Lightweight carbon fiber composite material and preparation method and application thereof

Abstract

The application discloses a kind of lightweight carbon fiber composite material and preparation method and application, belong to composite material technical field, the lightweight carbon fiber composite material includes following weight parts raw materials: epoxy resin 100 parts, modified carbon fiber 6-10 parts, amino acid modified ammonium polyphosphate 5-8 parts, diluent 15-20 parts, accelerator 0.5-2 parts, curing agent 30-35 parts;The modified carbon fiber is obtained by surface modification of branched urea-based silane coupling agent to carbon fiber, then complexed with rare earth ions, the modified carbon fiber and amino acid modified ammonium polyphosphate are introduced in the composite material of the application, and the synergistic effect of the mutual coordination between components makes the composite material realize the synergistic promotion of mechanical properties and flame retardant performance, and can be widely applied in bridge reinforcement, high-rise building, water conservancy facilities and other engineering fields with strict requirements on lightweight high-strength and fire safety.

Description

Technical Field

[0001] This invention belongs to the field of composite material technology, specifically relating to a lightweight carbon fiber composite material, its preparation method, and its application. Background Technology

[0002] In recent years, with the rapid development of infrastructure construction, complex projects such as large bridges, water conservancy facilities, and high-rise buildings are increasing, placing higher demands on the performance of building materials. Epoxy resin, due to its excellent adhesion, corrosion resistance, and thermal stability, is widely used in building adhesives, gap filling, and structural reinforcement. However, pure epoxy resin is brittle and has poor impact resistance after curing, making it difficult to meet the mechanical requirements of load-bearing structures. Carbon fiber, with its high specific strength, high elastic modulus, and fatigue resistance, is often incorporated into the resin matrix as a reinforcing phase to form carbon fiber reinforced polymer composites, thereby improving the mechanical properties and thermal stability of the resin matrix.

[0003] In existing technologies, carbon fiber / epoxy resin composites have shown promising application prospects in bridge reinforcement, seismic repair of high-rise buildings, and riverbank protection. For example, by combining chopped carbon fibers or carbon fiber cloth with epoxy resin, load-bearing capacity can be effectively shared and crack propagation limited.

[0004] However, the epoxy resin matrix is ​​brittle after curing and has weak interfacial bonding with carbon fibers, making the composite material prone to matrix cracking and fiber debonding, resulting in mechanical properties that fail to meet application requirements. Therefore, developing a carbon fiber composite material with excellent mechanical properties is of great significance. Summary of the Invention

[0005] One of the objectives of this invention is to provide a lightweight carbon fiber composite material to solve the problem of poor mechanical properties of existing carbon fiber epoxy resin composite materials.

[0006] The second objective of this invention is to provide a method for preparing the above-mentioned lightweight carbon fiber composite material.

[0007] The third objective of this invention is to provide applications of the aforementioned lightweight carbon fiber composite material.

[0008] The objective of this invention can be achieved through the following technical solutions: A lightweight carbon fiber composite material comprises the following raw materials in parts by weight: 100 parts epoxy resin, 6-10 parts modified carbon fiber, 5-8 parts amino acid modified ammonium polyphosphate, 15-20 parts diluent, 0.5-2 parts accelerator, and 30-35 parts curing agent.

[0009] The modified carbon fiber is obtained by surface modification of carbon fiber with a branched urea-based silane coupling agent, followed by complexation with rare earth ions.

[0010] Furthermore, the modified carbon fiber preparation steps are as follows: S1. Add the branched urea-silane coupling agent to the ethanol solution and stir until uniform. Then add the acidified carbon fiber and stir at 55-65℃ for 6-12 hours. Filter and dry the filter cake to obtain the intermediate product. S2. Add soluble rare earth salts to deionized water to obtain a rare earth salt solution, then add intermediate products, stir for 6-12 hours, filter, dry the filter cake, and obtain modified carbon fibers.

