Preparation method of thermal insulation carbon fiber thermal insulation material

Abstract

The application discloses a preparation method of a heat-insulating carbon fiber thermal insulation material and belongs to the technical field of carbon fiber modification. Carbon fibers are subjected to oxidation treatment by being immersed in a nitric acid solution to obtain surface pretreated carbon fibers; an original tetrapropyl orthosilicate hydrolysate and an activated levodopa dispersion liquid are mixed, solvent water is removed by evaporation under reduced pressure, and then, an organic silicon modified levodopa composite liquid is obtained by reacting for 18h to 22h in a temperature environment of 20 DEG C to 25 DEG C; the organic silicon modified levodopa composite liquid is adjusted to a pH of 8.0 to 9.0, then coated on the surface of the surface pretreated carbon fibers and subjected to ultrasonic treatment, and then, modified carbon fibers are obtained by standing, adsorbing and cross-linking; and the modified carbon fibers are subjected to high-temperature pyrolysis to obtain the heat-insulating carbon fiber thermal insulation material. Through the treatment, the modified carbon fibers have good high-temperature oxidation resistance.

Description

Technical Field

[0001] The invention belongs to the technical field of carbon fiber modification, and particularly relates to a method for preparing a heat-insulating carbon fiber thermal insulation material. Background Art

[0002] With the rapid advancement of science and technology, the demand for specialized material properties is increasing. Carbon fiber, due to its excellent mechanical properties, high specific modulus, high specific strength, low thermal expansion coefficient, and excellent toughness, is widely used in a variety of fields, including biology, chemical engineering, automotive, machinery, aviation, and aerospace. By combining carbon fiber with different substrate materials, carbon fiber-reinforced composites with specific functions can be prepared. For example, carbon / carbon composites, based on carbon, are used in applications requiring high mechanical performance due to their low thermal expansion coefficient, high elasticity, and high strength. Their excellent heat resistance and low weight make them a valuable tool in metal heat treatment. However, carbon fiber-reinforced composites require inert gas protection to fully realize these important properties. This is primarily due to the poor high-temperature oxidation resistance of carbon fiber. At high temperatures, a series of active sites exist on the carbon fiber surface. Oxygen diffuses into the fiber surface, binds to these active sites, and reacts to form carbon oxides, causing the fiber to lose weight. This is the nature of carbon fiber oxidation, resulting in suboptimal performance or even failure of the resulting matrix composite. This characteristic limits the application of carbon fiber. Therefore, under the premise of ensuring the performance of carbon fiber, improving the antioxidant ability of carbon fiber in an aerobic environment can greatly expand the application of carbon fiber in various fields and improve the stability of carbon fiber as a high-temperature protective material and ablative material reinforcement.

[0003] At present, the research on improving the antioxidant properties of carbon fiber is mainly carried out from two aspects: (1) Matrix modification technology: improving the antioxidant properties of carbon fiber itself, such as graphitization; (2): improving the antioxidant properties by modifying the coating on the carbon fiber surface. Currently, the commonly used surface coating treatments for carbon fiber include oxidation, electroplating, chemical plating, chemical vapor deposition and ion spray sputtering; commonly used coating materials include metal coatings such as Ni, Cu, Fe, Co, Al, Ag and non-metallic coatings such as SiC, Si, B. However, before the carbon fiber is surface treated, the carbon fiber surface has a colloid layer, the surface is smooth, lacks active functional groups, and is very inert. When compounded with the surface coating matrix, the wettability is poor, there are many interface defects, and the interface bonding strength is insufficient, which affects many properties of the modified carbon fiber.

[0004] Carbon fiber has a good application prospect in the field of thermal insulation due to its excellent low thermal expansion coefficient. Therefore, how to improve the oxidation resistance of carbon fiber in high temperature environments is of great significance to the improvement of its application in the field of thermal insulation in high temperature environments. Summary of the Invention

[0005] In response to the shortcomings of the prior art, the present invention addresses the technical problems raised in the background art by constructing a weakly alkaline organosilicon-modified levodopa composite solution, which is then applied to the surface of pretreated carbon fibers for polymerization and adhesion to obtain modified carbon fibers. This is then treated at high temperature to produce a heat-insulating carbon fiber thermal insulation material. Specifically, the present invention's technical solutions include the following:

[0006] A method for preparing a heat-insulating carbon fiber thermal insulation material, the method comprising the following steps:

[0007] The carbon fibers are immersed in a nitric acid solution for oxidation treatment to obtain surface pretreated carbon fibers;

[0008] The tetrapropyl orthosilicate hydrolyzate and the activated levodopa dispersion are mixed and evaporated under reduced pressure to remove the solvent water, followed by a reaction at a temperature of 20°C to 25°C for 18 hours to 22 hours to obtain an organosilicon-modified levodopa composite solution;

[0009] The organosilicon-modified levodopa composite solution is adjusted to a pH of 8.0-9.0, and then coated on the surface of the surface-pretreated carbon fiber and subjected to an ultrasonic treatment at a power of 300W-400W for 10-15 minutes, followed by standing for adsorption and crosslinking for 20-30 hours to obtain the modified carbon fiber;

[0010] The modified carbon fiber is pyrolyzed at high temperature to obtain the heat-insulating carbon fiber thermal insulation material.

