A method for preparing a carbon fiber sizing agent containing multi-walled carbon nanotubes and a carbon fiber

Abstract

The application provides a preparation method of a carbon fiber sizing agent containing multi-walled carbon nanotubes and a carbon fiber, and belongs to the technical field of carbon fiber manufacturing. The preparation method of the carbon fiber sizing agent containing multi-walled carbon nanotubes comprises the following steps: placing multi-walled carbon nanotubes in an inert atmosphere for heat treatment, wherein the temperature of the heat treatment is 2000-3000 DEG C, and the treatment time is 1-6 h; mixing the multi-walled carbon nanotubes after the heat treatment, a sizing agent resin matrix and a surfactant solution for mixing treatment, wherein the mixing treatment is sequentially carried out under the conditions of ultrasonic and mechanical stirring to obtain the carbon fiber sizing agent containing multi-walled carbon nanotubes, and the preparation method can improve the problem that the multi-walled carbon nanotubes are prone to agglomeration in the carbon fiber sizing agent to a certain extent.

Description

Technical Field

[0001] This application relates to the field of carbon fiber manufacturing technology, and more specifically, to a method for preparing a carbon fiber sizing agent containing multi-walled carbon nanotubes and carbon fiber. Background Technology

[0002] Carbon fiber, with its superior properties such as high strength, high modulus, and low density, is widely used in aerospace, sporting goods, and automobile manufacturing. Among these applications, sizing agents are key additives in the carbon fiber production process, serving to protect the carbon fiber surface and improve the interfacial bonding between the carbon fiber and the matrix resin.

[0003] Based on this, multi-walled carbon nanotubes possess a unique one-dimensional nanostructure and excellent mechanical, electrical, and thermal properties. Technicians have discovered that adding multi-walled carbon nanotubes to carbon fiber sizing agents to modify carbon fibers, after the corresponding carbon fibers are combined with the resin matrix, is expected to further improve the mechanical, electrical, and thermal properties of carbon fiber resin composites.

[0004] However, multi-walled carbon nanotubes tend to agglomerate in carbon fiber sizing agents. Unevenly dispersed multi-walled carbon nanotubes not only fail to perform their modifying function, but may also form defects in carbon fiber resin composites (such as reducing the interfacial bonding strength between carbon fibers and the resin matrix), resulting in poor performance of the composite material. Summary of the Invention

[0005] The purpose of this application is to provide a method for preparing a carbon fiber sizing agent containing multi-walled carbon nanotubes and a carbon fiber, which can improve the problem of easy agglomeration of multi-walled carbon nanotubes in carbon fiber sizing agents to a certain extent.

[0006] The embodiments of this application are implemented as follows:

[0007] In a first aspect, embodiments of this application provide a method for preparing a carbon fiber sizing agent containing multi-walled carbon nanotubes, comprising the following steps: placing multi-walled carbon nanotubes under an inert atmosphere for heat treatment, wherein the heat treatment temperature is 2000-3000℃ and the treatment time is 1-6h; mixing the heat-treated multi-walled carbon nanotubes, the sizing agent resin matrix, and the surfactant solution, wherein the mixing step is carried out sequentially under ultrasonic and mechanical stirring conditions to obtain a carbon fiber sizing agent containing multi-walled carbon nanotubes.

[0008] In existing technologies, the main reason why multi-walled carbon nanotubes (MWC nanotubes) tend to agglomerate in carbon fiber sizing agents is believed to be the high specific surface area of ​​the MBCs themselves and the strong van der Waals forces between them. A common improvement method is to use ultrasonic and mechanical stirring sequentially in a surfactant solution for assisted dispersion; however, practical results have shown that this dispersion method is also difficult to achieve uniform dispersion of MBCs. The inventors discovered through research that MBCs contain some impurities, including but not limited to metal catalysts introduced during the MBC preparation process, moisture, and incompletely converted single-walled components. The presence of these impurities is also one of the reasons why MBCs tend to agglomerate in carbon fiber sizing agents. Based on this, in this application, before mixing the multi-walled carbon nanotubes, the sizing agent resin matrix, and the surfactant solution, the multi-walled carbon nanotubes are first heat-treated at 2000–3000°C for 1–6 hours under an inert atmosphere. On the one hand, the high-temperature treatment can remove impurities such as residual metal catalysts and moisture from the multi-walled carbon nanotubes, thereby improving their purity. On the other hand, the high-temperature treatment can deeply repair lattice defects in the multi-walled carbon nanotubes (such as 5-membered or 7-membered ring distortion), thereby promoting multi-layer wall reconstruction and inducing single-layer walls to form multi-layer structures through carbon atom rearrangement (even transforming the residual single-wall structure in the multi-walled carbon nanotubes into a multi-wall structure, which is equivalent to improving the purity of the multi-walled carbon nanotubes). Through the combined effect of these two aspects, the purity of the multi-walled carbon nanotubes can be improved, thereby effectively improving the problem of easy aggregation of multi-walled carbon nanotubes due to the presence of impurities. Meanwhile, the surfactant solution is subsequently mixed using a combination of ultrasonic and mechanical stirring to ensure that a carbon fiber sizing agent with relatively uniform dispersion of multi-walled carbon nanotubes is finally prepared.

