Modified carbon fiber composite material and preparation method and application thereof

Abstract

The application belongs to the field of carbon fiber reinforced materials, and particularly relates to a modified carbon fiber composite material and a preparation method and application thereof. By introducing a modifier X and magnesium hydroxide nanosheets, the mechanical properties and flame-retardant properties of the modified carbon fiber composite material are greatly improved, and the modified carbon fiber composite material can be used to prepare an integrally molded carbon fiber luggage.

Description

Technical Field

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

[0002] Carbon fiber is a fibrous carbon material with a micro-graphite crystal structure. It is a long, thin filament and possesses excellent properties, including high tensile strength (2-7 GPa), good compressive strength (up to 3 GPa), high tensile elastic modulus (200-900 GPa), low density (1.75-2.18 g / cm3), good temperature resistance, low thermal expansion, excellent electrical and thermal conductivity, and good chemical resistance. Based on the different precursor fibers used, carbon fiber can be mainly divided into three categories: cellulose-based carbon fiber, pitch-based carbon fiber, and polyacrylonitrile-based carbon fiber.

[0003] Because carbon fiber is a brittle material, it is rarely used alone and needs to be combined with other matrix materials to effectively utilize its excellent properties. Typically, carbon fiber is used as the reinforcement, with metals, ceramics, cement, carbon, resins, etc., as the matrix, and is prepared through a special process to obtain carbon fiber reinforced composite materials. Since cured epoxy resin is an amorphous and highly cross-linked polymer, it has low shrinkage during curing, low residual stress, and requires low processing pressure, making it the most common resin matrix. Carbon fiber reinforced epoxy resin composite materials obtained from it possess anisotropy and designability, material-structure integration, composite effects, and multifunctionality, and are widely used in luggage, aerospace, automotive, energy, sports, and medical fields. Taking carbon fiber suitcases as an example, the male-female snap-fit ​​opening and closing structure of this one-piece molded carbon fiber suitcase has many advantages: 1) Excellent convenience: The male-female snap-fit ​​structure is simple to operate, requiring no complicated opening steps. Users only need to easily align the male and female snaps to snap or separate them to quickly open and close the suitcase, greatly saving time and effort, even in hurried travel situations. 2) Significantly Lightweight: Applied to the one-piece molded carbon fiber suitcase, it minimizes weight while ensuring overall durability. 3) Stylish Appearance in Line with Trends: The simple and streamlined male-female interlocking structure complements the stylish appearance of the one-piece molded carbon fiber suitcase, meeting today's consumer demand for suitcases that are not only practical but also aesthetically pleasing, enhancing the overall quality and fashion sense of the product. 4) Stable and Reliable Structure: The tight-fitting male-female interlocking structure effectively prevents accidental opening during use, ensuring luggage safety and providing a stable and reliable closure.

[0004] Carbon fiber reinforced resin matrix composites consist of carbon fibers, a resin matrix, and an interfacial phase. Carbon fibers act as reinforcement, the resin matrix shapes the composite into a load-bearing structure, and the interfacial phase serves as a bridge connecting the fibers and the resin matrix, and a link for stress transfer. However, the low surface energy and inert chemical properties of raw carbon fibers lead to poor interfacial bonding with the matrix, limiting their application in various fields. Therefore, improving the surface activity of carbon fibers to enhance interfacial bonding strength has been a hot research topic. Summary of the Invention