[0011] Furthermore, the mass concentration of the nitric acid solution is 40% to 45%. The purpose of nitric acid impregnation is to obtain reactive oxygen-containing groups on the inert surface of the carbon fiber, so that when the organosilicon-modified levodopa composite liquid is coated later, the organosilicon-modified levodopa composite liquid loaded with organosilicon can be fixed on the surface of the modified carbon fiber through the synergistic coordination of hydrogen bond adsorption and covalent bond cross-linking.

[0012] Furthermore, the conditions of the immersion oxidation treatment include a treatment temperature of 40° C. to 50° C. and a treatment time of 50 min to 55 min.

[0013] Furthermore, the preparation method of the tetrapropyl orthosilicate hydrolyzate comprises the following steps:

[0014] After tetrapropyl orthosilicate is dispersed in deionized water, acid is added to adjust the pH to 2.5-3.0, and then the temperature is raised to 50° C.-60° C. and reacted for 2 h-3 h to obtain the tetrapropyl orthosilicate hydrolyzate.

[0015] Furthermore, the preparation method of the activated levodopa dispersion comprises the following steps:

[0016] Levodopa and a carboxyl activator are dispersed in anhydrous dichloromethane and placed in a 0° C. environment for pre-activation treatment for 15 to 20 minutes to obtain the activated levodopa dispersion.

[0017] Furthermore, the molar ratio of levodopa to the carboxyl activator is 1:1.5-2.

[0018] Furthermore, the carboxyl activator is composed of EDC hydrochloride and DMAP in a molar ratio of 1:0.5~1.

[0019] Furthermore, the weight ratio of the tetrapropyl orthosilicate hydrolyzate to the activated levodopa dispersion is 1:5-10.

[0020] Furthermore, the high-temperature pyrolysis conditions include a pyrolysis temperature of 1100° C. to 1300° C. and a pyrolysis time of 60 min to 80 min.

[0021] Compared with the prior art, the present invention has the following beneficial effects:

[0022] The present invention uses levodopa as one of its raw materials, utilizing its ability to form poly-levodopa with excellent adhesion after self-polymerization. The carboxyl groups on the levodopa are first activated, followed by covalent condensation, esterification, and crosslinking with the hydrolyzate containing silanol groups obtained by acid hydrolysis of tetrapropyl orthosilicate, to form an organosilicon-modified levodopa composite. The carbon fiber surface is then oxidized using nitric acid at a specific concentration under specific conditions, altering its surface inertness and generating active oxygen-containing groups (hydroxyl and carboxyl groups), thereby producing surface-pretreated carbon fibers. The organosilicon-modified levodopa composite is then adjusted to a weakly alkaline environment and applied to the surface of the pretreated carbon fibers, causing the organosilicon-modified levodopa composite to self-polymerize. The composite adheres to the surface of the pretreated carbon fibers through physical and chemical adsorption with the active oxygen-containing groups on the pretreated carbon fibers, resulting in modified carbon fibers. The modified carbon fiber is then taken out and dried, and then subjected to high-temperature treatment to remove the poly-levodopa on the surface of the modified carbon fiber, while retaining the silicon dioxide on the surface of the modified carbon fiber to obtain a heat-insulating carbon fiber thermal insulation material. Silicon dioxide has good resistance to high-temperature oxidation, so that the prepared heat-insulating carbon fiber thermal insulation material has good resistance to high-temperature oxidation. DETAILED DESCRIPTION

[0023] The following will clearly and completely describe the technical solutions of the present invention through the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without making any creative efforts shall fall within the scope of protection of the present invention.

[0024] Unless otherwise specified, the raw materials and reagents used in the present invention are commercially available or can be prepared by known methods.

[0025] The carbon fiber was purchased from Weihai Guangwei Composite Materials Co., Ltd.

[0026] Preparation Example 1:

[0027] The preparation method of tetrapropyl orthosilicate hydrolyzate specifically comprises the following steps:

[0028] Tetrapropyl orthosilicate and deionized water were mixed in a flask at a weight ratio of 1:0.5. The mixture was then placed in an ultrasonic disperser and subjected to ultrasonic dispersion at 200 W for 20 minutes to obtain a tetrapropyl orthosilicate dispersion. The pH of the tetrapropyl orthosilicate dispersion was adjusted to 2.5 with hydrochloric acid, and then heated to 50°C for hydrolysis for 2 hours. The pH was then adjusted to neutral and stored to obtain a tetrapropyl orthosilicate hydrolyzed solution.

