A ketonized halloysite nanotube, its preparation method and application

Abstract

The present invention relates to the technical field of the preparation of silicone rubber materials, and particularly relates to a ketonized halloysite nanotube and its preparation method and application. The preparation method includes: dissolving levulinic acid in N,N'-dimethylformamide, and then adding an acidic reagent to adjust the pH to 2.5-3.5 to obtain a mixed solution; adding halloysite nanotubes to the mixed solution, and under acidic conditions, carrying out an esterification reaction between levulinic acid and halloysite nanotubes to obtain ketonized halloysite nanotubes; then using the ketonized halloysite nanotubes to prepare a ketonized halloysite nanotube silicone rubber composite material, and the composite material is made of the following raw materials in parts by weight: 100 parts of a silicone rubber matrix, 30-80 parts of a reinforcing agent, 2-4 parts of a vulcanizing agent, and 10-80 parts of ketonized halloysite nanotubes. The present invention not only overcomes the problem that halloysite nanotubes are difficult to be uniformly dispersed in the silicone rubber matrix, but also significantly improves the flame retardancy and mechanical properties of the silicone rubber.

Description

Technical Field

[0001] The present invention relates to the technical field of silicone rubber material preparation, and particularly relates to a ketonated halloysite nanotube, a preparation method thereof, and an application thereof. Background Art

[0002] Silicone rubber, as a polymer material with a Si-O bond as the main chain, exhibits excellent thermal stability, radiation resistance, weather resistance, high and low temperature resistance, as well as good elasticity, physiological inertness, and aging performance due to its unique chemical structure. These excellent properties have enabled silicone rubber to be widely used in many fields such as wire and cable, conveyor belt, air duct, seal, household appliances, ships, and automobiles. However, despite the many advantages of silicone rubber, its low oxygen index and poor self-extinguishing property limit its use in some occasions with strict requirements for flame retardancy. In a high-temperature environment, silicone rubber is prone to burning and releasing toxic and harmful gases, posing a potential threat to human health and environmental safety. Therefore, how to provide an effective method to improve the flame retardancy of silicone rubber is of great significance for expanding its application range, ensuring the safety of human life and property, and promoting environmental sustainable development.

[0003] In recent years, nanomaterials have shown great potential in the field of material modification due to their unique physical and chemical properties. Among them, halloysite nanotubes, as a natural nano-tubular clay mineral, are non-toxic, low-cost, and have good biocompatibility. Their unique tubular structure and high specific surface area have attracted extensive attention in the field of flame retardancy. However, despite the many advantages of halloysite nanotubes, the problem of uniform dispersion of halloysite nanotubes in silicone rubber composites prepared by existing technologies remains a major challenge, which greatly limits the effective application of halloysite nanotubes in the flame retardant modification of silicone rubber, and further hinders the further improvement of the flame retardancy of silicone rubber composites. Summary of the Invention

[0004] Aiming at the deficiencies of the existing technology, the present invention provides a ketonated halloysite nanotube, a preparation method thereof, and an application thereof. The present invention uses levulinic acid and halloysite nanotubes as raw materials, and carries out an esterification reaction under the catalysis of concentrated sulfuric acid with a mass fraction of 98% to prepare a ketonated halloysite nanotube; a keto group is introduced onto the halloysite nanotube through the esterification reaction, and the ketonated halloysite nanotube is used as a modifier to modify silicone rubber to obtain a ketonated halloysite nanotube silicone rubber composite material. After introducing a keto group onto the halloysite nanotube, the present invention not only effectively overcomes the problem of difficult uniform dispersion of halloysite nanotubes in silicone rubber, but also significantly improves the flame retardancy and mechanical properties of silicone rubber, thereby realizing the optimization of the comprehensive performance of silicone rubber composites.

[0005] To achieve the above object, the present invention adopts the following technical solutions:

[0006] The first object of the present invention is to provide a preparation method of ketonated halloysite nanotubes, comprising the following steps:

[0007] Dissolve levulinic acid in N,N'-dimethylformamide, and then add an acidic reagent to adjust the pH to 2.5 - 3.5 to obtain a mixed solution;

[0008] Add halloysite nanotubes to the mixed solution, and under acidic conditions, carry out an esterification reaction between levulinic acid and halloysite nanotubes to obtain ketonated halloysite nanotubes.

[0009] Among them, levulinic acid, also known as 4-oxopentanoic acid, is the most easily obtained and stably existing substance among the substances containing both a ketone group and a carboxyl group at present, and it is soluble in N,N'-dimethylformamide and can fully react with halloysite nanotubes.