[0005] The purpose of this invention is to provide a modified carbon fiber composite material, its preparation method, and its application, to solve the problems existing in the prior art, such as low surface energy of carbon fibers, inert chemical properties, poor interfacial bonding with the matrix, and poor flame retardant properties. To solve the above technical problems, this invention provides the following technical solution: A method for preparing a modified carbon fiber composite material includes the following steps: Step S1: Cut the carbon fiber into short carbon fibers, wash them with organic solvent, and vacuum dry them to obtain untreated short carbon fibers CFs; immerse the untreated short carbon fibers CFs in nitric acid solution for reaction, and after the reaction is completed, wash the carbon fibers repeatedly with deionized water until the pH value is neutral, and vacuum dry them to obtain acidified short carbon fibers CFs-COOH. Step S2: Add modifier X Add the organic solvent and water to a mixed solvent, then add the condensing agent HATU and stir until homogeneous to obtain a mixture; immerse the acidified short carbon fiber CFs-COOH in the above mixture; after immersion, repeatedly wash the carbon fiber with deionized water and vacuum dry to obtain the modified short carbon fiber CFs-X; Step S3: Add 20-30 parts of modified short carbon fiber CFs-X, 3-10 parts of magnesium hydroxide nanosheets, and 100-150 parts of diluent to a mixer and stir to obtain premix A; then add 90-120 parts of epoxy resin, 5-15 parts of curing agent, and 1-3 parts of antioxidant to premix A in sequence, and continue stirring to obtain premix B; Step S4: Place the premixed material B in a mold and put it in an oven for hot pressing and curing. After the mold cools down, remove the mold to obtain the modified carbon fiber composite material.

[0006] In some embodiments, the organic solvent in step S1 is selected from one or more of dichloromethane, acetone, THF, chloroform, and ethyl acetate; the organic solvent in step S2 is selected from one or more of dichloromethane, acetone, THF, chloroform, ethyl acetate, DMSO, DMF, and methanol.

[0007] In some embodiments, in step S1, the concentration of the nitric acid solution is 25-40 wt%; the length of the short carbon fiber is 1-10 mm; the mass-to-volume ratio of the untreated short carbon fiber (CFs) to the nitric acid solution is 1 g:(10-20) mL; the reaction temperature is 50-100 °C; and the reaction time is 1-10 h.

[0008] In some embodiments, in step S2, the mass-to-volume ratio of the modifier X to the mixed solvent is 1 g:(40~60) mL; the mass ratio of the modifier X to the acidified short carbon fiber CFs-COOH is 1:(2~5); the mass ratio of the modifier X to the condensing agent HATU is 1:(0.05~0.15); the soaking temperature is 50~80℃ and the soaking time is 1~5 h.

[0009] In some embodiments, in step S3, the curing agent is selected from one or more of ethylenediamine, hexamethylenediamine, diethylenetriamine, triethylenetetramine, diethylaminopropylamine, maleic anhydride, and phthalic anhydride; and the epoxy resin is selected from one or more of E-51, E-44, and F-51.

[0010] In some embodiments, in step S3, the antioxidant is selected from one or more of antioxidant 1010, antioxidant 168, and antioxidant 1076; the diluent is selected from one or more of acetone, n-butyl glycidyl ether, diglycidyl ether, and 1,4-butanediol diglycidyl ether.

[0011] In some implementations, the stirring temperature in step S3 is 50~100°C.

[0012] In some implementations, the curing conditions in step S4 are: curing at 80~100℃ for 1 hour, curing at 100~120℃ for 2 hours, and curing at 130~150℃ for 2 hours.

[0013] The present invention also provides a modified carbon fiber composite material, which is prepared by the above method.

[0014] The present invention also provides the application of the above-mentioned modified carbon fiber composite material in the preparation of integrally molded carbon fiber luggage.

[0015] The present invention has achieved the following beneficial effects: 1) This invention introduces modifier X The addition of magnesium hydroxide nanosheets significantly enhances the mechanical and flame-retardant properties of modified carbon fiber composites.

[0016] 2) This invention utilizes a chemical grafting method to introduce modifier X onto the surface of carbon fibers under the action of HATU accelerator. The introduced modifier X increases the surface active functional groups of the carbon fibers, promoting the wettability between the fiber and the resin matrix. Furthermore, the amino groups introduced onto the carbon fiber surface can undergo a curing and cross-linking reaction with the epoxy resin, significantly improving the compatibility between the fiber and the resin matrix, thereby enhancing mechanical properties. In addition, magnesium hydroxide nanosheets can increase the mechanical interlocking centers between the carbon fibers and the matrix, forming a strong mechanical interlocking effect, reducing stress concentration in the resin matrix, and enhancing interfacial bonding, thus improving mechanical properties.

