High-toughness epoxy-based buoyancy composite and method of making same

Abstract

This invention discloses a high-toughness epoxy-based buoyancy composite material and its preparation method, belonging to the field of buoyancy material technology. The composite material comprises the following raw materials in parts by weight: 80-100 parts epoxy resin, 60-70 parts curing agent, 30-50 parts modified hollow glass microspheres, 10-15 parts reactive diluent, 4-7 parts toughening agent, 0.5-1 part dispersant, and 0.4-0.8 parts defoamer. This invention modifies the surface of the hollow glass microspheres by grafting decyl long chains and C-F bonds onto their surface. The decyl long chains have good compatibility with the epoxy resin matrix, improving interfacial bonding strength and absorbing impact energy, thus enhancing the material's toughness. The C-F bonds impart strong hydrophobicity to the material, inhibiting the adsorption and diffusion of water molecules at the interface, thereby improving water resistance. The epoxy-based buoyancy composite material prepared by this invention possesses low density, high toughness, excellent interfacial bonding performance, and water resistance, making it suitable for long-term service in harsh environments such as deep-sea high pressure and strong corrosion.

Description

Technical Field

[0001] This invention belongs to the field of buoyancy material technology, specifically, it relates to a high-toughness epoxy-based buoyancy composite material and its preparation method. Background Technology

[0002] With the rapid development of marine resource development, deep-sea exploration, and water transportation, the demand for lightweight, high-strength materials capable of long-term stable operation in high-pressure, highly corrosive marine environments is becoming increasingly urgent. Buoyancy materials, as a key component of underwater vehicles, deep-sea submersibles, buoy systems, and offshore oil drilling platforms, directly determine the load-bearing capacity, safety, and service life of these devices. Traditional buoyancy materials are mainly chemically foamed materials such as expanded polyurethane and expanded polystyrene. While these materials possess certain low-density characteristics, they suffer from drawbacks such as low compressive strength, high water absorption, easy compression deformation under high pressure in the deep sea, and poor resistance to seawater corrosion. They can only meet basic applications in shallow sea areas and cannot adapt to the complex service environments of high pressure, high salinity, and high humidity in kilometer-deep and deeper waters, gradually failing to meet the technological upgrading requirements of modern marine engineering and deep-sea exploration.

[0003] Against this backdrop, epoxy resin has become a mainstream research and development direction for deep-sea buoyancy materials due to its excellent mechanical properties, low curing shrinkage, good chemical corrosion resistance, and compatibility with various fillers. However, pure epoxy resin is brittle and has a relatively high density after curing, making it difficult to meet the requirements for lightweight buoyancy materials when used directly as a matrix. Hollow glass microspheres, as a hollow inorganic filler, have the characteristics of low density, high compressive strength, controllable particle size, and good chemical stability. Introducing them into the epoxy resin matrix can significantly reduce the overall density of the composite material, while their rigid spherical structure can improve the compressive strength of the material to a certain extent.

[0004] However, existing publicly available technologies for buoyancy materials based on epoxy resin and hollow glass microspheres still face technical bottlenecks. First, buoyancy materials may be subjected to unexpected impacts during manufacturing, transportation, assembly, and service, such as hoisting collisions, scraping from seabed rocks, or impacts from debris. Traditional epoxy-based materials, due to their high cross-linking density, often exhibit brittle characteristics and are prone to cracking or even complete fragmentation under impact loads. Second, the interfacial compatibility between hollow glass microspheres and the epoxy resin matrix is ​​poor. Without effective surface treatment, the microspheres and resin are prone to interfacial debonding during curing, forming microscopic defects. Under external loads, cracks easily propagate along the interface, leading to a decline in the overall mechanical properties of the material. Finally, in long-term service in deep-water environments, water molecules not only diffuse into the material through the free volume of the resin matrix but may also penetrate along the microsphere-resin interface, causing interfacial debonding, plasticization, or even hydrolysis. In summary, it is urgent to solve these problems to meet the higher technical requirements of the buoyancy material technology field. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of the prior art and provide a high-toughness epoxy buoyancy composite material and its preparation method.

