Flame-retardant weatherable foamed polypropylene composite material and preparation method thereof

Abstract

The application provides a kind of flame-retardant weatherable foamed polypropylene composite material and its preparation method.The foamed polypropylene composite material contains the following components by weight: polypropylene 50-90 parts, polyethylene 10-50 parts, flame retardant 5-20 parts, synergist 1-10 parts, foaming agent 2-15 parts, irradiation sensitizer 0.5-3 parts, antioxidant 0.5-2 parts.The polypropylene composite material prepared by the application has a higher flame retardant grade and oxygen index, can effectively prevent the spread of fire, significantly reduces the risk of fire, and the halogen-free system is more environmentally friendly;The tensile strength is high and the tensile strength retention rate after thermal aging and ultraviolet aging is high, indicating that the mechanical properties are good, the structural bearing capacity is strong, and the weather resistance is good, so that the material has excellent long-term service life and environmental stability, and has wide application prospect.

Description

Technical Field

[0001] This invention belongs to the field of polypropylene foaming material technology, and particularly relates to a flame-retardant and weather-resistant foamed polypropylene composite material and its preparation method. Background Technology

[0002] Polypropylene (PP) foam materials are widely used in the automotive industry, building insulation, packaging and transportation, and outdoor facilities due to their advantages such as light weight, excellent thermal insulation, cushioning performance, and recyclability. However, polypropylene itself is a flammable polymer material with a limiting oxygen index (LOI) of only 17%-18%, which severely limits its application in environments with high safety requirements and harsh conditions.

[0003] To improve the flame retardant properties of polypropylene, flame retardants are often added industrially. While traditional halogenated flame retardants are highly efficient, they release toxic gases and fumes during combustion, which is inconsistent with current environmental regulations and the trend towards green materials, and their use has been gradually restricted. Halogen-free intumescent flame retardants have become a research hotspot due to their environmental friendliness and high flame retardant efficiency. However, conventional halogen-free intumescent flame retardants have poor compatibility with polypropylene, and large additions can easily lead to a significant decrease in the material's mechanical properties. Furthermore, there is still room for improvement in their char formation efficiency and char layer stability. Simultaneously, polypropylene molecules contain a large number of tertiary carbon atoms, making them extremely sensitive to light, heat, and oxygen. During long-term outdoor use, they are prone to molecular chain breakage, yellowing, and embrittlement, resulting in a rapid decline in mechanical properties. To improve weather resistance, existing technologies often employ the addition of light stabilizers, ultraviolet absorbers, and other additives. However, the synergy between these additives and the flame retardant system remains poor, failing to achieve complementary performance and improve the overall material performance.

[0004] Therefore, how to prepare a polypropylene foam material that can simultaneously achieve high flame retardancy, long-lasting weather resistance, stable mechanical properties, and controllable process is the problem that this invention urgently needs to solve. Summary of the Invention

[0005] The purpose of this invention is to provide a flame-retardant and weather-resistant foamed polypropylene composite material and its preparation method, so as to solve the problems mentioned in the background art.

[0006] To achieve the above objectives, the present invention provides a flame-retardant and weather-resistant foamed polypropylene composite material, characterized in that it comprises the following components in parts by weight: 50-90 parts of polypropylene, 10-50 parts of polyethylene, 5-20 parts of flame retardant, 1-10 parts of synergist, 2-15 parts of foaming agent, 0.5-3 parts of radiation sensitizer, and 0.5-2 parts of antioxidant. The flame retardant is an intumescent flame retardant, which is prepared by combining triazine-based charring agent, ammonium polyphosphate, and melamine polyphosphate.

