Supported heat-resistant additive as well as preparation method and application thereof

Abstract

The invention discloses a supported heat-resistant additive, which is prepared from the following ingredients in percentage by mass: 30 to 69.5 percent of hexagonal boron nitride nanosheets, 30 to 69.5 percent of metal oxides and 0.5 to 5 percent of silane coupling agents. The preparation method comprises the following steps: S1, carrying out plasma ball milling on hexagonal boron nitride particles to obtain partially stripped boron nitride powder; s2, dispersing the powder in a mixed solution of isopropanol, ethanol and water, adding a silane coupling agent, performing ultrasonic treatment and high-speed centrifugation, taking supernatant liquid, and performing freeze drying to obtain silane modified boron nitride nanosheets; s3, mixing the silane modified boron nitride nanosheet with an alcohol solvent, mixing a metal oxide with ethanol, and fully dissolving; mixing the two mixed solutions, adding excessive sodium hydroxide, transferring the mixed solutions into a reaction kettle, and carrying out solvothermal reaction; and after the reaction is completed, collecting a solid precipitate through high-speed centrifugation, and drying to obtain the heat-resistant additive of the boron nitride nanosheet loaded with the metal oxide. The high temperature resistance of the silicone rubber can be remarkably improved.

Description

Technical Field

[0001] The present invention relates to the technical field of silicone rubber processing, and particularly to a supported heat-resistant additive, a preparation method thereof, and an application thereof. Background Art

[0002] Silicone rubber is a polymer material with excellent comprehensive properties, having good high and low temperature resistance, insulation, weather resistance, and biocompatibility, and is widely used in the fields of mechanical chemical industry, electronic and electrical, biological medicine, aerospace, etc. The main chain of the silicone rubber molecule is composed of Si-O linkages, and the bond energy of the main chain is higher, so the upper limit of the heat-resistant temperature of silicone rubber reaches 250°C. With the continuous development of modern industry, in specific application scenarios, it is required that the heat-resistant temperature of silicone rubber can reach above 300°C, while existing ordinary silicone rubber cannot meet this temperature resistance requirement. Summary of the Invention

[0003] Aiming at the deficiencies of the above-mentioned prior art, the technical problem to be solved by this patent application is how to provide a supported heat-resistant additive, a preparation method thereof, and an application thereof.

[0004] To solve the above technical problems, the present invention adopts the following technical solutions:

[0005] A supported heat-resistant additive, a preparation method thereof, and an application thereof, calculated by mass fraction, include the following components: hexagonal boron nitride nanosheets 30 - 69.5%, metal oxide 30 - 69.5%, and silane coupling agent 0.5 - 5%.

[0006] A preparation method of a supported heat-resistant additive includes the following steps:

[0007] S1: Plasma ball-mill hexagonal boron nitride particles in a ball mill to obtain partially exfoliated boron nitride powder;

[0008] S2: Disperse the partially exfoliated boron nitride powder in a mixed solution of isopropanol, ethanol, and water, stir evenly, then add a silane coupling agent, perform ultrasonic treatment, then centrifuge at high speed, take the supernatant, and freeze-dry to obtain silane-modified boron nitride nanosheets;

[0009] S3: Mix and fully disperse the silane-modified boron nitride nanosheets with an alcohol solvent, and fully dissolve the metal oxide with ethanol; after the two mixed solutions are mixed evenly, add an excessive amount of sodium hydroxide, stir evenly, transfer the mixed solution to a reaction kettle, and perform a solvothermal reaction; after the reaction is completed, centrifuge at high speed to collect the solid precipitate, and dry to prepare a heat-resistant additive of boron nitride nanosheets loaded with metal oxide.

[0010] Preferably, the thickness of the hexagonal boron nitride particles is 1 - 5 μm, and the radial width is 5 - 30 μm.

[0011] Preferably, the metal oxide is one or more of titanium oxide, cobalt oxide, nickel oxide, yttrium oxide, cerium oxide and iron oxide, and the loading rate of the metal oxide on the modified boron nitride nanosheet is 30-70%.

[0012] Preferably, in step S2, the mass ratio of the mixed solution of ethanol, isopropanol and water is 5-20:60-80:90-100.

