A tung oil modified epoxy resin and a preparation method thereof

Abstract

The application discloses a tung oil modified epoxy resin and a preparation method thereof, and relates to the technical field of high polymer materials. In the preparation of the tung oil modified epoxy resin, tung oil is oxidized by a hydrogen peroxide solution to obtain a tung oil active diluent; nano-silicon dioxide and gamma-methacryloxypropyl trimethoxysilane are reacted to obtain modified nano-silicon dioxide; the tung oil is sequentially reacted with maleic anhydride, triethylenetetramine and DOPO to obtain a tung oil curing agent; the epoxy resin, the modified nano-silicon dioxide and the tung oil active diluent are uniformly mixed, the tung oil curing agent is added, ultrasonic dispersion is carried out at room temperature, and then the mixture is placed in a mold for curing and forming, and the tung oil modified epoxy resin is obtained by opening the mold and taking out the product. The tung oil modified epoxy resin prepared by the application has excellent mechanical properties and flame retardant properties, and is green and environment-friendly.

Description

Technical Field

[0001] This invention relates to the field of polymer materials technology, specifically to a tung oil-modified epoxy resin and its preparation method. Background Technology

[0002] Epoxy resin, as an important matrix for the development of composite materials, plays a vital supporting role in advanced chemical manufacturing. However, with the concepts of sustainable development and green environmental protection, petroleum-based materials are gradually shifting towards bio-based materials.

[0003] Vegetable oils are a low-cost biomass resource widely used in the synthesis of various bio-based materials. Tung oil, as a non-edible vegetable oil, is chemically reactive and possesses derivatization potential. Therefore, using tung oil to modify epoxy resins to improve their performance aligns with the concept of green and environmentally friendly development and has significant market value. Summary of the Invention

[0004] The purpose of this invention is to provide a tung oil-modified epoxy resin and its preparation method, so as to solve the problems existing in the prior art.

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

[0006] A tung oil-modified epoxy resin comprises the following components by weight: 100 parts epoxy resin, 10-15 parts tung oil reactive diluent, 4-6 parts modified nano silica, and 160-180 parts tung oil curing agent.

[0007] As an optimization, the tung oil active diluent is prepared by oxidizing tung oil with hydrogen peroxide solution.

[0008] As an optimization, the modified nano-silica is prepared by reacting nano-silica with γ-methacryloxypropyltrimethoxysilane.

[0009] As an optimization, the tung oil curing agent is prepared by reacting tung oil with maleic anhydride, triethylenetetramine, and DOPO in sequence.

[0010] A method for preparing tung oil-modified epoxy resin includes the following preparation steps:

[0011] (1) In a nitrogen atmosphere, maleic anhydride and tung oil are mixed evenly at a mass ratio of 1:4. The mixture is stirred and refluxed at 100-200 r / min for 2-3 hours at 120-125℃. Then, triethylenetetramine with a mass of 2-2.2 times that of maleic anhydride is added, and the mixture is stirred and reacted for 3-4 hours. Finally, DOPO with a mass of 0.8-1.0 times that of maleic anhydride is added, and the mixture is heated to 160-170℃ and stirred and reacted for 6-8 hours to obtain tung oil curing agent.

[0012] (2) Heat tung oil and maintain it at 55-60°C. Under stirring conditions of 100-200 r / min, add acetic acid, hydrogen peroxide solution and phosphoric acid solution at a uniform rate within 2 hours. After the addition is completed, continue stirring and react for 5-6 hours. Cool to room temperature and adjust the pH to neutral with 20% sodium carbonate solution. Let it stand to separate the layers and remove the aqueous phase. Then wash with pure water 3-5 times and let it stand to separate the layers to remove the aqueous phase. Then dry at 90-95°C for 3-4 hours to obtain tung oil active diluent.