[0007] As a further improvement, the synthesis of the triazine-based charring agent includes the following steps: (1) Add cyanuric chloride and organic solvent to a flask, stir and dissolve under ice bath, then slowly add ethanolamine to the flask. After the addition is complete, add a small amount of inorganic base solution to the reaction system and continue stirring in an ice bath for 1-3 hours. When the reaction is complete, intermediate one is obtained. (2) Heat the intermediate obtained in step (1) to 50-60℃, and then slowly add a mixed solution of 4,4'-diaminodiphenyl sulfone and organic solvent to the reaction system. After the addition is completed, add a small amount of inorganic base solution to the reaction system and keep the reaction at the temperature for 2-5 hours. After the reaction is completed, intermediate two is obtained. (3) Heat the intermediate obtained in step (2) to 80-100℃, and then slowly add the solution obtained by piperazine and organic solvent. After the addition is complete, add a small amount of inorganic base solution to the reaction system and continue the reaction at this temperature for 5-10 hours. After the reaction is complete, perform post-treatment to obtain triazine char-forming agent.

[0008] As a further improvement, the molar ratio of the added cyanuric chloride, ethanolamine and 4,4'-diaminodiphenyl sulfone is 2:(2-2.5):1.

[0009] As a further improvement, the synthesis of the flame retardant includes the following steps: In a high-speed mixer, triazine charring agent, ammonium polyphosphate, and melamine polyphosphate are mixed at 80-100℃ in a ratio of ammonium polyphosphate:melamine polyphosphate:triazine charring agent of (2-3):1:1 to obtain an intumescent flame retardant.

[0010] As a further improvement, the synergist comprises nanolayered metal carbides and hindered amine light stabilizers.

[0011] As a further improvement, the synthesis of the nanolayered metal carbide includes the following steps: (1) Dissolve lithium fluoride in dilute hydrochloric acid solution, then slowly add titanium aluminum carbide, stir at 35-45℃ for 20-30h, after stirring, centrifuge the obtained substance and wash with deionized water until the pH value of the supernatant is neutral, redisperse the obtained precipitate in deionized water, sonicate under ice bath for 20-30min, and finally centrifuge and dry to obtain nano-suspension; (2) Place the nano-suspension obtained in step (1) in a flask, add an organic solvent, and stir at room temperature for 10-15 min. Then add a silane coupling agent and stir at room temperature for 10-15 h. After the reaction is completed, perform post-treatment to obtain nano-layered metal carbides.

[0012] As a further improvement, the hindered amine light stabilizer is preferably bis(2,2,6,6-tetramethyl-4-piperidinyl) sebacate.

[0013] As a further improvement, the weight ratio of the nanolayered metal carbide to the hindered amine light stabilizer is 1:(1-1.5).

[0014] As a further improvement, the foaming agent is at least one of azodicarbonamide, p-toluenesulfonamide, N,N'-dinitrospentamethylenetetramine, trinitrosomethylenetriamine, triphosphatidyltriazine, azobisisobutyronitrile, and barium azodicarbonate; the irradiation sensitizer is at least one of trimethylolpropane triacrylate, dipentaerythritol hexaacrylate, triallyl isocyanurate, ethoxylated trimethylolpropane triacrylate, N,N'-m-phenylenebismaleimide, triallyl isocyanurate, and trimethylolpropane trimethacrylate.

[0015] As a further improvement, the antioxidant is at least one of antioxidant 1010, antioxidant 168, antioxidant 1098, and antioxidant 626.

[0016] This invention also provides a method for preparing a flame-retardant and weather-resistant foamed polypropylene composite material, characterized by comprising the following steps: (1) According to the weight parts, polypropylene, polyethylene, flame retardant, synergist, foaming agent, radiation sensitizer and antioxidant are put into a twin-screw extruder, melted and mixed evenly at a certain temperature, and extruded into sheets to obtain polypropylene pre-crosslinked master sheets; the processing temperature of the extruder should be lower than the decomposition temperature of the foaming agent; (2) The obtained pre-crosslinked master sheet is subjected to electron beam irradiation under specified dosage conditions to produce a crosslinking reaction and obtain a pre-foamed polypropylene master sheet; (3) The pre-foamed polypropylene master sheet is placed in a heating environment. Under conditions higher than the decomposition temperature of the foaming agent, the foaming agent decomposes and causes the master sheet to foam, thus obtaining a flame-retardant and weather-resistant foamed polypropylene composite material.

