Sizing agent for carbon fiber, preparation method of sizing agent, carbon fiber and composite material

Abstract

The embodiment of the invention provides a sizing agent for carbon fibers, a preparation method of the sizing agent, the carbon fibers and a composite material, and relates to the technical field of preparation of high-performance carbon fibers. The sizing agent for the carbon fibers, disclosed by the embodiment of the invention, comprises the following components in parts by weight: 10-20 parts of aminophenol trifunctional epoxy resin; 20 to 30 parts of amino tetrafunctional epoxy resin; 10 to 20 parts of dihydroxy-terminated polyphenyl ether resin; 10 to 15 parts of an emulsifier; and 50-60 parts of water. According to the sizing agent for the carbon fiber, the preparation method of the sizing agent, the carbon fiber and the composite material, the heat resistance, the interface bonding performance and the impact resistance can be improved at the same time.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of high-performance carbon fiber preparation, in particular to a sizing agent for carbon fiber, a preparation method thereof, carbon fiber and a composite material. BACKGROUND

[0002] Carbon fiber reinforced polymer composite (CFRP) is used in high-performance structures, which can be used as structural materials and functional materials, and is increasingly applied in aerospace, construction machinery, energy development, sports equipment, transportation and other fields. Although carbon fiber reinforced polymer composite has the advantages of carbon fiber, due to the smooth surface of carbon fiber, the chemical inertness is large, and the active functional groups on the surface of carbon fiber are particularly few, which needs to be treated by fiber sizing to increase the active groups on the surface of carbon fiber, and to avoid pollution on the surface of carbon fiber, and to enhance the interfacial adhesion between carbon fiber and matrix resin.

[0003] However, most of the sizing agents for carbon fiber have poor heat resistance, which are prone to decomposition and deterioration when used in high temperature. At the same time, most of the composite materials have poor mechanical strength, mainly due to poor interfacial bonding performance, and especially poor impact resistance, which cannot meet the specific use requirements of the application end.

[0004] Therefore, a sizing agent for carbon fiber capable of improving heat resistance and mechanical properties at the same time is needed. SUMMARY

[0005] The purpose of the embodiments of the present application is to provide a sizing agent for carbon fiber, a preparation method thereof, carbon fiber and a composite material, which can improve heat resistance and interfacial bonding performance and impact resistance at the same time.

[0006] In a first aspect, the embodiments of the present application provide a sizing agent for carbon fiber, which comprises the following components in parts by weight: 10-20 parts of amino phenol trifunctional epoxy resin; 20-30 parts of amino tetrafunctional epoxy resin; 10-20 parts of double-end hydroxyl polyphenyl ether resin; 10-15 parts of polyoxyethylene ether type emulsifier; 50-60 parts of water.

[0007] In the above technical solution, the sizing agent for carbon fibers uses two high-functionality epoxy resins, i.e., amino-phenol tri-functional epoxy resin and amino tetra-functional epoxy resin, as main resin materials, to increase the reaction sites during curing, improve the reaction activity, increase the crosslinking density during curing, i.e., increase the crosslinking density of the cured product, thereby improving the heat resistance and mechanical strength (interfacial bonding performance and impact resistance). Specifically, each molecule of the amino-phenol tri-functional epoxy resin and the amino tetra-functional epoxy resin has multiple epoxy groups (high functionality), compared with the most common bisphenol A type epoxy resin (double functionality), the two epoxy resins used in the present application have more epoxy groups, i.e., more reaction sites; and the amino groups built-in the molecules of the two epoxy resins can directly participate in the epoxy group reaction, promoting the ring-opening reaction of the epoxy groups during curing, and a higher crosslinking density and aromatic density can be formed during the curing process, so that the cured product exhibits good heat resistance and mechanical strength.

[0008] Meanwhile, the double-end hydroxyl polyphenyl ether resin with excellent impact resistance is introduced into the sizing agent for carbon fibers, to greatly improve the impact resistance by virtue of the characteristics of the ether bond (-O-) and the end hydroxyl group (-OH) carried by itself.

[0009] In a possible implementation manner, the molecular structure formula of the amino-phenol tri-functional epoxy resin is as follows: ; The epoxy value of the amino-phenol tri-functional epoxy resin is 0.9-1.05 eg / 100g.

