Sizing agent, polyacrylonitrile-based carbon fiber, preparation method and composite material

Abstract

The embodiment of the invention provides a sizing agent, polyacrylonitrile-based carbon fiber, a preparation method and a composite material, and relates to the technical field of carbon fiber production. The non-volatile components in the sizing agent disclosed by the embodiment of the invention comprise the following components in percentage by weight: 40-70wt% of epoxy resin, 15-30wt% of a water-borne epoxy resin emulsifier, 5-25wt% of a smoothing agent and 5-25wt% of acrylate resin, wherein the molecular weight of the epoxy resin is less than or equal to 500. According to the sizing agent, the polyacrylonitrile-based carbon fiber, the preparation method and the composite material, the hardness of the sized carbon fiber can be reduced, and the sizing agent is suitable for subsequent processing.

Description

Technical Field

[0001] The present application relates to the technical field of carbon fiber production. Specifically, it relates to a sizing agent, a polyacrylonitrile-based carbon fiber, a preparation method thereof, and a composite material. Background Art

[0002] In the production process of carbon fiber, the use of a sizing agent can not only reduce the generation amount of fuzz caused by mechanical friction, but also increase the surface activity of carbon fiber by introducing some chemical functional groups, thereby improving the interfacial adhesion strength between carbon fiber and matrix in the composite material. The carbon fiber formed by the dry-jet wet-spinning process has the advantages of few surface defects, excellent tensile properties, fast spinning speed, and excellent properties of the corresponding composite material. However, during the carbonization process of dry-jet wet-spun carbon fiber, the graphite crystal structure inside the carbon fiber is complete and closely arranged, so it has a high hardness. At present, after such carbon fiber is sized with a conventional sizing agent, the bundling property and hardness are improved, which are not suitable for subsequent processing processes such as weaving, needling, and yarn spreading; especially in winter, affected by temperature and humidity, the hardness of carbon fiber increases more significantly after sizing, making it even less suitable for subsequent processing. Summary of the Invention

[0003] The purpose of the embodiments of the present application is to provide a sizing agent, a polyacrylonitrile-based carbon fiber, a preparation method thereof, and a composite material, which can reduce the hardness of the sized carbon fiber and are suitable for subsequent processing.

[0004] In a first aspect, the embodiments of the present application provide a sizing agent, and the non-volatile components thereof by weight percentage include: 40wt% - 70wt% of epoxy resin, 15wt% - 30wt% of water-based epoxy resin emulsifier, 5wt% - 25wt% of smoothing agent, 5wt% - 25wt% of acrylate resin, and the molecular weight of the epoxy resin ≤ 500.

[0005] In the above technical solution, the main component of the sizing agent is an epoxy resin with a small molecular weight. After sizing the carbon fiber with this sizing agent, the flexibility and wettability of the carbon fiber can be improved, thereby reducing the hardness of the carbon fiber. The sized carbon fiber will not be too hard even in winter and is suitable for subsequent processing; in addition, although using a main component with a small molecular weight in the sizing agent will reduce the bundling property and wear resistance of the carbon fiber, the present application uses a combination of a smoothing agent, acrylate resin and an epoxy resin with a small molecular weight, which can make up for the above deficiencies and enable the carbon fiber to have good bundling property and wear resistance.

[0006] In a possible implementation manner, the epoxy resin includes one or more of E44 type epoxy resin, E51 type epoxy resin, F44 type epoxy resin, F51 type epoxy resin, and F48 type epoxy resin.

[0007] In the above technical solution, the above type of epoxy resin can improve the bundling property of the sized carbon fiber, and also improve the compatibility between the sized carbon fiber and the resin matrix to form a composite material.

[0008] In a possible implementation, the aqueous epoxy resin emulsifier includes a modified polyether active emulsifier containing a polyether segment, and the modified polyether active emulsifier is obtained by hydrophilic modification using a main resin, and the main resin includes one or more of E51 type epoxy resin and E44 type epoxy resin.

[0009] In the above technical solution, the above aqueous epoxy resin emulsifier not only has good emulsifying ability, but also when forming a composite material with the sized carbon fiber and the epoxy resin matrix, the epoxy groups contained in the aqueous epoxy resin emulsifier react with the epoxy groups of the epoxy resin matrix, and at the same time crosslinking reactions occur by means of the curing agent contained in the resin matrix, and a firm interfacial layer can be formed.

[0010] In a possible implementation, the molecular weight of the acrylate resin ≤ 2000.