[0013] (3) Weigh 100 parts of epoxy resin, 10-15 parts of tung oil active diluent, 4-6 parts of modified nano silica, and 160-180 parts of tung oil curing agent according to the mass fractions; mix the epoxy resin, modified nano silica, and tung oil active diluent evenly, then add the tung oil curing agent, ultrasonically disperse at room temperature for 10-12 minutes, place in a mold, stand at 60-70℃ for 6-8 hours, and after naturally cooling to room temperature, open the mold and take out the product to obtain tung oil modified epoxy resin.

[0014] As an optimization, the hydrogen peroxide solution in step (2) is a 30% hydrogen peroxide solution; the phosphoric acid solution is a 60% phosphoric acid solution; the relative quantities of tung oil, acetic acid, hydrogen peroxide solution and phosphoric acid solution are as follows, by mass fraction: 25-30 parts of tung oil, 22-25 parts of acetic acid, 55-65 parts of 30% hydrogen peroxide solution and 2-3 parts of 60% phosphoric acid solution.

[0015] As an optimization, the preparation method of the modified nano silica in step (3) is as follows: nano silica, γ-methacryloxypropyltrimethoxysilane and anhydrous ethanol are mixed evenly in a mass ratio of 1:1:10-12, ultrasonicated at room temperature for 8-10 min, and pure water with a mass of 1-2 times that of nano silica is added. The mixture is then ultrasonicated for 30-40 min, centrifuged and washed with pure water 3-5 times to prepare the product.

[0016] As an optimization, the epoxy resin is designated as E-51.

[0017] Compared with the prior art, the beneficial effects achieved by the present invention are:

[0018] In preparing tung oil-modified epoxy resin, the present invention involves reacting tung oil sequentially with maleic anhydride, triethylenetetramine, and DOPO to obtain a tung oil curing agent; mixing epoxy resin, modified nano-silica, and tung oil reactive diluent evenly, then adding the tung oil curing agent, ultrasonically dispersing at room temperature, placing it in a mold for curing and shaping, and finally removing it from the mold to obtain the tung oil-modified epoxy resin.

[0019] First, this invention prepares tung oil into a tung oil active diluent and a tung oil curing agent, using green and environmentally friendly raw materials without generating any volatile organic gases. The tung oil active diluent is obtained by oxidizing tung oil with hydrogen peroxide solution. This active diluent contains aliphatic long-chain hydrocarbons, which can increase toughness and improve elongation at break. Modified nano-silica is prepared by reacting nano-silica with γ-methacryloyloxypropyltrimethoxysilane, improving the dispersibility of the modified nano-silica. Simultaneously, the epoxy groups on the surface of the modified nano-silica can participate in curing, thereby increasing tensile strength.

[0020] Secondly, tung oil curing agent was prepared by reacting maleic anhydride, triethylenetetramine, and DOPO in sequence. Maleic anhydride formed an anhydride structure on tung oil through cyclization addition. Triethylenetetramine reacted with the anhydride structure to form abundant curing binding sites on tung oil, which improved the curing effect. DOPO was grafted onto the tung oil curing agent through phosphorus hydroaddition, which improved the flame retardant effect and made the flame retardant effect stable. Compared with directly adding flame retardants, it is not easy to migrate or be lost. Detailed Implementation

[0021] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. 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 of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0022] To more clearly illustrate the method provided by the present invention, the following embodiments will be described in detail.

[0023] Example 1

[0024] A method for preparing tung oil-modified epoxy resin mainly includes the following preparation steps:

[0025] (1) In a nitrogen atmosphere, maleic anhydride and tung oil are mixed evenly at a mass ratio of 1:4. The mixture is stirred and refluxed at 100r / min for 3 hours at 120℃. Triethylenetetramine with a mass of 2 times that of maleic anhydride is added and the mixture is stirred and reacted for another 3 hours. Then, DOPO with a mass of 0.8 times that of maleic anhydride is added and the mixture is heated to 160℃ and stirred and reacted for another 8 hours to obtain tung oil curing agent.