[0013] Preferably, in step S2, the silane coupling agent includes one or several of hexamethyldisilazane, dodecyltrimethoxysilane, 3-ureidopropyltriethoxysilane and 3-ureidopropyltrimethoxysilane, and the mass fraction of the silane coupling agent in the modified boron nitride nanosheet is 1%-5%.

[0014] Preferably, in step S1, the plasma ball milling time is 2-8 h, the discharge voltage is 4-8 kV, and the ball milling speed is 1000-3000 rpm.

[0015] Preferably, in step S2, the ultrasonic treatment power is 200-500 W, and the ultrasonic time is 6-12 h.

[0016] Preferably, in step S3, the solvothermal reaction temperature is 160-200 °C, and the reaction time is 12-24 h.

[0017] For the application of the supported heat-resistant additive in silicone rubber, calculated by mass fraction, the dosage of the heat-resistant additive is 1-5%.

[0018] Preferably, in step S2, the vacuum drying temperature is -70 to -50 °C, and the drying time is 12-48 h.

[0019] Preferably, in steps S2 and S3, the stirring rate is 300-2000 rpm, and the stirring time is 10-60 min.

[0020] Preferably, the alcohol solvent in step S3 includes one or more of ethanol and isopropanol.

[0021] Preferably, in the mixed solution in step S3, the mass ratio of the modified hexagonal boron nitride, metal inorganic acid salt and alcohol solvent is 2-5:8-20:90-100.

[0022] Preferably, the metal inorganic acid salt required for the solvothermal reaction in step S3 includes at least one of iron salt, cobalt salt, cerium salt, iron salt, nickel salt and yttrium salt.

[0023] Preferably, the titanium salt is one or more of titanium tetrachloride and titanium sulfate.

[0024] Preferably, the cobalt salt is one or more of cobalt sulfate and cobalt nitrate.

[0025] Preferably, the cerium salt is one or more of cerium nitrate and cerium chloride.

[0026] Preferably, the iron salt is one or more of ferrous sulfate, ferric sulfate, and ferric chloride.

[0027] Preferably, the nickel salt is one or more of nickel sulfate and nickel nitrate.

[0028] In summary, the supported heat-resistant additive prepared by the present invention is a composite filler of modified boron nitride nanosheets loaded with metal compounds. This composite filler has both the oxygen shielding and barrier effect of boron nitride nanosheets and the free radical quenching effect of metal oxides, thus being able to maximize the improvement of the high-temperature performance of solid or liquid silicone rubber and expand the application of silicone rubber materials in fields such as high-temperature equipment, high-temperature sealing, electronic component packaging, and national defense and military industries.

[0029] The specific beneficial effects are as follows:

[0030] 1) By the solvothermal method, metal compounds are loaded on modified boron nitride nanosheets to obtain a supported heat-resistant additive. The metal compounds have excellent free radical quenching functions, can consume silicone rubber macromolecular free radicals, significantly inhibit the thermal decomposition of silicone rubber, and thus significantly improve the heat resistance of silicone rubber;

[0031] 2) In the present invention, hexagonal boron nitride particles are exfoliated into boron nitride nanosheets through plasma ball milling combined with ultrasonic dispersion, which greatly increases the specific surface area of boron nitride. At the same time, more oxygen-containing groups are generated on the surface of boron nitride by plasma action, which can form a tighter interfacial bond with metal oxides during the annealing process. At the same time, the boron nitride nanosheets are beneficial to extending the propagation path of oxygen through silicone rubber, significantly improving the oxygen shielding and barrier effect of silicone rubber, and thus improving the heat-resistant oxidation performance of silicone rubber.

[0032] 3) The dosage of this supported heat-resistant additive in silicone rubber is small, only accounting for 1% - 5% of the mass percentage of silicone rubber, and can increase the heat-resistant temperature of silicone rubber to 300°C. In addition, this additive is dispersed in silicone rubber without obvious particle feeling and does not affect the color matching of silicone rubber. Description of the Drawings

[0033] Figure 1 is the SEM image of the supported heat-resistant additive, with magnification factors of 10,000 times (right figure) and 100,000 times (left figure) respectively.

[0034] Figure 2 is the comparison diagram of the appearance of the material before and after aging at 300°C for 168 h in Example 1. The left sample is the appearance before aging, and the right is the appearance after aging.