[0010] In the above technical solution, the amino-phenol tri-functional epoxy resin has high functionality and high epoxy value, so that the cured product exhibits good heat resistance and mechanical strength, and has good flexibility. Specifically, the epoxy value of the amino-phenol tri-functional epoxy resin is controlled within a certain range to ensure the high reaction activity of the resin; the amino groups built-in the molecule of the amino-phenol tri-functional epoxy resin can directly participate in the epoxy group reaction, and the phenolic hydroxyl groups are activated by hydrogen bond and catalyze the amino groups / other nucleophilic groups of the subsequent applied curing agent, the close synergistic effect of the amino groups and the phenolic hydroxyl groups in the molecule of the epoxy resin greatly promotes the ring-opening reaction of the epoxy groups during curing, and a higher crosslinking density and aromatic density can be formed during the curing process, so that the cured product exhibits good heat resistance and mechanical strength.

[0011] In a possible implementation manner, the molecular structure formula of the amino tetra-functional epoxy resin is as follows: ; The epoxy value of the amino tetra-functional epoxy resin is 0.7-0.95 eg / 100g.

[0012] In the technical solution, the amino tetrafunctional epoxy resin has high functionality and high epoxy value, so that the cured product has good heat resistance and mechanical strength. Specifically, the amino group in the molecule of the amino tetrafunctional epoxy resin can directly participate in the epoxy group reaction, promote the ring-opening reaction of the epoxy group during curing, and form high crosslinking density and aromatic density during the curing process, so that the cured product has good heat resistance and mechanical strength.

[0013] In a possible implementation, the structure of the double-end hydroxyl polyphenyl ether resin is as follows: ; The molecular weight of the double-end hydroxyl polyphenyl ether resin is greater than or equal to 1600 Mn, the functionality is greater than or equal to 1.85, and the hydroxyl content is greater than or equal to 10,000 ppm.

[0014] In the technical solution, the main chain of the double-end hydroxyl polyphenyl ether resin is formed by connecting rigid benzene rings through ether bonds (-O-). The ether bonds (-O-) connecting the benzene rings provide the freedom of rotation within the molecular chain. The flexibility of the bonds enables the molecular chain to locally twist, bend and stretch to a certain extent when subjected to external forces (such as impact forces), thereby absorbing and dissipating a portion of the impact energy. The double-end hydroxyl group of the double-end hydroxyl polyphenyl ether resin is the core structural feature of its excellent impact resistance. The hydroxyl groups (-OH) at both ends of the molecular chain have strong polarity and can form intermolecular hydrogen bonds with the oxygen atoms (ether bonds or hydroxyl groups at the other end) on adjacent molecular chains. When the material is impacted, these hydrogen bonds can be preferentially broken to absorb a large amount of impact energy. At the same time, the long molecular chains of the double-end hydroxyl polyphenyl ether resin are prone to physical entanglement. This entanglement network can effectively hinder the rapid expansion of cracks when the material is impacted. Therefore, the introduction of the double-end hydroxyl polyphenyl ether resin described above significantly improves the heat resistance, impact strength and fracture toughness of the composite material. The molecular weight, functionality and hydroxyl content of the resin are controlled within a certain range to ensure that the resin has excellent impact resistance.

[0015] In a possible implementation, the polyoxyethylene ether emulsifier includes at least one of a fatty alcohol polyoxyethylene ether, an isomeric tridecanol polyoxyethylene ether and an alkyl phenol polyoxyethylene ether.

[0016] In a possible implementation, the emulsion particle size of the sizing agent for carbon fibers is 300-500 nm, and the 5% thermal weight loss temperature is greater than 320℃.

[0017] In a second aspect, the embodiments of the present application provide a preparation method of the sizing agent for carbon fibers provided in the first aspect, which includes the following steps: The amino phenol trifunctional epoxy resin, the amino tetrafunctional epoxy resin, the double-end hydroxyl polyphenyl ether resin and the polyoxyethylene ether type emulsifier are mixed uniformly by stirring, and then water is added to obtain the sizing agent for carbon fibers by a phase inversion emulsification method.

[0018] In the technical scheme, the preparation method of the sizing agent for carbon fibers has simple and efficient process, high success rate and is suitable for industrial production.

[0019] In a possible implementation manner, the stirring and mixing method comprises: the temperature of stirring and mixing is 80-90 DEG C, the stirring and mixing rate is 800-1200 rmp, and the stirring and mixing time is 20-40 min. And / or, the phase inversion emulsification method comprises: the temperature is 85-95 DEG C, the stirring rate is 4000-6000 rmp, and the stirring time is 60-90 min.

[0020] In the technical scheme, the stirring and mixing adopts certain temperature, rate and time to make the double-end hydroxyl polyphenyl ether resin fully dissolved in the main material resin formed by the amino phenol trifunctional epoxy resin and the amino tetrafunctional epoxy resin.