[0017] As a further improvement, the processing temperatures of each section of the twin-screw extruder are set as follows: feeding section 160-170℃, melting section 175-200℃, homogenization section 180-200℃, and screw speed 80-150rpm. As a further improvement, the irradiation dose in step (2) is 10-100kGy and the irradiation voltage is 0.5-3.0MeV; the decomposition temperature of the foaming agent in step (3) is 200-260℃.

[0018] Compared with the prior art, the beneficial effects of the present invention are: This invention provides a flame-retardant and weather-resistant foamed polypropylene composite material and its preparation method. The obtained polypropylene composite material has a high flame retardancy rating (UL 94: HF-1) and oxygen index, which can effectively prevent the spread of flames and significantly reduce the risk of fire. Moreover, the halogen-free system is more environmentally friendly. It has high tensile strength and a high tensile strength retention rate after thermo-oxidative aging and UV aging, indicating good mechanical properties, strong structural load-bearing capacity, and good weather resistance, giving the material excellent long-term service life and environmental stability. This invention employs an intumescent flame retardant composed of a triazine-based charring agent, ammonium polyphosphate, and melamine polyphosphate. This intumescent flame retardant rapidly forms a dense and continuous intumescent char layer, effectively blocking heat transfer and oxygen contact, thus improving flame retardant efficiency. The nano-layered metal carbide, after modification with a silane coupling agent, exhibits excellent compatibility with the polypropylene matrix. Its layered structure forms a physical barrier, blocking heat and ultraviolet light penetration. The hindered amine light stabilizer captures free radicals generated by ultraviolet light decomposition, delaying molecular chain aging. The synergistic system of nano-layered metal carbide and hindered amine light stabilizer, combined with electron irradiation crosslinking technology, further enhances the mechanical properties and weather resistance of polypropylene composites, solving the problems of poor weather resistance and easy aging and cracking of traditional foamed polypropylene composites. Detailed Implementation

[0019] The present invention will be described below with reference to specific embodiments. It should be noted that the following embodiments are examples of the present invention and are used only to illustrate the invention, not to limit it. Other combinations and various modifications within the scope of the present invention can be made without departing from its spirit or scope.

[0020] In the following examples, except for the triazine-based char-forming agent and the nano-layered metal carbide, all other compound monomers and related reagents used were commercially available. Specifically, polypropylene was purchased from Formosa Plastics Industrial (Ningbo) Co., Ltd., grade 5012XT; polyethylene was purchased from Sinopec Zhenhai Refining & Chemical Co., Ltd., grade 7042; ammonium polyphosphate was purchased from Jinan Chaoyixing Chemical Co., Ltd., grade HT-208; and melamine polyphosphate was purchased from Shanghai Maclean Biochemical Technology Co., Ltd., product number M859615.

[0021] The preparation of triazine-based charring agents includes the following steps: (1) Add 50 mmol of cyanuric chloride and 200 mL of acetonitrile to a flask, stir and dissolve in an ice bath, then slowly add 50 mmol of ethanolamine to the flask. After the addition is complete, add 5 mL of 10% sodium hydroxide solution to the reaction system and continue stirring in an ice bath for 2 h. When the reaction is complete, intermediate one is obtained. (2) Heat the intermediate obtained in step (1) to 50°C, and then slowly add 25 mmol of 4,4'-diaminodiphenyl sulfone dissolved in 50 mL of acetonitrile to the reaction system. After the addition is complete, add 5 mL of 10% sodium hydroxide solution to the reaction system and keep the reaction at the temperature for 3 h. After the reaction is complete, intermediate two is obtained. (3) The intermediate obtained in step (2) was heated to 100°C, and then 25 mmol piperazine was slowly added dropwise to a solution obtained by dissolving 50 mL acetonitrile. After the addition was completed, 5 mL of 10% sodium hydroxide solution was added to the reaction system, and the reaction was continued at this temperature for 8 h. After the reaction was completed, the mixture was filtered and washed with deionized water. The solid obtained was dried in a vacuum drying oven at 80°C for 24 h to obtain a triazine char-forming agent.