[0011] In the above technical solution, the molecular weight of the acrylate resin is relatively low. If the molecular weight of the acrylate resin is too high, it will not only lead to a decrease in the flexibility of the sizing agent system, but also reduce the interfacial adhesion between the sized carbon fiber and the resin matrix when forming a composite material with the sized carbon fiber and the epoxy resin matrix.

[0012] In a possible implementation, the acrylate resin includes one or more of polyacrylate resin, polyether acrylate resin, polyester acrylate resin, and polyurethane acrylate resin.

[0013] In the above technical solution, the above acrylate resin contains strongly polar ester groups, which can improve the adhesion between carbon fiber filaments to make up for the decrease in the bundling property of carbon fibers due to the use of a main component with a small molecular weight in the sizing agent.

[0014] In a possible implementation, the smoothing agent includes one or more of polyethylene wax, polypropylene wax, oxidized polyethylene wax, oxidized polypropylene wax, modified polyethylene wax, modified polypropylene wax, polyethylene glycol monolaurate, polyethylene glycol monoheptanoate, polyethylene glycol monooctanoate, polyethylene glycol monononanoate, polyethylene glycol dilaurate, polyethylene glycol monopentadecanoate, polyethylene glycol myristate, polyethylene glycol dioctanoate, polyethylene glycol monopalmitate, polyethylene glycol monolinoleate, polyethylene glycol monooleate, and polyethylene glycol dioleate.

[0015] In the above technical solution, using the above-mentioned leveling agent in the sizing agent and sizing the carbon fiber can reduce the surface friction of the carbon fiber and endow it with good dispersibility, so that the resin matrix can fully infiltrate the carbon fiber when forming the composite material. The addition amount of the leveling agent in the sizing agent needs to be in a certain mass ratio. If the addition amount of the leveling agent is too small, the effect of good dispersion cannot be achieved, and if it is too much, the interfacial bonding strength between the carbon fiber and the resin matrix will be reduced.

[0016] In a second aspect, an embodiment of the present application provides a method for preparing the sizing agent provided in the first aspect, including the following steps:

[0017] Mix epoxy resin, aqueous epoxy resin emulsifier, leveling agent and acrylate resin and heat them to melting, and then add deionized water under high-speed dispersion conditions to achieve phase inversion.

[0018] In the above technical solution, the sizing agent is prepared by the phase inversion method. The preparation process is simple, the cost is low, and the stability of the prepared sizing agent is excellent.

[0019] In a third aspect, an embodiment of the present application provides a polyacrylonitrile-based carbon fiber, including a carbon fiber matrix and a coating layer located on the surface of the carbon fiber matrix. The carbon fiber matrix is formed by dry-jet wet spinning of polyacrylonitrile, and the coating layer is dried from the sizing agent provided in the first aspect.

[0020] In a fourth aspect, an embodiment of the present application provides a method for preparing a polyacrylonitrile-based carbon fiber, which includes the following steps:

[0021] Form a carbon fiber matrix by dry-jet wet spinning of polyacrylonitrile;

[0022] After impregnating the carbon fiber matrix in the sizing agent provided in the first aspect, dry it.

[0023] In a fifth aspect, an embodiment of the present application provides a composite material, including a resin matrix and the carbon fiber prepared by the polyacrylonitrile-based carbon fiber provided in the third aspect or the method for preparing the polyacrylonitrile-based carbon fiber provided in the fourth aspect. Detailed Embodiments

[0024] To make the objectives, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be clearly and completely described below. Those not specified in the embodiments are carried out according to conventional conditions or conditions recommended by the manufacturer. Those reagents or instruments not specified by the manufacturer can be obtained as conventional products through commercial purchase.

[0025] The following specifically describes a sizing agent, a polyacrylonitrile-based carbon fiber, a preparation method and a composite material according to an embodiment of the present application.

[0026] An embodiment of the present application provides a sizing agent, which includes a non-volatile component and a solvent. The non-volatile component includes, by weight percentage: 40wt% - 70wt% of epoxy resin, 15wt% - 30wt% of an aqueous epoxy resin emulsifier, 5wt% - 25wt% of a smoothing agent, 5wt% - 25wt% of an acrylate resin, and the molecular weight of the epoxy resin ≤ 500.

