High-heat-resistant flame-retardant enhanced injection molding composite material for automobile and preparation method thereof

Abstract

The invention discloses a high-heat-resistance flame-retardant enhanced injection molding composite material for an automobile and a preparation method thereof, and belongs to the field of polymer composite materials. The composite material is composed of polypropylene resin, modified glass fiber, a modified phosphorus-nitrogen flame retardant, modified nano talcum powder and the like, and the core innovation lies in directional modification of three key materials: the glass fiber is treated by a titanate coupling agent to improve the interface bonding force, and the phosphorus-nitrogen flame retardant is modified by silane to construct a core-shell structure to enhance the flame retardant efficiency; the nano talcum powder is coated with stearic acid, so that the dispersity is improved. Through component collaborative design and a specific preparation process, the thermal deformation temperature of the material reaches 146 DEG C or above, the tensile strength is greater than or equal to 42.5 MPa, the oxygen index is greater than or equal to 33.5%, the vertical combustion grade is V-0 grade, and the material has excellent mechanical properties, heat resistance, flame retardance and processing fluidity, is suitable for key parts such as automotive upholstery and engine peripheral parts, is simple and controllable in preparation process, and is suitable for industrial production. The industrial production is facilitated.

Description

Technical Field

[0001] This invention relates to the field of polymer composite materials technology, and in particular to a high heat-resistant and flame-retardant reinforced injection-molded composite material for automobiles and its preparation method, which is suitable for automotive applications such as interior parts, engine peripheral parts, and electrical control system housings that have stringent requirements for heat resistance, flame retardancy, and mechanical strength. Background Technology

[0002] The lightweight and safety-oriented development of the automotive industry has placed higher demands on automotive composite materials. Polypropylene, as a commonly used automotive matrix material, has advantages such as low density, excellent processing performance, and low cost. However, natural polypropylene has poor heat resistance (heat distortion temperature is only 80-100℃), is flammable, and has a limiting oxygen index of only 18-20%. Its mechanical strength is insufficient, making it difficult to meet the usage requirements of key parts such as engine periphery and electrical components.

[0003] In existing technologies, the performance of polypropylene is improved by adding glass fiber reinforcement and halogenated or inorganic flame retardants. However, this approach has several drawbacks: the polar surface of ordinary glass fiber has poor compatibility with the non-polar matrix of polypropylene, leading to easy agglomeration and weak interfacial bonding, thus failing to fully exert its reinforcing effect; traditional halogenated flame retardants release toxic and harmful gases during combustion, polluting the environment and failing to meet automotive environmental standards; inorganic flame retardants require large doses to achieve the flame-retardant effect, resulting in a significant decrease in the material's mechanical properties and processing fluidity; while nanofillers can improve heat resistance, they are prone to agglomeration and have poor dispersion with the matrix, making it difficult to achieve a balanced performance improvement.

[0004] Furthermore, automotive parts are mostly manufactured using injection molding, requiring composite materials to possess excellent melt flowability. Existing multifunctional modified polypropylene often suffers from problems such as unstable processing and low yield due to poor synergistic effects of additives. Therefore, there is an urgent need to develop an injection-molded composite material for automobiles that combines high heat resistance, high flame retardancy, high strength, and excellent processing performance through material modification optimization and component formulation design. Summary of the Invention

[0005] Purpose of the invention: The purpose of this invention is to provide a high heat-resistant and flame-retardant reinforced injection-molded composite material for automobiles. By directional modification of three key materials—glass fiber, flame retardant, and nano-talc—and combined with component synergistic design, a balanced improvement in the material's heat resistance, flame retardancy, mechanical strength, and processing performance is achieved. Another purpose of this invention is to provide a preparation method for this composite material, which is simple, controllable, and suitable for industrial production.

[0006] Technical solution: A high heat-resistant and flame-retardant reinforced injection-molded composite material for automobiles, comprising the following components by weight: 80 parts polypropylene resin, 20 parts modified glass fiber, 15 parts modified phosphorus-nitrogen flame retardant, 5 parts modified nano talc, 4 parts maleic anhydride-grafted polypropylene, 0.8 parts 2,6-di-tert-butyl-p-cresol, and 0.5 parts calcium stearate; The polypropylene resin is homopolymer polypropylene with a melt index of 12 g / 10 min and a melt index of 230 °C / 2.16 kg. The modified glass fiber is a short-cut glass fiber with a diameter of 10 μm and a length of 4 mm, which has been surface modified with a titanate coupling agent. The modified phosphorus-nitrogen flame retardant is a silane-modified ammonium polyphosphate-melamine cyanurate composite flame retardant, with a mass ratio of ammonium polyphosphate to melamine cyanurate of 2:1. The modified nano-talc powder is a nano-talc powder modified by coating the surface with stearic acid, with an average particle size of 500 nm. The grafting rate of the maleic anhydride-grafted polypropylene was 4%; The 2,6-di-tert-butyl-p-cresol has an industrial-grade purity of 99.5%; the calcium stearate is a lubricant with an industrial-grade purity of 99%.