[0022] The preparation of nanolayered metal carbides includes the following steps: (1) Dissolve 2.4 g of lithium fluoride in 20 mL of 9 mol / L hydrochloric acid solution, and then slowly add 1.5 g of titanium aluminum carbide to the above solution within 30 min. Stir at 35 °C for 24 h. After stirring, centrifuge the crude product at 10000 rpm for 10 min and wash with deionized water. Repeat centrifugation until the pH of the supernatant reaches 7. Disperse the obtained precipitate in 100 mL of deionized water, sonicate under ice bath for 30 min, and finally centrifuge at 10000 rpm for 20 min. Dry at 60 °C to obtain nano-suspension. (2) Take 5g of the nano suspension obtained in step (1) into a flask, add 50mL of acetone, and stir at room temperature for 10min. Then add 2.5mL of 3-(methacryloyloxy)propyltrimethoxysilane, stir at room temperature for 12h, and after the reaction is completed, centrifuge at 8000rpm for 10min and wash with acetone. Then dry the precipitate under vacuum at 60℃ for 12h to obtain nano-layered metal carbides.

[0023] Example 1 (1) By weight, 80 parts of polypropylene, 20 parts of polyethylene, 16 parts of flame retardant (8 parts of triazine charring agent, 4 parts of ammonium polyphosphate, 4 parts of melamine polyphosphate), 2.5 parts of synergist (1 part of nano-layered metal carbide, 1.5 parts of hindered amine light stabilizer), 6 parts of azodicarbonamide, 1.2 parts of trimethylolpropane triacrylate, and 1 part of antioxidant 1010 are added to a twin-screw extruder, melted and mixed evenly at a certain temperature, and extruded into sheets to obtain polypropylene pre-crosslinked master sheets; the processing temperature of each section of the twin-screw extruder is set as follows: feeding section 160℃, melting section 200℃, homogenization section 180℃, and screw speed 100rpm; (2) The obtained pre-crosslinked master sheet is subjected to electron beam irradiation under specified dose conditions to produce a crosslinking reaction and obtain a pre-foamed polypropylene master sheet; the irradiation dose is 50 kGy and the irradiation voltage is 1.5 MeV; (3) The pre-foamed polypropylene master sheet is placed in a high-temperature horizontal foaming furnace and foamed at 240°C. After foaming, it is taken out and naturally cooled to room temperature to obtain flame-retardant and weather-resistant foamed polypropylene composite material.

[0024] Example 2 (1) According to the weight parts, 90 parts of polypropylene, 10 parts of polyethylene, 10 parts of flame retardant (6 parts of triazine charring agent, 2 parts of ammonium polyphosphate, 2 parts of melamine polyphosphate), 4 parts of synergist (2 parts of nano-layered metal carbide, 2 parts of hindered amine light stabilizer), 5 parts of azodicarbonamide, 0.8 parts of trimethylolpropane triacrylate, and 1 part of antioxidant 1010 are put into a twin-screw extruder, melted and mixed evenly at a certain temperature, and extruded into sheets to obtain polypropylene pre-crosslinked master sheets; the processing temperature of each section of the twin-screw extruder is set as follows: feeding section 160℃, melting section 180℃, homogenization section 190℃, and screw speed 80rpm; (2) The obtained pre-crosslinked master sheet is subjected to electron beam irradiation under specified dose conditions to produce a crosslinking reaction and obtain a pre-foamed polypropylene master sheet; the irradiation dose is 40 kGy and the irradiation voltage is 2.5 MeV; (3) The pre-foamed polypropylene master sheet is placed in a high-temperature horizontal foaming furnace and foamed at 235°C. After foaming, it is taken out and naturally cooled to room temperature to obtain flame-retardant and weather-resistant foamed polypropylene composite material.