[0009] In some optional embodiments, the heat treatment temperature is 2550–3000°C; the heat treatment step is carried out in a graphite furnace with a real-time temperature of T, and during the heating process, the heating rate is C1 when T ≤ 1500°C, C2 when 1500°C < T ≤ 2500°C, and C3 when 2500°C < T ≤ 3000°C, wherein C1 > C2 > C3.

[0010] In the above technical solution, when the temperature range of heat treatment is within the range of 2550 to 3000℃, the heating rate is set according to different temperature ranges. Specifically, the higher the temperature, the smaller the heating rate, which helps to better balance the structural stability of multi-walled carbon nanotubes at high temperatures and the impurity removal effect.

[0011] In some alternative implementations, the difference in heating rate between any two adjacent C1, C2 and C3 is 5 to 6 °C / min; alternatively, C1 is 15 to 18 °C / min.

[0012] In the above technical solution, the difference in heating rate between any two adjacent C1, C2 and C3 is limited to the above range, and C1 is limited to the above range, so that each heating stage has a more suitable heating rate, thereby better balancing the structural stability and impurity removal effect of multi-walled carbon nanotubes at high temperatures.

[0013] In some alternative embodiments, the step of mixing the heat-treated multi-walled carbon nanotubes, the sizing agent resin matrix, and the surfactant solution includes: firstly, mixing the heat-treated multi-walled carbon nanotubes and the surfactant solution in a first mixing process, wherein the first mixing process is carried out sequentially under ultrasonic and mechanical stirring conditions to obtain a dispersion; and then mixing the dispersion and the sizing agent resin matrix in a second mixing process.

[0014] In the above technical solution, the step of mixing multi-walled carbon nanotubes, sizing agent resin matrix and surfactant solution is carried out by a step-by-step mixing method, which can make the multi-walled carbon nanotubes in the prepared carbon fiber sizing agent more uniformly distributed.

[0015] In some alternative implementations, the ultrasonic power is 200–600 W and the ultrasonic treatment time is 30–60 min in the first mixing step.

[0016] In the above technical solution, limiting the ultrasonic power and processing time to the above ranges helps to better disperse multi-walled carbon nanotubes in surfactant solutions.

[0017] In some alternative implementations, during the first mixing step, the mechanical stirring speed is 500–1500 rpm, and the mechanical stirring time is 2–4 hours.

[0018] In the above technical solution, limiting the rotation speed and processing time of mechanical stirring to the above ranges helps to better disperse multi-walled carbon nanotubes in surfactant solutions.

[0019] In some alternative embodiments, the step of mixing the heat-treated multi-walled carbon nanotubes, the sizing agent resin matrix, and the surfactant solution includes:

[0020] The amount of multi-walled carbon nanotubes added is 0.1 to 5 parts by weight, the amount of sizing agent resin matrix added is 10 to 40 parts, and the amount of surfactant solution added is 50.5 to 100 parts.

[0021] In the above technical solution, multi-walled carbon nanotubes, sizing agent resin matrix and surfactant solution are mixed according to the above mass proportions, which can take into account both the dispersion effect of each component and the modification effect on carbon fiber.

[0022] In some alternative embodiments, the surfactant solution comprises 0.5 to 10 parts of surfactant and 50 to 90 parts of solvent.

[0023] In the above technical solution, the surfactant and solvent in the surface modifier solution are mixed according to the above mass proportions so that the surfactant solution has a surfactant with a suitable mass ratio, which helps to disperse the various components better.

