Preparation method of modified carbon fiber and carbon fiber composite material

Abstract

The invention provides a preparation method of a modified carbon fiber and a carbon fiber composite material, and belongs to the technical field of carbon fiber manufacturing. The preparation method of the modified carbon fiber comprises the following steps: dispersing a resin matrix, inorganic nanoparticles and a coupling agent in an organic solvent to obtain a coating solution for modification, the inorganic nanoparticles comprising carbon nanoparticles; applying a coating solution for modification to the surface of the carbon fiber precursor, and then drying to remove the organic solvent to obtain a modified carbon fiber precursor with a coating on the surface; the modified carbon fiber precursor is subjected to carbonization treatment to obtain the nano-particle-containing modified carbon fiber, and the modified carbon fiber prepared by the method has the advantages of high strength and firm combination of the carbon nano-particles in the material.

Description

Technical Field

[0001] The present application relates to the technical field of carbon fiber manufacturing, and in particular to a method for preparing modified carbon fiber and carbon fiber composite materials. Background Art

[0002] Carbon fiber is widely used in the fields such as aerospace, sports equipment, automobile manufacturing with its excellent properties such as high strength, high modulus and low density. Wherein, adopting sizing agent to carry out sizing treatment to carbon fiber is a key step in the carbon fiber production process, and its effect is to protect the carbon fiber surface, improve the interface bonding performance of carbon fiber and matrix resin. On this basis, technical personnel have found that carbon nanoparticles (such as carbon nanotubes) have excellent mechanical properties, electrical properties and thermal properties etc., utilize it to modify carbon fiber, it is expected to further improve the intensity (such as tensile strength and elastic modulus) of carbon fiber, meanwhile, the load of carbon nanoparticles can increase the surface roughness of carbon fiber and increase the contact area between carbon fiber and resin, thus can also improve the interface bonding strength of carbon fiber and resin.

[0003] At present, the process of modifying carbon fibers using carbon nanoparticles is usually as follows: the surface of the carbon fibers (referring to the material after carbonization of the carbon fiber precursor rather than the carbon fiber precursor) is pretreated before sizing to increase the roughness of the carbon fiber surface and graft polar groups; the pretreated carbon fibers are then sizing with a sizing agent containing carbon nanoparticles, and carbon fibers modified with carbon nanoparticles are obtained after curing.

[0004] However, the carbon fibers produced by this process have problems such as poor strength and easy shedding of carbon nanoparticles, which in turn affects the performance of the carbon fiber resin composite material. Summary of the Invention

[0005] The purpose of the present application is to provide a method for preparing modified carbon fibers and carbon fiber composite materials. The modified carbon fibers prepared by this method have the advantages of higher strength and more reliable bonding of carbon nanoparticles in the material.

[0006] The embodiment of the present application is implemented as follows:

[0007] In a first aspect, an embodiment of the present application provides a method for preparing modified carbon fiber, comprising the following steps: dispersing a resin matrix, inorganic nanoparticles and a coupling agent in an organic solvent to obtain a coating solution for modification, wherein the inorganic nanoparticles include carbon nanoparticles; applying the coating solution for modification to the surface of the carbon fiber precursor, and then drying it to remove the organic solvent to obtain a modified carbon fiber precursor having a coating on the surface; and carbonizing the modified carbon fiber precursor to obtain a modified carbon fiber containing inorganic nanoparticles.

[0008] In the prior art, the process of modifying carbon fibers using carbon nanoparticles usually has the following problems: first, directly pre-treating the carbon fibers (referring to the material after carbonization treatment of carbon fiber precursors rather than carbon fiber precursors) (for example, liquid phase oxidation, i.e. immersing the carbon fibers in an oxidizing solution for surface modification) increases the surface roughness of the carbon fibers and grafts polar groups, but easily damages the structure of the carbon fibers, thereby resulting in lower strength of the carbon fibers; second, the carbon nanoparticles are dispersed in a sizing agent and then bonded to the carbon fiber surface after coating and curing treatment, wherein the carbon nanoparticles are mainly bonded to the material by physical adsorption, and the physical adsorption binding force is weak, resulting in the carbon nanoparticles being easily detached from the carbon fiber surface during subsequent processing, thereby making it difficult to effectively improve the strength of the carbon fibers, and also resulting in a problem of weak interface bonding after the modified carbon fibers are bonded to the resin matrix. In the present application, a coating solution containing a resin matrix, inorganic nanoparticles and a coupling agent is directly coated on the surface of a carbon fiber precursor (i.e., a carbon fiber precursor that has not yet been carbonized), and then subjected to a drying treatment and a carbonization treatment to obtain a modified carbon fiber containing inorganic nanoparticles, wherein the drying treatment is used to remove the organic solvent to obtain a modified carbon fiber precursor with a coating on the surface. Since the coating contains a coupling agent, the modified coating containing carbon nanoparticles can be firmly combined with the surface of the carbon fiber precursor; on this basis, the carbonization treatment can not only carbonize the carbon fiber precursor in the modified carbon fiber precursor, but also uniformly carbonize the non-carbon materials (resin matrix and coupling agent) in the entire modified coating to prepare In the modified carbon fiber made of all-carbon material, the carbon materials can be stably combined through π-π conjugation, so that the carbon nanoparticles in the prepared modified carbon fiber can be firmly combined with the surrounding carbon materials. At the same time, the modified coating and the inner core (formed after carbonization of carbon fiber precursor) can be firmly combined, thereby effectively improving the strength of the carbon fiber, and also enabling the modified carbon fiber to have a strong interface bonding force after combining with the resin matrix; furthermore, in the process of combining inorganic nanoparticles with carbon fiber, there is no need to pretreat the carbon fiber (referring to the material after carbonization treatment of carbon fiber precursor rather than carbon fiber precursor), which will not cause damage to the structure of the carbon fiber and also helps to improve the strength of the carbon fiber.

