Sizing agent, carbon fiber, preparation method and composite material

Abstract

The embodiment of the invention provides a sizing agent, a carbon fiber, a preparation method and a composite material, and relates to the technical field of carbon fiber production. The sizing agent provided by the embodiment of the invention comprises the following components in parts by weight: 20-40 parts of an epoxy resin prepolymer; 10 to 20 parts of polyurethane modified epoxy resin; 1-5 parts of fatty acid amide; and 40-60 parts of water. The carbon fiber provided by the embodiment of the invention comprises a carbon fiber body and a coating layer positioned on the surface of the carbon fiber body, wherein the coating layer is formed by drying the sizing agent. According to the sizing agent, the carbon fiber, the preparation method and the composite material, the sized carbon fiber is good in wear resistance and suitable for a carbon fiber winding process, and the formed composite material is good in interface bonding strength and tensile strength.

Description

Technical Field

[0001] The present application relates to the technical field of carbon fiber production, and in particular to a sizing agent, carbon fiber, a preparation method and a composite material. Background Art

[0002] Carbon fiber is a one-dimensional carbon material characterized by high specific strength, high specific modulus, high temperature resistance, and low density, making it a typical reinforcement. However, due to its high carbon content and high modulus, carbon fiber itself is brittle and has poor wear resistance. Mechanical friction during the manufacturing process can easily lead to breakage and fuzzing of the carbon fiber filaments. This fuzzing phenomenon is particularly severe for high-modulus carbon fiber products, which contain carbon content exceeding 99%. To address these issues, carbon fibers are typically sizing treated to effectively protect them, enhance wear resistance, and reduce the incidence of breakage and fuzzing.

[0003] At present, epoxy emulsion sizing agents are usually used for sizing treatment. This type of sizing agent mostly uses glycidyl ether epoxy resins such as E51 and E44 as the main resin. For composite materials composed of carbon fibers and epoxy resin matrices, this type of sizing agent has good interfacial bonding strength with the epoxy resin matrix. When using this type of sizing agent to impregnate and size carbon fibers, the sizing agent content on the carbon fiber surface needs to be high in order to better protect the carbon fibers and improve the wear resistance of the carbon fibers; especially in the high-modulus carbon fiber winding process, the production speed is fast, and the high-modulus carbon fibers themselves are more brittle. The fibers require multiple rollers, which places higher demands on the wear resistance of the carbon fibers. However, in subsequent applications, a high sizing agent content on the carbon fiber surface is not conducive to the impregnation of the carbon fibers, thereby reducing the tensile properties of the composite material. Summary of the Invention

[0004] The purpose of the embodiments of the present application is to provide a sizing agent, carbon fiber, preparation method and composite material. The sizing carbon fiber has good wear resistance, is suitable for carbon fiber winding process, and the composite material has good interface bonding strength and tensile strength.

[0005] In a first aspect, the present invention provides a sizing agent comprising the following components in parts by weight: 20-40 parts of epoxy resin prepolymer; 10-20 parts of polyurethane modified epoxy resin; 1-5 parts of fatty amide; 40~60 parts of water.

[0006] In the above technical solution, epoxy resin prepolymer and polyurethane modified epoxy resin are used as the main resin in the sizing agent. They both contain hydrophilic groups and can be directly emulsified without an emulsifier. In particular, polyurethane modified epoxy resin is more active and tougher than ordinary epoxy resin. It can better transfer stress when the interface is stressed, thereby improving the interfacial bonding strength. The sizing agent also uses fatty amide as a lubricant. Unlike ordinary lubricants such as lipids, alcohols or paraffin, fatty amide contains a certain amount of amide groups, which can form an isolation layer on the surface of carbon fiber, thereby reducing the amount of fiber fuzzing. Under the premise of low sizing agent content on the fiber surface, the wear resistance of the fiber after sizing is improved, thereby improving the carbon fiber winding processability.

