Carbon fiber sizing agent, modified carbon fiber, composite material and method

Abstract

The embodiment of the invention provides a carbon fiber sizing agent, a modified carbon fiber, a composite material and a method, and relates to the technical field of carbon fiber surface treatment. The carbon fiber sizing agent comprises the following components: polyetherimide, amino-functionalized ZIF-8 and an organic solvent, wherein the mass of the amino-functionalized ZIF-8 is 1%-10% of the mass of the polyetherimide. According to the carbon fiber sizing agent, the modified carbon fiber, the composite material and the method provided by the embodiment of the invention, the interface bonding strength and the heat resistance of the carbon fiber and the resin matrix in the carbon fiber composite material can be improved.

Description

Technical Field

[0001] This application relates to the field of carbon fiber surface treatment technology, and more specifically, to a carbon fiber sizing agent, modified carbon fiber, composite material, and method. Background Technology

[0002] Carbon fiber composites are materials composed of carbon fibers and a resin matrix. Their properties mainly depend on the interfacial bonding strength between the carbon fibers and the resin matrix. Sizing agents are typically used during carbon fiber production to improve this interfacial bonding strength. Sizing is a low-cost, simple, and industrially scalable surface modification method that can protect the fiber surface, improve fiber bundle structure, and increase fiber wettability to the resin, making it a crucial step in carbon fiber production. While traditional sizing agents (such as epoxy resin and polyurethane-based sizing agents) can improve the processability of carbon fibers, the resulting carbon fiber composites still suffer from problems such as low interfacial bonding strength and insufficient heat resistance. Summary of the Invention

[0003] The purpose of this application is to provide a carbon fiber sizing agent, modified carbon fiber, composite material and method, which can improve the interfacial bonding strength and heat resistance between carbon fiber and resin matrix in carbon fiber composite material.

[0004] In a first aspect, embodiments of this application provide a carbon fiber sizing agent comprising the following components: polyetherimide, amino-functionalized ZIF-8, and an organic solvent, wherein the mass of the amino-functionalized ZIF-8 is 1% to 10% of the mass of the polyetherimide.

[0005] In the above technical solution, the carbon fiber sizing agent contains amino-functionalized ZIF-8 and polyetherimide (PEI). The carbon fiber is sized using this carbon fiber sizing agent. The amino-functionalized ZIF-8 in the carbon fiber sizing agent can introduce amino groups, giving the carbon fiber surface more active groups. On the other hand, it can enhance the compatibility between ZIF-8 and polyetherimide. By utilizing the metal-organic framework of ZIF-8 material and the synergistic modification of carbon fiber by polyetherimide (PEI), the interfacial bonding performance between carbon fiber and resin matrix can be improved, the mechanical properties of composite materials can be enhanced, and the bonding force between polyetherimide and carbon fiber can be enhanced. Polyetherimide (PEI) can enhance heat resistance and provide strong polar groups, thereby improving the surface modification effect of polyetherimide (PEI) on carbon fiber. Specifically, the amino-functionalization of ZIF-8 has a positive enhancing effect on the overall performance: amino-functionalized ZIF-8 increases the number of active groups on the carbon fiber surface, and the imide carbonyl group (-C=O) of polyetherimide (PEI) can act as a hydrogen bond acceptor, forming -C=O…HN- hydrogen bonds with -NH2; the active amino groups at the ends of amino-functionalized ZIF-8 and polyetherimide (PEI) can work together to improve the surface activity of carbon fibers. The strongly polar groups of polyetherimide (PEI) (such as -C=O, -O-) generate dipole-dipole interactions with the polar groups on the CF surface, enhancing interfacial bonding; the nano-rough structure of ZIF-8 enhances the roughness of the carbon fiber, with chemical bonding and mechanical wedge bonding working together on the carbon fiber. Therefore, the synergistic effect of amino-functionalized ZIF-8 and polyetherimide improves the modification effect on carbon fibers.