[0011] Furthermore, the amount of the branched urea-silane coupling agent mentioned in S1 is 2-5% of the mass of the acidified carbon fiber.

[0012] Furthermore, the ethanol solution has a mass fraction of 90-95%.

[0013] Furthermore, the ratio of soluble rare earth salt, deionized water, and intermediate product in S2 is 0.5-2g: 100-200mL: 5-10g.

[0014] Furthermore, the soluble rare earth salt is at least one of lanthanum nitrate, cerium nitrate, lanthanum chloride, and cerium chloride.

[0015] Furthermore, the branched urea-based silane coupling agent is obtained by reacting the amino group in branched polyethyleneimine with the isocyanate group in isocyanate-based siloxane to form a urea group.

[0016] Further, the isocyanate-based siloxane is at least one selected from 3-isocyanate-propyltriethoxysilane, 3-isocyanate-propylmethyldimethoxysilane, 3-isocyanate-propylmethyldiethoxysilane, and 3-isocyanate-propyltrimethoxysilane.

[0017] Furthermore, the preparation steps of the branched urea-silane coupling agent are as follows: Branched polyethyleneimine was added to anhydrous N,N-dimethylformamide and stirred until homogeneous. Then, isocyanate-based siloxane was added, and the mixture was stirred and reacted at 55-65°C for 12 hours under nitrogen protection. After the reaction was completed, N,N-dimethylformamide was removed by vacuum distillation to obtain a branched urea-based silane coupling agent.

[0018] Furthermore, the molar ratio of the branched polyethyleneimine to the isocyanate-based siloxane is 1:4-8, and the molecular weight of the branched polyethyleneimine is 1800-25000.

[0019] Furthermore, the acidified carbon fiber is degummed carbon fiber oxidized with concentrated nitric acid. Concentrated nitric acid has strong oxidizing properties. After oxidation treatment, the surface roughness of the carbon fiber increases, and a large number of oxidized groups such as carboxyl and hydroxyl groups are formed on the surface, which enhances the surface activity of the carbon fiber.

[0020] Furthermore, the preparation steps of the acidified carbon fiber are as follows: Short carbon fibers are immersed in acetone-ethanol solution for 24-48 hours to complete the degumming step. Then, they are transferred to concentrated nitric acid solution for 3-5 hours. Finally, they are taken out and washed with acetone and deionized water in sequence, and then dried to obtain acidified carbon fibers.

[0021] Furthermore, the acetone-ethanol solution is composed of acetone and anhydrous ethanol in a volume ratio of 1:1.

[0022] Furthermore, the concentrated nitric acid has a mass fraction of 65-68%.

[0023] Furthermore, the chopped carbon fibers have a diameter of 6-7 μm and a length of 1-10 mm.

[0024] Furthermore, the raw materials for preparing the amino acid-modified ammonium polyphosphate include amino acids and ammonium polyphosphate, with a mass ratio of amino acids to ammonium polyphosphate of 1:2-4.

[0025] Ammonium polyphosphate modified with amino acids was prepared by ion exchange. The organic shell of amino acids can effectively improve the interfacial compatibility between ammonium polyphosphate and the resin matrix, and reduce stress concentration caused by the agglomeration of inorganic fillers. The amino acid surface is rich in amino and carboxyl groups, which can serve as efficient char-forming agents and gas sources. Together with the acid source of ammonium polyphosphate, they form an integrated intumescent flame retardant system. In addition, the carboxyl groups and other groups carried by amino acids can form coordination complexes with rare earth ions on the surface of modified carbon fibers. These metal ion coordination bonds can act as reversible sacrificial bonds in composite materials. When subjected to external force, the coordination bonds break preferentially to dissipate energy, and can reform after the external force is released, thereby improving the impact toughness of the material.

[0026] Furthermore, the amino acid is at least one selected from arginine, lysine, histidine, cysteine, and methionine.