[0009] In some optional embodiments, the coating solution includes, by weight, 30 to 40 parts of a resin matrix, 1 to 10 parts of inorganic nanoparticles, 1 to 5 parts of a coupling agent, and 80 to 100 parts of an organic solvent.

[0010] In the above technical solution, the mass fraction of each component is limited to the above range so that each component has an appropriate dosage, thereby allowing each component to better exert its own effect; at the same time, the coating solution can also have an appropriate viscosity, thereby facilitating subsequent coating.

[0011] In some optional embodiments, in the modified carbon fiber precursor, the coating layer has a thickness of 1 to 2 μm.

[0012] In the above technical solution, the thickness of the coating is limited to the above range, so that the coating contains nanoparticles with a relatively appropriate mass ratio, thereby being able to better enhance the performance of the carbon fiber with the help of the nanoparticles.

[0013] In some optional embodiments, the inorganic nanoparticles further include silicon carbide nanoparticles; optionally, the mass ratio of silicon carbide nanoparticles to carbon nanoparticles is (2-6):1.

[0014] In the above technical solution, adding silicon carbide particles to inorganic nanoparticles can improve the high temperature resistance and oxidation resistance of carbon fiber, thereby enabling the modified carbon fiber to be used under more extreme conditions; further, the mass ratio of silicon carbide nanoparticles and carbon nanoparticles is limited to the above range so that the two have a more appropriate mass ratio, so that the performance of carbon fiber can be better improved with the help of silicon carbide nanoparticles and carbon nanoparticles.

[0015] In some optional embodiments, the diameter of the carbon fiber precursor is 8 to 10 μm, and the particle size of the inorganic nanoparticles is 10 to 100 nm; optionally, the carbon fiber precursor is selected from polyacrylonitrile fiber; optionally, the resin matrix is selected from at least one of phenolic resin, melamine-formaldehyde resin and epoxy resin; optionally, the coupling agent is selected from at least one of KH560, Z6040 and KBM403.

[0016] In the above technical solution, the diameter of the carbon fiber precursor and the particle size of the inorganic nanoparticles are simultaneously limited to the above range so that the two have a more appropriate size difference, thereby facilitating the stable bonding of the inorganic nanoparticles to the surface of the carbon fiber precursor; further, the carbon fiber precursor is selected from polyacrylonitrile fiber because the carbon fiber precursor of this material has the advantage of a wider range of applicability; further, the technical solution provided in this application has a wide variety of applicable resin matrices and coupling agents, which can provide more feasible implementation plans.

[0017] In some optional embodiments, before applying the modified coating solution to the surface of the carbon fiber precursor, the step of pretreating the carbon fiber precursor is also included to increase the surface roughness of the carbon fiber precursor and graft polar groups onto the surface.

[0018] In the above technical solution, a pretreatment step is added before applying the coating solution to the surface of the carbon fiber precursor to increase the surface roughness of the carbon fiber precursor and graft polar groups on the surface, which can increase the bonding strength between the modified coating and the surface of the carbon fiber precursor.

[0019] In some optional embodiments, the pretreatment step includes: immersing the carbon fiber precursor in a concentrated nitric acid solution under ultrasonic conditions for surface treatment.

[0020] In the above technical solution, liquid phase oxidation is used for pretreatment, which has the advantage of being easy to implement; at the same time, ultrasound is used for auxiliary treatment, which can improve the effect of pretreatment.

[0021] In some optional embodiments, in the pretreatment step, at least one of the following conditions A to D is met:

[0022] The temperature of concentrated nitric acid solution A is 55-65℃.

[0023] The mass concentration of concentrated nitric acid B is 60-70%.

[0024] C Ultrasonic frequency is 30~50kHz.

[0025] D processing time is 1 to 2 hours.