[0025] Example 3 (1) By weight, 85 parts of polypropylene, 15 parts of polyethylene, 20 parts of flame retardant (10 parts of triazine charring agent, 5 parts of ammonium polyphosphate, 5 parts of melamine polyphosphate), 3.5 parts of synergist (1.5 parts of nano-layered metal carbide, 2 parts of hindered amine light stabilizer), 8 parts of azodicarbonamide, 2 parts of trimethylolpropane triacrylate, and 0.6 parts of antioxidant 1010 are added to a twin-screw extruder, melted and mixed evenly at a certain temperature, and extruded into sheets to obtain polypropylene pre-crosslinked master sheets; the processing temperature of each section of the twin-screw extruder is set as follows: feeding section 160℃, melting section 180℃, homogenization section 190℃, and screw speed 120rpm; (2) The obtained pre-crosslinked master sheet is subjected to electron beam irradiation under specified dose conditions to produce a crosslinking reaction and obtain a pre-foamed polypropylene master sheet; the irradiation dose is 60 kGy and the irradiation voltage is 2.0 MeV; (3) The pre-foamed polypropylene master sheet is placed in a high-temperature horizontal foaming furnace and foamed at 250°C. After foaming, it is taken out and naturally cooled to room temperature to obtain flame-retardant and weather-resistant foamed polypropylene composite material.

[0026] Example 4 The method is basically the same as in Example 1, except that 1 part of nanolayered metal carbide and 1.5 parts of hindered amine light stabilizer are replaced with 2 parts of nanolayered metal carbide and 1 part of hindered amine light stabilizer.

[0027] Example 5 The process is basically the same as in Example 1, except that 16 parts of flame retardant (8 parts of triazine charring agent, 4 parts of ammonium polyphosphate, and 4 parts of melamine polyphosphate) are replaced with 15 parts of flame retardant (5 parts of triazine charring agent, 5 parts of ammonium polyphosphate, and 5 parts of melamine polyphosphate).

[0028] Example 6 The method is basically the same as in Example 5, except that 1 part of nanolayered metal carbide and 1.5 parts of hindered amine light stabilizer are replaced with 2 parts of nanolayered metal carbide and 1 part of hindered amine light stabilizer.

[0029] Example 7 The method is basically the same as in Example 1, except that 1 part of nanolayered metal carbide and 1.5 parts of hindered amine light stabilizer are replaced with 1.5 parts of nanolayered metal carbide and 1 part of hindered amine light stabilizer.

[0030] Example 8 The process is basically the same as in Example 1, except that the feeding section 160°C, melting section 180°C, and homogenization section 190°C are replaced with the feeding section 165°C, melting section 185°C, and homogenization section 190°C.

[0031] Comparative Example 1 The process is basically the same as in Example 1, except that 16 parts of flame retardant (8 parts of triazine charring agent, 4 parts of ammonium polyphosphate, and 4 parts of melamine polyphosphate) are replaced with 16 parts of traditional intumescent flame retardant (8 parts of pentaerythritol, 4 parts of ammonium polyphosphate, and 4 parts of melamine polyphosphate).

[0032] Comparative Example 2 It is basically the same as Example 1, except that: nanolayered metal carbides are not used.

[0033] The components and their contents used in Examples 1-8 and Comparative Examples 1-2 are summarized in Table 1 below: Table 1

[0034] The polypropylene composite materials prepared in Examples 1-8 and Comparative Examples 1-2 were subjected to flame retardancy and weather resistance tests. The specific test methods are as follows: Flame retardancy rating: conducted according to UL94 HBF horizontal burning test for foam materials, sample size 150mm×50mm×5mm; Oxygen index: conducted according to GB / T 2406.2-2009, sample size 100mm×10mm×4mm; Tensile strength: Tested according to GB / T 6344-2008, tensile speed 500 mm / min; Thermo-oxidative aging retention rate: carried out according to GB / T 7141-2021, thermo-oxidative aging at 120℃ for 1000h, and the tensile strength retention rate was calculated. UV aging retention rate: The process was carried out in accordance with GB / T 16422.3-2014, using a UVB-313 UV lamp, and continuously irradiated at 60℃ for 168 hours to calculate the tensile strength retention rate. Apparent density: determined according to GB / T 6343-2009, with sample size 100mm×100mm.

