Modified carbon fiber composite material as well as preparation method and application thereof

Abstract

The invention 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 the modifier X and the magnesium hydroxide nanosheet, the mechanical property and flame retardant property of the modified carbon fiber composite material are greatly improved, and the modified carbon fiber composite material can be used for preparing an integrated compression molding carbon fiber luggage case.

Description

Technical Field

[0001] The present invention 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. Background Art

[0002] Carbon fiber is a fibrous carbon material with a micrographite crystal structure and is a slender filament. Carbon fiber has 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. Depending on the different precursors used in carbon fiber, it 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 requires integration with other matrix materials to effectively unleash its excellent properties. Typically, carbon fiber-reinforced composites are prepared using specialized processes, using carbon fiber as reinforcement and metal, ceramic, cement, carbon, resin, and other materials as matrices. Since cured epoxy resin is an amorphous, highly cross-linked polymer, it exhibits minimal shrinkage during curing, low residual stress, and requires low processing pressure. It is currently the most common resin matrix. The resulting carbon fiber-reinforced epoxy resin composites exhibit anisotropy, designability, material-structure integration, composite effects, and versatility, leading to widespread application in luggage, aerospace, automotive, energy, sports, and medicine. For example, the male-female snap-fit ​​mechanism used in this one-piece compression-molded carbon fiber luggage offers several advantages: 1) Convenience: The male-female snap-fit ​​mechanism is simple to operate, eliminating the need for complex opening procedures. Users simply align the male and female snaps to quickly open and close the suitcase, significantly saving time and effort, making it easy to use even on the go. 2) Significant Lightweight: The design of the one-piece molded carbon fiber suitcase minimizes weight while ensuring overall durability. 3) Stylish and Trendy: The simple and streamlined male and female buckle design complements the stylish appearance of the one-piece molded carbon fiber suitcase, meeting current consumer demands for luggage that is both practical and aesthetically pleasing, enhancing the product's overall quality and style. 4) Stable and Reliable Structure: The tight male and female buckle design effectively prevents accidental opening during use, ensuring luggage safety and providing a stable and reliable closure.

[0004] Carbon fiber-reinforced resin-based composites are composed of carbon fibers, a resin matrix, and an interfacial phase between the two phases. The carbon fibers serve as reinforcement within the composite, while the resin matrix molds the composite into a load-bearing structure. The interfacial phase acts as a bridge connecting the fibers and the resin matrix, and also as a link for stress transfer. However, the low surface energy and chemical inactivity of raw carbon fibers result in poor interfacial bonding between them and 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 topic for researchers. Summary of the Invention

[0005] The present invention aims to provide a modified carbon fiber composite material, its preparation method, and its application, to address the problems existing in the prior art, such as low carbon fiber surface energy, chemical inactivity, poor interfacial bonding with the matrix, and poor flame retardancy. To address the above technical problems, the present invention provides the following technical solutions: A method for preparing a modified carbon fiber composite material comprises the following steps: Step S1: cutting carbon fibers into short carbon fibers, washing them with an organic solvent, and vacuum drying them to obtain untreated short carbon fibers CFs; immersing the untreated short carbon fibers CFs in a nitric acid solution for reaction, repeatedly washing the carbon fibers with deionized water until the pH value is neutral after the reaction, and vacuum drying them to obtain acidified short carbon fibers CFs-COOH; Step S2: Add the modifier X Add to a mixed solvent of an organic solvent and water, then add a condensation agent HATU, and stir evenly to obtain a mixed solution; soak the acidified short carbon fiber CFs-COOH in the mixed solution; after soaking, repeatedly wash the carbon fiber with deionized water and vacuum dry to obtain the modified short carbon fiber CFs-X; Step S3: adding 20-30 parts of modified short carbon fibers CFs-X, 3-10 parts of magnesium hydroxide nanosheets, and 100-150 parts of a diluent into a mixer, stirring and mixing to obtain a premix A; then adding 90-120 parts of an epoxy resin, 5-15 parts of a curing agent, and 1-3 parts of an antioxidant to the premix A in sequence, and continuing to stir and mix to obtain a premix B; Step S4: placing the premixed material B in a mold and placing it in an oven for hot pressing and curing, and demolding the mold after cooling to obtain a 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 25~40wt%; the length of the short carbon fibers is 1~10mm; the mass volume ratio of the untreated short carbon fibers CFs to the nitric acid solution is 1g:(10~20)mL; the reaction temperature is 50~100°C, and the reaction time is 1~10h.

