Dipping and airing method of carbon fiber soft felt

Abstract

The invention discloses a carbon fiber soft felt impregnating and airing method, which comprises the following steps: pretreating a carbon fiber soft felt with a nitric acid solution with a specific concentration, preparing an impregnant containing epoxy resin, a curing agent and other components, and a microcapsule wall material is of a gelatin-polyurea multilayer structure and contains a repairing agent. Intermittent stirring and pressure and vacuum assistance are adopted during impregnation operation, so that sufficient permeation of the impregnant is ensured. And controlling the temperature, the humidity and the turn-over time during airing to cure the impregnant. The preparation of the microcapsule relates to the steps of inner layer gelatin coating, outer layer polyurea coating, urea-formaldehyde resin polymerization and the like, and gamma-aminopropyltriethoxysilane is added for treatment when the microcapsule is formed. The method can solve the problems of non-uniform impregnation, insufficient penetration depth, unstable microcapsule performance and the like in a traditional impregnation method, realizes uniform and sufficient penetration of the impregnant into the carbon fiber soft felt, and improves the performance and stability of the microcapsule, thereby improving the comprehensive performance of the carbon fiber soft felt composite material.

Description

Technical Field

[0001] This invention relates to the field of carbon fiber composite material processing technology, specifically to a method for impregnating and drying carbon fiber soft felt. Background Technology

[0002] Carbon fiber felt, due to its excellent properties such as lightweight, high strength, and high modulus, is widely used in many fields such as aerospace, automotive industry, and sporting goods. However, in practical applications, to enhance its performance and functionality, carbon fiber felt often needs to be impregnated, allowing the impregnating agent to fully penetrate into the fibers, thereby improving the overall performance of the composite material.

[0003] Traditional impregnation methods have some drawbacks, such as uneven impregnation, which can easily lead to insufficient or excessive impregnation in certain areas, affecting the performance and stability of composite materials. The impregnating agent has limited penetration depth and cannot fully fill the pores and fiber gaps inside the carbon fiber felt, making it difficult for the composite material to achieve the ideal strength and toughness. In addition, the preparation and application technology of microcapsules is not perfect, and the performance and stability of microcapsules are not good, so they cannot effectively perform their repair and other functions.

[0004] Therefore, it is of great significance to provide an impregnation and drying method for carbon fiber soft felt that can make the impregnating agent penetrate into the interior of the carbon fiber soft felt evenly and fully, while improving the performance and stability of microcapsules. Summary of the Invention

[0005] The purpose of this invention is to provide an impregnation and drying method for carbon fiber soft felt, which solves the problems of uneven impregnation, insufficient penetration depth and unstable microcapsule performance in traditional impregnation methods. This method enables the impregnating agent to penetrate the interior of the carbon fiber soft felt evenly and fully, improves the performance and stability of the microcapsules, and thus enhances the overall performance of the carbon fiber soft felt composite material, meeting the needs of different fields for high-performance carbon fiber soft felt.

[0006] To achieve the above objectives, the present invention provides the following technical solution: a method for impregnating and drying carbon fiber soft felt, comprising the following steps: (1) Pretreatment of carbon fiber soft felt The carbon fiber felt was soaked in a 30%-40% nitric acid solution for 3-6 hours; (2) Preparation of impregnating agent The impregnating agent comprises, by weight, 6-7 parts epoxy resin, 1-2 parts aliphatic amine curing agent, 0.5-0.8 parts n-butanol, 0.8-1.2 parts rubber elastomer toughening agent, and 0.5-0.8 parts microcapsules. The components are stirred in a mixing container at a speed of 300-500 r / min for 15-30 min to ensure uniform mixing. The wall material of the microcapsule has a multi-layer structure, with an inner layer of flexible gelatin and an outer layer of polyurea. Melamine is added as a crosslinking agent during the synthesis of the wall material. The microcapsule contains a repair agent, which is a combination of epoxy resin and curing agent. (3) Impregnation operation Pour the impregnating agent prepared in step (2) into the impregnation tank, and use a paddle mixer to stir intermittently at a stirring speed of 200-300 r / min. Stir for 5 minutes and stop for 2 minutes. Control the impregnation temperature at 40-60℃ to ensure that the impregnating agent is evenly distributed and maintains good fluidity. The carbon fiber felt is completely immersed in the impregnation tank for 15-30 minutes. The impregnation tank is placed in a sealed container, and nitrogen is introduced into the sealed container to increase the air pressure inside the container. The pressure is precisely controlled using a pressure sensor and a pressure regulating valve to maintain it within the range of 0.1-0.3 MPa, ensuring that the impregnating agent fully penetrates into the interior of the carbon fiber felt. Vacuum assistance is used during the impregnation process. The carbon fiber felt and impregnating agent are placed in a vacuum environment with a vacuum degree of 0.05-0.1MPa for 5-10 minutes and then restored to normal pressure or slightly positive pressure. The slightly positive pressure range is 0.01-0.03MPa, which further improves the impregnation effect. (4) Drying treatment Remove the impregnated carbon fiber felt from the impregnation tank and allow the excess impregnating agent to drip for 5-10 minutes. Then, lay the carbon fiber felt flat on the drying rack in the drying room. The temperature of the drying room should be 20-30℃ and the relative humidity should not exceed 60%. Turn the carbon fiber felt over every 2-3 hours and let it dry for 24-72 hours until the impregnating agent is completely cured.