[0006] In one possible implementation, the amino-functionalized ZIF-8 comprises a material obtained by amino-modifying ZIF-8 using a silane coupling agent; And / or, the mass concentration of the solution composed of the polyetherimide and the organic solvent is 0.001 g / mL to 0.1 g / mL; And / or, the organic solvent includes at least one of N-methylpyrrolidone and dimethylformamide.

[0007] Secondly, embodiments of this application provide a method for preparing the carbon fiber sizing agent provided in the first aspect, which includes the following steps: Polyetherimide is dissolved in an organic solvent to form a solution, and then amino-functionalized ZIF-8 is uniformly dispersed in the solution.

[0008] In one possible implementation, the preparation method of the amino-functionalized ZIF-8 includes the following steps: dispersing ZIF-8 in a solvent, adding a silane coupling agent, reacting at 70~80℃ for 5~8 hours, and obtaining the amino-functionalized ZIF-8 by centrifugation and drying, wherein the silane coupling agent includes 3-aminopropyltriethoxysilane, and the mass ratio of ZIF-8 to the silane coupling agent is 1:(0.5~2).

[0009] In the above technical solution, the preparation method of amino-functionalized ZIF-8 is to modify ZIF-8 with amino groups using a silane coupling agent, which is a simple preparation method.

[0010] In one possible implementation, the method of uniformly dispersing amino-functionalized ZIF-8 in the solution includes: adding amino-functionalized ZIF-8 to the solution and ultrasonically dispersing it for 30 to 60 minutes, wherein the ultrasonic dispersion power is 200 to 500 W.

[0011] Thirdly, embodiments of this application provide a method for surface modification of carbon fiber, which includes the following steps: The carbon fiber is impregnated with the carbon fiber sizing agent provided in the first aspect for sizing treatment, and then dried to obtain modified carbon fiber.

[0012] In the above technical solution, the sizing treatment of carbon fiber is mainly carried out by impregnation and drying processes, so that the carbon fiber sizing agent is coated on the surface of the carbon fiber, and a strong interfacial bonding layer is formed by the components in the carbon fiber sizing agent.

[0013] In one possible implementation, the carbon fibers are first subjected to plasma treatment, followed by sizing.

[0014] In the above technical solution, the carbon fiber is first subjected to plasma treatment to activate the surface of the carbon fiber, thereby forming a micron-level rough structure and hydroxylating the surface. Then, the carbon fiber is sized using the carbon fiber sizing agent of this application embodiment. The flexible polymer in the carbon fiber sizing agent, polyetherimide (PEI), and ZIF-8 with a nanostructure form a dual-system composite structure, which can further increase the surface active groups and surface roughness of the carbon fiber, thereby improving the interfacial properties of the composite material formed by the carbon fiber.

[0015] In one possible implementation, the gas used for plasma treatment is argon or oxygen, and the pressure is 10~100 Pa. And / or, the plasma treatment power is 50~200 W, and the time is 1~10 minutes.

[0016] In the above technical solution, high-energy ions in the plasma bombard the carbon fiber surface under the acceleration of the electric field, removing surface contaminants and forming micro-nano-level roughness through sputtering effect; high-energy electrons and metastable atoms promote hydroxylation of carbon fiber surface through charge transfer effect.

[0017] Fourthly, embodiments of this application provide a modified carbon fiber, which is prepared using the surface modification method for carbon fiber provided in the third aspect.

[0018] Fifthly, embodiments of this application provide a composite material, including a resin matrix and the modified carbon fiber provided in the fourth aspect. Detailed Implementation

[0019] Polyetherimide (PEI) is used as a component of high-performance sizing agents for sizing carbon fibers due to its high heat resistance and the presence of highly polar groups. However, the bonding ability between polyetherimide (PEI) and carbon fibers is limited, thus limiting its surface modification effect on carbon fibers.