[0007] At the same time, by utilizing the characteristics of the reaction between fatty amide and epoxy groups (no reaction at room temperature, epoxy ring-opening curing reaction at high temperature), the interface performance of the composite material can be effectively enhanced, the shear strength of the composite material can be improved, and it is conducive to the development of more application scenarios. Specifically, fatty amide and epoxy resin need to be above a relatively high temperature to react, and will not react during the sizing and drying stage. Fatty amide mainly plays a lubricating role on the fiber surface and will not affect the properties of carbon fiber. When the fiber sized with the sizing agent is used to form a composite material with an epoxy resin matrix, the temperature of the reaction between fatty amide and epoxy resin is reduced due to the presence of a curing agent in the system, and / or the higher processing temperature causes the amide group to produce a ring-opening addition reaction with the epoxy group in the epoxy resin matrix, which is conducive to the combination of carbon fiber and epoxy resin matrix and improves the interface bonding strength of the composite material. Therefore, the sized carbon fiber has good wear resistance, is suitable for carbon fiber winding process, and the composite material formed has good interface bonding strength and tensile strength.

[0008] In a possible implementation, the epoxy resin prepolymer includes at least one of an etherification reaction type modified epoxy resin and a grafting reaction type ion group modified epoxy resin.

[0009] In a possible implementation, the etherification reaction type modified epoxy resin includes at least one of a polyethylene oxide modified epoxy resin and a polyoxypropylene modified epoxy resin; And / or, the graft reaction type ion-modified epoxy resin includes at least one of an acrylic acid graft modified epoxy resin and a maleic anhydride graft modified epoxy resin.

[0010] In one possible implementation, the fatty amide includes at least one of oleamide, ethylene bisoleamide, stearamide and erucamide.

[0011] In a second aspect, an embodiment of the present application provides a method for preparing the sizing agent provided in the first aspect, comprising the following steps: mixing the epoxy resin prepolymer, the polyurethane-modified epoxy resin and the fatty amide to obtain a mixed solution; The water is added to the mixed solution and sheared and dispersed to obtain the sizing agent.

[0012] In the above technical solution, the liquid polyurethane-modified epoxy resin is first fully mixed with other components to improve the mixing uniformity, and then the mixture is dispersed and mixed with water by shearing to achieve a good emulsification effect.

[0013] In a possible implementation, the shear dispersion method includes: shear dispersion at 2000-3000 r / min for 3-5 min.

[0014] In a third aspect, an embodiment of the present application provides a carbon fiber, comprising a carbon fiber body and a coating layer located on the surface of the carbon fiber body, wherein the coating layer is formed by drying the sizing agent provided in the first aspect.

[0015] In a fourth aspect, an embodiment of the present application provides a method for preparing carbon fiber, comprising the following steps: The carbon fiber body is immersed in the sizing agent provided in the first aspect and then dried.

[0016] In a possible implementation, the immersion temperature is 25-35 min° C., and the immersion time is 1-5 min. And / or, the drying temperature is 120-150° C., and the drying time is 15-20 seconds.

[0017] In the above technical solution, during the drying process, a certain drying temperature is controlled to achieve curing, and a short drying time is controlled to avoid the reaction of the fatty amide in the sizing agent with the epoxy resin, thereby ensuring the fiber sizing effect.

[0018] In a fifth aspect, an embodiment of the present application provides a composite material comprising an epoxy resin matrix and the carbon fiber provided in the third aspect or the carbon fiber prepared by the method for preparing the carbon fiber provided in the fourth aspect.