[0029] Preparation Example 2:

[0030] The preparation method of tetrapropyl orthosilicate hydrolyzate specifically comprises the following steps:

[0031] Tetrapropyl orthosilicate and deionized water were mixed in a flask at a weight ratio of 1:0.7. The mixture was then placed in an ultrasonic disperser and subjected to ultrasonic dispersion at 200 W for 20 minutes to obtain a tetrapropyl orthosilicate dispersion. The pH of the tetrapropyl orthosilicate dispersion was adjusted to 2.5 with hydrochloric acid, and then heated to 55°C for hydrolysis for 2.5 hours. The pH was then adjusted to neutral and stored to obtain a tetrapropyl orthosilicate hydrolyzed solution.

[0032] Preparation Example 3:

[0033] The preparation method of tetrapropyl orthosilicate hydrolyzate specifically comprises the following steps:

[0034] Tetrapropyl orthosilicate and deionized water were mixed in a flask at a weight ratio of 1:0.9. The mixture was then placed in an ultrasonic disperser and subjected to ultrasonic dispersion at 200 W for 20 minutes to obtain a tetrapropyl orthosilicate dispersion. The pH of the tetrapropyl orthosilicate dispersion was adjusted to 3.0 with hydrochloric acid, and then heated to 60°C for hydrolysis for 3 hours. The pH was then adjusted to neutral and stored to obtain a tetrapropyl orthosilicate hydrolyzed solution.

[0035] Preparation Example 4:

[0036] The preparation method of ethyl orthosilicate hydrolyzate specifically includes the following steps:

[0037] TEOS and deionized water were mixed in a flask at a weight ratio of 1:0.9. The mixture was then placed in an ultrasonic disperser and subjected to ultrasonic dispersion at 200 W for 20 minutes to obtain a TEOS dispersion. The pH of the TEOS dispersion was adjusted to 3.0 with hydrochloric acid, and then heated to 60°C for hydrolysis for 3 hours. The pH was then adjusted to neutral and stored to obtain a TEOS hydrolyzed solution.

[0038] Preparation Example 5:

[0039] The preparation method of tetrabutyl orthosilicate hydrolyzate specifically includes the following steps:

[0040] Tetrabutyl orthosilicate and deionized water were mixed in a flask at a weight ratio of 1:0.9. The mixture was then placed in an ultrasonic disperser and subjected to ultrasonic dispersion at 200 W for 20 minutes to obtain a tetrabutyl orthosilicate dispersion. The pH of the tetrabutyl orthosilicate dispersion was adjusted to 3.0 with hydrochloric acid, and then heated to 60°C for hydrolysis for 3 hours. The pH was then adjusted to neutral and stored to obtain a tetrabutyl orthosilicate hydrolyzed solution.

[0041] Preparation Example 6:

[0042] The preparation method of activated levodopa dispersion specifically includes the following steps:

[0043] 0.1 mol of levodopa was weighed and added to 400 ml of anhydrous dichloromethane. The mixture was then dispersed using an ultrasonic disperser at 400 W for 15 minutes to obtain a levodopa dispersion. A carboxyl activator consisting of 0.1 mol of EDC hydrochloride and 0.05 mol of DMAP was added to the levodopa dispersion. The mixture was then stirred at 0°C for 15 minutes to obtain a pre-activation levodopa dispersion.

[0044] Preparation Example 7:

[0045] The preparation method of activated levodopa dispersion specifically includes the following steps:

[0046] 0.1 mol of levodopa was weighed and added to 400 ml of anhydrous dichloromethane. The mixture was then dispersed using an ultrasonic disperser at 400 W for 15 minutes to obtain a levodopa dispersion. A carboxyl activator consisting of 0.1 mol of EDC hydrochloride and 0.08 mol of DMAP was added to the levodopa dispersion. The mixture was then stirred at 0°C for 17 minutes to obtain a pre-activation levodopa dispersion.

[0047] Preparation Example 8:

[0048] The preparation method of activated levodopa dispersion specifically includes the following steps:

[0049] Weigh 0.1 mol of levodopa into 400 ml of anhydrous dichloromethane. Disperse the mixture using an ultrasonic disperser at 400 W for 15 minutes to obtain a levodopa dispersion. Add a carboxyl activator consisting of 0.1 mol of EDC hydrochloride and 0.1 mol of DMAP to the levodopa dispersion. Stir and pre-activate the mixture at 0°C for 20 minutes to obtain an activated levodopa dispersion.

[0050] Preparation Example 9:

[0051] The preparation method of activated dopamine hydrochloride dispersion specifically includes the following steps:

[0052] 0.1 mol of dopamine hydrochloride was weighed and added to 400 ml of anhydrous dichloromethane. The mixture was then dispersed using an ultrasonic disperser at 400 W for 15 minutes to obtain a dopamine hydrochloride dispersion. A carboxyl activator consisting of 0.1 mol of EDC hydrochloride and 0.1 mol of DMAP was added to the dopamine hydrochloride dispersion. The mixture was then stirred at 0°C for 20 minutes to pre-activate the dopamine hydrochloride dispersion.