[0006] The objective of this invention can be achieved through the following technical solutions: A high-toughness epoxy-based buoyancy composite material comprises the following raw materials in parts by weight: 80-100 parts epoxy resin, 60-70 parts curing agent, 30-50 parts modified hollow glass microspheres, 10-15 parts reactive diluent, 4-7 parts toughening agent, 0.5-1 part dispersant, and 0.4-0.8 parts defoamer.

[0007] As a further technical solution, the epoxy resin is obtained by compounding bisphenol A type epoxy resin and bisphenol F type epoxy resin, with a mass ratio of 7:3.

[0008] As a further technical solution, the active diluent is butyl glycidyl ether or 1,4-butanediol diglycidyl ether.

[0009] As a further technical solution, the toughening agent is carboxyl-terminated butadiene-acrylonitrile rubber.

[0010] As a further technical solution, the modified hollow glass microspheres are prepared through the following steps: S1. In a three-necked flask, melamine and N,N-dimethylformamide were added sequentially, nitrogen gas was introduced for protection, and the mixture was heated to 50-60°C. The mixture was stirred until most of the product was dissolved, and then the temperature was further increased to 80-90°C. Decanoic acid, 4-dimethylaminopyridine and dicyclohexylcarbodiimide were added sequentially. After the addition was complete, the mixture was stirred for 12-16 hours until the reaction was complete. After post-treatment, product 1 was obtained. S2. In a three-necked flask, product 1 and N,N-dimethylformamide were added sequentially. Nitrogen gas was introduced for protection, and the mixture was heated to 50-60°C. After stirring until homogeneous, the apparatus was placed in an ice-water bath (0-5°C). Perfluorobutyric acid and 1-hydroxybenzotriazole were added, and the mixture was stirred for 5-10 minutes. Then, N,N-diisopropylethylamine was added to adjust the system to a weakly alkaline state (pH=8-9). Finally, EDC·HCl (1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride) was added. After the addition was complete, the ice bath was removed, and the mixture was slowly raised to room temperature. The reaction was continued to be stirred for 12-24 hours. After the reaction was completed, product 2 was obtained after post-treatment. S3. In a three-necked flask, add product 2, N,N-dimethylformamide and potassium carbonate in sequence. After stirring evenly, place the apparatus in an ice-water bath (0-5℃), and then slowly add cyanuric chloride. After the addition is complete, continue stirring for 2-4 hours. After the reaction is complete, product 3 is obtained after post-processing. S4. Add the silane-modified hollow glass microspheres to a three-necked flask, dry them under vacuum at 80°C for 2 hours, then purge with nitrogen for protection, add N,N-dimethylformamide, and ultrasonically disperse them evenly. Add product 3 and N,N-diisopropylethylamine to the flask, and heat to 60-80°C with stirring. Keep the temperature and stir for 12-24 hours to obtain the modified hollow glass microspheres.

[0011] Further, in step S1, the ratio of melamine, decanoic acid, 4-dimethylaminopyridine and dicyclohexylcarbodiimide is 15.1-17.3g:17.2g:1.2g:20.6g.

[0012] Further, in step S2, the ratio of product 1, perfluorobutyric acid, 1-hydroxybenzotriazole and EDC·HCl is 30.5-33.9g:21.4g:1.4g:19.1g.

[0013] Furthermore, in step S3, the ratio of product 2, potassium carbonate, and cyanuric chloride is 95.2g:27.6g:20.5-22.7g.

[0014] Furthermore, in step S4, the ratio of the amount of silane-modified hollow glass microspheres, product 3, and N,N-diisopropylethylamine is 50g:7.5-9.2g:3.2g.

[0015] In the process of preparing modified hollow glass microspheres according to the present invention, the reaction formulas for steps S1, S2, and S3 are as follows: This invention prepares modified hollow glass microspheres through a four-step reaction. To ensure the smooth progress of the reaction, the amount of reactants in steps S1-S3 needs to be strictly controlled. Specifically, in step S1, the molar ratio of melamine to decanoic acid should be close to 1:1, with melamine in excess, and two amino groups reserved for subsequent reactions. In step S2, the molar ratio of product 1 to perfluorobutyric acid should be close to 1:1, with product 1 in excess, and one amino group reserved for reaction S3. Finally, in step S3, the molar ratio of product 2 to cyanuric chloride should be close to 2:1, with cyanuric chloride in excess, and one chlorine group reserved for reaction S4.