[0007] Preferably, in step (1), the concentration of the nitric acid solution is 35%, and the carbon fiber felt is soaked in it for 4 hours.

[0008] Preferably, in step (2), the impregnating agent contains 6.5 parts epoxy resin, 1.5 parts fatty amine curing agent, 0.6 parts n-butanol, 1 part rubber elastomer toughening agent, and 0.6 parts microcapsules; the stirring speed is 400 r / min, and the stirring time is 20 min.

[0009] Preferably, in step (3), the stirring speed of the paddle agitator is 250 r / min, the immersion temperature is 50℃, the immersion time is 20 min, the applied pressure is 0.2 MPa, the vacuum environment treatment time is 8 min, and the micro-positive pressure after recovery is 0.02 MPa.

[0010] Preferably, in step (4), the temperature of the drying room is 25°C, the relative humidity is 50%, the turning interval is 2.5h, and the drying time is 48h.

[0011] Preferably, the preparation of the microcapsules includes the following steps: S1. Preparation of inner wall material Weigh gelatin and deionized water at a mass ratio of 1:10. Add the gelatin to the deionized water and heat and stir in a water bath at 55°C until the gelatin is completely dissolved to form a gelatin solution of a certain concentration. S2, Preparation of Repair Agent Mix epoxy resin and fatty amine curing agent in a 10:1 ratio, and add an appropriate amount of acetone or methyl ethyl ketone as a diluent to prepare a repair solution. The amount of diluent added is 10%-20% of the total mass of the repair solution. S3, Gelatin inner layer encapsulation The repair solution prepared in step S2 is dispersed in the gelatin solution prepared in S3. The solution is stirred at a speed of 1000-1500 r / min using a high-speed stirrer to form tiny droplets of repair solution, which are then encapsulated by the gelatin solution, forming a preliminary structure in which the repair solution is encapsulated by gelatin as the inner wall material. S4. Preparation of outer wall material Synthesis of polyurea: Toluene diisocyanate (TDI) and ethylenediamine are weighed in a molar ratio of 1:1 and added to acetone. The amount of acetone used is 3-5 times the total mass of TDI and ethylenediamine. The mixture is reacted at 60°C for 3 hours to form polyurea, so as to completely dissolve TDI and ethylenediamine. S5, polyurea outer layer The gelatin-coated repair fluid droplet dispersion system formed in step S3 is slowly added to the polyurea solution prepared in step S4 while stirring. During the stirring process, the polyurea will gradually deposit on the surface of the gelatin-coated droplets to form an outer coating. S6, Packaging The repair solution coated with a polyurea outer layer is dispersed in an aqueous medium, and sodium dodecyl sulfate is used as an emulsifier to form a water-in-oil emulsion. The amount of emulsifier is 1%-3% of the mass of the repair solution. S7. Synthesis of urea-formaldehyde resin prepolymer Weigh out 10 parts of urea, 20 parts of formaldehyde, 0.5 parts of ammonium chloride, and 1 part of melamine. First, add urea and formaldehyde to the reaction vessel and carry out a polycondensation reaction at pH 4 and temperature 70℃. Then, add ammonium chloride as a catalyst and react for 3 hours to form a urea-formaldehyde resin prepolymer. Melamine is added as a crosslinking agent during the synthesis of urea-formaldehyde resin. S8, Microcapsule formation Urea-formaldehyde resin prepolymer was dropped into an emulsion, and the urea-formaldehyde resin was polymerized on the surface of the repair solution droplets at 50°C, a stirring speed of 800 r / min, and a pH of 8 to form microcapsules. Microcapsules with a particle size of 10-100 μm were obtained by filtration and washing.