[0035] Figure 3 Figure of the appearance of the material before and after aging at 300 °C for 168 h in Example 2. The sample on the left is the appearance before aging, and the one on the right is the appearance after aging.

[0036] Figure 4 Figure of the appearance of the material before and after aging at 300 °C for 168 h in Example 3. The sample on the left is the appearance before aging, and the one on the right is the appearance after aging.

[0037] Figure 5 Figure of the appearance of the material before and after aging at 300 °C for 168 h in Example 4. The sample on the left is the appearance before aging, and the one on the right is the appearance after aging.

[0038] Figure 6 Figure of the appearance of the material before and after aging at 300 °C for 168 h in Example 5. The sample on the left is the appearance before aging, and the one on the right is the appearance after aging.

[0039] Figure 7 Figure of the appearance of the material before and after aging at 300 °C for 168 h in Comparative Example 1. The sample on the left is the appearance before aging, and the one on the right is the appearance after aging.

[0040] Figure 8 Figure of the appearance of the material before and after aging at 300 °C for 168 h in Comparative Example 2. The sample on the left is the appearance before aging, and the one on the right is the appearance after aging. Detailed implementation manners

[0041] In order to better introduce the technical solutions and advantages of the present invention, the present invention will be further explained and described below in conjunction with specific embodiments. The described embodiments are part of the embodiments of the present invention, rather than all of the embodiments.

[0042] Example 1:

[0043] A supported heat-resistant additive, by mass percentage, including 56.2% of boron nitride nanosheets, 19.1% of cerium oxide, 10.4% of titanium dioxide, 11.1% of cobalt oxide, and 3.2% of hexamethyldisilazane. The preparation method of the heat-resistant additive includes the following steps:

[0044] Hexagonal boron nitride particles are subjected to plasma ball milling in a ball mill for 6 h, the discharge voltage is 6 kV, and the ball milling speed is 2000 rpm to obtain partially exfoliated boron nitride powder;

[0045] The above-mentioned partially exfoliated boron nitride powder is mixed with isopropanol, ethanol and water at a mass ratio of 10:20:80:10, and magnetically stirred at 600 rpm for 15 min to prepare a mixed solution. Subsequently, hexamethyldisilazane is added at a mass ratio of mixed solution: silane coupling agent = 100:1, ultrasonically treated in an ultrasonic cleaner for 12 h, transferred to a centrifuge and centrifuged at 3000 rpm for 15 min to remove the boron nitride precipitate that is not fully exfoliated at the bottom. The supernatant is freeze-dried in a freeze dryer for 48 h to obtain modified boron nitride nanosheets;

[0046] The modified boron nitride nanosheets are mixed with isopropanol at a mass ratio of 1:8, and stirred with a magnetic stirrer at 600 rpm for 30 min to fully disperse the nanosheets. Subsequently, ethanol, cerium nitrate, titanium tetrachloride and cobalt nitrate are mixed at a mass ratio of 50:3:2:2, and stirred at 600 rpm for 30 min to fully dissolve the above metal compounds. Then, the above two mixed solutions are mixed at a mass ratio of 1:1.05. Then, according to the mass ratio of mixed solution: NaOH = 20:1, NaOH is added, and stirred at 600 rpm for 30 min. After mixing evenly, the mixed solution is transferred to a reaction kettle for solvothermal reaction. After reacting at 160 °C for 12 h, the reaction product is centrifuged at 2000 rpm for 5 min in a centrifuge, and the solid precipitate is collected. The precipitate is placed in an oven and dried at 80 °C for 8 h to obtain a composite filler of boron nitride nanosheets loaded with metal oxides;

[0047] Example 2:

[0048] A supported heat-resistant additive, by mass percentage, wherein boron nitride nanosheets are 53.8%, copper oxide is 17.7%, iron oxide is 12.2%, nickel oxide is 13.2%, and hexamethyldisilazane is 3.1%. The preparation method of the heat-resistant additive includes the following steps:

[0049] Hexagonal boron nitride particles are subjected to plasma ball milling in a ball mill for 6 h, the discharge voltage is 6 kV, and the ball milling speed is 2000 rpm to obtain partially exfoliated boron nitride flake powder;

