A temperature-resistant and ablation-resistant condensed silicone rubber composite material based on alkoxy hyperbranched silicone resin and a preparation method thereof

Abstract

The application discloses a kind of based on alkoxy hyperbranched organosilicon resin enhanced temperature-resistant and ablation-resistant condensation type silicone rubber composite material and preparation method thereof, belong to high polymer heat protection composite material technical field.The application uses alkoxy hyperbranched organosilicon resin as crosslinking agent, with end hydroxyl silicone rubber as matrix, with zirconium oxide, boron zinc acid salt, silicon carbide, chopped carbon fiber, magnesium hydroxide, aluminum hydroxide as filler system, after organic tin catalyst catalysis room temperature curing obtains temperature-resistant and ablation-resistant condensation type silicone rubber composite material.The application significantly improves the mechanical properties and high temperature resistance of the material through the crosslinking reinforcement effect of alkoxy hyperbranched organosilicon resin, while reducing the linear ablation rate and mass ablation rate of the material;The material can be applied to engine heat insulation, spacecraft heat protection, probe outer surface heat protection and other fields by virtue of excellent thermal performance, mechanical properties and heat insulation capacity.

Description

Technical Field

[0001] This invention belongs to the field of polymer thermal protection composite materials technology, specifically relating to a heat-resistant and ablation-resistant condensation-type silicone rubber composite material based on alkoxy hyperbranched organosilicon resin and its preparation method. Background Technology

[0002] With the iterative development of aerospace equipment such as high-speed aircraft and reusable space launch vehicles, thermal protection systems are placing increasingly stringent demands on sealing, bonding, and protective coating materials. In thermal insulation layers at reentry sites, engine jet stages, and interstage separation, materials must withstand temperatures of hundreds or even thousands of degrees Celsius, intense scouring from high-speed particle-laden airflow, and complex mechanical loads within extremely short timeframes. Simultaneously, to meet practical needs such as rapid on-site construction, structural weight reduction, and adaptation to irregularly shaped structural components, ideal protective materials should also possess characteristics such as room temperature curing, low density, good elastic recovery, and ease of large-area application.

[0003] Condensation-type room temperature vulcanizing (RTV) silicone rubber is a preferred substrate for thermal protective coatings and potting applications due to its rapid cross-linking and molding at room temperature, along with its outstanding electrical insulation, weather resistance, and flexibility. However, unmodified RTV silicone rubber typically has a long-term service temperature not exceeding 200°C. It rapidly degrades and loses weight at higher temperatures, and its low carbonization rate and porous carbon layer under ablation conditions prevent it from forming an effective thermal insulation and erosion-resistant barrier, making it difficult to directly meet the protection requirements of extreme high-temperature ablation conditions.

[0004] Currently, most ablation-resistant silicone rubber materials employ linear silicone resin modification or single inorganic filler reinforcement. While these methods can improve the material's heat resistance to some extent, significant shortcomings remain. To enhance the temperature resistance and ablation resistance of condensation-type RTV silicone rubber, existing technologies primarily focus on introducing inorganic ablation-resistant fillers or organic charring agents. Adding inorganic fillers such as mica powder, aluminosilicate fiber, and zirconium oxide, while improving the material's thermal residual rate and erosion resistance to some extent, often comes at the cost of material density, elasticity, and processing fluidity, which is particularly unfavorable for thermal protection applications requiring lightweight and wide-temperature-range elasticity. Introducing organic charring agents such as phenolic resin and boron phenolic resin can increase the high-temperature charring rate, but their compatibility with the silicone rubber matrix is ​​poor, leading to phase separation. Furthermore, large-scale additions cause a sharp increase in system viscosity, severely impacting the material's room-temperature vulcanization characteristics and processability. Therefore, existing modification methods consistently face a contradiction in achieving multiple application goals such as "ablation resistance, lightweight and high strength, and room-temperature operation," making it difficult to coordinate performance across different aspects.