[0027] Furthermore, the preparation steps of the amino acid-modified ammonium polyphosphate are as follows: Amino acids and ammonium polyphosphate were added together to a 90-95 wt% ethanol solution and reacted at 75-80℃ for 4-6 h under nitrogen protection. After the reaction was completed, the mixture was cooled to room temperature, filtered, and the filter cake was washed with a 90-95 wt% ethanol solution. The washing product was dried at 60℃ to constant weight to obtain amino acid-modified ammonium polyphosphate.

[0028] Furthermore, the epoxy resin is bisphenol A type epoxy resin E44 and / or bisphenol A epoxy resin E51.

[0029] Further, the diluent is at least one selected from butyl glycidyl ether, 1,4-butanediol diglycidyl ether, ethylene glycol diglycidyl ether, phenyl glycidyl ether, 1,6-hexanediol diglycidyl ether, and neopentyl glycol diglycidyl ether.

[0030] Furthermore, the accelerator is 2,4,6-tris(dimethylaminomethyl)phenol.

[0031] Furthermore, the curing agent is at least one selected from diaminodiphenyl sulfone, diaminodiphenylmethane, and dicyandiamide.

[0032] The preparation method of the above-mentioned lightweight carbon fiber composite material includes the following steps: Mix epoxy resin and diluent evenly, then add modified carbon fiber and amino acid-modified ammonium polyphosphate, stir and disperse for 20-30 minutes, then add accelerator and curing agent, continue stirring for 5-10 minutes, finally place the mixture in a mold, vacuum degas and cure to obtain lightweight carbon fiber composite material.

[0033] Furthermore, the vacuum degassing time is 10-24 hours, and the vacuum degree is ≤133 Pa.

[0034] Furthermore, the curing conditions are: 80℃ for 1-2 hours, 120℃ for 2-3 hours, and 140℃ for 2-4 hours.

[0035] The above-mentioned lightweight carbon fiber composite materials are used in the construction industry.

[0036] Furthermore, the aforementioned carbon fiber composite materials can be used in bridge construction to reduce structural weight and improve durability and load-bearing capacity. In high-rise buildings, carbon fiber composite materials can be used to reinforce structures and improve seismic resistance.

[0037] The beneficial effects of this invention are: 1. This invention provides a lightweight carbon fiber composite material, in which modified carbon fiber and amino acid-modified ammonium polyphosphate are introduced. The components work together in a coordinated manner to achieve a synergistic improvement in mechanical properties and flame retardant properties. It can be widely used in engineering fields with stringent requirements for lightweight, high strength and fire safety, such as bridge reinforcement, high-rise buildings, and water conservancy facilities.

[0038] 2. In this invention, the modified carbon fiber is obtained by surface modification of carbon fiber with a branched urea-based silane coupling agent, followed by complexation with rare earth ions. The hyperbranched structure formed by the reaction of branched polyethyleneimine and isocyanate silane constructs an active interface layer rich in amino and urea groups on the surface of the carbon fiber. This interface layer enhances the interfacial bonding strength between the fiber and epoxy resin through chemical bonding, and absorbs and dissipates impact energy by utilizing the flexible segment structure of the hyperbranched polymer, thereby improving the toughness of the composite material. In addition, the rare earth ions chelated on the surface can catalyze the formation of carbon during combustion, which helps to improve the flame retardant performance of the composite material.

[0039] 3. In this invention, the organic shell layer on the surface of amino acid-modified ammonium polyphosphate can improve the interfacial compatibility between ammonium polyphosphate and the resin matrix, reduce stress concentration, and the amino and carboxyl groups contained in the amino acids can act as char-forming agents and gas sources, forming an intumescent flame-retardant system with the acid source of ammonium polyphosphate, which helps to improve the flame-retardant performance of the composite material. At the same time, the carboxyl groups in the amino acids can form coordination complexes with rare earth ions on the surface of modified carbon fibers. These coordination bonds can preferentially break and dissipate energy under external force, and reform after the external force is released, thereby improving the impact toughness of the material. Detailed Implementation

[0040] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0041] The following is a detailed description with reference to specific examples.

