Carbon fiber sizing agent and preparation method thereof, carbon fiber and composite material

Abstract

The invention provides a carbon fiber sizing agent and a preparation method thereof, a carbon fiber and a composite material, and belongs to the technical field of carbon fiber sizing agents. The carbon fiber sizing agent comprises the following components in parts by weight: 90-100 parts of amino modified epoxy resin, 10-20 parts of an emulsifier and 0.5-1 part of a flatting agent, wherein the amino modified epoxy resin is obtained by carrying out graft modification on epoxy resin by an amino compound; the average particle size of the carbon fiber sizing agent is less than or equal to 300nm, and the surface tension is less than or equal to 40mN / m. The carbon fiber sizing agent has smaller average particle size and lower surface tension, effectively improves the permeation and infiltration capacity to the surface of the carbon fiber, realizes homogeneous sizing and protection uniformity of the carbon fiber, improves the problems of cleavage, broken filaments and the like of the carbon fiber, and further improves the performance stability of the carbon fiber.

Description

Technical Field

[0001] The present application relates to the technical field of carbon fiber sizing agents, and in particular to a carbon fiber sizing agent and a preparation method thereof, carbon fibers, and composite materials. Background Art

[0002] Carbon fiber sizing agents are important additives in the carbon fiber production process, playing a key role in improving the performance and quality of carbon fibers. They can prevent fiber adhesion, reduce friction, protect fiber filaments from damage, and help obtain homogeneous carbon filaments. However, current carbon fiber sizing agents generally have insufficient wettability, resulting in poor sizing uniformity on the fiber surface, which in turn leads to problems such as split and fuzzy carbon fibers. Summary of the Invention

[0003] In response to the deficiencies in the prior art, the purpose of this application includes providing a carbon fiber sizing agent and its preparation method, and carbon fiber, which can achieve homogeneous sizing and protection uniformity of carbon fiber, improve problems such as splitting and hairiness of carbon fiber, and thereby improve the performance stability of carbon fiber.

[0004] In a first aspect, an embodiment of the present application provides a carbon fiber sizing agent, comprising the following components in parts by weight: 90 to 100 parts of an amino-modified epoxy resin, 10 to 20 parts of an emulsifier, and 0.5 to 1 part of a leveling agent; wherein the amino-modified epoxy resin is obtained by grafting modification of an epoxy resin with an amino compound; the average particle size of the carbon fiber sizing agent is ≤300 nm, and the surface tension is ≤40 mN / m. In the above technical solution, by using an amino-modified epoxy resin with high hydrophilicity, combined with an emulsifier and a smaller weight portion of a leveling agent, the carbon fiber sizing agent has better wettability, lower average particle size and surface tension, with an average particle size of ≤300nm and a surface tension of ≤40mN / m, thereby effectively improving the penetration and wetting ability of the carbon fiber surface, achieving homogeneous sizing and protection uniformity of the carbon fiber, improving problems such as splitting and hairiness of the carbon fiber, and thereby improving the performance stability of the carbon fiber.

[0005] Among them, the amino group in the amino-modified epoxy resin has strong polarity and reactivity, and can form hydrogen bonds or chemical bonds with groups such as hydroxyl and carboxyl groups on the surface of carbon fibers, thereby enhancing the interfacial bonding between the sizing agent and the fiber. In addition, the amino group can react with the epoxy groups in the subsequent composite material matrix (such as the epoxy resin matrix) to form chemical crosslinks, thereby achieving interfacial bridging of the "fiber-sizing agent-matrix" and solving the problem of weak interfacial bonding caused by the inertness of the carbon fiber surface. The emulsifier enables the amino-modified epoxy resin to disperse into small and uniform emulsion droplets, maintaining the high stability of the sizing agent system. The leveling agent can improve the wettability of the sizing agent emulsion on the carbon fiber surface by reducing the surface tension of the sizing agent emulsion, promote the rapid penetration of the emulsion into the gaps between the monofilaments, avoid "shrinkage" and "agglomeration" caused by excessive surface tension, and ensure that the sizing layer is evenly spread on the surface of each monofilament to form a film of uniform thickness.