[0005] Hyperbranched silicone resins, with their near-spherical three-dimensional topological structure, abundant terminal reactive functional groups, and excellent solubility and low viscosity, offer a new approach to solving the aforementioned problems. Introducing them into silicone rubber matrices can serve as multifunctional macromolecular crosslinking agents to construct dense three-dimensional networks, and can also improve filler distribution uniformity through nanoscale dispersion effects. Existing studies have shown that vinyl hyperbranched polysiloxanes or fluorinated hyperbranched silicone resins can significantly improve tensile strength, tear strength, and thermal stability in thermally vulcanized or addition-vulcanized silicone rubbers. However, research on condensation-type room-temperature vulcanized silicone rubber systems, which are most suitable for on-site construction, especially in areas requiring simultaneous ablation resistance, high-temperature resistance, and excellent room-temperature operability, remains very limited.

[0006] Patent CN114561103A discloses a condensation-type room temperature vulcanizing insulating silicone rubber and its preparation method. This technology reduces the thermal conductivity of the material and improves the settling stability of the filler by using low-density insulating fillers compounded with heat-resistant resins. However, the tackifier synthesis process of this type of material is complex, making it difficult to achieve low-cost, high-efficiency large-scale production. At the same time, its insulating filler types are relatively limited, without the introduction of more efficient insulating components such as aerogels and hollow ceramic microspheres. The thermal conductivity still has considerable room for optimization, and it is difficult to form a continuous and dense protective layer under continuous high-temperature ablation environment, resulting in limited ablation resistance.

[0007] Patent CN116179145A discloses a single-component condensation-type room-temperature vulcanizing silicone rubber resistant to high-temperature creep and its preparation method. This technology improves the creep resistance of silicone rubber under prolonged high-temperature loading by modifying nano-calcium carbonate with epoxy cyclohexyl cage-type polysilsesquioxane and using terminal alkoxymethylphenyl silicone oil plasticizer. However, this type of material is mainly designed for high-temperature creep resistance and mechanical stability, and does not construct an effective ablation-resistant structural system for extreme high-temperature ablation environments. At the same time, its filler system is mainly composed of high-filler nano-calcium carbonate, focusing on reinforcement and creep resistance. It is difficult to form a continuous and dense ceramic protective layer at high temperatures, and the structural stability of the material remains limited under continuous high-temperature flame erosion conditions, making it difficult to meet the requirements of ablation-resistant protection applications.

[0008] Patent CN118652661A discloses a single-component, low-hardness, thermally conductive condensation-type room-temperature vulcanizing silicone rubber and its preparation method. This technology uses a modified hydroxyl polydimethylsiloxane compounded with a chain extender to achieve high thermal conductivity and inhibit oil seepage when filled with 70-90 parts of thermally conductive filler. However, this type of material is mainly designed for low hardness, high thermal conductivity, and non-oil seepage properties, but its ablation resistance is insufficient, and it does not construct an effective ablation-resistant structural system for extreme high-temperature ablation environments. At the same time, its filler system is mainly composed of conventional thermally conductive powders, focusing on improving heat transfer efficiency. It is difficult to form a continuous and dense ceramic protective layer at high temperatures, and the material's structural stability remains limited under continuous high-temperature flame erosion conditions, making it difficult to meet the requirements of ablation-resistant protection applications.

[0009] In summary, the research indicates that developing a composite material that can improve both the mechanical properties of condensation-type room temperature vulcanizing silicone rubber and enhance its high-temperature ablation resistance has clear application value and industrial demand. Summary of the Invention

[0010] The first technical problem solved by this invention is to provide a method for preparing a high-temperature resistant and ablation-resistant condensation-type silicone rubber composite material reinforced with alkoxy hyperbranched silicone resin. This method uses alkoxy hyperbranched silicone resin as a crosslinking agent component to participate in the condensation crosslinking reaction of terminal hydroxyl silicone rubber. By increasing the crosslinking density of the material, a three-dimensional crosslinking network is formed inside the composite material, thereby improving the mechanical properties of the composite material. The second technical problem solved by this invention is to provide a high-temperature resistant and ablation-resistant condensation-type silicone rubber composite material reinforced with alkoxy hyperbranched silicone resin. This condensation-type room temperature vulcanizing silicone rubber composite material achieves improved mechanical properties, temperature resistance, and thermal insulation properties. The third technical problem solved by this invention is to provide an application of the high-temperature resistant and ablation-resistant condensation-type silicone rubber composite material reinforced with alkoxy hyperbranched silicone resin in the fields of engine thermal insulation, aircraft thermal protection, and probe outer surface thermal protection.