[0020] In addition, ZIF-8 is a metal-organic framework material whose structure consists of metal ions and organic ligands. The applicant found that ZIF-8, as a nanoporous material, is used as a component of a sizing agent to sizing carbon fibers; ZIF-8 can introduce active groups through surface functionalization and can also increase the roughness of carbon fibers, but its surface modification effect on carbon fibers is relatively weak.

[0021] After extensive exploration and research, the applicant discovered that by functionalizing ZIF-8 and combining the nanostructure enhancement of ZIF-8 material with the chemical bonding of polyetherimide (PEI), the surface modification effect of carbon fiber can be significantly improved, thereby achieving a significant improvement in the interfacial properties and heat resistance of carbon fiber.

[0022] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions in the embodiments of this application will be clearly and completely described below. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments whose manufacturers are not specified are all conventional products that can be purchased commercially.

[0023] The carbon fiber sizing agent, modified carbon fiber, composite material, and method of this application will be described in detail below.

[0024] This application provides a carbon fiber sizing agent comprising the following components: polyetherimide, amino-functionalized ZIF-8, and an organic solvent, wherein the mass of amino-functionalized ZIF-8 is 1% to 10% of the mass of polyetherimide. Exemplarily, the mass of amino-functionalized ZIF-8 is 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10% of the mass of polyetherimide, or any intermediate value between two of the above values.

[0025] In the embodiments of this application, ZIF-8 is a metal-organic framework material whose structure consists of metal ions and organic ligands. In some embodiments of this application, ZIF-8 is provided by zinc ions (such as zinc nitrate Zn(NO3)2·6H2O). 2+ ZIF-8 is a three-dimensional porous network structure formed by the coordination of imidazole ions (such as imidazole ions provided by 2-methylimidazolium) with imidazole ions. The ZIF-8 in this application can be self-made or purchased directly; for example, ZIF-8 can be purchased from a related product of Shanghai Yuanye Biotechnology Co., Ltd. ZIF-8 possesses the following excellent physicochemical properties: extremely high specific surface area and pore volume: the specific surface area of ​​ZIF-8 is typically as high as 1000-2000 m² / s. 2 / g, meaning it has a large internal space for adsorbing and storing molecules. Thermal stability: Stable up to 550℃ in an inert atmosphere. Chemical stability: Very stable in common organic solvents (such as benzene and methanol). Particularly noteworthy is its structural stability in boiling water and alkaline aqueous solutions, which is rare for many MOF materials. "Gate effect": The pore diameter is approximately 3.4 Å, but the flexible framework allows the pores to dynamically expand during molecular adsorption (up to 4.0 Å or more). This allows it to selectively adsorb molecules slightly larger than its theoretical pore size (e.g., CO2 with a kinetic diameter of 3.3 Å), while excluding larger molecules (e.g., N2 with a kinetic diameter of 3.6 Å). This "molecular sieve" property is the basis for its use in separation.

[0026] Amino-functionalized ZIF-8 is a material obtained by amino-modifying ZIF-8. In some embodiments of this application, amino-functionalized ZIF-8 is obtained by amino-modifying ZIF-8 using a silane coupling agent. Similarly, amino-functionalized ZIF-8 can be prepared in-house or purchased directly. Amino-functionalized ZIF-8 not only retains the aforementioned characteristics of ZIF-8, but also achieves synergistic effects by introducing amino groups.

[0027] In the embodiments of this application, polyetherimide (PEI) possesses the following performance characteristics: Extremely high heat resistance: High glass transition temperature (Tg): PEI has a glass transition temperature as high as approximately 217°C. This means that it maintains excellent mechanical strength and stiffness at high temperatures (e.g., 180-200°C), and its long-term service temperature can reach above 170°C. Excellent heat aging resistance: Its performance degradation is very slow even after prolonged use in high-temperature environments. Superior mechanical strength and rigidity: Even at high temperatures, PEI exhibits high strength, modulus, and dimensional stability. Its strength and rigidity are comparable to some metals, but its weight is much lighter, making it ideal for applications requiring lightweight and high strength.