[0007] Preferably, the modified glass fiber is prepared as follows: a 2% (w / w) solution of titanate coupling agent in ethanol is prepared, wherein the volume ratio of ethanol to deionized water is 95:5. After stirring evenly, the pH value is adjusted to 4.5. Short-cut glass fibers are added to the above solution at a bath ratio of 1:20, and the solution is stirred at 60°C for 30 minutes to allow the titanate coupling agent to be fully adsorbed onto the glass fiber surface. The treated glass fiber is then dried in a 120°C oven for 2 hours to remove the solvent and moisture. The alkoxy groups of the titanate coupling agent molecules undergo a de-alcoholization condensation reaction with the silanol groups on the glass fiber surface to form stable Ti-O-Si covalent bonds, thereby constructing a dense organic coating layer on the glass fiber surface to obtain the modified glass fiber.

[0008] Preferably, the modified phosphorus-nitrogen flame retardant is prepared as follows: 14.55g of deionized water and 0.45g of glacial acetic acid are mixed and stirred until the pH of the solution is adjusted to 4.5. 15g of γ-aminopropyltriethoxysilane is slowly added dropwise and stirred at 300r / min for 30 minutes to prepare a 3% (w / w) γ-aminopropyltriethoxysilane hydrolysate for later use. 100g of ammonium polyphosphate powder is added to a high-speed mixer, the speed is adjusted to 800r / min, and the temperature is raised to 60℃. The hydrolysate is then atomized and sprayed dropwise onto the surface of the ammonium polyphosphate powder. After the spraying is completed, the temperature is raised to 80℃ and the mixture is stirred at a constant temperature for 1 hour. The P-OH on the surface of the ammonium polyphosphate reacts with the -Si-OH in the hydrolysate. A water condensation reaction forms Si-OP covalent bonds to obtain the APP@KH550 core-shell precursor. 50g of melamine cyanurate powder is added to a high-speed mixer in three portions, with 10-minute intervals between each addition. The mixture is stirred for 30 minutes at 800 rpm and 80°C. Melamine cyanurate forms hydrogen bonds with KH550, coating the surface of individual APP@KH550 particles to form the APP@KH550@MCA double-layer core-shell structure powder. The powder is then heated to 160°C at 800 rpm for 30 minutes to remove moisture. The dried core-shell powder is then pulverized using an air jet mill and passed through a 200-mesh standard sieve to obtain a modified phosphorus-nitrogen flame retardant.

[0009] Preferably, the modified nano-talc powder is prepared as follows: nano-talc powder is added to deionized water to prepare a suspension with a mass fraction of 5%, and ultrasonically dispersed for 30 minutes with an ultrasonic power of 500W; stearic acid is heated to 70°C to melt, and added to the above suspension at a mass ratio of stearic acid to nano-talc powder of 1:20. The mixture is stirred and reacted at 80°C for 60 minutes, and the stearic acid molecules undergo esterification reaction with the hydroxyl groups on the surface of the nano-talc powder through the carboxyl groups; the suspension after reaction is centrifuged, the precipitate is washed three times with deionized water, dried at 105°C for 3 hours, pulverized, and passed through a 300-mesh sieve to obtain modified nano-talc powder.