[0042] Preparation Example 1 A modified carbon fiber, prepared by the following steps: S1. Add 0.2g of branched urea-silane coupling agent to 100mL of 90wt% ethanol solution and stir until homogeneous. Then add 10g of acidified carbon fiber, stir at 55℃ for 6h, filter, dry the filter cake, and obtain the intermediate product. S2. Add 0.5g of cerium chloride to 100mL of deionized water to obtain a rare earth salt solution, then add 5g of intermediate product, stir for 6h, filter, dry the filter cake to obtain modified carbon fiber.

[0043] The preparation steps for branched urea-silane coupling agents are as follows: 0.6 mmol of branched polyethyleneimine with a molecular weight of 1800 was added to 30 mL of anhydrous N,N-dimethylformamide and stirred until homogeneous. Then, 2.4 mmol of 3-isocyanopropyltriethoxysilane was added. The mixture was stirred at 55 °C for 12 h under nitrogen protection. After the reaction was completed, N,N-dimethylformamide was removed by vacuum distillation to obtain a branched ureosilane coupling agent.

[0044] The preparation steps of acidified carbon fiber are as follows: Short carbon fibers with a diameter of 6-7 μm and a length of 1-10 mm were immersed in an acetone-ethanol solution for 24 hours and then removed to complete the degumming step. The acetone-ethanol solution consisted of acetone and anhydrous ethanol in a volume ratio of 1:1. The carbon fibers were then transferred to 65 wt% concentrated nitric acid for 3 hours and then removed and washed with acetone and deionized water in sequence. Finally, the carbon fibers were dried to obtain acidified carbon fibers.

[0045] Preparation Example 2 A modified carbon fiber, prepared by the following steps: S1. Add 0.35g of branched urea-silane coupling agent to 100mL of 95wt% ethanol solution and stir until homogeneous. Then add 10g of acidified carbon fiber, stir at 60℃ for 8h, filter, dry the filter cake to obtain the intermediate product. S2. Add 1g of lanthanum chloride to 150mL of deionized water to obtain a rare earth salt solution, then add 8g of intermediate product, stir for 8h, filter, dry the filter cake to obtain modified carbon fiber.

[0046] The preparation steps for branched urea-silane coupling agents are as follows: 0.6 mmol of branched polyethyleneimine with a molecular weight of 1800 was added to 50 mL of anhydrous N,N-dimethylformamide and stirred until homogeneous. Then, 3.6 mmol of 3-isocyanopropyltrimethoxysilane was added. The mixture was stirred at 60 °C for 12 h under nitrogen protection. After the reaction was completed, N,N-dimethylformamide was removed by vacuum distillation to obtain a branched ureosilane coupling agent.

[0047] The preparation steps of acidified carbon fiber are as follows: Short carbon fibers with a diameter of 6-7 μm and a length of 1-10 mm were immersed in an acetone-ethanol solution for 36 hours and then removed to complete the degumming step. The acetone-ethanol solution consisted of acetone and anhydrous ethanol in a volume ratio of 1:1. The carbon fibers were then transferred to 65 wt% concentrated nitric acid and immersed for 4 hours. Finally, the carbon fibers were removed and washed with acetone and deionized water in sequence, and then dried to obtain acidified carbon fibers.

[0048] Preparation Example 3 A modified carbon fiber, prepared by the following steps: S1. Add 0.5g of branched urea-silane coupling agent to 100mL of 95wt% ethanol solution and stir until homogeneous. Then add 10g of acidified carbon fiber, stir at 65℃ for 12h, filter, dry the filter cake, and obtain the intermediate product. S2. Add 2g of cerium chloride to 200mL of deionized water to obtain a rare earth salt solution, then add 10g of intermediate product, stir for 12h, filter, dry the filter cake to obtain modified carbon fiber.