[0024] In some alternative embodiments, the preparation method satisfies at least one of the following conditions A to C:

[0025] The sizing agent resin matrix is ​​selected from at least one of epoxy resin and polyurethane.

[0026] Surfactant B is selected from at least one of sodium dodecylbenzenesulfonate and Tween-80.

[0027] Solvent C is selected from at least one of deionized water and ethanol.

[0028] In the above technical solution, the types of sizing agent matrix, surfactant and solvent are limited to the above range so that each component can be better dispersed.

[0029] Secondly, embodiments of this application provide a carbon fiber, including a carbon fiber matrix and a modified coating located on the surface of the carbon fiber matrix. The modified coating is formed by applying a carbon fiber sizing agent as provided in the first aspect embodiment and then curing it.

[0030] In the above technical solution, the surface of the carbon fiber has a modified coating formed by curing the carbon fiber sizing agent provided in the first aspect embodiment. Since the multi-walled carbon nanotubes in the modified coating are uniformly distributed on the surface of the carbon fiber, when the corresponding carbon fiber is combined with the resin matrix, the mechanical properties, electrical properties and thermal properties of the carbon fiber resin composite material can be improved, and the interface bonding strength between the carbon fiber and the resin matrix can also be made better. Attached Figure Description

[0031] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of this application and should not be regarded as a limitation of the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0032] Figure 1 A process flow diagram of a method for preparing a carbon fiber sizing agent containing multi-walled carbon nanotubes provided in this application embodiment;

[0033] Figure 2 This is a distribution diagram of multi-walled carbon nanotubes on the surface of carbon fibers in Example 1 of this application;

[0034] Figure 3 This is a distribution diagram of multi-walled carbon nanotubes on the surface of carbon fibers in Example 2 of this application;

[0035] Figure 4 This is a distribution diagram of multi-walled carbon nanotubes on the surface of carbon fibers in Comparative Example 1 of this application;

[0036] Figure 5 This is a distribution diagram of multi-walled carbon nanotubes on the surface of carbon fibers in Comparative Example 3 of this application. Detailed Implementation

[0037] 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.

[0038] It should be noted that the terms "and / or" in this application, such as "feature 1 and / or feature 2", all refer to the three cases of "feature 1" alone, "feature 2" alone, and "feature 1" plus "feature 2".

[0039] In addition, in the description of this application, unless otherwise stated, "one or more" means two or more; the range of "numerical value a to numerical value b" includes the two endpoints "a" and "b"; and "unit of measurement" in "numerical value a to numerical value b + unit of measurement" represents the "unit of measurement" of both "numerical value a" and "numerical value b".

[0040] In existing technologies, the main reason why multi-walled carbon nanotubes (MWCNTs) tend to agglomerate in carbon fiber sizing agents is believed to be the high specific surface area of ​​the MCCNTs themselves and the strong van der Waals forces between them. A common improvement method is to use ultrasonic and mechanical stirring sequentially in the surfactant solution for assisted dispersion; however, practical results have shown that this dispersion method is also difficult to achieve uniform dispersion of MCCNTs.

[0041] Through research, the inventors discovered that multi-walled carbon nanotubes contain some impurities, including but not limited to metal catalysts, moisture, and incompletely converted single-walled components introduced during the preparation of multi-walled carbon nanotubes. The presence of these impurities is one of the reasons why multi-walled carbon nanotubes are prone to agglomeration in carbon fiber sizing agents.

[0042] Based on this, the inventors further heat-treated the multi-walled carbon nanotubes before mixing, and found that this could effectively improve the problem of multi-walled carbon nanotubes being prone to agglomeration due to the presence of impurities. At the same time, the inventors then used ultrasonic and mechanical stirring in the surfactant solution to mix the nanotubes, and found that a carbon fiber sizing agent with relatively uniform dispersion of multi-walled carbon nanotubes could be prepared.

[0043] The following describes in detail the preparation method of the carbon fiber sizing agent containing multi-walled carbon nanotubes and the carbon fiber according to the embodiments of this application.