[0019] In the above technical solution, in the composite material composed of carbon fiber and epoxy resin, carbon fiber is used as a reinforcing material due to its high strength and high modulus characteristics, and epoxy resin is usually used as a matrix material due to its good adhesion, corrosion resistance and easy processing; and the composite material composed of the epoxy resin matrix and the carbon fiber sized with a specific sizing agent has good interface bonding strength and tensile strength. DETAILED DESCRIPTION

[0020] Carbon fiber is a one-dimensional carbon material characterized by high specific strength, high specific modulus, high temperature resistance, and low density, making it a typical reinforcement. However, due to its high carbon content and high modulus, carbon fiber itself is relatively brittle and has poor wear resistance. Mechanical friction during the manufacturing process can easily lead to breakage and fuzzing of the carbon fiber filaments. This is particularly true for high-modulus carbon fiber products, which contain carbon content exceeding 99%, making fuzzing even more severe. To address these issues, sizing the carbon fibers requires a sizing agent, which effectively protects the fibers, enhances wear resistance, and reduces the incidence of breakage and fuzzing.

[0021] At present, epoxy emulsion sizing agents are usually used for sizing treatment. This type of sizing agent mostly uses glycidyl ether epoxy resins such as E51 and E44 as the main resin. For composite materials composed of carbon fibers and epoxy resin matrices, this type of sizing agent has good interfacial bonding strength with the epoxy resin matrix. When using this type of sizing agent to impregnate and size carbon fibers, the sizing agent needs to reach a content of 1% or even 1.4% on the carbon fiber surface in order to exert a better protective effect on the carbon fibers and improve the wear resistance of the carbon fibers. Especially in the high-modulus carbon fiber winding process, the production speed is fast, and the high-modulus carbon fibers themselves are more brittle. The fibers require multiple rollers, which places higher demands on the wear resistance of the carbon fibers. However, in subsequent applications, the sizing agent content on the carbon fiber surface should not be too much, especially in prepreg, pultrusion and other processes. Excessive sizing agent content on the carbon fiber surface is not conducive to the impregnation of the carbon fibers, thereby reducing the tensile properties of the composite material.

[0022] To make the purpose, technical solutions and advantages of the examples of the present application clearer, the technical solutions in the examples of the present application will be described clearly and completely below. Where specific conditions are not specified in the examples, conventional conditions or conditions recommended by the manufacturer are used. Where the manufacturer of the reagents or instruments is not specified, they are all conventional products that can be purchased commercially.

[0023] The sizing agent, carbon fiber, preparation method and composite material of the embodiments of the present application are described in detail below.

[0024] The present application provides a sizing agent, which comprises the following components, by weight: 20 to 40 parts of epoxy resin prepolymer; 10 to 20 parts of polyurethane-modified epoxy resin; 1 to 5 parts of fatty amide; and 40 to 60 parts of water. For example, the sizing agent comprises the following components, by weight: 20, 25, 30, 35, or 40 parts of epoxy resin prepolymer, or an intermediate value between any two of the above values; 10, 12, 15, 17, or 20 parts of polyurethane-modified epoxy resin, or an intermediate value between any two of the above values; 1, 2, 3, 4, or 5 parts of fatty amide, or an intermediate value between any two of the above values; and 40, 45, 50, 55, or 60 parts of water, or an intermediate value between any two of the above values.

[0025] In this embodiment, epoxy resin prepolymer and polyurethane modified epoxy resin are used as the main resin in the sizing agent. They both contain hydrophilic groups and can be directly emulsified without an emulsifier. In particular, polyurethane modified epoxy resin is more active and has better toughness than ordinary epoxy resin. It can better transfer stress when the interface is stressed, thereby improving the interfacial bonding strength. The sizing agent also uses fatty amide as a lubricant. Unlike ordinary lubricants such as lipids, alcohols or paraffin, fatty amide contains a certain amount of amide groups, which can form an isolation layer on the surface of carbon fiber, thereby reducing the amount of fiber fuzzing. Under the premise of low sizing agent content on the fiber surface, the wear resistance of the fiber after sizing is improved, thereby improving the carbon fiber winding processability.

[0026] In some optional embodiments of the present application, the epoxy resin prepolymer is a water-based epoxy resin prepolymer, and the water-based epoxy resin prepolymer includes at least one of an etherification reaction type modified epoxy resin and a grafting reaction type ion group modified epoxy resin.

