High-temperature-resistant silica gel composite material and preparation method thereof

Abstract

The application discloses a high-temperature-resistant silica gel composite material and a preparation method thereof, and belongs to the technical field of high polymer materials. In view of the problems that existing silica gel is easy to be thermally degraded and brittle and has poor flame-retardant performance above 300 DEG C, the application uses methyl vinyl silicone rubber as a matrix, introduces specific structure organic flame retardant and epoxy modified nano cerium dioxide. The two are in-situ chemically bonded through epoxy groups and phenolic hydroxyl groups to construct a synergistic protection network, which significantly improves the dispersibility of the filler and prevents high-temperature migration. The material has excellent mechanical property retention rate at 350 DEG C extreme high temperature, and the flame-retardant grade reaches UL-94 V-0 level. By forming a dense Ce-P-O-C ceramicized carbon layer, oxygen and heat are effectively isolated, the technical problems that the silica gel is easy to crack and easy to burn in an extreme heat environment are solved, and the material is suitable for the fields of aerospace and electronic packaging.

Description

Technical Field

[0001] This invention belongs to the field of polymer materials technology, specifically relating to a high-temperature resistant silicone composite material and its preparation method. Background Technology

[0002] Due to its unique Si-O-Si main chain structure, silicone rubber possesses excellent resistance to high and low temperatures, electrical insulation, and chemical stability, making it widely used in aerospace, automotive, electronics, and high-end kitchenware industries. Particularly in applications such as aero-engine sealing and high-power electronic device packaging, silicone composite materials not only need to serve as sealing or insulating media but also must maintain long-term physical and mechanical properties under extreme thermal environments.

[0003] However, existing silicone composite materials often undergo thermal rearrangement degradation when exposed to sustained high temperatures above 300°C, leading to hardening, brittleness, and even cracking. Traditional improvement methods often involve adding large amounts of inorganic fillers (such as silica and alumina), but this often sacrifices the material's processing performance and resilience, and offers limited improvement in oxidation resistance at extreme temperatures.

[0004] Furthermore, silicone rubber itself is a flammable material, easily igniting and releasing a large amount of heat under high temperatures or open flame conditions. In the aerospace and high-end electronic packaging fields, in addition to requiring materials with extremely high heat aging resistance, there are also stringent requirements for the flame retardant properties of the materials. Traditional flame retardants (such as aluminum hydroxide, halogenated flame retardants, etc.) are added in large quantities, which not only severely deteriorates the mechanical properties of silicone rubber but also compromises its high-temperature stability. Therefore, developing a silicone composite material that can maintain excellent mechanical properties at temperatures above 300°C while also possessing excellent flame retardant properties is a pressing technical challenge that needs to be solved in this field. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of existing technologies and provide a high-temperature resistant silicone composite material and its preparation method. This invention improves two raw materials in the high-temperature resistant system by introducing a specific organic flame retardant and epoxy-modified nano-cerium dioxide, constructing a synergistic protective network within the silicone matrix. This not only significantly improves the high-temperature stability of the material but also endows it with excellent flame-retardant properties.

[0006] The objective of this invention can be achieved through the following technical solutions: A high-temperature resistant silicone composite material, comprising the following raw materials by weight: Methyl vinyl silicone rubber: 100 parts; Fumed silica: 30-45 parts; Structure control agent: 3-6 parts; Organic flame retardant: 8-15 parts; Epoxy-modified nano-cerium dioxide: 3-8 parts; Hydrogen-containing silicone oil: 1.5-3.0 parts; Platinum catalyst: 0.05-0.15 parts; Inhibitor: 0.01-0.05 parts.

[0007] Furthermore, the organic flame retardant is prepared by the following steps: Step A1: Add zinc acetate to deionized water with stirring, heat to 78-82℃, then add 50wt% phytic acid, stir and reflux at a constant temperature for 4-6 hours. After the reaction is complete, cool to room temperature to obtain crude zinc phytate. After washing and drying, obtain zinc phytate. Step A2: Add zinc phytate to anhydrous ethanol and stir for 30 min. Then add 3,4-dihydroxybenzaldehyde and p-phenylenediamine. Heat to 78-82℃ and reflux for 2-3 h. Then add 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide and stir for 10-12 h. After standing for 12 h to precipitate, filter. After washing and drying the precipitate, obtain the organic flame retardant. The reaction process of p-phenylenediamine, 3,4-dihydroxybenzaldehyde (1), and 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (2) is as follows: .