[0010] A method for preparing a high heat-resistant and flame-retardant reinforced injection-molded composite material for automobiles includes the following steps: S1. Place the polypropylene resin in an 85℃ oven and dry for 4 hours to remove moisture, then set aside. S2. Weigh the modified glass fiber, modified phosphorus-nitrogen flame retardant, modified nano talc, maleic anhydride-grafted polypropylene, 2,6-di-tert-butyl-p-cresol, and calcium stearate according to the weight parts, add them to a high-speed mixer, set the speed to 800 r / min, mix for 25 minutes to obtain a uniform mixture. S3. Add the dried polypropylene resin and mixture to a twin-screw extruder. Set the temperatures of each section of the extruder as follows: Zone 1 160℃, Zone 2 175℃, Zone 3 185℃, Zone 4 190℃, and Die Head 180℃. The screw speed is 300 r / min. After melt blending, extrude and granulate. After water cooling, pelletizing, and drying, obtain high heat-resistant and flame-retardant reinforced injection molded composite material granules for automotive applications. Beneficial effects: Modified glass fibers are coated with a titanate coupling agent. The titanate coupling agent forms stable Ti-O-Si covalent bonds with the glass fiber surface, changing the glass fiber surface from hydrophilic to hydrophobic. The interfacial bonding force with the polypropylene matrix is ​​increased by more than 40%. This not only solves the fiber agglomeration problem, but also significantly enhances the mechanical strength of the composite material. The tensile strength is increased by 35% compared with the unmodified glass fiber composite material.

[0011] The modified phosphorus-nitrogen flame retardant employs a single-particle stepwise coating process to prepare an APP@KH550@MCA double-layer core-shell structure, fundamentally avoiding flame retardant powder agglomeration. With APP as the phosphorus source core and MCA as the nitrogen source shell, precise phosphorus-nitrogen synergy is achieved within a single particle, and gas-phase / condensed-phase flame retardancy occurs simultaneously during combustion. The KH550 intermediate layer is bonded to APP through Si-OP covalent bonds and to MCA through hydrogen bonds, achieving both stable core-shell structure and forming a dense phosphorus-silicon composite carbon layer during combustion, preventing molten dripping and significantly improving flame retardant efficiency. This results in a composite material with an oxygen index of over 33.5% and a vertical burning rating of V-0, with no toxic gas release during combustion, meeting environmental protection requirements.

[0012] Modified nano-talc powder, after being coated with stearic acid, exhibits significantly improved dispersibility and forms a uniform heat-resistant network within the polypropylene matrix. This increases the heat distortion temperature of the composite material to over 145℃. Furthermore, through synergistic effects with glass fiber, the rigidity and dimensional stability of the material are further optimized.

[0013] The synergistic effect of each component, with maleic anhydride-grafted polypropylene acting as a compatibilizer, further strengthens the interfacial bonding between the modified filler and the matrix, while calcium stearate improves processing fluidity. This allows the composite material to maintain high heat resistance, high flame retardancy, and high strength while possessing excellent injection molding performance, with a yield rate of over 98%. Attached Figure Description

[0014] Figure 1 This is a graph showing the performance test results of the embodiment and the comparative example; Figure 2 It is a picture of the actual particle size produced. Detailed Implementation

[0015] To make the technical solution of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0016] Example 1 (1) Preparation of modified glass fiber: Prepare a 2% (w / w) solution of titanate coupling agent in ethanol (ethanol:deionized water = 95:5, volume ratio), adjust the pH to 4.5, add 100g of short glass fiber (diameter 10μm, length 4mm) to the solution (bath ratio 1:20), stir at 60℃ for 30 minutes, and dry at 120℃ for 2 hours to obtain modified glass fiber; (2) Preparation of modified phosphorus-nitrogen flame retardant: Weigh 100g ammonium polyphosphate (degree of polymerization 1000, phosphorus content ≥31%), 50g melamine cyanurate (nitrogen content ≥49%), 15g γ-aminopropyltriethoxysilane, 0.45g glacial acetic acid, and 14.55g deionized water for later use; Preparation of hydrolysate: Add 0.45g glacial acetic acid to 14.55g deionized water, stir evenly to adjust pH=4.5, and slowly add 15g glacial acetic acid. gγ-aminopropyltriethoxysilane was stirred at 300 r / min for 30 minutes to obtain a 3% KH550 hydrolysate; APP@KH550 preparation: 100 g ammonium polyphosphate powder was added to a high-speed mixer, and the KH550 hydrolysate was atomized and sprayed dropwise onto the powder surface at 800 r / min and 60 °C. After the drop spraying was completed, the temperature was raised to 80 °C and the reaction was stirred at a constant temperature for 1 hour to obtain the APP@KH550 core-shell precursor; Preparation of APP@KH550@MCA: 50g of MCA powder was added to a high-speed mixer in three batches, with a 10-minute interval between each batch. The mixture was stirred at 800r / min and 80℃ for 30 minutes to form a double-layer core-shell structure powder. Curing and pulverization: The powder was dehydrated by constant temperature drying at 800r / min and 160℃ for 30 minutes. After removal, it was pulverized by an air jet mill and passed through a 200-mesh sieve to obtain APP@KH550@MCA double-layer core-shell structure modified phosphorus-nitrogen flame retardant. (3) Preparation of modified nano talc: 50g of nano talc (particle size 500nm) was added to 1000mL of deionized water, ultrasonically dispersed for 30 minutes (500W), 2.5g of stearic acid was melted at 70℃ and added to the suspension, stirred at 80℃ for 60 minutes, centrifuged and washed 3 times, dried at 105℃ for 3 hours, and passed through a 300-mesh sieve to obtain modified nano talc; (4) Dry 80g of polypropylene resin at 85℃ for 4 hours for later use; (5) Weigh 20g of modified glass fiber, 15g of modified phosphorus and nitrogen flame retardant, 5g of modified nano talc powder, 4g of maleic anhydride grafted polypropylene, 0.8g of 2,6-di-tert-butyl-p-cresol, and 0.5g of calcium stearate, add them to a high-speed mixer, mix at 800r / min for 25 minutes to obtain a mixture; (6) The dried polypropylene resin and the mixture are added to a twin-screw extruder. The temperatures of each section are: 160℃ in zone 1, 175℃ in zone 2, 185℃ in zone 3, 190℃ in zone 4, and 180℃ at the die head. The screw speed is 300r / min. The mixture is extruded and granulated to obtain composite material particles.

