Moisture-heat resistant sizing agent and preparation method thereof, carbon fiber and composite material thereof

Abstract

The present invention provides a heat-resistant sizing agent and a preparation method thereof, as well as carbon fibers and composite materials thereof, relating to the technical field of sizing agents for carbon fibers. The sizing agent comprises the following components, measured by mass: 10 to 20 parts of an epoxy resin prepolymer, 10 to 20 parts of a polyurethane-modified epoxy resin, 20 to 30 parts of a fluorene-based epoxy resin, and 50 to 60 parts of water. The present invention solves the technical problem of poor heat-resistant stability of carbon fiber-reinforced resin-based composite materials in the prior art, achieving the technical effect of having a high interfacial bonding strength between the carbon fibers and the resin matrix in the composite material and relatively excellent heat-resistant stability of the composite material.

Description

Technical Field

[0001] The present invention relates to the technical field of sizing agents for carbon fibers, and in particular to a moisture-heat resistant sizing agent and a preparation method thereof, carbon fibers and composite materials thereof. Background Art

[0002] Carbon fiber reinforced resin-based composites have excellent specific strength and modulus, as well as good designability, and are widely used in sports and leisure, pressure vessels, aerospace, and other fields. However, carbon fiber is a brittle material, and mechanical friction during the manufacturing process can easily lead to single-filament breakage and fuzzing.

[0003] Studies have shown that sizing treatment of carbon fiber can effectively protect the carbon fiber and reduce the incidence of hair and broken fibers. At the same time, after sizing treatment, a resin transition layer will be formed on the surface of the carbon fiber, which can increase the surface activity of the carbon fiber and effectively improve the interface bonding strength between the carbon fiber and the resin matrix.

[0004] At present, sizing agents are mainly glycidyl ether epoxy resins such as E51 and E44. The carbon fibers corresponding to this type of sizing agent have a high interfacial bonding strength with the epoxy resin matrix; however, the corresponding carbon fiber reinforced resin-based composite materials have poor moisture and heat resistance stability, which has affected the promotion and application of epoxy resin sizing agents.

[0005] Fluorene-based epoxy resin is a new type of moisture-heat resistant epoxy resin with excellent moisture-heat resistance. However, it has many rigid groups and the cured resin has poor toughness, making it unsuitable for direct use as a carbon fiber sizing agent.

[0006] In view of this, the present invention is proposed. Summary of the Invention

[0007] One of the objects of the present invention is to provide a moisture-heat resistant sizing agent having excellent moisture-heat resistance stability.

[0008] The second object of the present invention is to provide a method for preparing a moisture-heat resistant sizing agent, which has a simple process, high efficiency, high success rate, and is suitable for industrial production.

[0009] The third object of the present invention is to provide a carbon fiber that has a high interface bonding strength after being combined with a resin matrix, and at the same time has relatively excellent moisture and heat resistance stability with the resin matrix, and can also increase the impact resistance of the material.

[0010] A fourth object of the present invention is to provide a composite material that not only has high interface bonding strength, but also has relatively excellent moisture and heat stability and better impact resistance.

[0011] In order to achieve the above-mentioned purpose of the present invention, the following technical solutions are adopted:

[0012] In a first aspect, a heat and moisture resistant sizing agent comprises the following components in parts by mass:

[0013] 10 to 20 parts of epoxy resin prepolymer, 10 to 20 parts of polyurethane modified epoxy resin, 20 to 30 parts of fluorene-based epoxy resin, and 50 to 60 parts of water.

[0014] Furthermore, the epoxy resin prepolymer includes a water-based epoxy resin prepolymer.

[0015] Furthermore, the waterborne epoxy resin prepolymer includes at least one of an etherification reaction type modified epoxy resin and a grafting reaction type ion group modified epoxy resin.

[0016] Furthermore, the etherification reaction type modified epoxy resin includes at least one of polyethylene oxide modified epoxy resin and polypropylene oxide modified epoxy resin.

[0017] Furthermore, the graft reaction type ion-modified epoxy resin includes at least one of an acrylic acid graft modified epoxy resin and a maleic anhydride graft modified epoxy resin.

[0018] Furthermore, the fluorene-based epoxy resin includes at least one of bisphenol fluorene epoxy resin and bis-o-cresol fluorene epoxy resin.

[0019] In a second aspect, a method for preparing the moisture-heat resistant sizing agent described in any one of the above items comprises the following steps:

[0020] The components are mixed in proportion to obtain the moisture and heat resistant sizing agent.