[0053] Example 1:

[0054] A method for preparing a heat-insulating carbon fiber thermal insulation material specifically includes the following steps:

[0055] The carbon fiber was completely immersed in a nitric acid solution with a mass concentration of 40%, and then placed in a water bath at a temperature of 40°C for heating and oxidation treatment for 50 minutes. After the oxidation treatment was completed, the carbon fiber was removed and the surface nitric acid solution was rinsed with a large amount of distilled water until the pH of the rinse water was neutral. It was then placed in a vacuum drying oven at 70°C and dried to constant weight to obtain surface pretreated carbon fiber;

[0056] 1 part by weight of the tetrapropyl orthosilicate hydrolyzate obtained in Preparation Example 1 and 5 parts by weight of the activated levodopa dispersion obtained in Preparation Example 6 were mixed and stirred to obtain a mixed system, and then a reduced pressure evaporator was used to remove water from the mixed system, and then the mixture was controlled to react at a temperature of 20° C. for 18 hours to obtain an organosilicon-modified levodopa composite liquid; the pH of the organosilicon-modified levodopa composite liquid was adjusted to 8.0 with ammonia water, and then the composite liquid was coated on the surface of the surface pretreated carbon fiber. After the coating was completed, the composite liquid was placed in an ultrasonic power environment of 300 W for 10 minutes, and then allowed to stand at room temperature for adsorption and crosslinking for 20 hours to obtain a modified carbon fiber;

[0057] After the static adsorption is completed, the modified carbon fiber is placed in an oven at 80°C to dry until the surface is hardened, then placed in a tubular furnace and heated to 1100°C at a heating rate of 10°C / min. It is pyrolyzed in this temperature environment for 60 minutes and then naturally cooled to room temperature to obtain an insulating carbon fiber thermal insulation material.

[0058] Example 2:

[0059] A method for preparing a heat-insulating carbon fiber thermal insulation material specifically includes the following steps:

[0060] The carbon fiber was completely immersed in a nitric acid solution with a mass concentration of 40%, and then placed in a water bath at a temperature of 45°C for 50 minutes for heating and oxidation treatment. After the oxidation treatment was completed, the carbon fiber was removed and the surface nitric acid solution was rinsed with a large amount of distilled water until the pH of the rinse water was neutral. It was then placed in a vacuum drying oven at 70°C and dried to constant weight to obtain surface pretreated carbon fiber;

[0061] 1 part by weight of the tetrapropyl orthosilicate hydrolyzate obtained in Preparation Example 2 and 6 parts by weight of the activated levodopa dispersion obtained in Preparation Example 7 were mixed and stirred to obtain a mixed system, and then a reduced pressure evaporator was used to remove water from the mixed system, and then the mixture was controlled to react at a temperature of 20° C. for 19 hours to obtain an organosilicon-modified levodopa composite liquid; the pH of the organosilicon-modified levodopa composite liquid was adjusted to 8.0 with ammonia water, and then the composite liquid was coated on the surface of the surface pretreated carbon fiber. After the coating was completed, the composite liquid was placed in an ultrasonic power environment of 350 W for 10 minutes, and then allowed to stand at room temperature for adsorption and crosslinking for 24 hours to obtain a modified carbon fiber;

[0062] After the static adsorption is completed, the modified carbon fiber is placed in an oven at 80°C to dry until the surface is hardened, then placed in a tubular furnace and heated to 1200°C at a heating rate of 10°C / min. It is pyrolyzed in this temperature environment for 70 minutes and then naturally cooled to room temperature to obtain an insulating carbon fiber thermal insulation material.

[0063] Example 3:

[0064] A method for preparing a heat-insulating carbon fiber thermal insulation material specifically includes the following steps:

[0065] The carbon fiber was completely immersed in a nitric acid solution with a mass concentration of 45%, and then placed in a water bath at a temperature of 45°C for 55 minutes for heating and oxidation treatment. After the oxidation treatment was completed, the carbon fiber was removed and the surface nitric acid solution was rinsed with a large amount of distilled water until the pH of the rinse water was neutral. It was then placed in a vacuum drying oven at 70°C and dried to constant weight to obtain surface pretreated carbon fiber;

[0066] 1 part by weight of the tetrapropyl orthosilicate hydrolyzate obtained in Preparation Example 3 and 8 parts by weight of the activated levodopa dispersion obtained in Preparation Example 8 were mixed and stirred to obtain a mixed system, and then a reduced pressure evaporator was used to remove water from the mixed system, and then the mixture was controlled to react at a temperature of 25° C. for 20 hours to obtain an organosilicon-modified levodopa composite liquid; the pH of the organosilicon-modified levodopa composite liquid was adjusted to 8.5 with ammonia water, and then the composite liquid was coated on the surface of the surface pretreated carbon fiber. After the coating was completed, the composite liquid was placed in an ultrasonic power environment of 350 W for 15 minutes, and then allowed to stand for adsorption and crosslinking at room temperature for 28 hours to obtain a modified carbon fiber;

[0067] After the static adsorption is completed, the modified carbon fiber is placed in an oven at 80°C to dry until the surface is hardened, then placed in a tubular furnace and heated to 1300°C at a heating rate of 10°C / min. It is pyrolyzed in this temperature environment for 80 minutes and then naturally cooled to room temperature to obtain an insulating carbon fiber thermal insulation material.