[0017] 3) The modifier X used in this invention contains a triazine ring structure and has good flame retardant properties. It achieves the best flame retardant effect by combining with the inorganic flame retardant magnesium hydroxide. The modified carbon fiber composite material obtained by this invention has a limiting oxygen index as high as 40.8%. Detailed Implementation

[0018] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments. 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 skilled in the art without creative effort are within the scope of protection of the present invention.

[0019] The endpoints and any values ​​of the ranges described in this invention are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein. The raw materials and reagents used in the following examples are commercially available.

[0020] Example 1 A method for preparing a modified carbon fiber composite material includes the following steps: Step S1: The carbon fiber (T300, manufactured by Toray Industries, Japan, with 3K pores, a diameter of 7μm, and a density of 1.75g / cm³) is then... 3 Short carbon fibers with a length of approximately 3 mm were cut and placed in a round-bottom flask. They were then refluxed with acetone at 80°C for 24 h. After that, they were dried overnight in a vacuum oven at 80°C to obtain untreated short carbon fibers (CFs). Then, 20.0 g of the untreated short carbon fibers (CFs) were immersed in 200 mL of a 30 wt% nitric acid solution and reacted at 80°C for 5 h. The carbon fibers were then repeatedly washed with deionized water until the pH value was neutral. After vacuum drying overnight, they were obtained acidified short carbon fibers (CFs-COOH). Step S2: Add modifier X 5.0 g of the modified short carbon fiber CFs-COOH was added to a mixed solvent of THF (200 mL) and water (50 mL), followed by the addition of condensing agent HATU (0.3 g), and stirred until homogeneous to obtain a mixture. At 60 °C, 20.0 g of the acidified short carbon fiber CFs-COOH was immersed in the above mixture for 2 h. After the reaction was complete, the carbon fiber was repeatedly washed with deionized water and finally dried in a vacuum oven at 100 °C to obtain the modified short carbon fiber CFs-X. Step S3: Add 20 parts of modified short carbon fiber CFs-X, 5 parts of magnesium hydroxide nanosheets (model LY1-S, average particle size 0.9μm, average thickness 0.2μm, manufactured by Kyowa Corporation, Japan), and 100 parts of acetone to a mixer and stir at 50°C for 30 minutes to obtain premix A; then add 100 parts of epoxy resin (model WSR618, molecular weight between 350 and 400, manufactured by Nantong Xingchen Co., Ltd.), 10 parts of curing agent ethylenediamine, and 1 part of antioxidant 1010 to premix A in sequence, and continue stirring and mixing at 50°C for 30 minutes to obtain premix B; Step S4: Place the mixture B in a mold and put it in an oven for hot pressing and curing. The curing conditions are 1 hour at 80°C, 2 hours at 120°C, and 2 hours at 150°C. After the mold cools down, remove the mold to obtain the modified carbon fiber composite material.