[0027] In some optional embodiments of the present application, the etherification reaction type modified epoxy resin includes at least one of a polyethylene oxide modified epoxy resin and a polyoxypropylene modified epoxy resin; And / or, the graft reaction type ion group modified epoxy resin includes at least one of an acrylic acid graft modified epoxy resin and a maleic anhydride graft modified epoxy resin.

[0028] The following is a description of the components used in the examples of this application.

[0029] The epoxy resin prepolymers of the embodiments of the present application can be prepared in-house or commercially available. The structural characteristics of the etherification reaction-modified epoxy resin are that the epoxy resin backbone is connected to polyethylene oxide (PEO) or polypropylene oxide (PPO) segments via ether bonds (—O—) to form a hydrophilic block structure. For example, the structural unit of the polyethylene oxide-modified epoxy resin is -O-(CH2CH2O) n -H; the structural unit of polyoxypropylene modified epoxy resin is -O-(CH2CH(CH3)O) n -H.

[0030] The structural characteristic of grafted reactive ionic modified epoxy resins is that carboxylic acid groups (—COOH) or anhydride groups (—CO—O—CO—) are introduced into the epoxy resin side chains via free radical grafting. For example, the structural unit of acrylic acid grafted modified epoxy resin is -CH2-CH(COOH)-; the structural unit of maleic anhydride grafted modified epoxy resin is -CH2-CH(CO-O-CO-CH=CH)-.

[0031] The polyurethane-modified epoxy resins used in the embodiments of this application can be homemade or commercially available. In some optional embodiments of this application, the polyurethane-modified epoxy resins are characterized by block or graft copolymerization of epoxy resin and polyurethane prepolymers, with a general structural formula: epoxy resin-O-CO-NH-R-NH-CO-O-polyurethane segment, where R represents the residue of a diisocyanate (such as TDI or MDI). This structure combines the rigidity of epoxy resin with the toughness of polyurethane, while also containing hydrophilic groups (such as -NH-COO-), which facilitates dispersion in water.

[0032] The fatty amides of the embodiments of the present application can be prepared in-house or commercially available. In some optional embodiments of the present application, the fatty amides include at least one of oleamide, ethylene bisoleamide, stearamide, and erucamide.

[0033] In this embodiment, if other types of lubricants are used instead of fatty amide, the claimed technical effect cannot be achieved.

[0034] Among them, oleic acid amide (English name Oleic acid amide), also known as oleamide (Oleamide), also known as cis-9-Octadecenoamide (cis-9-Octadecenoamide), is an unsaturated fatty amide and is a white crystalline or granular solid.

[0035] Ethylene bisoleamide is an organic compound with the molecular formula C 38 H 72 N2O2, a synthetic wax, is a pale yellow waxy solid.

[0036] The present invention provides a method for preparing the sizing agent of the aforementioned embodiment, comprising the following steps: S1, mixing epoxy resin prepolymer, polyurethane-modified epoxy resin and fatty amide to obtain a mixed solution; S2. Add water to the mixed solution and disperse it by high-speed shearing to obtain a sizing agent.

[0037] In this embodiment, the liquid polyurethane-modified epoxy resin is first fully mixed with other components to improve mixing uniformity, and then shear-dispersed mixed with water to achieve a good emulsification effect.

[0038] In some optional embodiments of the present application, high-speed shear dispersion is achieved by mixing and dispersing materials through the shearing effect between a high-speed rotating rotor and a stator, typically achieved by a shear disperser; the shear dispersion method includes: shear dispersion at 2000-3000 r / min for 3-5 minutes. For example, the rotation speed is 2000 r / min, 2300 r / min, 2500 r / min, 2700 r / min, 3000 r / min, or any intermediate value thereof, and the shear time is 3 minutes, 3.5 minutes, 4 minutes, 4.5 minutes, 5 minutes, or any intermediate value thereof.

