A modified continuous carbon fiber, a method for modifying the surface of a continuous carbon fiber by in-situ polymerization of aniline, and a carbon fiber reinforced resin composite

Abstract

This invention discloses a modified continuous carbon fiber, a method for in-situ polymerization modification of aniline on the surface of continuous carbon fiber, and a carbon fiber reinforced resin composite material. The modified continuous carbon fiber provided by this invention includes continuous carbon fiber and a polyaniline layer in-situ grown on the surface of the continuous carbon fiber. It is prepared by the following process: the continuous carbon fiber is sequentially oxidized, followed by in-situ polymerization in a polymerization system containing aniline monomers and an oxidant, and finally washed and dried to obtain the modified continuous carbon fiber. This invention, through a continuous process of "surface activation-in-situ polymerization-washing, drying-sizing," uniformly coats the surface of the continuous carbon fiber with a controllable thickness of aniline polymer layer, significantly improving the surface polarity and roughness of the continuous carbon fiber and enhancing its interfacial bonding performance with the resin. The above modification method is adaptable to continuous production lines and can effectively enhance the interfacial properties of composite materials, possessing good prospects for high-end applications.

Description

Technical Field

[0001] This invention relates to the field of continuous carbon fiber modification technology, and more specifically, to a modified continuous carbon fiber, a method for in-situ polymerization modification of aniline on the surface of continuous carbon fiber, and a carbon fiber reinforced resin composite material. Background Technology

[0002] Carbon fiber composites are widely used in aerospace, new energy, and high-end equipment due to their high specific strength and high specific modulus. Their performance bottleneck often lies in the interfacial bonding between the carbon fiber and the resin matrix. Traditional surface treatment methods (such as air oxidation, electrolytic oxidation, and sizing) can introduce oxygen-containing functional groups or physical protective layers, but they have limitations in improving interfacial toughness and achieving functionalization. Furthermore, laboratory surface modification techniques (such as vapor deposition and solution immersion polymerization) are difficult to integrate with continuous industrial production lines, resulting in problems such as poor uniformity, weak adhesion, and low efficiency. Summary of the Invention

[0003] The purpose of this invention is to overcome the problems existing in the prior art and provide a modified continuous carbon fiber, a method for in-situ polymerization modification of aniline on the surface of continuous carbon fiber, and a carbon fiber reinforced resin composite material. The aim is to construct a uniform polyaniline functional layer on the surface of continuous carbon fiber through in-situ polymerization technology, so as to significantly improve the interfacial bonding strength and comprehensive mechanical properties of carbon fiber composite materials.

[0004] The technical problem solved by this invention is achieved by the following technical solution.

[0005] The present invention provides a modified continuous carbon fiber, comprising continuous carbon fiber and a polyaniline layer grown in situ on the surface of the continuous carbon fiber.

[0006] This invention provides a method for in-situ polymerization modification of aniline on the surface of continuous carbon fibers, comprising: in-situ polymerization of aniline on the surface of continuous carbon fibers on a continuous carbon fiber production line to form a polyaniline layer.

[0007] The present invention provides a carbon fiber reinforced resin composite material, comprising a resin matrix and the modified continuous carbon fiber described above or the modified continuous carbon fiber prepared by the preparation method described above.

[0008] The present invention has the following beneficial effects: This invention employs an in-situ polymerization process to directly polymerize aniline monomers on the surface of continuous carbon fibers, obtaining a stable and thickness-controllable polyaniline layer. The surface of the polyaniline layer contains a large number of polar functional groups such as amino and carboxyl groups, which enables the modified continuous carbon fibers to form a dual bond of "physical anchoring + chemical bonding" with the resin matrix. This significantly improves the wettability and compatibility of the modified continuous carbon fibers with the resin matrix, resulting in high bonding strength and significantly enhancing the interfacial bonding performance and mechanical properties of carbon fiber-reinforced resin composites.