[0008] Furthermore, the ratio of deionized water, zinc acetate, and 50wt% phytic acid used in step A1 is 150mL:10.5-11.0g:13.5-14.0g.

[0009] Further, the ratio of anhydrous ethanol, zinc phytate, 3,4-dihydroxybenzaldehyde, p-phenylenediamine, and 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide in step A2 is 100mL:2.8-3.2g:2.0-2.2g:0.80-0.84g:3.2-3.4g.

[0010] Furthermore, the epoxy-modified nano-cerium dioxide is prepared by the following steps: Nano-cerium dioxide was ultrasonically dispersed in a mixed solvent of anhydrous ethanol and deionized water. Silane coupling agent KH-560 was added, and the mixture was heated to 60-70℃ and mechanically stirred for 4-6 hours. After the reaction, the mixture was centrifuged, the precipitate was washed three times with anhydrous ethanol, vacuum dried at 80℃ for 12 hours, and then ground through a 400-mesh sieve to obtain epoxy-modified nano-cerium dioxide.

[0011] Furthermore, the ratio of the amount of nano-cerium dioxide, anhydrous ethanol, deionized water, and silane coupling agent KH-560 is 10g:100mL:10mL:1.2-1.8g.

[0012] As a further aspect of the present invention, the preparation method of the above-mentioned high-temperature resistant silicone composite material includes the following steps: (1) Premixing: Weigh the above raw materials according to the mass fraction, add methyl vinyl silicone rubber to the kneader, heat to 60-80℃, add fumed silica and structure control agent in batches, and knead for 2-3 hours. (2) High-temperature devolatilization: After completion, the kneader is turned on with vacuum, the temperature is raised to 150-160℃, the vacuum degree is maintained above -0.09MPa, devolatilization is carried out for 1.5 hours, and the material is discharged when the temperature is lowered to below 60℃ to obtain the base material; (3) Functional modification: Transfer the base material into a two-roll mill, add organic flame retardant and epoxy-modified nano-cerium dioxide in sequence, and repeat the thin pass 10-15 times. (4) Addition of vulcanization system: Add hydrogen-containing silicone oil, platinum catalyst and inhibitor to it, mix evenly and adjust to roll gap of 5mm for sheeting. (5) Molding and vulcanization: A flat vulcanizing machine is used for the first stage of vulcanization at a temperature of 160-170℃, a pressure of 10-15MPa, and a time of 10min; then it is placed in an oven for the second stage of vulcanization at a temperature of 200℃ and a time of 2-4 hours. After completion, it is naturally cooled to room temperature to obtain a high-temperature resistant silicone composite material.

[0013] The beneficial effects of this invention are: This invention provides a high-temperature resistant silicone composite material and its preparation method. Its core innovation lies in the introduction of a self-made core-shell hybrid organic flame retardant and epoxy-modified nano-cerium dioxide to construct a multi-dimensional synergistic protective network within the silicone matrix, achieving a dual breakthrough in both mechanical and flame-retardant properties under extreme high-temperature environments. Specific beneficial effects are as follows: (1) A stable inorganic-organic hybrid flame retardant system was constructed, which significantly improved the stability of the components.

[0014] The self-made organic flame retardant of this invention is not a simple stacking of components, but rather utilizes the strong coordination between the phenolic hydroxyl groups in 3,4-dihydroxybenzaldehyde and the metal ions on the surface of zinc phytate. This allows the phosphorus and nitrogen-containing Schiff base components to be in situ coated onto the surface of zinc phytate, forming a ZnPA@PAPDO hybrid structure with zinc phytate as the core and modified DOPO as the shell. This core-shell structure effectively solves the problem of easy aggregation of zinc phytate and improves its compatibility with the silicone rubber matrix using the organic shell layer. As can be seen from the data in Table 2, the high-temperature mass loss rate of Example 8 is only 4.2%, far lower than the 18.6% of Comparative Example 1 (using ordinary DOPO). This strongly demonstrates that the hybrid structure can significantly inhibit the migration and volatilization of flame retardant components at a high temperature of 350°C.