[0010] Preferably, use anhydrous ethanol to wash the obtained ketonated halloysite nanotubes multiple times to remove residual impurities.

[0011] Preferably, the conditions for the drying treatment are: drying in a vacuum drying oven at 100°C for 6h - 10h.

[0012] Preferably, the dosage ratio of levulinic acid, N,N'-dimethylformamide to halloysite nanotubes is 6g - 9g: 400mL - 500mL: 40g - 50g.

[0013] Preferably, the catalyst is concentrated hydrochloric acid or concentrated sulfuric acid with a mass fraction of 98%.

[0014] Preferably, the temperature of the esterification reaction is 100°C - 120°C, and the time is 1.5h - 3.5h.

[0015] The second object of the present invention is to provide the ketonated halloysite nanotubes prepared by the above preparation method.

[0016] The third object of the present invention is to provide the application of the above ketonated halloysite nanotubes in the preparation of a ketonated halloysite nanotube silicone rubber composite material, and the ketonated halloysite nanotube silicone rubber composite material is made of the following raw materials in parts by weight: 100 parts of a silicone rubber matrix, 30 parts - 80 parts of a reinforcing agent, 2 parts - 4 parts of a vulcanizing agent, and 10 parts - 80 parts of ketonated halloysite nanotubes.

[0017] Preferably, the reinforcing agent is selected from one or more of silica, carbon black, carbon nanotubes or graphene.

[0018] Preferably, the vulcanizing agent is bis(2,5-dimethyl-2,5-di(t-butylperoxy)hexane).

[0019] Preferably, the silicone rubber matrix is selected from methyl vinyl silicone rubber, methyl silicone rubber, methyl vinyl phenyl silicone rubber, nitrile silicone rubber or fluorosilicone rubber.

[0020] Preferably, the ketone-functionalized halloysite nanotube silicone rubber composite material is prepared according to the following steps:

[0021] A reinforcing agent, ketone-functionalized halloysite nanotubes and a vulcanizing agent are sequentially added to the silicone rubber matrix, and after being subjected to mixing and vulcanization treatments in sequence, a ketone-functionalized halloysite nanotube silicone rubber composite material is obtained.

[0022] Preferably, the temperature of the mixing treatment is 40°C to 70°C, and the mixing is carried out until the silicone rubber matrix, the reinforcing agent, the vulcanizing agent and the ketone-functionalized halloysite nanotubes are uniformly mixed and no bubbles flow out.

[0023] Preferably, the conditions of the vulcanization treatment are: at 150°C to 170°C, applying a pressure of 10 MPa to 20 MPa, and keeping the temperature for 15 min to 30 min.

[0024] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0025] 1. The present invention provides a preparation method of ketone-functionalized halloysite nanotubes. After levulinic acid is dissolved in N,N'-dimethylformamide, concentrated sulfuric acid with a mass fraction of 98% is added to obtain a mixed solution. Subsequently, halloysite nanotubes are added to the mixed solution for an esterification reaction to obtain ketone-functionalized halloysite nanotubes;

[0026] Among them, levulinic acid is a bifunctional organic acid, and its molecular structure contains both a ketone group and a carboxyl group. Concentrated sulfuric acid with a mass fraction of 98% is used as a strong acid catalyst. While adjusting the pH of the mixed solution, it enhances the reaction activity of levulinic acid; under acidic conditions, the carboxyl group of levulinic acid reacts with the hydroxyl groups on the surface of halloysite nanotubes to carry out an esterification reaction, and a ketone group is successfully introduced onto the surface of halloysite nanotubes, thereby preparing ketone-functionalized halloysite nanotubes.

[0027] 2. The present invention provides an application of ketone-functionalized halloysite nanotubes in the preparation of ketone-functionalized halloysite nanotube silicone rubber composite materials. The silicone rubber is modified with ketone-functionalized halloysite nanotubes to obtain a ketone-functionalized halloysite nanotube silicone rubber composite material. It not only effectively overcomes the problem that halloysite nanotubes are difficult to be uniformly dispersed in silicone rubber, but also significantly improves the flame retardancy and mechanical properties of silicone rubber.