[0026] (2) Take 25 parts of tung oil, 22 parts of acetic acid, 55 parts of 30% hydrogen peroxide solution, and 2 parts of 60% phosphoric acid solution according to the mass fraction. Heat the tung oil and keep it at 55°C. Under the stirring condition of 100r / min, add acetic acid, hydrogen peroxide solution and phosphoric acid solution at a uniform rate within 2h. After the addition is completed, continue stirring and react for 6h. Cool to room temperature and adjust the pH to neutral with 20% sodium carbonate solution. Let stand and separate the layers to remove the aqueous phase. Then wash with pure water three times and let stand and separate the layers to remove the aqueous phase. Then dry at 90°C for 4h to obtain tung oil active diluent.

[0027] (3) Mix nano-silica, γ-methacryloxypropyltrimethoxysilane and anhydrous ethanol in a mass ratio of 1:1:10, sonicate at room temperature for 8 min, add pure water equal to the mass of nano-silica, continue sonicating for 40 min, centrifuge and wash three times with pure water to obtain modified nano-silica; weigh 100 parts of E-51 epoxy resin, 10 parts of tung oil reactive diluent, 4 parts of modified nano-silica and 160 parts of tung oil curing agent according to the mass ratio; mix E-51 epoxy resin, modified nano-silica and tung oil reactive diluent evenly, add tung oil curing agent, sonicate at room temperature for 10 min, place in a mold, stand at 60℃ for 8 h, cool naturally to room temperature and then open the mold to obtain tung oil modified epoxy resin.

[0028] Example 2

[0029] A method for preparing tung oil-modified epoxy resin mainly includes the following preparation steps:

[0030] (1) In a nitrogen atmosphere, maleic anhydride and tung oil are mixed evenly at a mass ratio of 1:4. The mixture is stirred and refluxed at 150 r / min at 122℃ for 2.5 h. Triethylenetetramine with a mass of 2.1 times that of maleic anhydride is added and the mixture is stirred and reacted for another 3.5 h. Then DOPO with a mass of 0.9 times that of maleic anhydride is added and the mixture is heated to 165℃ and stirred and reacted for another 7 h to obtain tung oil curing agent.

[0031] (2) Take 28 parts of tung oil, 23 parts of acetic acid, 60 parts of 30% hydrogen peroxide solution, and 2.5 parts of 60% phosphoric acid solution according to the mass fraction. Heat the tung oil and keep it at 57°C. Under the stirring condition of 150 r / min, add acetic acid, hydrogen peroxide solution and phosphoric acid solution at a uniform rate within 2 hours. After the addition is completed, continue stirring and react for 5.5 hours. Cool to room temperature and adjust the pH to neutral with 20% sodium carbonate solution. Let stand and separate the layers to remove the aqueous phase. Then wash with pure water by stirring 4 times and let stand and separate the layers to remove the aqueous phase. Then dry at 92°C for 3.5 hours to obtain the tung oil active diluent.

[0032] (3) Mix nano-silica, γ-methacryloxypropyltrimethoxysilane and anhydrous ethanol in a mass ratio of 1:1:11, sonicate at room temperature for 9 min, add 1.5 times the mass of pure water of nano-silica, continue sonicating for 35 min, centrifuge and wash with pure water 4 times to obtain modified nano-silica; weigh 100 parts of E-51 epoxy resin, 12 parts of tung oil reactive diluent, 5 parts of modified nano-silica and 170 parts of tung oil curing agent according to the mass ratio; mix E-51 epoxy resin, modified nano-silica and tung oil reactive diluent evenly, add tung oil curing agent, sonicate at room temperature for 11 min, place in a mold, stand at 65℃ for 7 h, cool naturally to room temperature and then open the mold to obtain tung oil modified epoxy resin.

[0033] Example 3

[0034] A method for preparing tung oil-modified epoxy resin mainly includes the following preparation steps:

[0035] (1) In a nitrogen atmosphere, maleic anhydride and tung oil are mixed evenly at a mass ratio of 1:4. The mixture is stirred and refluxed at 100-200 r / min for 2 h at 125 °C. Triethylenetetramine with a mass of 2.2 times that of maleic anhydride is added, and the mixture is stirred and reacted for another 4 h. Then DOPO with a mass of 1.0 times that of maleic anhydride is added, and the mixture is heated to 170 °C and stirred and reacted for another 6 h to obtain tung oil curing agent.