[0050] The above-mentioned partially exfoliated boron nitride powder is mixed with isopropanol, ethanol and water at a mass ratio of 10:20:80:10, and magnetically stirred at 600 rpm for 15 min to prepare a mixed solution. Subsequently, hexamethyldisilazane is added at a mass ratio of mixed solution: silane coupling agent = 100:1, ultrasonically treated in an ultrasonic cleaner for 12 h, transferred to a centrifuge and centrifuged at 3000 rpm for 15 min to remove the boron nitride precipitate that is not fully exfoliated at the bottom. The supernatant is dried in a freeze dryer for 48 h to obtain modified boron nitride nanosheets;

[0051] Mix the modified boron nitride nanosheets and isopropanol at a mass ratio of 1:8, and stir with a magnetic stirrer at 600 rpm for 30 min to fully disperse the nanosheets. Subsequently, mix ethanol, copper sulfate, ferrous sulfate, and nickel chloride at a mass ratio of 50:3:2:2, and stir at 600 rpm for 30 min to fully dissolve the above metal compounds. Then mix the above two mixtures at a mass ratio of 1:1.05. Then, add NaOH at a mass ratio of mixture:NaOH = 20:1, and stir at 600 rpm for 30 min to obtain a mixture. Then transfer the mixture to a reaction kettle for solvothermal reaction. After reacting at 160 °C for 12 h, centrifuge the reaction product at 2000 rpm for 5 min in a centrifuge, collect the solid precipitate, and dry it in an oven at 80 °C for 8 h to obtain a composite filler of boron nitride nanosheet supported metal oxide;

[0052] Example 3:

[0053] A supported heat-resistant additive, by mass percentage, including 56.1% of boron nitride nanosheets, 19.2% of cerium oxide, 10.4% of titanium dioxide, 11.1% of cobalt oxide, and 3.2% of hexamethyldisilazane. The preparation method of the heat-resistant additive includes the following steps:

[0054] Hexagonal boron nitride particles are subjected to plasma ball milling in a ball mill for 6 h, the discharge voltage is 6 kV, and the ball milling speed is 2000 rpm to obtain partially exfoliated boron nitride powder;

[0055] Mix the above partially exfoliated boron nitride powder, isopropanol, ethanol, and water at a mass ratio of 10:20:80:10, and stir magnetically at 600 rpm for 15 min to make a mixture. Subsequently, add hexamethyldisilazane at a mass ratio of mixture:silane coupling agent = 100:1, ultrasonically treat it in an ultrasonic cleaner for 12 h, transfer it to a centrifuge and centrifuge at 3000 rpm for 15 min to remove the boron nitride precipitate that is not fully exfoliated at the bottom, and freeze-dry the supernatant in a freeze dryer for 48 h to obtain modified boron nitride nanosheets;

[0056] Mix the modified boron nitride nanosheets and isopropanol at a mass ratio of 1:8, and stir magnetically at 600 rpm for 30 min to fully disperse the nanosheets. Subsequently, mix ethanol, cerium nitrate, titanium tetrachloride, and cobalt nitrate at a mass ratio of 50:3:2:2, and stir magnetically at 600 rpm for 30 min to fully dissolve the above metal compounds. Then mix the above two mixtures at a mass ratio of 1:1.05. Then, add NaOH according to the mass ratio of mixture:NaOH = 20:1, stir at 600 rpm for 30 min to obtain a mixture, and then transfer the mixture to a reaction kettle for solvothermal reaction. After reacting at 160 °C for 24 h, centrifuge the reaction product at 2000 rpm for 5 min in a centrifuge, collect the solid precipitate, and dry it in an oven at 80 °C for 8 h to obtain a composite filler of boron nitride nanosheets loaded with metal oxides;

[0057] Example 4:

[0058] A supported heat-resistant additive, by mass percentage, wherein boron nitride nanosheets are 56.1%, cerium oxide is 19.2%, titanium dioxide is 10.4%, cobalt oxide is 11.1%, and 3-ureidopropyltriethoxysilane is 3.2%. The preparation method of the heat-resistant additive includes the following steps:

[0059] Hexagonal boron nitride particles are subjected to plasma ball milling in a ball mill for 6 h, the discharge voltage is 6 kV, and the ball milling speed is 2000 rpm to obtain partially exfoliated boron nitride powder;