[0009] In addition, the present invention adopts a continuous process of "surface activation-in-situ polymerization-washing, drying-sizing", the entire modification process is compatible with continuous carbon fiber production lines, the carbon fiber running speed can reach 50-300m / h, each link can be automated, the production efficiency is high, and it is suitable for large-scale industrial applications. Attached Figure Description

[0010] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0011] Figure 1 AFM image of the modified continuous carbon fiber prepared in Example 1; Figure 2 AFM image of the modified continuous carbon fiber prepared for Comparative Example 4. Detailed Implementation

[0012] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments whose manufacturers are not specified are all conventional products that can be purchased commercially.

[0013] The following provides a detailed description of a modified continuous carbon fiber, a method for in-situ polymerization modification of aniline on the surface of continuous carbon fiber, and a carbon fiber reinforced resin composite material provided by embodiments of the present invention.

[0014] In a first aspect, the present invention provides a modified continuous carbon fiber, comprising a continuous carbon fiber and a polyaniline layer grown in situ on the surface of the continuous carbon fiber.

[0015] Polyaniline, as an intrinsically conductive polymer, possesses excellent chemical stability and tunable conductivity. If it can be stably combined with carbon fibers, it is expected to simultaneously improve the mechanical interlocking and chemical bonding capabilities of the interface. Therefore, this invention proposes to uniformly coat the surface of continuous carbon fibers with a polyaniline layer of controllable thickness, significantly improving the surface polarity and roughness of the continuous carbon fibers and enhancing their interfacial bonding performance with the resin matrix. Furthermore, the modified continuous carbon fibers provided by this invention are modified directly on the carbon fiber production line while the fibers are in operation. This modification process is suitable for continuous production lines and large-scale industrial applications.

[0016] In some alternative embodiments, the thickness of the polyaniline layer on the surface of the continuous carbon fiber is in the range of 10-100 nm.

[0017] In some alternative embodiments, the polyaniline layer on the surface of the continuous carbon fiber is formed by in-situ polymerization of a polymerization system solution containing aniline monomers on the surface of the continuous carbon fiber; Preferably, the polymerization system solution containing aniline monomer includes aniline monomer, oxidant, first dopant, second dopant and deionized water, and the concentrations of each component are: aniline monomer 0.05-0.2 mol / L, oxidant 0.05-0.6 mol / L, first dopant 0.4-0.8 mol / L, second dopant 0.1-0.5 mol / L, and the molar ratio of aniline monomer to oxidant is 1:(0.4-1). Preferably, the oxidant includes one or more of ammonium sulfate, sodium persulfate, and hydrogen peroxide; Preferably, the first dopant includes one or more of sulfuric acid, phosphoric acid, or hydrochloric acid; Preferably, the second dopant includes one or more of p-toluenesulfonic acid, hydrochloric acid, or camphorsulfonic acid.

[0018] In some alternative embodiments, the continuous fiber is a polyacrylonitrile-based dry-jet spun carbon fiber with a tow specification of 12K-24K and a single filament diameter of 5-8μm.

[0019] In a second aspect, the present invention provides a method for in-situ polymerization modification of aniline on the surface of continuous carbon fibers, comprising: on a continuous carbon fiber production line, in-situ polymerization of aniline on the surface of continuous carbon fibers to form a polyaniline layer.

[0020] To overcome the shortcomings of existing continuous carbon fiber surface modification technologies, such as difficulty in continuous production, poor uniformity, and weak interfacial bonding, this invention develops an in-situ polymerization modification method for aniline on the surface of continuous carbon fibers. In this method, continuous carbon fibers are passed through a polymerization reaction tank containing a polymerization system solution of aniline monomers on a carbon fiber production line. During the short residence time of the continuous carbon fibers in the polymerization reaction tank, a polyaniline layer formed by nano-sized polyaniline particles grows in situ on the surface of the continuous carbon fibers. Therefore, this invention provides a novel treatment method that can continuously and online construct a uniform, strongly bonded, thin-layer polyaniline functionalized interface on the surface of carbon fibers. The modification technology provided by this invention is simple, environmentally friendly, and adaptable to industrial continuous production. It has significant theoretical and engineering value for breaking through the bottleneck of interfacial performance of carbon fiber composite materials and promoting their development towards higher damage tolerance and structural-functional integration.