[0026] In the above technical solution, the temperature of the concentrated nitric acid solution, the mass concentration of the concentrated nitric acid, the ultrasonic frequency and the treatment time in the pretreatment step are respectively limited within the above ranges, which can achieve a better pretreatment effect, that is, the surface of the carbon fiber precursor can have an appropriate roughness and be grafted with an appropriate amount of polar groups.

[0027] In some optional embodiments, before the step of pretreating the carbon fiber precursor, the step of cleaning the carbon fiber precursor with an organic solution is also included to remove the oil agent on the surface of the carbon fiber precursor; optionally, the organic solution is selected from a mixed solution of ethanol and acetone; optionally, the volume ratio of ethanol and acetone is 1:1.

[0028] In the above technical solution, the carbon fiber precursor is cleaned with an organic solution before the pretreatment step, which can effectively remove the oil on the surface of the carbon fiber precursor, thereby improving the effect of subsequent pretreatment thereof; further, the organic solvent is a mixed solution of ethanol and acetone and the volume ratio of the two is limited to 1:1, which can more easily and thoroughly remove the oil on the surface of the carbon fiber precursor.

[0029] In a second aspect, an embodiment of the present application provides a method for preparing a carbon fiber resin composite material, wherein the modified carbon fiber provided in the embodiment of the first aspect is subjected to sizing and curing treatment, and then the cured modified carbon fiber is composited with a resin.

[0030] In the above technical scheme, the modified carbon fiber provided in the first embodiment is used as a substrate, and then a carbon fiber resin composite material is prepared through sizing treatment, curing treatment and composite process. Since the modified carbon fiber has the advantages of relatively excellent strength and the carbon nanoparticles are more firmly bound in the material, the prepared composite material has the advantages of relatively excellent strength and higher interface bonding strength between the carbon fiber and the resin matrix. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following is a brief introduction to the drawings required for use in the embodiments. It should be understood that the following drawings only show certain embodiments of the present application and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other relevant drawings can be obtained based on these drawings without creative work.

[0032] Figure 1 A process flow chart of a method for preparing modified carbon fiber provided in this application;

[0033] Figure 2 This is a cross-sectional view of the carbon fiber and resin in the composite material of Example 1 of the present application;

[0034] Figure 3 This is a cross-sectional view of the carbon fiber and resin in the composite material of Example 2 of the present application;

[0035] Figure 4 This is a cross-sectional view of the carbon fiber and resin in the composite material of Comparative Example 2 of this application. DETAILED DESCRIPTION

[0036] 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.

[0037] It should be noted that “and / or” in this application, such as “Feature 1 and / or Feature 2”, refers to three situations: “Feature 1” alone, “Feature 2” alone, or “Feature 1” plus “Feature 2”.

[0038] In addition, in the description of this application, unless otherwise specified, the meaning of "multiple" in "one or more" refers to two or more; the range of "value a to value b" includes the two end values "a" and "b", and the "unit of measurement" in "value a to value b+unit of measurement" represents the "unit of measurement" of both "value a" and "value b".

[0039] In the prior art, the process of modifying carbon fibers using carbon nanoparticles is usually as follows: first, the surface of the carbon fibers (referring to the material after carbonization of the carbon fiber precursor, not the carbon fiber precursor) is pretreated to increase the surface roughness of the carbon fibers and graft polar groups; then, the pretreated carbon fibers are sizing with a sizing agent containing carbon nanoparticles. This preparation process has the following problems:

[0040] (1) Direct pretreatment of carbon fibers (e.g., liquid-phase oxidation, where the carbon fibers are immersed in an oxidizing solution for surface modification) increases the surface roughness of the carbon fibers and grafts polar groups, but it can easily damage the structure of the carbon fibers, leading to lower structural strength of the carbon fibers.

[0041] (2) Carbon nanoparticles are dispersed in the sizing agent and then bonded to the surface of the carbon fiber after coating and curing. The carbon nanoparticles are mainly bonded to the material through physical adsorption. The physical adsorption binding force is weak, which causes the carbon nanoparticles to easily fall off from the carbon fiber surface during subsequent processing, making it difficult to effectively improve the strength of the carbon fiber. It also causes the problem of weak interface bonding after the modified carbon fiber is combined with the resin matrix.

[0042] Based on this, the inventors, after research, provided a new modified carbon fiber preparation process and found that the prepared modified carbon fiber has the advantages of higher strength and more reliable bonding of carbon nanoparticles in the material.

[0043] The following is a detailed description of the preparation methods of the modified carbon fibers and carbon fiber composite materials according to the embodiments of the present application.

[0044] In a first aspect, an embodiment of the present application provides a method for preparing modified carbon fiber, comprising the following steps: dispersing a resin matrix, inorganic nanoparticles and a coupling agent in an organic solvent to obtain a coating solution for modification, wherein the inorganic nanoparticles include carbon nanoparticles; applying the coating solution for modification to the surface of the carbon fiber precursor, and then drying it to remove the organic solvent to obtain a modified carbon fiber precursor having a coating on the surface; and carbonizing the modified carbon fiber precursor to obtain a modified carbon fiber containing inorganic nanoparticles.