[0068] Example 4:

[0069] A method for preparing a heat-insulating carbon fiber thermal insulation material specifically includes the following steps:

[0070] The carbon fiber was completely immersed in a nitric acid solution with a mass concentration of 45%, and then placed in a water bath at a temperature of 50°C for 55 minutes for heating and oxidation treatment. After the oxidation treatment, the carbon fiber was removed and the surface nitric acid solution was rinsed with a large amount of distilled water until the pH of the rinse water was neutral. It was then placed in a vacuum drying oven at 70°C and dried to constant weight to obtain surface pretreated carbon fiber;

[0071] 1 part by weight of the tetrapropyl orthosilicate hydrolyzate obtained in Preparation Example 3 and 10 parts by weight of the activated levodopa dispersion obtained in Preparation Example 8 were mixed and stirred to obtain a mixed system, and then a reduced pressure evaporator was used to remove water from the mixed system, and then the mixture was controlled to react at a temperature of 25° C. for 22 hours to obtain an organosilicon-modified levodopa composite liquid; the pH of the organosilicon-modified levodopa composite liquid was adjusted to 9.0 with ammonia water, and then the composite liquid was coated on the surface of the surface pretreated carbon fiber. After the coating was completed, the composite liquid was placed in an ultrasonic power environment of 400 W for 15 minutes, and then allowed to stand for adsorption and crosslinking at room temperature for 30 hours to obtain a modified carbon fiber;

[0072] After the static adsorption is completed, the modified carbon fiber is placed in an oven at 80°C to dry until the surface is hardened, then placed in a tubular furnace and heated to 1300°C at a heating rate of 10°C / min. It is pyrolyzed in this temperature environment for 80 minutes and then naturally cooled to room temperature to obtain an insulating carbon fiber thermal insulation material.

[0073] Comparative Example 1:

[0074] A method for preparing a heat-insulating carbon fiber thermal insulation material specifically includes the following steps:

[0075] The carbon fiber was completely immersed in a nitric acid solution with a mass concentration of 45%, and then placed in a water bath at a temperature of 50°C for 55 minutes for heating and oxidation treatment. After the oxidation treatment, the carbon fiber was removed and the surface nitric acid solution was rinsed with a large amount of distilled water until the pH of the rinse water was neutral. It was then placed in a vacuum drying oven at 70°C and dried to constant weight to obtain surface pretreated carbon fiber;

[0076] 1 part by weight of the ethyl orthosilicate hydrolyzate obtained in Preparation Example 4 and 10 parts by weight of the activated levodopa dispersion obtained in Preparation Example 8 were mixed and stirred to obtain a mixed system, and then a reduced pressure evaporator was used to remove water from the mixed system, and then the mixture was controlled to react at a temperature of 25° C. for 22 hours to obtain an organosilicon-modified levodopa composite liquid; the pH of the organosilicon-modified levodopa composite liquid was adjusted to 9.0 with ammonia water, and then the composite liquid was coated on the surface of the surface pretreated carbon fiber. After the coating was completed, the composite liquid was placed in an ultrasonic power environment of 400 W for 15 minutes, and then allowed to stand for adsorption and crosslinking at room temperature for 30 hours to obtain a modified carbon fiber;

[0077] After the static adsorption is completed, the modified carbon fiber is placed in an oven at 80°C to dry until the surface is hardened, then placed in a tubular furnace and heated to 1300°C at a heating rate of 10°C / min. It is pyrolyzed in this temperature environment for 80 minutes and then naturally cooled to room temperature to obtain an insulating carbon fiber thermal insulation material.

[0078] Comparative Example 2:

[0079] A method for preparing a heat-insulating carbon fiber thermal insulation material specifically includes the following steps:

[0080] The carbon fiber was completely immersed in a nitric acid solution with a mass concentration of 45%, and then placed in a water bath at a temperature of 50°C for 55 minutes for heating and oxidation treatment. After the oxidation treatment, the carbon fiber was removed and the surface nitric acid solution was rinsed with a large amount of distilled water until the pH of the rinse water was neutral. It was then placed in a vacuum drying oven at 70°C and dried to constant weight to obtain surface pretreated carbon fiber;