[0044] In a first aspect, embodiments of this application provide a method for preparing a carbon fiber sizing agent containing multi-walled carbon nanotubes, comprising the following steps: placing the multi-walled carbon nanotubes under an inert atmosphere for heat treatment, wherein the heat treatment temperature is 2000–3000°C (e.g., but not limited to, any one of 2000°C, 2100°C, 2200°C, 2300°C, 2400°C, 2500°C, 2600°C, 2700°C, 2800°C, 2900°C, and 3000°C, or any combination thereof). The range of values), the treatment time is 1 to 6 hours (for example, but not limited to any one of the treatment times of 1 hour, 2 hours, 3 hours, 4 hours, 5 hours and 6 hours or any range between two); the heat-treated multi-walled carbon nanotubes, the sizing agent resin matrix and the surfactant solution are mixed, wherein the mixing step is carried out sequentially under ultrasonic and mechanical stirring conditions (i.e., ultrasonic mixing is used first, and then mechanical stirring is used for mixing), to obtain a carbon fiber sizing agent containing multi-walled carbon nanotubes.

[0045] In this application, before mixing multi-walled carbon nanotubes (MWCNTs), the sizing agent resin matrix, and the surfactant solution, the MWCNTs are first heat-treated at 2000–3000°C for 1–6 hours under an inert atmosphere. On one hand, the high-temperature treatment removes residual metal catalysts and moisture from the MWCNTs, thereby improving their purity. On the other hand, the high-temperature treatment deeply repairs lattice defects in the MWCNTs (such as 5-membered or 7-membered ring distortion), promoting multilayer wall reconstruction and inducing single-layer walls to form multilayer structures through carbon atom rearrangement (even converting residual single-wall structures in the MWCNTs into multi-wall structures, effectively improving their purity). Through the combined effect of these two aspects, the purity of the MWCNTs is improved, effectively mitigating the problem of MWCNTs easily agglomerating due to impurities. Simultaneously, the surfactant solution is subsequently mixed using a combination of ultrasonic and mechanical stirring to ensure that a carbon fiber sizing agent with relatively uniform dispersion of MWCNTs is ultimately prepared.

[0046] It should be noted that the type of inert atmosphere is not limited, for example, it can be at least one of nitrogen and argon.

[0047] As an example, the heat treatment temperature is 2550–3000℃; the heat treatment steps are carried out in a graphite furnace, the real-time temperature of the graphite furnace is T, and during the heating process, when T≤1500℃, the heating rate is C1, when 1500℃<T≤2500℃, the heating rate is C2, and when 2500℃<T≤3000℃, the heating rate is C3, where C1>C2>C3.

[0048] In this embodiment, when the temperature range of heat treatment is within the range of 2550 to 3000°C, the heating rate is set according to different temperature ranges. Specifically, the higher the temperature, the smaller the heating rate, which helps to better balance the structural stability of multi-walled carbon nanotubes at high temperatures and the impurity removal effect.

[0049] As an example, in C1, C2, and C3, the difference in heating rate between any two adjacent values ​​is 5 to 6 °C / min, for example, but not limited to, any one of the following values ​​or a range between any two: 56 °C / min, 5.1 °C / min, 5.2 °C / min, 5.3 °C / min, 5.4 °C / min, 5.5 °C / min, 5.6 °C / min, 5.7 °C / min, 5.8 °C / min, 5.9 °C / min, and 6 °C / min; and C1 is 15 to 18 °C / min, for example, but not limited to, any one of the following values ​​or a range between any two: 15 °C / min, 16 °C / min, 17 °C / min, and 18 °C / min.

[0050] In this embodiment, the difference in heating rate between any two adjacent C1, C2 and C3 is limited to the above range, and C1 is limited to the above range, so that each heating stage has a more suitable heating rate, thereby better balancing the structural stability and impurity removal effect of multi-walled carbon nanotubes at high temperatures.

[0051] In other possible implementations, the same heating rate may be used for all heating stages.

[0052] As an example, the steps of mixing heat-treated multi-walled carbon nanotubes, sizing agent resin matrix, and surfactant solution include: firstly, mixing the heat-treated multi-walled carbon nanotubes and surfactant solution for the first time, wherein the first mixing step is carried out sequentially under ultrasonic and mechanical stirring conditions to obtain a dispersion; and then mixing the dispersion and sizing agent resin matrix for the second time.

[0053] In this embodiment, the step of mixing multi-walled carbon nanotubes, sizing agent resin matrix and surfactant solution is carried out by a step-by-step mixing method, which can make the multi-walled carbon nanotubes in the prepared carbon fiber sizing agent more uniformly distributed.

[0054] In other possible implementations, a one-step mixed processing method may also be used.