[0021] Furthermore, the mixing process conditions include stirring at a rotation speed of 2000 r / min to 3000 r / min for 3 min to 5 min.

[0022] In a third aspect, a carbon fiber comprises a carbon fiber matrix and a surface coating layer thereof;

[0023] The coating layer is formed by any one of the above-mentioned moisture-heat resistant sizing agents.

[0024] In a fourth aspect, a composite material comprises an epoxy resin matrix, and carbon fibers bonded to the epoxy resin matrix;

[0025] The carbon fibers include the carbon fibers described above.

[0026] Compared with the prior art, the present invention has at least the following beneficial effects:

[0027] The moisture-heat resistant sizing agent provided by the present invention introduces a fluorenyl epoxy resin into an epoxy resin and simultaneously adds a polyurethane-modified epoxy resin. With the coordinated cooperation of the components and their proportions, the corresponding composite material can have relatively excellent moisture-heat stability and can also increase the impact resistance of the composite material. Specifically, the epoxy resin prepolymer and the polyurethane-modified epoxy resin have self-emulsifying properties and can therefore assist the fluorenyl epoxy resin in achieving a better emulsification effect. Compared with directly using an emulsifier to assist the emulsification of the fluorenyl epoxy resin, the epoxy resin prepolymer and the polyurethane-modified epoxy resin will basically not affect the moisture-heat stability while assisting the emulsification, thereby enabling the corresponding composite material to have even better moisture-heat stability.

[0028] The preparation method of the moisture-heat resistant sizing agent provided by the invention has simple process, high efficiency, high success rate and is suitable for industrial production.

[0029] The carbon fiber provided by the present invention has a high interface bonding strength after being combined with the resin matrix. At the same time, it also has relatively excellent moisture and heat resistance stability with the resin matrix, and can also increase the impact resistance of the material.

[0030] The composite material provided by the present invention not only has high interface bonding strength, but also has relatively excellent moisture and heat resistance stability and better impact resistance. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] In order to more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the specific embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0032] Figure 1 The structural formula of a fluorenyl epoxy resin provided in one embodiment of the present invention is shown. DETAILED DESCRIPTION

[0033] The following will clearly and completely describe the technical solutions of the present invention in conjunction with the embodiments. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0034] While the mainstream epoxy resin sizing agents in the prior art can achieve high interfacial bonding strength between the sized carbon fibers and the epoxy resin matrix, the corresponding carbon fiber-reinforced resin-based composites suffer from poor moisture and heat stability. In light of this, the present invention is proposed.

[0035] According to a first aspect of the present invention, there is provided a moisture-heat resistant sizing agent comprising the following components in parts by mass:

[0036] 10 to 20 parts of epoxy resin prepolymer, 10 to 20 parts of polyurethane modified epoxy resin, 20 to 30 parts of fluorene-based epoxy resin, and 50 to 60 parts of water.

[0037] In the present invention, typical but non-limiting mass parts of epoxy resin prepolymer are, for example, 10 parts, 12 parts, 14 parts, 16 parts, 18 parts, and 20 parts; typical but non-limiting mass parts of polyurethane modified epoxy resin are, for example, 10 parts, 12 parts, 14 parts, 16 parts, 18 parts, and 20 parts; typical but non-limiting mass parts of fluorenyl epoxy resin are, for example, 20 parts, 22 parts, 24 parts, 26 parts, 28 parts, and 30 parts; typical but non-limiting mass parts of water are, for example, 50 parts, 52 parts, 54 parts, 56 parts, 58 parts, and 60 parts.

[0038] It should be noted that the fluorenyl epoxy resin molecular chain is connected to the benzene ring by the fluorenyl group. Figure 1 Fluorene is a stable rigid group with excellent moisture and heat resistance, dielectric properties, mechanical properties and chemical resistance. Although the rigidity of the fluorene-based epoxy resin molecular chain is greater than that of general epoxy resin and can significantly improve heat resistance, the rigidity of fluorene-based epoxy resin is too high. Using it alone as a sizing agent will have an adverse effect on the performance of the composite material, especially its impact resistance.