[0006] In some embodiments, the amino compound includes at least one of diethanolamine or diisopropanolamine.

[0007] In the above technical solution, diethanolamine or diisopropanolamine contains both amino groups (secondary amine groups) that react with epoxy groups and polar hydroxyl groups, and the molecular chain also has a certain degree of flexibility. The amino groups are used to graft the epoxy resin, while the hydroxyl groups also enhance hydrophilicity, compatibility, and flexibility.

[0008] In some embodiments, the epoxy value of the epoxy resin is 0.40 mol / 100 g to 0.87 mol / 100 g.

[0009] In the above technical solution, an epoxy resin with a moderate epoxy value is used. After grafting modification, the hydrophilic groups (such as hydroxyl groups and amino groups) can form hydrogen bonds or electrostatic interactions with the hydroxyl groups and carboxyl groups on the surface of the carbon fiber. Moreover, due to the moderate epoxy value, the grafted polar groups are evenly distributed, and a continuous and tight adsorption film can be formed on the fiber surface. Moreover, the resin molecular weight corresponding to the epoxy resin is relatively short, and it can flexibly fit the carbon fiber surface to further enhance the adsorption force. In addition, the epoxy value is in a moderate range, which makes it difficult to over-crosslink after the grafting reaction, and the products are mostly linear or low-branched structures, and the sizing agent emulsion has good stability.

[0010] In some embodiments, the emulsifier includes at least one of fatty alcohol polyoxyethylene ether, fatty amine polyoxyethylene ether, or alkylphenol polyoxyethylene ether.

[0011] In the above technical solution, the above-mentioned non-ionic emulsifiers are used, and their molecular structures contain both "hydrophobic groups" (hydrophobic chains of fatty alcohols / amines / alkylphenols) and "hydrophilic groups" (polyoxyethylene ether chains). Through the interface adsorption of "the hydrophobic end anchoring the epoxy resin (non-polar / weakly polar) and the hydrophilic end facing the aqueous phase", the oil-water interfacial tension is reduced, and the amino-modified epoxy resin is dispersed into stable small droplets (the emulsion particle size is small and uniform, and not easy to coalesce), ensuring the stability of the sizing agent during storage and use. In addition, since epoxy resin matrix is ​​usually used in carbon fiber / resin composites, the polyoxyethylene ether chains in the above-mentioned emulsifiers can also match with epoxy resin (containing polar groups such as ether bonds and hydroxyl groups) through hydrogen bonds or polar interactions to form interfacial bridges, thereby enhancing the adhesion between the carbon fiber and the resin matrix, and thus improving the mechanical properties of the composite material.

[0012] In addition, by using amino-modified epoxy resin in combination with the above-mentioned emulsifier, the polyoxyethylene ether chain can also combine with the amino group through hydrogen bonds, and at the same time the hydrophobic chain is affinity with the non-polar part of the resin, thereby further enhancing the emulsification stability of the sizing agent and further enhancing the sizing uniformity.

[0013] In some embodiments, the leveling agent includes at least one of polyether-modified polysiloxane, polymethylphenylsiloxane, polyether polyester-modified organosiloxane, or alkyl-modified organosiloxane.

[0014] In the above technical solution, compared to the direct use of epoxy resin, the amino-modified epoxy resin used in this application increases its polarity, leading to an increase in the surface tension of the sizing agent system. The use of the above-mentioned silicone leveling agent can effectively reduce the surface tension of the sizing agent, enhance wettability, promote the leveling and spreading of the sizing agent, optimize interfacial compatibility, and improve the density of the sizing layer, thereby further improving the uniformity and stability of the sizing layer and reducing problems such as linting. In addition, the polar groups (polyether, polyester) in the above-mentioned leveling agent can also form hydrogen bonds with the amino groups in the amino-modified epoxy resin, thereby improving the compatibility between the two and effectively avoiding leveling agent failure or interfacial interference caused by polarity differences.