[0055] As an example, in the first mixing step, the ultrasonic power is 200 to 600 W, for example, but not limited to any one of 200 W, 300 W, 400 W, 500 W and 600 W or any range between two; the ultrasonic treatment time is 30 to 60 min, for example, but not limited to any one of 30 min, 40 min, 50 min and 60 min or any range between two.

[0056] In this embodiment, limiting the ultrasonic power and processing time to the above ranges helps to better disperse multi-walled carbon nanotubes in the surfactant solution.

[0057] As an example, in the first mixing step, the mechanical stirring speed is 500 to 1500 rpm, for example, but not limited to any one of 500 rpm, 800 rpm, 1000 rpm, 1200 rpm, 1500 rpm, or any range between two; the mechanical stirring time is 2 to 4 hours, for example, but not limited to any one of 2 hours, 2.5 hours, 3 hours, 3.5 hours, and 4 hours, or any range between two.

[0058] In this embodiment, limiting the mechanical stirring speed and processing time to the above ranges helps to better disperse multi-walled carbon nanotubes in the surfactant solution.

[0059] It should be noted that the second mixing process can be performed by mechanical stirring only (since the multi-walled carbon nanotubes are already uniformly dispersed, ultrasonication is not required for the second mixing process), or it can be performed by referring to the steps of the first mixing process.

[0060] As an example, in the step of mixing heat-treated multi-walled carbon nanotubes, sizing agent resin matrix and surfactant solution: the amount of multi-walled carbon nanotubes added is 0.1 to 5 parts by mass, the amount of sizing agent resin matrix added is 10 to 40 parts, and the amount of surfactant solution added is 50.5 to 100 parts.

[0061] In this embodiment, multi-walled carbon nanotubes, sizing agent resin matrix, and surfactant solution are mixed in the above-mentioned mass proportions, which can take into account both the dispersion effect of each component and the modification effect on carbon fiber.

[0062] As an example, the surfactant solution comprises 0.5 to 10 parts surfactant and 50 to 90 parts solvent.

[0063] In this embodiment, the surfactant and solvent in the surface modifier solution are mixed according to the above-mentioned mass proportions so that the surfactant solution has a surfactant with a suitable mass ratio, thereby helping the various components to be better dispersed.

[0064] As an example, the preparation method satisfies at least one of the following conditions A to C:

[0065] The sizing agent resin matrix is ​​selected from at least one of epoxy resin and polyurethane.

[0066] Surfactant B is selected from at least one of sodium dodecylbenzenesulfonate and Tween-80.

[0067] Solvent C is selected from at least one of deionized water and ethanol.

[0068] In this embodiment, the types of sizing agent matrix, surfactant and solvent are limited to the above ranges so that each component can be better dispersed.

[0069] It should be noted that, for the preparation of carbon fiber sizing agents containing multi-walled carbon nanotubes, any processes or steps not specifically described or limited can be set according to conventional methods in this field.

[0070] As an example, after the second mixing treatment of the dispersion and the sizing agent resin matrix is ​​completed, the mixture is further filtered using a 0.4 μm microporous membrane.

[0071] As an example, a process flow diagram of the preparation method of carbon fiber sizing agent containing multi-walled carbon nanotubes is exemplarily provided. Figure 1 .

[0072] Secondly, embodiments of this application provide a carbon fiber, including a carbon fiber matrix and a modified coating located on the surface of the carbon fiber matrix. The modified coating is formed by applying a carbon fiber sizing agent as provided in the first aspect embodiment and then curing it.

[0073] In this application, the surface of the carbon fiber has a modified coating formed by curing the carbon fiber sizing agent provided in the first aspect embodiment. Since the multi-walled carbon nanotubes in the modified coating are uniformly distributed on the surface of the carbon fiber, when the corresponding carbon fiber is combined with the resin matrix, the mechanical properties, electrical properties and thermal properties of the carbon fiber resin composite material can be improved, and the interface bonding strength between the carbon fiber and the resin matrix can also be made better.

[0074] It should be noted that the preparation process of carbon fiber can be carried out in accordance with conventional processes in this field, and will not be described in detail in this application.

[0075] The features and performance of this application will be further described in detail below with reference to the embodiments.

[0076] Example 1

[0077] This application provides a method for preparing carbon fiber, including the following steps:

[0078] Preparation of S1 carbon fiber sizing agent containing multi-walled carbon nanotubes:

[0079] Multi-walled carbon nanotubes were placed in a graphite furnace under a nitrogen atmosphere and heat-treated at 2400℃ for 4 hours. The heating program was as follows: 15℃ / min from room temperature to 1500℃ and 10℃ / min from 1500℃ to 2400℃.