[0015] (2) Through in-situ chemical bonding at the interface, the filler’s “microscopic anchoring” and uniform dispersion were achieved.

[0016] The epoxy groups on the surface of epoxy-modified nano-cerium dioxide undergo ring-opening crosslinking reactions with the abundant phenolic hydroxyl groups in the shell of the organic flame retardant during vulcanization. This in-situ chemical bonding firmly "anchors" the hybrid flame retardant to the cerium dioxide surface, constructing a continuous protective network. As shown in Table 2, the initial tensile strength of Example 8 reached 8.2 MPa, significantly better than the 6.2 MPa of Comparative Example 2 (using unmodified cerium dioxide), indicating that this interfacial reinforcement greatly improves the dispersibility of the filler in the matrix and enhances the physical and mechanical properties.

[0017] (3) It achieves deep synergy between free radical capture and "double-layer barrier" mechanism, which greatly enhances heat aging resistance.

[0018] To address the issue of silica gel's susceptibility to thermal rearrangement degradation above 350℃, this invention achieves a superposition of multiple protective mechanisms: on the one hand, the variable valence state of cerium dioxide (Ce... 3+ / Ce 4+ The phenolic hydroxyl groups in the organic flame retardant synergistically capture free radicals generated by thermal degradation. On the other hand, the four elements P, N, Zn, and Ce catalyze the in-situ carbonization of the silica matrix at high temperatures, forming a dense and robust Ce-POC ceramic carbon layer. This carbon layer acts as a physical barrier, significantly inhibiting the erosion of the silicon-oxygen backbone by oxygen and heat. Table 2 shows that after aging at 350℃ for 72 hours, Example 8 maintained a tensile strength retention rate of up to 86.5%, with a hardness change of only +3 degrees, while Comparative Example 3 (traditional aluminum hydroxide system) was severely embrittled and broke easily, fully verifying the generational advantage of the system of this invention under extreme thermal environments.

[0019] (4) Gas-solid dual-phase flame retardant synergy gives the material excellent fire safety performance.

[0020] This invention, while improving heat resistance, unexpectedly achieved excellent flame retardant effects. The DOPO groups in the shell of the organic flame retardant release phosphorus-containing free radicals upon heating, exerting a gas-phase quenching effect; while the cerium dioxide in the core synergistically promotes the formation of a ceramicized char layer, which provides solid-phase barrier properties. Table 2 shows that the flame retardant ratings of Examples 7-9 all reached UL-94 V-0, with the highest limiting oxygen index (LOI) reaching 35.8%. In contrast, Comparative Example 4 (lacking the zinc phytate structure) had an LOI reduced to 29.5% and a flame retardant rating of only V-1, further confirming the core role of zinc phytate in catalytic char formation and improving flame retardant efficiency.

[0021] In summary, this invention solves the technical problems of silicone composite materials being easily degraded and flammable at extreme high temperatures, making them highly valuable for applications in demanding fields such as aerospace and electronic packaging. Detailed Implementation

[0022] 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. Meanwhile, unless otherwise specified, the raw materials, reagents, or devices used in the following embodiments can be obtained from conventional commercial channels. The specifications and manufacturer information of the raw materials used below are shown in Table 1: Table 1. Specifications and Manufacturer Information of Experimental Raw Materials

[0023] Example 1: Preparation of organic flame retardants: Step A1: Add 150 mL of deionized water to reactor A with stirring, then add 10.5 g of zinc acetate with stirring. Heat reactor A to 78 °C with stirring, then add 13.5 g of 50 wt% phytic acid. Stir and reflux at a constant temperature for 4 h. After the reaction is complete, cool to room temperature to obtain crude zinc phytate. Wash the crude zinc phytate three times with deionized water, and then vacuum dry at 100 °C for 12 h to obtain zinc phytate. Step A2: Add 100 mL of anhydrous ethanol to reactor B, then add 2.8 g of zinc phytate while stirring, stir for 30 min, then add 2.0 g of 3,4-dihydroxybenzaldehyde and 0.80 g of p-phenylenediamine. Heat reactor B to 78 °C, stir and reflux for 2 h, then add 3.2 g of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide to reactor B while stirring, continue stirring for 10 h, let stand to precipitate for 12 h, filter, wash the precipitate three times with deionized water, and dry under vacuum at 60 °C for 12 h to obtain the organic flame retardant.