[0028] Among them, the ketonylated halloysite nanotubes have a unique surface chemical structure. The introduced keto functional groups not only enhance the interfacial bonding force between the halloysite nanotubes and the silicone rubber matrix, but also greatly promote the uniform dispersion of the halloysite nanotubes in the silicone rubber. At the same time, due to the principle of like dissolves like and the good interaction between the keto functional groups and the silicone rubber molecular chains, the ketonylated halloysite nanotubes exhibit excellent dispersion in the silicone rubber matrix and can generate strong interactions with the silicone rubber molecular chains, bringing more excellent comprehensive properties to the composite material. Brief Description of the Drawings

[0029] Figure 1 It is the scanning electron microscope image of Comparative Example 4 in the present invention;

[0030] Figure 2 It is the scanning electron microscope image of Comparative Example 5 in the present invention. Detailed Embodiments

[0031] Next, the technical solutions of the present invention will be clearly and completely described in conjunction with the data in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts fall within the protection scope of the present invention.

[0032] It should be noted that the professional terms used in the present invention are only for the purpose of describing specific embodiments and are not intended to limit the protection scope of the present invention. Unless otherwise specifically stated, various raw materials, reagents, instruments and equipment used in the following embodiments of the present invention can be obtained through market purchase or prepared by existing methods. Among them, the methyl vinyl silicone rubbers with grades 110-0 and 110-1 are both purchased from Guangdong Dongjue Silicone Rubber Co., Ltd.; the VN2 precipitated silica with the grade is purchased from Evonik Degussa GmbH;

[0033] In the prior art, although silicone rubber has many excellent properties, its low oxygen index and poor self-extinguishing property limit its application in occasions with high flame retardancy requirements. Especially its characteristic of being easy to burn and release toxic gases at high temperatures poses a threat to human health and the environment. In addition, as a potential flame retardant modifier, halloysite nanotubes fail to fully exert their efficacy due to their difficult uniform dispersion in silicone rubber.

[0034] To address these defects, the present invention provides a preparation method for ketonylated halloysite nanotubes, which includes the following steps: dissolving levulinic acid in N,N'-dimethylformamide, and then adding an acidic reagent to adjust the pH to 2.5-3.5 to obtain a mixed solution; adding halloysite nanotubes to the mixed solution, and under acidic conditions, carrying out an esterification reaction between levulinic acid and the halloysite nanotubes to obtain ketonylated halloysite nanotubes.

[0035] The present invention adopts the ketonation modification technology. By surface-modifying halloysite nanotubes, ketone groups with good compatibility with silicone rubber are introduced to improve the dispersion performance of halloysite nanotubes in silicone rubber. Subsequently, levulinic acid is introduced onto the surface of halloysite nanotubes to form ketonated halloysite nanotubes. Then, by mixing the ketonated halloysite nanotubes with a reinforcing agent and a vulcanizing agent, and then mixing and vulcanizing with a silicone rubber matrix, a ketonated halloysite nanotube silicone rubber composite material is prepared. The present invention not only effectively overcomes the dispersion problem of nanotubes in silicone rubber, but also significantly improves the flame retardancy of silicone rubber and broadens the application field of silicone rubber.

[0036] The following uses examples to further explain and illustrate the technical solution of the present invention, specifically as follows:

[0037] Example 1

[0038] A preparation method of ketonated halloysite nanotubes includes the following steps:

[0039] S1. After cleaning and drying the surface of halloysite nanotubes to remove surface moisture, 6.3 g of levulinic acid is weighed and dissolved in 400 mL of N,N'-dimethylformamide. Then, 1 mL of concentrated sulfuric acid with a mass fraction of 98% is added dropwise, and the pH is measured to be 3. The mixture is stirred at 110 °C for 15 min to obtain a mixed solution;

[0040] S2. 50 g of halloysite nanotubes are slowly added to the mixed solution, and stirring is continued for 2 h to ensure full reaction. After the reaction is completed, the solid product is separated by filtration and washed repeatedly with absolute ethanol to remove residual impurities;

[0041] S3. The washed product is placed in a vacuum drying oven at 100 °C and dried for 8 h to obtain ketonated halloysite nanotubes.

[0042] Example 2

[0043] A preparation method of ketonated halloysite nanotubes includes the following steps:

[0044] S1. After cleaning and drying the surface of halloysite nanotubes to remove surface moisture, 7.56 g of levulinic acid is weighed and dissolved in 400 mL of N,N'-dimethylformamide. Then, 1 mL of concentrated sulfuric acid with a mass fraction of 98% is added dropwise, and the pH is measured to be 3. At 110 °C, the mixture is stirred for 20 min to obtain a mixed solution;

[0045] S2. 60 g of halloysite nanotubes are slowly added to the mixed solution, and stirring is continued for 2 h to ensure full reaction. After the reaction is completed, the solid product is separated by filtration and washed repeatedly with absolute ethanol to remove residual impurities;

[0046] S3. Place the washed product in a vacuum drying oven at 100 °C and dry it for 9 h to obtain ketonated halloysite nanotubes.