[0035] The test results are shown in Table 2, as follows: Table 2

[0036] As can be seen from the test results of Example 1 and Comparative Example 1 in Table 2, compared with the preparation of polypropylene composite materials using traditional intumescent flame retardants, the polypropylene composite materials prepared using the compound intumescent flame retardant of the present invention, which is composed of triazine charring agent, ammonium polyphosphate, and melamine polyphosphate, can achieve the UL94 level HF-1 burning rating and have a higher oxygen index. This indicates that the intumescent flame retardant prepared by the present invention can form a dense and stable intumescent char layer, effectively insulating heat and oxygen, and improving the flame retardant performance of the material. To a certain extent, it can also improve the tensile strength and the tensile strength retention rate after thermo-oxidative aging and UV aging, and reduce the apparent density, indicating good mechanical properties, strong structural load-bearing capacity, high weather resistance, and good lightweight characteristics.

[0037] The test results of Example 1 and Comparative Example 2 show that if the nano-layered metal carbide in the synergist is not used, the tensile strength and weather resistance retention rate of the polypropylene composite material are low. This indicates that the present invention can play a synergistic role in enhancing mechanical properties and weather resistance by using nano-layered metal carbide and hindered amine light stabilizer as synergists, thus ensuring the structural integrity after foaming.

[0038] As can be seen from the test results of Examples 1-8, the polypropylene composite material prepared by the method provided by the present invention has a high flame retardant rating and oxygen index, which can effectively prevent the spread of flames and significantly reduce the risk of fire. Moreover, the halogen-free system is more environmentally friendly. The high tensile strength and high tensile strength retention rate after thermo-oxidative aging and UV aging indicate good mechanical properties, strong structural load-bearing capacity, and good weather resistance, giving the material excellent long-term service life and environmental stability. The relatively low apparent density indicates that it maintains good lightweight characteristics, which can further expand its application advantages in weight-sensitive fields such as automobiles, construction, and outdoor facilities.

[0039] The above embodiments are only for illustrating the technical concept and features of the present invention, and are intended to enable those skilled in the art to understand the content of the present invention and implement it. They should not be used to limit the scope of protection of the present invention. All equivalent changes or modifications made in accordance with the spirit and essence of the present invention should be covered within the scope of protection of the present invention.

Claims

1. A flame-retardant and weather-resistant foamed polypropylene composite material, characterized in that, It contains the following components in parts by weight: 50-90 parts polypropylene, 10-50 parts polyethylene, 5-20 parts flame retardant, 1-10 parts synergist, 2-15 parts foaming agent, 0.5-3 parts radiation sensitizer, and 0.5-2 parts antioxidant. The flame retardant is an intumescent flame retardant, which is prepared by combining triazine-based charring agent, ammonium polyphosphate, and melamine polyphosphate.

2. The flame-retardant and weather-resistant foamed polypropylene composite material according to claim 1, characterized in that, The synthesis of the triazine-based char-forming agent includes the following steps: (1) Add cyanuric chloride and organic solvent to a flask, stir and dissolve under ice bath, then slowly add ethanolamine to the flask. After the addition is complete, add a small amount of inorganic base solution to the reaction system and continue stirring in an ice bath for 1-3 hours. When the reaction is complete, intermediate one is obtained. (2) Heat the intermediate obtained in step (1) to 50-60℃, and then slowly add a mixed solution of 4,4'-diaminodiphenyl sulfone and organic solvent to the reaction system. After the addition is completed, add a small amount of inorganic base solution to the reaction system and keep the reaction at the temperature for 2-5 hours. After the reaction is completed, intermediate two is obtained. (3) Heat the intermediate obtained in step (2) to 80-100℃, and then slowly add the solution obtained by piperazine and organic solvent. After the addition is complete, add a small amount of inorganic base solution to the reaction system and continue the reaction at this temperature for 5-10 hours. After the reaction is complete, perform post-treatment to obtain triazine char-forming agent.