[0012] Preferably, in step S2, the amount of diluent added in the preparation of the repair agent is 15%; In step S3, when forming the gelatin-encapsulated core, the high-speed mixer is stirred at a speed of 1200 r / min. In step S6, the amount of emulsifier used when the water-in-oil emulsion is formed is 2%.

[0013] Preferably, in step S8, when the urea-formaldehyde resin prepolymer is dropped into the water-in-oil emulsion to form microcapsules, γ-aminopropyltriethoxysilane is added at 3% of the total mass of the wall material; first, γ-aminopropyltriethoxysilane is dissolved in ethanol to prepare a 30% solution, and then this solution is slowly added dropwise or added to the reaction system in which the microcapsules are being formed.

[0014] Preferably, in step S8, the concentration of the γ-aminopropyltriethoxysilane solution is 5%-15%. This solution is slowly added dropwise or added to the reaction system in which microcapsules are forming, and then the reaction is carried out at 40°C for 1.5 hours.

[0015] Preferably, the concentration of the γ-aminopropyltriethoxysilane solution is 10%.

[0016] Compared with the prior art, the beneficial effects of the present invention are: 1. This invention effectively removes air from inside the carbon fiber felt by using intermittent stirring, applying pressure of 0.1-0.3 MPa, and vacuum assistance during the impregnation process, thereby accelerating the flow rate of the impregnating agent, enhancing its penetration ability, and ensuring that the impregnating agent is uniformly and fully filled into the pores and fiber gaps of the carbon fiber felt. This improves the impregnation uniformity and saturation of the composite material, and thus enhances the strength and toughness of the composite material.

[0017] 2. The microcapsules in this invention adopt a gelatin-polyurea multilayer wall material structure, and melamine is added as a crosslinking agent during the wall material synthesis process to enhance the strength and stability of the wall material. Simultaneously, γ-aminopropyltriethoxysilane is added during the microcapsule preparation process to further improve the performance of the microcapsules and their compatibility with the impregnating agent, enabling the microcapsules to better perform their repair and other functions and extend the service life of the composite material.

[0018] 3. This invention precisely limits and optimizes various process parameters in the impregnation and drying process, such as nitric acid solution concentration, impregnating agent component ratio, stirring speed, temperature, pressure, and time, ensuring the stability and repeatability of the process, which is conducive to large-scale industrial production and improves production efficiency and product quality.

[0019] 4. By strictly controlling the temperature, relative humidity, turning interval, and drying time in the drying chamber during the drying process, this invention provides a good environment for the curing of the impregnating agent, ensuring that the impregnating agent can be completely cured, thereby further improving the performance and quality of the composite material. Detailed Implementation

[0020] The technical solution of the present invention will be clearly and completely described below with reference to specific embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0021] One embodiment of the present invention provides a method for impregnating and drying carbon fiber soft felt, comprising the following steps: (1) Pretreatment of carbon fiber soft felt The carbon fiber felt was soaked in a 30%-40% nitric acid solution for 3-6 hours; (2) Preparation of impregnating agent The impregnating agent comprises, by weight, 6-7 parts epoxy resin, 1-2 parts aliphatic amine curing agent, 0.5-0.8 parts n-butanol, 0.8-1.2 parts rubber elastomer toughening agent, and 0.5-0.8 parts microcapsules. The components are stirred in a mixing container at a speed of 300-500 r / min for 15-30 min to ensure uniform mixing. The wall material of the microcapsule has a multi-layer structure, with an inner layer of flexible gelatin and an outer layer of polyurea. Melamine is added as a crosslinking agent during the synthesis of the wall material. The microcapsule contains a repair agent, which is a combination of epoxy resin and curing agent. (3) Impregnation operation Pour the impregnating agent prepared in step (2) into the impregnation tank, and use a paddle mixer to stir intermittently at a stirring speed of 200-300 r / min. Stir for 5 minutes and stop for 2 minutes. Control the impregnation temperature at 40-60℃ to ensure that the impregnating agent is evenly distributed and maintains good fluidity. The carbon fiber felt is completely immersed in the impregnation tank for 15-30 minutes. The impregnation tank is placed in a sealed container, and nitrogen is introduced into the sealed container to increase the air pressure inside the container. The pressure is precisely controlled using a pressure sensor and a pressure regulating valve to maintain it within the range of 0.1-0.3 MPa, ensuring that the impregnating agent fully penetrates into the interior of the carbon fiber felt. Vacuum assistance is used during the impregnation process. The carbon fiber felt and impregnating agent are placed in a vacuum environment with a vacuum degree of 0.05-0.1MPa for 5-10 minutes and then restored to normal pressure or slightly positive pressure. The slightly positive pressure range is 0.01-0.03MPa, which further improves the impregnation effect. (4) Drying treatment Remove the impregnated carbon fiber felt from the impregnation tank and allow the excess impregnating agent to drip for 5-10 minutes. Then, lay the carbon fiber felt flat on the drying rack in the drying room. The temperature of the drying room should be 20-30℃ and the relative humidity should not exceed 60%. Turn the carbon fiber felt over every 2-3 hours and let it dry for 24-72 hours until the impregnating agent is completely cured.