[0017] Example 2 (1) The preparation methods of modified glass fiber, modified phosphorus-nitrogen flame retardant and modified nano talc are the same as in Example 1; (2) Dry 80g of polypropylene resin at 85℃ for 4 hours for later use; (3) Weigh 20g of modified glass fiber, 15g of modified phosphorus and nitrogen flame retardant, 5g of modified nano talc powder, 4g of maleic anhydride grafted polypropylene, 0.8g of 2,6-di-tert-butyl-p-cresol, and 0.5g of calcium stearate, add them to a high-speed mixer, mix at 800r / min for 25 minutes to obtain a mixture; (4) The extrusion granulation process is the same as in Example 1 to obtain composite material particles.

[0018] Example 3 (1) The preparation methods of modified glass fiber, modified phosphorus-nitrogen flame retardant and modified nano talc are the same as in Example 1; (2) Dry 80g of polypropylene resin at 85℃ for 4 hours for later use; (3) Weigh 20g of modified glass fiber, 15g of modified phosphorus and nitrogen flame retardant, 5g of modified nano talc powder, 4g of maleic anhydride grafted polypropylene, 0.8g of 2,6-di-tert-butyl-p-cresol, and 0.5g of calcium stearate, add them to a high-speed mixer, mix at 800r / min for 25 minutes to obtain a mixture; (4) The extrusion granulation process is the same as in Example 1 to obtain composite material particles.

[0019] Comparative Example 1 (1) Unmodified glass fiber: Short glass fiber (10 μm in diameter and 4 mm in length) is used directly without titanate coupling agent treatment; (2) The preparation methods of the modified phosphorus-nitrogen flame retardant and the modified nano-talc are the same as in Example 1; (3) Dry 80g of polypropylene resin at 85℃ for 4 hours for later use; (4) Weigh 20g of unmodified glass fiber, 15g of modified phosphorus and nitrogen flame retardant, 5g of modified nano talc powder, 4g of maleic anhydride grafted polypropylene, 0.8g of 2,6-di-tert-butyl-p-cresol, and 0.5g of calcium stearate, add them to a high-speed mixer, mix at 800r / min for 25 minutes to obtain a mixture; (5) The extrusion granulation process is the same as in Example 1 to obtain composite material particles.

[0020] Comparative Example 2 (1) The preparation methods of modified glass fiber and modified nano talc are the same as in Example 1; (2) Unmodified flame retardant: A mixture of ammonium polyphosphate and melamine cyanurate at a mass ratio of 2:1 is used directly without silane modification; (3) Dry 80g of polypropylene resin at 85℃ for 4 hours for later use; (4) Weigh 20g of modified glass fiber, 15g of unmodified flame retardant, 5g of modified nano talc powder, 4g of maleic anhydride grafted polypropylene, 0.8g of 2,6-di-tert-butyl-p-cresol, and 0.5g of calcium stearate, add them to a high-speed mixer, mix at 800r / min for 25 minutes to obtain a mixture; (5) The extrusion granulation process is the same as in Example 1 to obtain composite material particles.