[0015] In a second aspect, an embodiment of the present application also provides a method for preparing a carbon fiber sizing agent, comprising the following steps: mixing an amino-modified epoxy resin, an emulsifier, and a leveling agent in parts by weight, adding water for emulsification and phase transfer, and obtaining a carbon fiber sizing agent.

[0016] In the above technical solution, this application uses a highly hydrophilic amino-modified epoxy resin in combination with an emulsifier and a leveling agent. During mixing, the emulsifier adsorbs on the surface of the resin particles, preventing them from agglomerating through steric hindrance and charge repulsion. During the phase transition from oil-in-water to oil-in-water emulsion (from oil-in-water emulsion), the emulsifier further reduces the oil-water interfacial tension, dispersing the resin into small droplets and ultimately forming a stable aqueous emulsion. This method is simple and environmentally friendly, and the aqueous emulsion imparts good fluidity to the sizing agent, which, combined with the leveling agent, allows it to evenly penetrate and spread across the carbon fiber surface.

[0017] In some embodiments, the preparation method of the amino-modified epoxy resin includes the following steps: adding an ethanol solution of an amino compound to an ethanol solution of an epoxy resin at 50°C to 60°C, mixing for 0.5h to 1h, heating to 80°C to 90°C, and reacting for 3h to 5h to obtain an amino-modified epoxy resin; wherein the mass ratio of the epoxy resin to the amino compound is 100:(10~20).

[0018] In this technical solution, amino groups are introduced into the epoxy resin through a nucleophilic addition-ring-opening reaction between an amino compound and the epoxy groups (three-membered ring structure with high tension and easy ring opening) in the epoxy resin. By first mixing an ethanol solution of the amino compound and an ethanol solution of the epoxy resin at a relatively low temperature, the amino compound and the epoxy resin come into full contact, forming a homogeneous solution. This allows for a uniform, gentle, and controllable reaction. Further heating promotes complete reaction and improves efficiency. Furthermore, by maintaining an appropriate mass ratio of the epoxy resin to the amino compound, the epoxy groups react fully, preventing residual epoxy groups from causing subsequent self-polymerization.

[0019] In a third aspect, an embodiment of the present application further provides a carbon fiber, which is sizing-treated with the carbon fiber sizing agent provided in the first aspect of the present application.

[0020] In the above technical solution, the carbon fibers treated with the carbon fiber sizing agent of the present application have good mechanical properties while significantly improving problems such as surface splitting and fuzz. The tensile strength of the carbon fibers is greater than 5150 MPa, and the amount of fuzz is less than 2.5 mg / 50 m.

[0021] In some embodiments, after sizing treatment, the content of the carbon fiber sizing agent in the carbon fiber is 0.9 wt % to 1.1 wt %.

[0022] In the above technical solution, by using the carbon fiber sizing agent provided in this application, when the content is 0.9wt%~1.1wt%, a uniform and stable film layer can be formed on the carbon fiber surface, so that the carbon fiber has good mechanical properties while problems such as surface splitting and hairiness are significantly improved.

[0023] In a fourth aspect, an embodiment of the present application further provides a composite material comprising an epoxy resin matrix and the carbon fiber provided in the third aspect.

[0024] In the above technical solution, in this application, carbon fibers treated with a carbon fiber sizing agent are combined with an epoxy resin matrix to obtain a composite material, wherein the carbon fibers have high tensile strength and low surface fuzziness, and further combined with the surface having amino groups that can react with epoxy groups in the epoxy resin matrix to form chemical crosslinks, thereby effectively improving the interfacial bonding between the carbon fibers and the epoxy resin matrix, thereby making the composite material have good mechanical properties (such as interlaminar shear strength). DETAILED DESCRIPTION

[0025] To make the purpose, technical solutions and advantages of the examples of the present application clearer, the technical solutions in the examples of the present application will be described clearly and completely below. Where specific conditions are not specified in the examples, conventional conditions or conditions recommended by the manufacturer are used. Where the manufacturer of the reagents or instruments is not specified, they are all conventional products that can be purchased commercially.