[0039] An embodiment of the present application provides a carbon fiber, comprising a carbon fiber body and a coating layer located on the surface of the carbon fiber body, wherein the coating layer is formed by drying the sizing agent of the aforementioned embodiment.

[0040] In some optional embodiments of the present application, the coating layer content in the carbon fiber is between 0.4 and 1.2 wt%.

[0041] The present invention provides a method for preparing carbon fiber, comprising the following steps: The carbon fiber body is immersed in the sizing agent of the aforementioned embodiment and then dried.

[0042] In this embodiment, the impregnation amount of the sizing agent can be adjusted by controlling the impregnation time or the concentration of the sizing agent, thereby adjusting the coating layer content in the carbon fiber.

[0043] In one possible implementation, the immersion temperature can be room temperature (in actual operation, due to the high temperature in the workshop, it is basically maintained above 25°C), the immersion temperature is 25-35°C, and the immersion time is 1-5 minutes; And / or, the drying temperature is 120-150° C., and the drying time is 15-20 seconds.

[0044] Illustratively, the drying temperature is 120°C, 130°C, 140°C, 150°C or any intermediate value thereof; the drying time is 15s, 16s, 17s, 18s, 20s or any intermediate value thereof.

[0045] In this embodiment, during the drying process, a certain drying temperature is controlled to achieve curing, and a short drying time is controlled to avoid the reaction of the fatty amide in the sizing agent with the epoxy resin, thereby ensuring the fiber sizing effect.

[0046] An embodiment of the present application provides a composite material, comprising an epoxy resin matrix and the carbon fiber of the aforementioned embodiment or the carbon fiber produced by the method for producing the carbon fiber of the aforementioned embodiment.

[0047] In the embodiment of the present application, the composite material is composed of two or more materials with different properties (epoxy resin + carbon fiber), which are macroscopically composed of materials with new properties through physical or chemical methods.

[0048] In this embodiment, in the composite material composed of carbon fiber and epoxy resin, carbon fiber is used as a reinforcing material due to its high strength and high modulus characteristics, and epoxy resin is usually used as a matrix material due to its good adhesion, corrosion resistance and easy processing; and the composite material composed of the epoxy resin matrix and the carbon fiber sized with a specific sizing agent has good interface bonding strength and tensile strength.

[0049] The features and performance of the present application are further described in detail below with reference to the embodiments.

[0050] Example 1 This embodiment provides a composite material, and the specific preparation process is as follows: According to parts by weight, 20 parts of epoxy resin prepolymer (using polyethylene oxide modified epoxy resin (etherification reaction type modified epoxy resin), specifically BASF's EC 141), 20 parts of polyurethane modified epoxy resin (specifically Nan Ya's NPER-133L) and 5 parts of fatty amide (specifically oleic acid amide) are stirred and mixed to obtain a mixed solution; then, 55 parts of deionized water are added to the mixed solution, and shear dispersion is carried out at 2000 r / min for 5 minutes using a high-speed shear disperser to obtain a sizing agent.

[0051] The unsized M40 carbon fiber (carbon fiber body) is impregnated in a sizing tank filled with the above-mentioned sizing agent. The temperature of the sizing agent is 30°C, the impregnation time is 2 minutes, and then dried at 130°C for 20 seconds to obtain an M40 carbon fiber with a coating layer on the surface, i.e., carbon fiber.

[0052] The obtained carbon fiber and epoxy resin are taken in a ratio of 35wt% of epoxy resin content, compounded by a winding machine, and cured to form a composite material.

[0053] Example 2 This embodiment provides a composite material, which differs from Example 1 in that: in this embodiment, 40 parts of epoxy resin prepolymer, 10 parts of polyurethane-modified epoxy resin, and 1 part of fatty amide are stirred and mixed, measured by weight, to obtain a mixed solution; subsequently, 49 parts of deionized water are added to the mixed solution, and the mixture is sheared and mixed at 2000 r / min for 5 minutes using a high-speed shear disperser to obtain a sizing agent; and finally, a composite material is formed.