[0039] By introducing fluorenyl groups into epoxy resin sizing agents, with the help of the rigid groups stabilized by the fluorenyl groups, it is made to have excellent comprehensive properties such as moisture and heat resistance, dielectric properties, mechanical properties and chemical resistance; in short, the rigidity of the fluorenyl epoxy resin molecular chain is greater than that of the general epoxy resin, which significantly improves the heat resistance, and thus is conducive to improving the moisture and heat stability of the corresponding carbon fiber reinforced resin-based composite material. However, compounding the fluorenyl epoxy resin with a conventional emulsifier to prepare a fluorenyl epoxy resin sizing agent has the following disadvantages: the conventional emulsifier component is extremely hydrophilic and easily absorbs water under wet and hot conditions, which affects the moisture and heat stability of the fluorenyl group, making it difficult to effectively improve the moisture and heat stability of the corresponding carbon fiber reinforced resin-based composite material. At the same time, since the fluorenyl epoxy resin itself is too rigid, it has a negative impact on the impact resistance of the carbon fiber reinforced resin-based composite material.

[0040] The present invention innovatively compounds an epoxy resin prepolymer with self-emulsifying properties and a polyurethane-modified epoxy resin with a fluorene-based epoxy resin. With the synergistic coordination of the components and their proportions, the purpose of assisting the emulsification of the fluorene-based epoxy resin is achieved while effectively reducing the impact on the fluorene-based moisture and heat stability, and improving the impact strength of the material.

[0041] In a preferred embodiment, the epoxy resin prepolymer used in the present invention may be a water-based epoxy resin prepolymer. The use of a specific type of epoxy resin prepolymer is more conducive to achieving an excellent emulsification effect of the fluorene-based epoxy resin.

[0042] In a preferred embodiment, the waterborne epoxy resin prepolymer includes but is not limited to at least one of an etherification reaction type modified epoxy resin and a graft reaction type ion group modified epoxy resin. The waterborne epoxy resin prepolymer of this particular system has the advantages of relatively excellent physical and chemical properties and a wide range of applicability.

[0043] In a preferred embodiment, the etherification reaction type modified epoxy resin includes but is not limited to at least one of polyethylene oxide modified epoxy resin and polypropylene oxide modified epoxy resin.

[0044] In a preferred embodiment, the graft-reactive ion-modified epoxy resin includes but is not limited to at least one of an acrylic acid-grafted modified epoxy resin and a maleic anhydride-grafted modified epoxy resin.

[0045] The etherification reaction type modified epoxy resin and the graft reaction type ion group modified epoxy resin each have a large number of applicable types, and thus can provide more feasible implementation plans, which is conducive to the promotion and application of the technical solution of the present invention.

[0046] In a preferred embodiment, the fluorene-based epoxy resin includes but is not limited to at least one of bisphenol fluorene epoxy resin and bis-o-cresol fluorene epoxy resin.

[0047] According to a second aspect of the present invention, there is provided a method for preparing the moisture-heat resistant sizing agent described in any one of the above, comprising the following steps:

[0048] The components are mixed in proportion to obtain a moisture and heat resistant sizing agent.

[0049] In the present invention, epoxy resin prepolymer, polyurethane modified epoxy resin and fluorene epoxy resin are firstly mixed in proportion to obtain a mixed solution; water is then added to the mixed solution and stirred to obtain a moisture and heat resistant sizing agent.

[0050] The preparation method of the moisture-heat resistant sizing agent provided by the invention has simple process, high efficiency, high success rate and is suitable for industrial production.

[0051] The sizing agent prepared by the present invention can not only improve the moisture and heat resistance stability of the corresponding composite material, but also increase the impact resistance of the composite material; at the same time, the preparation method of the present invention also has the advantages of simple process, no use of organic solvents, safety and environmental protection, and low production cost.

[0052] In the present invention, water is added to the mixed solution and stirred at a speed of 2000 r / min to 3000 r / min for 3 to 5 minutes. The speed and stirring time are limited within a specific range, which is more conducive to sufficient emulsification of the mixed system. At the same time, the formed sizing agent emulsion can have a suitable particle size, thereby giving the sizing agent higher stability.

[0053] According to a third aspect of the present invention, there is provided a carbon fiber, comprising a carbon fiber matrix and a surface coating layer thereof;

[0054] The coating layer is formed by any one of the above-mentioned moisture-heat resistant sizing agents.

[0055] In the present invention, the surface coating layer of the carbon fiber is formed by drying a moisture- and heat-resistant sizing agent, which not only enables the composite material after the carbon fiber and the resin matrix are combined to have a higher interface bonding strength, but also ensures that the carbon fiber and the resin matrix have both relatively excellent moisture- and heat-resistant stability, and can also increase the impact resistance of the composite material.