[0021] In some optional embodiments, the process includes the following steps: preparing polyaniline-modified continuous carbon fibers using a continuous process of surface activation-in-situ polymerization-washing, drying-sizing, and surface activation. The carbon fiber running speed during the in-situ polymerization process is consistent with that of the activation, washing, drying, and sizing stages, all at 50-300 m / h, to achieve continuous production. The continuous carbon fiber modification method provided by this invention is suitable for continuous production lines. It adds an in-situ polymerization step to the continuous carbon fiber production process. The entire modification process is compatible with continuous carbon fiber production lines, the carbon fiber running speed can reach 50-300 m / h, and each step can be automated, resulting in high production efficiency and suitability for large-scale industrial applications.

[0022] In some optional embodiments, the surface activation treatment includes: immersing continuous carbon fibers in an electrolytic cell containing an alkaline electrolyte at 15-35°C for 10-30 seconds, followed by washing with water to remove residual electrolyte, thereby obtaining activated carbon fibers. The alkaline electrolyte includes at least one of cyclic Na₂CO₃, NaOH, and Na₂SO₄. During the surface activation of continuous carbon fibers, controlling the appropriate activation temperature and operating speed can effectively activate the surface and avoid fiber strength loss due to excessive etching.

[0023] In some optional embodiments, in-situ polymerization includes: passing activated continuous carbon fibers through a polymerization reaction tank containing a polymerization system solution of aniline monomers to perform in-situ polymerization of aniline on the surface of the continuous carbon fibers. The in-situ polymerization temperature is controlled at 10-35°C, and the residence time is 10-30 s to obtain continuous carbon fibers with a polyaniline layer on the surface. The thickness of the aniline polymer layer is controlled by adjusting the aniline monomer concentration and residence time, and the thickness range is 10-100 nm. During the in-situ polymerization modification of aniline on the surface of continuous carbon fibers, the activated carbon fibers are passed through a polymerization reaction tank containing a polymerization system solution of aniline monomers. In the presence of a first dopant and a second dopant, the aniline monomers are oxidized and polymerized using an oxidant, generating a polyaniline layer formed by nanoscale polyaniline particles on the surface of the continuous carbon fibers. Appropriate polymerization temperature and humidity are controlled to ensure uniform concentration of the polymerization system and avoid the formation of an "inhomogeneous" structure in the polymer layer, thereby achieving precise control of the thickness of the polyaniline layer on the surface of the continuous carbon fibers.

[0024] By precisely controlling the activation intensity and polymerization conditions, excessive etching or oxidation of the carbon fiber surface is avoided, the properties of the carbon fiber itself are well preserved, and the overall mechanical properties of the composite material are not affected.

[0025] In some optional embodiments, the washing, drying, and sizing process includes: passing the in-situ polymerized carbon fiber through a washing tank, followed by drying on drying rollers at a temperature of 50-200°C; passing the carbon fiber through a sizing tank at a speed of 50-300 m / h, with a sizing amount of 1%-2%, and drying at 50-200°C to finally obtain polyaniline-modified continuous carbon fiber. Controlling the sizing amount within the above range can avoid problems such as increased fuzz and roller sticking caused by excessive sizing.

[0026] As can be seen from the above, this invention employs an in-situ polymerization process to directly polymerize aniline monomers on the surface of continuous carbon fibers, obtaining a stable and thickness-controllable polyaniline layer. The surface of the polyaniline layer contains a large number of polar functional groups such as amino and carboxyl groups, which allows the modified continuous carbon fibers to form a dual bond with the resin matrix: "physical anchoring (i.e., the mechanical interlocking between the rough surface of the polyaniline layer and the resin matrix) + chemical bonding (i.e., the chemical reaction and intermolecular forces between the polar functional groups such as amino and carboxyl groups of the polyaniline layer and the functional groups (such as epoxy and hydroxyl groups) of the resin matrix)". This significantly improves the wettability and compatibility of the modified continuous carbon fibers with the resin matrix, resulting in high bonding strength and significantly enhancing the interfacial bonding performance and mechanical properties of the carbon fiber-resin composite material.