[0028] In this embodiment, the carbon fiber sizing agent comprises amino-functionalized ZIF-8 and polyetherimide (PEI). This sizing agent is used to sizing carbon fibers. The amino-functionalized ZIF-8 in the sizing agent introduces amino groups, increasing the number of active groups on the carbon fiber surface. Furthermore, it enhances the compatibility between ZIF-8 and polyetherimide. The synergistic modification of carbon fibers by the metal-organic framework of ZIF-8 and polyetherimide (PEI) improves the interfacial bonding performance between carbon fibers and the resin matrix, enhancing the mechanical properties of the composite material. It also strengthens the bond between polyetherimide and carbon fibers. Polyetherimide (PEI) enhances heat resistance and provides strongly polar groups, improving the surface modification effect of polyetherimide (PEI) on carbon fibers. Therefore, the carbon fiber sizing agent can improve the interfacial bonding strength and heat resistance of carbon fibers and the resin matrix in carbon fiber composites.

[0029] In some embodiments of this application, the mass concentration of the solution composed of polyetherimide and organic solvent is 0.001 g / mL to 0.1 g / mL.

[0030] In the embodiments of this application, the mass concentration of the solution composed of polyetherimide and organic solvent refers to the ratio of the mass of polyetherimide to the volume of the solution composed of polyetherimide and organic solvent. Exemplarily, the mass concentration of the solution composed of polyetherimide and organic solvent is 0.001 g / mL, 0.002 g / mL, 0.005 g / mL, 0.007 g / mL, 0.009 g / mL, 0.01 g / mL, 0.02 g / mL, 0.03 g / mL, 0.07 g / mL, 0.1 g / mL, or any intermediate value between two of the above values.

[0031] In some embodiments of this application, the organic solvent includes at least one of N-methylpyrrolidone and dimethylformamide (DMF).

[0032] This application also provides a method for preparing the carbon fiber sizing agent of the foregoing embodiments, which includes the following steps: Polyetherimide is dissolved in an organic solvent to form a solution, and then amino-functionalized ZIF-8 is uniformly dispersed in the solution to form a stable nanocomposite system.

[0033] In some embodiments of this application, the preparation method of amino-functionalized ZIF-8 involves modifying ZIF-8 with an amino group using a silane coupling agent. As one embodiment, the preparation method of amino-functionalized ZIF-8 includes the following steps: dispersing ZIF-8 in a solvent, adding a silane coupling agent, reacting at 70-80°C for 5-8 hours, and then centrifuging and drying to obtain amino-functionalized ZIF-8. The silane coupling agent includes 3-aminopropyltriethoxysilane, and the mass ratio of ZIF-8 to the silane coupling agent is 1:(0.5-2). The solvent includes methanol. Exemplarily, the reaction conditions are 70°C, 72°C, 75°C, 77°C, 80°C, or any intermediate value between the above two values, for 5 hours, 6 hours, 7 hours, 8 hours, or any intermediate value between the above two values.

[0034] In some embodiments of this application, the method for uniformly dispersing amino-functionalized ZIF-8 in a solution includes: adding amino-functionalized ZIF-8 to the solution and ultrasonically dispersing it for 30-60 minutes at a power of 200-500 W. Exemplarily, the ultrasonic dispersing power is 200 W, 300 W, 400 W, 500 W, or any value between two of the above; the ultrasonic dispersing time is 30 minutes, 40 minutes, 50 minutes, 60 minutes, or any value between two of the above.

[0035] This application also provides an application of the carbon fiber sizing agent described in the foregoing embodiments in carbon fiber surface modification.

[0036] This application also provides a method for surface modification of carbon fiber, which includes the following steps: The carbon fiber was impregnated with the carbon fiber sizing agent of the aforementioned embodiment for sizing treatment, and then dried to obtain modified carbon fiber.

