Carbon fiber sizing agent as well as preparation method and application thereof

Abstract

The invention provides a carbon fiber sizing agent as well as a preparation method and application thereof. The carbon fiber sizing agent is prepared from the following raw materials in parts by weight: 100-150 parts of epoxy resin, 100-150 parts of polyurethane modified epoxy resin, 100-150 parts of polyethylene glycol, 1-2 parts of an organic solvent, 0.2-0.5 part of a catalyst, 5-10 parts of an alcohol amine compound, 5-15 parts of an acidic pH regulator and 300-500 parts of water. The carbon fiber sizing agent is not prone to layering, good in high-temperature and low-temperature resistance and convenient to store, the reaction for preparing the raw materials can be carried out in the same reaction kettle, and the production efficiency is greatly improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of sizing agents, and particularly relates to a sizing agent for carbon fibers, a preparation method thereof, and an application thereof. Background Art

[0002] The sizing agent is a key factor affecting the use effect of carbon fibers. A high-quality sizing agent can reduce surface defects of the fibers and improve the bonding property between the fibers and the resin. The research on carbon fiber sizing agents abroad is relatively mature, and companies such as Toray and Mitsubishi Rayon in Japan are in the leading position in the research of carbon fiber sizing agents. However, the formula of the sizing agent belongs to the core business secret and is not publicly disclosed. Currently, the sizing agents used by major foreign carbon fiber manufacturers are mostly self-developed, and the technology is kept confidential and not sold externally.

[0003] Compared with foreign countries, the research and application of sizing agents in China started relatively late, and there are still many problems with product performance and product quality stability. Many carbon fiber manufacturers are still using a large amount of imported sizing agents from abroad. Especially for high-performance carbon fibers, the existing domestic sizing agent products cannot meet the requirements, and imported sizing agents are generally expensive and have a long procurement cycle, which seriously affects the development of carbon fiber production enterprises in China. Some of the sizing agents used by existing carbon fiber manufacturers are self-developed, with the technology kept confidential and not sold externally. Most of the sizing agents of carbon fiber manufacturers are purchased externally. The sizing agent products sold publicly either have a high price or have many problems with product performance and product quality stability.

[0004] Therefore, developing a carbon fiber sizing agent with stable product performance and product quality is of great significance for the development of domestic carbon fibers. Summary of the Invention

[0005] Aiming at the deficiencies of the prior art, the purpose of the present invention is to provide a sizing agent for carbon fibers, a preparation method thereof, and an application thereof. The sizing agent for carbon fibers is not easy to delaminate, has good high and low temperature resistance, is convenient for storage, and the reactions of the raw materials for preparation can be carried out in the same reaction kettle without the need to replace the reactor and remove organic solvents during the process, greatly improving the production efficiency.

[0006] To achieve this purpose, the present invention adopts the following technical solutions:

[0007] In the first aspect, the present invention provides a sizing agent for carbon fibers. The raw materials for preparing the sizing agent for carbon fibers include, by weight: 100 - 150 parts of epoxy resin, 100 - 150 parts of polyurethane-modified epoxy resin, 100 - 150 parts of polyethylene glycol, 1 - 2 parts of organic solvent, 0.2 - 0.5 part of catalyst, 5 - 10 parts of alkanolamine compound, 5 - 15 parts of acidic pH regulator, and 300 - 500 parts of water.

[0008] The weight parts of the epoxy resin are 100 - 150 parts. For example, it can be 100 parts, 105 parts, 110 parts, 115 parts, 120 parts, 125 parts, 130 parts, 135 parts, 140 parts, 145 parts, 150 parts, and specific point values between the above point values. Due to space limitations and for the sake of simplicity, the present invention does not exhaustively list the specific point values included in the above range.

[0009] The weight parts of the polyurethane - modified epoxy resin are 100 - 150 parts. For example, it can be 100 parts, 105 parts, 110 parts, 115 parts, 120 parts, 125 parts, 130 parts, 135 parts, 140 parts, 145 parts, 150 parts, and specific point values between the above point values. Due to space limitations and for the sake of simplicity, the present invention does not exhaustively list the specific point values included in the above range.

[0010] The weight parts of the polyethylene glycol are 100 - 150 parts. For example, it can be 100 parts, 105 parts, 110 parts, 115 parts, 120 parts, 125 parts, 130 parts, 135 parts, 140 parts, 145 parts, 150 parts, and specific point values between the above point values. Due to space limitations and for the sake of simplicity, the present invention does not exhaustively list the specific point values included in the above range.