[0026] Carbon fiber sizing agents are important additives in the carbon fiber production process. They play a key role in improving the performance and quality of carbon fibers. They can prevent fiber adhesion, reduce friction, protect fiber filaments from damage, and help obtain homogeneous carbon filaments. The sizing agent needs to form a uniform film on the carbon fiber surface to play a role in homogeneous protection. However, the particle size of current carbon fiber sizing agents is generally above 500nm, and the surface tension of the emulsion is above 40mN / m. In actual production applications, there are still problems such as insufficient wettability resulting in poor sizing uniformity on the fiber surface, causing problems such as splitting and hairy carbon fibers.

[0027] Based on this, the first aspect of the embodiment of the present application proposes a carbon fiber sizing agent, comprising the following components in parts by weight: 90 to 100 parts of amino-modified epoxy resin, 10 to 20 parts of emulsifier, and 0.5 to 1 part of leveling agent; wherein, the amino-modified epoxy resin is obtained by grafting modification of epoxy resin with amino compounds; the average particle size of the carbon fiber sizing agent is ≤300 nm, and the surface tension is ≤40 mN / m.

[0028] As an example, in the carbon fiber sizing agent, the weight proportion of the amino-modified epoxy resin is 90 parts, 95 parts, 100 parts or an intermediate value between any two of the above values; the weight proportion of the emulsifier is 10 parts, 12 parts, 15 parts, 18 parts, 20 parts or an intermediate value between any two of the above values; the weight proportion of the leveling agent is 0.5 parts, 0.6 parts, 0.7 parts, 0.8 parts, 1 part or an intermediate value between any two of the above values.

[0029] It should be noted that the carbon fiber sizing agent is an aqueous emulsion system. The average particle size of the carbon fiber sizing agent refers to the average diameter of the emulsified droplets in the carbon fiber sizing agent. The smaller the average particle size and the more uniform the distribution, the better the dispersion of the particles in water, the less affected by gravity, and the less likely they are to settle or stratify. In addition, a smaller average particle size range is conducive to the formation of a uniform and dense film layer after sizing. The surface tension of the carbon fiber sizing agent refers to the force of the liquid surface resisting expansion. It is the primary factor that determines the adsorption capacity and effect of the sizing agent on carbon fiber. When the surface tension of the sizing agent is less than the surface energy of the carbon fiber, it can spontaneously spread on the carbon fiber surface to form a uniform coverage.

[0030] As an example, the average particle size of the carbon fiber sizing agent is 100 nm, 150 nm, 200 nm, 250 nm, 300 nm or an intermediate value between any two of the above values; the surface tension of the carbon fiber sizing agent is 30 mN / m, 32 mN / m, 35 mN / m, 38 mN / m, 40 mN / m or an intermediate value between any two of the above values.

[0031] Furthermore, the average particle size of the carbon fiber sizing agent is 100 nm to 300 nm; and the surface tension is 30 mN / m to 40 mN / m.

[0032] The present application uses an amino-modified epoxy resin with high hydrophilicity, in combination with an emulsifier and a leveling agent with a small weight portion, so that the carbon fiber sizing agent has good wettability, low average particle size and surface tension, with an average particle size of ≤300nm and a surface tension of ≤40mN / m, thereby effectively improving the penetration and wetting ability of the carbon fiber surface, achieving homogeneous sizing and protection uniformity of the carbon fiber, improving problems such as splitting and hairiness of the carbon fiber, and thereby improving the performance stability of the carbon fiber.