[0036] (2) Take 30 parts of tung oil, 25 parts of acetic acid, 65 parts of 30% hydrogen peroxide solution, and 3 parts of 60% phosphoric acid solution according to the mass fraction. Heat the tung oil and keep it at 60°C. Under the stirring condition of 200r / min, add acetic acid, hydrogen peroxide solution and phosphoric acid solution at a uniform rate within 2 hours. After the addition is completed, continue stirring and react for 5 hours. Cool to room temperature and adjust the pH to neutral with 20% sodium carbonate solution. Let stand and separate the layers to remove the aqueous phase. Then wash with pure water 5 times and let stand and separate the layers to remove the aqueous phase. Then dry at 95°C for 3 hours to obtain the tung oil active diluent.

[0037] (3) Mix nano-silica, γ-methacryloxypropyltrimethoxysilane and anhydrous ethanol in a mass ratio of 1:1:12, sonicate at room temperature for 10 min, add pure water with a mass of 2 times that of nano-silica, continue sonicating for 40 min, centrifuge and wash with pure water 5 times to obtain modified nano-silica; weigh 100 parts of E-51 epoxy resin, 15 parts of tung oil reactive diluent, 6 parts of modified nano-silica and 180 parts of tung oil curing agent according to the mass fraction; mix E-51 epoxy resin, modified nano-silica and tung oil reactive diluent evenly, add tung oil curing agent, sonicate at room temperature for 12 min, place in a mold, stand at 70℃ for 6 h, cool naturally to room temperature and then open the mold to obtain tung oil modified epoxy resin.

[0038] Comparative Example 1

[0039] A method for preparing tung oil-modified epoxy resin mainly includes the following preparation steps:

[0040] (1) In a nitrogen atmosphere, maleic anhydride and tung oil are mixed evenly at a mass ratio of 1:4. The mixture is stirred and refluxed at 150 r / min at 122℃ for 2.5 h. Then, DOPO with a mass of 0.9 times that of maleic anhydride is added, and the temperature is raised to 165℃ and the reaction is continued for 7 h to obtain tung oil curing agent.

[0041] (2) Take 28 parts of tung oil, 23 parts of acetic acid, 60 parts of 30% hydrogen peroxide solution, and 2.5 parts of 60% phosphoric acid solution according to the mass fraction. Heat the tung oil and keep it at 57°C. Under the stirring condition of 150 r / min, add acetic acid, hydrogen peroxide solution and phosphoric acid solution at a uniform rate within 2 hours. After the addition is completed, continue stirring and react for 5.5 hours. Cool to room temperature and adjust the pH to neutral with 20% sodium carbonate solution. Let stand and separate the layers to remove the aqueous phase. Then wash with pure water by stirring 4 times and let stand and separate the layers to remove the aqueous phase. Then dry at 92°C for 3.5 hours to obtain the tung oil active diluent.

[0042] (3) Mix nano-silica, γ-methacryloxypropyltrimethoxysilane and anhydrous ethanol in a mass ratio of 1:1:11, sonicate at room temperature for 9 min, add 1.5 times the mass of pure water of nano-silica, continue sonicating for 35 min, centrifuge and wash with pure water 4 times to obtain modified nano-silica; weigh 100 parts of E-51 epoxy resin, 12 parts of tung oil reactive diluent, 5 parts of modified nano-silica and 170 parts of tung oil curing agent according to the mass ratio; mix E-51 epoxy resin, modified nano-silica and tung oil reactive diluent evenly, add tung oil curing agent, sonicate at room temperature for 11 min, place in a mold, stand at 65℃ for 7 h, cool naturally to room temperature and then open the mold to obtain tung oil modified epoxy resin.