[0027] Exemplarily, the non-volatile component includes, by weight percentage: 40wt%, 50wt%, 60wt%, 70wt% of epoxy resin or an intermediate value between any two of the above values, 15wt%, 20wt%, 25wt%, 30wt% of an aqueous epoxy resin emulsifier or an intermediate value between any two of the above values, 5wt%, 10wt%, 15wt%, 20wt%, 25wt% of a smoothing agent or an intermediate value between any two of the above values, 5wt%, 10wt%, 15wt%, 20wt%, 25wt% of an acrylate resin or an intermediate value between any two of the above values.

[0028] In some embodiments of the present application, the solvent is deionized water.

[0029] In some embodiments of the present application, the sizing agent is an emulsion, and the solid content (mass ratio of the non-volatile component) of the emulsion is 40% - 70%.

[0030] In some embodiments of the present application, the epoxy resin includes one or more of E44 type epoxy resin, E51 type epoxy resin, F44 type epoxy resin, F51 type epoxy resin, and F48 type epoxy resin. The aqueous epoxy resin emulsifier used in the embodiments of the present application can be a commercially available product. Exemplarily, the epoxy resin is E44 type epoxy resin (such as the E44 type epoxy resin product of production manufacturer Baling Petrochemical with a molecular weight of 350 - 400), E51 type epoxy resin (such as the E51 type epoxy resin product of production manufacturer Baling Petrochemical with a molecular weight of 300 - 350).

[0031] In some embodiments of the present application, the aqueous epoxy resin emulsifier includes a modified polyether active emulsifier containing a polyether chain segment (a commercially available product), and this modified polyether active emulsifier is obtained by hydrophilic modification of the main resin, and the main resin includes one or more of E51 type epoxy resin and E44 type epoxy resin. The aqueous epoxy resin emulsifier used in the embodiments of the present application can be a commercially available product. Exemplarily, the aqueous epoxy resin emulsifier is the product of production manufacturer Foshan Juntu New Materials with the brand JT - 801.

[0032] In some embodiments of the present application, the molecular weight of the acrylate resin ≤ 2000.

[0033] In some embodiments of the present application, the acrylate resin includes one or more of polyacrylate resin, polyether acrylate resin, polyester acrylate resin, and polyurethane acrylate resin. The acrylate resin used in the embodiments of the present application can be a commercially available product. Exemplarily, the acrylate resin is polyacrylate resin (such as producer Wanhua Chemical 1366, molecular weight 200 - 300), polyether acrylate resin (such as producer Nanjing Kailian KLF0913, molecular weight 150 - 200).

[0034] In some embodiments of the present application, the leveling agent includes one or more of polyethylene wax, polypropylene wax, oxidized polyethylene wax, oxidized polypropylene wax, modified polyethylene wax, modified polypropylene wax, polyethylene glycol monolaurate, polyethylene glycol monoheptanoate, polyethylene glycol monocaprylate, polyethylene glycol monononanoate, polyethylene glycol dilaurate, polyethylene glycol monopentadecanoate, polyethylene glycol myristate, polyethylene glycol dicaprylate, polyethylene glycol monopalmitate, polyethylene glycol monolinoleate, polyethylene glycol monooleate, and polyethylene glycol dioleate.

[0035] The embodiments of the present application provide a preparation method of the sizing agent of the foregoing embodiments, which is prepared by the phase inversion method and specifically includes the following steps:

[0036] Mix epoxy resin, aqueous epoxy resin emulsifier, leveling agent, and acrylate resin and heat to melting, and then add deionized water under high-speed dispersion conditions to achieve phase inversion.

[0037] The embodiments of the present application provide a polyacrylonitrile-based carbon fiber, which includes a carbon fiber matrix and a coating layer on the surface of the carbon fiber matrix. The carbon fiber matrix is formed by using polyacrylonitrile through the dry-jet wet-spinning process, and the coating layer is dried from the sizing agent of the foregoing embodiments.

[0038] The embodiments of the present application provide a preparation method of a polyacrylonitrile-based carbon fiber, which includes the following steps:

[0039] Use polyacrylonitrile to form a carbon fiber matrix through the dry-jet wet-spinning process;

[0040] Immerse the carbon fiber matrix in the sizing agent of the foregoing embodiments and then dry it.

[0041] The embodiments of the present application provide a composite material, which includes a resin matrix and the polyacrylonitrile-based carbon fiber of the foregoing embodiments or the carbon fiber prepared by the preparation method of the polyacrylonitrile-based carbon fiber of the foregoing embodiments. As an implementation manner, the resin matrix is an epoxy resin matrix.