[0037] In this embodiment, the sizing treatment of carbon fiber is mainly carried out by impregnation and drying processes, so that the carbon fiber sizing agent is coated on the surface of the carbon fiber, and a strong interfacial bonding layer is formed by the components in the carbon fiber sizing agent.

[0038] In some embodiments of this application, the carbon fiber is first subjected to plasma treatment and then to sizing. Specifically, the carbon fiber after high-temperature carbonization is subjected to plasma treatment.

[0039] In this embodiment, the carbon fiber is first subjected to plasma treatment to activate the carbon fiber surface, thereby forming a micron-level rough structure and hydroxylating the surface. Then, the carbon fiber is sized using the carbon fiber sizing agent of this application embodiment. The flexible polymer polyetherimide (PEI) in the carbon fiber sizing agent and the nanostructured ZIF-8 construct a dual-system composite structure, which can further increase the surface active groups and surface roughness of the carbon fiber, thereby improving the interfacial properties of the composite material formed by the carbon fiber.

[0040] In some embodiments of this application, the gas used for plasma treatment is argon or oxygen, and the gas pressure is 10~100 Pa. Exemplarily, the gas pressure is 10 Pa, 30 Pa, 50 Pa, 70 Pa, 100 Pa, or any intermediate value between two of the above values.

[0041] In some embodiments of this application, the plasma treatment power is 50~200 W, and the time is 1~10 minutes. Exemplarily, the plasma treatment power is 50 W, 100 W, 150 W, 200 W or any intermediate value between two of the above values, and the time is 1 minute, 3 minutes, 5 minutes, 8 minutes, 10 minutes or any intermediate value between two of the above values.

[0042] In this embodiment, plasma treatment is a technique that uses plasma generated by ionized gas to physically or chemically modify the surface of a material. By bombarding the carbon fiber surface with plasma, oxygen-containing functional groups are introduced, thereby improving surface activity. The equipment can include radio frequency plasma, microwave plasma torches, and sliding arc jet plasma devices, etc.

[0043] In this embodiment, high-energy ions in the plasma bombard the carbon fiber surface under the acceleration of an electric field, removing surface contaminants and forming micro-nano-level roughness through sputtering effect; high-energy electrons and metastable atoms promote hydroxylation of the carbon fiber surface through charge transfer effect.

[0044] This application also provides a modified carbon fiber, which is prepared using the surface modification method for carbon fibers described in the foregoing embodiments.

[0045] This application also provides a composite material, including a resin matrix and the modified carbon fiber described in the foregoing embodiments.

[0046] The features and performance of this application will be further described in detail below with reference to the embodiments.

[0047] Example 1 This embodiment provides a modified carbon fiber, the surface modification method of which is as follows: (1) 500 mg ZIF-8 (purchased from Shanghai Yuanye Biotechnology Co., Ltd.) was dispersed in 50 mL of methanol, and 0.75 mL of 3-aminopropyltriethoxysilane was added. The mass ratio of ZIF-8 to 3-aminopropyltriethoxysilane was 1:1.4. The reaction was carried out at 80 °C for 6 hours. After centrifugation and drying, amino-functionalized ZIF-8 was obtained. 1 g of polyetherimide (PEI) was dissolved in 100 mL of N-methylpyrrolidone, and 0.05 g of the above-mentioned amino-functionalized ZIF-8 was added. The amount of amino-functionalized ZIF-8 added was 5% of the mass of polyetherimide (PEI). The mixture was ultrasonically dispersed for 40 minutes at a power of 300 W to obtain a carbon fiber sizing agent.

[0048] (2) The carbon fiber after high temperature carbonization (the carbon fiber (T800 grade) comes from Zhongfu Shenying Carbon Fiber Co., Ltd.) is placed in a plasma reactor, argon gas is introduced, the gas pressure is 50 Pa, and it is treated for 5 minutes under the condition of 150 W power. The plasma-treated carbon fibers were impregnated in the above-mentioned carbon fiber sizing agent for 10 minutes and then dried at 80°C to obtain modified carbon fibers.