[0049] The preparation steps for branched urea-silane coupling agents are as follows: 0.6 mmol of branched polyethyleneimine with a molecular weight of 1800 was added to 60 mL of anhydrous N,N-dimethylformamide and stirred until homogeneous. Then, 4.8 mmol of 3-isocyanopropylmethyldimethoxysilane was added. The mixture was stirred at 65 °C for 12 h under nitrogen protection. After the reaction was completed, N,N-dimethylformamide was removed by vacuum distillation to obtain a branched urea-silane coupling agent.

[0050] The preparation steps of acidified carbon fiber are as follows: Short carbon fibers with a diameter of 6-7 μm and a length of 1-10 mm were immersed in an acetone-ethanol solution for 48 hours and then removed to complete the degumming step. The acetone-ethanol solution consisted of acetone and anhydrous ethanol in a volume ratio of 1:1. The carbon fibers were then transferred to 68 wt% concentrated nitric acid for 5 hours. Finally, the carbon fibers were removed and washed with acetone and deionized water in sequence, and then dried to obtain acidified carbon fibers.

[0051] Compare with Example 1 A modified carbon fiber, prepared by the following steps: 0.2 g of branched urea-silane coupling agent was added to 100 mL of 90 wt% ethanol solution and stirred until homogeneous. Then, 10 g of acidified carbon fiber was added, and the mixture was stirred at 55 °C for 6 h. After filtration, the filter cake was dried to obtain modified carbon fiber. The preparation process of the branched urea-silane coupling agent and acidified carbon fiber was the same as in Preparation Example 1.

[0052] Compare with Example 2 A modified carbon fiber, prepared by the following steps: 0.2 g of γ-aminopropyltriethoxysilane was added to 100 mL of 90 wt% ethanol solution and stirred until homogeneous. Then, 10 g of acidified carbon fiber was added, and the mixture was stirred at 55 °C for 6 h. After filtration, the filter cake was dried to obtain modified carbon fiber. The preparation process of acidified carbon fiber was the same as in Preparation Example 1.

[0053] Compare with Example 3 A modified carbon fiber, prepared by the following steps: 2g of cerium chloride and lanthanum chloride were added to 200mL of deionized water to obtain a rare earth salt solution. Then, 10g of acidified carbon fiber was added, and the mixture was stirred for 12h. After filtration, the filter cake was dried to obtain modified carbon fiber. The preparation process of acidified carbon fiber was the same as in Preparation Example 1.

[0054] Example 1 A lightweight carbon fiber composite material comprises the following raw materials in parts by weight: 100 parts of bisphenol A type epoxy resin E44, 6 parts of modified carbon fiber of Preparation Example 1, 5 parts of amino acid modified ammonium polyphosphate, 15 parts of 1,4-butanediol diglycidyl ether, 0.5 parts of 2,4,6-tris(dimethylaminomethyl)phenol, and 30 parts of diaminodiphenyl sulfone.

[0055] The preparation steps for amino acid-modified ammonium polyphosphate are as follows: 1g of arginine and 2g of ammonium polyphosphate were added to 50mL of 95wt% ethanol solution. The mixture was reacted at 75℃ for 4h under nitrogen protection. After the reaction was completed, the mixture was cooled to room temperature, filtered, and the filter cake was washed with 95wt% ethanol solution. The washing product was dried at 60℃ to constant weight to obtain amino acid-modified ammonium polyphosphate.

[0056] The preparation method of the above-mentioned lightweight carbon fiber composite material includes the following steps: The epoxy resin and diluent were mixed evenly, then modified carbon fiber and amino acid-modified ammonium polyphosphate were added and stirred for 20 minutes. Finally, the accelerator and curing agent were added and stirred for another 5 minutes. The mixture was then placed in a mold and vacuum degassed at 120 Pa for 10 hours, treated at 80℃ for 1 hour, 120℃ for 2 hours, and 140℃ for 2 hours to obtain the lightweight carbon fiber composite material.