[0047] Example 3

[0048] A preparation method of ketonated halloysite nanotubes, comprising the following steps:

[0049] S1. After cleaning the surface of the halloysite nanotubes and drying them to remove the surface moisture, weigh 6.93 g of levulinic acid and dissolve it in 500 mL of N,N'-dimethylformamide. Then, add 1 mL of concentrated sulfuric acid with a mass fraction of 98%, measure the pH to be 2.5, and stir at 110 °C for 20 min to obtain a mixed solution.

[0050] S2. Slowly add 55 g of halloysite nanotubes to the mixed solution and continue stirring for 2 h to ensure complete reaction. After the reaction is completed, separate the solid product by filtration and wash it with anhydrous ethanol multiple times to remove residual impurities.

[0051] S3. Place the washed product in a vacuum drying oven at 100 °C and dry it for 8 h to obtain ketonated halloysite nanotubes.

[0052] Application Example 1

[0053] Apply the ketonated halloysite nanotubes prepared in Example 1 to the preparation of a ketonated halloysite nanotube silicone rubber composite material:

[0054] S1. Weigh 100 g of methyl vinyl silicone rubber 110-0, 50 g of white carbon black, 80 g of ketonated halloysite nanotubes, and 3 g of bis(2,5-dimethyl-2,5-di(t-butylperoxy)hexane). Mix the white carbon black and the ketonated halloysite nanotubes and stir evenly.

[0055] S2. Place the methyl vinyl silicone rubber on the roller of a mixer, set the roller temperature to 60 °C, and sequentially add the evenly stirred white carbon black, ketonated halloysite nanotubes, and vulcanizing agent. Knead repeatedly until the methyl vinyl silicone rubber is evenly mixed and no bubbles flow out, then take it out and let it stand, and cool it to room temperature to obtain a kneaded rubber.

[0056] S3. Put the kneaded rubber into a mold and vulcanize it in a flat vulcanizer at 160 °C and 15 Mpa for 20 min to obtain a ketonated halloysite nanotube silicone rubber composite material.

[0057] Application Example 2

[0058] Apply the ketonated halloysite nanotubes prepared in Example 2 to the preparation of a ketonated halloysite nanotube silicone rubber composite material:

[0059] S1. Weigh 100 g of methyl vinyl silicone rubber 110-1, 50 g of silica, 40 g of ketonated halloysite nanotubes and 3 g of bis(2,5-dimethyl-2,5-di(tert-butylperoxy)hexane). Mix the silica and the ketonated halloysite nanotubes and stir evenly.

[0060] S2. Place the methyl vinyl silicone rubber on the rollers of a mixer. Set the roller temperature to 60 °C. Add the evenly stirred silica, ketonated halloysite nanotubes and vulcanizing agent in sequence. Knead repeatedly until the methyl vinyl silicone rubber is evenly mixed and no bubbles flow out. Then take it out and let it stand, and cool it to room temperature to obtain a kneaded rubber.

[0061] S3. Put the kneaded rubber into a mold and vulcanize it in a flat vulcanizer at 160 °C and 15 Mpa for 20 min to obtain a ketonated halloysite nanotube silicone rubber composite material.

[0062] Application Example 3

[0063] Apply the ketonated halloysite nanotubes prepared in Example 3 to the preparation of a ketonated halloysite nanotube silicone rubber composite material:

[0064] S1. Weigh 100 g of methyl vinyl silicone rubber 110-0, 50 g of silica, 10 g of ketonated halloysite nanotubes and 3 g of bis(2,5-dimethyl-2,5-di(tert-butylperoxy)hexane). Mix the silica and the ketonated halloysite nanotubes and stir evenly.

[0065] S2. Place the methyl vinyl silicone rubber on the rollers of a mixer. Set the roller temperature to 60 °C. Add the evenly stirred silica, ketonated halloysite nanotubes and vulcanizing agent in sequence. Knead repeatedly until the methyl vinyl silicone rubber is evenly mixed and no bubbles flow out. Then take it out and let it stand, and cool it to room temperature to obtain a kneaded rubber.