[0021] Example 2 A method for preparing a modified carbon fiber composite material includes the following steps: Step S1: The carbon fiber (T300, manufactured by Toray Industries, Japan, with 3K pores, a diameter of 7μm, and a density of 1.75g / cm³) is then... 3 Short carbon fibers with a length of approximately 3 mm were cut and placed in a round-bottom flask. They were then refluxed with acetone at 80°C for 24 h. After that, they were dried overnight in a vacuum oven at 80°C to obtain untreated short carbon fibers (CFs). Then, 20.0 g of the untreated short carbon fibers (CFs) were immersed in a 40 wt% nitric acid solution (300 mL) and reacted at 70°C for 6 h. The carbon fibers were then repeatedly washed with deionized water until the pH value was neutral. After vacuum drying overnight, they were obtained acidified short carbon fibers (CFs-COOH). Step S2: Add modifier X 8.0 g of the modified short carbon fiber CFs-COOH was added to a mixed solvent of acetone (200 mL) and water (50 mL), and then 0.5 g of condensing agent HATU was added and stirred until homogeneous to obtain a mixture. At 55 °C, 20.0 g of acidified short carbon fiber CFs-COOH was immersed in the above mixture for 3 h. After the reaction was completed, the carbon fiber was repeatedly washed with deionized water and finally dried in a vacuum oven at 100 °C to obtain modified short carbon fiber CFs-X. Step S3: Add 25 parts of modified short carbon fiber CFs-X, 6 parts of magnesium hydroxide nanosheets (model LY1-S, average particle size 0.9μm, average thickness 0.2μm, manufactured by Kyowa Corporation, Japan), and 100 parts of acetone to a mixer and stir at 50°C for 30 minutes to obtain premix A; then add 100 parts of epoxy resin (model WSR618, molecular weight between 350 and 400, manufactured by Nantong Xingchen Co., Ltd.), 8 parts of curing agent hexamethylenediamine, and 2 parts of antioxidant 1076 to premix A in sequence, and continue stirring and mixing at 50°C for 30 minutes to obtain premix B; Step S4: Place the premixed material B in a mold and put it in an oven for hot pressing and curing. The curing conditions are 1 hour at 80℃, 2 hours at 120℃, and 2 hours at 150℃. After the mold cools down, remove the mold to obtain the modified carbon fiber composite material.

[0022] Comparative Example 1 Based on Example 2, steps S1 and S2 are omitted, and the modified short carbon fiber CFs-X in step S3 is replaced with the acidified short carbon fiber CFs-COOH described in step S1. Other operations and steps are the same as in Example 2.

[0023] Comparative Example 2 Based on Example 2, the magnesium hydroxide nanosheets in step S3 are omitted, and other operations and steps are the same as in Example 2.

[0024] Comparative Example 3 Based on Example 2, step S2 is... Replace with Other operations and steps are the same as in Example 2.

[0025] Performance testing The mechanical and flame-retardant properties of the modified carbon fiber composites obtained in Examples 1-2 and Comparative Examples 1-3 were tested according to the following standards: 1) Interlaminar Shear Strength: The interlaminar shear strength (ILSS) of the modified carbon fiber composite was obtained using the three-point short beam bending method on a Zwick Z100 universal testing machine in Germany, according to ASTM D2344 standard. The sensor was 100 kN. The specimen size was 25 mm × 6.5 mm × 2 mm, the testing speed was 2 mm / min, the span was 8 mm, and the test was conducted at room temperature. Five valid data points were selected from each group of specimens, and their average value was taken.

[0026] 2) Bending strength: According to ASTM D7624 standard, the bending strength and bending modulus of carbon fiber composites were obtained by the three-point bending method on a Zwick universal testing machine in Germany. The sensor was 1 kN, the sample size was 50 mm × 10 mm × 2 mm, the test speed was 1 mm / min, the span was 64 mm, and the test was carried out at room temperature. Five valid data points were selected from each group of samples and their average value was taken.

[0027] 3) Limiting oxygen index: Tested according to GB / T 2406.2-2009 "Determination of flammability by oxygen index method for plastics - Part 2: Room temperature test". The results are shown in Table 1.

[0028] Table 1 Performance Test Results As can be seen from the results of Examples 1-2 in Table 1, the modified carbon fiber composite material prepared by the present invention has excellent mechanical properties and flame retardant properties.

[0029] Specifically, by comparing Example 2 with Comparative Examples 1-3, it can be seen that the present invention introduces modifier X. The addition of magnesium hydroxide nanosheets significantly improves the mechanical and flame-retardant properties of modified carbon fiber composites. The main reason for this is: First, this invention utilizes a chemical grafting method to introduce modifier X onto the surface of carbon fibers under the action of HATU accelerator. The introduced modifier X can increase the surface active functional groups of carbon fibers, promote the wettability between the fiber and the resin matrix, and the amino groups introduced onto the carbon fiber surface can undergo a curing and crosslinking reaction with epoxy resin, greatly improving the compatibility between the fiber and the resin matrix, thereby enhancing mechanical properties.