[0024] Example 2 Preparation of organic flame retardants: Step A1: Add 150 mL of deionized water to reactor C with stirring, then add 10.8 g of zinc acetate with stirring. Heat reactor C to 80 °C with stirring, then add 13.8 g of 50 wt% phytic acid. Stir and reflux at a constant temperature for 5 h. After the reaction is complete, cool to room temperature to obtain crude zinc phytate. Wash the crude zinc phytate three times with deionized water, and then vacuum dry at 100 °C for 12 h to obtain zinc phytate. Step A2: Add 100 mL of anhydrous ethanol to reactor D, then add 3.0 g of zinc phytate while stirring, stir for 30 min, then add 2.1 g of 3,4-dihydroxybenzaldehyde and 0.82 g of p-phenylenediamine. Heat reactor D to 80 °C, stir and reflux for 2.5 h, then add 3.3 g of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide to reactor D while stirring, continue stirring for 11 h, let stand to precipitate for 12 h, filter, wash the precipitate three times with deionized water, and dry under vacuum at 60 °C for 12 h to obtain the organic flame retardant.

[0025] Example 3 Preparation of organic flame retardants: Step A1: Add 150 mL of deionized water to reactor E with stirring, then add 11.0 g of zinc acetate with stirring. Heat reactor E to 82°C with stirring, then add 14.0 g of 50 wt% phytic acid. Stir and reflux at a constant temperature for 6 hours. After the reaction is complete, cool to room temperature to obtain crude zinc phytate. Wash the crude zinc phytate three times with deionized water, and then dry it under vacuum at 100°C for 12 hours to obtain zinc phytate. Step A2: Add 100 mL of anhydrous ethanol to reactor F, then add 3.2 g of zinc phytate while stirring, stir for 30 min, then add 2.2 g of 3,4-dihydroxybenzaldehyde and 0.84 g of p-phenylenediamine. Heat reactor F to 82 °C, stir and reflux for 3 h, then add 3.4 g of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide to reactor F while stirring, continue stirring for 12 h, let stand to precipitate for 12 h, filter, wash the precipitate three times with deionized water, and dry under vacuum at 60 °C for 12 h to obtain the organic flame retardant.

[0026] Example 4 Preparation of epoxy-modified nano-cerium dioxide: 10g of nano-cerium dioxide was ultrasonically dispersed in a mixed solvent of 100mL anhydrous ethanol and 10mL deionized water. 1.2g of silane coupling agent KH-560 was added to the mixture, and the temperature was raised to 65℃. The mixture was mechanically stirred for 5h. After the reaction was completed, the mixture was centrifuged, and the precipitate was washed three times with anhydrous ethanol. The precipitate was then vacuum dried at 80℃ for 12h and ground through a 400-mesh sieve to obtain epoxy-modified nano-cerium dioxide.

[0027] Example 5 Preparation of epoxy-modified nano-cerium dioxide: 10g of nano-cerium dioxide was ultrasonically dispersed in a mixed solvent of 100mL anhydrous ethanol and 10mL deionized water. 1.5g of silane coupling agent KH-560 was added to the mixture, and the temperature was raised to 65℃. The mixture was mechanically stirred for 5h. After the reaction was completed, the mixture was centrifuged, and the precipitate was washed three times with anhydrous ethanol. The precipitate was then vacuum dried at 80℃ for 12h and ground through a 400-mesh sieve to obtain epoxy-modified nano-cerium dioxide.

[0028] Example 6 Preparation of epoxy-modified nano-cerium dioxide: 10g of nano-cerium dioxide was ultrasonically dispersed in a mixed solvent of 100mL anhydrous ethanol and 10mL deionized water. 1.8g of silane coupling agent KH-560 was added to the mixture, and the temperature was raised to 65℃. The mixture was mechanically stirred for 5h. After the reaction was completed, the mixture was centrifuged, and the precipitate was washed three times with anhydrous ethanol. The precipitate was then vacuum dried at 80℃ for 12h and ground through a 400-mesh sieve to obtain epoxy-modified nano-cerium dioxide.