[0011] The weight parts of the organic solvent are 1 - 2 parts. For example, it can be 1 part, 1.2 parts, 1.4 parts, 1.6 parts, 1.8 parts, 2 parts, and specific point values between the above point values. Due to space limitations and for the sake of simplicity, the present invention does not exhaustively list the specific point values included in the above range.

[0012] The weight parts of the catalyst are 0.2 - 0.5 parts. For example, it can be 0.2 parts, 0.3 parts, 0.4 parts, 0.5 parts, and specific point values between the above point values. Due to space limitations and for the sake of simplicity, the present invention does not exhaustively list the specific point values included in the above range.

[0013] The weight parts of the alkanolamine compound are 5 - 10 parts. For example, it can be 5 parts, 6 parts, 7 parts, 8 parts, 9 parts, 10 parts, and specific point values between the above point values. Due to space limitations and for the sake of simplicity, the present invention does not exhaustively list the specific point values included in the above range.

[0014] The weight parts of the acidic pH regulator are 5 - 15 parts. For example, it can be 5 parts, 5.5 parts, 6 parts, 7 parts, 8 parts, 9 parts, 10 parts, 11 parts, 12 parts, 13 parts, 14 parts, 15 parts, and specific point values between the above point values. Due to space limitations and for the sake of simplicity, the present invention does not exhaustively list the specific point values included in the above range.

[0015] The weight portion of the water is 300-500 portions, for example, it can be 300 portions, 305 portions, 310 portions, 350 portions, 380 portions, 400 portions, 410 portions, 450 portions, 480 portions, 500 portions, and specific point values between the above point values. Due to space limitations and for the sake of simplicity, the present invention does not exhaustively list the specific point values included in the above range.

[0016] In the present invention, the epoxy resin is modified by reacting with polyethylene glycol to increase the toughness of the epoxy resin and reduce its hardness. An alcohol amine compound is added to amine-modify the epoxy resin, introducing an amino group onto the molecular chain of the epoxy resin to enhance the activity of the epoxy resin. An acidic pH regulator is added for acidification to enhance the hydrophilicity of the epoxy resin and adjust the pH value of the sizing agent.

[0017] Preferably, the number average molecular weight of the epoxy resin is 300-1000, for example, it can be 300, 400, 500, 600, 700, 800, 900, 1000, and specific point values between the above point values. Due to space limitations and for the sake of simplicity, the present invention does not exhaustively list the specific point values included in the above range.

[0018] Preferably, the catalyst includes triphenylphosphine.

[0019] Preferably, the alcohol amine compound includes any one or a combination of at least two of ethanolamine, diethanolamine, or triethanolamine.

[0020] Preferably, the acidic pH regulator includes any one or a combination of at least two of acetic acid, dilute hydrochloric acid, dilute sulfuric acid, or dilute nitric acid.

[0021] Preferably, the number average molecular weight of the polyethylene glycol is 2000-8000, for example, it can be 2000, 3000, 5000, 6000, 8000, and specific point values between the above point values. Due to space limitations and for the sake of simplicity, the present invention does not exhaustively list the specific point values included in the above range.

[0022] Preferably, the organic solvent includes any one or a combination of at least two of acetone, xylene, or pyrrolidone.

[0023] Preferably, the water includes demineralized water.

[0024] In the second aspect, the present invention provides a preparation method of the carbon fiber sizing agent as described in the first aspect, and the preparation method includes:

[0025] (1) Mix epoxy resin, polyurethane-modified epoxy resin, polyethylene glycol, organic solvent, and catalyst, and carry out a reaction to obtain alcoholized epoxy resin;

[0026] (2) Mix the alcoholized epoxy resin obtained in step (1) with the alcohol amide compound and react to obtain the aminated epoxy resin;

[0027] (3) Mix the aminated epoxy resin obtained in step (2) with an acidic pH regulator, react, and then add water and mix evenly to obtain the sizing agent for carbon fibers.

[0028] Preferably, the reaction in step (1) is carried out under stirring conditions.