[0033] Among them, the amino group in the amino-modified epoxy resin has strong polarity and reactivity, and can form hydrogen bonds or chemical bonds with groups such as hydroxyl and carboxyl groups on the surface of carbon fibers, thereby enhancing the interfacial bonding between the sizing agent and the fiber. In addition, the amino group can react with the epoxy groups in the subsequent composite material matrix (such as the epoxy resin matrix) to form chemical crosslinks, thereby achieving interfacial bridging of the "fiber-sizing agent-matrix" and solving the problem of weak interfacial bonding caused by the inertness of the carbon fiber surface. The emulsifier allows the amino-modified epoxy resin to be dispersed in small and uniform emulsion droplets, maintaining the high stability of the sizing agent system. The leveling agent can improve the wettability of the sizing agent emulsion on the carbon fiber surface by reducing the surface tension of the sizing agent emulsion, promote the rapid penetration of the emulsion into the gaps between the monofilaments, avoid "shrinkage" and "agglomeration" caused by excessive surface tension, and ensure that the sizing layer is evenly spread on the surface of each monofilament to form a film of uniform thickness.

[0034] The following examples are combined to describe in detail the carbon fiber sizing agent, its preparation method and properties in this application. It should be understood that these examples are only used to illustrate this application and are not intended to limit the scope of this application.

[0035] The present invention provides a method for preparing a carbon fiber sizing agent, comprising the following steps: S1. Add an ethanol solution of an amino compound to an ethanol solution of an epoxy resin at 50°C to 60°C, mix for 0.5 to 1 hour, then heat to 80°C to 90°C and react for 3 to 5 hours to obtain an amino-modified epoxy resin. The mass ratio of the epoxy resin to the amino compound is 100:(10-20).

[0036] As an example, the mixing temperature is 50°C, 52°C, 55°C, 58°C, 60°C or an intermediate value between any two of the above values; the mixing time is 0.5h, 0.6h, 0.8h, 1h or an intermediate value between any two of the above values; the temperature for heating the reaction is 80°C, 82°C, 85°C, 88°C, 90°C or an intermediate value between any two of the above values; the reaction time is 3h, 4h, 5h or an intermediate value between any two of the above values; the mass ratio of the epoxy resin to the amino compound is 100:10, 100:15, 100:18, 100:20 or an intermediate value between any two of the above values.

[0037] In some embodiments, the amino compound includes at least one of diethanolamine or diisopropanolamine.

[0038] In some embodiments, the epoxy resin has an epoxy value of 0.40 mol / 100 g to 0.87 mol / 100 g. For example, the epoxy resin has an epoxy value of 0.40 mol / 100 g, 0.50 mol / 100 g, 0.60 mol / 100 g, 0.70 mol / 100 g, 0.85 mol / 100 g, or an intermediate value between any two of the above values. For example, the epoxy resin may be at least one of AG80, E51, E44, 634, and 370. S2, mixing the amino-modified epoxy resin, the emulsifier and the leveling agent according to parts by weight, adding water for emulsification and phase inversion, and obtaining a carbon fiber sizing agent.

[0039] In some embodiments, the emulsifier includes at least one of fatty alcohol polyoxyethylene ether, fatty amine polyoxyethylene ether, or alkylphenol polyoxyethylene ether. For example, the fatty alcohol polyoxyethylene ether may be at least one of AEO-3, AEO-7, AEO-15, and AEO-20; the fatty amine polyoxyethylene ether may be at least one of AC-1202, NPB-15, and AC-1810; and the alkylphenol polyoxyethylene ether may be at least one of NP-10, OP-8, OP-9, and OP-10.

[0040] In some embodiments, the leveling agent includes at least one of polyether-modified polysiloxane, polymethylphenylsiloxane, polyether polyester-modified organosiloxane, or alkyl-modified organosiloxane. Further, the leveling agent includes at least one of polyether-modified polysiloxane or polyether polyester-modified organosiloxane.