[0045] In the present application, a coating solution containing a resin matrix, nanoparticles and a coupling agent is directly coated on the surface of a carbon fiber precursor (i.e., a carbon fiber precursor that has not yet been carbonized), and then subjected to a drying treatment and a carbonization treatment to obtain a modified carbon fiber containing inorganic nanoparticles, wherein the drying treatment is used to remove the organic solvent to obtain a modified carbon fiber precursor with a coating on the surface. Since the coating contains a coupling agent, the modified coating containing carbon nanoparticles can be firmly combined with the surface of the carbon fiber precursor; on this basis, the carbonization treatment can not only carbonize the carbon fiber precursor in the modified carbon fiber precursor, but also uniformly carbonize the non-carbon materials (resin matrix and coupling agent) in the entire modified coating to prepare The modified carbon fibers of all-carbon materials can be stably bonded to each other through π-π conjugation, so that the carbon nanoparticles in the prepared modified carbon fibers can be firmly bonded to the surrounding carbon materials. At the same time, the modified coating and the inner core (formed after carbonization of the carbon fiber precursor) can be firmly bonded, thereby effectively improving the strength of the carbon fibers, and also enabling the modified carbon fibers to have a strong interface bonding force after being combined with the resin matrix. Furthermore, in the process of combining inorganic nanoparticles with carbon fibers, there is no need to pretreat the carbon fibers (referring to the material after carbonization of the carbon fiber precursor rather than the carbon fiber precursor), which will not damage the structure of the carbon fibers and will also help to improve the strength of the carbon fibers.

[0046] It should be noted that in the present application, carbon nanoparticles are applied to the surface of carbon fiber precursor (i.e., carbon fiber precursor that has not yet been carbonized), and the modified carbon fiber precursor with coating will be carbonized later, and accordingly, the resin matrix and coupling agent in the coating will also be carbonized and converted into carbon material; whereas in the prior art, carbon nanoparticles are applied to the surface of carbon fiber (referring to the material after carbonization of carbon fiber precursor rather than carbon fiber precursor), and the subsequent carbonization will not be carried out but curing treatment, and accordingly, the non-carbon components in the coating will not be carbonized. It can be seen from this that the preparation process of the modified carbon fiber provided by the present application is quite different from the existing process, which can also reflect the progressiveness of the technical solution of the present application to a certain extent.

[0047] It should be noted that the coating objects of the modified coating solution and the sizing agent in this application are different. Specifically, the coating object of the modified coating solution is the carbon fiber precursor (i.e., the carbon fiber precursor that has not been carbonized), while the coating object of the sizing agent is the finished carbon fiber (obtained after carbonization of the carbon fiber precursor).

[0048] It should be noted that the dosage of various functional components in the coating solution is not limited and can be adaptively adjusted according to time requirements.

[0049] As an example, the coating solution includes, by weight, 30 to 40 parts of a resin matrix (for example, but not limited to, the resin matrix is 30, 32, 34, 36, 38 and 40 parts, or a range between any two parts), 1 to 10 parts of inorganic nanoparticles (for example, but not limited to, the nanoparticles are 1, 2, 4, 6, 8 and 10 parts, or a range between any two parts), 1 to 5 parts of a coupling agent (for example, but not limited to, the coupling agent is 1, 2, 3, 4 and 5 parts, or a range between any two parts), and 80 to 100 parts of an organic solvent (for example, but not limited to, the organic solvent is 80, 85, 90, 95 and 100 parts, or a range between any two parts).

[0050] As an example, the mass fraction of each component is limited to the above range so that each component has an appropriate dosage, and thus each component can better exert its own effect; at the same time, it can also make the coating solution have an appropriate viscosity, thereby facilitating subsequent coating.

[0051] As an example, in the modified carbon fiber precursor, the thickness of the coating is 1 to 2 μm, for example but not limited to any point value among 1 μm, 1.2 μm, 1.4 μm, 1.6 μm, 1.8 μm and 2.0 μm, or a range value between any two of them.

[0052] In this embodiment, the thickness of the coating is limited to the above range, so that the coating contains nanoparticles with a relatively suitable mass ratio, thereby being able to better enhance the performance of the carbon fiber with the help of the nanoparticles.

[0053] As an example, the inorganic nanoparticles also include silicon carbide nanoparticles.

[0054] In this embodiment, adding silicon carbide particles to the inorganic nanoparticles can improve the high temperature resistance and oxidation resistance of the carbon fibers, thereby enabling the modified carbon fibers to be used under relatively extreme conditions.

[0055] It should be noted that the mass ratio of silicon carbide nanoparticles to carbon nanoparticles is not limited and can be adaptively adjusted according to actual needs.