[0016] This invention modifies the surface of hollow glass microspheres by grafting decyl long chains and CF bonds onto their surface. The decyl long chains, similar in structure to the alkyl framework of epoxy resin, significantly reduce interfacial energy and improve the resin's wettability of the microspheres. Furthermore, the decyl long chains exhibit good flexibility, absorbing impact energy and preventing stress concentration at rigid interfaces, thereby enhancing the toughness of the matrix. The introduced CF bonds, with their strong hydrophobicity, significantly inhibit the adsorption and diffusion of water molecules at the interface. Simultaneously, the dense arrangement of fluorine segments forms a physical barrier, hindering water molecule penetration and significantly improving the water resistance of the matrix. Finally, by grafting organic chains onto the hollow glass microspheres, the migration and exudation resistance of the organic chains are significantly improved, thereby enhancing the overall performance stability.

[0017] As a further technical solution, the silane-modified hollow glass microspheres are prepared through the following steps: Hollow glass microspheres were placed in a high-speed mixer, preheated to 80-100℃ and stirred. Then, silane coupling agent KH-550 was added to an ethanol aqueous solution and the pH was adjusted to 4-5 with acetic acid. After stirring evenly, the mixture was sprayed evenly onto the surface of the microspheres stirred at high speed. After stirring for 15-20 minutes, the mixture was transferred to a vacuum drying oven for drying to remove solvent and moisture, thus obtaining silane-modified hollow glass microspheres.

[0018] As a further technical solution, the amount of the silane coupling agent KH-550 is 1.2-1.5% of the mass of the hollow glass microspheres.

[0019] As a further technical solution, the mass ratio of ethanol to water in the ethanol-water solution is 9:1.

[0020] As a further technical solution, the drying temperature is 100-105℃ and the time is 2-3 hours.

[0021] This invention also provides a method for preparing a high-toughness epoxy-based buoyancy composite material, comprising the following steps: Step 1: Add epoxy resin, reactive diluent, toughening agent, dispersant and defoamer to the reaction vessel in sequence, stir evenly, then add curing agent, stir at high speed under vacuum for 10-15 minutes to degas, and obtain resin mixture. Step 2: Add the modified hollow glass microspheres to the resin mixture in three batches, and then stir at low speed in a vacuum mixer for 10-20 minutes to allow the resin to fully coat the microspheres. Then let it stand under vacuum for 10-15 minutes. After observing that no bubbles escape, the mixed slurry is obtained. Step 3: Slowly pour the mixed slurry into the preheated mold, maintaining a vacuum during the pouring process. Place the poured mold into an oven for heating and curing. After curing, allow it to cool naturally to room temperature and demold to obtain a high-toughness epoxy buoyancy composite material.

[0022] As a further technical solution, the high-speed stirring speed is 1200-1500 rpm.

[0023] As a further technical solution, the rotation speed of the low-speed stirring is 300-400 rpm.

[0024] As a further technical solution, the temperature of the preheating mold is 50-55℃.

[0025] As a further technical solution, the heating curing procedure is as follows: curing at 60-65℃ for 4 hours, then curing at 90-95℃ for 6 hours, and finally curing at 120-130℃ for 2 hours.

[0026] The beneficial effects of this invention are: 1. This invention introduces a carboxyl-terminated butadiene-acrylonitrile rubber toughening agent into epoxy resin and grafts a flexible decyl long chain onto the surface of hollow glass microspheres, which effectively absorbs impact energy, avoids stress concentration, and significantly improves the impact resistance and overall toughness of the material. 2. The decyl long chains grafted onto the surface of the modified hollow glass microspheres have good compatibility with the epoxy resin matrix, which reduces the interfacial energy, improves the wettability of the resin to the microspheres, reduces micro-defects, and enhances the interfacial bonding strength. 3. The introduction of fluorine segments containing CF bonds on the surface of microspheres effectively inhibits the adsorption and diffusion of water molecules at the interface, significantly improving the water resistance of the composite material. 4. Organic chains are firmly grafted onto the surface of hollow glass microspheres through chemical bonds, which enhances the migration resistance and exudation resistance of the organic chains and ensures the stability of the material's performance during long-term service. 5. The use of bisphenol A and bisphenol F epoxy resins ensures mechanical strength while reducing system viscosity, which is beneficial for the uniform dispersion of hollow glass microspheres and achieves synergistic optimization of low density and high strength. In summary, this invention effectively solves the problems of poor toughness, poor interfacial compatibility, and insufficient water resistance of existing epoxy-based buoyancy materials, and is suitable for long-term service in harsh environments such as deep-sea high pressure and strong corrosion. Detailed Implementation