[0011] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows:

[0012] A heat-resistant and ablation-resistant condensation-type silicone rubber composite material based on alkoxy hyperbranched organosilicon resin is composed of the following components by weight: 100 parts of hydroxyl-terminated silicone rubber, 10-60 parts of alkoxy hyperbranched organosilicon resin, 1-10 parts of boron zincate, 1-10 parts of silicon carbide, 5-30 parts of chopped carbon fiber, 5-30 parts of zirconium oxide, 10-50 parts of magnesium hydroxide, 10-50 parts of aluminum hydroxide, and 0.1-2 parts of organotin catalyst.

[0013] Furthermore, the viscosity of the hydroxyl-terminated silicone rubber is 2000-50000 mPa·s, and the hydroxyl mass fraction is 0.02%-3%.

[0014] Furthermore, the alkoxy hyperbranched silicone resin has a viscosity of 100-1000 mPa·s and an alkoxy content of 3%-12%.

[0015] Furthermore, the zinc borate is selected from one or more of zinc borate 3,5-hydrate, zinc borate 7-hydrate, zinc borate 1-hydrate, and anhydrous zinc borate.

[0016] Furthermore, the organotin catalyst is selected from one or more of dibutyltin dilaurate, stannous octoate, dibutyltin diacetate, di(dodecyl sulfide)dibutyltin, and dioctyltin.

[0017] Furthermore, the preparation method of the alkoxy hyperbranched organosilicon resin-reinforced high-temperature resistant and ablation-resistant condensation-type silicone rubber composite material includes the following steps:

[0018] 1) Add alkoxy hyperbranched silicone resin to hydroxyl-terminated silicone rubber and mix thoroughly;

[0019] 2) Add zirconium oxide, zinc borate, silicon carbide, short-cut carbon fiber, magnesium hydroxide, and aluminum hydroxide filler, mix well, and then heat.

[0020] 3) After the system has cooled, add the organotin catalyst and mix.

[0021] 4) Apply the adhesive to the surface of the substrate or mold and cure it to obtain a temperature-resistant and ablation-resistant silicone rubber composite material.

[0022] Furthermore, in step 2), the heating temperature is 100-120℃ and the heating time is 1-1.5h.

[0023] Furthermore, in step 4), the curing temperature is 20-30℃ and the moisture curing time is 10-12h.

[0024] Furthermore, the application of the alkoxy hyperbranched organosilicon resin-reinforced high-temperature resistant and ablation-resistant condensation-type silicone rubber composite material in the field of polymer thermal protection composite materials technology.

[0025] Furthermore, this includes aircraft thermal protection structures, engine thermal insulation layers, detector outer surface thermal protection, and building high-temperature fireproof and heat-insulating coatings.

[0026] Compared with the prior art, the present invention has the following advantages:

[0027] (1) This invention utilizes alkoxy hyperbranched organosilicon resin to participate in the condensation crosslinking reaction of silicone rubber, forming a uniform and dense three-dimensional crosslinked network structure within the material, thereby improving the mechanical properties of the material. Simultaneously, in conjunction with a composite filler system composed of zirconium oxide, zinc borate, silicon carbide, chopped carbon fibers, magnesium hydroxide, and aluminum hydroxide, a synergistic ceramization reaction occurs between the fillers and between the fillers and the matrix under high-temperature flame erosion conditions, enabling the rapid formation of a continuous, dense, and stable ceramization protective layer. This protective layer effectively hinders heat transfer and oxygen diffusion, significantly reducing the linear ablation rate and mass ablation rate of the material, meeting the ablation protection requirements under extreme thermal environments.