[0022] More specifically, in step (1), the concentration of the nitric acid solution is 35%, and the carbon fiber felt is soaked in it for 4 hours. This step helps to remove impurities and oil stains from the carbon fiber surface, while etching the carbon fiber surface to increase its roughness, thereby improving the interfacial bonding force between the carbon fiber and the impregnating agent, resulting in better subsequent impregnation effects and enhancing the overall performance of the composite material.

[0023] More specifically, in step (2), the impregnating agent contains 6.5 parts epoxy resin, 1.5 parts aliphatic amine curing agent, 0.6 parts n-butanol, 1 part rubber elastomer toughening agent, and 0.6 parts microcapsules; the stirring speed is 400 r / min, and the stirring time is 20 min. In this step, the epoxy resin, aliphatic amine curing agent, n-butanol, rubber elastomer toughening agent, and microcapsules are mixed in this proportion and stirred evenly at a certain speed and time. This helps to utilize the epoxy resin to provide bonding strength, the aliphatic amine curing agent to cure the epoxy resin, the n-butanol to dilute it, and facilitates the uniform mixing of the components. The rubber elastomer toughening agent can improve the toughness of the material and prevent brittle fracture during use. The microcapsules then play a self-repairing role.

[0024] More specifically, in step (3), the paddle mixer speed is 250 r / min, the impregnation temperature is 50℃, the impregnation time is 20 min, and the applied pressure is 0.2 MPa; the vacuum environment treatment time is 8 min, and the micro-positive pressure after recovery is 0.02 MPa. In this step, nitrogen gas is introduced at a pressure of 0.1-0.3 MPa, which allows the impregnating agent to penetrate more fully into the interior of the carbon fiber soft felt; the vacuum-assisted treatment further improves the impregnation effect, making the bond between the impregnating agent and the carbon fiber soft felt tighter, and improving the density and performance of the composite material.

[0025] More specifically, in step (4), the drying chamber temperature is 25℃, the relative humidity is 50%, the turning interval is 2.5h, and the drying time is 48h. The temperature and humidity conditions in this step are conducive to the uniform curing of the impregnating agent, preventing quality problems caused by uneven curing or excessively rapid curing; regular turning ensures that the impregnating agent in all parts of the carbon fiber felt can be fully cured, improving the product quality stability; the drying time is 24-72h to ensure that the impregnating agent is completely cured, resulting in carbon fiber composite material products with stable performance.

[0026] More specifically, the preparation of the microcapsules includes the following steps: S1. Preparation of inner wall material Weigh gelatin and deionized water at a mass ratio of 1:10. Add the gelatin to the deionized water and heat and stir in a water bath at 55°C until the gelatin is completely dissolved to form a gelatin solution of a certain concentration. S2, Preparation of Repair Agent Mix epoxy resin and fatty amine curing agent in a 10:1 ratio, and add an appropriate amount of acetone or methyl ethyl ketone as a diluent to prepare a repair solution. The amount of diluent added is 10%-20% of the total mass of the repair solution. S3, Gelatin inner layer encapsulation The repair solution prepared in step S2 is dispersed in the gelatin solution prepared in S3. The solution is stirred at a speed of 1000-1500 r / min using a high-speed stirrer to form tiny droplets of repair solution, which are then encapsulated by the gelatin solution, forming a preliminary structure in which the repair solution is encapsulated by gelatin as the inner wall material. S4. Preparation of outer wall material Synthesis of polyurea: Toluene diisocyanate (TDI) and ethylenediamine are weighed in a molar ratio of 1:1 and added to acetone. The amount of acetone used is 3-5 times the total mass of TDI and ethylenediamine. The mixture is reacted at 60°C for 3 hours to form polyurea, so as to completely dissolve TDI and ethylenediamine. S5, polyurea outer layer The gelatin-coated repair fluid droplet dispersion system formed in step S3 is slowly added to the polyurea solution prepared in step S4 while stirring. During the stirring process, the polyurea will gradually deposit on the surface of the gelatin-coated droplets to form an outer coating. S6, Packaging The repair solution coated with a polyurea outer layer is dispersed in an aqueous medium, and sodium dodecyl sulfate is used as an emulsifier to form a water-in-oil emulsion. The amount of emulsifier is 1%-3% of the mass of the repair solution. S7. Synthesis of urea-formaldehyde resin prepolymer Weigh out 10 parts of urea, 20 parts of formaldehyde, 0.5 parts of ammonium chloride, and 1 part of melamine. First, add urea and formaldehyde to the reaction vessel and carry out a polycondensation reaction at pH 4 and temperature 70℃. Then, add ammonium chloride as a catalyst and react for 3 hours to form a urea-formaldehyde resin prepolymer. Melamine is added as a crosslinking agent during the synthesis of urea-formaldehyde resin. S8, Microcapsule formation Urea-formaldehyde resin prepolymer was dropped into an emulsion, and the urea-formaldehyde resin was polymerized on the surface of the repair solution droplets at 50°C, a stirring speed of 800 r / min, and a pH of 8 to form microcapsules. Microcapsules with a particle size of 10-100 μm were obtained by filtration and washing.