[0021] In a third aspect, the embodiments of the present application provide a carbon fiber, comprising a carbon fiber substrate and a coating layer attached to the surface of the carbon fiber substrate, wherein the coating layer is formed by curing the sizing agent for carbon fibers provided in the first aspect, and the mass ratio of the coating layer is 0.5%-1.0%.

[0022] In the technical scheme, the carbon fiber substrate is subjected to surface treatment by the sizing agent for carbon fibers, thereby enhancing the heat resistance and mechanical strength.

[0023] In a fourth aspect, the embodiments of the present application provide a composite material, comprising an epoxy resin substrate and the carbon fiber provided in the third aspect, wherein the carbon fiber is combined with the epoxy resin substrate.

[0024] In the technical scheme, the carbon fiber is combined with the epoxy resin substrate, thereby not only having high interfacial bonding performance, but also having good impact resistance. DETAILED DESCRIPTION

[0025] In order to make the purpose, technical scheme and advantages of the embodiments of the present application more clear, the technical scheme in the embodiments of the present application will be clearly and completely described below. The specific conditions are not indicated in the embodiments, and the conventional conditions or the conditions recommended by the manufacturer are used. The reagents or instruments used are not indicated by the manufacturer, and are conventional products that can be purchased in the market.

[0026] It should be noted that "and / or" in the present application, such as "feature 1 and / or feature 2", means "feature 1" alone, "feature 2" alone, "feature 1" plus "feature 2", the three cases.

[0027] In addition, in the description of the present application, unless otherwise stated, the meaning of "multiple" in "one or more" refers to two or more; The range of "value a~value b" includes both end values "a" and "b", and "unit of measurement" in "value a~value b+unit of measurement" represents the "unit of measurement" of both "value a" and "value b".

[0028] The carbon fiber sizing agent and its preparation method, carbon fiber and composite material of the present application are described in detail below.

[0029] The present application provides a kind of carbon fiber sizing agent, by weight fraction, it includes the following components: Amino phenol trifunctional epoxy resin 10~20 parts; Amino tetrafunctional epoxy resin 20~30 parts; Double end hydroxyl polyphenyl ether resin 10~20 parts; Polyoxyethylene ether type emulsifier 10~15 parts; Water 50~60 parts.

[0030] Exemplarily, the carbon fiber sizing agent includes the following components by weight fraction: amino phenol trifunctional epoxy resin 10 parts, 12 parts, 14 parts, 16 parts, 18 parts, 20 parts or any intermediate value fraction between any two of the above values; Amino tetrafunctional epoxy resin 20 parts, 22 parts, 24 parts, 26 parts, 28 parts, 30 parts or any intermediate value fraction between any two of the above values; Double end hydroxyl polyphenyl ether resin 10 parts, 12 parts, 14 parts, 16 parts, 18 parts, 20 parts or any intermediate value fraction between any two of the above values; Polyoxyethylene ether type emulsifier 10 parts, 11 parts, 12 parts, 13 parts, 14 parts, 15 parts or any intermediate value fraction between any two of the above values; Water 50 parts, 52 parts, 53 parts, 55 parts, 56 parts, 58 parts, 60 parts or any intermediate value fraction between any two of the above values.

[0031] In this embodiment, two kinds of high-functionality epoxy resins, amino phenol trifunctional epoxy resin and amino tetrafunctional epoxy resin, are used as main resin to increase the reaction site during curing, improve the reaction activity and increase the crosslinking density, thereby improving the heat resistance and mechanical strength (interfacial bonding performance, impact resistance); At the same time, double end hydroxyl polyphenyl ether resin with excellent impact resistance is introduced into the carbon fiber sizing agent, which greatly improves the impact resistance due to the characteristics of ether bond (-O-) and end hydroxyl (-OH) it carries.

[0032] The functional groups of the amino-phenol trifunctional epoxy resin include amino groups, phenolic hydroxyl groups, and epoxy groups, and the corresponding resin monomer has three highly reactive epoxy groups (trifunctional groups). In some embodiments of the present application, the molecular structure of the amino-phenol trifunctional epoxy resin is: The molecular structure here refers to the structure of the resin monomer corresponding to the epoxy resin, which forms a three-dimensional network structure macromolecule, i.e., the amino-phenol trifunctional epoxy resin, by chemically reacting with a curing agent. The resin monomer includes tertiary amino functional groups, phenolic hydroxyl functional groups, and three highly reactive epoxy functional groups.