[0029] Example 7 Preparation of high-temperature resistant silicone composite materials: First, the high-temperature resistant silicone composite material, by weight, includes the following raw materials: Methyl vinyl silicone rubber: 100 parts; Fumed silica: 30 parts; Structure control agent: 3 parts; Organic flame retardant prepared in Example 1: 8 parts; Epoxy-modified nano-cerium dioxide prepared in Example 4: 3 parts; Hydrogen-containing silicone oil: 1.5 parts; Platinum catalyst: 0.05 parts; Inhibitor: 0.01 parts.

[0030] Then, the preparation method of the high-temperature resistant silicone composite material includes the following steps: (1) Premixing: Weigh the above raw materials according to the mass fraction, add methyl vinyl silicone rubber to the kneader, heat to 60°C, add fumed silica and structure control agent in batches, and knead for 2 hours. (2) High-temperature devolatification: After completion, the kneader is turned on with vacuum, the temperature is raised to 150℃, the vacuum degree is maintained above -0.09MPa, and the devolatification is carried out for 1.5 hours to remove volatile components. The material is then discharged at a temperature below 60℃ to obtain the base material. (3) Functional modification: The base material is transferred into a two-roll mill, and the organic flame retardant prepared in Example 1 and the epoxy-modified nano-cerium dioxide prepared in Example 4 are added to it in sequence. The mixture is repeatedly passed through a thin mill 10 times to ensure that the filler is evenly dispersed and to promote the pre-reaction of the interface. (4) Addition of vulcanization system: Add hydrogen-containing silicone oil, platinum catalyst and inhibitor to it, mix evenly and adjust to roll gap of 5mm for sheeting. (5) Molding and vulcanization: A flat vulcanizing machine is used for the first stage of vulcanization at a temperature of 160℃, a pressure of 10MPa, and a time of 10min; then it is placed in an oven for the second stage of vulcanization at a temperature of 200℃ and a time of 2 hours. After completion, it is naturally cooled to room temperature to obtain a high-temperature resistant silicone composite material.

[0031] Example 8 Preparation of high-temperature resistant silicone composite materials: First, the high-temperature resistant silicone composite material, by weight, includes the following raw materials: Methyl vinyl silicone rubber: 100 parts; Fumed silica: 42 parts; Structure control agent: 5 parts; Organic flame retardant prepared in Example 2: 14.5 parts; Epoxy-modified nano-cerium dioxide prepared in Example 5: 6.5 parts; Hydrogen-containing silicone oil: 2.0 parts; Platinum catalyst: 0.1 parts; Inhibitor: 0.03 parts.

[0032] Then, the preparation method of the high-temperature resistant silicone composite material includes the following steps: (1) Premixing: Weigh the above raw materials according to the mass fraction, add methyl vinyl silicone rubber to the kneader, heat to 75°C, add fumed silica and structure control agent in batches, and knead for 3 hours. (2) High-temperature devolatification: After completion, the kneader is turned on with vacuum, the temperature is raised to 155℃, the vacuum degree is maintained above -0.09MPa, and devolatification is carried out for 1.5 hours to remove volatile components. The material is then discharged at a temperature below 60℃ to obtain the base material. (3) Functional modification: The base material is transferred into a two-roll mill, and the organic flame retardant prepared in Example 2 and the epoxy-modified nano-cerium dioxide prepared in Example 5 are added to it in sequence. The mixture is repeatedly passed through a thin mill 15 times to ensure that the filler is evenly dispersed and to promote the pre-reaction of the interface. (4) Addition of vulcanization system: Add hydrogen-containing silicone oil, platinum catalyst and inhibitor to it, mix evenly and adjust to roll gap of 5mm for sheeting. (5) Molding and vulcanization: A flat vulcanizing machine is used for the first stage of vulcanization at a temperature of 165℃, a pressure of 12MPa, and a time of 10min; then it is placed in an oven for the second stage of vulcanization at a temperature of 200℃ and a time of 4 hours. After completion, it is naturally cooled to room temperature to obtain a high-temperature resistant silicone composite material.