[0027] More specifically, in the preparation steps of the microcapsules, in step S2, the amount of diluent added in the preparation of the repair agent is 15%; In step S3, when forming the gelatin-encapsulated core, the high-speed mixer is stirred at a speed of 1200 r / min. In step S6, the amount of emulsifier used when the water-in-oil emulsion is formed is 2%.

[0028] In the microcapsule preparation process, step S1 utilizes the flexibility and biocompatibility of gelatin to provide a stable and compatible inner wall material environment for encapsulating the repair agent. Step S2 ensures the repair agent possesses good adhesion, curing properties, and suitable viscosity, facilitating subsequent encapsulation and rapid damage repair. Step S3 encapsulates the repair solution into uniform microdroplets, ensuring a stable repair agent content within each microcapsule. Step S4 synthesizes polyurea, whose chemical stability and mechanical strength provide reliable outer protection for the microcapsules. Step S5 slowly adds the gelatin-encapsulated droplet dispersion system to the polyurea solution with stirring, forming a bilayer wall material structure, enhancing microcapsule stability and preventing damage propagation. Step S6 uses 2% sodium dodecyl sulfate as an emulsifier to form a uniformly dispersed water-in-oil emulsion of the polyurea-encapsulated repair solution in an aqueous medium, facilitating subsequent handling and storage. Step S7 adds melamine as a crosslinking agent during the synthesis of the urea-formaldehyde resin prepolymer, improving wall material strength and stability, and enhancing adhesion to the composite matrix. Step S8 polymerizes urea-formaldehyde resin on the surface of droplets under these conditions. After filtration and washing, microcapsules with a particle size of 10-100 μm are obtained. This process ensures the overall quality and performance of the microcapsules, enabling them to effectively protect the repair agent and release it promptly when the material is damaged to achieve self-repair function.

[0029] More specifically, in step S8, when the urea-formaldehyde resin prepolymer is dropped into the water-in-oil emulsion to form microcapsules, γ-aminopropyltriethoxysilane is added at 3% of the total mass of the wall material. First, γ-aminopropyltriethoxysilane is dissolved in ethanol to prepare a 30% solution, and then this solution is slowly added dropwise or added to the reaction system in which the microcapsules are being formed.

[0030] More specifically, in step S8, the concentration of the γ-aminopropyltriethoxysilane solution is 5%-15%. This solution is slowly added dropwise or added to the reaction system in which the microcapsules are forming, and then the reaction is carried out at 40°C for 1.5 hours.

[0031] More specifically, in the microcapsule preparation steps, the concentration of the γ-aminopropyltriethoxysilane solution is 10%.

