product (denoted as 1.5%MgAl-LDHs@MIPUA).

[0042] Example 8 A method for preparing a flame-retardant hydrotalcite polyurea composite material, comprising the following steps: (1) 2.7 g of MgAl-LDHs were added to 43 g of PPG2000, and the mixture was ultrasonically dispersed for 10 min using a high-speed homogenizer to ensure that the nanoparticles were fully and uniformly dispersed in the polyol and that there was no obvious particle aggregation or precipitation in the mixture. (2) Then, the mixture from step (1) is transferred to a dry three-necked flask equipped with a vacuum port, heated to 120°C and stirred evenly (magnetic spinner speed is 500 r / min), and then the vacuum pump is turned on to remove water under vacuum conditions of -0.1 MPa for 2~3 h (so that the water content is ≤0.05 wt%). (3) Cool the raw material system to 60°C, remove the vacuum with dry nitrogen, add 20 g of MDI-50 and 20 g of IPDI, stir evenly, heat to 80°C and react under nitrogen protection. During the reaction, the isocyanate content (NCO%) of the system is measured every 1 h using the di-n-butylamine-toluene method. When the NCO% is close to the theoretical value (15%), stop the reaction. Then, vacuum the system for 0.5 h to remove residual bubbles and low-boiling substances, cool to room temperature, and seal and store under nitrogen atmosphere to obtain component A; (4) Weigh 30 g D2000, 10 g DMTDA and 7 g MDBA, add them to a dry three-necked flask, heat to 90℃ and stir evenly for 1.5 h to obtain a mixed system; (5) Heat the mixture from step (4) to 120°C, turn on the vacuum pump, remove water for 2 h under a vacuum of -0.1 MPa (water content ≤0.05 wt%), and then cool to room temperature to obtain component B; (6) Measure 60.9 g of component A and 36.7 g of component B and add them to a beaker. Stir quickly with a glass rod for 15-20 s, then pour into a polytetrafluoroethylene mold and let stand at room temperature for 72 h to cure, to obtain 2.0wt%MgAl-LDHs modified polyurea product (denoted as 2.0%MgAl-LDHs@MIPUA).

[0043] Effect verification 1. Tensile properties were tested on the hydrotalcite polyurea composites from Examples 6-8 with addition amounts of 1 wt%, 1.5 wt%, and 2 wt%, respectively, and compared with the MI-type polyurea (MIPUA) from Example 3 without hydrotalcite. The test results are as follows: Figure 1 As shown in Table 1.

[0044] Figure 1 The stress-strain curves are for the polyurea composite materials of Examples 3 and 6-8.

[0045] Table 1. Tensile property test results of polyurea composites with different MgAl-LDHs addition amounts Figure 1 The stress-strain curves of polyurea composites with different amounts of hydrotalcite (MLD) are shown. Table 1 summarizes the thickness, elastic modulus, tensile strength, and elongation at break data for different amounts of MLD. It can be seen that the elastic modulus of MIPUA without MgAl-LDH nanoparticles is 166.34 MPa, the tensile strength is 7.26 MPa, and the elongation at break is 27.5%, exhibiting typical non-yielding brittle fracture characteristics. However, after adding MgAl-LDH to the polyurea matrix, compared to MIPUA, the elastic modulus and tensile strength of the composite material are significantly reduced, while the elongation at break is significantly increased. This indicates that the incorporation of nanofillers promotes the transformation of the material from brittle fracture to ductile deformation mechanism, and its plastic deformation capacity before fracture is significantly enhanced. As the amount of MgAl-LDH added increases from 1.0 wt% to 2.0 wt%, the elastic modulus and tensile strength of the composite material gradually increase, while the elongation at break shows a trend of first increasing and then decreasing, but the decrease is relatively small. A comprehensive comparison of various mechanical properties shows that when the amount of MgAl-LDHs added is 2.0 wt%, the composite material exhibits the most balanced overall tensile properties, with an elastic modulus of 92.74 MPa, a tensile strength of 3.96 MPa, and an elongation at break of 146.32%.