[0056] As an example, the mass ratio of silicon carbide nanoparticles to carbon nanoparticles is (2-6):1, such as but not limited to any one of 2:1, 3:1, 4:1, 5:1 and 6:1 or a range between any two of the mass ratios.

[0057] In this embodiment, the mass ratio of silicon carbide nanoparticles to carbon nanoparticles is limited to the above range so that the two have a more appropriate mass ratio, thereby better improving the performance of carbon fibers with the help of silicon carbide nanoparticles and carbon nanoparticles.

[0058] It is understandable that in order to better improve the comprehensive performance of carbon fibers, other functional components, such as graphite nanoparticles, can be added to the inorganic nanoparticles according to actual needs.

[0059] As an example, the diameter of the carbon fiber precursor is 8 to 10 μm (for example, but not limited to a diameter of 8 μm, 8.5 μm, 9 μm, 9.5 μm and 10 μm, or a range between any two of them), and the particle size of the inorganic nanoparticles is 10 to 100 nm (for example, but not limited to a particle size of 10 nm, 20 nm, 30 nm, 40 nm, 50 nm, 60 nm, 70 nm, 80 nm, 90 nm and 100 nm, or a range between any two of them). In this embodiment, the diameter of the carbon fiber precursor and the particle size of the inorganic nanoparticles are simultaneously limited to the above range so that the two have a more suitable size difference, thereby facilitating the stable bonding of the inorganic nanoparticles to the surface of the carbon fiber precursor.

[0060] It should be noted that the shape of the carbon nanoparticles is not limited. For example, they can be spherical, with the particle size being the diameter; or they can be long strips, with the particle size being the length.

[0061] As an example, the carbon nanoparticles are long carbon nanotubes, and their length dimension is the particle size.

[0062] It should be noted that the material of the carbon fiber precursor is not limited and can be adaptively adjusted according to actual needs.

[0063] As an example, the carbon fiber precursor is selected from polyacrylonitrile fiber, which is usually prepared from polyacrylonitrile through spinning technology.

[0064] In this embodiment, the carbon fiber precursor is polyacrylonitrile fiber because the carbon fiber precursor made of this material has the advantage of a wide range of applications.

[0065] It should be noted that the types of the resin matrix and the coupling agent are not limited and can be selected and arranged according to conventional methods in the art.

[0066] As an example, the resin matrix is selected from at least one of phenolic resin, melamine-formaldehyde resin and epoxy resin.

[0067] As an example, the coupling agent is selected from at least one of KH560, Z6040 and KBM403.

[0068] In this embodiment, the technical solution provided in this application has a wide variety of applicable resin matrices and coupling agents, and can provide a large number of feasible implementation plans.

[0069] As an example, before applying the modified coating solution to the surface of the carbon fiber precursor, the method further includes a step of pretreating the carbon fiber precursor to increase the surface roughness of the carbon fiber precursor and graft polar groups onto the surface.

[0070] In this embodiment, a pretreatment step is added before applying the coating solution to the surface of the carbon fiber precursor to increase the surface roughness of the carbon fiber precursor and graft polar groups on the surface, which can increase the bonding strength between the modified coating and the surface of the carbon fiber precursor.

[0071] It should be noted that the method used in the pretreatment step is not limited and can be set according to conventional selections in the field, for example, various means such as anodic oxidation, liquid phase oxidation, plasma treatment, and gas phase oxidation can be used.

[0072] As an example, the pretreatment step includes: immersing the carbon fiber precursor in a concentrated nitric acid solution under ultrasonic conditions for surface treatment.

[0073] In this embodiment, liquid phase oxidation is used for pretreatment, which has the advantage of being easy to implement; at the same time, ultrasound is used for auxiliary treatment to improve the effect of pretreatment.

[0074] As an example, in the preprocessing step, at least one of the following conditions A to D is satisfied:

[0075] The temperature of concentrated nitric acid solution A is 55-65°C, for example but not limited to any one of 55°C, 57°C, 60°C, 62°C and 65°C or a range between any two of them.

[0076] The mass concentration of concentrated nitric acid B is 60-70%, for example, but not limited to, any one of 60%, 62%, 64%, 66%, 68% and 70% or a range between any two of the mass concentrations.

[0077] C ultrasonic frequency is 30-50 kHz, for example but not limited to any one of 30%, 35%, 40%, 45% and 50% or a range between any two of the ultrasonic frequencies.

[0078] D The processing time is 1 to 2 hours, for example but not limited to, the processing time is any one of 1 hour, 1.2 hours, 1.4 hours, 1.6 hours, 1.8 hours and 2 hours, or a range between any two of them.

[0079] In this embodiment, the temperature of the concentrated nitric acid solution in the pretreatment step, the mass concentration of the concentrated nitric acid, the ultrasonic frequency and the treatment time are respectively limited to the above-mentioned ranges, which can achieve a better pretreatment effect, that is, the surface of the carbon fiber precursor can have an appropriate roughness and be grafted with an appropriate amount of polar groups (such as hydroxyl and carboxyl polar groups).