[0056] According to a fourth aspect of the present invention, there is provided a composite material comprising an epoxy resin matrix, and carbon fibers bonded to the epoxy resin matrix;

[0057] The carbon fiber includes the carbon fiber described above.

[0058] The composite material provided by the present invention not only has high interface bonding strength, but also has relatively excellent moisture and heat resistance stability and better impact resistance.

[0059] The present invention is further described below by way of examples. Unless otherwise specified, the materials in the examples were prepared according to existing methods or directly purchased from the market.

[0060] Example 1

[0061] This embodiment provides a heat and moisture resistant sizing agent, and the preparation method includes the following steps:

[0062] (a) mixing 10 parts by mass of a polyethylene oxide-modified epoxy resin (epoxy resin prepolymer), 10 parts by mass of a polyurethane-modified epoxy resin, and 30 parts by mass of a bisphenol fluorene epoxy resin to obtain a mixed solution;

[0063] (b) adding 50 parts of deionized water to the mixed solution obtained in step (a) and stirring and mixing at a speed of 2000 r / min for 5 minutes to obtain a moisture-heat resistant sizing agent.

[0064] Example 2

[0065] This embodiment provides a heat and moisture resistant sizing agent, and the preparation method includes the following steps:

[0066] (a) mixing 10 parts by mass of an acrylic acid-grafted modified epoxy resin (epoxy resin prepolymer), 20 parts by mass of a polyurethane-modified epoxy resin, and 20 parts by mass of a bis-o-cresol fluorene epoxy resin to obtain a mixed solution;

[0067] (b) adding 55 parts of deionized water to the mixed solution obtained in step (a) and stirring and mixing at a speed of 3000 r / min for 3 minutes to obtain a moisture-heat resistant sizing agent.

[0068] Example 3

[0069] This embodiment provides a heat and moisture resistant sizing agent, and the preparation method includes the following steps:

[0070] (a) stirring and mixing, by weight, 15 parts of a maleic anhydride graft-modified epoxy resin (epoxy resin prepolymer), 10 parts of a polyurethane-modified epoxy resin, and 25 parts of a bis-o-cresol fluorene epoxy resin to obtain a mixed solution;

[0071] (b) adding 50 parts of deionized water to the mixed solution obtained in step (a) and stirring and mixing at a speed of 2000 r / min for 5 minutes to obtain a moisture-heat resistant sizing agent.

[0072] Comparative Example 1

[0073] This comparative example provides a sizing agent, and the preparation method comprises the following steps:

[0074] 55 parts by mass of polyethylene oxide modified epoxy resin (epoxy resin prepolymer) and 55 parts of deionized water were stirred and mixed at a speed of 2000 r / min for 5 minutes to obtain a sizing agent.

[0075] Comparative Example 2

[0076] This comparative example provides a sizing agent, and the preparation method comprises the following steps:

[0077] (a) stirring and mixing 25 parts by mass of a maleic anhydride graft-modified epoxy resin (epoxy resin prepolymer) and 25 parts by mass of a bis-o-cresol fluorene epoxy resin to obtain a mixed solution;

[0078] (b) adding 50 parts of deionized water to the mixed solution obtained in step (a) and stirring and mixing at a speed of 2000 r / min for 5 minutes to obtain a sizing agent.

[0079] Comparative Example 3

[0080] This comparative example provides a sizing agent, and the preparation method comprises the following steps:

[0081] 40 parts by mass of bis-o-cresol fluorene epoxy resin and 5 parts of Span-80 (emulsifier) ​​were added to 55 parts of deionized water and stirred at a speed of 2000 r / min for 5 minutes to obtain a sizing agent.

[0082] Comparative Example 4

[0083] This comparative example provides a sizing agent, which differs from Example 1 only in that the mass fraction of the polyethylene oxide modified epoxy resin is 5 parts;

[0084] The remaining components, their proportions and preparation process are the same as those in Example 1.

[0085] In this comparative example, since the amount of polyethylene oxide modified epoxy resin (waterborne epoxy resin prepolymer) added was too small, resulting in poor emulsion stability, no sizing agent could be formed.

[0086] Comparative Example 5

[0087] This comparative example provides a sizing agent, which differs from Example 1 only in that the mass fraction of the polyethylene oxide modified epoxy resin is 25 parts;

[0088] The remaining components, their proportions and preparation process are the same as those in Example 1.

[0089] Comparative Example 6

[0090] This comparative example provides a sizing agent, which differs from Example 1 only in that the mass fraction of the polyurethane-modified epoxy resin is 5 parts;

[0091] The remaining components, their proportions and preparation process are the same as those in Example 1.