[0029] Preferably, the stirring speed is 10 - 200 rpm, for example, it can be 10 rpm, 20 rpm, 30 rpm, 50 rpm, 80 rpm, 100 rpm, 120 rpm, 150 rpm, 180 rpm, 200 rpm, and specific point values between the above point values. Due to space limitations and for the sake of brevity, the specific point values included in the scope of the present invention are not exhaustively listed herein.

[0030] Preferably, the reaction temperature in step (1) is 100 - 150 °C, for example, it can be 100 °C, 105 °C, 110 °C, 120 °C, 130 °C, 140 °C, 150 °C, and specific point values between the above point values. Due to space limitations and for the sake of brevity, the specific point values included in the scope of the present invention are not exhaustively listed herein.

[0031] Preferably, the reaction time in step (1) is 8 - 12 h, for example, it can be 8 h, 8.2 h, 8.4 h, 8.5 h, 9 h, 9.5 h, 10 h, 10.5 h, 11 h, 11.5 h, 12 h, and specific point values between the above point values. Due to space limitations and for the sake of brevity, the specific point values included in the scope of the present invention are not exhaustively listed herein.

[0032] Preferably, the reaction temperature in step (2) is 80 - 100 °C, for example, it can be 80 °C, 85 °C, 90 °C, 95 °C, 100 °C, and specific point values between the above point values. Due to space limitations and for the sake of brevity, the specific point values included in the scope of the present invention are not exhaustively listed herein.

[0033] Preferably, the reaction time in step (2) is 20 - 40 min, for example, it can be 20 min, 25 min, 30 min, 35 min, 38 min, 40 min, and specific point values between the above point values. Due to space limitations and for the sake of brevity, the specific point values included in the scope of the present invention are not exhaustively listed herein.

[0034] Preferably, the temperature of the reaction in step (3) is 30 - 50°C, for example, it can be 30°C, 35°C, 40°C, 45°C, 50°C, and the specific point values between the above point values. Due to space limitations and for the sake of brevity, the present invention does not exhaustively list the specific point values included in the said range.

[0035] Preferably, the time of the reaction in step (3) is 1 - 3 h, for example, it can be 1 h, 1.5 h, 2 h, 2.5 h, 3 h, and the specific point values between the above point values. Due to space limitations and for the sake of brevity, the present invention does not exhaustively list the specific point values included in the said range.

[0036] Preferably, the mixing in step (3) is carried out under stirring conditions.

[0037] Preferably, the temperature of the stirring in step (3) is 30 - 50°C, for example, it can be 30°C, 35°C, 40°C, 45°C, 50°C, and the specific point values between the above point values. Due to space limitations and for the sake of brevity, the present invention does not exhaustively list the specific point values included in the said range.

[0038] Preferably, the time of the stirring in step (3) is 1 - 3 h, for example, it can be 1 h, 1.5 h, 2 h, 2.5 h, 3 h, and the specific point values between the above point values. Due to space limitations and for the sake of brevity, the present invention does not exhaustively list the specific point values included in the said range.

[0039] Preferably, the speed of the stirring in step (3) is 300 - 1500 rpm, for example, it can be 300 rpm, 350 rpm, 400 rpm, 450 rpm, 500 rpm, 550 rpm, 600 rpm, 650 rpm, 700 rpm, 750 rpm, 800 rpm, 900 rpm, 950 rpm, 1000 rpm, 1100 rpm, 1200 rpm, 1500 rpm, and the specific point values between the above point values. Due to space limitations and for the sake of brevity, the present invention does not exhaustively list the specific point values included in the said range.

[0040] In the third aspect, the present invention provides an application of the sizing agent for carbon fiber as described in the first aspect in carbon fiber or graphite fiber.

[0041] Compared with the prior art, the present invention has the following beneficial effects:

[0042] The present invention provides a sizing agent for carbon fiber. The sizing agent for carbon fiber has stable performance, is not easy to delaminate, has good high and low temperature resistance, and is convenient for storage. The sizing agent can perfectly replace imported sizing agents, and the production cost is much lower than that of imported sizing agents. The sizing agent improves production efficiency, with an epoxy value of 0.28 - 0.3 mol / 100 g, freeze-thaw stability of 1 - 5 times, high temperature stability of 1 - 5 times, a particle size of 208 - 218 nm. After treating carbon fiber with the sizing agent, the tensile strength of the carbon fiber is 5270 - 5300 Mpa, the elongation at break is 2.15%, the elastic modulus is 245 - 247 GPa, the linear density is 789 - 791 g / km, the resistivity is 1.5×10 -3 -1.51×0 -3 Ω·m, the bundle wire width is 5.49 - 6.77 mm, the vertical suspension is 3.6 - 6.1 cm, the amount of hairiness is 4.6 - 20.4 mg / 50 m, and the interlaminar shear is 89 - 104 MPa. Detailed implementation manners

[0043] The technical solution of the present invention will be further described below through specific implementation manners. Those skilled in the art should understand that the embodiments are only for helping to understand the present invention and should not be regarded as specific limitations to the present invention.