[0033] Example 9 Preparation of high-temperature resistant silicone composite materials: First, the high-temperature resistant silicone composite material, by weight, includes the following raw materials: Methyl vinyl silicone rubber: 100 parts; Fumed silica: 45 parts; Structure control agent: 6 parts; Organic flame retardant prepared in Example 3: 15 parts; Epoxy-modified nano-cerium dioxide prepared in Example 6: 8 parts; Hydrogen-containing silicone oil: 3.0 parts; Platinum catalyst: 0.15 parts; Inhibitor: 0.05 parts.

[0034] Then, the preparation method of the high-temperature resistant silicone composite material includes the following steps: (1) Premixing: Weigh the above raw materials according to the mass fraction, add methyl vinyl silicone rubber to the kneader, heat to 80°C, add fumed silica and structure control agent in batches, and knead for 3 hours. (2) High-temperature devolatation: After completion, the kneader is turned on with vacuum, the temperature is raised to 160℃, the vacuum degree is maintained above -0.09MPa, and the devolatation is carried out for 1.5 hours to remove volatile components. The material is then discharged at a temperature below 60℃ to obtain the base material. (3) Functional modification: The base material is transferred into a two-roll mill, and the organic flame retardant prepared in Example 3 and the epoxy-modified nano-cerium dioxide prepared in Example 6 are added to it in sequence. The mixture is repeatedly passed through a thin mill 15 times to ensure that the filler is evenly dispersed and to promote the pre-reaction of the interface. (4) Addition of vulcanization system: Add hydrogen-containing silicone oil, platinum catalyst and inhibitor to it, mix evenly and adjust to roll gap of 5mm for sheeting. (5) Molding and vulcanization: A flat vulcanizing machine is used for the first stage of vulcanization at a temperature of 170℃, a pressure of 15MPa, and a time of 10min; then it is placed in an oven for the second stage of vulcanization at a temperature of 200℃ and a time of 4 hours. After completion, it is naturally cooled to room temperature to obtain a high-temperature resistant silicone composite material.

[0035] Comparative Example 1 The basic formulation and preparation process are exactly the same as in Example 8. The only difference is that the "organic flame retardant prepared in Example 2" in Example 8 is replaced in equal amounts with commercially available ordinary DOPO (9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide), and finally a high-temperature resistant silicone composite material is obtained.

[0036] Comparative Example 2 The basic formula and preparation process are exactly the same as in Example 8. The only difference is that the "epoxy-modified nano-cerium dioxide prepared in Example 5" in Example 8 is replaced with "ordinary nano-cerium dioxide that has not been modified by KH-560" in equal amounts, and the high-temperature resistant silicone composite material is finally obtained.

[0037] Comparative Example 3 The basic formula and preparation process are exactly the same as in Example 8. The only difference is that the "organic flame retardant" and "epoxy modified nano-cerium dioxide" in Example 8 are completely removed and replaced with an equal total weight (21 parts) of the traditional flame retardant and heat-resistant agent "aluminum hydroxide (ATH)", and finally a high-temperature resistant silicone composite material is obtained.

[0038] Comparative Example 4 The basic formulation and preparation process are exactly the same as in Example 8. The only difference is that the organic flame retardant used in the preparation process is that step A1 (without adding zinc phytate) is removed. Instead, 3,4-dihydroxybenzaldehyde, p-phenylenediamine and DOPO are used to react and prepare an intermediate without zinc and polyphosphate structure, which finally yields a high-temperature resistant silicone composite material.

[0039] Test Example 1 The performance of the high-temperature resistant silicone composite materials prepared in Examples 7-9 and Comparative Examples 1-4 was tested. The test process is as follows, and the test results are shown in Table 2: (1) Tensile strength and elongation at break: According to GB / T 528 standard, the vulcanized silicone sheet was cut into dumbbell-shaped specimens and tested at room temperature using a universal testing machine at a tensile speed of 500 mm / min.

[0040] (2) Hardness: In accordance with GB / T 531.1 standard, stack silicone sheets to a thickness greater than 6mm, use a Shore A hardness tester to test, and read the value after stabilization.