[0092] Comparative Example 7

[0093] This comparative example provides a sizing agent, which differs from Example 1 only in that the mass fraction of the polyurethane-modified epoxy resin is 25 parts;

[0094] The remaining components, their proportions and preparation process are the same as those in Example 1.

[0095] Test example

[0096] The performance of the sizing agents obtained in the examples and comparative examples was tested, and the results are shown in Table 1.

[0097] The test method is as follows: first, T700 carbon fiber is immersed in a sizing agent for 2 minutes, then the impregnated T700 carbon fiber is vacuum dried at high temperature, and then the sizing T700 carbon fiber is compounded with an epoxy resin film to form a prepreg. The prepreg is then cut, laid, and compression molded to obtain an epoxy resin-based carbon fiber composite material.

[0098] The obtained composite materials were subjected to impact strength tests and interlaminar shear tests in accordance with GBT 1043.2-2018 and ASTM D 2344 standards. Specifically, the impact strength and interlaminar shear strength of each composite material sample were first tested in a dry state at room temperature, and then the composite material samples were placed in 75°C water for 14 days, and then the interlaminar shear test was performed in accordance with ASTM D 2344 standard.

[0099] Table 1

[0100]

[0101] Referring to Table 1, it can be seen from the test results of Examples 1-3 and Comparative Example 1 that the introduction of fluorenyl epoxy resin into the sizing agent has a better resistance to moisture and heat than the composite material without the introduction of fluorenyl epoxy resin; the test results of Examples 1-3 and Comparative Example 2 show that the direct compounding of fluorenyl epoxy resin with epoxy resin prepolymer has an obviously insufficient impact strength compared with the introduction of polyurethane-modified epoxy resin; the test results of Examples 1-3 and Comparative Example 3 show that the compounding of fluorenyl epoxy resin with conventional emulsifier does not enhance the resistance to moisture and heat. Only after compounding with epoxy resin prepolymer and polyurethane-modified epoxy resin does the composite material have excellent resistance to moisture and heat.

[0102] At the same time, it can be seen from the test results of Example 1 and Comparative Examples 4-7 that too little or too much epoxy resin prepolymer or polyurethane modified epoxy resin will have an adverse effect on the overall performance of the composite material; it can be seen that the epoxy resin prepolymer, polyurethane modified epoxy resin and fluorene epoxy resin can only work effectively together within an appropriate dosage ratio range, so that the composite material has excellent moisture and heat stability and better impact strength.

[0103] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the above embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A heat and moisture resistant sizing agent, characterized in that: It is composed of the following components in parts by mass: 10 to 20 parts of epoxy resin prepolymer, 10 to 20 parts of polyurethane-modified epoxy resin with self-emulsifying properties, 20 to 30 parts of fluorene-based epoxy resin, and 50 to 60 parts of water; The epoxy resin prepolymer includes a water-based epoxy resin prepolymer; The waterborne epoxy resin prepolymer includes at least one of an etherification reaction type modified epoxy resin and a grafting reaction type ion group modified epoxy resin.

2. The heat and moisture resistant sizing agent according to claim 1, characterized in that The etherification reaction type modified epoxy resin includes at least one of polyethylene oxide modified epoxy resin and polypropylene oxide modified epoxy resin.

3. The heat and moisture resistant sizing agent according to claim 1, characterized in that The graft reaction type ion-modified epoxy resin includes at least one of an acrylic acid graft modified epoxy resin and a maleic anhydride graft modified epoxy resin.

4. The heat-and-humidity resistant sizing agent according to any one of claims 1 to 3, characterized in that The fluorene-based epoxy resin includes at least one of bisphenol fluorene epoxy resin and bis-o-cresol fluorene epoxy resin.

5. A method for preparing the heat and moisture resistant sizing agent according to any one of claims 1 to 4, characterized in that: The following steps are involved: The components are mixed in proportion to obtain the moisture and heat resistant sizing agent.

6. The preparation method according to claim 5, characterized in that The mixing process conditions include stirring at a rotation speed of 2000 r / min to 3000 r / min for 3 min to 5 min.

7. A carbon fiber, characterized in that It includes a carbon fiber matrix and a surface coating layer thereof; The coating layer is formed by the moisture-heat resistant sizing agent according to any one of claims 1 to 4.

8. A composite material, characterized in that comprising an epoxy resin matrix, and carbon fibers combined with the epoxy resin matrix; The carbon fiber includes the carbon fiber according to claim 7.

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