[0054] Example 3 This embodiment provides a composite material, which differs from Example 1 in that: in this embodiment, 30 parts of epoxy resin prepolymer, 15 parts of polyurethane-modified epoxy resin, and 3 parts of fatty amide are stirred and mixed, measured by weight, to obtain a mixed solution; subsequently, 52 parts of deionized water are added to the mixed solution, and the mixture is sheared and mixed at 2000 r / min for 5 minutes using a high-speed shear disperser to obtain a sizing agent; and finally, a composite material is formed.

[0055] Example 4 This embodiment provides a composite material, which differs from embodiment 1 in that: in this embodiment, the epoxy resin prepolymer adopts acrylic acid graft-modified epoxy resin (grafted reactive ion-modified epoxy resin); finally, a composite material is formed.

[0056] Example 5 This embodiment provides a composite material, which differs from embodiment 1 in that: in this embodiment, the fatty amide specifically adopts ethylene bisoleamide; and finally a composite material is formed.

[0057] Example 6 This embodiment provides a composite material, which differs from embodiment 1 in that: in this embodiment, during the impregnation treatment, the impregnation time is 10 minutes; and finally a composite material is formed.

[0058] Example 7 This embodiment provides a composite material, which differs from embodiment 1 in that: in this embodiment, the drying temperature after impregnation is 160° C.; and finally a composite material is formed.

[0059] Example 8 This embodiment provides a composite material, which differs from embodiment 1 in that: in this embodiment, the drying time after impregnation is 60 seconds; and finally a composite material is formed.

[0060] Comparative Example 1 This comparative example provides a composite material, which differs from Example 1 in that: in this comparative example, 20 parts of epoxy resin prepolymer and 20 parts of polyurethane-modified epoxy resin are stirred and mixed, in parts by weight, to obtain a mixed solution; subsequently, 60 parts of deionized water are added to the mixed solution, and the mixture is sheared and mixed at 2000 r / min for 5 minutes using a high-speed shear disperser to obtain a sizing agent; and finally, a composite material is formed.

[0061] Comparative Example 2 This comparative example provides a composite material, which differs from Example 1 in that: in this comparative example, liquid paraffin is used to replace fatty amide; and finally a composite material is formed.

[0062] The carbon fibers and composite materials in the above embodiments and comparative examples were tested.

[0063] 1. According to the standard "GB / T 31290-2014 Determination of the fuzzing amount of carbon fiber", the fuzzing amount of the carbon fibers obtained by sizing treatment in each embodiment and comparative example was tested.

[0064] 2. The composite materials of the embodiments and comparative examples were made into Noll rings, and interlaminar shear and tensile tests were performed on each Noll ring sample according to GB / T 1458 standard.

[0065] The test results of the carbon fibers and composite materials of the above examples and comparative examples are shown in Table 1.

[0066] Table 1 Performance results of different carbon fibers and composite materials

[0067] As can be seen from Table 1, the amount of fuzzing of the carbon fibers obtained by sizing with a specific sizing agent in Examples 1 to 8 is small, indicating that the sizing agent has a good protective effect on the carbon fibers and the carbon fibers have good wear resistance; and the layer shear strength of the Nohl rings in Examples 1 to 8 is high, indicating that the interface bonding strength between the carbon fibers and the epoxy resin matrix in the composite materials is good; and the tensile strength of the Nohl rings is good, indicating that the composite materials have excellent tensile properties.

[0068] No lubricant was used in the sizing agent of Comparative Example 1, and the fuzzing amount of the carbon fiber obtained by sizing treatment was as high as 28.5 mg / 50 m, which was significantly higher than the fuzzing amount of the carbon fiber of the embodiment. Since the wear resistance of the carbon fiber is poor, the tensile properties of the composite material are affected to a certain extent. Therefore, the tensile strength of the Noll ring of Comparative Example 1 is lower than the tensile strength of the Noll ring of the embodiment; and the shear strength of the Noll ring layer of Comparative Example 1 is lower than the shear strength level of the Noll ring layer of the embodiment, indicating that the interface bonding strength of the composite material of Comparative Example 1 is relatively poor.