[0021] Comparative Example 3 (1) The preparation methods of modified glass fiber and modified phosphorus-nitrogen flame retardant are the same as in Example 1; (2) Unmodified nano talc: Nano talc (particle size 500nm) is used directly without stearic acid modification; (3) Dry 80g of polypropylene resin at 85℃ for 4 hours for later use; (4) Weigh 20g of modified glass fiber, 15g of modified phosphorus and nitrogen flame retardant, 5g of unmodified nano talc powder, 4g of maleic anhydride grafted polypropylene, 0.8g of 2,6-di-tert-butyl-p-cresol, and 0.5g of calcium stearate, add them to a high-speed mixer, mix at 800r / min for 25 minutes to obtain a mixture. (5) The extrusion granulation process is the same as in Example 1 to obtain composite material particles.

[0022] Performance testing methods Heat distortion temperature (HDT): According to GB / T1634.2-2004 standard, load 0.45MPa; Tensile strength: According to GB / T1040.2-2006 standard, tensile rate is 50 mm / min; Bending strength: According to GB / T9341-2008 standard, bending rate is 2 mm / min; Impact strength of simply supported beam: According to GB / T1043.1-2008 standard, no notch; Oxygen Index (OI): Based on GB / T2406.2-2009 standard; Vertical flammability rating: UL94 according to GB / T2408-2021 standard; Melt flow index (MI): According to GB / T3682.1-2018 standard, 230℃ / 2.16kg.

[0023] The test results of Examples 1-3 show that the composite material provided by the present invention exhibits excellent performance in terms of heat distortion temperature, mechanical strength, flame retardancy and processing performance: the heat distortion temperature is above 146℃, the tensile strength is ≥42.5MPa, the flexural strength is ≥65.3MPa, the oxygen index is ≥33.5%, the vertical burning rating reaches V-0, and the melt flow index is ≥10.2g / 10min, which meets the requirements for use in key automotive components.

[0024] Comparative Example 1 uses unmodified glass fiber. Due to poor interfacial bonding, the tensile strength, flexural strength, and impact strength decreased by 26.6%, 25.7%, and 25.8%, respectively, and the heat distortion temperature decreased by 16.4%. This indicates that modified glass fiber is crucial for improving the mechanical properties and heat resistance of the material. Comparative Example 2 used an unmodified flame retardant, and the oxygen index dropped significantly to 27.3%, with a vertical burning rating of only HB. Molten dripping occurred during combustion, indicating that silane modification significantly improved the flame retardant efficiency and synergistic charring ability of phosphorus-nitrogen flame retardants. Comparative Example 3 used unmodified nano-talc powder, which resulted in a decrease in mechanical properties and heat resistance due to agglomeration. The tensile strength decreased by 16.2%, the heat distortion temperature decreased by 11.0%, and the melt index decreased by 12.4%, demonstrating the effect of stearic acid modification on improving the dispersibility and processing performance of nano-talc powder.

[0025] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the scope of protection of the present invention. Therefore, the scope of protection of this patent should be determined by the appended claims.

Claims

1. A high heat-resistant and flame-retardant reinforced injection-molded composite material for automobiles, characterized in that, The product comprises the following components by weight: 80 parts polypropylene resin, 20 parts modified glass fiber, 15 parts APP@KH550@MCA double-core-shell modified phosphorus-nitrogen flame retardant, 5 parts modified nano talc, 4 parts maleic anhydride-grafted polypropylene, 0.8 parts 2,6-di-tert-butyl-p-cresol, and 0.5 parts calcium stearate. The polypropylene resin is homopolymer polypropylene with a melt index of 12 g / 10 min and a melt index of 230 °C / 2.16 kg. The modified glass fiber is a short-cut glass fiber with a diameter of 10 μm and a length of 4 mm, which has been surface modified with a titanate coupling agent. The modified phosphorus-nitrogen flame retardant is a silane-modified ammonium polyphosphate-melamine cyanurate composite flame retardant, with a mass ratio of ammonium polyphosphate to melamine cyanurate of 2:

1. The modified nano-talc powder is a nano-talc powder modified by coating the surface with stearic acid, with an average particle size of 500 nm. The grafting rate of the maleic anhydride-grafted polypropylene was 4%; The 2,6-di-tert-butyl-p-cresol has an industrial-grade purity of 99.5%; the calcium stearate is a lubricant with an industrial-grade purity of 99%.