[0008] In some embodiments, 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 acidified short carbon fiber CFs-COOH is 1: (2-5); the mass ratio of the modifier X to the condensation agent HATU is 1: (0.05-0.15); the immersion temperature is 50-80° C., and the immersion 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 embodiments, in step S3, the stirring treatment temperature is 50-100°C.

[0012] In some embodiments, in step S4, the curing conditions are: curing at 80-100° C. for 1 hour, curing at 100-120° C. for 2 hours, and curing at 130-150° C. 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 use of the modified carbon fiber composite material in preparing an integrally molded carbon fiber suitcase.

[0015] The present invention has achieved the following beneficial effects: 1) The present invention introduces a modifier X and magnesium hydroxide nanosheets, greatly improving the mechanical properties and flame retardant properties of modified carbon fiber composites.

[0016] 2) The application introduces modifier X into the surface of carbon fiber under the action of HATU promoter by chemical grafting method, the introduced modifier X can increase the surface active functional group of carbon fiber, promote the wettability between fiber and resin matrix, and the amino group introduced on the surface of carbon fiber can occur curing crosslinking reaction with epoxy resin, which greatly improves the compatibility of fiber and resin matrix, so as to improve the mechanical properties. In addition, the magnesium hydroxide nanosheet can increase the mechanical engagement center between carbon fiber and matrix, form strong mechanical interlocking effect between carbon fiber and matrix, weaken the stress concentration of carbon fiber in resin matrix, and enhance the interface bonding force, so as to improve the mechanical properties.

[0017] 3) The modifier X used in the application contains triazine ring structure, has good flame retardant performance, and can play the best flame retardant effect by combining with inorganic flame retardant magnesium hydroxide. The limiting oxygen index of the modified carbon fiber composite material obtained by the application is as high as 40.8%. DETAILED DESCRIPTION

[0018] The technical solutions of the application will be described below in conjunction with the embodiments, obviously, the described embodiments are part of the embodiments of the application, rather than all the embodiments. Based on the embodiments in the application, all other embodiments obtained by those skilled in the art without creative labor belong to the protection scope of the application.

[0019] The end points and any values of the scope described in the application are not limited to the exact ranges or values, and these ranges or values should be understood as containing values close to these ranges or values. For numerical value ranges, the end point values of each range, the end point values of each range and the individual point values can be combined with each other to obtain one or more new numerical value ranges, which should be regarded as specifically disclosed herein. The raw materials and reagents used in the following examples are commercially available.