[0049] Example 2 This embodiment provides a modified carbon fiber, the surface modification method of which differs from that of Example 1 in that: in step (1) of this embodiment, 0.07 g of the above-mentioned amino-functionalized ZIF-8 is added, and the amount of amino-functionalized ZIF-8 added is 7% of the mass of polyetherimide (PEI).

[0050] Example 3 This embodiment provides a modified carbon fiber, the surface modification method of which differs from that of Example 1 in that: in step (1) of this embodiment, 0.01 g of the above-mentioned amino-functionalized ZIF-8 is added, and the amount of amino-functionalized ZIF-8 added is 1% of the mass of polyetherimide (PEI).

[0051] Example 4 This embodiment provides a modified carbon fiber, the surface modification method of which differs from that of Example 1 in that: in step (1) of this embodiment, 0.1 g of the above-mentioned amino-functionalized ZIF-8 is added, and the amount of amino-functionalized ZIF-8 added is 10% of the mass of polyetherimide (PEI).

[0052] Example 5 This embodiment provides a modified carbon fiber, the surface modification method of which differs from that of Example 1 in that: in step (1) of this embodiment, the amount of 3-aminopropyltriethoxysilane added is adjusted so that the mass ratio of ZIF-8 to 3-aminopropyltriethoxysilane is 1:0.5.

[0053] Example 6 This embodiment provides a modified carbon fiber, the surface modification method of which differs from that of Example 1 in that: in step (1) of this embodiment, the amount of 3-aminopropyltriethoxysilane added is adjusted so that the mass ratio of ZIF-8 to 3-aminopropyltriethoxysilane is 1:2.

[0054] Example 7 This embodiment provides a modified carbon fiber, the surface modification method of which differs from that of Embodiment 1 in that: in step (2) of this embodiment, the plasma treatment power is 200 W and the treatment time is 8 minutes.

[0055] Example 8 This embodiment provides a modified carbon fiber, the surface modification method of which differs from that of Embodiment 1 in that: in step (2) of this embodiment, the plasma treatment power is 50 W and the treatment time is 10 minutes.

[0056] Example 9 This embodiment provides a modified carbon fiber, the surface modification method of which differs from that of Embodiment 1 in that: in step (2) of this embodiment, plasma treatment is not performed.

[0057] Comparative Example 1 This comparative example provides a modified carbon fiber, the surface modification method of which differs from that of Example 1 in that: in step (1) of this comparative example, when preparing the carbon fiber sizing agent, no amino-functionalized ZIF-8 is added, that is, in step (2) only polyetherimide (PEI) solution is used for sizing treatment.

[0058] Comparative Example 2 This comparative example provides a modified carbon fiber, the surface modification method of which differs from that of Example 1 in that: in step (1) of this comparative example, polyetherimide (PEI) is not added when preparing the carbon fiber sizing agent, that is, in step (2) only amino-functionalized ZIF-8 solution is used for sizing treatment.

[0059] Comparative Example 3 This comparative example provides a modified carbon fiber, the surface modification method of which differs from that of Example 1 in that: in step (1) of this comparative example, when preparing the carbon fiber sizing agent, alkylated graphene is used to replace amino-functionalized ZIF-8. The preparation process of alkylated graphene is as follows: 0.5g of graphene oxide with a size not greater than 1μm is dispersed in 40ml of anhydrous acetonitrile, sonicated for 1h, 0.5g of DIC is added, and the reaction is carried out at 70℃ for 4h to activate the carboxyl groups on the surface of graphene oxide; then 1g of octadecylamine is added, and the mixture is refluxed at 80℃ for 8h under nitrogen protection. After the reaction is completed, the product is washed with N,N-dimethylacetamide and acetone in sequence to remove residual DIC and octadecylamine, and then the product is vacuum dried at 60℃ for 6h to obtain alkylated graphene.

