Carbon fiber surface treatment method based on molecular layer deposition

Abstract

The invention discloses a continuous carbon fiber surface treatment technology based on molecular layer deposition (MLD), and belongs to the field of carbon fiber surface science. According to the method, by directionally introducing a functional group matched with a matrix, the interface performance is remarkably improved, and the surface of the carbon fiber is accurately modified. By means of the method, molecular-level precision uniform deposition can be achieved on the complex three-dimensional carbon fiber surface, and therefore precise regulation and control over the type, density and spatial distribution of functional groups are achieved. On the premise that the surface etching degree of the carbon fibers is not increased and the carbon fibers are uniformly deposited, high-density and designable functional groups are introduced to form strong interaction and excellent interface wettability with a resin matrix, so that the interface stress transmission efficiency is remarkably enhanced, and finally, the interface bonding effect of the composite material is improved. The method has the advantages of being uniform in treatment, high in efficiency, continuous in process, high in customization, free of damage to fibers and the like, and is suitable for batch preparation of the high-performance carbon fiber reinforced resin-based composite material.

Description

Technical Field

[0001] This invention belongs to the field of carbon fiber surface treatment technology, specifically relating to a method for continuous functional group modification of carbon fiber surface based on molecular layer deposition, which aims to directionally enhance the interfacial bonding performance between carbon fiber and resin matrix. Background Technology

[0002] Carbon fiber reinforced resin matrix composites are widely used in aerospace, automotive, and other industries due to their advantages such as lightweight, high strength, and corrosion resistance. Among these applications, the interface is crucial for the effective stress transfer and structural integrity of the composite material. However, the chemical inertness and smooth surface of carbon fibers result in weak interfacial bonding between the carbon fiber and the polymer matrix, which has become a key bottleneck restricting further improvements in the overall mechanical properties of the composite material.

[0003] To improve interfacial properties, various surface treatment technologies have been developed. Traditional carbon fiber surface treatment methods, such as oxidation and plasma treatment, can improve interfacial properties to some extent, but still suffer from problems such as uneven treatment, uncontrollable functional group types, potential damage to the fiber matrix, or discontinuous processing. Patent CN120518889A discloses a surface modification method that uses temperature-controlled vaporization oxidation to achieve steam wetting and increased roughness on the carbon fiber surface, thereby enhancing the interfacial bonding between carbon fiber and epoxy resin. However, this method etches the carbon fiber surface, resulting in uncontrollable and insufficiently uniform micro / nano structures, and it does not truly introduce stable chemically active groups, limiting the long-term stability of the interface. Patent CN120138971A discloses a modification method that prepares a sandwich-type self-assembled structure by repeatedly impregnating the carbon fiber surface, thereby enhancing the strength and toughness of carbon fiber epoxy resin composites. However, this method's multiple impregnations may lead to poor treatment uniformity, making it difficult to ensure consistent results within the fiber bundle. Summary of the Invention

[0004] To address the problems of poor uniformity, difficulty in precisely controlling functional group types, and easy damage to the fiber's bulk strength in traditional fiber modification layers, this invention provides a carbon fiber surface treatment method based on molecular layer deposition (MLD), innovatively applying MLD technology to carbon fiber surface modification. This technology enables non-destructive, uniform MLD deposition on the complex porous surface of carbon fibers, with precise control over thickness, chemical composition, and chemical structure. By designing the deposition raw materials, the chemical functional groups on the carbon fiber surface can be customized as needed, thus opening up a completely new technical pathway for carbon fiber surface functionalization and holding significant importance for promoting the industrial application of high-performance carbon fiber composite materials.

[0005] To solve the above-mentioned technical problems, the present invention adopts the following technical solution:

[0006] This invention provides a continuous surface treatment method for carbon fibers based on molecular layer deposition. By directionally depositing amino, carboxyl, or hydroxyl functional groups onto carbon fibers using molecular layer deposition technology, and in conjunction with a sizing agent, the interfacial shear strength between the carbon fibers and the resin matrix is ​​improved, thereby completing the surface treatment of the carbon fibers.

[0007] The molecular layer deposition technology employs a molecular layer deposition apparatus that is an improvement on existing molecular layer deposition apparatuses by adding a carbon fiber guide roller to achieve continuous deposition.

[0008] Specifically, the following steps are included:

[0009] Step 1, filament feeding and tension control: Place the carbon fiber bundle on the filament feeding machine and apply constant tension to ensure that the carbon fiber remains straight and not loose during subsequent processing.