[0041] As an example, the polyether-modified polysiloxane may be at least one of BYK-333, BYK-348, BYK-377, and the polyether polyester-modified organosiloxane may be at least one of KP-366, MONENG-1070 / 1071, and SP-963.

[0042] The present application also provides a carbon fiber, which is sizing-treated with the carbon fiber sizing agent provided in the first aspect of the present application.

[0043] It is understandable that the present application does not limit the method of sizing treatment, and the sizing treatment can be performed using methods and equipment known in the art.

[0044] In some embodiments, the sizing treatment method may include the following steps: immersing the carbon fiber in a carbon fiber sizing agent, and drying after sizing.

[0045] In some embodiments, after sizing, the carbon fiber has a carbon fiber sizing agent content of 0.9 wt % to 1.1 wt %. For example, the carbon fiber sizing agent content is 0.90 wt %, 0.95 wt %, 0.98 wt %, 1.05 wt %, 1.1 wt %, or an intermediate value between any two of the above values.

[0046] In addition, an embodiment of the present application also provides a composite material, including an epoxy resin matrix and the above-mentioned carbon fiber.

[0047] It is understood that the present application does not limit the preparation method of the composite material, and the composite material can be prepared using methods and equipment known in the art. As an example, an epoxy resin and a curing agent are mixed to form a resin mixture, and the sized carbon fiber is impregnated with the resin mixture and cured to form a carbon fiber composite material.

[0048] Example The carbon fiber sizing agent and its preparation method of the present application are described in detail below with reference to specific embodiments.

[0049] The sources of the main raw materials used in the examples and comparative examples of the present application are shown in Table 1: Table 1 Sources of main raw materials in Examples and Comparative Examples

[0050] Example 1 This embodiment provides a carbon fiber sizing agent, the preparation method of which includes the following steps: (1) Epoxy resin E44 and diethanolamine were fully dissolved in ethanol. The diethanolamine ethanol solution was slowly added dropwise to the epoxy resin ethanol solution at 50°C and stirred for 0.5 h. The temperature was then raised to 85°C and the reaction was continued for 4 h to obtain an amino-modified epoxy resin. The epoxy resin was 100 parts, with an epoxy value of 0.40-0.47 mol / 100 g, and the diethanolamine was 10 parts. (2) 100 parts of the above-mentioned amino-modified epoxy resin, 10 parts of the emulsifier fatty alcohol polyoxyethylene ether, and 0.5 parts of the leveling agent polyether-modified polysiloxane are mixed uniformly according to the proportions, and then water is added for phase inversion and emulsification to obtain a carbon fiber sizing agent emulsion.

[0051] Example 2 This embodiment provides a carbon fiber sizing agent, the preparation method of which includes the following steps: (1) Epoxy resin E51 and diethanolamine were fully dissolved in ethanol. The diethanolamine ethanol solution was slowly added dropwise to the epoxy resin ethanol solution at 50°C and stirred for 0.5 h. The temperature was then raised to 85°C and the reaction was continued for 3.5 h to obtain an amino-modified epoxy resin. The epoxy resin was 100 parts, with an epoxy value of 0.50-0.54 mol / 100 g, and the diethanolamine was 15 parts. (2) 100 parts of the above-mentioned amino-modified epoxy resin, 15 parts of the emulsifier fatty amine polyoxyethylene ether, and 1 part of the leveling agent polyether-modified polysiloxane are mixed uniformly according to the proportions, and then water is added for phase inversion and emulsification to obtain a carbon fiber sizing agent emulsion.