[0066] S3. Put the kneaded rubber into a mold and vulcanize it in a flat vulcanizer at 160 °C and 15 Mpa for 20 min to obtain a ketonated halloysite nanotube silicone rubber composite material.

[0067] Application Example 4

[0068] Apply the ketonated halloysite nanotubes prepared in Example 2 to the preparation of a ketonated halloysite nanotube silicone rubber composite material. The preparation steps are the same as those in Application Example 2, except that in S1, the dosage of silica is 30 g and the dosage of bis(2,5-dimethyl-2,5-di(tert-butylperoxy)hexane) is 2 g. The steps are as follows:

[0069] S1. Weigh 100 g of methyl vinyl silicone rubber 110-0, 30 g of silica, 40 g of ketonated halloysite nanotubes and 2 g of bis(2,5-dimethyl-2,5-di(tert-butylperoxy)hexane). Mix the silica and the ketonated halloysite nanotubes and stir evenly.

[0070] S2. Place the methyl vinyl silicone rubber on the rollers of a mixer, set the roller temperature to 60 °C, and sequentially add the uniformly stirred silica, ketonated halloysite nanotubes, and vulcanizing agent. Knead repeatedly until the methyl vinyl silicone rubber is uniformly mixed and no bubbles flow out, then take it out and let it stand, and cool it to room temperature to obtain a kneaded rubber;

[0071] S3. Put the kneaded rubber into a mold and vulcanize it in a flat vulcanizer at 160 °C and 15 Mpa for 20 min to obtain a ketonated halloysite nanotube silicone rubber composite material.

[0072] Application Example 5

[0073] Apply the ketonated halloysite nanotubes prepared in Example 2 to the preparation of a ketonated halloysite nanotube silicone rubber composite material. The preparation steps are the same as those in Application Example 2, except that in S1, the dosage of silica is 80 g and the dosage of bis(2,5-dimethyl-2,5-hexanediolato)platinum(IV) is 4 g. The steps are as follows:

[0074] S1. Weigh 100 g of methyl vinyl silicone rubber 110-0, 80 g of silica, 40 g of ketonated halloysite nanotubes, and 4 g of bis(2,5-dimethyl-2,5-hexanediolato)platinum(IV). Mix the silica and the ketonated halloysite nanotubes and stir evenly;

[0075] S2. Place the methyl vinyl silicone rubber on the rollers of a mixer, set the roller temperature to 60 °C, and sequentially add the uniformly stirred silica, ketonated halloysite nanotubes, and vulcanizing agent. Knead repeatedly until the methyl vinyl silicone rubber is uniformly mixed and no bubbles flow out, then take it out and let it stand, and cool it to room temperature to obtain a kneaded rubber;

[0076] S3. Put the kneaded rubber into a mold and vulcanize it in a flat vulcanizer at 160 °C and 15 Mpa for 20 min to obtain a ketonated halloysite nanotube silicone rubber composite material.

[0077] Comparative Example 1

[0078] A preparation method of a halloysite nanotube silicone rubber composite material is the same as the preparation steps in Application Example 2, except that the ketonated halloysite nanotubes in S1 are replaced with an equal amount of halloysite nanotubes. The steps are as follows:

[0079] S1. Weigh 100 g of methyl vinyl silicone rubber 110-0, 50 g of silica, 40 g of halloysite nanotubes, and 3 g of bis(2,5-dimethyl-2,5-hexanediolato)platinum(IV). Mix the silica and the halloysite nanotubes and stir evenly;

[0080] S2, placing the methyl vinyl silicone rubber on the roller of the mixer, setting the roller temperature to 60°C, adding the uniformly stirred white carbon black, halloysite nanotubes, and vulcanizing agent in sequence, repeatedly mixing until the methyl vinyl silicone rubber is uniformly mixed and no bubbles flow out, taking it out and letting it stand, cooling it to room temperature, and obtaining a mixed rubber;

[0081] S3. Put the mixed rubber into a mold and vulcanize it in a flat vulcanizer at 160° C. and 15 MPa for 20 min to obtain a halloysite nanotube silicone rubber composite material.