[0010] Step 2, carbon fiber desizing treatment: The carbon fiber is continuously passed through a desizing furnace for high-temperature thermal oxidation treatment to remove the original sizing agent on the surface.

[0011] Step 3, continuous molecular layer deposition functionalization: the desized carbon fibers are continuously passed through the molecular layer deposition device at a speed of 2.8~3.0 m / min, and a molecular layer containing specific functional groups of a certain thickness is deposited on the fiber surface by molecular layer deposition technology.

[0012] Step 4, continuous sizing: the functionalized carbon fibers enter the sizing tank and are immersed in a sizing agent that matches the matrix, depositing a layer of molecular layers with specific functional groups on their surface.

[0013] Step 5, drying and winding: After the sizing carbon fiber is dried by the drying device, it is wound by the winding machine to obtain surface-modified carbon fiber.

[0014] Furthermore, the carbon fiber is continuously passed through a desizing furnace under the traction of a transmission device for high-temperature thermal oxidation treatment at a temperature of 450~550℃ for 10~15s.

[0015] Furthermore, by using molecular layer deposition technology, at 60~200℃, a deposition material is pulsed in, and a molecular layer containing specific functional groups with a thickness of 5~30 nanometers is deposited on the fiber surface.

[0016] Furthermore, the sizing agent is selected from thermosetting sizing agents or thermoplastic sizing agents;

[0017] The thermosetting sizing agent is an epoxy resin sizing agent, a vinyl resin sizing agent, or a phenolic resin sizing agent, etc.

[0018] The thermoplastic sizing agent is a polyamide sizing agent, a polyurethane sizing agent, a polyimide sizing agent, or a polyamic acid sizing agent, etc.

[0019] The dosage of sizing agent is 0.8-1.2%, and the sizing immersion time is 5-10 seconds.

[0020] Furthermore, amino, carboxyl, or hydroxyl functional groups are directionally deposited onto carbon fibers using molecular layer deposition technology, specifically:

[0021] The raw materials used for depositing amino groups are ethylenediamine, acrylamine, or hexamethylenediamine, which contain highly reactive primary amine groups.

[0022] The raw materials used for carboxyl deposition are five-membered cyclic anhydrides with rigid aromatic skeletons and high reactivity, such as pyromellitic dianhydride, 1,4,5,8-naphthalenetetracarboxylic dianhydride, or 3,3',4,4'-biphenyltetracarboxylic dianhydride.

[0023] The raw materials used for depositing hydroxyl groups are polyols containing highly active primary hydroxyl groups, such as ethylene glycol, glycerol, or 1,4-butanediol.

[0024] Furthermore, the carbon fibers prepared by the above method are applicable to polyacrylonitrile carbon fibers such as T300, T700, T800, and T1000.

[0025] Furthermore, the carbon fiber prepared by the above method is suitable for composite with thermosetting resins such as epoxy resin, phenolic resin, and unsaturated polyester, as well as thermoplastic resin matrices such as polyamide, polyphenylene sulfide, and polyether ether ketone.

[0026] Compared with the prior art, the present invention has the following advantages:

[0027] 1. This invention features continuous processing and high efficiency. It successfully integrates molecular layer deposition technology into a continuous carbon fiber processing line, realizing fully automated carbon fiber surface modification, greatly improving processing efficiency, and has the potential for industrial application.

[0028] 2. This invention significantly improves the interfacial properties between carbon fibers and the resin matrix. It precisely introduces highly active functional groups through molecular layer deposition (MLD) technology and combines this with a sizing agent that is compatible with the resin matrix for synergistic modification. This strategy works from both chemical and physical perspectives: on the one hand, the functional groups and the sizing agent form a dense hydrogen bond network; on the other hand, the sizing agent molecules become deeply entangled with the resin matrix. These dual mechanisms work together to fundamentally and significantly improve the interfacial shear strength of the composite material.

[0029] 3. The present invention provides uniform and controllable surface modification treatment for carbon fibers. The production line is equipped with a constant tension control system and a dedicated continuous molecular layer deposition reaction chamber, which ensures the uniformity and consistency of the functional group molecular layer and the sizing layer on the continuous long fiber, resulting in stable product quality.

[0030] 4. This invention is flexible and customizable. By adjusting the raw materials and process parameters of molecular layer deposition, the chemical properties of the carbon fiber surface can be customized to meet the interface optimization requirements of different resin matrices. Attached Figure Description

[0031] To more clearly illustrate the technical solutions in the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0032] Figure 1 This is a schematic diagram of the continuous carbon fiber surface treatment production line of the present invention.