[0028] (2) The alkoxy hyperbranched silicone resin used in this invention has a highly branched three-dimensional network structure and abundant alkoxy side groups, which can significantly improve the crosslinking density and thermal stability of silicone rubber as a crosslinking agent. At the same time, the resin itself has excellent heat resistance and can inhibit the degradation and backbiting of the polymer backbone at high temperatures, so that the composite material can maintain its structural integrity under continuous high temperature environment and significantly improve the long-term service temperature.

[0029] (3) This invention uses an organotin catalyst to catalyze the condensation reaction, which can be cured at room temperature without the need for heating or pressurization equipment. It is suitable for on-site construction and heat protection treatment of large-sized and complex-shaped parts. The curing process has low shrinkage, does not corrode the substrate, and the operating window is adjustable, which is convenient for industrial production and application. Attached Figure Description

[0030] Figure 1 This is a synthetic route diagram for the samples prepared in Examples 1-2 and the comparative examples of this application;

[0031] Figure 2 The figures show the tensile test results of the samples prepared in Examples 1-2 and the comparative examples of this application;

[0032] Figure 3 Comparative images of the samples prepared in Examples 1-2 and the comparative examples of this application, and the samples after butane spray gun ablation. Detailed Implementation

[0033] The present invention will be further illustrated below with reference to specific embodiments. These embodiments are implemented based on the technical solutions of the present invention, and it should be understood that these embodiments are only used to illustrate the present invention and are not intended to limit the scope of the present invention.

[0034] The hydroxyl-terminated 107 silicone rubber used in the following examples was purchased from Hubei Longsheng Sihai New Materials Co., Ltd.; alumina, zirconium oxide, silicon carbide, magnesium hydroxide, aluminum hydroxide, and zinc borate were purchased from Qingdao Zhongye New Materials Technology Co., Ltd.; and the organotin catalyst was purchased from Nanjing Wanqing Chemical Glass Instrument Co., Ltd.; and the chopped carbon fiber was purchased from Toray Industries, Inc., Japan.

[0035] The alkoxy hyperbranched organosilicon preparation method used in the following examples adopts Chinese invention patent with publication number CN118978701A: Example 1 of a low viscosity alkoxy-rich hyperbranched organosilicon resin and its preparation method and application.

[0036] Example 1

[0037] like Figure 1 As shown, this embodiment provides a method for preparing a high-temperature resistant and ablation-resistant condensation-type silicone rubber composite material reinforced with alkoxy hyperbranched organosilicon resin. The formula is as follows by mass: 100 parts of hydroxyl-terminated 107 silicone rubber (viscosity 20000 mPa·s, hydroxyl mass fraction 0.04%), 50 parts of alkoxy hyperbranched organosilicon (viscosity 100-1000 mPa·s, alkoxy content 5.48%), 20 parts of zirconium oxide (average particle size 2 μm), 4 parts of zinc borate 3,5-hydrate (average particle size 2 μm), 4 parts of silicon carbide (average particle size 5 μm), 10 parts of chopped carbon fiber (average particle size 0.5 mm), 30 parts of magnesium hydroxide (average particle size 2 μm), 30 parts of aluminum hydroxide (average particle size 2 μm), and 0.5 parts of dibutyltin dibutylsilicate.

[0038] Includes the following steps:

[0039] Alkoxy hyperbranched organosilicon was added to hydroxyl-terminated 107 silicone rubber and premixed at room temperature until homogeneous. Then zirconium oxide, zinc borate, silicon carbide, chopped carbon fibers, magnesium hydroxide, and aluminum hydroxide were added and mixed for 1 min at room temperature using a degassing machine. Then dibutyltin disilicate catalyst was added and mixing was continued for 2 min. The mixture was then uniformly coated into a mold and cured at room temperature for 12 h to obtain an alkoxy hyperbranched organosilicon resin-reinforced, heat-resistant, ablation-resistant condensation-type silicone rubber composite material.