[0060] Mix the above partially exfoliated boron nitride powder, isopropanol, ethanol, and water at a mass ratio of 10:20:80:10, and stir at 600 rpm for 15 min to prepare a mixture. Subsequently, add 3-ureidopropyltriethoxysilane according to the mass ratio of mixture:silane coupling agent = 100:1, ultrasonically treat it in an ultrasonic cleaner for 12 h, transfer it to a centrifuge and centrifuge at 3000 rpm for 15 min to remove the boron nitride precipitate that is not fully exfoliated at the bottom, and freeze-dry the supernatant in a freeze dryer for 48 h to obtain modified boron nitride nanosheets;

[0061] Mix the modified boron nitride nanosheets and isopropanol at a mass ratio of 1:8, and magnetically stir at 600 rpm for 30 min to disperse the nanosheets. Subsequently, mix ethanol, cerium nitrate, titanium tetrachloride, and cobalt nitrate at a mass ratio of 50:3:2:2, and stir at 600 rpm for 30 min to fully dissolve the above metal salts. Finally, mix the above two mixed solutions at a mass ratio of 1:1.05. Then, add NaOH according to the mass ratio of the mixed solution:NaOH of 20:1, stir at 600 rpm in a magnetic stirrer for 30 min, transfer the mixed solution to a reaction kettle for solvothermal reaction. After reacting at 160 °C for 12 h, centrifuge the reaction product at 2000 rpm in a centrifuge for 5 min, collect the solid precipitate, and dry it in an oven at 80 °C for 8 h to obtain a composite filler of boron nitride nanosheet-supported metal oxide;

[0062] Example 5:

[0063] A supported heat-resistant additive, by mass percentage, including 68.9% of boron nitride nanosheets, 12.5% of copper oxide, 6.6% of iron oxide, 7.2% of nickel oxide, and 4.8% of hexamethyldisilazane. The preparation method of the heat-resistant additive includes the following steps:

[0064] Hexagonal boron nitride particles are subjected to plasma ball milling in a ball mill for 6 h, the discharge voltage is 6 kV, and the ball milling speed is 2000 rpm to obtain partially exfoliated boron nitride powder;

[0065] Mix the above partially exfoliated boron nitride powder, isopropanol, ethanol, and water at a mass ratio of 10:20:80:10, and stir in a beaker at 600 rpm for 15 min to prepare a mixed solution. Subsequently, add hexamethyldisilazane according to the mass ratio of the mixed solution:silane coupling agent = 100:1, ultrasonically treat in an ultrasonic cleaner for 12 h, transfer to a centrifuge and centrifuge at 3000 rpm for 15 min to remove the boron nitride precipitate that is not fully exfoliated at the bottom, and freeze-dry the supernatant in a freeze dryer for 48 h to obtain modified boron nitride nanosheets;

[0066] Mix the modified boron nitride nanosheets and isopropanol at a mass ratio of 1:8, and stir magnetically at 600 rpm for 30 min to fully disperse the nanosheets. Subsequently, mix ethanol, copper sulfate, ferrous sulfate, and nickel chloride at a mass ratio of 50:2:1:1, and stir magnetically at 600 rpm for 30 min to fully dissolve the above metal compounds. Then mix the above two mixtures at a mass ratio of 1:1.05. Add NaOH at a mass ratio of mixture:NaOH = 20:1, and stir magnetically at 600 rpm for 30 min to obtain a mixture. Then transfer the mixture to a reaction kettle for solvothermal reaction. After reacting at 160 °C for 24 h, centrifuge the reaction product at 2000 rpm for 5 min in a centrifuge, collect the solid precipitate, and place it in an oven at 80 °C for drying for 8 h to prepare a composite filler of boron nitride nanosheet-supported metal oxide;

[0067] Comparative Example 1:

[0068] A supported heat-resistant additive, by mass percentage, cerium oxide 47.7%, titanium dioxide 25.2%, cobalt oxide 27.1%, and its preparation method includes the following steps:

[0069] Mix ethanol, cerium nitrate, titanium tetrachloride, and cobalt nitrate at a mass ratio of 50:3:2:2, stir magnetically at 600 rpm for 30 min, then add NaOH at a mass ratio of mixture:NaOH = 10:1, stir magnetically at 600 rpm for 30 min to obtain a mixture. Then transfer the mixture to a reaction kettle for solvothermal reaction. After reacting at 160 °C for 12 h, centrifuge at 2000 rpm for 5 min in a centrifuge to collect the solid precipitate, and place it in an oven at 80 °C for drying for 8 h to prepare a composite filler of metal oxide particles;