[0033] In some embodiments of the present application, the epoxy value of the amino-phenol trifunctional epoxy resin is 0.9-1.05 eg / 100g. For example, the epoxy value of the amino-phenol trifunctional epoxy resin is 0.9 eg / 100g, 0.92 eg / 100g, 0.95 eg / 100g, 0.97 eg / 100g, 1 eg / 100g, 1.03 eg / 100g, 1.05 eg / 100g, or an epoxy value between any two of the above values.

[0034] In the embodiments of the present application, the epoxy value (epoxy value) is the amount of substance of the epoxy groups contained in 100g of epoxy resin, and its relationship with the epoxy equivalent is epoxy value = 100 / epoxy equivalent. It is one of the most important indicators for identifying the properties of epoxy resin.

[0035] In this embodiment, the amino-phenol trifunctional epoxy resin has a high degree of functionality and a high epoxy value, so that the cured product exhibits good heat resistance and mechanical strength, and has good flexibility.

[0036] The functional groups of the amino-phenol trifunctional epoxy resin include amino groups, phenolic hydroxyl groups, and epoxy groups, and the corresponding resin monomer has three highly reactive epoxy groups (trifunctional groups). In some embodiments of the present application, the molecular structure of the amino-phenol trifunctional epoxy resin is: The molecular structure here refers to the structure of the resin monomer corresponding to the epoxy resin, which forms a three-dimensional network structure macromolecule, i.e., the amino-phenol trifunctional epoxy resin, by chemically reacting with a curing agent. The resin monomer includes tertiary amino functional groups, phenolic hydroxyl functional groups, and three highly reactive epoxy functional groups.

[0037] In some embodiments of the present application, the amino tetra-functional epoxy resin has an epoxy value of 0.7-0.95 eg / 100g. Illustratively, the amino tetra-functional epoxy resin has an epoxy value of 0.7 eg / 100g, 0.75 eg / 100g, 0.8 eg / 100g, 0.85 eg / 100g, 0.9 eg / 100g, 0.95 eg / 100g, or an epoxy value between any two of the aforementioned values.

[0038] In this embodiment, the amino tetra-functional epoxy resin has a high functionality and a high epoxy value, so that the cured product exhibits good heat resistance and mechanical strength.

[0039] In some embodiments of the present application, the structure of the double-end hydroxyl polyphenyl ether resin is: ; The double-end hydroxyl polyphenyl ether resin has a molecular weight of ≥1600 Mn, a functionality of ≥1.85, and a hydroxyl content of ≥10000 ppm.

[0040] In this embodiment, the double-end hydroxyl polyphenyl ether resin is a polyphenyl ether oligomer with hydroxyl groups at both ends of the molecular chain, which has the inherent properties of polyphenyl ether. It can be mixed in the liquid epoxy resin system, greatly improving the heat resistance, impact strength, and fracture toughness of the composite material.

[0041] In some embodiments of the present application, the polyoxyethylene ether emulsifier includes at least one of fatty alcohol polyoxyethylene ether, isomeric tridecanol polyoxyethylene ether, and alkyl phenol polyoxyethylene ether.

[0042] In some embodiments of the present application, the emulsion particle size of the sizing agent for carbon fibers is 300-500 nm, and the 5% thermal weight loss temperature is >320℃. The 5% thermal weight loss temperature refers to the temperature at which the sample loses 5% of its mass during heating using thermal gravimetric analysis technology.

[0043] Illustratively, the emulsion particle size of the sizing agent for carbon fibers is 300 nm, 350 nm, 400 nm, 450 nm, 500 nm, or a value between any two of the aforementioned values. The 5% thermal weight loss temperature of the sizing agent for carbon fibers is 325℃, 330℃, 335℃, or higher.

[0044] The present application also provides a preparation method of the sizing agent for carbon fibers of the foregoing embodiments, which includes the following steps: The amino phenol tri-functional epoxy resin, the amino tetra-functional epoxy resin, the double-end hydroxyl polyphenyl ether resin, and the polyoxyethylene ether emulsifier are mixed uniformly by stirring, and then water is added to obtain the sizing agent for carbon fibers by phase inversion emulsification.

[0045] In some embodiments of the present application, the method of stirring mixing includes: the temperature of stirring mixing is 80-90℃, the rate of stirring mixing is 800-1200rmp, and the time of stirring mixing is 20-40min. Exemplarily, the temperature of stirring mixing is 80℃, 82℃, 85℃, 87℃, 90℃, or any intermediate value between any two of the above-mentioned temperatures, the rate of stirring mixing is 800rmp, 900rmp, 1000rmp, 1100rmp, 1200rmp, or any intermediate value between any two of the above-mentioned rates, and the time of stirring mixing is 20min, 30min, 40min, or any intermediate value between any two of the above-mentioned times.