2. The high heat-resistant and flame-retardant reinforced injection-molded composite material for automobiles according to claim 1, characterized in that, The modified glass fiber is prepared as follows: a 2% (w / w) solution of titanate coupling agent in ethanol is prepared, wherein the volume ratio of ethanol to deionized water is 95:

5. After stirring evenly, the pH value is adjusted to 4.

5. Short-cut glass fibers are added to the above solution at a bath ratio of 1:

20. The solution is stirred at 60°C for 30 minutes to allow the titanate coupling agent to be fully adsorbed onto the glass fiber surface. The treated glass fiber is then dried in a 120°C oven for 2 hours to remove the solvent and moisture. The alkoxy groups of the titanate coupling agent molecules undergo a de-alcoholization condensation reaction with the silanol groups on the glass fiber surface to form stable Ti-O-Si covalent bonds, thus constructing a dense organic coating layer on the glass fiber surface to obtain the modified glass fiber.

3. The high heat-resistant and flame-retardant reinforced injection-molded composite material for automobiles according to claim 1, characterized in that, The modified phosphorus-nitrogen flame retardant is prepared as follows: 14.55g of deionized water and 0.45g of glacial acetic acid are mixed and stirred until the pH of the solution is adjusted to 4.

5. 15g of γ-aminopropyltriethoxysilane is slowly added dropwise and stirred at 300r / min for 30 minutes to prepare a 3% (w / w) γ-aminopropyltriethoxysilane hydrolysate for later use. 100g of ammonium polyphosphate powder is added to a high-speed mixer, the speed is adjusted to 800r / min, and the temperature is raised to 60℃. The hydrolysate is then atomized and sprayed dropwise onto the surface of the ammonium polyphosphate powder. After the spraying is completed, the temperature is raised to 80℃ and the mixture is stirred at a constant temperature for 1 hour. The P-OH on the surface of the ammonium polyphosphate undergoes dehydration and condensation with the -Si-OH in the hydrolysate. The reaction forms Si-OP covalent bonds to obtain the APP@KH550 core-shell precursor. 50g of melamine cyanurate powder is added to a high-speed mixer in three portions, with a 10-minute interval between each addition. The mixture is stirred for 30 minutes at 800 rpm and 80°C. Melamine cyanurate forms hydrogen bonds with KH550, coating the surface of APP@KH550 single particles to form the APP@KH550@MCA double-layer core-shell structure powder. The mixture is then heated to 160°C at 800 rpm for 30 minutes to remove moisture. The dried core-shell powder is then pulverized using an air jet mill and passed through a 200-mesh standard sieve to obtain the modified phosphorus-nitrogen flame retardant.

4. The high heat-resistant and flame-retardant reinforced injection-molded composite material for automobiles according to claim 1, characterized in that, The modified nano-talc powder is prepared as follows: nano-talc powder is added to deionized water to prepare a suspension with a mass fraction of 5%, and ultrasonically dispersed for 30 minutes with an ultrasonic power of 500W; stearic acid is heated to 70℃ to melt, and added to the above suspension at a mass ratio of stearic acid to nano-talc powder of 1:

20. The mixture is stirred and reacted at 80℃ for 60 minutes, and the stearic acid molecules undergo esterification reaction with the hydroxyl groups on the surface of the nano-talc powder through the carboxyl groups; the suspension after reaction is centrifuged, the precipitate is washed three times with deionized water, dried at 105℃ for 3 hours, pulverized, and passed through a 300-mesh sieve to obtain modified nano-talc powder.

5. A method for preparing a high heat-resistant and flame-retardant reinforced injection-molded composite material for automobiles as described in any one of claims 1 to 4, characterized in that, Includes the following steps: S1. Place the polypropylene resin in an 85℃ oven and dry for 4 hours to remove moisture. Set aside for later use. S2. Weigh the modified glass fiber, modified phosphorus-nitrogen flame retardant, modified nano talc, maleic anhydride-grafted polypropylene, 2,6-di-tert-butyl-p-cresol, and calcium stearate according to the weight parts, add them to a high-speed mixer, set the speed to 800 r / min, mix for 25 minutes to obtain a uniform mixture. S3. Add the dried polypropylene resin and the mixture into a twin-screw extruder. Set the temperature of each section of the extruder as follows: Zone 1 160℃, Zone 2 175℃, Zone 3 185℃, Zone 4 190℃, and Die Head 180℃. The screw speed is 300 r / min. After melt blending, the mixture is extruded and granulated. After water cooling, pelletizing, and drying, high heat-resistant and flame-retardant reinforced injection molding composite material granules for automobiles are obtained.

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