[0070] Comparative Example 2:

[0071] A supported heat-resistant additive, by mass percentage, boron nitride nanosheets 95.3%, hexamethyldisilazane 4.7%, and its preparation method includes the following steps:

[0072] Hexagonal boron nitride particles are subjected to plasma ball milling in a ball mill for 6 h, the discharge voltage is 6 kV, and the ball milling speed is 2000 rpm to obtain partially exfoliated boron nitride powder;

[0073] The above-mentioned partially exfoliated boron nitride powder is mixed with isopropanol, ethanol, and water at a mass ratio of 10:20:80:10, and stirred at 600 rpm for 15 min to prepare a mixed solution. Subsequently, hexamethyldisilazane is added at a mass ratio of mixed solution: silane coupling agent = 100:1, and ultrasonic treatment is carried out in an ultrasonic cleaner for 12 h. Then it is transferred to a centrifuge and centrifuged at 3000 rpm for 15 min to remove the boron nitride precipitate that is not fully exfoliated at the bottom. The supernatant is freeze-dried in a freeze dryer for 48 h to obtain modified boron nitride nanosheets.

[0074] The supported heat-resistant additives prepared in Examples 1 to 5 and Comparative Examples 1 to 2 are mixed evenly with methyl vinyl silicone oil, fumed silica, MQ resin, hydrogen-containing silicone oil, platinum catalyst, and inhibitor at a mass ratio of 3:60:30:20:2:0.5:0.01, and vulcanized at 130 °C for 15 min on a flat vulcanizer to prepare silicone rubber vulcanizates.

[0075] Performance test:

[0076] The hardness, tensile strength, and elongation at break of the samples are measured with reference to the national standards GB / T531.1-2008 and GB / T528-2009. The samples are subjected to a thermal oxygen aging test with reference to the national standard GB / T3512-2014, the aging temperature is 300 °C, and the aging time is 168 h. The hardness, tensile strength, and elongation at break of the samples after aging are measured, and the test results are shown in Table 1.

[0077] Table 1 Comparison of the mechanical properties of the corresponding samples before and after aging in each example

[0078]

[0079] It can be seen from the data in Table 1 that:

[0080] 1) In Examples 1 to 5, the hardness of the silicone rubber before aging was above 65 degrees (Shore A), the tensile strength was greater than 8 MPa, and the elongation at break was greater than 400%. After aging at 300 °C for 168 h, the hardness of the silicone rubber was below 90 degrees (Shore A), the tensile strength was about 6 MPa, and the elongation at break was about 150%, indicating that the heat-resistant additives prepared in Examples 1 to 5 significantly improved the high-temperature resistance of the silicone rubber. Different metal salts were used in Examples 1 and 2, and the prepared heat-resistant additives both had good heat-resistant modification effects. The solvothermal reaction time in Example 3 was longer than that in Examples 1 and 2, which was beneficial to increasing the loading amount of metal oxides on the surface of boron nitride nanosheets, and thus the improvement of the heat resistance of the silicone rubber was more significant. In Example 4, 3-ureidopropyltriethoxysilane was used for surface modification of boron nitride nanosheets, and the prepared heat-resistant additive also had good heat resistance for the silicone rubber. The content of metal oxides loaded on the heat-resistant additive prepared in Example 5 was relatively low, so the improvement effect on the heat resistance of the silicone rubber was poor.

[0081] 2) By comparing the performance results of Examples 1 to 5 with those of Comparative Example 1, it can be seen that in Comparative Example 1, only metal oxides were used as heat-resistant additives. After aging at 300 °C for 168 h, the hardness of the silicone rubber material was greater than that corresponding to Examples 1 to 5, and the tensile strength and elongation were significantly lower than those corresponding to Examples 1 to 5, indicating that the combination of modified boron nitride nanosheets and metal oxides in the supported heat-resistant additive was the key to improving the heat resistance of the silicone rubber.

[0082] 3) Figure 1 are SEM images of the supported heat-resistant additive at magnification factors of 10,000 times and 100,000 times respectively. As Figure 1 shown, in the heat-resistant additives obtained in Examples 1 to 5, a large number of metal oxide particles were attached to the surface of boron nitride nanosheets. Metal oxides can quench the free radicals generated during the aging process of silicone rubber, and further delay the thermal-oxidative aging rate of silicone rubber and improve its heat resistance through the oxygen barrier effect of boron nitride nanosheets.