[0046] Phase inversion emulsification is an important technology for preparing emulsions (especially fine emulsions or nanoemulsions). Its core principle is to induce phase inversion of the system by changing the emulsification conditions (such as temperature, composition, etc.), thereby forming a stable emulsion of the desired type. In some embodiments of the present application, the phase inversion emulsification includes: the temperature is 85-95℃, the stirring rate is 4000-6000rmp, and the stirring time is 60-90min. Exemplarily, the temperature is 85℃, 90℃, 95℃, or any intermediate value between any two of the above-mentioned temperatures, the stirring rate is 4000rmp, 5000rmp, 6000rmp, or any intermediate value between any two of the above-mentioned rates, and the stirring time is 60min, 70min, 80min, 90min, or any intermediate value between any two of the above-mentioned times.

[0047] The present application also provides a carbon fiber, which comprises a carbon fiber substrate and a coating layer attached to the surface of the carbon fiber substrate, the coating layer being formed by curing the sizing agent for carbon fiber of the foregoing embodiments, and the mass fraction of the coating layer being 0.5%-1.0%.

[0048] The content of the sizing agent (i.e. the content of the coating layer) of the sized interfacial reinforced carbon fiber is 0.5%-1.0%. Exemplarily, the content of the coating layer of the sized interfacial reinforced carbon fiber can be, but is not limited to, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, or 1.0%.

[0049] In this embodiment, the content of the sizing agent (i.e. the content of the coating layer) on the sized interfacial reinforced carbon fiber is set to 0.5%-1.0%, which can adjust the hardness and fuzz of the carbon fiber, and achieve the balance between the process performance and the interfacial performance of the carbon fiber.

[0050] The present application also provides a composite material, which comprises an epoxy resin matrix and the carbon fiber of the foregoing embodiments, and the carbon fiber is combined with the epoxy resin matrix.

[0051] In this embodiment, the carbon fiber sizing agent provided by the embodiment of the present application is used to prepare a composite material with interlaminar shear strength > 110 MPa, high interface performance, and cantilever beam impact strength > 95 MPa, high impact resistance.

[0052] The features and performance of the present application are further described in detail below in conjunction with the embodiments.

[0053] Embodiment 1 The present embodiment provides a sizing agent for carbon fibers, which is prepared as follows: (1) Prepare each raw material component by mass fraction: amino phenol tri-functional epoxy resin 15 parts by mass, amino tetra-functional epoxy resin 25 parts by mass, double-end hydroxyl polyphenyl ether resin 15 parts by mass, and polyoxyethylene ether type emulsifier 13 parts by mass.

[0054] The amino phenol tri-functional epoxy resin is purchased from Shanghai Huayi Resin Co., Ltd., and its corresponding molecular structure formula is: The product information shows that the epoxy value of the amino phenol tri-functional epoxy resin is 0.9-1.05 eq / 100 g.

[0055] The amino tetra-functional epoxy resin is purchased from Shanghai Huayi Resin Co., Ltd., and its corresponding molecular structure formula is: The product information shows that the epoxy value of the amino tetra-functional epoxy resin is 0.7-0.95 eq / 100 g.

[0056] The double-end hydroxyl polyphenyl ether resin is purchased from Shaanxi Suobo Electronic Material Co., Ltd., and its structure formula is: The product information shows that the molecular weight of the double-end hydroxyl polyphenyl ether resin is ≥1600 Mn, the functionality is ≥1.85, and the hydroxyl content is ≥10000 ppm.

[0057] The polyoxyethylene ether type emulsifier is selected from fatty alcohol polyoxyethylene ether.

[0058] (2) Mix the above raw material components according to the above ratio, and heat to 85℃ for melting and stirring. The stirring rate is 1000rmp, the stirring time is 30min, and after uniform stirring, add water 50 parts by mass. Through phase inversion emulsification method, the temperature of the phase inversion emulsification method is 90℃, the stirring rate is 5000rmp, and the stirring time is 90min, to obtain the sizing agent emulsion.

[0059] Embodiment 2 The present embodiment provides a sizing agent for carbon fibers, which is prepared as follows: (1) Prepare each raw material component by mass fraction: amino phenol three functional epoxy resin 20 parts by mass, amino four functional epoxy resin 20 parts by mass, double end hydroxyl polyphenyl ether resin 10 parts by mass, polyoxyethylene ether type emulsifier 10 parts by mass.