[0033] Figure 2 This is a schematic diagram showing the contact angle and interfacial shear strength after the modification treatment according to the present invention. Detailed Implementation

[0034] To gain a deeper understanding of this invention, we will describe it in its entirety and in detail. However, this invention has many implementations and is not limited to the specific examples listed herein. These examples are presented to enhance a comprehensive understanding of the disclosure of this invention.

[0035] This invention designs a continuous carbon fiber processing device to perform the method of this invention. The continuous carbon fiber processing device includes: a fiber feeding device, a desizing device, a molecular layer deposition device, a sizing device, a drying device, and a fiber winding device. The fiber feeding machine is used to apply a constant tension to the carbon fiber bundle. The desizing device is a desizing furnace, which performs desizing treatment on the carbon fiber bundle. The desizing treatment is a high-temperature thermal oxidation treatment. The sizing device is a sizing tank, which is used to hold the sizing agent and to sizing the carbon fiber. The drying device is used to dry the sizing carbon fiber. The fiber winding device is a fiber winding machine, which is used to wind the carbon fiber.

[0036] This invention discloses a continuous surface treatment method for carbon fibers based on molecular layer deposition, specifically comprising the following steps:

[0037] 1. Install the T700 grade carbon fiber tow onto the unwinding machine, set a constant tension, and drive it at an average speed of 3.0 m / min.

[0038] 2. Under the traction of the transmission device, the carbon fiber passes through a desizing furnace. High-temperature desizing is carried out at 450~550℃ for 10~15 seconds to remove the original commercial sizing agent and obtain desizing carbon fiber.

[0039] 3. The carbon fiber enters the molecular layer deposition device along the transmission device. When ethylenediamine is used as raw material, the chamber temperature is preheated and set to 65°C; when pyromellitic dianhydride is used as raw material, the chamber temperature is set to 178°C. The device is cyclically pulsed 60 times to obtain highly chemically active carbon fibers with specific functional groups deposited.

[0040] 4. After being processed by the molecular layer deposition equipment, the carbon fiber is immersed in the corresponding sizing agent through the sizing tank along the transmission device. The sizing amount is 1.0% and the immersion time is 10s to obtain sizing carbon fiber.

[0041] 5. After sizing, the carbon fibers are fed into the drying process via the transmission device, and then wound up by the winding machine to obtain surface-modified carbon fibers.

[0042] 6. The modified carbon fiber monofilaments were combined with a resin matrix to prepare carbon fiber monofilament microdroplet composite materials.

[0043] 7. The carbon fiber monofilament microdroplet composite material obtained in the corresponding embodiment was subjected to contact angle and interfacial shear strength tests.

[0044] The inventors conducted a series of tests based on the above method, and the specific test settings are shown in Table 1 below:

[0045] Table 1

[0046]

[0047] The test results are shown in Table 2:

[0048] Table 2

[0049]

[0050] Comparing the data from the above embodiments reveals that the functional groups deposited by MLD improve the wettability of the carbon fiber surface by increasing its polarity and surface energy, thereby enhancing the interfacial bonding between the fiber and the matrix. A lower contact angle results in better wettability and correspondingly higher interfacial shear strength. Furthermore, different functional groups exhibit significant performance selectivity on different matrices. For epoxy and phenolic resin matrices, the -COOH functional group achieves the smallest contact angle and the highest interfacial shear strength, exhibiting the best overall performance. On polyamide and polyetheretherketone matrices, the -NH2 functional group demonstrates the best wettability and interfacial adhesion.

[0051] The above results demonstrate that by directionally depositing matrix-compatible functional groups on the carbon fiber surface for different matrix materials, the surface wettability of the material can be effectively improved and the interfacial bonding strength can be significantly enhanced. This discovery provides important experimental evidence for the application of this patented technology in composite material interface engineering design.

[0052] In summary, the continuous carbon fiber modification scheme of desizing, molecular layer deposition functionalization and sizing provided by the present invention can significantly enhance the interfacial bonding between carbon fibers and resin matrix, thereby contributing to the preparation of high-performance carbon fiber reinforced composite materials.

[0053] Contents not described in detail in this specification are prior art known to those skilled in the art. Although illustrative specific embodiments of the invention have been described above to facilitate understanding by those skilled in the art, it should be understood that the invention is not limited to the scope of the specific embodiments. Various modifications are readily apparent to those skilled in the art as long as they fall within the spirit and scope of the invention as defined and determined by the appended claims, and all inventions utilizing the concept of this invention are protected.