[0083] 4) Figure 2 are the external shape comparison diagrams of the materials of Examples 1 to 5 and Comparative Examples 1 to 2 before and after aging at 300 °C for 168 h. The samples on the left are the external shapes before aging, and the right ones are the external shapes after aging. From Figure 2It can be seen that after high-temperature aging of Examples 1 to 5 and Comparative Example 1, the main change in the shape of the material is the reduction in size, and there is no obvious change in color. In Comparative Example 1, when a metal oxide is used alone as a heat-resistant additive, after aging at 300 °C for 168 h, the size shrinkage of the material is more obvious, which is significantly greater than the shrinkage of the corresponding material shape sizes in Examples 1 to 5. In Comparative Example 2, only modified boron nitride nanosheets are used as heat-resistant additives. After the vulcanizate prepared by mixing with silicone rubber is aged at 300 °C for 168 h, the sample ruptures and the aging is severe.

[0084] Finally, it should be noted that those skilled in the art can make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to include these modifications and variations.

Claims

1. A supported heat-resistant additive, characterized in that: Calculated by mass fraction, the invention comprises the following components: 30-69.5% of hexagonal boron nitride nanosheets, 30-69.5% of metal oxides and 0.5-5% of silane coupling agents.

2. A method for preparing a supported heat-resistant additive, characterized in that: The following steps are involved: S1: plasma milling hexagonal boron nitride particles in a ball mill to obtain partially exfoliated boron nitride powder; S2: dispersing the partially exfoliated boron nitride powder in a mixture of isopropanol, ethanol and water, stirring evenly, adding a silane coupling agent, ultrasonically treating, centrifuging at high speed, taking the supernatant, and freeze-drying to obtain silane-modified boron nitride nanosheets; S3: Mix silane-modified boron nitride nanosheets with alcohol solvents and fully disperse them, and mix metal oxides with ethanol and fully dissolve them; after the two mixed solutions are evenly mixed, add excess sodium hydroxide, stir evenly, and transfer the mixed solution into a reactor to perform a solvent thermal reaction; after the reaction is completed, collect the solid precipitate by high-speed centrifugation, and dry it to obtain a heat-resistant additive of boron nitride nanosheets loaded with metal oxides.

3. The method for preparing a supported heat-resistant additive according to claim 2, characterized in that: The hexagonal boron nitride particles have a thickness of 1 to 5 μm and a radial width of 5 to 30 μm.

4. The method for preparing a supported heat-resistant additive according to claim 2, characterized in that: The metal oxide is one or more of titanium oxide, cobalt oxide, nickel oxide, yttrium oxide, cerium oxide and iron oxide, and the loading rate of the metal oxide on the modified boron nitride nanosheet is 30-70%.

5. The method for preparing a supported heat-resistant additive according to claim 2, characterized in that: In step S2, the mass ratio of the mixed solution of ethanol, isopropanol and water is 5-20:60-80:90-100.

6. The method for preparing a supported heat-resistant additive according to claim 2, characterized in that: In step S2, the silane coupling agent includes one or more of hexamethyldisilazane, dodecyltrimethoxysilane, 3-ureapropyltriethoxysilane and 3-ureapropyltrimethoxysilane, and the mass fraction of the silane coupling agent in the modified boron nitride nanosheets is 1% to 5%.

7. The method for preparing a supported heat-resistant additive according to claim 2, characterized in that: In step S1, the plasma ball milling time is 2 to 8 hours, the discharge voltage is 4 to 8 kV, and the ball milling speed is 1000 to 3000 rpm.

8. The method for preparing a supported heat-resistant additive according to claim 2, characterized in that: In step S2, the ultrasonic treatment power is 200-500W, and the ultrasonic treatment time is 6-12h.

9. The method for preparing a supported heat-resistant additive according to claim 2, characterized in that: In step S3, the solvent thermal reaction temperature is 160-200° C., and the reaction time is 12-24 hours.

10. Use of the supported heat-resistant additive in silicone rubber as claimed in claim 1, wherein the amount of the heat-resistant additive is 1-5% by mass.

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