[0080] As an example, before the step of pre-treating the carbon fiber precursor, the method further includes a step of washing the carbon fiber precursor with an organic solution to remove the oil on the surface of the carbon fiber precursor.

[0081] In this embodiment, the carbon fiber precursor is cleaned with an organic solution before the pretreatment step, which can effectively remove the oil on the surface of the carbon fiber precursor, thereby improving the effect of subsequent pretreatment thereof.

[0082] As an example, the organic solution is selected from a mixed solution of ethanol and acetone.

[0083] As an example, the volume ratio of ethanol to acetone is 1:1.

[0084] In this embodiment, the organic solvent is a mixed solution of ethanol and acetone and the volume ratio of the two is limited to 1:1, which can more easily and thoroughly remove the oil agent on the surface of the carbon fiber precursor.

[0085] It should be noted that any process or step not specifically described or limited in the preparation of the modified carbon fiber may be configured according to conventional methods in the art.

[0086] As an example, in the drying treatment step, the treatment temperature is 80-90°C, for example but not limited to the treatment temperature being any one of 80°C, 82°C, 84°C, 86°C, 88°C and 90°C or a range between any two of them; the treatment time is 0.5-2h, for example but not limited to the treatment time being any one of 0.5h, 1h, 1.5h and 2h or a range between any two of them.

[0087] As an example, the carbonization treatment step is carried out under an inert gas atmosphere, wherein the treatment temperature is 750-850°C, for example but not limited to the treatment temperature being any one of 750°C, 770°C, 800°C, 820°C and 850°C or a range between any two of them; the treatment time is 1-2h, for example but not limited to the treatment time being any one of 1h, 1.2h, 1.4h, 1.6h, 1.8h and 2h or a range between any two of them.

[0088] As an example, the inert gas is selected from at least one of nitrogen and argon.

[0089] As an example, the process flow chart of the preparation method of modified carbon fiber can be found in Figure 1 .

[0090] In a second aspect, an embodiment of the present application provides a method for preparing a carbon fiber resin composite material, wherein the modified carbon fiber provided in the embodiment of the first aspect is subjected to sizing and curing treatment, and then the cured modified carbon fiber is composited with a resin.

[0091] In the above technical scheme, the modified carbon fiber provided in the first embodiment is used as a substrate, and then a carbon fiber resin composite material is prepared through sizing treatment, curing treatment and composite process. Since the modified carbon fiber has the advantages of relatively excellent strength and the carbon nanoparticles are more firmly bound in the material, the prepared composite material has the advantages of relatively excellent strength and higher interface bonding strength between the carbon fiber and the resin matrix.

[0092] It should be noted that during the sizing step, the composition of the sizing agent can be adaptively adjusted according to the type of resin material in the carbon fiber resin composite material, and is not specifically limited in the embodiments of this application. For example, if the resin material in the carbon fiber resin composite material is epoxy resin, the specific composition of the sizing agent is, by weight, 50-70 parts of bisphenol A diglycidyl ether, 20-35 parts of polyvinyl alcohol, and 5-15 parts of cocoyl glucoside.

[0093] It should be noted that the composite processing method is not limited, for example, compression molding technology can be used for composite processing.

[0094] It should be noted that any process or step not specifically described or limited in the preparation process of the carbon fiber resin composite material may be configured according to conventional selections in the art.

[0095] The features and performance of the present application are further described in detail below with reference to the embodiments.

[0096] Example 1

[0097] The present invention provides a method for preparing a carbon fiber resin composite material, comprising the following steps:

[0098] S1: 30 parts of resin matrix (phenolic resin), 6 parts of inorganic nanoparticles (including 4 parts of carbon nanotubes and 2 parts of silicon carbide nanoparticles, and the average particle size of both is 20 nm) and 3 parts of coupling agent (KH560) are dispersed in 100 parts of ethanol solvent according to the mass ratio to obtain a coating solution for modification.

[0099] S2 uses a mixed solvent of acetone and ethanol in a volume ratio of 1:1 to soak and clean the carbon fiber precursor (polyacrylonitrile carbon fiber precursor with a diameter of 8.5 μm) to remove the oil agent on the surface of the carbon fiber precursor; then the cleaned carbon fiber precursor is immersed in a concentrated nitric acid solution under ultrasonic conditions for pretreatment, wherein the temperature of the concentrated nitric acid solution is 60°C, the mass concentration of concentrated nitric acid is 65%, the ultrasonic frequency is 40 kHz, and the treatment time is 1.5 hours; then, the coating solution for modification is applied to the surface of the pretreated carbon fiber precursor, and then dried (treated at 80°C for 1 hour) to remove ethanol to obtain a modified carbon fiber precursor with a coating on the surface (coating thickness is 1 μm).