[0081] 1 part by weight of the tetrabutyl orthosilicate hydrolyzate obtained in Preparation Example 5 and 10 parts by weight of the activated levodopa dispersion obtained in Preparation Example 8 were mixed and stirred to obtain a mixed system, and then a reduced pressure evaporator was used to remove water from the mixed system, and then the mixture was controlled to react at a temperature of 25° C. for 22 hours to obtain an organosilicon-modified levodopa composite liquid; the pH of the organosilicon-modified levodopa composite liquid was adjusted to 9.0 with ammonia water, and then the composite liquid was coated on the surface of the surface pretreated carbon fiber. After the coating was completed, the composite liquid was placed in an ultrasonic power environment of 400 W for 15 minutes, and then allowed to stand for adsorption and crosslinking at room temperature for 30 hours to obtain a modified carbon fiber;

[0082] After the static adsorption is completed, the modified carbon fiber is placed in an oven at 80°C to dry until the surface is hardened, then placed in a tubular furnace and heated to 1300°C at a heating rate of 10°C / min. It is pyrolyzed in this temperature environment for 80 minutes and then naturally cooled to room temperature to obtain an insulating carbon fiber thermal insulation material.

[0083] Comparative Example 3:

[0084] A method for preparing a heat-insulating carbon fiber thermal insulation material specifically includes the following steps:

[0085] The carbon fiber was completely immersed in a nitric acid solution with a mass concentration of 45%, and then placed in a water bath at a temperature of 50°C for 55 minutes for heating and oxidation treatment. After the oxidation treatment, the carbon fiber was removed and the surface nitric acid solution was rinsed with a large amount of distilled water until the pH of the rinse water was neutral. It was then placed in a vacuum drying oven at 70°C and dried to constant weight to obtain surface pretreated carbon fiber;

[0086] 1 part by weight of the tetrapropyl orthosilicate hydrolyzate obtained in Preparation Example 3 and 10 parts by weight of the activated dopamine hydrochloride dispersion obtained in Preparation Example 9 were mixed and stirred to obtain a mixed system, and then a reduced pressure evaporator was used to remove water from the mixed system, and then the mixture was controlled to react at a temperature of 25° C. for 22 hours to obtain an organosilicon-modified levodopa composite liquid; the pH of the organosilicon-modified levodopa composite liquid was adjusted to 9.0 with ammonia water, and then the composite liquid was coated on the surface of the surface pretreated carbon fiber. After the coating was completed, the composite liquid was placed in an ultrasonic power environment of 400 W for 15 minutes, and then allowed to stand for adsorption and crosslinking at room temperature for 30 hours to obtain a modified carbon fiber;

[0087] After the static adsorption is completed, the modified carbon fiber is placed in an oven at 80°C to dry until the surface is hardened, then placed in a tubular furnace and heated to 1300°C at a heating rate of 10°C / min. It is pyrolyzed in this temperature environment for 80 minutes and then naturally cooled to room temperature to obtain an insulating carbon fiber thermal insulation material.

[0088] Comparative Example 4:

[0089] A method for preparing a heat-insulating carbon fiber thermal insulation material specifically includes the following steps:

[0090] A mixture of 1 part by weight of the raw tetrapropyl orthosilicate hydrolysate obtained in Preparation Example 3 and 10 parts by weight of the activated levodopa dispersion obtained in Preparation Example 8 is stirred to obtain a mixed system, and then water in the mixed system is removed by a vacuum evaporator, followed by reaction at a temperature environment of 25°C for 22 hours to obtain a silicone-modified levodopa composite liquid. The pH of the silicone-modified levodopa composite liquid is adjusted to 9.0 with ammonia water, and then it is coated on the surface of the carbon fiber. After the coating is completed, it is placed in an ultrasonic power environment of 400W for 15 minutes, and then it is left to stand and adsorb and crosslink at room temperature for 30 hours to obtain modified carbon fiber.

[0091] After the standing and adsorption is completed, the modified carbon fiber is placed in an oven at 80°C to dry until the surface is hardened, and then it is placed in a tube furnace, heated to 1300°C at a heating rate of 10°C / min, pyrolyzed at this temperature environment for 80 minutes, and then naturally cooled to room temperature to obtain thermal insulation carbon fiber insulation material.

[0092] Comparative Example 5:

[0093] A preparation method of thermal insulation carbon fiber insulation material, specifically comprising the following processes:

[0094] The carbon fiber is completely immersed in a nitric acid solution with a mass concentration of 60%, and then placed in a water bath kettle with a temperature of 60°C for heating and oxidation treatment for 70 minutes. After the oxidation treatment is completed, the carbon fiber is taken out and the surface nitric acid solution is washed with a large amount of distilled water until the pH of the washing water is neutral, and then placed in a vacuum drying oven at 70°C to dry to constant weight to obtain surface pretreated carbon fiber.

[0095] A mixture of 1 part by weight of the raw tetrapropyl orthosilicate hydrolysate obtained in Preparation Example 3 and 10 parts by weight of the activated levodopa dispersion obtained in Preparation Example 8 is stirred to obtain a mixed system, and then water in the mixed system is removed by a vacuum evaporator, followed by reaction at a temperature environment of 25°C for 22 hours to obtain a silicone-modified levodopa composite liquid. The pH of the silicone-modified levodopa composite liquid is adjusted to 9.0 with ammonia water, and then it is coated on the surface of the carbon fiber. After the coating is completed, it is placed in an ultrasonic power environment of 400W for 15 minutes, and then it is left to stand and adsorb and crosslink at room temperature for 30 hours to obtain modified carbon fiber.