[0052] Example 3 This embodiment provides a carbon fiber sizing agent, the preparation method of which includes the following steps: (1) Epoxy resin 370 and diisopropanolamine were fully dissolved in ethanol. The diisopropanolamine ethanol solution was slowly added dropwise to the epoxy resin ethanol solution at 50°C and stirred for 0.5 h. The temperature was then raised to 90°C and the reaction was continued for 4 h to obtain an amino-modified epoxy resin. The epoxy resin was 100 parts, with an epoxy value of 0.58-0.61 mol / 100 g, and the diethanolamine was 20 parts. (2) 100 parts of the above-mentioned amino-modified epoxy resin, 20 parts of the emulsifier alkylphenol polyoxyethylene ether, and 0.8 parts of the leveling agent polyether polyester modified organic silicone are mixed uniformly according to the proportions, and then water is added for phase inversion and emulsification to obtain a carbon fiber sizing agent emulsion.

[0053] Example 4 (1) Epoxy resin AG-80 and diethanolamine were fully dissolved in ethanol. The diethanolamine ethanol solution was slowly added dropwise to the epoxy resin ethanol solution at 50°C and stirred for 0.5 h. The temperature was then raised to 85°C and the reaction was continued for 4 h to obtain an amino-modified epoxy resin. The epoxy resin was 100 parts, with an epoxy value of 0.80-0.87 mol / 100 g, and the diethanolamine was 10 parts. (2) 100 parts of the above-mentioned amino-modified epoxy resin, 10 parts of the emulsifier fatty amine polyoxyethylene ether, and 0.6 parts of the leveling agent polyether-modified polysiloxane are mixed uniformly according to the proportions, and then water is added for phase inversion and emulsification to obtain a carbon fiber sizing agent emulsion.

[0054] Comparative Example 1 This comparative example provides a carbon fiber sizing agent, the preparation method of which differs from that of Example 1 only in that 5 parts of an emulsifier, fatty alcohol polyoxyethylene ether, is used in step (2).

[0055] Comparative Example 2 This comparative example provides a carbon fiber sizing agent, the preparation method of which differs from that of Example 1 only in that 30 parts of an emulsifier, fatty alcohol polyoxyethylene ether, is used in step (2).

[0056] Comparative Example 3 This comparative example provides a carbon fiber sizing agent, the preparation method of which differs from that of Example 1 only in that step (1) is not included, and epoxy resin is used in place of amino-modified epoxy resin in step (2).

[0057] Comparative Example 4 This comparative example provides a carbon fiber sizing agent, the preparation method of which differs from that of Example 1 only in that no leveling agent is used in step (2).

[0058] The raw material compositions of the carbon fiber sizing agents in the above examples and comparative examples are shown in Table 2.

[0059] Table 2 Composition of carbon fiber sizing agents in Examples and Comparative Examples (Unit: parts by weight)

[0060] Test example The carbon fibers were sized and dried using a carbon fiber sizing agent. The carbon fiber sizing agents prepared in the above examples and comparative examples and the corresponding sizing-treated carbon fibers were subjected to performance tests. The test results are shown in Table 3. The specific test methods are as follows: 1. Carbon fiber sizing agent (1) Average particle size: The test was performed using the dynamic light scattering (DLS) method in accordance with the GB / T 29024.1-2012 “Particle size analysis - Dynamic light scattering method” test standard.

[0061] (2) Surface tension: The test was carried out using the hanging drop method in accordance with the test standard GB / T 22237-2008 “Determination of surface tension of surfactants”.

[0062] 2. Carbon fiber (1) Sizing agent content in carbon fiber: Use the burning method in GB / T 26752-2011 "Test method for sizing agent content in carbon fiber": burn in air at 550℃±20℃ to constant weight, and calculate the weight loss.

[0063] (2) Hair quantity: Test according to the hair quantity determination method in "Carbon Fiber and Graphite Fiber".

[0064] (3) Tensile strength: Tested in accordance with GB / T 3362-2017.

[0065] Table 3 Performance test results of the examples and comparative examples

[0066] Combining Table 2 and Table 3, it can be seen that compared with Comparative Examples 1 to 4, the carbon fiber sizing agent prepared in Examples 1 to 4 of the present application has a smaller average particle size and lower surface tension, with an average particle size of ≤300 nm and a surface tension of ≤40 mN / m. The corresponding carbon fiber prepared has a lower amount of fuzz while having a smaller sizing agent content and maintaining a higher tensile strength.