[0032] Adding γ-aminopropyltriethoxysilane solutions of different concentrations and reacting them in step S8 of microcapsule preparation yields multiple benefits, which are analyzed in detail below with reference to different concentrations: The overall effects of adding γ-aminopropyltriethoxysilane are twofold: First, it improves interfacial compatibility. The γ-aminopropyltriethoxysilane molecule contains amino and ethoxy groups. The amino group has certain reactivity and can chemically react with certain groups in the microcapsule wall material (such as urea-formaldehyde resin, polyurea, gelatin, etc.) and the composite matrix. The ethoxy group can hydrolyze to form silanol groups, which can form chemical bonds with hydroxyl groups on the material surface. In this way, γ-aminopropyltriethoxysilane can form a "bridge" between the microcapsules and the composite matrix, improving interfacial compatibility and allowing the microcapsules to be better dispersed in the matrix, thus improving the overall uniformity and stability of the composite material. Second, it enhances bonding strength. At the interface between the microcapsules and the matrix, the chemical bonds formed by γ-aminopropyltriethoxysilane significantly enhance the bonding strength between the microcapsules and the matrix. When the material is subjected to external forces, this strong bonding strength can effectively transfer stress, reduce debonding between the microcapsules and the matrix, and improve the mechanical properties of the composite material, such as tensile strength and flexural strength. On the other hand, to improve the repair effect, when the material is damaged, the microcapsules rupture and release the repair agent. γ-aminopropyltriethoxysilane can promote the binding of the repair agent to the damaged site. It can form a good bond between the repair agent and the damage interface, allowing the repair agent to adhere more firmly to the damaged area, thereby improving the repair effect and extending the service life of the material.

[0033] The effects of a 30% γ-aminopropyltriethoxysilane solution are twofold: Firstly, it allows for efficient addition. By preparing a 30% solution and slowly adding it dropwise to the reaction system, this higher concentration reduces the volume of solution during addition, ensuring accurate dosage and facilitating operation and control. Secondly, the higher concentration allows for faster diffusion and reaction within the reaction system, improving reaction efficiency and enabling γ-aminopropyltriethoxysilane to quickly exert its effect of improving interfacial properties.

[0034] When the concentration of γ-aminopropyltriethoxysilane solution is within the range of 5%-15%, its diffusion and reaction rate in the reaction system are relatively moderate, facilitating precise control of the reaction process. This moderate reaction rate allows γ-aminopropyltriethoxysilane to fully react with the microcapsule wall material and other components in the reaction system, while avoiding agglomeration or other adverse reactions caused by excessively high local concentrations due to excessively rapid reactions, thus ensuring the stability of the microcapsule quality and performance. Within this concentration range, γ-aminopropyltriethoxysilane can form a uniform modified layer on the surface of the microcapsule wall material, further optimizing the interfacial properties between the microcapsule and the matrix. Different concentrations can be adjusted according to specific material systems and performance requirements to achieve the best interfacial modification effect, thereby improving the overall performance of the composite material.

[0035] A concentration of 10% is an ideal choice within the 5%-15% concentration range mentioned above. This concentration ensures that γ-aminopropyltriethoxysilane has sufficient active ingredients in the reaction system to achieve good interfacial modification effects, while avoiding the adverse effects of excessively high concentrations, such as increased costs and impaired microcapsule dispersibility. Reacting at 40℃ for 1.5 hours, the 10% concentration solution fully participates in the reaction, optimizing the interfacial bonding between the microcapsules and the matrix, thereby significantly improving the performance and durability of the composite material.

[0036] The following are several preferred examples compared with Example 1: Example 1: The stirring time in step (2) is 20 min, and the vacuum degree in step (3) is 0.05 MPa with vacuum assistance and the impregnation temperature is 50℃.

[0037] Preferred Example 1: The stirring time in step (2) is 15 min, and the vacuum degree in step (3) is 0.05 MPa with vacuum assistance and the impregnation temperature is 50 °C.

[0038] Preferred Example 2: The stirring time in step (2) is 25 min, and the vacuum degree in step (3) is 0.05 MPa with vacuum assistance and the impregnation temperature is 50 °C.

[0039] Preferred Example 3: The stirring time in step (2) is 20 min, and the vacuum degree in step (3) is 0.07 MPa with vacuum assistance and the impregnation temperature is 50 °C.

[0040] Preferred Example 4: The stirring time in step (2) is 20 min, and the vacuum degree in step (3) is 0.09 MPa with vacuum assistance and the impregnation temperature is 50 °C.

[0041] Preferred Example 5: The stirring time in step (2) is 20 min, and the vacuum degree in step (3) is 0.05 MPa with vacuum assistance and the impregnation temperature is 45℃.

[0042] Preferred Example 6: The stirring time in step (2) is 20 min, and the vacuum degree in step (3) is 0.05 MPa with vacuum assistance and the impregnation temperature is 55 °C.

[0043] Preferred Example 7: The stirring time in step (2) is 15 min, and the vacuum degree in step (3) is 0.07 MPa with vacuum assistance and the impregnation temperature is 45℃.

[0044] Preferred Example 8: The stirring time in step (2) is 25 min, and the vacuum degree in step (3) is 0.09 MPa with vacuum assistance and the impregnation temperature is 55 °C.