[0027] Thirdly, the present invention provides a carbon fiber reinforced resin composite material, comprising a resin matrix and the modified continuous carbon fiber described above or the modified continuous carbon fiber prepared by the preparation method described above.

[0028] This invention achieves a synergistic interface reinforcement effect of "physical anchoring and chemical bonding" by forming a uniform and stable aniline polymer layer in situ on the surface of continuous carbon fibers, ensuring the complete preservation of the mechanical properties of the carbon fiber itself and meeting the requirements of high-end composite materials for interface performance and service stability.

[0029] In some optional embodiments, the resin matrix is ​​one of epoxy resin, polyamide, or polyurethane resin, wherein the modified continuous carbon fiber has a volume fraction of 55%-65% and a carbon fiber areal density of 100-300 g / m³. 2 .

[0030] In some alternative embodiments, the carbon fiber reinforced resin composite material is prepared by the following method: modified continuous carbon fibers are laid in a mold in an orthogonal layup manner, resin is injected into the mold through a vacuum infusion device, so that the resin fully wets the interior of the continuous carbon fiber bundle and is heated and cured, and then naturally cooled to room temperature to obtain the carbon fiber reinforced resin composite material.

[0031] The present invention will be further described below with reference to embodiments.

[0032] Example 1 This embodiment provides a method for in-situ polymerization modification of aniline on the surface of continuous carbon fibers, including the following steps: S1. Surface activation: Continuous carbon fibers are passed through an electrolytic cell containing Na2CO3 solution and immersed at 15-35℃ for 10-30 seconds. After activation, residual electrolyte is removed by washing with water to obtain activated carbon fibers. S2. In-situ polymerization: Prepare a polymerization system solution with 0.1 mol / L aniline monomer, 0.1 mol / L ammonium persulfate, and 0.2 mol / L p-toluenesulfonic acid by concentration, and inject them into a polymerization reaction tank containing 0.4 mol / L dilute sulfuric acid; pass the activated carbon fibers through the polymerization reaction tank to carry out in-situ polymerization of aniline in the polymerization system at a polymerization temperature of 20℃ and a residence time of 20s to obtain carbon fibers with aniline polymerized thin layers.

[0033] S3. Washing and drying: The carbon fibers after in-situ polymerization are washed in a water washing tank and then dried on a drying roller at 125°C to obtain modified continuous carbon fibers.

[0034] S4. Sizing treatment: The carbon fiber is passed through a sizing tank, the sizing time is 20s, the running speed is 150m / h, the sizing amount is 1.5%, and after sizing, it is dried by a drying roller at 125℃.

[0035] S5. Composite material preparation: Modified continuous carbon fibers were laid in a mold in an orthogonal layup manner, with a carbon fiber volume fraction of 55% and a carbon fiber areal density of 200 g / m³. 2Resin is injected into a mold using a vacuum infusion device, allowing the resin to fully impregnate the interior of the continuous carbon fiber bundles and then be heated and cured. After natural cooling to room temperature, carbon fiber composite material is obtained.

[0036] Example 2 The only difference from Example 1 is that the concentration ratio of aniline monomer to oxidant in step S2 is changed to 1:0.5; the polymerization system solution is prepared (0.1 mol / L aniline monomer, 0.05 mol / L ammonium persulfate, and 0.2 mol / L p-toluenesulfonic acid, by concentration) and injected into a polymerization reactor containing 0.4 mol / L dilute sulfuric acid; the activated carbon fibers are passed through the polymerization reactor to carry out in-situ polymerization of aniline in the polymerization system at a polymerization temperature of 20°C and a polymerization time of 20 s.