[0042] The features and properties of the present application are further described in detail below in conjunction with embodiments.

[0043] Example 1

[0044] This example provides a sizing agent, and its preparation process is as follows:

[0045] By weight, 50 parts of E51 type epoxy resin (manufacturer: Baling Petrochemical, molecular weight 300 - 350), 20 parts of waterborne epoxy resin emulsifier (manufacturer: Foshan Juntu New Materials, grade JT - 801), 15 parts of polypropylene wax, and 15 parts of polyurethane acrylate (manufacturer: Shin-Nakamura Chemical Co., Ltd., UA - 160TM, molecular weight 1000) are added to a reactor equipped with a stirrer, and heated to 80 °C to fully melt the system; 5 parts of absolute ethanol are added as a co - solvent, and the whole system is mixed evenly; then, under the condition of high - speed dispersion at 3000 r / min, deionized water is slowly added to the system to achieve inversion, and water is continuously added to make the solid content of the system reach 50%, and then the system is kept under high - speed dispersion for 30 min. Finally, a milky white waterborne epoxy emulsion, that is, the sizing agent, is obtained.

[0046] Example 2

[0047] This example provides a sizing agent, and the difference in its preparation process from that of Example 1 is that: 70 parts of E51 type epoxy resin, 15 parts of waterborne epoxy resin emulsifier, 10 parts of polypropylene wax, and 5 parts of polyurethane acrylate are used.

[0048] Example 3

[0049] This example provides a sizing agent, and the difference in its preparation process from that of Example 1 is that: 40 parts of E51 type epoxy resin, 30 parts of waterborne epoxy resin emulsifier, 20 parts of polypropylene wax, and 10 parts of polyurethane acrylate are used.

[0050] Example 4

[0051] This example provides a sizing agent, and the difference in its preparation process from that of Example 1 is that: E44 type epoxy resin (manufacturer: Baling Petrochemical, molecular weight 350 - 400) is selected as the epoxy resin.

[0052] Example 5

[0053] This example provides a sizing agent, and the difference in its preparation process from that of Example 1 is that: a waterborne epoxy resin emulsifier (manufacturer: Shanghai Zhongcheng ER - 9200) is selected as the waterborne epoxy resin emulsifier.

[0054] Example 6

[0055] This example provides a sizing agent, and the difference in its preparation process from that of Example 1 is that: polyethylene glycol monolaurate is selected as the smoothing agent.

[0056] Example 7

[0057] This embodiment provides a sizing agent, and the difference in its preparation process from that of Embodiment 1 lies in that: 15 parts of polyacrylate resin (manufacturer: Satellite Chemical STL-550, molecular weight 400 - 450) is used as the acrylate resin.

[0058] Comparative Example 1

[0059] Commercial epoxy sizing agent MU6021.

[0060] Test Example

[0061] The sizing agents prepared in Examples 1 - 7, the commercial sizing agent of Comparative Example 1, and the sizing agent prepared in Comparative Example 2 were respectively diluted to a solid content of 1.3%, and attached to SYT49S-2K carbon fiber tows (carbon fiber matrix) by the impregnation method, and then dried at 200 °C to obtain the corresponding sized carbon fibers respectively.

[0062] Each sized carbon fiber was respectively compounded with an epoxy resin matrix to form each composite material.

[0063] The particle size and stability of the above sizing agents (emulsions) were tested, the fiber hardness, hairiness quantification, and fiber opening rate of the above sized carbon fibers were tested, and the interlaminar shear strength of the above composite materials (sized carbon fiber / epoxy resin) was tested.

[0064] Among them, (1) The particle size of the above sizing agent (emulsion) was tested using a laser particle size analyzer. The emulsion sample was automatically diluted to an appropriate concentration for testing, and the analyzer model was Microtrac S3500;

[0065] (2) The above sizing agents (emulsions) were allowed to stand for 1 month, and the emulsion stability was observed. If the emulsion had no stratification and no precipitation at the bottom, the stability was excellent; if the emulsion had no stratification but had precipitation at the bottom, the stability was good; if the emulsion was stratified and had precipitation at the bottom, the stability was poor;

[0066] (3) The tests were carried out according to the methods for fiber hardness, hairiness quantification, and fiber opening rate in "Carbon Fibers and Graphite Fibers";

[0067] (4) The interlaminar shear strength was measured in accordance with GB / T 30969.