[0027] The technical solutions in the embodiments of the present invention will be clearly and completely described below. 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.

[0028] Example 1 Preparation of silane-modified hollow glass microspheres: Fifty parts of hollow glass microspheres (particle size 20-50 μm) were placed in a high-speed mixer, preheated to 80°C and stirred. Then, 0.6 parts of silane coupling agent KH-550 were added to 100 parts of ethanol aqueous solution (ethanol to water mass ratio of 9:1), and the pH was adjusted to 4 with acetic acid. After stirring evenly, the mixture was sprayed evenly onto the surface of the microspheres stirred at high speed. After stirring for 15 min, the mixture was transferred to a vacuum drying oven and dried at 100°C for 2 h to obtain silane-modified hollow glass microspheres.

[0029] Preparation of modified hollow glass microspheres: S1. In a three-necked flask, 30.2 g of melamine and 200 mL of N,N-dimethylformamide were added sequentially. Nitrogen gas was introduced for protection, and the mixture was heated to 50 °C. The mixture was stirred until most of the melamine was dissolved, and then the mixture was heated to 80 °C. Then, 34.4 g of decanoic acid, 2.4 g of 4-dimethylaminopyridine, and 41.2 g of dicyclohexylcarbodiimide were added sequentially. After the addition was complete, the mixture was stirred for 12 h. The reaction was completed, and after post-treatment, product 1 was obtained. S2. In a three-necked flask, 61.0 g of product 1 and N,N-dimethylformamide were added sequentially. Nitrogen gas was introduced for protection, and the mixture was heated to 50°C. After stirring until homogeneous, the apparatus was placed in an ice-water bath (0°C). 42.8 g of perfluorobutyric acid and 2.8 g of 1-hydroxybenzotriazole were added. After stirring for 5 min, N,N-diisopropylethylamine was added, and the pH of the system was adjusted to 8. Finally, 38.2 g of EDC·HCl was added. After the addition was complete, the ice bath was removed, and the mixture was slowly raised to room temperature. The reaction was continued to be stirred for 12 h. After the reaction was completed, product 2 was obtained after post-treatment. S3. In a three-necked flask, add 95.2g of product 2, N,N-dimethylformamide and 27.6g of potassium carbonate in sequence. After stirring evenly, place the apparatus in an ice-water bath (0℃) and slowly add 20.5g of cyanuric chloride. After the addition is complete, continue stirring and react for 2 hours. After the reaction is complete, product 3 is obtained after post-processing. S4. Add 50g of silane-modified hollow glass microspheres to a three-necked flask, dry under vacuum at 80℃ for 2h, then purge with nitrogen for protection, add N,N-dimethylformamide, and ultrasonically disperse until uniform. Add 7.5g of product 3 and 3.2g of N,N-diisopropylethylamine to the flask, heat to 60℃ with stirring, and maintain the temperature and stir for 12h. After the reaction is complete, cool to room temperature, centrifuge, and wash successively with N,N-dimethylformamide, ethanol, and deionized water. After drying, the modified hollow glass microspheres are obtained.