Claims

1. A carbon fiber surface treatment method based on molecular layer deposition, characterized in that, The surface treatment of carbon fibers is achieved by directionally depositing functional groups such as amino, carboxyl, or hydroxyl groups onto carbon fibers using molecular layer deposition technology, combined with a sizing agent, thereby improving the interfacial shear strength between the carbon fibers and the resin matrix.

2. The carbon fiber surface treatment method based on molecular layer deposition according to claim 1, characterized in that: The molecular layer deposition technology employs a molecular layer deposition apparatus that is an improvement on existing molecular layer deposition apparatuses by adding a carbon fiber guide roller to achieve continuous deposition.

3. The carbon fiber surface treatment method based on molecular layer deposition according to claim 2, characterized in that: The aforementioned carbon fiber surface treatment technology is matched with a continuous carbon fiber processing device to complete the continuous processing of carbon fibers. The continuous carbon fiber processing device includes: a fiber feeding device, a desizing device, a molecular layer deposition device, a sizing device, a drying device, and a fiber take-up device; The fiber feeding machine is used to apply constant tension to the carbon fiber bundle; The desizing device is a desizing furnace, which desizing carbon fiber bundles. The desizing process is a high-temperature thermal oxidation process with a processing temperature of 450~550℃ and a processing time of 10~15 seconds. The sizing device is a sizing tank, which is used to hold the sizing agent and to sizing the carbon fiber. The drying device is used to dry carbon fibers that have undergone sizing treatment. The winding device is a winding machine used to wind up carbon fibers.

4. The carbon fiber surface treatment method based on molecular layer deposition according to claim 1, characterized in that: The molecular layer deposition process is carried out at 60~200℃, and the thickness of the functional group molecular layer formed is 5~30 nanometers; the deposition material is introduced by pulse 20~100 times.

5. The carbon fiber surface treatment method based on molecular layer deposition according to claim 1, characterized in that: The sizing agent is selected from thermosetting sizing agents or thermoplastic sizing agents; The thermosetting sizing agent is an epoxy resin sizing agent, a vinyl resin sizing agent, or a phenolic resin sizing agent. The thermoplastic sizing agent is a polyamide sizing agent, a polyurethane sizing agent, a polyimide sizing agent, or a polyamic acid sizing agent; The dosage of sizing agent is 0.8-1.2%, and the sizing immersion time is 5-10 seconds.

6. The carbon fiber surface treatment method based on molecular layer deposition according to claim 1, characterized in that: The functional groups of amino, carboxyl, or hydroxyl groups are directionally deposited onto carbon fibers using molecular layer deposition technology. Specifically: The raw materials used for depositing amino groups are ethylenediamine, acrylamine, or hexamethylenediamine, which contain highly reactive primary amine groups. The raw materials used for carboxyl deposition are five-membered cyclic anhydrides with rigid aromatic skeletons and high reactivity, such as pyromellitic dianhydride, 1,4,5,8-naphthalenetetracarboxylic dianhydride, or 3,3',4,4'-biphenyltetracarboxylic dianhydride. The raw materials used for depositing hydroxyl groups are polyols containing highly active primary hydroxyl groups, such as ethylene glycol, glycerol, or 1,4-butanediol.

7. The carbon fiber surface treatment method based on molecular layer deposition according to claim 3, characterized in that: Includes the following steps: Step 1: Place the carbon fiber tow on the unwinding machine and apply a constant tension; Step 2: The carbon fiber is continuously passed through a desizing furnace for desizing treatment to obtain desized carbon fiber; Step 3: The desized carbon fiber is fed into a molecular layer deposition device to deposit a molecular layer containing specific functional groups on the fiber surface. Step 4: The carbon fibers treated in Step 3 are put into a sizing tank containing a sizing agent that matches the matrix for sizing treatment to obtain sizing carbon fibers. Step 5: After the sized carbon fiber is dried at 150~200℃ by a drying device, it is wound up by a winding machine to obtain surface-modified carbon fiber.

8. A highly surface-active carbon fiber, characterized in that, The carbon fiber is prepared by the method described in any one of claims 1 to 7.

9. The modified carbon fiber prepared according to claim 8, characterized in that, The method is applicable to polyacrylonitrile carbon fibers.

10. The modified carbon fiber prepared according to claim 8, characterized in that, The carbon fiber is suitable for composite with epoxy resin, phenolic resin, unsaturated polyester thermosetting resin and polyamide, polyphenylene sulfide, and polyether ether ketone thermoplastic resin matrix.

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