[0044] Example 1

[0045] This example provides a sizing agent for carbon fiber and its preparation method. The preparation raw materials of the sizing agent for carbon fiber include, by weight: 100 parts of epoxy resin, 100 parts of polyurethane-modified epoxy resin, 120 parts of polyethylene glycol, 1 part of pyrrolidone, 0.2 part of triphenylphosphine, 6 parts of ethanolamine, 10 parts of acetic acid, and 480 parts of deionized water.

[0046] The preparation method includes:

[0047] (1) Mix epoxy resin, polyurethane-modified epoxy resin, polyethylene glycol, pyrrolidone, and triphenylphosphine, and react at 130°C for 10 h to obtain alcoholized epoxy resin;

[0048] (2) Mix the alcoholized epoxy resin obtained in step (1) with ethanolamine, and react at 80°C for 30 min to obtain aminated epoxy resin;

[0049] (3) Mix the aminated epoxy resin obtained in step (2) with acetic acid, react at 50°C for 30 min, add deionized water, and continue stirring at 50°C for 1 h to obtain the sizing agent for carbon fiber.

[0050] Example 2

[0051] This embodiment provides a carbon fiber sizing agent and a preparation method thereof. The raw materials for preparing the carbon fiber sizing agent include, by weight: 120 parts of epoxy resin, 100 parts of polyurethane-modified epoxy resin, 100 parts of polyethylene glycol, 2 parts of pyrrolidone, 0.4 part of triphenylphosphine, 8 parts of ethanolamine, 6 parts of acetic acid, and 480 parts of demineralized water.

[0052] The preparation method includes:

[0053] (1) Mix epoxy resin, polyurethane-modified epoxy resin, polyethylene glycol, pyrrolidone, and triphenylphosphine, and react at 110 °C for 10 h to obtain alcoholized epoxy resin;

[0054] (2) Mix the alcoholized epoxy resin obtained in step (1) with ethanolamine, and react at 100 °C for 30 min to obtain aminated epoxy resin;

[0055] (3) Mix the aminated epoxy resin obtained in step (2) with acetic acid, react at 40 °C for 30 min, add demineralized water, and continue stirring at 40 °C for 2 h to obtain the carbon fiber sizing agent.

[0056] Example 3

[0057] This embodiment provides a carbon fiber sizing agent and a preparation method thereof. The raw materials for preparing the carbon fiber sizing agent include, by weight: 100 parts of epoxy resin, 200 parts of polyurethane-modified epoxy resin, 100 parts of polyethylene glycol, 1 part of pyrrolidone, 0.4 part of triphenylphosphine, 8 parts of ethanolamine, 6 parts of acetic acid, and 623 parts of demineralized water.

[0058] The preparation method includes:

[0059] (1) Mix epoxy resin, polyurethane-modified epoxy resin, polyethylene glycol, pyrrolidone, and triphenylphosphine, and react at 110 °C for 10 h to obtain alcoholized epoxy resin;

[0060] (2) Mix the alcoholized epoxy resin obtained in step (1) with ethanolamine, and react at 100 °C for 30 min to obtain aminated epoxy resin;

[0061] (3) Mix the aminated epoxy resin obtained in step (2) with acetic acid, react at 40 °C for 30 min, add demineralized water, and continue stirring at 40 °C for 2 h to obtain the carbon fiber sizing agent.

[0062] Example 4

[0063] This embodiment provides a carbon fiber sizing agent and a preparation method thereof. The raw materials for preparing the carbon fiber sizing agent include, by weight: 100 parts of epoxy resin, 100 parts of polyurethane-modified epoxy resin, 100 parts of polyethylene glycol, 8 parts of pyrrolidone, 0.4 part of triphenylphosphine, 8 parts of ethanolamine, 6 parts of acetic acid, and 480 parts of demineralized water.