[0020] Example 1 A preparation method of a modified carbon fiber composite material, comprising the following steps: Step S1: cut the carbon fiber (T300, produced by Japan Toray Co., Ltd., with a hole number of 3 K, and a diameter and density of 7 μm and 1.75 g / cm 3 ) into short carbon fibers with a length of about 3 mm, and then place it in a round-bottom flask, clean it with acetone reflux at 80℃ for 24 h; then dry it in a vacuum oven at 80℃ overnight, and prepare for use, to obtain untreated short carbon fibers CFs; then immerse the untreated short carbon fibers CFs (20.0 g) in a concentrated nitric acid solution (200 mL) with a concentration of 30wt%, react at 80℃ for 5 h, then repeatedly clean the carbon fiber with deionized water until the pH value is neutral, and vacuum dry overnight, prepare for use, to obtain acidized short carbon fibers CFs-COOH; Step S2: Add the modifier X (5.0 g) was added to a mixed solvent of THF (200 mL) and water (50 mL), and then a condensation agent HATU (0.3 g) was added and stirred to obtain a mixed solution. Acidified short carbon fiber CFs-COOH (20.0 g) was placed in the above mixed solution and soaked for 2 h at 60 ° C. After the reaction, 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: 20 parts of modified short carbon fibers CFs-X, 5 parts of magnesium hydroxide nanosheets (model LY1-S, average particle size 0.9 μm, average thickness 0.2 μm, produced by Kyowa, Japan), and 100 parts of acetone were added to a mixer and stirred at 50° C. for 30 minutes to obtain a premix A; then, 100 parts of epoxy resin (model WSR618, molecular weight between 350 and 400, produced by Nantong Xingchen Co., Ltd.), 10 parts of curing agent ethylenediamine, and 1 part of antioxidant 1010 were added to the premix A in sequence, and the stirring and mixing were continued at 50° C. for 30 minutes to obtain a premix B; Step S4: Place the mixed material B in a mold and put it into an oven for hot pressing and curing. The curing conditions are 80°C for 1 hour, 120°C for 2 hours, and 150°C for 2 hours. After the mold is cooled, it is demolded to obtain a modified carbon fiber composite material.

[0021] Example 2 A method for preparing a modified carbon fiber composite material comprises the following steps: Step S1: Carbon fiber (T300, produced by Toray Industries, Japan, with a pore size of 3 K, a diameter of 7 μm and a density of 1.75 g / cm 3 ) were cut into short carbon fibers with a length of about 3 mm, then placed in a round-bottom flask and washed with acetone reflux at 80 ° C for 24 h; then placed in a vacuum oven at 80 ° C and dried overnight for later use to obtain untreated short carbon fibers CFs; then the untreated short carbon fibers CFs (20.0 g) were immersed in a nitric acid solution (300 mL) with a concentration of 40 wt%, reacted at 70 ° C for 6 h, and then the carbon fibers were repeatedly washed with deionized water until the pH value was neutral, vacuum dried overnight for later use to obtain acidified short carbon fibers CFs-COOH; Step S2: Add the modifier X (8.0 g) was added to a mixed solvent of acetone (200 mL) and water (50 mL), and then the condensation agent HATU (0.5 g) was added and stirred to obtain a mixed solution. Acidified short carbon fiber CFs-COOH (20.0 g) was placed in the above mixed solution and soaked for 3 h at 55 ° C. After the reaction, 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: 25 parts of modified short carbon fibers CFs-X, 6 parts of magnesium hydroxide nanosheets (model LY1-S, average particle size 0.9 μm, average thickness 0.2 μm, produced by Kyowa, Japan), and 100 parts of acetone were added to a mixer and stirred at 50° C. for 30 minutes to obtain a premix A; then, 100 parts of epoxy resin (model WSR618, molecular weight between 350 and 400, produced by Nantong Xingchen Co., Ltd.), 8 parts of curing agent hexamethylenediamine, and 2 parts of antioxidant 1076 were added to the premix A in sequence, and the stirring and mixing were continued at 50° C. for 30 minutes to obtain a premix B; Step S4: placing the premixed material B in a mold and putting it into an oven for hot pressing and curing. The curing conditions are 80°C for 1 hour, 120°C for 2 hours, and 150°C for 2 hours. After the mold is cooled, demolding is performed to obtain a modified carbon fiber composite material.

[0022] Comparative Example 1 On the basis of Example 2, steps S1 and S2 are omitted, and the modified short carbon fiber CFs-X in step S3 is replaced by 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 On the basis of 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 On the basis of Example 2, the Replace with , other operations and steps are the same as in Example 2.