[0096] After the standing and adsorption is completed, the modified carbon fiber is placed in an oven at 80°C to dry until the surface is hardened, and then it is placed in a tube furnace, heated to 1300°C at a heating rate of 10°C / min, pyrolyzed at this temperature environment for 80 minutes, and then naturally cooled to room temperature to obtain thermal insulation carbon fiber insulation material.

[0097] Comparative Example 6:

[0098] A preparation method of thermal insulation carbon fiber insulation material, specifically comprising the following processes:

[0099] The carbon fiber was completely immersed in a nitric acid solution with a mass concentration of 45%, and then placed in a water bath at a temperature of 50°C for 55 minutes for heating and oxidation treatment. After the oxidation treatment, the carbon fiber was removed and the surface nitric acid solution was rinsed with a large amount of distilled water until the pH of the rinse water was neutral. It was then placed in a vacuum drying oven at 70°C and dried to constant weight to obtain surface pretreated carbon fiber;

[0100] 11 parts by weight of the tetrapropyl orthosilicate hydrolyzate obtained in Preparation Example 3 was coated on the surface of the surface-pretreated carbon fiber. After coating, the carbon fiber was placed in an ultrasonic power environment of 400 W for 15 minutes, and then allowed to stand at room temperature for 30 hours for adsorption and crosslinking to obtain a modified carbon fiber.

[0101] After the static adsorption is completed, the modified carbon fiber is placed in an oven at 80°C to dry until the surface is hardened, then placed in a tubular furnace and heated to 1300°C at a heating rate of 10°C / min. It is pyrolyzed in this temperature environment for 80 minutes and then naturally cooled to room temperature to obtain an insulating carbon fiber thermal insulation material.

[0102] High temperature antioxidant performance test:

[0103] The heat insulating carbon fiber thermal insulation materials prepared in Examples 1 to 4 and Comparative Examples 1 to 6 were heated to 1000° C. at a heating rate of 5° C. / min, and the initial oxidation temperature was measured by a thermogravimetric analyzer. The results are shown in Table 1 below.

[0104] Table 1 Initial oxidation temperature

[0105]

[0106] The following conclusions can be drawn from the test results in Table 1:

[0107] (1) It can be found from Examples 1 to 4 that the present invention constructs a weakly alkaline organosilicon-modified levodopa composite liquid, which is then coated on the surface of the pretreated carbon fiber to polymerize and adhere to obtain modified carbon fiber, and then subjected to high-temperature treatment to obtain an insulating carbon fiber thermal insulation material having good high-temperature antioxidant properties.

[0108] (2) It can be found from Comparative Example 1 that although tetraethyl orthosilicate can be hydrolyzed to prepare a hydrolysis solution containing silicon hydroxyl groups, the heat-insulating carbon fiber thermal insulation material prepared in the system has poor high-temperature oxidation stability, which may be due to the fact that the ethyl carbon chain in tetraethyl orthosilicate is faster than the propyl carbon chain in tetrapropyl orthosilicate in the system, resulting in a larger viscosity of the tetraethyl orthosilicate hydrolysis solution prepared after crosslinking between silicon hydroxyl groups. Although a larger viscosity is beneficial to adhesion to the surface of the pretreated carbon fiber, the larger viscosity leads to difficulty in uniform infiltration into the surface of the pretreated carbon fiber, thereby resulting in poor high-temperature oxidation stability.

[0109] (3) It can be found from Comparative Example 2 that although tetra-n-butyl orthosilicate can be hydrolyzed to prepare a hydrolysis solution containing silicon hydroxyl groups, the heat-insulating carbon fiber thermal insulation material prepared in the system has poor high-temperature oxidation stability, which may be due to the fact that the butyl carbon chain in tetra-n-butyl orthosilicate is longer than the propyl carbon chain and has a larger steric hindrance, resulting in slower hydrolysis of tetra-n-butyl orthosilicate in the system. Slow hydrolysis leads to poor adhesion of the tetra-n-butyl orthosilicate hydrolysis solution, and the surface of the pretreated carbon fiber in the system is insufficient to achieve good adhesion to the surface of the pretreated carbon fiber. This may lead to a thin and easily detached silica protective layer after high-temperature pyrolysis, thereby resulting in poor high-temperature oxidation stability.

[0110] (4) It can be found from Comparative Example 3 that although dopamine hydrochloride also has an oxidative self-polymerization to generate a polydopamine structure with adhesion, the heat-insulating carbon fiber thermal insulation material prepared in the system has poor high-temperature oxidation stability, which may be due to the fact that dopamine hydrochloride does not have a functional group carboxyl group, making it difficult for the tetrapropyl orthosilicate hydrolysis solution containing silicon hydroxyl groups to effectively bind to dopamine hydrochloride through covalent esterification condensation between the carboxyl group and the silicon hydroxyl group. This makes it difficult for the prepared organic silicon modified levodopa composite solution to effectively load organic silicon, and further leads to a thin silica protective layer after high-temperature pyrolysis of the polydopamine structure, resulting in poor high-temperature oxidation stability of the prepared heat-insulating carbon fiber thermal insulation material.