[0060] Experimental Example 1 This experiment tested the thermal stability of the modified carbon fibers in Examples 1-9 and Comparative Examples 1-3. The test method was to use a thermogravimetric analyzer to perform thermogravimetric analysis (TGA) on the modified fibers in a nitrogen atmosphere within the range of 30℃ to 800℃, with a heating rate of 20℃ / min. T onset The temperature at which the sample loses 5% of its original mass.

[0061] Table 1 Initial thermal decomposition temperature of sizing agent

[0062] Results analysis: Comparing the results of Examples 1-9 and Comparative Example 1, it can be seen that the addition of amino-functionalized ZIF-8 to the carbon fiber sizing agents of Examples 1-9 resulted in a lower initial degradation temperature and a higher residual rate. According to the carbon fiber sizing agents of Examples 1-4 (the amount of ZIF-8 added to the carbon fiber sizing agent is 1%-10% of the mass of PEI), compared with the carbon fiber sizing agent of Comparative Example 1, the initial degradation temperature of the sizing agent was significantly lowered and the residual rate was significantly increased.

[0063] In addition, the carbon fiber sizing agent of Example 2 (with 7% of the mass of polyetherimide added by amino-functionalized ZIF-8) had a lower initial degradation temperature but a higher residual rate compared to the carbon fiber sizing agent of Example 1 (with 5% of the mass of polyetherimide added by amino-functionalized ZIF-8). In contrast, the carbon fiber sizing agent of Comparative Example 1, which did not contain ZIF-8 or amino-functionalized ZIF-8, had a higher initial degradation temperature (512°C) and a lower residual rate (48%).

[0064] The reason for this is that ZIF-8 particles have high thermal stability, and the addition of ZIF-8 particles to polyetherimide (PEI) exhibits a synergistic effect, reducing the degradation of the sizing agent and increasing the residual rate.

[0065] Experimental Example 2 In this experiment, the interfacial shear strength (IFSS) of the modified carbon fibers prepared in Examples 1-9 and Comparative Examples 1-3 was determined using the microbead debonding method: A single carbon fiber was fixed to a reinforcing sheet. Epoxy resin, curing agent, and acetone were mixed in a specific ratio, thoroughly stirred, and allowed to stand until no more air bubbles appeared. Then, a small amount of resin was dripped onto the fiber for curing. After curing, resin droplets with a diameter of 40-80 mm were peeled off the carbon fiber using the clamps of the microbead debonding device. The test results are shown in Table 2.

[0066] Table 2 Interfacial shear strength of modified carbon fibers

[0067] Results analysis: (1) Comparing the results of Example 1, Example 2 and Comparative Examples 1-2, it can be seen that the amount of ZIF-8 added in the carbon fiber sizing agent used in Example 2 is 1% of the mass of PEI. The interfacial shear strength (IFSS) value of the modified carbon fiber is relatively high. The carbon fiber sizing agent used in Comparative Example 1 does not add ZIF-8 and amino-functionalized ZIF-8. The IFSS of the modified carbon fiber is only 46 MPa. The carbon fiber sizing agent used in Comparative Example 2 only uses amino-functionalized ZIF-8. The IFSS of the modified carbon fiber is only 43 MPa. The carbon fiber sizing agent used in Comparative Example 3 adopts the combination of PEI and alkyl graphene. The improvement of the interfacial performance of the modified carbon fiber is limited.

[0068] As can be seen from the results of Examples 1 to 4, the amount of ZIF-8 added to the carbon fiber sizing agent used in this application is 1% to 10% of the mass of PEI, which can improve the interfacial shear strength (IFSS) value of the modified carbon fiber to a certain extent.

[0069] The reason for this is that the nano-rough structure of amino-functionalized ZIF-8 in the carbon fiber sizing agent can enhance the mechanical interlocking between carbon fiber and resin, and the polar groups of polyetherimide (PEI) provide chemical bonding, thereby improving the interfacial properties of carbon fiber.