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

[0026] 2) Flexural Strength: The flexural strength and flexural modulus of carbon fiber composites were measured using the three-point bending method on a German Zwick universal testing machine in accordance with ASTM D7624. The sensor was 1 kN, the specimen dimensions were 50 mm × 10 mm × 2 mm, the test speed was 1 mm / min, the span was 64 mm, and the tests were conducted at room temperature. Five valid data points were selected from each group of specimens and the average value was taken.

[0027] 3) Limiting Oxygen Index: Tested according to GB / T 2406.2-2009, "Plastics - Determination of Combustion Behavior by the Oxygen Index Method - Part 2: Room Temperature Test." Results are shown in Table 1.

[0028] Table 1 Performance test results According to the results of Examples 1-2 in Table 1, it can be seen that 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 the modifier X and magnesium hydroxide nanosheets, greatly improving the mechanical properties and flame retardant properties of modified carbon fiber composites. The main reasons are: First, the present invention utilizes a chemical grafting method to introduce modifier X onto the carbon fiber surface under the action of a HATU accelerator. The introduced modifier X can increase the surface active functional groups of the carbon fiber, 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, greatly improving the compatibility between the fiber and the resin matrix, thereby enhancing the mechanical properties.

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

[0031] Finally, the modifier X adopted by the application contains triazine ring structure, has good flame retardant performance, and through combination with inorganic flame retardant magnesium hydroxide, optimal flame retardation effect is achieved, and the limiting oxygen index of the modified carbon fiber composite material obtained by the application is as high as 40.8%.

[0032] The above examples are merely illustrative for the sake of clarity and are in no way intended to limit the scope of the embodiments. Other variations and modifications can be made based on the above description by those of ordinary skill in the art. Here, all the embodiments are not required to be exhaustive. The obvious variations or modifications derived from the above description are still within the protection scope of the present application.

Claims

1. A method for preparing a modified carbon fiber composite material, comprising the following steps: Step S1: cutting the carbon fibers into short carbon fibers, washing them with an organic solvent, and vacuum drying them to obtain untreated short carbon fibers CFs; The untreated short carbon fibers CFs were immersed in a nitric acid solution for reaction. After the reaction, the carbon fibers were repeatedly washed with deionized water until the pH value was neutral, and then vacuum dried to obtain acidified short carbon fibers CFs-COOH. Step S2: Add the modifier X Add to a mixed solvent of an organic solvent and water, then add a condensation agent HATU, and stir evenly to obtain a mixed solution; soak the acidified short carbon fiber CFs-COOH in the mixed solution; after soaking, repeatedly wash the carbon fiber with deionized water and vacuum dry to obtain the modified short carbon fiber CFs-X; Step S3: adding 20-30 parts of modified short carbon fibers CFs-X, 3-10 parts of magnesium hydroxide nanosheets, and 100-150 parts of a diluent into a mixer, stirring and mixing to obtain a premix A; then adding 90-120 parts of an epoxy resin, 5-15 parts of a curing agent, and 1-3 parts of an antioxidant to the premix A in sequence, and continuing to stir and mix to obtain a premix B; Step S4: placing the premixed material B in a mold and placing it in an oven for hot pressing and curing, and demolding the mold after cooling to obtain a modified carbon fiber composite material.

2. The preparation method according to claim 1, characterized in that 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.

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

4. 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 acidified short carbon fiber CFs-COOH is 1: (2-5); the mass ratio of the modifier X to the condensation agent HATU is 1: (0.05-0.15); the immersion temperature is 50-80 ° C, and the immersion time is 1-5 h.

5. The preparation method according to claim 1, characterized in that 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.

6. The preparation method according to claim 1, characterized in that 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.

7. The preparation method according to claim 1, characterized in that In step S3, the stirring and mixing treatment temperature is 50-100°C.

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

9. A modified carbon fiber composite material, characterized in that: The method according to any one of claims 1 to 8 is used for preparation.

10. Use of the modified carbon fiber composite material according to claim 9 in preparing an integrally molded carbon fiber suitcase.

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