[0037] Example 3 The only difference from Example 1 is that the concentrations of aniline monomer and ammonium persulfate in step S2 are changed; based on the concentration, 0.2 mol / L aniline monomer, 0.2 mol / L ammonium persulfate, and 0.2 mol / L p-toluenesulfonic acid are injected into the polymerization reactor containing 0.4 mol / L dilute sulfuric acid.

[0038] Example 4 The only difference from Example 1 is that the concentration of the reaction solution in step S2 is changed to 0.8 mol / L.

[0039] Example 5 The only difference from Example 1 is that the oxidant in step S2 is changed to hydrogen peroxide.

[0040] Example 6 The only difference from Example 1 is that the polymerization temperature in step S2 is changed to 35°C.

[0041] Example 7 The only difference from Example 1 is that the polymerization time in step S2 is changed to 30 seconds.

[0042] Comparative Example 1 The only difference from Example 1 is that the concentrations of aniline monomer and ammonium persulfate in step S2 are changed; based on the concentration, 1 mol / L aniline monomer, 1 mol / L ammonium persulfate, and 0.4 mol / L p-toluenesulfonic acid are injected into the polymerization reactor containing 0.4 mol / L dilute sulfuric acid.

[0043] Comparative Example 2 The only difference from Example 1 is that S2 in-situ polymerization is omitted, and the surface-activated carbon fibers are directly sized in S4 after being washed and dried in S3.

[0044] Comparative Example 3 The only difference from Example 1 is that the S1 surface activation step is omitted, that is, the continuous carbon fibers are directly subjected to S2 aniline in-situ polymerization.

[0045] Comparative Example 4 The only difference from Example 1 is that S1 surface activation and S2 in-situ polymerization are omitted, and only S4 sizing is performed.

[0046] Comparative Example 5 The steps are similar to those in Example 1, except that the temperature of the Na2CO3 solution during activation is 40-50℃.

[0047] Comparative Example 6 The steps are similar to those in Example 1, except that the activation time during the activation process is 35-60 seconds.

[0048] Test case The modified carbon fibers obtained in the above embodiments and comparative examples were subjected to comprehensive performance tests, and the test results are shown in Table 1. The specific test methods are as follows: 1. Modified carbon fiber (1) Roughness: According to the test standard GB / T31227-2014 "Method for measuring the surface roughness of sputtered thin films by atomic force microscopy", the contact mode test was adopted; (2) Interfacial shear strength: According to ASTM D7234-19, the microbead debonding method combined with a self-made microdroplet debonding device was used for testing.

[0049] Table 1. Test results of interfacial shear properties of carbon fiber reinforced resin composites prepared in the examples and comparative examples.

[0050] As shown in Table 1, the interfacial shear strength (60.2-69.4 MPa) of the carbon fibers and resin matrix in Examples 1-7 of this application is significantly higher than that in Comparative Examples 1-4 (49.1-56.8 MPa), proving that the modification method effectively improves the interfacial bonding performance of carbon fibers and resin. Figure 1-2 It can be seen that the surface roughness of carbon fiber after in-situ polymerization is significantly improved, with the Ra value reaching 20nm, which is 7nm higher than the Ra value of carbon fiber that has not undergone surface activation and in-situ polymerization.

[0051] In summary, the continuous carbon fiber surface aniline in-situ polymerization modification method provided by this invention, through a synergistic process of "surface activation-in-situ polymerization," can form a uniform and stable aniline polymer layer on the carbon fiber surface. On the one hand, it significantly improves the surface roughness of the carbon fiber (Ra increases by 7 nm), enhancing the mechanical anchoring effect with the resin matrix; on the other hand, the polar functional groups of the aniline polymer layer strengthen the chemical bonding between the modified continuous carbon fiber and the resin matrix. The modification method of this invention is simple, suitable for continuous production, and the modified continuous carbon fiber can significantly improve the interfacial mechanical properties of the composite material.