[0045] Preferred Example 9: The stirring time in step (2) is 20 min, and the vacuum degree in step (3) is 0.08 MPa with vacuum assistance and the impregnation temperature is 52℃.

[0046]

[0047] The experimental data above show that in the preferred example 7, the microcapsule breakage rate was reduced to 3%, the tensile strength reached 180 MPa, and the self-healing efficiency was 45%, all of which are better than those of preferred examples 1-6.

[0048] In preferred example 8, the microcapsule breakage rate was further reduced to 2%, the release effect of the repair agent reached 38%, the tensile strength was 190 MPa, and the self-repair efficiency was increased to 50%. All performances were superior to preferred examples 1-7.

[0049] In Preferred Example 9, the microcapsule breakage rate was also 2%, the repair agent release effect was optimal at 40%, the tensile strength was as high as 200 MPa, the flexural strength was 170 MPa, and the self-healing efficiency also reached the highest of 55%. Preferred Example 9 achieved the best optimization results, showing the best performance in terms of microcapsule stability, carbon fiber soft felt mechanical properties, and self-healing properties.

[0050] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from the spirit or essential characteristics of the invention. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, it is intended that all variations falling within the meaning and scope of equivalents of the claims be included within the present invention.

Claims

1. A method for impregnating and drying carbon fiber soft felt, characterized in that, Includes the following steps: (1) Pretreatment of carbon fiber soft felt The carbon fiber felt was soaked in a 30%-40% nitric acid solution for 3-6 hours; (2) Preparation of impregnating agent The impregnating agent comprises, by weight, 6-7 parts epoxy resin, 1-2 parts aliphatic amine curing agent, 0.5-0.8 parts n-butanol, 0.8-1.2 parts rubber elastomer toughening agent, and 0.5-0.8 parts microcapsules. The components are stirred in a mixing container at a speed of 300-500 r / min for 15-30 min to ensure uniform mixing. The wall material of the microcapsule has a multi-layer structure, with an inner layer of flexible gelatin and an outer layer of polyurea. Melamine is added as a crosslinking agent during the synthesis of the wall material. The microcapsule contains a repair agent, which is a combination of epoxy resin and curing agent. (3) Impregnation operation Pour the impregnating agent prepared in step (2) into the impregnation tank, and use a paddle mixer to stir intermittently at a stirring speed of 200-300 r / min. Stir for 5 minutes and stop for 2 minutes. Control the impregnation temperature at 40-60℃ to ensure that the impregnating agent is evenly distributed and maintains good fluidity. The carbon fiber felt is completely immersed in the impregnation tank for 15-30 minutes. The impregnation tank is placed in a sealed container, and nitrogen is introduced into the sealed container to increase the air pressure inside the container. The pressure is precisely controlled using a pressure sensor and a pressure regulating valve to maintain it within the range of 0.1-0.3 MPa, ensuring that the impregnating agent fully penetrates into the interior of the carbon fiber felt. Vacuum assistance is used during the impregnation process. The carbon fiber felt and impregnating agent are placed in a vacuum environment with a vacuum degree of 0.05-0.1MPa for 5-10 minutes and then restored to normal pressure or slightly positive pressure. The slightly positive pressure range is 0.01-0.03MPa, which further improves the impregnation effect. (4) Drying treatment Remove the impregnated carbon fiber felt from the impregnation tank and allow the excess impregnating agent to drip for 5-10 minutes. Then, lay the carbon fiber felt flat on the drying rack in the drying room. The temperature of the drying room should be 20-30℃ and the relative humidity should not exceed 60%. Turn the carbon fiber felt over every 2-3 hours and let it dry for 24-72 hours until the impregnating agent is completely cured.

2. The method for impregnating and drying carbon fiber soft felt according to claim 1, characterized in that: In step (1), the concentration of the nitric acid solution is 35%, and the carbon fiber felt is soaked in it for 4 hours.

3. The method for impregnating and drying carbon fiber soft felt according to claim 1, characterized in that: In step (2), the impregnating agent contains 6.5 parts epoxy resin, 1.5 parts fatty amine curing agent, 0.6 parts n-butanol, 1 part rubber elastomer toughening agent, and 0.6 parts microcapsules; the stirring speed is 400 r / min, and the stirring time is 20 min.

4. The method for impregnating and drying carbon fiber soft felt according to claim 1, characterized in that: In step (3), the stirring speed of the paddle agitator is 250 r / min, the immersion temperature is 50℃, the immersion time is 20 min, the applied pressure is 0.2 MPa, the vacuum environment treatment time is 8 min, and the micro positive pressure after recovery is 0.02 MPa.