3. The flame-retardant and weather-resistant foamed polypropylene composite material according to claim 2, characterized in that, The molar ratio of the added cyanuric chloride, ethanolamine and 4,4'-diaminodiphenyl sulfone is 2:(2-2.5):

1.

4. The flame-retardant and weather-resistant foamed polypropylene composite material according to claim 1, characterized in that, The synthesis of the flame retardant includes the following steps: In a high-speed mixer, triazine charring agent, ammonium polyphosphate, and melamine polyphosphate are mixed at 80-100℃ in a ratio of ammonium polyphosphate:melamine polyphosphate:triazine charring agent of (2-3):1:1 to obtain an intumescent flame retardant.

5. The flame-retardant and weather-resistant foamed polypropylene composite material according to claim 1, characterized in that, The synergist comprises nanolayered metal carbides and hindered amine light stabilizers.

6. The flame-retardant and weather-resistant foamed polypropylene composite material according to claim 5, characterized in that, The synthesis of the nanolayered metal carbide includes the following steps: (1) Dissolve lithium fluoride in dilute hydrochloric acid solution, then slowly add titanium aluminum carbide, stir at 35-45℃ for 20-30h, after stirring, centrifuge the obtained substance and wash with deionized water until the pH value of the supernatant is neutral, redisperse the obtained precipitate in deionized water, sonicate under ice bath for 20-30min, and finally centrifuge and dry to obtain nano-suspension; (2) Place the nano-suspension obtained in step (1) in a flask, add an organic solvent, and stir at room temperature for 10-15 min. Then add a silane coupling agent and stir at room temperature for 10-15 h. After the reaction is completed, perform post-treatment to obtain nano-layered metal carbides.

7. The flame-retardant and weather-resistant foamed polypropylene composite material according to claim 5, characterized in that, The weight ratio of the nanolayered metal carbide to the hindered amine light stabilizer is 1:(1-1.5).

8. The flame-retardant and weather-resistant foamed polypropylene composite material according to claim 1, characterized in that, The foaming agent is at least one of azodicarbonamide, p-toluenesulfonamide, N,N'-dinitrospentamethylenetetramine, trinitrosomethylenetriamine, triphosphatidyltriazine, azobisisobutyronitrile, and barium azodicarbonate; the irradiation sensitizer is at least one of trimethylolpropane triacrylate, dipentaerythritol hexaacrylate, triallyl isocyanurate, ethoxylated trimethylolpropane triacrylate, N,N'-m-phenylenebismaleimide, triallyl isocyanurate, and trimethylolpropane trimethacrylate.

9. A method for preparing a flame-retardant and weather-resistant foamed polypropylene composite material according to any one of claims 1-8, characterized in that, Includes the following steps: (1) According to the weight parts, polypropylene, polyethylene, flame retardant, synergist, foaming agent, radiation sensitizer and antioxidant are put into a twin-screw extruder, melted and mixed evenly at a certain temperature, and extruded into sheets to obtain polypropylene pre-crosslinked master sheets; the processing temperature of the extruder should be lower than the decomposition temperature of the foaming agent; (2) The obtained pre-crosslinked master sheet is subjected to electron beam irradiation under specified dosage conditions to produce a crosslinking reaction and obtain a pre-foamed polypropylene master sheet; (3) The pre-foamed polypropylene master sheet is placed in a heating environment. Under conditions higher than the decomposition temperature of the foaming agent, the foaming agent decomposes and causes the master sheet to foam, thus obtaining a flame-retardant and weather-resistant foamed polypropylene composite material.

10. The method for preparing a flame-retardant and weather-resistant foamed polypropylene composite material according to claim 9, characterized in that, In step (2), the irradiation dose is 10-100 kGy and the irradiation voltage is 0.5-3.0 MeV; in step (3), the decomposition temperature of the foaming agent is 200-260℃.

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