[0082] Comparative Example 2

[0083] A method for preparing a silicone rubber composite material, which has the same preparation steps as those of Application Example 2, except that the ketonized halloysite nanotubes in S1 are replaced with an equal amount of aluminum hydroxide, comprises the following steps:

[0084] S1. Weigh 100g of methyl vinyl silicone rubber 110-0, 40g of aluminum hydroxide and 3g of dipentadienyl, and mix them thoroughly;

[0085] S2, placing the methyl vinyl silicone rubber on the roller of the mixer, setting the roller temperature to 60°C, adding aluminum hydroxide and a vulcanizing agent in sequence, mixing repeatedly until the methyl vinyl silicone rubber is evenly mixed and no bubbles flow out, taking it out and letting it stand, cooling it to room temperature, and obtaining a mixed rubber;

[0086] S3. Put the mixed rubber into a mold and vulcanize it in a flat vulcanizer at 160°C and 15 MPa for 20 minutes to obtain a silicone rubber composite material.

[0087] Comparative Example 3

[0088] A method for preparing a ketonized halloysite nanotube silicone rubber composite material, which has the same preparation steps as those of Application Example 3, except that the amount of the ketonized halloysite nanotubes in S1 is replaced from 40 g to 90 g, comprising the following steps:

[0089] S1. Preparation of ketonized halloysite nanotube silicone rubber composite material: weigh 100 g of methyl vinyl silicone rubber 110-0, 50 g of white carbon black, 90 g of ketonized halloysite nanotubes and 3 g of bis(25-pentylene)sulfonate, mix the white carbon black and the ketonized halloysite nanotubes and stir evenly;

[0090] S2, placing the methyl vinyl silicone rubber on the roller of the mixer, setting the roller temperature to 60°C, adding the uniformly stirred white carbon black, ketonized halloysite nanotubes, and vulcanizing agent in sequence, repeatedly mixing until the methyl vinyl silicone rubber is uniformly mixed and no bubbles flow out, taking it out and letting it stand, cooling it to room temperature, and obtaining a mixed rubber;

[0091] S3. Place the mixed rubber into a mold and cure it in a flat vulcanizer at 160 °C and 15 Mpa for 20 min to obtain a ketonylated halloysite nanotube silicone rubber composite material.

[0092] Comparative Example 4

[0093] A preparation method of a ketonylated halloysite nanotube silicone rubber composite material is the same as the preparation steps of Application Example 2, except that in S1, no silica is added, and it includes the following steps:

[0094] S1. Weigh 100 g of methyl vinyl silicone rubber 110-0, 40 g of ketonylated halloysite nanotubes, and 3 g of bis(2,5-dimethyl-2,5-di(tert-butylperoxy)hexane);

[0095] S2. Place the methyl vinyl silicone rubber on the rollers of a mixer, set the roller temperature to 60 °C, add the ketonylated halloysite nanotubes and the vulcanizing agent in sequence, and repeatedly mix until the methyl vinyl silicone rubber is evenly mixed and no bubbles flow out, then take it out and let it stand, and cool it to room temperature to obtain a mixed rubber;

[0096] S3. Place the mixed rubber into a mold and cure it in a flat vulcanizer at 160 °C and 15 Mpa for 20 min to obtain a ketonylated halloysite nanotube silicone rubber composite material.

[0097] Comparative Example 5

[0098] A preparation method of a halloysite nanotube silicone rubber composite material is the same as the preparation steps of Comparative Example 1, except that in S1, no silica is added, and it includes the following steps:

[0099] S1. Weigh 100 g of methyl vinyl silicone rubber 110-0, 40 g of halloysite nanotubes, and 3 g of the vulcanizing agent bis(2,5-dimethyl-2,5-di(tert-butylperoxy)hexane);

[0100] S2. Place the methyl vinyl silicone rubber on the rollers of a mixer, set the roller temperature to 60 °C, add the halloysite nanotubes and the vulcanizing agent in sequence, and repeatedly mix until the methyl vinyl silicone rubber is evenly mixed and no bubbles flow out, then take it out and let it stand, and cool it to room temperature to obtain a mixed rubber;

[0101] S3. Place the mixed rubber into a mold and cure it in a flat vulcanizer at 160 °C and 15 Mpa for 20 min to obtain a halloysite nanotube silicone rubber composite material.

[0102] Since the ketonylated halloysite nanotube silicone rubber composite material and the halloysite nanotube silicone rubber composite material added with silica will affect the scanning electron microscope results, Comparative Example 4 and Comparative Example 5 are given for easy observation of the morphology.

[0103] Performance Test

[0104] a. Vertical Burning Test:

[0105] Test method: Vertical combustion test was carried out in accordance with GB / T 2408-2008;

[0106] Vertical combustion tests were performed on the ketonated halloysite nanotube silicone rubber composites prepared in Application Examples 1 to 3, the halloysite nanotube silicone rubber composite of Comparative Example 1, and the silicone rubber composite of Comparative Example 2. The test results are shown in Tables 1, 2, 3, 4, and 5.