[0111] (5) It can be found from Comparative Example 4 that the heat-insulating carbon fiber thermal insulation material prepared in the system has poor high-temperature oxidation stability, which may be due to the fact that the main component of carbon fiber is carbon atom, and the graphite-like structure formed has high chemical stability and low surface energy. This leads to low reactivity of carbon fiber in many environments, making it difficult to effectively adhere to the organic silicon modified levodopa composite solution, and further leading to poor high-temperature oxidation stability of the final prepared heat-insulating carbon fiber thermal insulation material.

[0112] (6) Comparative Example 5 shows that the thermal insulation carbon fiber thermal insulation material prepared in this system has poor high-temperature oxidation stability. This may be because, although the nitric acid oxidation treatment can increase the oxygen-containing active groups on the carbon fiber surface, the increase in oxygen-containing active groups facilitates further contact reaction with the coating liquid and improves the adhesion effect. However, excessively high nitric acid concentration and excessively long oxidation treatment may cause the carbon fiber matrix structure to be damaged, which in turn makes the thermal insulation carbon fiber thermal insulation material have poor high-temperature oxidation stability.

[0113] (7) It can be found from Comparative Example 6 that although the tetrapropyl orthosilicate hydrolyzate can produce adhesion through cross-linking condensation between silanol groups, it is not enough to achieve good adhesion to the surface pretreated carbon fiber in the formulation of this system, resulting in the silica protective layer after high-temperature pyrolysis easily falling off, making it difficult to achieve high-temperature oxidation protection for the carbon fiber.

[0114] The embodiments described above provide a detailed description of the technical solutions and beneficial effects of the present invention. It should be understood that the above descriptions are merely specific embodiments of the present invention and are not intended to limit the present invention. Various changes and modifications may be made to the present invention without departing from the spirit and scope of the present invention, and such changes and modifications fall within the scope of the present invention as claimed.

Claims

1. A method for preparing a heat-insulating carbon fiber thermal insulation material, characterized in that: The preparation method comprises the following steps: The carbon fibers are immersed in a nitric acid solution for oxidation treatment to obtain surface pretreated carbon fibers; The tetrapropyl orthosilicate hydrolyzate and the activated levodopa dispersion are mixed and evaporated under reduced pressure to remove the solvent water, followed by a reaction at a temperature of 20°C to 25°C for 18 hours to 22 hours to obtain an organosilicon-modified levodopa composite solution; The organosilicon-modified levodopa composite solution is adjusted to a pH of 8.0-9.0, and then coated on the surface of the surface-pretreated carbon fiber and subjected to an ultrasonic treatment at a power of 300W-400W for 10-15 minutes, followed by standing for adsorption and crosslinking for 20-30 hours to obtain the modified carbon fiber; The modified carbon fiber is pyrolyzed at high temperature to obtain the heat-insulating carbon fiber thermal insulation material; The preparation method of the activated levodopa dispersion comprises the following steps: Levodopa and a carboxyl activator are dispersed in anhydrous dichloromethane and placed in a 0°C environment for pre-activation treatment for 15 minutes to 20 minutes to obtain the activated levodopa dispersion; The molar ratio of levodopa to the carboxyl activator is 1:1.5-2.

2. The method for preparing a heat-insulating carbon fiber thermal insulation material according to claim 1, characterized in that: The mass concentration of the nitric acid solution is 40% to 45%.

3. The method for preparing a heat-insulating carbon fiber thermal insulation material according to claim 1, characterized in that: The conditions of the immersion oxidation treatment include a treatment temperature of 40° C. to 50° C. and a treatment time of 50 min to 55 min.

4. The method for preparing a heat-insulating carbon fiber thermal insulation material according to claim 1, characterized in that: The preparation method of the tetrapropyl orthosilicate hydrolyzate comprises the following steps: After tetrapropyl orthosilicate is dispersed in deionized water, acid is added to adjust the pH to 2.5-3.0, and then the temperature is raised to 50° C.-60° C. and reacted for 2 h-3 h to obtain the tetrapropyl orthosilicate hydrolyzate.

5. The method for preparing a heat-insulating carbon fiber thermal insulation material according to claim 1, characterized in that: The weight ratio of the tetrapropyl orthosilicate hydrolyzate to the activated levodopa dispersion is 1:5-10.

6. The method for preparing a heat-insulating carbon fiber thermal insulation material according to claim 1, characterized in that: The high-temperature pyrolysis conditions include a pyrolysis temperature of 1100° C. to 1300° C. and a pyrolysis time of 60 min to 80 min.

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