[0057] Example 2 A lightweight carbon fiber composite material comprises the following raw materials in parts by weight: 100 parts of bisphenol A type epoxy resin E44, 8 parts of modified carbon fiber of Preparation Example 1, 6.5 parts of amino acid modified ammonium polyphosphate, 18 parts of 1,4-butanediol diglycidyl ether, 1 part of 2,4,6-tris(dimethylaminomethyl)phenol, and 32 parts of diaminodiphenyl sulfone.

[0058] The preparation steps for amino acid-modified ammonium polyphosphate are the same as in Example 1.

[0059] The preparation method of the above-mentioned lightweight carbon fiber composite material includes the following steps: The epoxy resin and diluent were mixed evenly, then modified carbon fiber and amino acid-modified ammonium polyphosphate were added and stirred and dispersed for 25 minutes. Finally, the accelerator and curing agent were added and stirred for another 8 minutes. The mixture was then placed in a mold and vacuum degassed at 120 Pa for 14 hours, treated at 80℃ for 1.5 hours, 120℃ for 2.5 hours, and 140℃ for 3 hours to obtain the lightweight carbon fiber composite material.

[0060] Example 3 A lightweight carbon fiber composite material comprises the following raw materials in parts by weight: 100 parts of bisphenol A type epoxy resin E44, 10 parts of modified carbon fiber of Preparation Example 1, 8 parts of amino acid modified ammonium polyphosphate, 20 parts of 1,4-butanediol diglycidyl ether, 2 parts of 2,4,6-tris(dimethylaminomethyl)phenol, and 35 parts of diaminodiphenyl sulfone.

[0061] The preparation steps for amino acid-modified ammonium polyphosphate are the same as in Example 1.

[0062] The preparation method of the above-mentioned lightweight carbon fiber composite material includes the following steps: The epoxy resin and diluent were mixed evenly, then modified carbon fiber and amino acid-modified ammonium polyphosphate were added and stirred and dispersed for 30 minutes. Finally, the accelerator and curing agent were added and stirred for another 10 minutes. The mixture was then placed in a mold and vacuum degassed at 120 Pa for 24 hours, treated at 80℃ for 2 hours, treated at 120℃ for 3 hours, and treated at 140℃ for 4 hours to obtain the lightweight carbon fiber composite material.

[0063] Example 4 A lightweight carbon fiber composite material, compared with Example 1, differs only in that the preparation steps of amino acid-modified ammonium polyphosphate in this example are as follows: 1 g of lysine and 3 g of ammonium polyphosphate were added to 60 mL of 93 wt% ethanol solution. The mixture was reacted at 78 °C for 5 h under nitrogen protection. After the reaction was completed, the mixture was cooled to room temperature, filtered, and the filter cake was washed with 93 wt% ethanol solution. The washing product was dried at 60 °C to constant weight to obtain amino acid modified ammonium polyphosphate.

[0064] Example 5 A lightweight carbon fiber composite material, compared with Example 1, differs only in that the preparation steps of amino acid-modified ammonium polyphosphate in this example are as follows: 1 g of cysteine ​​and 4 g of ammonium polyphosphate were added to 70 mL of 95 wt% ethanol solution. The mixture was reacted at 80 °C for 6 h under nitrogen protection. After the reaction was completed, the mixture was cooled to room temperature, filtered, and the filter cake was washed with 95 wt% ethanol solution. The washing product was dried at 60 °C to constant weight to obtain amino acid modified ammonium polyphosphate.

[0065] Example 6 A lightweight carbon fiber composite material, compared with Example 1, differs only in that the modified carbon fiber in Example 1 is replaced with an equal mass of the product obtained in Example 2.

[0066] Example 7 A lightweight carbon fiber composite material, which differs from Example 1 only in that the modified carbon fiber in Example 1 is replaced with an equal mass of the product obtained in Preparation Example 3.

[0067] Example 8 A lightweight carbon fiber composite material, compared with Example 2, differs only in that the modified carbon fiber in Example 2 is replaced with an equal mass of the product obtained in Preparation Example 3.