[0043] Comparative Example 2

[0044] A method for preparing tung oil-modified epoxy resin mainly includes the following preparation steps:

[0045] (1) In a nitrogen atmosphere, maleic anhydride and tung oil are mixed evenly at a mass ratio of 1:4. The mixture is stirred and refluxed at 150 r / min at 122℃ for 2.5 h. Triethylenetetramine with a mass of 2.1 times that of maleic anhydride is added and the mixture is stirred and reacted for another 3.5 h to obtain tung oil curing agent.

[0046] (2) Take 28 parts of tung oil, 23 parts of acetic acid, 60 parts of 30% hydrogen peroxide solution, and 2.5 parts of 60% phosphoric acid solution according to the mass fraction. Heat the tung oil and keep it at 57°C. Under the stirring condition of 150 r / min, add acetic acid, hydrogen peroxide solution and phosphoric acid solution at a uniform rate within 2 hours. After the addition is completed, continue stirring and react for 5.5 hours. Cool to room temperature and adjust the pH to neutral with 20% sodium carbonate solution. Let stand and separate the layers to remove the aqueous phase. Then wash with pure water by stirring 4 times and let stand and separate the layers to remove the aqueous phase. Then dry at 92°C for 3.5 hours to obtain the tung oil active diluent.

[0047] (3) Mix nano-silica, γ-methacryloxypropyltrimethoxysilane and anhydrous ethanol in a mass ratio of 1:1:11, sonicate at room temperature for 9 min, add 1.5 times the mass of pure water of nano-silica, continue sonicating for 35 min, centrifuge and wash with pure water 4 times to obtain modified nano-silica; weigh 100 parts of E-51 epoxy resin, 12 parts of tung oil reactive diluent, 5 parts of modified nano-silica and 170 parts of tung oil curing agent according to the mass ratio; mix E-51 epoxy resin, modified nano-silica and tung oil reactive diluent evenly, add tung oil curing agent, sonicate at room temperature for 11 min, place in a mold, stand at 65℃ for 7 h, cool naturally to room temperature and then open the mold to obtain tung oil modified epoxy resin.

[0048] Comparative Example 3

[0049] A method for preparing tung oil-modified epoxy resin mainly includes the following preparation steps:

[0050] (1) In a nitrogen atmosphere, maleic anhydride and tung oil are mixed evenly at a mass ratio of 1:4. The mixture is stirred and refluxed at 150 r / min at 122℃ for 2.5 h. Triethylenetetramine with a mass of 2.1 times that of maleic anhydride is added and the mixture is stirred and reacted for another 3.5 h. Then DOPO with a mass of 0.9 times that of maleic anhydride is added and the mixture is heated to 165℃ and stirred and reacted for another 7 h to obtain tung oil curing agent.

[0051] (2) Nano silica, γ-methacryloxypropyltrimethoxysilane and anhydrous ethanol were mixed evenly in a mass ratio of 1:1:11, ultrasonicated at room temperature for 9 min, and pure water with a mass of 1.5 times that of nano silica was added. The mixture was ultrasonicated for another 35 min, centrifuged and washed 4 times with pure water to obtain modified nano silica. 100 parts of E-51 epoxy resin, 5 parts of modified nano silica and 170 parts of tung oil curing agent were weighed according to the mass ratio. The E-51 epoxy resin and modified nano silica were mixed evenly, and then tung oil curing agent was added. The mixture was ultrasonically dispersed at room temperature for 11 min, placed in a mold, and left to stand at 65℃ for 7 h. After naturally cooling to room temperature, the mold was opened and the mixture was taken out to obtain tung oil modified epoxy resin.

[0052] Comparative Example 4

[0053] A method for preparing tung oil-modified epoxy resin mainly includes the following preparation steps:

[0054] (1) In a nitrogen atmosphere, maleic anhydride and tung oil are mixed evenly at a mass ratio of 1:4. The mixture is stirred and refluxed at 150 r / min at 122℃ for 2.5 h. Triethylenetetramine with a mass of 2.1 times that of maleic anhydride is added and the mixture is stirred and reacted for another 3.5 h. Then DOPO with a mass of 0.9 times that of maleic anhydride is added and the mixture is heated to 165℃ and stirred and reacted for another 7 h to obtain tung oil curing agent.

