Sizing agent, preparation method and application thereof

Abstract

This invention relates to the field of sizing agents, and discloses a sizing agent, its preparation method, and its application. The sizing agent comprises a polymer, microfibers, a surfactant, and a solvent; wherein, based on the total mass of the sizing agent, the polymer content is 0.1-5 wt%, the microfiber content is 0.01-1 wt%, and the surfactant content is 0.1-5 wt%. The sizing agent provided by this invention can significantly improve the interfacial properties of sized carbon fiber composites, avoid fuzzing and fiber breakage caused by friction between carbon fibers, thereby giving the carbon fiber composites good wear resistance and improving their service life and performance stability.

Description

Technical Field

[0001] This invention relates to the field of sizing agents, specifically to a sizing agent, its preparation method, and its application. Background Technology

[0002] Compared to metallic materials, carbon fiber reinforced composites offer numerous advantages, such as strength, lightness, corrosion resistance, fatigue resistance, and the ability to be customized to specific industrial performance requirements. However, because carbon fiber reinforced composites consist of two distinct materials (rigid fibers and a soft matrix or binder), they are susceptible to strain damage. The interfacial phase between the two materials significantly impacts the overall mechanical properties of the composite, necessitating improvements.

[0003] Traditional carbon fiber sizing agents use epoxy resin and polyurethane as sizing slurries, and the sized carbon fibers are mainly used in epoxy resin composites for low-temperature applications. However, when these sizing agents are applied to high-temperature resistant composites such as polyimide and polyetheretherketone, traditional slurries are prone to degradation at high processing temperatures (>300℃) and high service temperatures, affecting the interfacial adhesion of the composites and thus reducing their mechanical properties at high temperatures. In recent years, researchers have begun to focus on the development of sizing agents suitable for high-temperature resistant carbon fiber composites. JP2014125688 formulated a high-temperature resistant solvent-based sizing agent by mixing polyimide with hydroxyl or carboxyl groups with epoxy resins such as bisphenol A glycidyl ether and phenolic glycidyl ether. US20140343218A1, CN103614923A, CN103174026A, and CN109265998A disclose a polyimide waterborne sizing agent formulated from a water-soluble polyamic acid salt synthesized from aromatic dianhydride and aromatic diamine. Polyimide sizing agents have a highly thermally stable aromatic main chain structure and a high degree of compatibility with high-temperature resistant resin matrices, which can effectively improve the temperature resistance and mechanical properties of carbon fiber reinforced composites in high-temperature environments.

[0004] However, the polyimide sizing agent has a rigid main chain structure, resulting in high stiffness of the sized carbon fibers. Furthermore, the polyimide sizing agent is difficult to distribute evenly on the carbon fiber surface, easily leading to localized agglomeration. In subsequent carbon fiber processing steps, due to the rigidity and rough surface of the carbon fibers, frequent friction between individual filaments and carbon fiber bundles causes fuzzing and filament breakage, affecting the performance of the carbon fiber composite material. Therefore, improving the abrasion resistance of sized carbon fibers is crucial. Summary of the Invention

[0005] To overcome the shortcomings of existing technologies, such as poor wear resistance of carbon fibers after sizing, which affects the performance of carbon fiber composites, a microfiber composite polymer sizing agent, its preparation method, and its application are provided, which can enable sizing carbon fiber composites to have good wear resistance.

[0006] The first aspect of the present invention provides a sizing agent comprising a polymer, microfibers, a surfactant, and a solvent; Based on the total mass of the above slurry, the polymer content is 0.1-5wt%, the microfiber content is 0.01-1wt%, and the surfactant content is 0.1-5wt%.

[0007] A second aspect of the present invention provides a method for preparing the sizing agent provided in the first aspect of the present invention, the method comprising the following steps: (1) Mix the polymer with the solvent; (2) In the presence of a surfactant, the mixture obtained in step (1) is mixed with microfibers to obtain a sizing agent.

[0008] The third aspect of the present invention provides an application of the sizing agent provided in the first aspect of the present invention in carbon fiber sizing.