[0041] (3) High-temperature aging test: The standard dumbbell-shaped sample was suspended in a high-temperature forced-air aging test chamber at 350℃, with air circulation maintained, and removed after 72 hours of continuous aging. After being placed in a standard environment for 24 hours, its tensile strength, elongation at break and hardness were tested again, and the performance retention rate and hardness change value were calculated.

[0042] (4) Flame retardant performance test: According to GB / T 2408 standard, the sample is cut into standard strips of 125mm×13mm×3.2mm, and UL-94 vertical burning test is performed using a vertical burning tester. The afterflame time and dripping situation are recorded to evaluate the flame retardant level.

[0043] (5) Limiting oxygen index (LOI) test: According to GB / T 2406.2 standard, the sample is cut into 150mm×10mm×4mm, and the minimum oxygen concentration required to maintain the combustion of the material is tested using an oxygen index tester.

[0044] (6) High-temperature mass loss rate: Weigh the vulcanized silicone sheet (recorded as M1), place it in a 350℃ high-temperature aging chamber for 72 hours, remove it, cool it, and weigh it again (recorded as M2). Mass loss rate = (M1-M2) / M1×100%. This indicator directly reflects whether the flame retardant has volatilized and whether the silicone main chain has degraded.

[0045] Table 2 Test Results

[0046] Analysis of the data in Table 2: 1. Overall comparison of the examples and comparative examples: Examples 7-9 exhibited excellent mechanical properties before aging, and after aging at an extreme high temperature of 350℃ for 72 hours, the tensile strength and elongation at break retained more than 75%, with minimal change in hardness (≤5 degrees), and all achieved UL-94 V-0 flame retardant rating. Among them, Example 8, as the optimal formulation, had the highest mechanical property retention rate after aging (strength retention rate 86.5%, elongation retention rate 82.3%), with a mass loss rate of only 4.2%, demonstrating the best overall performance.

[0047] 2. Comparative Example 1 Analysis (Chemical Bonding and Anti-Volatilization Effect): Comparative Example 1 used ordinary DOPO. Due to the lack of groups that react with modified cerium dioxide, DOPO volatilized significantly at 350℃ (mass loss rate as high as 18.6%), leading to flame retardant loss and a drop in UL-94 rating to V-2. Simultaneously, the silicone matrix, deprived of flame retardant protection, underwent severe thermal degradation, with a dramatic increase in hardness (+18 degrees) and a significant decrease in mechanical strength retention. This demonstrates the irreplaceable nature of the self-made organic flame retardant structure of this invention.

[0048] 3. Comparative Example 2 Analysis (Effect of Interface Anchoring): Comparative Example 2 used unmodified cerium dioxide, which could not undergo ring-opening crosslinking with the organic flame retardant. Due to filler agglomeration and poor interfacial bonding, its initial tensile strength (6.2 MPa) was significantly lower than that of Example 8. At high temperatures, due to the failure to form a tight microscopic synergistic network, the free radical capture efficiency decreased, and the performance retention rate after aging was only about 40%.

[0049] 4. Comparative Example 3 Analysis (Limitations of Traditional Technology): Comparative Example 3 used conventional aluminum hydroxide, which begins to dehydrate and decompose above 200℃. Under extreme testing at 350℃ for 72 hours, the aluminum hydroxide completely failed and destroyed the silica gel network, leading to severe embrittlement of the material (strength retention rate of only 12.5%, breaking easily upon bending), a mass loss rate as high as 28.5%, completely rendering it unusable and unable to pass the UL-94 test. This fully demonstrates the revolutionary advantage of the system of this invention at extreme high temperatures.

[0050] 5. Comparative Example 4 Analysis (Role of Ceramization into Carbon): Comparative Example 4 removed the zinc phytate structure. Although it still possessed certain flame retardant and antioxidant capabilities, due to the lack of catalytic action from Zn and polyphosphate structures, it could not form a dense and robust Ce-POC ceramized carbon layer at high temperatures. Therefore, its high-temperature mass loss rate (9.8%) was higher than that of Example 8, its heat insulation and oxygen barrier effects were weakened, resulting in a decrease in mechanical retention rate after aging to approximately 60%, and the LOI index also dropped to 29.5%. This verifies the core catalytic role of zinc phytate in the in-situ ceramization process.