[0107] Table 1 is the vertical combustion test value table of the ketonated halloysite nanotube silicone rubber composite in Application Example 1

[0108]

[0109] Table 2 is the vertical combustion test value table of the ketonated halloysite nanotube silicone rubber composite in Application Example 2

[0110]

[0111]

[0112] Table 3 is the vertical combustion test value table of the ketonated halloysite nanotube silicone rubber composite in Application Example 3

[0113]

[0114] From the comparative analysis of Tables 1, 2, and 3, it was observed that the ketonated halloysite nanotube silicone rubber composites prepared in Application Example 1, Application Example 2, and Application Example 3 showed high consistency in flame retardancy performance and all reached the excellent standard of V-0 level, indicating that the esterification reaction technology effectively promoted the uniform dispersion of halloysite nanotubes in the silicone rubber matrix, thereby greatly improving the flame retardancy efficiency of the ketonated halloysite nanotube silicone rubber composites;

[0115] Further comparison of the data in Table 1 and Table 2 found that even when the addition amount of ketonated halloysite nanotubes in Application Example 2 was halved, the flame retardant effect of its ketonated halloysite nanotube silicone rubber composite remained stable without significant decrease;

[0116] Comparing Tables 1, 2, and 3, although the flame retardancy performance of the ketonated halloysite nanotube silicone rubber composite prepared in Application Example 3 was still relatively uniform, it was lower than that of the ketonated halloysite nanotube silicone rubber composites prepared in Application Example 1 and Application Example 2, and the second afterglow time of some samples was longer, indicating that when the content of ketonated halloysite nanotubes was too low, its enhancement effect on the flame retardancy performance of the composite would be significantly weakened.

[0117] Table 4 is the numerical table of the vertical combustion test of the halloysite nanotube silicone rubber composite in Comparative Example 1

[0118]

[0119] It can be seen from Table 4 that the flame retardant performance of the halloysite nanotube silicone rubber composite in Comparative Example 1 is unstable. Some samples reached the V-1 level, indicating that the halloysite nanotubes without esterification reaction have poor dispersion in silicone rubber, resulting in a decrease in the flame retardant performance of the composite material. By comparing Table 2 and Table 4, it is found that the flame retardant performance of the ketone-functionalized halloysite nanotube silicone rubber composite in Application Example 2 is more excellent, and all samples reached the V-0 level, showing better flame retardant effect and stability, which indicates that the esterification reaction can significantly improve the flame retardant performance of the halloysite nanotube silicone rubber composite material.

[0120] Table 5 is the numerical table of the vertical combustion test of the silicone rubber composite in Comparative Example 2

[0121]

[0122] It can be seen from Table 5 that the flame retardant performance of the silicone rubber composite in Comparative Example 2 is unevenly distributed and the flame retardant performance of the samples is relatively extreme; by comparing Table 2 and Table 5, it is found that the ketone-functionalized halloysite nanotube composite prepared in Application Example 2 can effectively improve the flame retardant performance of the samples.

[0123] b. Mechanical property test:

[0124] Test method: The tensile property is tested in accordance with GB / T 528-2009, the tear property is tested in accordance with GB / T529-2008, and the Shore A hardness is tested in accordance with GB / T 531.1—2008;

[0125] The mechanical properties of the ketone-functionalized halloysite nanotube silicone rubber composites prepared in Application Examples 1 to 3 and Comparative Example 3, the halloysite nanotube silicone rubber composite prepared in Comparative Example 1, and the silicone rubber composite prepared in Comparative Example 2 were detected, and the test results are shown in Table 6.

[0126] Table 6 is the data table of the mechanical property test results of the silicone rubber composites in Application Examples 1 to 3 and Comparative Examples 1 to 3

[0127] Sample Tensile strength (MPa) Tear strength (KN / m) Shore hardness (Shore / A) Application Example 1 9.64 14.78 72 Application Example 2 8.36 13.89 70 Application Example 3 6.14 10.98 68 Comparative Example 1 7.01 11.61 69 Comparative Example 2 6.97 11.56 68 Comparative Example 3 8.17 13.27 69

[0128] As shown in Table 6, with the increase in the content of ketonized halloysite nanotubes, the tensile strength, tear strength, and Shore hardness of the ketonized halloysite nanotube silicone rubber composites all show a trend of increasing first and then decreasing, indicating that increasing the addition amount of ketonized halloysite nanotubes can effectively improve the mechanical properties of the ketonized halloysite nanotube silicone rubber composites. However, when the addition amount of ketonized halloysite nanotubes exceeds 90 g, the mechanical properties of the silicone rubber composites decrease instead. This is because excessive ketonized halloysite nanotubes agglomerate in the silicone rubber matrix, resulting in a weakened interfacial bonding force between the silicone rubber matrix and the ketonized halloysite nanotubes, thereby reducing the mechanical properties of the ketonized halloysite nanotube silicone rubber composites.