[0030] A method for preparing a high-toughness epoxy-based buoyancy composite material includes the following steps: Step 1: Add 80 parts of epoxy resin (a mixture of bisphenol A type epoxy resin and bisphenol F type epoxy resin in a mass ratio of 7:3), 10 parts of butyl glycidyl ether, 4 parts of carboxyl-terminated nitrile rubber, 0.5 parts of dispersant (BYK-W969), and 0.4 parts of defoamer (BYK-A530) to the reactor in sequence. After stirring evenly, add 60 parts of polyetheramine (D230) and stir at high speed (1200 rpm) under vacuum for 10 minutes to remove bubbles and obtain a resin mixture. Step 2: Add 30 portions of modified hollow glass microspheres to the resin mixture in three batches, and then stir at low speed (300 rpm) for 10 minutes in a vacuum mixer to ensure that the resin fully coats the microspheres. Then let it stand under vacuum for 10 minutes. After observing that no bubbles escape, the mixed slurry is obtained. Step 3: Slowly pour the mixed slurry into the preheated mold (temperature 50℃), maintaining a vacuum during the pouring process. Place the poured mold into an oven and heat it to cure (the curing procedure is as follows: cure at 60℃ for 4 hours, then at 90℃ for 6 hours, and finally at 120℃ for 2 hours). After curing, allow it to cool naturally to room temperature, demold, and obtain a high-toughness epoxy buoyancy composite material.

[0031] Example 2 Preparation of silane-modified hollow glass microspheres: Fifty parts of hollow glass microspheres (particle size 20-50 μm) were placed in a high-speed mixer, preheated to 100℃ and stirred. Then, 0.75 parts of silane coupling agent KH-550 were added to 100 parts of ethanol aqueous solution (ethanol to water mass ratio of 9:1), and the pH was adjusted to 5 with acetic acid. After stirring evenly, the mixture was sprayed evenly onto the surface of the microspheres stirred at high speed. After stirring for another 20 min, the mixture was transferred to a vacuum drying oven and dried at 105℃ for 3 h to obtain silane-modified hollow glass microspheres.

[0032] Preparation of modified hollow glass microspheres: S1. In a three-necked flask, 34.6 g of melamine and 200 mL of N,N-dimethylformamide were added sequentially. Nitrogen gas was introduced for protection, and the mixture was heated to 60 °C. The mixture was stirred until most of the melamine was dissolved, and then the mixture was heated to 90 °C. Then, 34.4 g of decanoic acid, 2.4 g of 4-dimethylaminopyridine, and 41.2 g of dicyclohexylcarbodiimide were added sequentially. After the addition was complete, the mixture was stirred for 16 h. The reaction was completed, and after post-treatment, product 1 was obtained. S2. In a three-necked flask, 67.8 g of product 1 and N,N-dimethylformamide were added sequentially. Nitrogen gas was introduced for protection, and the mixture was heated to 60°C. After stirring until homogeneous, the apparatus was placed in an ice-water bath (5°C). 42.8 g of perfluorobutyric acid and 2.8 g of 1-hydroxybenzotriazole were added. After stirring for 10 min, N,N-diisopropylethylamine was added, and the pH of the system was adjusted to 9. Finally, 38.2 g of EDC·HCl was added. After the addition was complete, the ice bath was removed, and the mixture was slowly raised to room temperature. The reaction was continued to be stirred for 24 h. After the reaction was completed, product 2 was obtained after post-treatment. S3. In a three-necked flask, add 95.2g of product 2, N,N-dimethylformamide and 27.6g of potassium carbonate in sequence. After stirring evenly, place the apparatus in an ice-water bath (5℃) and slowly add 22.7g of cyanuric chloride. After the addition is complete, continue stirring for 4 hours. After the reaction is complete, product 3 is obtained after post-processing. S4. Add 50g of silane-modified hollow glass microspheres to a three-necked flask, dry under vacuum at 80℃ for 2h, then purge with nitrogen for protection, add N,N-dimethylformamide, and ultrasonically disperse until uniform. Add 9.2g of product 3 and 3.2g of N,N-diisopropylethylamine to the flask, heat to 80℃ with stirring, and maintain the temperature and stir for 24h. After the reaction is complete, cool to room temperature, centrifuge, and wash successively with N,N-dimethylformamide, ethanol, and deionized water. After drying, the modified hollow glass microspheres are obtained.