[0052] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A modified continuous carbon fiber, characterized by, It includes continuous carbon fibers and a polyaniline layer grown in situ on the surface of the continuous carbon fibers.

2. The modified continuous carbon fiber according to claim 1, wherein The thickness of the polyaniline layer on the surface of the continuous carbon fiber is in the range of 10-100 nm.

3. The modified continuous carbon fiber according to claim 1, wherein The polyaniline layer on the surface of the continuous carbon fiber is formed by in-situ polymerization of a polymerization system solution containing aniline monomers on the surface of the continuous carbon fiber. Preferably, the polymerization system solution containing aniline monomer includes aniline monomer, oxidant, first dopant, second dopant and deionized water, and the concentrations of each component are: aniline monomer 0.05-0.2 mol / L, oxidant 0.05-0.6 mol / L, first dopant 0.4-0.8 mol / L, second dopant 0.1-0.5 mol / L, and the molar ratio of aniline monomer to oxidant is 1:(0.4-1). Preferably, the oxidant includes one or more of ammonium sulfate, sodium persulfate, and hydrogen peroxide; Preferably, the first dopant includes one or more of sulfuric acid, phosphoric acid, or hydrochloric acid; Preferably, the second dopant includes one or more of p-toluenesulfonic acid, hydrochloric acid, or camphorsulfonic acid.

4. The modified continuous carbon fiber according to any one of claims 1 to 3, wherein The continuous fiber is a polyacrylonitrile-based dry-jet wet-spun carbon fiber with a tow specification of 12K-24K and a single filament diameter of 5-8μm.

5. A method for continuous carbon fiber surface modification by in-situ polymerization of aniline, characterized by, include: On a continuous carbon fiber production line, aniline is polymerized in situ on the surface of the continuous carbon fiber to form a polyaniline layer.

6. The method of claim 5, wherein, Includes the following steps: A continuous process of "surface activation-in-situ polymerization-washing, drying-sizing" was adopted to prepare polyaniline modified continuous carbon fibers. In the in-situ polymerization process, the carbon fiber running speed was consistent with that of the activation, washing, drying and sizing stages, which was 50-300 m / h, so as to achieve continuous production.

7. The method of claim 6, wherein, In-situ polymerization includes: passing activated continuous carbon fibers through a polymerization reaction tank containing a polymerization system solution of aniline monomers to carry out in-situ polymerization of aniline on the surface of the continuous carbon fibers; Preferably, the activation of continuous carbon fibers includes: passing the continuous carbon fibers through an electrolytic cell containing an alkaline electrolyte, immersing them at 15-35°C for 10-30 seconds, and then washing them with water to remove residual electrolyte to obtain activated carbon fibers, wherein: the alkaline electrolyte includes at least one of cyclic Na2CO3, NaOH, and Na2SO4. Preferably, the in-situ polymerization includes: controlling the in-situ polymerization temperature to 10-35°C and the residence time to 10-30s to obtain continuous carbon fibers with a polyaniline layer on the surface, wherein the thickness of the aniline polymer layer is controlled by adjusting the aniline monomer concentration and the residence time, and the thickness range is 10-100nm.

8. The method of claim 6, wherein, The washing, drying and sizing process includes: washing the in-situ polymerized carbon fiber in a water washing tank, then drying it with a drying roller at a temperature of 50-200℃; passing the carbon fiber through a sizing tank at a speed of 50-300m / h with a sizing amount of 1%-2%, and drying it at 50-200℃ to finally obtain polyaniline modified continuous carbon fiber.

9. A carbon fiber reinforced resin composite material, characterized by, It includes a resin matrix and modified continuous carbon fibers according to any one of claims 1-4 or modified continuous carbon fibers prepared by the preparation method according to any one of claims 5-8.

10. The carbon fiber reinforced resin composite material according to claim 9, characterized in that, The resin matrix comprises one of an epoxy resin, a polyamide or a polyurethane resin, wherein: the volume fraction of the modified carbon fibers is 55-65%, the areal density of the carbon fibers is 100-300 g / m 2 .

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