[0051] It should be noted that, in this document, terms such as “comprising,” “including,” or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus.

[0052] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A high-temperature resistant silicone composite material, characterized in that, By weight, it includes the following ingredients: Methyl vinyl silicone rubber: 100 parts; Fumed silica: 30-45 parts; Structure control agent: 3-6 parts; Organic flame retardant: 8-15 parts; Epoxy-modified nano-cerium dioxide: 3-8 parts; Hydrogen-containing silicone oil: 1.5-3.0 parts; Platinum catalyst: 0.05-0.15 parts; Inhibitor: 0.01-0.05 parts.

2. The high-temperature resistant silicone composite material according to claim 1, characterized in that, The organic flame retardant is prepared by the following steps: Step A1: Add zinc acetate to deionized water with stirring, heat to 78-82℃, then add 50wt% phytic acid, stir and reflux at a constant temperature for 4-6 hours. After the reaction is complete, cool to room temperature to obtain crude zinc phytate. After washing and drying, obtain zinc phytate. Step A2: Add zinc phytate to anhydrous ethanol and stir for 30 min. Then add 3,4-dihydroxybenzaldehyde and p-phenylenediamine. Heat to 78-82℃ and reflux for 2-3 h. Then add 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide and stir for 10-12 h. After standing for 12 h to precipitate, filter. After washing and drying the precipitate, obtain the organic flame retardant.

3. The high-temperature resistant silicone composite material according to claim 2, characterized in that, The ratio of deionized water, zinc acetate, and 50wt% phytic acid used in step A1 is 150mL:10.5-11.0g:13.5-14.0g.

4. The high-temperature resistant silicone composite material according to claim 2, characterized in that, The ratio of anhydrous ethanol, zinc phytate, 3,4-dihydroxybenzaldehyde, p-phenylenediamine, and 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide in step A2 is 100mL:2.8-3.2g:2.0-2.2g:0.80-0.84g:3.2-3.4g.

5. The high-temperature resistant silicone composite material according to claim 1, characterized in that, The epoxy-modified nano-cerium dioxide is prepared by the following steps: Nano-cerium dioxide was ultrasonically dispersed in a mixed solvent of anhydrous ethanol and deionized water. Silane coupling agent KH-560 was added, and the mixture was heated to 60-70℃ and mechanically stirred for 4-6 hours. After the reaction, the mixture was centrifuged, the precipitate was washed three times with anhydrous ethanol, vacuum dried at 80℃ for 12 hours, and then ground through a 400-mesh sieve to obtain epoxy-modified nano-cerium dioxide.

6. The high-temperature resistant silicone composite material according to claim 5, characterized in that, The ratio of nano-cerium dioxide, anhydrous ethanol, deionized water, and silane coupling agent KH-560 is 10g:100mL:10mL:1.2-1.8g.

7. A method for preparing a high-temperature resistant silicone composite material according to any one of claims 1-6, characterized in that, Includes the following steps: (1) Premixing: Weigh the above raw materials according to the mass fraction, add methyl vinyl silicone rubber to the kneader, heat to 60-80℃, add fumed silica and structure control agent in batches, and knead for 2-3 hours. (2) High-temperature devolatilization: After completion, the kneader is turned on with vacuum, the temperature is raised to 150-160℃, the vacuum degree is maintained above -0.09MPa, devolatilization is carried out for 1.5 hours, and the material is discharged when the temperature is lowered to below 60℃ to obtain the base material; (3) Functional modification: Transfer the base material into a two-roll mill and add organic flame retardant and epoxy-modified nano-cerium dioxide in sequence, and repeat the thin pass 10-15 times. (4) Addition of vulcanization system: Add hydrogen-containing silicone oil, platinum catalyst and inhibitor to it, mix evenly and adjust to roll gap of 5mm for sheeting. (5) Molding and vulcanization: A flat vulcanizing machine is used for the first stage of vulcanization at a temperature of 160-170℃, a pressure of 10-15MPa, and a time of 10min; then it is placed in an oven for the second stage of vulcanization at a temperature of 200℃ and a time of 2-4 hours. After completion, it is naturally cooled to room temperature to obtain a high-temperature resistant silicone composite material.

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