[0068] The particle size and stability of the sizing agent, the fiber hardness, hairiness quantification, and fiber opening rate of the sized carbon fiber, and the test data of the interlaminar shear strength between the sized carbon fiber and the epoxy resin matrix in the composite material are listed in Table 1.

[0069] Table 1 Performance Results of Different Examples and Comparative Examples

[0070]

[0071] As can be seen from Table 1, compared with the pure epoxy sizing agent of Comparative Example 1, the hardness of the sized fiber prepared in Examples 1 to 7 is significantly lower, which proves that the sizing agent of the embodiments of the present application can reduce the hardness of the carbon fiber after sizing treatment. In addition, the particle size of the sizing agent emulsion prepared in the embodiments of the present application (Examples 1, 3 to 7) is very small and the stability is excellent; the quantitative analysis of the carbon fiber hair treated with the sizing agent of the embodiments of the present application (Examples 1 to 2, Examples 4 to 7) is low (good flexibility) and the fiber opening property is good; the carbon fiber of the embodiments of the present application has good compatibility with the resin matrix, so the carbon fiber of the embodiments of the present application has a wider application range.

[0072] In summary, the sizing agent, polyacrylonitrile-based carbon fiber and preparation method and composite material of the embodiments of the present application can reduce the hardness of the sized carbon fiber and are suitable for subsequent processing.

[0073] The above are only the embodiments of the present application and are not intended to limit the protection scope of the present application. For those skilled in the art, the present application can have various changes and modifications. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A sizing agent, characterized in that, The non-volatile components therein, by weight percentage, include: 40wt% - 70wt% of epoxy resin, 15wt% - 30wt% of aqueous epoxy resin emulsifier, 5wt% - 25wt% of smoothing agent, and 5wt% - 25wt% of acrylate resin, and the molecular weight of the epoxy resin ≤ 500.

2. The sizing agent according to claim 1, characterized in that, The epoxy resin includes one or more of E44 type epoxy resin, E51 type epoxy resin, F44 type epoxy resin, F51 type epoxy resin, and F48 type epoxy resin.

3. The sizing agent according to claim 1 or 2, characterized in that, The aqueous epoxy resin emulsifier includes a modified polyether active emulsifier containing a polyether segment, and the modified polyether active emulsifier is obtained by hydrophilic modification using a main resin, and the main resin includes one or more of E51 type epoxy resin and E44 type epoxy resin.

4. The sizing agent according to claim 1, characterized in that, The molecular weight of the acrylate resin ≤ 2000.

5. The sizing agent according to claim 1 or 4, characterized in that, The acrylate resin includes one or more of polyacrylate resin, polyether acrylate resin, polyester acrylate resin, and polyurethane acrylate resin.

6. The sizing agent according to claim 1, characterized in that, The smoothing agent includes one or more of polyethylene wax, polypropylene wax, oxidized polyethylene wax, oxidized polypropylene wax, modified polyethylene wax, modified polypropylene wax, polyethylene glycol monolaurate, polyethylene glycol monoheptanoate, polyethylene glycol monooctanoate, polyethylene glycol monononanoate, polyethylene glycol dilaurate, polyethylene glycol monopalmitate, polyethylene glycol monostearate, polyethylene glycol dioctanoate, polyethylene glycol monopalmitate, polyethylene glycol monolinoleate, polyethylene glycol monooleate, and polyethylene glycol dioleate.

7. A method for preparing a sizing agent according to any one of claims 1 to 6, characterized in that, It includes the following steps: Mix the epoxy resin, aqueous epoxy resin emulsifier, smoothing agent, and acrylate resin and heat them to melting, and then add deionized water under high-speed dispersion conditions to achieve phase inversion.

8. A polyacrylonitrile-based carbon fiber, characterized in that, It includes a carbon fiber matrix and a coating layer on the surface of the carbon fiber matrix. The carbon fiber matrix is formed by dry-jet wet spinning of polyacrylonitrile, and the coating layer is dried from the sizing agent according to any one of claims 1 - 6.

9. A method for preparing polyacrylonitrile-based carbon fiber, characterized in that, It includes the following steps: Form a carbon fiber matrix by dry-jet wet spinning of polyacrylonitrile; Immerse the carbon fiber matrix in the sizing agent according to any one of claims 1 - 6 and then dry it.

10. A composite material, characterized in that, It includes a resin matrix and carbon fibers prepared by the preparation method of the polyacrylonitrile-based carbon fiber according to claim 8 or the polyacrylonitrile-based carbon fiber according to claim 9.

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