[0080] 0.5 parts of heat-treated multi-walled carbon nanotubes were added to 72 parts of surface modifier solvent (2 parts of sodium dodecylbenzenesulfonate were added to 70 parts of deionized water and stirred). The mixture was then ultrasonically dispersed at an ultrasonic power of 300W for 0.75h, and then mechanically stirred at a stirring speed of 800rpm for 3h to obtain a dispersion.

[0081] The above dispersion of 72.5 parts and 27.5 parts of epoxy resin (sizing agent resin matrix) was mechanically stirred and dispersed at a stirring speed of 800 rpm for 3 hours; then the mixture was filtered through a 0.4 μm microporous membrane, and the filtrate was collected to obtain a carbon fiber sizing agent containing multi-walled carbon nanotubes.

[0082] Preparation of S2 carbon fiber

[0083] The sizing agent from step S1 is applied to the surface of the carbon fiber matrix (polyacrylonitrile carbon fiber matrix) and then dried at 80°C for 1 hour to obtain carbon fiber with a modified coating.

[0084] Example 2

[0085] This application provides a method for preparing carbon fiber, including the following steps:

[0086] Preparation of S1 carbon fiber sizing agent containing multi-walled carbon nanotubes:

[0087] Multi-walled carbon nanotubes were placed in a graphite furnace under a nitrogen atmosphere and heat-treated at 2800℃ for 2 hours. The heating program was as follows: 15℃ / min from room temperature to 1500℃, 10℃ / min from 1500℃ to 2500℃, and 5℃ / min from 2500℃ to 2800℃.

[0088] One part of heat-treated multi-walled carbon nanotubes was added to 63 parts of surface modifier solvent (3 parts of Tween-80 were added to 60 parts of ethanol and stirred). The mixture was then ultrasonically dispersed at an ultrasonic power of 400W for 50 minutes, and then mechanically stirred at a stirring speed of 1000rpm for 2.5 hours to obtain a dispersion.

[0089] The above dispersion of 64 parts and 36 parts of polyurethane (sizing agent resin matrix) was mechanically stirred and dispersed at a stirring speed of 800 rpm for 3 hours; then the mixture was filtered through a 0.4 μm microporous membrane, and the filtrate was collected to obtain a carbon fiber sizing agent containing multi-walled carbon nanotubes.

[0090] Preparation of S2 carbon fiber

[0091] The sizing agent from step S1 is applied to the surface of the carbon fiber matrix (polyacrylonitrile carbon fiber matrix) and then dried at 80°C for 1 hour to obtain carbon fiber with a modified coating.

[0092] Comparative Example 1

[0093] This application provides a comparative example of a method for preparing carbon fiber, which differs from Example 1 only in that no heat treatment is performed in step S1.

[0094] Comparative Example 2

[0095] This application provides a comparative example of a method for preparing carbon fiber, which differs from Example 1 only in that the heat treatment temperature in step S1 is 1500°C.

[0096] Comparative Example 3

[0097] This application provides a comparative example of a method for preparing carbon fiber, which differs from Example 1 only in that: in step S1, 0.5 parts of heat-treated multi-walled carbon nanotubes are added to 72 parts of surface modifier solvent (2 parts of sodium dodecylbenzenesulfonate are added to 70 parts of deionized water and stirred), and then mechanically stirred and dispersed at a stirring speed of 800 rpm for 3.75 h to obtain a dispersion.

[0098] Test case

[0099] (1) Distribution of multi-walled carbon nanotubes on carbon fiber surface

[0100] Test method: The carbon fibers prepared in Examples 1-2 and Comparative Examples 1 and 3 were used as samples, and the distribution of multi-walled carbon nanotubes on the carbon fiber surface of each sample was observed using a scanning electron microscope.

[0101] See Figures 2-5 As can be seen, in Examples 1 and 2, the multi-walled carbon nanotubes on the carbon fiber surface were relatively dispersed and evenly distributed when prepared according to the preparation process provided in the embodiments of this application; while in Comparative Examples 1 and 3, since they were not prepared according to the preparation process provided in the embodiments of this application, the multi-walled carbon nanotubes on the carbon fiber surface were more concentrated and severely agglomerated.