[0064] The preparation method includes:

[0065] (1) Mix epoxy resin, polyurethane-modified epoxy resin, polyethylene glycol, pyrrolidone, and triphenylphosphine, and react at 110°C for 10 h to obtain alcoholized epoxy resin;

[0066] (2) Mix the alcoholized epoxy resin obtained in step (1) with ethanolamine, and react at 100°C for 30 min to obtain aminated epoxy resin;

[0067] (3) Mix the aminated epoxy resin obtained in step (2) with acetic acid, react at 40°C for 30 min, add deionized water, and continue stirring at 40°C for 2 h to obtain the sizing agent for carbon fiber.

[0068] Comparative Example 1

[0069] This comparative example provides a sizing agent for carbon fiber. The manufacturer of the sizing agent for carbon fiber is Sanyo, and the grade is FS-6.

[0070] Perform performance tests on the sizing agents for carbon fiber provided in Examples 1-4 and Comparative Example 1. The specific method is as follows:

[0071] (1) Epoxy value, GB-T 1667-2008;

[0072] (2) pH value, pH meter;

[0073] (3) Freeze-thaw stability: Keep the sizing agent at -10°C ± 2°C for 18 h, then heat it up to 20°C ± 2°C

[0074] Keep it for 6 h, and repeat this cycle 5 times, then observe whether it layers.

[0075] (4) High-temperature stability: Keep the sizing agent at 60°C ± 2°C for 18 h, then cool it down to 20°C ± 2°C

[0076] Keep it for 6 h, and repeat this cycle 5 times, then observe whether it layers;

[0077] Prepare the obtained sizing agent for carbon fiber into an aqueous solution of about 2%. After surface treatment in the carbon fiber production process, immerse the carbon fiber in the sizing agent solution for 10 - 30 seconds, and then dry it to obtain a carbon fiber sample. The final sizing agent content on the carbon fiber surface is about 0.5 - 1%. Perform performance tests on the treated carbon fiber. The test methods are as follows:

[0078] (5) Tensile strength and elongation at break, GB / T 3362;

[0079] (6) Elastic modulus, GB / T 3362;

[0080] (7) Linear density, GB / T 3362;

[0081] (8) Resistivity, GB / T 32993;

[0082] (9) Tow width:

[0083] Select about 1 m of neat carbon fiber without hairiness and damage; lay the carbon fiber flat on the recording paper, dip your finger in the printing ink, press it on the carbon fiber from top, middle and bottom, leaving three complete parallel marks from left to right on the recording paper; use a digital caliper after zero adjustment to measure the distance of the blank part in the mark, which is the tow width, accurate to 0.01 mm, and take the average of three measurements as the tow width of the carbon fiber on this axis;

[0084] (10) Sag verticality:

[0085] Pull out a section of carbon fiber tow from the bobbin and cut an effective length of 40 cm; calibration: vertically fix one end of the carbon fiber and hang a 100 g weight at the other end, and let it stand for 30 min under the measured temperature and humidity conditions to correct the bending and twisting of the carbon fiber tow; horizontal fixation: remove the load weight 3, fix it on the horizontal rectangular base 4, fix it with the fixing belt 6, and use a ruler to measure and ensure that the horizontal distance between the end of the carbon fiber tow 5 and the base is 25 cm; let the carbon fiber tow 5 hang naturally, and at the same time press the stopwatch. After 2 min, measure the horizontal distance L, accurate to 0.1 cm, and repeat the test for 3 samples; take the average of the above 3 values to obtain the sag value L of the carbon fiber;

[0086] (11) Hairiness amount:

[0087] Take one axis of the carbon fiber to be tested and take 50 m from this axis of wire; take a square sponge with a length of 6 cm and a width of 3 cm and weigh it, denoted as m1; clamp the sample fiber in the middle of the cut sponge, place a 250 g press block above the sponge, and apply a load of 2.5 N; continuously and uniformly make the 50 m fiber pass through the middle of the sponge medium; weigh the sponge with hairiness left, denoted as m2; calculation: the calculation formula for the hairiness amount: m = m2 - m1, where: m is the hairiness amount of the carbon fiber; m1 is the mass of the carbon fiber before the test; m2 is the mass of the carbon fiber after the test;

[0088] (12) Interlaminar shear, ASTM D 2344.