[0009] In the sizing agent provided by this invention, the polymer, as the matrix resin, can form a uniform and dense film layer on the carbon fiber surface, enhancing the adhesion between the polymer and the carbon fiber; the microfibers can form a support network on the carbon fiber surface, further increasing the interfacial bonding force between the carbon fiber and the matrix resin; and the surfactant can improve the wettability of the polymer and microfibers on the carbon fiber. The synergistic effect of these three components significantly improves the interfacial properties of the sized carbon fiber composite material, preventing fuzzing and fiber breakage caused by friction between carbon fibers, thereby giving the carbon fiber composite material good wear resistance and improving its service life and performance stability. Detailed Implementation

[0010] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0011] The first aspect of the present invention provides a sizing agent comprising a polymer, microfibers, a surfactant, and a solvent; Based on the total mass of the above slurry, the polymer content is 0.1-5wt%, the microfiber content is 0.01-1wt%, and the surfactant content is 0.1-5wt%.

[0012] In this invention, when the specific types and contents of each component in the sizing agent are within the above-mentioned range, the resulting sizing agent can significantly improve the stiffness and abrasion resistance of carbon fiber, and can also improve the in-plane shear strength of carbon fiber-polyetheretherketone sheet.

[0013] According to a preferred embodiment of this application, based on the total mass of the slurry, the polymer content is 0.1-3 wt%, the microfiber content is 0.01-0.1 wt%, and the surfactant content is 0.1-1 wt%.

[0014] In this invention, when the specific types and contents of each component in the sizing agent are within the above-mentioned range, the resulting sizing agent can further improve the stiffness and wear resistance of carbon fiber, and can also improve the in-plane shear strength of carbon fiber-polyetheretherketone sheet.

[0015] More preferably, based on the total mass of the slurry, the polymer content is 0.2-0.5 wt%, the microfiber content is 0.02-0.05 wt%, and the surfactant content is 0.1-0.2 wt%.

[0016] According to the present invention, preferably, the mass ratio of the polymer to the microfiber is 8-12:1.

[0017] In this invention, when the mass ratio of the polymer to the microfiber is within the above-mentioned range, the resulting sizing agent can further improve the stiffness and abrasion resistance of the carbon fiber, and further improve the in-plane shear strength of the carbon fiber-polyetheretherketone sheet.

[0018] According to a preferred embodiment of the present invention, the microfibers are synthetic fibers.

[0019] According to the present invention, preferably, the median length of the microfiber is 10-50 μm, the median diameter is 80-160 nm, and the median aggregate size is 0.5-2 μm.

[0020] In this invention, when the median length, median diameter, and median aggregate size of the microfiber are within the above-mentioned ranges, the microfiber is easier to disperse.

[0021] More preferably, the median length of the microfiber is 20-30 μm, the median diameter is 100-140 nm, and the median aggregate size is 0.8-1.2 μm.

[0022] Aggregation size refers to the maximum size of the clumps or bundles formed by fibers during aggregation in any direction.

[0023] In this invention, the aggregate size and median length of the microfibers were measured using a KH7700 three-dimensional microscope, and the median diameter of the microfibers was measured using a Hitachi S-4800 scanning electron microscope. When measuring the median length and median diameter of the microfibers, the microfibers should be fully dispersed to avoid aggregation.

[0024] According to a preferred embodiment of the present invention, the polymer is selected from at least one of polyamide, polyamic acid salt, polyimide, polyether ether ketone, polybenzimidazole, polyurethane and polytetrafluoroethylene.

[0025] According to the present invention, preferably, the polymer is a polyamic acid salt.

[0026] According to a preferred embodiment of the present invention, the microfibers are selected from at least one of polyacrylonitrile fiber, polylactic acid fiber, polyamide fiber, polyetheretherketone fiber, polypropylene fiber, polyethylene fiber, polyvinyl chloride fiber, polytetrafluoroethylene fiber, and polyvinyl alcohol fiber.

[0027] According to the present invention, preferably, the microfibers are polyacrylonitrile fibers.

[0028] According to the present invention, preferably, the microfibers are electrospun fibers.

[0029] The present invention does not particularly limit the type of surfactant, and those skilled in the art can choose conventionally. According to a preferred embodiment of the present invention, the surfactant comprises an organosilicon surfactant and / or a nonionic surfactant.

[0030] According to the present invention, preferably, the organosilicon surfactant is selected from at least one of polyether-modified silicone oil, amino silicone oil, carboxyl silicone oil, hydroxyl silicone oil and epoxy silicone oil.