[0070] (2) According to the results of Examples 1, 5 and 6, it can be seen that when preparing amino-functionalized ZIF-8, controlling the mass ratio of ZIF-8 to 3-aminopropyltriethoxysilane to be 1:0.5~1:2 will result in amino-functionalized ZIF-8 having a good effect on improving interfacial properties, which is reflected in the high interfacial shear strength (IFSS) value of the modified carbon fiber.

[0071] (3) According to the results of Examples 1, 7 and 8, it can be seen that adjusting the power and time of plasma treatment of carbon fibers can improve the interfacial properties of modified carbon fibers. In particular, Example 7 uses plasma treatment with higher power, and the modified carbon fibers have a higher IFSS value.

[0072] The results of Examples 1 and 9 show that adding a plasma treatment process during the modification of carbon fibers can improve the interfacial properties of the modified carbon fibers.

[0073] The reason for this is that plasma treatment increases the number of surface active groups on carbon fibers, strengthens their chemical bonding with the resin, and thus improves interfacial properties.

[0074] In summary, the carbon fiber sizing agent, modified carbon fiber, composite material, and method of this application can improve the interfacial bonding strength and heat resistance between carbon fiber and resin matrix in carbon fiber composite materials.

[0075] The above description is merely an embodiment of this application and is not intended to limit the scope of protection of this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the scope of protection of this application.

Claims

1. A carbon fiber sizing agent, characterized in that, It comprises the following components: polyetherimide, amino-functionalized ZIF-8, and organic solvent, wherein the mass of the amino-functionalized ZIF-8 is 1% to 10% of the mass of the polyetherimide.

2. The carbon fiber sizing agent according to claim 1, characterized in that, The amino-functionalized ZIF-8 includes a material obtained by amino-modifying ZIF-8 using a silane coupling agent. And / or, the mass concentration of the solution composed of the polyetherimide and the organic solvent is 0.001 g / mL to 0.1 g / mL; And / or, the organic solvent includes at least one of N-methylpyrrolidone and dimethylformamide.

3. A method for preparing a carbon fiber sizing agent as described in claim 1 or 2, characterized in that, It includes the following steps: The polyetherimide is dissolved in the organic solvent to form a solution, and then the amino-functionalized ZIF-8 is uniformly dispersed in the solution.

4. The method for preparing the carbon fiber sizing agent according to claim 3, characterized in that, The preparation method of the amino-functionalized ZIF-8 includes the following steps: dispersing ZIF-8 in a solvent, adding a silane coupling agent, reacting at 70~80℃ for 5~8 hours, and obtaining the amino-functionalized ZIF-8 by centrifugation and drying, wherein the silane coupling agent includes 3-aminopropyltriethoxysilane, and the mass ratio of ZIF-8 to the silane coupling agent is 1:(0.5~2).

5. The method for preparing the carbon fiber sizing agent according to claim 3, characterized in that, The method for uniformly dispersing amino-functionalized ZIF-8 in the solution includes: adding amino-functionalized ZIF-8 to the solution and ultrasonically dispersing it for 30 to 60 minutes, wherein the ultrasonic dispersion power is 200 to 500 W.

6. A method for surface modification of carbon fiber, characterized in that, It includes the following steps: The carbon fiber is impregnated with the carbon fiber sizing agent as described in claim 1 or 2 for sizing treatment, and then dried to obtain modified carbon fiber.

7. The surface modification method for carbon fibers according to claim 6, characterized in that, The carbon fibers are first subjected to plasma treatment, and then to sizing treatment.

8. The surface modification method for carbon fibers according to claim 7, characterized in that, The gas used for plasma treatment is argon or oxygen, and the gas pressure is 10~100 Pa. And / or, the plasma treatment power is 50~200 W, and the time is 1~10 minutes.

9. A modified carbon fiber, characterized in that, It is prepared using the surface modification method of carbon fiber as described in any one of claims 6 to 8.

10. A composite material, characterized in that, It includes a resin matrix and the modified carbon fiber as described in claim 9.

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