[0089] Perform performance tests on the sizing agents of the carbon fibers provided in Examples 1-4 and Comparative Example 1. The test results are shown in Table 1. Perform performance tests on the treated carbon fibers, and the results are shown in Tables 2-3:

[0090] Table 1

[0091]

[0092]

[0093] Table 2

[0094]

[0095] Table 3

[0096]

[0097]

[0098] Due to the insufficient product stability of Example 3 and Example 4, subsequent experiments could not be carried out, and there is no corresponding carbon fiber experimental data.

[0099] As can be seen from Tables 1-3, the performance indicators of the carbon fiber sizing agent provided by this patent reach the level of imported sizing agents. Some results are even slightly better than those of imported sizing agents, and all indicators are significantly better than domestic sizing agents.

[0100] The applicant declares that the present invention uses the above embodiments to illustrate a carbon fiber sizing agent and its preparation method and application, but the present invention is not limited to the above embodiments, that is, it does not mean that the present invention must rely on the above embodiments to be implemented. Those skilled in the art should understand that any improvement to the present invention, the equivalent replacement of each raw material of the product of the present invention, the addition of auxiliary components, and the selection of specific methods, etc., all fall within the protection scope and the disclosure scope of the present invention.

Claims

1. A carbon fiber sizing agent, characterized in that, The raw materials for preparing the carbon fiber sizing agent include, by weight, 100-150 parts of epoxy resin, 100-150 parts of polyurethane-modified epoxy resin, 100-150 parts of polyethylene glycol, 1-2 parts of organic solvent, 0.2-0.5 parts of catalyst, 5-10 parts of alcoholamine compound, 5-15 parts of acidic pH regulator and 300-500 parts of water.

2. The sizing agent for carbon fiber according to claim 1, wherein The catalyst includes triphenylphosphine; Preferably, the alcoholamine compound includes any one of ethanolamine, diethanolamine or triethanolamine, or a combination of at least two thereof; Preferably, the acidic pH adjuster includes any one of acetic acid, dilute hydrochloric acid, dilute sulfuric acid or dilute nitric acid, or a combination of at least two thereof.

3. The sizing agent for carbon fiber according to claim 1 or 2, characterized in that, The number average molecular weight of the epoxy resin is 300-1000.

4. The sizing agent for carbon fiber according to any one of claims 1-3, characterized in that, The number average molecular weight of the polyethylene glycol is 2000-8000; Preferably, the organic solvent comprises any one of acetone, xylene or pyrrolidone, or a combination of at least two thereof; Preferably, the water comprises desalinated water.

5. A method for preparing the carbon fiber sizing agent according to any one of claims 1 to 4, characterized in that: The preparation method comprises: (1) mixing an epoxy resin, a polyurethane-modified epoxy resin, polyethylene glycol, an organic solvent, and a catalyst, and reacting the mixture to obtain an alcoholized epoxy resin; (2) mixing the alcoholized epoxy resin obtained in step (1) with an alcohol amination, and reacting the mixture to obtain an aminated epoxy resin; (3) mixing the aminated epoxy resin obtained in step (2) with an acidic pH regulator, reacting the mixture, and then adding water and mixing the mixture evenly to obtain the carbon fiber sizing agent.

6. The preparation method according to claim 5, characterized in that The reaction in step (1) is carried out under stirring; Preferably, the stirring speed in step (1) is 10-200 rpm; Preferably, the reaction temperature in step (1) is 100-150°C; Preferably, the reaction time in step (1) is 8-12 hours.

7. The preparation method according to claim 5 or 6, characterized in that The reaction temperature in step (2) is 80-100° C. Preferably, the reaction time in step (2) is 20-40 min.

8. The preparation method according to any one of claims 5 to 7, characterized in that, The reaction temperature in step (3) is 30-50°C; Preferably, the reaction time in step (3) is 1-3 hours.

9. The preparation method according to any one of claims 5-8, characterized in that, The mixing in step (3) is carried out under stirring conditions; Preferably, the stirring temperature in step (3) is 30-50°C; Preferably, the stirring time in step (3) is 1-3h; Preferably, the stirring speed in step (3) is 300-1500 rpm.

10. Use of the carbon fiber sizing agent according to any one of claims 1 to 4 in carbon fiber or graphite fiber.

Images