5. The method for impregnating and drying carbon fiber soft felt according to claim 1, characterized in that: In step (4), the temperature of the drying room is 25°C, the relative humidity is 50%, the turning interval is 2.5h, and the drying time is 48h.

6. The method for impregnating and drying carbon fiber soft felt according to claim 1, characterized in that: The preparation of the microcapsules includes the following steps: S1. Preparation of inner wall material Weigh gelatin and deionized water at a mass ratio of 1:

10. Add the gelatin to the deionized water and heat and stir in a water bath at 55°C until the gelatin is completely dissolved to form a gelatin solution of a certain concentration. S2, Preparation of Repair Agent Mix epoxy resin and fatty amine curing agent in a 10:1 ratio, and add an appropriate amount of acetone or methyl ethyl ketone as a diluent to prepare a repair solution. The amount of diluent added is 10%-20% of the total mass of the repair solution. S3, Gelatin inner layer encapsulation The repair solution prepared in step S2 is dispersed in the gelatin solution prepared in S3. The solution is stirred at a speed of 1000-1500 r / min using a high-speed stirrer to form tiny droplets of repair solution, which are then encapsulated by the gelatin solution, forming a preliminary structure in which the repair solution is encapsulated by gelatin as the inner wall material. S4. Preparation of outer wall material Synthesis of polyurea: Toluene diisocyanate (TDI) and ethylenediamine are weighed in a molar ratio of 1:1 and added to acetone. The amount of acetone used is 3-5 times the total mass of TDI and ethylenediamine. The mixture is reacted at 60°C for 3 hours to form polyurea, so as to completely dissolve TDI and ethylenediamine. S5, polyurea outer layer The gelatin-coated repair fluid droplet dispersion system formed in step S3 is slowly added to the polyurea solution prepared in step S4 while stirring. During the stirring process, the polyurea will gradually deposit on the surface of the gelatin-coated droplets to form an outer coating. S6, Packaging The repair solution coated with a polyurea outer layer is dispersed in an aqueous medium, and sodium dodecyl sulfate is used as an emulsifier to form a water-in-oil emulsion. The amount of emulsifier is 1%-3% of the mass of the repair solution. S7. Synthesis of urea-formaldehyde resin prepolymer Weigh out 10 parts of urea, 20 parts of formaldehyde, 0.5 parts of ammonium chloride, and 1 part of melamine. First, add urea and formaldehyde to the reaction vessel and carry out a polycondensation reaction at pH 4 and temperature 70℃. Then, add ammonium chloride as a catalyst and react for 3 hours to form a urea-formaldehyde resin prepolymer. Melamine is added as a crosslinking agent during the synthesis of urea-formaldehyde resin. S8, Microcapsule formation Urea-formaldehyde resin prepolymer was dropped into an emulsion, and the urea-formaldehyde resin was polymerized on the surface of the repair solution droplets at 50°C, a stirring speed of 800 r / min, and a pH of 8 to form microcapsules. Microcapsules with a particle size of 10-100 μm were obtained by filtration and washing.

7. The method for impregnating and drying carbon fiber soft felt according to claim 6, characterized in that: In step S2, the amount of diluent added in the preparation of the repair agent is 15%; In step S3, when forming the gelatin-encapsulated core, the high-speed mixer is stirred at a speed of 1200 r / min. In step S6, the amount of emulsifier used when the water-in-oil emulsion is formed is 2%.

8. The method for impregnating and drying carbon fiber soft felt according to claim 7, characterized in that: In step S8, when the urea-formaldehyde resin prepolymer is dropped into the water-in-oil emulsion to form microcapsules, γ-aminopropyltriethoxysilane is added at 3% of the total mass of the wall material. First, γ-aminopropyltriethoxysilane is dissolved in ethanol to prepare a 30% solution, and then this solution is slowly added dropwise or added to the reaction system in which the microcapsules are being formed.

9. The method for impregnating and drying carbon fiber soft felt according to claim 8, characterized in that: In step S8, the concentration of the γ-aminopropyltriethoxysilane solution is 5%-15%. This solution is slowly added dropwise or added to the reaction system in which microcapsules are forming, and then the reaction is carried out at 40°C for 1.5 h.

10. The method for impregnating and drying carbon fiber soft felt according to claim 9, characterized in that: The concentration of the γ-aminopropyltriethoxysilane solution is 10%.

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