[0030] Secondly, magnesium hydroxide nanosheets can increase the mechanical interlocking centers between carbon fibers and the matrix, forming a strong mechanical interlocking effect between the carbon fibers and the matrix, reducing stress concentration of carbon fibers in the resin matrix, and enhancing interfacial bonding, thereby improving mechanical properties.

[0031] Finally, the modifier X used in this invention contains a triazine ring structure and has good flame retardant properties. It achieves the best flame retardant effect by combining with the inorganic flame retardant magnesium hydroxide. The modified carbon fiber composite material obtained by this invention has a limiting oxygen index as high as 40.8%.

[0032] The above embodiments are merely illustrative examples and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A method for preparing a modified carbon fiber composite material, comprising the following steps: Step S1: Cut the carbon fiber into short carbon fibers, wash with organic solvent, and vacuum dry to obtain untreated short carbon fibers (CFs). Untreated short carbon fibers (CFs) were immersed in nitric acid solution for reaction. After the reaction, the carbon fibers were repeatedly washed with deionized water until the pH value was neutral. The carbon fibers were then dried under vacuum to obtain acidified short carbon fibers (CFs-COOH). Step S2: Add modifier X Add the organic solvent and water to a mixed solvent, then add the condensing agent HATU and stir until homogeneous to obtain a mixture; immerse the acidified short carbon fiber CFs-COOH in the above mixture; after immersion, repeatedly wash the carbon fiber with deionized water and vacuum dry to obtain the modified short carbon fiber CFs-X; Step S3: Add 20-30 parts of modified short carbon fiber CFs-X, 3-10 parts of magnesium hydroxide nanosheets, and 100-150 parts of diluent to a mixer and stir to obtain premix A; then add 90-120 parts of epoxy resin, 5-15 parts of curing agent, and 1-3 parts of antioxidant to premix A in sequence, and continue stirring to obtain premix B; Step S4: Place the premixed material B in a mold and put it in an oven for hot pressing and curing. After the mold cools down, remove the mold to obtain the modified carbon fiber composite material. The organic solvent in step S1 is acetone; the organic solvent in step S2 is acetone; In step S3, the curing agent is hexamethylenediamine; the epoxy resin is E-51. In step S3, the antioxidant is antioxidant 1076; the diluent is acetone. In step S2, the mass ratio of the modifier X to the acidified short carbon fiber CFs-COOH is 1:(2~5).

2. The preparation method according to claim 1, characterized in that, In step S1, the concentration of the nitric acid solution is 25-40 wt%; the length of the short carbon fiber is 1-10 mm; the mass-to-volume ratio of the untreated short carbon fiber (CFs) to the nitric acid solution is 1 g:(10-20) mL; the reaction temperature is 50-100 °C; and the reaction time is 1-10 h.

3. The preparation method according to claim 1, characterized in that, In step S2, the mass-volume ratio of the modifier X to the mixed solvent is 1 g:(40~60) mL; the mass ratio of the modifier X to the condensing agent HATU is 1:(0.05~0.15); the soaking temperature is 50~80℃ and the soaking time is 1~5 h.

4. The preparation method according to claim 1, characterized in that, In step S3, the mixing temperature is 50~100℃.

5. The preparation method according to claim 1, characterized in that, In step S4, the curing conditions are: curing at 80~100℃ for 1 hour, curing at 100~120℃ for 2 hours, and curing at 130~150℃ for 2 hours.

6. A modified carbon fiber composite material, characterized in that, It is prepared by the method described in any one of claims 1-5.

7. The application of the modified carbon fiber composite material of claim 6 in the preparation of a one-piece molded carbon fiber suitcase.

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