[0031] More preferably, the organosilicon surfactant is a polyether-modified silicone oil and a hydroxyl silicone oil, wherein the mass ratio of the polyether-modified silicone oil to the hydroxyl silicone oil is 100:0.5-5.

[0032] The polyether-modified silicone oil can be BYK-310 and / or BYK-333.

[0033] The hydroxyl silicone oil can be at least one of Dow Corning 200 Fluid, Wacker AK 100, and Shin-Etsu KF-96.

[0034] According to the present invention, preferably, the nonionic surfactant is selected from at least one of polyoxyethylene surfactants, alkylphenyl ether surfactants, and fatty acid methyl ester amide surfactants.

[0035] More preferably, the nonionic surfactant is polyoxyethylene sorbitol ester and / or polyoxyethylene alkylphenol ether.

[0036] The polyoxyethylene alkylphenol ether can be at least one of Triton X-100, Triton X-114, Triton X-305 and Triton X-405.

[0037] According to a further preferred embodiment of the invention, the surfactant comprises an organosilicon surfactant and a nonionic surfactant.

[0038] The mass ratio of organosilicon surfactants to nonionic surfactants is 1:0.5-2.

[0039] In this invention, the surfactant comprises an organosilicon surfactant and a nonionic surfactant, and when the mass ratio of the two is within the above range, it can further reduce the surface tension of the sizing agent, improve the wettability and uniformity of the sizing agent on the fiber surface, and enable the sizing agent to form a uniform and dense sizing layer on the carbon fiber surface, thereby further improving the wear resistance of the carbon fiber composite material and enhancing its service life and performance stability.

[0040] The present invention does not particularly limit the type of solution, and those skilled in the art can choose conventionally.

[0041] When the polymer is selected from at least one of polyamide, polyamic acid salt, polyimide, polyetheretherketone, polybenzimidazole, polyurethane and polytetrafluoroethylene, the solvent may be an organic solvent, such as at least one of N-methylpyrrolidone, sulfolane, dimethylformamide, dimethylacetamide and dimethyl sulfoxide.

[0042] When the polymer is a polyamic acid salt, the solvent can be water.

[0043] A second aspect of the present invention provides a method for preparing the sizing agent provided in the first aspect of the present invention, the method comprising the following steps: (1) Mix the polymer with the solvent; (2) In the presence of a surfactant, the mixture obtained in step (1) is mixed with microfibers to obtain a sizing agent.

[0044] This invention does not impose any particular limitation on the mixing method, as long as it can achieve the purpose of thorough mixing, and those skilled in the art can choose the conventional method.

[0045] The present invention does not have a particular limitation on the mixing temperature. The components in the sizing agent can be fully mixed at room temperature. Appropriately increasing the temperature, for example at 40-50°C, is more conducive to mixing.

[0046] According to a preferred embodiment of the present invention, the mixing method in steps (1) and (2) is stirring.

[0047] According to the present invention, preferably, the stirring rate in step (2) is 40-100 times that in step (1).

[0048] In this invention, when the ratio of the stirring rate in step (1) to the stirring rate in step (2) is within the above range, the components of the sizing agent can be further mixed evenly, thereby further improving the wettability of the sizing agent.

[0049] In this invention, there is no particular limitation on the stirring time in steps (1)-(2), as long as it can achieve the purpose of thorough mixing, for example, it can be 5 min-3 h.

[0050] The third aspect of the present invention provides the application of the sizing agent provided in the first aspect of the present invention in carbon fiber sizing.

[0051] According to a particularly preferred embodiment of the invention, the sizing agent comprises a polymer, microfibers, a surfactant, and a solvent.

[0052] Based on the total mass of the above slurry, the polymer content is 0.2-2.5 wt%, the microfiber content is 0.01-0.1 wt%, and the surfactant content is 0.1-1 wt%.

[0053] The polymer is a polyamic acid salt.

[0054] The microfibers are polyacrylonitrile fibers.

[0055] The median length of the microfiber is 20-30 μm, the median diameter is 100-140 nm, and the median aggregate size is 0.8-1.2 μm.

[0056] The surfactants include silicone surfactants and nonionic surfactants.

[0057] The mass ratio of organosilicon surfactants to nonionic surfactants is 1:0.5-2.

[0058] The organosilicon surfactant is a polyether-modified silicone oil or a hydroxyl silicone oil.