[0129] In addition, the mechanical properties of the silicone rubber composites added with ketonized halloysite nanotubes are significantly better than those of the silicone rubber composites added with halloysite nanotubes and without halloysite nanotubes, indicating that ketonized halloysite nanotubes can better combine with the silicone rubber matrix, thereby improving the mechanical properties of the ketonized halloysite nanotube silicone rubber composites.

[0130] Figure 1 It is the scanning electron microscope result diagram of Comparative Example 4. Figure 2 It is the scanning electron microscope result of Comparative Example 5. Figure 1 The white particles in it represent ketonized halloysite nanotubes, while the black part is the methyl vinyl silicone rubber matrix. Observation Figure 1 finds that the ketonized halloysite nanotubes show a good dispersion state in the silicone rubber; while Figure 2 the white particles in it are halloysite nanotubes, and the methyl vinyl silicone rubber matrix is also represented in black. Observation Figure 2 finds that the dispersion state of halloysite nanotubes in the silicone rubber matrix is poor, and obvious agglomeration phenomena occur.

[0131] It should be noted that when the present invention involves numerical ranges, it should be understood that any value between the two endpoints of each numerical range and the two endpoints can be selected. Since the adopted step methods are the same as those in the embodiments, in order to prevent repetition, the present invention describes the preferred embodiments. Although the preferred embodiments of the present invention have been described, those skilled in the art can make additional changes and modifications to these embodiments once they know the basic creative concepts. Therefore, the appended claims are intended to be interpreted to include the preferred embodiments and all changes and modifications falling within the scope of the present invention.

[0132] Obviously, 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 equivalent technologies, the present invention also intends to include these modifications and variations.

Claims

1. A method for preparing ketonized halloysite nanotubes, characterized in that: The steps include: Dissolving levulinic acid in N,N'-dimethylformamide, and then adding an acidic reagent to adjust the pH to 2.5-3.5 to obtain a mixed solution; Adding halloysite nanotubes to the mixed solution, and reacting levulinic acid with the halloysite nanotubes for esterification under acidic conditions to obtain ketonized halloysite nanotubes; The usage ratio of levulinic acid, N,N'-dimethylformamide and halloysite nanotubes is 6g-9g:400mL-500mL:40g-50g; The temperature of the esterification reaction is 100°C to 120°C, and the time is 1.5h to 3.5h.

2. The method for preparing ketonized halloysite nanotubes according to claim 1, characterized in that: The acidic reagent is concentrated hydrochloric acid or concentrated sulfuric acid with a mass fraction of 98%.

3. A ketonized halloysite nanotube obtained by the preparation method according to any one of claims 1 to 2.

4. Use of the ketonized halloysite nanotubes according to claim 3 in preparing a ketonized halloysite nanotube silicone rubber composite material, characterized in that: The ketonized halloysite nanotube silicone rubber composite material is prepared from the following raw materials in parts by weight: 100 parts of silicone rubber matrix, 30 to 80 parts of reinforcing agent, 2 to 4 parts of vulcanizing agent and 10 to 80 parts of ketonized halloysite nanotube.

5. The use according to claim 4, characterized in that: The reinforcing agent is selected from one or more of white carbon black, carbon black, carbon nanotubes or graphene.

6. The use according to claim 4, characterized in that: The vulcanizing agent is di-25.

7. The use according to claim 4, characterized in that: The silicone rubber matrix is ​​selected from methyl vinyl silicone rubber, methyl silicone rubber, methyl vinyl phenyl silicone rubber, nitrile silicone rubber or fluorosilicone rubber.

8. The use according to claim 4, characterized in that: The keto-haloysite nanotube silicone rubber composite material was prepared according to the following steps: A reinforcing agent, ketonized halloysite nanotubes and a vulcanizing agent are sequentially added to a silicone rubber matrix, and after sequential mixing and vulcanization treatment, a ketonized halloysite nanotube silicone rubber composite material is obtained.

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