[0100] S3 carbonizes the modified carbon fiber precursor (in a nitrogen atmosphere, heats to 800° C. at a heating rate of 5° C. / min and keeps the temperature for 1 h) to obtain modified carbon fiber containing nanoparticles.

[0101] S4 coated the sizing agent (including 50 parts of bisphenol A diglycidyl ether, 35 parts of polyvinyl alcohol and 15 parts of coconut glucoside) onto the surface of the modified carbon fiber and performed a curing treatment (treated at 80°C for 1 hour), then mixed the cured carbon fiber with epoxy resin (E-51) in a mass ratio of 3:2, and adopted a compression molding technology (temperature control was: heat preservation at 85°C for 2 hours, heat preservation at 130°C for 2 hours, and heat preservation at 180°C for 2 hours) to prepare a carbon fiber resin composite material.

[0102] Example 2

[0103] This embodiment of the present application provides a method for preparing a carbon fiber resin composite material, which differs from Example 1 only in that in step S1, the inorganic nanoparticles further include two portions of graphite nanoparticles with an average particle size of 20 nm.

[0104] Comparative Example 1

[0105] The comparative example of the present application provides a method for preparing a carbon fiber resin composite material, comprising the following steps:

[0106] S1 pre-treats the carbonized carbon fiber (carbon fiber obtained by carbonizing polyacrylonitrile carbon fiber precursor with a diameter of 8.5 μm) by immersing it in a concentrated nitric acid solution under ultrasonic conditions, wherein the temperature of the concentrated nitric acid solution is 60°C, the mass concentration of concentrated nitric acid is 65%, the ultrasonic frequency is 40 kHz, and the treatment time is 1.5 h.

[0107] S2 coated the sizing agent (including 50 parts of bisphenol A diglycidyl ether, 35 parts of polyvinyl alcohol and 15 parts of coconut glucoside; as well as 4 parts of carbon nanotubes and 2 parts of silicon carbide nanoparticles, and the average particle size of both was 20 nm) onto the surface of the carbon fiber and cured it (treated at 80°C for 1 hour), then mixed the cured carbon fiber with epoxy resin (E-51) in a mass ratio of 3:2, and adopted compression molding technology (temperature control was: heat preservation at 85°C for 2 hours, heat preservation at 130°C for 2 hours, and heat preservation at 180°C for 2 hours) to prepare a carbon fiber resin composite material.

[0108] Comparative Example 2

[0109] The comparative example of the present application provides a method for preparing a carbon fiber resin composite material, comprising the following steps:

[0110] S1 uses a mixed solvent of acetone and ethanol in a volume ratio of 1:1 to immerse and clean the carbon fiber precursor (polyacrylonitrile carbon fiber precursor with a diameter of 8.5 μm) to remove the oil agent on the surface of the carbon fiber precursor; then the cleaned carbon fiber precursor is immersed in a concentrated nitric acid solution under ultrasonic conditions for pretreatment, wherein the temperature of the concentrated nitric acid solution is 60°C, the mass concentration of concentrated nitric acid is 65%, the ultrasonic frequency is 40 kHz, and the treatment time is 1.5 h.

[0111] S2 performs carbonization treatment on the pretreated carbon fiber precursor (in a nitrogen atmosphere, heating to 800°C at a heating rate of 5°C / min and keeping the temperature for 1 hour) to obtain carbon fiber.

[0112] S3 coated the sizing agent (including 50 parts of bisphenol A diglycidyl ether, 35 parts of polyvinyl alcohol and 15 parts of coconut glucoside) onto the surface of the carbon fiber and performed a curing treatment (treated at 80°C for 1 hour), then mixed the cured carbon fiber with epoxy resin (E-51) in a mass ratio of 3:2, and adopted a compression molding technology (temperature control was: heat preservation at 85°C for 2 hours, heat preservation at 130°C for 2 hours, and heat preservation at 180°C for 2 hours) to prepare a carbon fiber resin composite material.

[0113] Test example

[0114] Performance testing of carbon fiber resin composite materials

[0115] (1) Strength test of composite materials

[0116] The composite materials prepared in Examples 1-2 and Comparative Examples 1-2 were respectively used as samples, and the tensile strength and elastic modulus of each sample were tested, and the test results were statistically summarized in Table 1.

[0117] (2) Test of the interface bonding strength between carbon fiber and resin in composite materials

[0118] The composite materials prepared in Examples 1-2 and Comparative Examples 1-2 were respectively used as samples, and the interlaminar shear strength of the carbon fiber and the resin of each sample at 600° C. was tested, and the test results were statistically summarized in Table 1.