[0059] The mass ratio of polyether-modified silicone oil to hydroxyl silicone oil is 100:0.5-5.

[0060] The present invention will be described in detail below through embodiments.

[0061] In the following examples, stiffness was measured according to the method in GB / T 7689.4-2013; The number of abrasion resistance cycles was measured using a TM-200H high-speed carbon fiber friction cohesion tester, according to the following method: The fiber bundle moves back and forth at a constant speed under the drive of the rotating wheel, and rubs against the stainless steel rod until it breaks. The number of frictions that the fiber experiences when it breaks is measured.

[0062] Take approximately 30cm of the carbon fiber to be tested. After protecting both ends of the carbon fiber with labels, fix both ends of the carbon fiber bundle to the clamp of the abrasion tester. Load a certain weight onto one end of the clamp (3K: 300g, 12K: 1200g, 24K: 2200g, 48K: 2200g), where 3K, 12K, 24K, and 48K refer to the number of monofilaments in the carbon fiber bundle being 3000, 12000, 24000, and 48000, respectively. After resetting the counter to zero, adjust the rotation speed to 300r / min and start the motor. The carbon fiber begins to rub against the friction roller (stainless steel rod). After the fiber breaks, the machine automatically stops and records the cumulative number of reciprocating strokes until breakage. The average value of 10 tests is taken as the analysis result.

[0063] The in-plane shear strength was measured using a universal testing machine, in accordance with ASTM D 3518.

[0064] Unless otherwise specified, all reagents and raw materials are commercially available. Specifically, the polyacrylonitrile fibers are from Shanghai Petrochemical, with a median length of 20 μm, a median diameter of 120 nm, and a median agglomeration size of 1 μm; The carbon fiber is from Shanghai Petrochemical, and its grade is SCF35. The surfactant Triton X-100 was purchased from Merck; Surfactant BYK-333 was purchased from BYK Chemicals; The surfactant Dow Corning 200 Fluid was purchased from Dow.

[0065] In the following embodiments, unless otherwise specified, all parts refer to parts by mass.

[0066] Example 1 At 40°C, polyamic acid salts were mixed with water and stirred at 200 rpm for 3 hours. Then, a surfactant was added, wherein the mass ratio of Tween 60:BYK-333:Dow Corning 200 Fluid was 100:100:1, and the mixture was stirred at 200 rpm for 0.5 hours. Finally, polyacrylonitrile fibers were added, and the mixture was stirred at 8000 rpm for 5 minutes to obtain the sizing agent.

[0067] Based on the total mass of the above sizing agent, the content of polyamic acid salt is 0.27 wt%, the content of polyacrylonitrile fiber is 0.03 wt%, and the content of surfactant is 0.13 wt%.

[0068] Example 2 The sizing agent was prepared according to the method of Example 1, except that the surfactants were Triton X-100, BYK-333 and Dow Corning 200 Fluid, with a mass ratio of 200:100:1.

[0069] Example 3 The sizing agent was prepared according to the method in Example 1, except that the amount of polyamic acid salt added was different.

[0070] Based on the total mass of the above sizing agent, the content of polyamic acid salt is 1.96 wt%, the content of polyacrylonitrile fiber is 0.03 wt%, and the content of surfactant is 0.13 wt%.

[0071] Example 4 The sizing agent was prepared according to the method in Example 2, except that the amount of polyamic acid salt added was different.

[0072] Based on the total mass of the above sizing agent, the content of polyamic acid salt is 1.96 wt%, the content of polyacrylonitrile fiber is 0.03 wt%, and the content of surfactant is 0.13 wt%.

[0073] Example 5 The sizing agent was prepared according to the method of Example 1, except that the content of polyamic acid salt was 5 wt%, the content of polyacrylonitrile fiber was 1 wt%, and the content of surfactant was 5 wt%.

[0074] Comparative Example 1 The sizing agent was prepared according to the method of Example 1, except that polyacrylonitrile fibers and surfactants were not added.

[0075] Comparative Example 2 The sizing agent was prepared according to the method of Example 1, except that polyamic acid salts were not added.

[0076] Comparative Example 3 The sizing agent was prepared according to the method of Example 1, except that the content of polyamic acid salt was 10 wt%, the content of polyacrylonitrile fiber was 2 wt%, and the content of surfactant was 10 wt%.