[0068] Comparative Example 1 A lightweight carbon fiber composite material, which differs from Example 1 only in that the modified carbon fiber in Example 1 is replaced with an equal mass of the product obtained in Comparative Example 1.

[0069] Comparative Example 2 A lightweight carbon fiber composite material, which differs from Example 1 only in that the modified carbon fiber in Example 1 is replaced with an equal mass of the product obtained in Comparative Example 2.

[0070] Comparative Example 3 A lightweight carbon fiber composite material, which differs from Example 1 only in that the modified carbon fiber in Example 1 is replaced with an equal mass of the product obtained in Comparative Example 3.

[0071] Comparative Example 4 A lightweight carbon fiber composite material, compared with Example 1, differs only in that the amino acid-modified ammonium polyphosphate in Example 1 is replaced with an equal mass of ammonium polyphosphate.

[0072] Comparative Example 5 A lightweight carbon fiber composite material, compared with Example 1, differs only in that the modified carbon fiber in Example 1 is replaced with an equal mass of the product obtained in Comparative Example 2, and the amino acid-modified ammonium polyphosphate is replaced with an equal mass of ammonium polyphosphate.

[0073] The lightweight carbon fiber composite materials obtained in Examples 1-8 and Comparative Examples 1-5 were subjected to performance tests, and the test procedures are as follows: Tensile property test: The test was conducted using a universal testing machine. The loading speed of the universal testing machine was set to 10 mm / min. The test procedure was in accordance with GB / T1447-2005 standard. Impact resistance test: The test is conducted using an impact testing machine, and the test process is conducted in accordance with the GB / T2571-1995 standard. Flame retardant performance test: The test was conducted using a limiting oxygen index meter, and the test process was conducted in accordance with the GB / T8924-2005 standard. The results are shown in Table 1: Table 1

[0074] As shown in Table 1, the lightweight carbon fiber composite materials obtained in Examples 1-8 of this application have a tensile strength of 57.0-60.0 MPa and an impact strength of 11.8-13.0 kJ / m. 2 The limiting oxygen index was 28.5-29.8%. As can be seen from the test results of Example 1 and Comparative Example 1, compared with the modified carbon fiber without rare earth ion chelation (Comparative Example 1), the composite material prepared by using rare earth ion chelated modified carbon fiber (Example 1) has higher tensile strength, impact strength and limiting oxygen index. This indicates that the rare earth ions chelated on the carbon fiber surface enhance the interfacial bonding and dissipate impact energy by forming coordination complexes with the carboxyl groups of amino acid modified ammonium polyphosphate through coordination complexation. On the other hand, they catalyze carbonization during combustion, thereby synergistically improving the mechanical properties and flame retardant properties of the composite material. Similarly, the test results of Example 1 and Comparative Examples 2-3 show that Comparative Example 2 uses ordinary silane KH550 to modify carbon fiber, and Comparative Example 3 uses rare earth ions to directly physically adsorb carbon fiber. Both have poor mechanical properties and flame retardant properties, indicating that the hyperbranched active interface layer constructed by the branched urea-based silane coupling agent is the key to achieving effective anchoring of rare earth ions, enhancing interfacial bonding and playing a toughening role. The test results of Example 1 and Comparative Example 4 show that when Comparative Example 4 uses unmodified ammonium polyphosphate instead of amino acid-modified ammonium polyphosphate, its limiting oxygen index and impact strength are significantly reduced. This indicates that the organic shell of amino acid-modified ammonium polyphosphate not only improves the interfacial compatibility with the resin matrix, but its amino and carboxyl groups can also act as char-forming agents and gas sources, forming an integrated intumescent flame retardant system with ammonium polyphosphate. At the same time, the coordination effect of carboxyl groups with rare earth ions further enhances the interfacial toughness.