[0067] It can be seen from the performance test results of Example 1 and Comparative Examples 1 and 2 that when the amount of emulsifier is too low, it cannot be effectively emulsified and dispersed, so that the average particle size and surface tension of the sizing agent are significantly increased, and the corresponding amount of carbon fiber fuzz increases and the tensile strength decreases; when it is too high, the interface of the emulsion system is unstable, resulting in a significant increase in the average particle size of the carbon fiber sizing agent and an increase in the surface tension.

[0068] It can be seen from the performance test results of Example 1 and Comparative Example 3 that, compared with the use of epoxy resin, the use of hydrophilically modified amino-modified epoxy resin in Example 1 can effectively reduce the emulsion particle size and reduce the surface tension, thereby significantly reducing the amount of fuzz on the carbon fiber.

[0069] From the performance test results of Example 1 and Comparative Example 4, it can be seen that by using a leveling agent in combination with an amino-modified epoxy resin and an emulsifier, the stability of the emulsion can be further improved, the surface tension can be reduced, the wettability of the sizing agent on the fiber can be improved, and the fuzz level of the carbon fiber can be improved.

[0070] The embodiments described above are part of the embodiments of the present application, rather than all of the embodiments. The detailed description of the embodiments of the present application is not intended to limit the scope of the present application for protection, but merely represents selected embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of this application.

Claims

1. A carbon fiber sizing agent, characterized in that: The invention comprises the following components in parts by weight: 90-100 parts of amino-modified epoxy resin, 10-20 parts of emulsifier, and 0.5-1 part of leveling agent; The amino-modified epoxy resin is obtained by grafting an amino compound onto an epoxy resin; the average particle size of the carbon fiber sizing agent is ≤300 nm, and the surface tension is ≤40 mN / m.

2. The carbon fiber sizing agent according to claim 1, characterized in that The amino compound includes at least one of diethanolamine and diisopropanolamine.

3. The carbon fiber sizing agent according to claim 1, characterized in that The epoxy value of the epoxy resin is 0.40 mol / 100 g to 0.87 mol / 100 g.

4. The carbon fiber sizing agent according to claim 1, characterized in that The emulsifier includes at least one of fatty alcohol polyoxyethylene ether, fatty amine polyoxyethylene ether or alkylphenol polyoxyethylene ether.

5. The carbon fiber sizing agent according to claim 1, characterized in that The leveling agent includes at least one of polyether-modified polysiloxane, polymethylphenylsiloxane, polyether polyester-modified organic siloxane or alkyl-modified organic siloxane.

6. A method for preparing a carbon fiber sizing agent according to any one of claims 1 to 5, characterized in that: The following steps are involved: The amino modified epoxy resin, emulsifier and leveling agent are mixed according to parts by weight, and water is added to perform emulsification and phase inversion to obtain the carbon fiber sizing agent.

7. The preparation method according to claim 6, characterized in that The preparation method of the amino-modified epoxy resin comprises the following steps: Adding the ethanol solution of the amino compound to the ethanol solution of the epoxy resin at 50° C. to 60° C., mixing for 0.5 h to 1 h, heating to 80° C. to 90° C., and reacting for 3 h to 5 h to obtain the amino-modified epoxy resin; Wherein, the mass ratio of the epoxy resin to the amino compound is 100:(10~20).

8. A carbon fiber, characterized in that The carbon fiber is sizing-treated with the carbon fiber sizing agent according to any one of claims 1 to 5.

9. The carbon fiber according to claim 8, characterized in that After sizing treatment, the content of the carbon fiber sizing agent in the carbon fiber is 0.9 wt % to 1.1 wt %.

10. A composite material, characterized in that The invention comprises an epoxy resin matrix and carbon fibers as claimed in claim 8 or 9.

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