[0033] A method for preparing a high-toughness epoxy-based buoyancy composite material includes the following steps: Step 1: In a reaction vessel, add 90 parts of epoxy resin (a mixture of bisphenol A type epoxy resin and bisphenol F type epoxy resin in a mass ratio of 7:3), 12.5 parts of 1,4-butanediol diglycidyl ether, 5.5 parts of carboxyl-terminated nitrile rubber, 0.75 parts of dispersant (BYK-W969), and 0.6 parts of defoamer (BYK-A530). After stirring evenly, add 65 parts of polyetheramine (D230). Stir at high speed (1500 rpm) under vacuum for 15 minutes to remove bubbles and obtain a resin mixture. Step 2: Add 40 portions of modified hollow glass microspheres to the resin mixture in three batches, and then stir at low speed (400 rpm) for 20 minutes in a vacuum mixer to ensure that the resin fully coats the microspheres. Then let it stand under vacuum for 15 minutes. After observing that no bubbles escape, the mixed slurry is obtained. Step 3: Slowly pour the mixed slurry into the preheated mold (temperature 55℃), maintaining a vacuum during the pouring process. Place the poured mold into an oven and heat to cure (the curing procedure is as follows: cure at 65℃ for 4 hours, then at 95℃ for 6 hours, and finally at 130℃ for 2 hours). After curing, allow it to cool naturally to room temperature, demold, and obtain a high-toughness epoxy buoyancy composite material.

[0034] Example 3 The only difference between this embodiment and Embodiment 2 is that, in this embodiment, a method for preparing a high-toughness epoxy-based buoyancy composite material includes the following steps: Step 1: Add 100 parts of epoxy resin (a mixture of bisphenol A type epoxy resin and bisphenol F type epoxy resin in a mass ratio of 7:3), 15 parts of 1,4-butanediol diglycidyl ether, 7 parts of carboxyl-terminated nitrile rubber, 1 part of dispersant (BYK-W969), and 0.8 parts of defoamer (BYK-A530) to the reactor in sequence. After stirring evenly, add 70 parts of polyetheramine (D230) and stir at high speed (1500 rpm) under vacuum for 15 minutes to degas, thus obtaining a resin mixture. Step 2: Add 50 portions of modified hollow glass microspheres to the resin mixture in three batches, and then stir at low speed (400 rpm) for 20 minutes in a vacuum mixer to ensure that the resin fully coats the microspheres. Then let it stand under vacuum for 15 minutes. After observing that no bubbles escape, the mixed slurry is obtained. Step 3: Slowly pour the mixed slurry into the preheated mold (temperature 55℃), maintaining a vacuum during the pouring process. Place the poured mold into an oven and heat to cure (the curing procedure is as follows: cure at 65℃ for 4 hours, then at 95℃ for 6 hours, and finally at 130℃ for 2 hours). After curing, allow it to cool naturally to room temperature, demold, and obtain a high-toughness epoxy buoyancy composite material.

[0035] Comparative Example 1 The only difference between this comparative example and Example 3 is that in this comparative example, the hollow glass microspheres are not modified; ordinary hollow glass microspheres are used instead of modified hollow glass microspheres to obtain the composite material.

[0036] Comparative Example 2 The only difference between this comparative example and Comparative Example 1 is that, in this comparative example, the modified hollow glass microspheres were replaced with hollow glass microspheres that were only surface-treated with silane coupling agent KH-550 (without S1-S4 organic chain modification) to obtain the composite material.

[0037] The following performance tests were conducted on Examples 1, 2, and 3, and Comparative Examples 1 and 2: The impact strength of the specimens was determined according to GB / T 1043 standard; The water absorption rate of the samples was determined according to GB / T 1034 standard. The measurement results are shown in Table 1: Table 1 As shown in Table 1, the composite material prepared in the embodiments of the present invention exhibits higher toughness and water resistance than the comparative example. Therefore, the present invention is suitable for long-term service requirements in harsh environments such as deep-sea high pressure and strong corrosion.

[0038] 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 high-toughness epoxy-based buoyancy composite material, characterized in that, The raw materials include the following parts by weight: 80-100 parts epoxy resin, 60-70 parts curing agent, 30-50 parts modified hollow glass microspheres, 10-15 parts reactive diluent, 4-7 parts toughening agent, 0.5-1 part dispersant, and 0.4-0.8 parts defoamer.