[0075] As can be seen from the test results of Example 1 and Comparative Example 5, Comparative Example 5, which uses both ordinary silane KH550 modified carbon fiber and unmodified ammonium polyphosphate, has the lowest tensile strength, impact strength and limiting oxygen index among all samples, significantly lower than that of Example 1. This indicates that the present invention achieves multiple effects of interface reinforcement, toughening and flame retardancy through the synergistic combination of modified carbon fiber and amino acid modified ammonium polyphosphate, and each component is indispensable.

[0076] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.

[0077] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A lightweight carbon fiber composite material, characterized in that, Including the following parts by weight of raw materials: 100 parts epoxy resin, 6-10 parts modified carbon fiber, 5-8 parts amino acid modified ammonium polyphosphate, 15-20 parts diluent, 0.5-2 parts accelerator, and 30-35 parts curing agent; The modified carbon fiber is obtained by surface modification of carbon fiber with a branched urea-based silane coupling agent, followed by complexation with rare earth ions.

2. The lightweight carbon fiber composite material according to claim 1, characterized in that, The modified carbon fiber preparation steps are as follows: S1. Add the branched urea-silane coupling agent to the ethanol solution and stir until uniform. Then add the acidified carbon fiber and stir at 55-65℃ for 6-12 hours. Filter and dry the filter cake to obtain the intermediate product. S2. Add soluble rare earth salts to deionized water to obtain a rare earth salt solution, then add intermediate products, stir for 6-12 hours, filter, dry the filter cake, and obtain modified carbon fibers.

3. The lightweight carbon fiber composite material according to claim 2, characterized in that, The amount of branched urea-silane coupling agent mentioned in S1 is 2-5% of the mass of acidified carbon fiber.

4. The lightweight carbon fiber composite material according to claim 2, characterized in that, The ratio of soluble rare earth salt, deionized water, and intermediate product in S2 is 0.5-2g: 100-200mL: 5-10g, wherein the soluble rare earth salt is at least one of lanthanum nitrate, cerium nitrate, lanthanum chloride, and cerium chloride.

5. A lightweight carbon fiber composite material according to claim 1 or 2, characterized in that, The branched urea-based silane coupling agent is obtained by reacting the amino group in branched polyethyleneimine with the isocyanate group in isocyanate-based siloxane to form a urea group.

6. The lightweight carbon fiber composite material according to claim 5, characterized in that, The isocyanate-based siloxane is at least one selected from 3-isocyanate-propyltriethoxysilane, 3-isocyanate-propylmethyldimethoxysilane, 3-isocyanate-propylmethyldiethoxysilane, and 3-isocyanate-propyltrimethoxysilane.

7. The lightweight carbon fiber composite material according to claim 5, characterized in that, The preparation steps of the branched urea-silane coupling agent are as follows: Branched polyethyleneimine was added to anhydrous N,N-dimethylformamide and stirred until homogeneous. Then, isocyanate-based siloxane was added, and the mixture was stirred and reacted at 55-65°C for 12 hours under nitrogen protection. After the reaction was completed, N,N-dimethylformamide was removed by vacuum distillation to obtain a branched urea-based silane coupling agent.

8. The lightweight carbon fiber composite material according to claim 7, characterized in that, The molar ratio of the branched polyethyleneimine to isocyanate-based siloxane is 1:4-8, and the molecular weight of the branched polyethyleneimine is 1800-25000.

9. A method for preparing a lightweight carbon fiber composite material, characterized in that, The method for preparing the lightweight carbon fiber composite material according to any one of claims 1-8 comprises the following steps: Mix epoxy resin and diluent evenly, then add modified carbon fiber and amino acid-modified ammonium polyphosphate, stir and disperse for 20-30 minutes, then add accelerator and curing agent, continue stirring for 5-10 minutes, finally place the mixture in a mold, vacuum degas and cure to obtain lightweight carbon fiber composite material.

10. The application of the lightweight carbon fiber composite material as described in any one of claims 1-8 in the construction industry.

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