[0069] The sizing agent of Comparative Example 2 uses liquid paraffin as a lubricant, and the amount of fuzzing of the carbon fiber obtained by sizing treatment is significantly reduced compared with the amount of fuzzing of the carbon fiber in Comparative Example 1, indicating that the wear resistance of the carbon fiber is improved; but the layer shear strength of the Noll ring of Comparative Example 2 is significantly reduced compared with Comparative Example 1, and is significantly lower than the layer shear strength of the Noll ring of the embodiment, indicating that liquid paraffin affects the bonding between the carbon fiber and the epoxy resin, and has a significant negative impact on the interlayer bonding performance; at the same time, the tensile strength of the Noll ring of Comparative Example 2 is also reduced to a certain extent compared with Comparative Example 1, and is significantly lower than the tensile strength of the Noll ring of the embodiment, indicating that liquid paraffin will affect the tensile properties of the composite material.

[0070] In summary, the sizing agent, carbon fiber, and preparation method of the embodiments of the present application and the carbon fiber of the composite material have good wear resistance, are suitable for the carbon fiber winding process, and the composite material composed thereof has good interface bonding strength and tensile strength.

[0071] The above description is merely an embodiment of the present application and is not intended to limit the scope of protection of the present application. For those skilled in the art, various modifications and variations of the present application are possible. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present application shall be included in the scope of protection of the present application.

Claims

1. A sizing agent, characterized in that Calculated by weight, it includes the following components: 20-40 parts of epoxy resin prepolymer; 10-20 parts of polyurethane modified epoxy resin; 1-5 parts of fatty amide; 40~60 parts of water.

2. The sizing agent according to claim 1, characterized in that The epoxy resin prepolymer includes at least one of an etherification reaction type modified epoxy resin and a graft reaction type ion group modified epoxy resin.

3. The sizing agent according to claim 2, characterized in that The etherification reaction type modified epoxy resin includes at least one of polyethylene oxide modified epoxy resin and polypropylene oxide modified epoxy resin; And / or, the graft reaction type ion-modified epoxy resin includes at least one of an acrylic acid graft modified epoxy resin and a maleic anhydride graft modified epoxy resin.

4. The sizing agent according to claim 1, characterized in that The fatty amide includes at least one of oleamide, ethylene bisoleamide, stearamide and erucamide.

5. A method for preparing a sizing agent according to any one of claims 1 to 4, characterized in that: The following steps are involved: mixing the epoxy resin prepolymer, the polyurethane-modified epoxy resin and the fatty amide to obtain a mixed solution; The water is added to the mixed solution and sheared and dispersed to obtain the sizing agent.

6. The method for preparing a sizing agent according to claim 5, wherein The shear dispersion method includes: shear dispersion at 2000-3000 r / min for 3-5 minutes.

7. A carbon fiber, characterized in that The invention comprises a carbon fiber body and a coating layer located on the surface of the carbon fiber body, wherein the coating layer is formed by drying the sizing agent according to any one of claims 1 to 4.

8. A method for preparing carbon fiber, characterized in that: The following steps are involved: The carbon fiber body is immersed in the sizing agent according to any one of claims 1 to 4, and then dried.

9. The method for preparing a sizing agent according to claim 8, wherein The immersion temperature is 25-35 min°C, and the immersion time is 1-5 min; And / or, the drying temperature is 120-150° C., and the drying time is 15-20 seconds.

10. A composite material, characterized in that The invention comprises an epoxy resin matrix and the carbon fiber according to claim 7 or the carbon fiber prepared by the method for preparing the carbon fiber according to any one of claims 8 to 9.

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