[0077] Application Example 1 The carbon fibers were impregnated for 5 seconds in the sizing agents obtained in the above examples and comparative examples. Then, they were pressed using a roller at a pressure of 10 kN and a speed of 2 m / min. Finally, the carbon fibers were dried at 120°C for 30 minutes to obtain sized carbon fibers.

[0078] The stiffness and abrasion resistance of the sized carbon fiber were tested according to the test method described in the specific embodiments of this invention, and the results are shown in Table 1.

[0079] Application Example 2 A unidirectional prepreg, made by impregnating continuous carbon fibers with hot-melt polyetheretherketone resin, is used to prepare [+45 / -45]. 4SThe carbon fiber-polyetheretherketone (PEEEK) laminate specimens, i.e., the laminates, consist of alternating layers of carbon fiber at +45° and -45° angles, repeated four times each, for a total of eight carbon fiber layers. These eight layers form a symmetrical structure with the mid-plane as the axis of symmetry. The nominal dimensions of the specimens are 250mm × 25mm (length × width). The in-plane shear strength of the carbon fiber-PEEK laminates was tested according to the test method described in the specific embodiments of this invention, and the results are shown in Table 1.

[0080] Table 1

[0081] As can be seen from the results in Table 1, carbon fibers sized with the sizing agent provided by the present invention have lower stiffness and better wear resistance, and the carbon fiber-polyetheretherketone (PEEK) sheets made from them have higher in-plane shear strength.

[0082] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A sizing agent, characterized in that, It includes polymers, microfibers, surfactants, and solvents; Based on the total mass of the above slurry, the polymer content is 0.1-5wt%, the microfiber content is 0.01-1wt%, and the surfactant content is 0.1-5wt%.

2. The sizing agent according to claim 1, characterized in that, Based on the total mass of the above slurry, the polymer content is 0.2-2.5 wt%, the microfiber content is 0.01-0.1 wt%, and the surfactant content is 0.1-1 wt%.

3. The sizing agent according to claim 1 or 2, characterized in that, The microfibers are synthetic fibers; Preferably, the median length of the microfiber is 10-50 μm, the median diameter is 80-160 nm, and the median aggregate size is 0.5-2 μm.

4. The sizing agent according to any one of claims 1-3, characterized in that, The polymer is selected from at least one of polyamide, polyamic acid salt, polyimide, polyetheretherketone, polybenzimidazole, polyurethane and polytetrafluoroethylene, preferably polyamic acid salt.

5. The sizing agent according to any one of claims 1-4, characterized in that, The microfibers are selected from at least one of polyacrylonitrile fiber, polylactic acid fiber, polyamide fiber, polyetheretherketone fiber, polypropylene fiber, polyethylene fiber, polyvinyl chloride fiber, polytetrafluoroethylene fiber, and polyvinyl alcohol fiber, preferably polyacrylonitrile fiber; Preferably, the median length of the microfiber is 20-30 μm, the median diameter is 100-140 nm, and the median aggregate size is 0.8-1.2 μm; Preferably, the microfibers are electrospun fibers.

6. The sizing agent according to any one of claims 1-5, characterized in that, The surfactant is selected from organosilicon surfactants and / or nonionic surfactants; Preferably, the organosilicon surfactant is selected from at least one of polyether-modified silicone oil, amino silicone oil, carboxyl silicone oil, hydroxyl silicone oil, and epoxy silicone oil; Preferably, the nonionic surfactant is selected from at least one of polyoxyethylene surfactants, alkylbenzene ether surfactants, and fatty acid methyl ester amide surfactants.

7. The sizing agent according to any one of claims 1-6, characterized in that, The solvent is selected from water and / or organic solvents; Preferably, the organic solvent is selected from at least one of ethanol, acetone, N-methylpyrrolidone, sulfolane, dimethylformamide, dimethylacetamide, and dimethyl sulfoxide.

8. A method for preparing the sizing agent according to any one of claims 1-7, characterized in that, Includes the following steps: (1) Mix the polymer with the solvent; (2) In the presence of a surfactant, the mixture obtained in step (1) is mixed with microfibers to obtain a sizing agent.

9. The method according to claim 8, characterized in that, The mixing method in steps (1) and (2) is stirring. Preferably, the stirring rate in step (2) is 40-100 times that in step (1).

10. The application of the sizing agent according to any one of claims 1-7 in carbon fiber sizing.

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