2. The high-toughness epoxy-based buoyancy composite material according to claim 1, characterized in that, The epoxy resin is a compound of bisphenol A type epoxy resin and bisphenol F type epoxy resin, with a mass ratio of 7:

3.

3. The high-toughness epoxy-based buoyancy composite material according to claim 1, characterized in that, The modified hollow glass microspheres are prepared by the following steps: S1. In a flask, melamine and N,N-dimethylformamide are added in sequence, nitrogen gas is introduced, and the mixture is heated to 50-60°C. After stirring, the mixture is heated to 80-90°C, and then decanoic acid, 4-dimethylaminopyridine and dicyclohexylcarbodiimide are added. After the addition is complete, the mixture is stirred and reacted for 12-16 hours. The reaction is complete, and product 1 is obtained. S2. In a flask, add product 1 and N,N-dimethylformamide in sequence, purge with nitrogen, heat to 50-60℃, stir until homogeneous, place in an ice-water bath, add perfluorobutyric acid and 1-hydroxybenzotriazole, stir for 5-10 min, then add N,N-diisopropylethylamine, adjust the pH of the system to 8-9, and finally add EDC·HCl. After the addition is complete, remove the ice bath and stir the reaction at room temperature for 12-24 h. The reaction is complete, and product 2 is obtained. S3. In a flask, add product 2, N,N-dimethylformamide and potassium carbonate in sequence, stir well, place in an ice-water bath, and then slowly add cyanuric chloride. After the addition is complete, stir the reaction for 2-4 hours. The reaction is complete, and product 3 is obtained. S4. Add the silane-modified hollow glass microspheres to a flask, dry them under vacuum at 80°C for 2 hours, then introduce nitrogen gas, add N,N-dimethylformamide, and disperse by ultrasonication. Add product 3 and N,N-diisopropylethylamine to the flask, heat to 60-80°C and react for 12-24 hours to obtain the modified hollow glass microspheres.

4. The high-toughness epoxy-based buoyancy composite material according to claim 3, characterized in that, In step S1, the ratio of melamine, decanoic acid, 4-dimethylaminopyridine and dicyclohexylcarbodiimide is 15.1-17.3g:17.2g:1.2g:20.6g.

5. The high-toughness epoxy-based buoyancy composite material according to claim 3, characterized in that, In step S2, the ratio of product 1, perfluorobutyric acid, 1-hydroxybenzotriazole and EDC·HCl is 30.5-33.9g:21.4g:1.4g:19.1g.

6. The high-toughness epoxy-based buoyancy composite material according to claim 3, characterized in that, In step S3, the ratio of product 2, potassium carbonate, and cyanuric chloride is 95.2g:27.6g:20.5-22.7g.

7. The high-toughness epoxy-based buoyancy composite material according to claim 3, characterized in that, In step S4, the ratio of silane-modified hollow glass microspheres, product 3, and N,N-diisopropylethylamine is 50g:7.5-9.2g:3.2g.

8. A method for preparing a high-toughness epoxy-based buoyancy composite material, used to prepare the high-toughness epoxy-based buoyancy composite material according to any one of claims 1-7, characterized in that, Includes the following steps: Step 1: Add epoxy resin, reactive diluent, toughening agent, dispersant and defoamer to the reaction vessel in sequence, stir evenly, then add curing agent, stir at high speed under vacuum for 10-15 minutes to degas, and obtain resin mixture. Step 2: Add the modified hollow glass microspheres to the resin mixture, stir at low speed for 10-20 minutes, and then let it stand under vacuum for 10-15 minutes to obtain the mixed slurry. Step 3: Pour the mixed slurry into a preheated mold, maintaining a vacuum during the pouring process. After the mold is heated and cured, it is cooled and demolded to obtain a high-toughness epoxy buoyancy composite material.

9. The method for preparing a high-toughness epoxy-based buoyancy composite material according to claim 8, characterized in that, The temperature of the preheated mold is 50-55℃.

10. The method for preparing a high-toughness epoxy-based buoyancy composite material according to claim 8, characterized in that, The heating and curing process is as follows: cure at 60-65℃ for 4 hours, then cure at 90-95℃ for 6 hours, and finally cure at 120-130℃ for 2 hours.

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