[0046] 2. To systematically investigate the effect of MgAl-LDHs on the flame retardancy of the polyurea material of this invention, limiting oxygen index (LOI) tests were conducted on MgAl-LDHs@MIPUA with different addition amounts. The results are as follows: Figure 2 As shown.

[0047] Figure 2 The limiting oxygen index test results are for the polyurea composite materials of Examples 3 and 6-8.

[0048] like Figure 2 As shown, the limiting oxygen index (LOI) of the MIPUA prepared in Example 3 of this invention is 23.68%, which also shows excellent flame retardant properties, which is significantly improved compared with traditional polyurea materials.

[0049] When the MgAl-LDHs addition amounts were 1.0%, 1.5%, and 2.0%, the LOI values ​​of MgAl-LDHs@MIPUA increased to 24.39%, 25.20%, and 26.55%, respectively. Overall, the LOI value of the composite material gradually increased with the increase of MgAl-LDHs addition, indicating that the introduction of MgAl-LDHs helps to improve the flame retardant properties of polyurea materials. This phenomenon is mainly due to the good flame retardant and thermal stability properties of MgAl-LDHs. First, during the thermal decomposition process, MgAl-LDHs removes interlayer water and structural hydroxyl groups. This process absorbs a certain amount of heat and can dilute the combustible decomposition products to a certain extent, thereby inhibiting the combustion process. Second, the inorganic residues formed after the decomposition of MgAl-LDHs help to further improve the integrity and stability of the char layer and slow down the transfer of heat, oxygen, and combustible volatiles inside and outside the material.

[0050] Combination Figure 2 The morphology of the samples after combustion tests shows that the char layer formed after combustion becomes more pronounced with increasing MgAl-LDHs addition, indicating that the addition of MgAl-LDHs promotes char layer formation. Combined with the LOI results and combustion residue morphology analysis, it can be concluded that MgAl-LDHs can improve the flame retardant properties of polyurea composites through endothermic decomposition, inorganic barrier, and char formation promotion.

[0051] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Various modifications and improvements made by those skilled in the art to the technical solutions of the present invention without departing from the spirit of the present invention should fall within the protection scope defined by the claims of the present invention.

Claims

1. A flame-retardant polyurea composite material, characterized in that, The raw material contains component A and component B; Component A is prepared by reacting aromatic isocyanate with polyether polyol, wherein the aromatic isocyanate contains diphenylmethane diisocyanate and isophorone diisocyanate. Component B contains polyetheramine and diamine chain extender.

2. The flame-retardant polyurea composite material according to claim 1, characterized in that, The raw materials of the flame-retardant polyurea composite material also contain magnesium aluminum hydrotalcite; the amount of magnesium aluminum hydrotalcite added to the flame-retardant polyurea composite material is 1.0-2.0 wt%.

3. The flame-retardant polyurea composite material according to claim 1, characterized in that, The mass ratio of component A to component B is 59-60.9:36.

7.

4. The flame-retardant polyurea composite material according to claim 1, characterized in that, The mass ratio of the aromatic isocyanate to the polyether polyol is 30.8-40:35-43.

5. The flame-retardant polyurea composite material according to claim 1, characterized in that, The polyetheramine is polyoxypropylene diamine.

6. The flame-retardant polyurea composite material according to claim 1, characterized in that, The mass ratio of the polyetheramine to the diamine chain extender is 30:

17.

7. The flame-retardant polyurea composite material according to claim 1, characterized in that, The diamine chain extender contains dimethylthiotoluenediamine and 4,4'-methylenebis(N-(sec-butyl)aniline); the mass ratio of dimethylthiotoluenediamine to 4,4'-methylenebis(N-(sec-butyl)aniline) is 10:

7.

8. A method for preparing a flame-retardant polyurea composite material according to any one of claims 1-7, characterized in that, Includes the following steps: Magnesium aluminum hydrotalcite was mixed with polyether polyol, and then aromatic isocyanate was added. The mixture was reacted under a protective atmosphere at 80°C to obtain component A. Component B is obtained by mixing polyetheramine and diamine chain extender; Components A and B are mixed and cured to prepare the flame-retardant polyurea composite material.

9. The application of the flame-retardant polyurea composite material according to any one of claims 1-7 in the field of flame retardancy.

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