[0102] (2) Interfacial bonding strength test of carbon fiber resin composite material

[0103] Test method: The carbon fibers prepared in Examples 1-2 and Comparative Examples 1-3 were used as samples. Each sample was then mixed with epoxy resin (E-31) at a mass ratio of 3:2. Carbon fiber resin composites were prepared by compression molding (temperature control was as follows: heat treatment at 85℃ for 2h, heat treatment at 130℃ for 2h, and heat treatment at 180℃ for 2h). The interlaminar shear strength between carbon fibers and resin matrix in each composite material was then tested, and the results are summarized in Table 1.

[0104] Table 1

[0105] Example 1 80 Example 2 79 Comparative Example 1 73 Comparative Example 2 69 Comparative Example 3 72

[0106] Referring to Table 1, the test results of Examples 1-2 and Comparative Examples 1-3 show that when carbon fibers are prepared according to the preparation process provided in the embodiments of this application, and the corresponding carbon fibers are combined with resin materials to form carbon fiber resin composite materials, the carbon fibers and resin in the composite materials have relatively excellent interfacial bonding strength. This result is consistent with... Figures 2-5 The distribution results of multi-walled carbon nanotubes on the carbon fiber surface are consistent.

[0107] The embodiments described above are some, but not all, of the embodiments of this application. The detailed description of the embodiments of this application is not intended to limit the scope of the claimed application, but merely to illustrate selected embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of this application without inventive effort are within the scope of protection of this application.

Claims

1. A method for preparing a carbon fiber sizing agent containing multi-walled carbon nanotubes, characterized in that, Includes the following steps: Multi-walled carbon nanotubes were subjected to heat treatment under an inert atmosphere, wherein the heat treatment temperature was 2550~3000℃ and the treatment time was 1~6 h. The heat-treated multi-walled carbon nanotubes, sizing agent resin matrix, and surfactant solution are mixed, wherein the mixing process is carried out sequentially under ultrasonic and mechanical stirring conditions to obtain a carbon fiber sizing agent containing multi-walled carbon nanotubes. In the step of mixing the heat-treated multi-walled carbon nanotubes, the sizing agent resin matrix, and the surfactant solution: the amount of multi-walled carbon nanotubes added is 0.1-5 parts by mass, the amount of the sizing agent resin matrix added is 10-40 parts, and the amount of the surfactant solution added is 50.5-100 parts; the surfactant solution includes: 0.5-10 parts of surfactant and 50-90 parts of solvent; The heat treatment step is carried out in a graphite furnace, the real-time temperature of which is T. During the heating process, when T≤1500℃, the heating rate is C1; when 1500℃<T≤2500℃, the heating rate is C2; and when 2500℃<T≤3000℃, the heating rate is C3, wherein C1>C2>C3.

2. The preparation method according to claim 1, characterized in that, In C1, C2, and C3, the difference in heating rate between any two adjacent pairs is 5~6℃ / min.

3. The preparation method according to claim 2, characterized in that, C1 is 15~18℃ / min.

4. The preparation method according to any one of claims 1 to 3, characterized in that, The step of mixing the heat-treated multi-walled carbon nanotubes, the sizing agent resin matrix, and the surfactant solution includes: The heat-treated multi-walled carbon nanotubes and surfactant solution are first mixed, and the first mixing process is carried out under ultrasonic and mechanical stirring conditions to obtain a dispersion. Then the dispersion and the sizing agent resin matrix are mixed a second time.

5. The preparation method according to claim 4, characterized in that, In the first mixing process, the ultrasonic power is 200-600 W and the ultrasonic treatment time is 30-60 min.

6. The preparation method according to claim 4, characterized in that, In the first mixing process, the mechanical stirring speed is 500~1500 rpm, and the mechanical stirring time is 2~4 h.

7. The preparation method according to claim 1, characterized in that, At least one of the following conditions A to C must be met: A. The sizing agent resin matrix is ​​selected from at least one of epoxy resin and polyurethane; B. The surfactant is selected from at least one of sodium dodecylbenzenesulfonate and Tween-80: C. The solvent is selected from at least one of deionized water and ethanol.

8. A carbon fiber, characterized in that, It includes a carbon fiber matrix and a modified coating on the surface of the carbon fiber matrix, the modified coating being formed by applying a carbon fiber sizing agent as described in any one of claims 1 to 7 and then curing it.

Images