[0060] Among them, the specific materials of amino phenol three functional epoxy resin, amino four functional epoxy resin, double end hydroxyl polyphenyl ether resin and polyoxyethylene ether type emulsifier are the same as those in Example 1.

[0061] (2) The above raw material components are mixed according to the above ratio, and heated to 85℃ for melting and stirring. The stirring rate is 1000rmp, the stirring time is 30min, and after stirring uniformly, 50 parts by mass of water is added. The phase inversion emulsification method is used, the temperature of the phase inversion emulsification method is 90℃, the stirring rate is 5000rmp, and the stirring time is 90min. The sizing agent emulsion is obtained.

[0062] Example 3 The present embodiment provides a sizing agent for carbon fiber, and the preparation process is as follows: (1) Prepare each raw material component by mass fraction: amino phenol three functional epoxy resin 10 parts by mass, amino four functional epoxy resin 30 parts by mass, double end hydroxyl polyphenyl ether resin 20 parts by mass, polyoxyethylene ether type emulsifier 15 parts by mass.

[0063] Among them, the specific materials of amino phenol three functional epoxy resin, amino four functional epoxy resin and double end hydroxyl polyphenyl ether resin are the same as those in Example 1; the polyoxyethylene ether type emulsifier is isomeric tridecanol polyoxyethylene ether.

[0064] (2) The above raw material components are mixed according to the above ratio, and heated to 85℃ for melting and stirring. The stirring rate is 1000rmp, the stirring time is 30min, and after stirring uniformly, 50 parts by mass of water is added. The phase inversion emulsification method is used, the temperature of the phase inversion emulsification method is 90℃, the stirring rate is 5000rmp, and the stirring time is 90min. The sizing agent emulsion is obtained.

[0065] Comparative Example 1 The present comparative example provides a sizing agent for carbon fiber, and the difference between the preparation process and Example 1 is that in step (1), bisphenol A epoxy resin (epoxy value is 0.4~0.55 eq / 100g, purchased from Shanghai Resin Factory Co., Ltd., model 634, 618) is used instead of amino phenol three functional epoxy resin, that is, bisphenol A epoxy resin and amino four functional epoxy resin are used as the main resin, and finally the sizing agent emulsion is obtained.

[0066] Comparative Example 2 The comparative example provides a sizing agent for carbon fibers, the preparation process of which is different from that of example 1 in that in step (1), bisphenol A epoxy resin (epoxy value 0.4-0.55 eq / 100 g) is used instead of amino tetrafunctional epoxy resin, i.e., bisphenol A epoxy resin and amino phenolic trifunctional epoxy resin are used as the main resin, and finally a sizing agent emulsion is obtained.

[0067] Comparative example 3 The comparative example provides a sizing agent for carbon fibers, the preparation process of which is different from that of example 1 in that in step (1), no double-end hydroxyl polyphenyl ether resin is added, and finally a sizing agent emulsion is obtained.

[0068] Comparative example 4 The comparative example provides a sizing agent for carbon fibers, the preparation process of which is different from that of example 1 in that in step (1), polysorbate-80 is selected as an emulsifier to replace fatty alcohol polyoxyethylene ether, and finally a sizing agent emulsion is obtained.

[0069] Comparative example 5 The comparative example provides a sizing agent for carbon fibers, the preparation process of which is different from that of example 1 in that in step (1), the following raw material components are prepared by mass fraction: amino phenolic trifunctional epoxy resin 5 parts by mass, amino tetrafunctional epoxy resin 30 parts by mass, double-end hydroxyl polyphenyl ether resin 15 parts by mass, and polyoxyethylene ether type emulsifier 13 parts by mass. The specific materials of the amino phenolic trifunctional epoxy resin, the amino tetrafunctional epoxy resin, the double-end hydroxyl polyphenyl ether resin, and the polyoxyethylene ether type emulsifier are the same as those of example 1. Finally, a sizing agent emulsion is obtained.

[0070] Comparative example 6 The comparative example provides a sizing agent for carbon fibers, the preparation process of which is different from that of example 1 in that in step (1), the following raw material components are prepared by mass fraction: amino phenolic trifunctional epoxy resin 20 parts by mass, amino tetrafunctional epoxy resin 15 parts by mass, double-end hydroxyl polyphenyl ether resin 15 parts by mass, and polyoxyethylene ether type emulsifier 13 parts by mass. The specific materials of the amino phenolic trifunctional epoxy resin, the amino tetrafunctional epoxy resin, the double-end hydroxyl polyphenyl ether resin, and the polyoxyethylene ether type emulsifier are the same as those of example 1. Finally, a sizing agent emulsion is obtained.