[0055] (2) Take 28 parts of tung oil, 23 parts of acetic acid, 60 parts of 30% hydrogen peroxide solution, and 2.5 parts of 60% phosphoric acid solution according to the mass fraction. Heat the tung oil and keep it at 57°C. Under the stirring condition of 150 r / min, add acetic acid, hydrogen peroxide solution and phosphoric acid solution at a uniform rate within 2 hours. After the addition is completed, continue stirring and react for 5.5 hours. Cool to room temperature and adjust the pH to neutral with 20% sodium carbonate solution. Let stand and separate the layers to remove the aqueous phase. Then wash with pure water by stirring 4 times and let stand and separate the layers to remove the aqueous phase. Then dry at 92°C for 3.5 hours to obtain the tung oil active diluent.

[0056] (3) Weigh 100 parts of E-51 epoxy resin, 12 parts of tung oil reactive diluent, 5 parts of nano silica, and 170 parts of tung oil curing agent according to the mass fraction; mix E-51 epoxy resin, nano silica, and tung oil reactive diluent evenly, then add tung oil curing agent, ultrasonically disperse at room temperature for 11 min, place in a mold, stand at 65℃ for 7 h, and after naturally cooling to room temperature, open the mold and take out to obtain tung oil modified epoxy resin.

[0057] Test case

[0058] Testing of tensile strength and elongation at break

[0059] Test method: Prepare specimens according to GB / T 2567 and test tensile strength and elongation at break using an MDW-10 universal tensile testing machine at a tensile speed of 2 mm / min.

[0060] Flame retardant performance testing

[0061] Test method: The limiting oxygen index is tested according to GB / T2406.2 standard.

[0062] The results are shown in Table 1.

[0063] Tensile strength:

[0064] Table 1

[0065] Tensile strength elongation Limiting oxygen index Example 1 67.5MPa 7.3％ 30.9％ Example 2 68.1MPa 7.3％ 31.3％ Example 3 68.3MPa 7.1％ 31.8％ Comparative Example 1 41.8MPa 7.8％ 31.7％ Comparative Example 2 67.9MPa 8.1％ 22.8％ Comparative Example 3 68.2MPa 5.7％ 31.7％ Comparative Example 4 54.8MPa 7.6％ 30.2％

[0066] A comparison of the experimental data from Examples 1-3 and Comparative Examples 1-4 in Table 1 reveals that the tung oil-modified epoxy resin prepared by this invention possesses excellent mechanical and flame-retardant properties.

[0067] By comparing Examples 1-3 and Comparative Example 1, it can be found that although the anhydride groups have a certain curing effect when the tung oil curing agent is prepared without the reaction of triethylenetetramine, there are fewer curing sites, resulting in a decrease in curing effect. Therefore, the tung oil curing agent prepared using triethylenetetramine can achieve better tensile strength.

[0068] By comparing Examples 1-3 and Comparative Example 2, it can be found that DOPO is grafted onto tung oil curing agent through phosphohydrogenation, giving it good overall flame retardant properties.

[0069] By comparing Examples 1-3 and Comparative Example 3, it can be found that the tung oil active diluent contains aliphatic long-chain hydrocarbons, which can increase toughness and improve elongation at break.

[0070] By comparing Examples 1-3 and Comparative Example 4, it can be found that modifying nano-silica improves the dispersibility of the modified nano-silica. At the same time, the epoxy groups on the surface of the modified nano-silica can participate in curing, thereby improving the tensile strength.

[0071] 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 its spirit or essential characteristics. 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, all variations falling within the meaning and scope of equivalents of the claims are intended to be included within the present invention. No markings in the claims should be construed as limiting the scope of the claims.