[0119] Table 1

[0120] sample Tensile strength (MPa) Elastic modulus (GPa) Interlaminar shear strength (MPa) Example 1 5967 294 73 Example 2 6023 305 86 Comparative Example 1 5887 287 63 Comparative Example 2 5648 289 67

[0121] Referring to Table 1, it can be seen from the test results of Examples 1 to 2 and Comparative Example 1 that in a system for improving the performance of carbon fiber using inorganic nanoparticles, the preparation process provided by the embodiment of the present application, compared with the conventional preparation process, the carbon fiber resin composite material prepared by the former has better strength, and the carbon fiber and resin in the composite material have better interface bonding strength.

[0122] From the test results of Examples 1 to 2 and Comparative Example 2, it can be seen that the carbon fiber resin composite material prepared by forming a coating containing nanoparticles on the surface of the carbon fiber precursor has better strength than that prepared by not forming a coating containing nanoparticles on the surface of the carbon fiber precursor, and the carbon fiber and resin in the composite material also have better interface bonding strength. Figure 2 、 Figure 3 and Figure 4 ,in, Figure 2 and Figure 3 Corresponding to the cross-sectional views of the carbon fibers and resin in Example 1 and Example 2, respectively, Figure 4 The cross-sectional view of the carbon fiber and resin in the corresponding example 2 shows that the carbon fiber and resin in Examples 1 and 2 are basically not separated, while the carbon fiber and resin in the comparative example 2 are more seriously separated, indicating that a coating containing inorganic nanoparticles is formed on the surface of the carbon fiber precursor, which can make the corresponding carbon fiber and resin have a relatively excellent interface bonding strength.

[0123] The embodiments described above are part of the embodiments of the present application, rather than all of the embodiments. The detailed description of the embodiments of the present application is not intended to limit the scope of the present application for protection, but merely represents selected embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of this application.

Claims

1. A method for preparing modified carbon fiber, characterized in that: The following steps are involved: dispersing a resin matrix, inorganic nanoparticles and a coupling agent in an organic solvent to obtain a coating solution for modification, wherein the inorganic nanoparticles include carbon nanoparticles; Applying the coating solution for modification to the surface of the carbon fiber precursor, and then drying it to remove the organic solvent to obtain a modified carbon fiber precursor with a coating on the surface; The modified carbon fiber precursor is carbonized to obtain modified carbon fiber containing the inorganic nanoparticles.

2. The method for preparing modified carbon fiber according to claim 1, wherein The coating solution comprises, by weight, 30 to 40 parts of the resin matrix, 1 to 10 parts of the inorganic nanoparticles, 1 to 5 parts of the coupling agent, and 80 to 100 parts of the organic solvent.

3. The method for preparing modified carbon fiber according to claim 2, wherein: In the modified carbon fiber precursor, the coating has a thickness of 1 to 2 μm.

4. The method for preparing modified carbon fiber according to claim 2, wherein: The inorganic nanoparticles also include silicon carbide nanoparticles; Optionally, the mass ratio of the silicon carbide nanoparticles to the carbon nanoparticles is (2-6):

1.

5. The method for preparing modified carbon fiber according to any one of claims 1 to 4, characterized in that: The diameter of the carbon fiber precursor is 8 to 10 μm, and the particle size of the inorganic nanoparticles is 10 to 100 nm; Optionally, the carbon fiber precursor is selected from polyacrylonitrile fiber; Optionally, the resin matrix is selected from at least one of phenolic resin, melamine-formaldehyde resin and epoxy resin; Optionally, the coupling agent is selected from at least one of KH560, Z6040 and KBM403.

6. The method for preparing modified carbon fiber according to any one of claims 1 to 4, characterized in that: Before applying the coating solution for modification to the surface of the carbon fiber precursor, the method further includes a step of pretreating the carbon fiber precursor to increase the surface roughness of the carbon fiber precursor and graft polar groups onto the surface.

7. The method for preparing modified carbon fiber according to claim 6, characterized in that: The pretreatment step includes: immersing the carbon fiber precursor in a concentrated nitric acid solution under ultrasonic conditions for surface treatment.

8. The method for preparing modified carbon fiber according to claim 7, characterized in that: In the pretreatment step, at least one of the following conditions A to D is met: The temperature of the concentrated nitric acid solution A is 55-65°C; The mass concentration of the concentrated nitric acid in B is 60-70%; C Ultrasonic frequency is 30-50kHz; D processing time is 1 to 2 hours.

9. The method for preparing modified carbon fiber according to claim 6, wherein: Before the step of pre-treating the carbon fiber precursor, the method further includes the step of washing the carbon fiber precursor with an organic solution to remove the oil on the surface of the carbon fiber precursor; Optionally, the organic solution is selected from a mixed solution of ethanol and acetone; Optionally, the volume ratio of the ethanol to the acetone is 1:

1.

10. A method for preparing a carbon fiber resin composite material, characterized in that: The modified carbon fiber according to any one of claims 1 to 9 is subjected to sizing treatment and curing treatment, and then the cured modified carbon fiber is composited with a resin.

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