[0071] Test example 1 The test example tests the heat resistance and stability of the sizing agents for carbon fibers provided in examples 1-3 and comparative examples 1-6.

[0072] The heat resistance is tested by testing the thermal weight loss, wherein the thermal weight loss is tested according to the standard GB / T 27761; The stability test method is: take a proper amount of diluted sizing agent in a test tube, stand at room temperature for 72h, and observe whether it is layered (including no layering, slight layering, and obvious layering).

[0073] The results are shown in Table 1.

[0074] Table 1 Composition and test results of sizing agent for carbon fiber of Examples 1-3 and Comparative Examples 1-6

[0075] From the results in Table 1, it can be seen that the sizing agent emulsion particle size provided by Example 1 is 336 nm, no layering, and the sizing agent 5% thermal weight loss temperature is 335℃; the sizing agent emulsion particle size provided by Example 2 is 320 nm, no layering, and the sizing agent 5% thermal weight loss temperature is 330℃; the sizing agent emulsion particle size provided by Example 3 is 343 nm, no layering, and the sizing agent 5% thermal weight loss temperature is 333℃. Therefore, the sizing agent for carbon fiber provided by Examples 1-3 has good stability, no layering, and good heat resistance, and the 5% thermal weight loss temperature is >320℃.

[0076] In Comparative Example 1 and Comparative Example 2, after replacing the amino-phenol trifunctional epoxy resin and the amino-tetrafunctional epoxy resin with bisphenol A epoxy resin respectively, the heat resistance of the prepared sizing agent is significantly reduced; in Comparative Example 3, after not adding the double-end hydroxyl polyphenyl ether resin, the heat resistance of the prepared sizing agent is also reduced to a certain extent; in Comparative Example 4, after changing the type of emulsifier, the sizing agent is unstable and obvious layering occurs.

[0077] Therefore, it can be seen that the sizing agent for carbon fiber designed in the present application uses amino-phenol trifunctional epoxy resin, amino-tetrafunctional epoxy resin and double-end hydroxyl polyphenyl ether resin in a suitable weight to cooperate synergistically, and then cooperates with a suitable weight of polyoxyethylene ether type emulsifier (including at least one of fatty alcohol polyoxyethylene ether, isomeric tridecanol polyoxyethylene ether and alkyl phenol polyoxyethylene ether) to uniformly disperse the epoxy resin, thereby obtaining a sizing agent with high heat resistance and good stability.

[0078] Test Example 2 In this test example, the application performance of the sizing agent for carbon fiber provided by Examples 1-3 and Comparative Examples 1-6 is tested. The specific method is: the same carbon fiber (T700 carbon fiber) is immersed in the sizing agent for carbon fiber provided by Examples 1-3 and Comparative Examples 1-6 for 2min, and then the immersed T700 carbon fiber is subjected to high-temperature vacuum drying at a drying temperature of 200℃ for 10s to obtain sized carbon fiber; each sized carbon fiber is compounded with an epoxy resin film to prepare a prepreg; the prepreg is cut, laminated and molded in sequence to obtain a composite material, which is then detected.

[0079] The content of the sizing agent of the carbon fiber was tested by weighing the carbon fiber and the sized carbon fiber and calculating the weight gain percentage of the sized carbon fiber, i.e. the content of the sizing agent.

[0080] The mechanical properties of the composite material were tested according to GB / T 1843 and ASTM D 2344 standards.

[0081] The results are shown in Table 2.

[0082] Table 2 Application performance of the sizing agent for carbon fiber of Examples 1-3 and Comparative Examples 1-6

[0083] " / " means not tested.

[0084] According to the results in Table 2, the carbon fiber prepared by using the sizing agent for carbon fiber of Examples 1-3 has a composite material with an interlaminar shear strength > 110 MPa and a cantilever beam impact strength > 95 MPa, which has excellent interfacial bonding performance and impact resistance.

[0085] In Comparative Examples 1 and 2, the amino phenol tri-functional epoxy resin and the amino tetra-functional epoxy resin in the sizing agent are replaced by bisphenol A epoxy resin, respectively, which reduces the amount of active functional groups of the epoxy resin, resulting in a decrease in crosslinking density during the curing process. This is reflected in the interlaminar shear strength of the composite material, which is relatively reduced compared to the composite material of Example 1. In addition, the crosslinking density and aromatic density formed during the curing process are reduced, which leads to a decrease in the impact resistance of the composite material. In Comparative Example 3, the double-end hydroxyl polyphenyl ether resin is completely removed from the sizing agent, which significantly reduces the cantilever beam impact strength of the composite material. In Comparative Example 4, the prepared sizing agent is unstable, so the sizing test cannot be carried out, and therefore the composite material performance is not tested.