Claims

1. A tung oil-modified epoxy resin, characterized in that, By weight, it includes the following components: 100 parts epoxy resin, 10-15 parts tung oil reactive diluent, 4-6 parts modified nano silica, and 160-180 parts tung oil curing agent. The tung oil active diluent is prepared by oxidizing tung oil with hydrogen peroxide solution. The modified nano-silica is prepared by reacting nano-silica with γ-methacryloxypropyltrimethoxysilane; The preparation method of the tung oil curing agent is as follows: Under a nitrogen atmosphere, maleic anhydride and tung oil are mixed evenly at a mass ratio of 1:

4. The mixture is stirred and refluxed at 100-200 r / min for 2-3 hours at 120-125℃. Then, triethylenetetramine with a mass of 2-2.2 times that of maleic anhydride is added, and the mixture is stirred and reacted for another 3-4 hours. Finally, DOPO with a mass of 0.8-1.0 times that of maleic anhydride is added, and the mixture is heated to 160-170℃ and stirred and reacted for another 6-8 hours to obtain the tung oil curing agent.

2. A method for preparing tung oil-modified epoxy resin, characterized in that, The preparation steps include the following: (1) In a nitrogen atmosphere, maleic anhydride and tung oil are mixed evenly at a mass ratio of 1:

4. The mixture is stirred and refluxed at 100-200 r / min for 2-3 h at 120-125 °C. Triethylenetetramine with a mass of 2-2.2 times that of maleic anhydride is added and the mixture is stirred and reacted for 3-4 h. Then, DOPO with a mass of 0.8-1.0 times that of maleic anhydride is added and the mixture is heated to 160-170 °C and stirred and reacted for 6-8 h to obtain tung oil curing agent. (2) Heat tung oil and keep it at 55~60℃. Under stirring conditions of 100~200r / min, add acetic acid, hydrogen peroxide solution and phosphoric acid solution at a uniform rate within 2h. After the addition is completed, continue stirring and react for 5~6h. Cool to room temperature and adjust the pH to neutral with 20% sodium carbonate solution. Let stand to separate the layers and remove the aqueous phase. Then wash with pure water 3~5 times and let stand to separate the layers to remove the aqueous phase. Then dry at 90~95℃ for 3~4h to obtain tung oil active diluent. (3) Weigh 100 parts of epoxy resin, 10-15 parts of tung oil reactive diluent, 4-6 parts of modified nano silica, and 160-180 parts of tung oil curing agent according to the mass fraction; mix the epoxy resin, modified nano silica, and tung oil reactive diluent evenly, then add the tung oil curing agent, ultrasonically disperse at room temperature for 10-12 minutes, place in a mold, stand at 60-70℃ for 6-8 hours, and after naturally cooling to room temperature, open the mold and take out the product to obtain tung oil modified epoxy resin; the modified nano silica is prepared by reacting nano silica and γ-methacryloyloxypropyltrimethoxysilane.

3. The method for preparing tung oil-modified epoxy resin according to claim 2, characterized in that, The hydrogen peroxide solution in step (2) is a 30% hydrogen peroxide solution by mass; the phosphoric acid solution is a 60% phosphoric acid solution by mass; the relative quantities of the tung oil, acetic acid, hydrogen peroxide solution and phosphoric acid solution are as follows, by mass fraction: 25-30 parts of tung oil, 22-25 parts of acetic acid, 55-65 parts of 30% hydrogen peroxide solution and 2-3 parts of 60% phosphoric acid solution.

4. The method for preparing tung oil-modified epoxy resin according to claim 2, characterized in that, The modified nano silica in step (3) is prepared by mixing nano silica, γ-methacryloxypropyltrimethoxysilane and anhydrous ethanol in a mass ratio of 1:1:10~12, sonicating at room temperature for 8~10 min, adding 1~2 times the mass of pure water to the nano silica, sonicating for another 30~40 min, centrifuging, and washing with pure water 3~5 times to obtain the modified nano silica.

5. The method for preparing tung oil-modified epoxy resin according to claim 2, characterized in that, The epoxy resin is of type E-51.