[0086] Comparative Examples 5-6 are outside the scope of the application in terms of the mass fraction of the amino phenol tri-functional epoxy resin and the amino tetra-functional epoxy resin. Comparative Example 5 is a case where the amount of the amino phenol tri-functional epoxy resin is too small relative to the amino tetra-functional epoxy resin, and Comparative Example 6 is a case where the amount of the amino tetra-functional epoxy resin is too small relative to the amino phenol tri-functional epoxy resin. The results show that the interlaminar shear strength and impact resistance of the composite material of Comparative Examples 5-6 are reduced to some extent compared to the composite material of Examples 1-3.

[0087] Therefore, the sizing agent for carbon fibers in the embodiment of the present application is prepared by mixing amino-phenol trifunctional epoxy resin, amino tetrafunctional epoxy resin and double-end hydroxyl polyphenyl ether resin in a proper weight ratio, and mixing a proper weight of polyoxyethylene ether emulsifier, and is suitable for improving the mechanical properties (interface performance + impact resistance) of the composite material, so that it can be used in a wider range.

[0088] In summary, the sizing agent for carbon fibers, the preparation method thereof, the carbon fibers and the composite material can simultaneously improve the heat resistance, the interface bonding performance and the impact resistance.

[0089] The above only describes the embodiments of the present application and is not used to limit the protection scope of the present application. For those skilled in the art, the present application can have various modifications and changes. 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 for carbon fiber, characterized in that, By weight, it comprises the following components: 10-20 parts of aminophenol trifunctional epoxy resin; 20-30 parts of amino tetrafunctional epoxy resin; 10-20 parts of hydroxyl-terminated polyphenylene ether resin; 10-15 parts of polyoxyethylene ether emulsifier; 50-60 parts water.

2. The sizing agent for carbon fiber according to claim 1, characterized in that, The molecular structural formula of the aminophenol trifunctional epoxy resin is: ; The epoxy value of the aminophenol trifunctional epoxy resin is 0.9~1.05eg / 100g.

3. The sizing agent for carbon fiber according to claim 1, characterized in that, The molecular structural formula of the amino tetrafunctional epoxy resin is: ; The epoxy value of the amino tetrafunctional epoxy resin is 0.7~0.95eg / 100g.

4. The sizing agent for carbon fiber according to claim 1, characterized in that, The structural formula of the double-hydroxyl-terminated polyphenylene ether resin is: ; The hydroxyl-terminated polyphenylene ether resin has a molecular weight ≥1600Mn, a functionality ≥1.85, and a hydroxyl content ≥10000ppm.

5. The sizing agent for carbon fiber according to claim 1, characterized in that, The polyoxyethylene ether type emulsifier includes at least one of fatty alcohol polyoxyethylene ether, isotridecyl alcohol polyoxyethylene ether, and alkylphenol polyoxyethylene ether.

6. The sizing agent for carbon fiber according to claim 1, characterized in that, The emulsion particle size of the sizing agent for carbon fiber is 300~500nm, and the 5% thermal weight loss temperature is >320℃.

7. A method for preparing a sizing agent for carbon fiber as described in any one of claims 1 to 6, characterized in that, It includes the following steps: According to the weight ratio, the aminophenol trifunctional epoxy resin, the amino tetrafunctional epoxy resin, the double-hydroxyl-terminated polyphenylene ether resin and the polyoxyethylene ether emulsifier are stirred and mixed evenly, and then water is added to obtain the sizing agent for carbon fiber by phase inversion emulsification.

8. The method for preparing the sizing agent for carbon fiber according to claim 7, characterized in that, The mixing method includes: a mixing temperature of 80~90℃, a mixing rate of 800~1200 rpm, and a mixing time of 20~40 min; And / or, the phase inversion emulsification method includes: a temperature of 85~95℃, a stirring rate of 4000~6000 rpm, and a stirring time of 60~90 min.

9. A type of carbon fiber, characterized in that, It includes a carbon fiber matrix and a coating layer attached to the surface of the carbon fiber matrix, wherein the coating layer is formed by curing a carbon fiber sizing agent as described in any one of claims 1 to 6, and the mass percentage of the coating layer is 0.5% to 1.0%.

10. A composite material, characterized in that, It includes an epoxy resin matrix and carbon fibers as described in claim 9, wherein the carbon fibers are bonded to the epoxy resin matrix.

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