[0040] Example 2

[0041] A method for preparing a high-temperature resistant and ablation-resistant condensation-type silicone rubber composite material reinforced with alkoxy hyperbranched organosilicon resin, wherein the formulation is as follows by mass parts: 100 parts of hydroxyl-terminated 107 silicone rubber (viscosity 50000 mPa·s, hydroxyl mass fraction 0.04%), 50 parts of alkoxy hyperbranched organosilicon (viscosity 100-1000 mPa·s, alkoxy content 5.48%), 30 parts of zirconium oxide (average particle size 2 μm), 4 parts of zinc borate 3,5 hydrated (average particle size 2 μm), 6 parts of silicon carbide (average particle size 5 μm), 15 parts of chopped carbon fiber (average particle size 0.5 mm), 30 parts of magnesium hydroxide (average particle size 2 μm), 30 parts of aluminum hydroxide (average particle size 2 μm), and 0.5 parts of dibutyltin dimethylsiloxane.

[0042] Includes the following steps:

[0043] Alkoxy hyperbranched organosilicon was added to hydroxyl-terminated 107 silicone rubber and premixed at room temperature until homogeneous. Then zirconium oxide, zinc borate, silicon carbide, chopped carbon fibers, magnesium hydroxide, and aluminum hydroxide were added and mixed for 1 min at room temperature using a degassing machine. Then dibutyltin disilicate catalyst was added and mixing was continued for 2 min. The mixture was then uniformly coated into a mold and cured at room temperature for 12 h to obtain an alkoxy hyperbranched organosilicon resin-reinforced, heat-resistant, ablation-resistant condensation-type silicone rubber composite material.

[0044] Comparative Example 1

[0045] The formula is as follows by weight: 100 parts of hydroxyl-terminated 107 silicone rubber (viscosity 50000 mPa·s, hydroxyl mass fraction 0.04%), 50 parts of tetraethyl orthosilicate (content 26.4%), 20 parts of zirconium oxide (average particle size 2 μm), 4 parts of zinc borate 3,5-hydrate (average particle size 2 μm), 4 parts of silicon carbide (average particle size 5 μm), 10 parts of chopped carbon fiber (average particle size 0.5 mm), 30 parts of magnesium hydroxide (average particle size 2 μm), 30 parts of aluminum hydroxide (average particle size 2 μm), and 0.5 parts of dibutyltin dibutylsilicate.

[0046] Includes the following steps:

[0047] Tetraethyl orthosilicate was added to hydroxyl-terminated 107 silicone rubber and premixed at room temperature until homogeneous. Then zirconium oxide, zinc borate, silicon carbide, chopped carbon fibers, magnesium hydroxide, and aluminum hydroxide were added and mixed for 1 min at room temperature using a degassing machine. Dibutyltin disilicate catalyst was then added and mixing continued for 2 min. The mixture was then evenly coated into a mold and cured at room temperature for 12 h to obtain the composite material.

[0048] The alkoxy-hyperbranched organosilicon resin-reinforced, heat-resistant, and ablation-resistant condensation-type silicone rubber composites prepared in Examples 1-2 and Comparative Example 1 were subjected to performance tests. The results are shown in Table 1 and... Figure 2-3 .

[0049] 1. Tensile strength test: The tensile strength of the rubber was tested using an Instron 5967 universal tensile testing machine;

[0050] 2. Thermogravimetric analysis test: Thermogravimetric analysis was performed using a STA449F3 thermogravimetric-differential scanning calorimetry analyzer (Netzche GmbH, Germany).

[0051] 3. Oxyacetylene ablation test: The oxyacetylene ablation test was conducted according to the GJB 323B-2018 standard.

[0052] Table 1. Performance tests of alkoxy-hyperbranched organosilicon resin-reinforced, heat-resistant, ablation-resistant condensation-type silicone rubber composites prepared in Examples 1-2 and Comparative Example 1.

[0053]

[0054] From Table 1 and Figure 2-3 It can be seen that the tensile strength of the alkoxy hyperbranched organosilicon resin-reinforced high-temperature ablation-resistant condensation-type silicone rubber composite material prepared by the present invention is significantly improved. The highest elongation at break in Example 2 reaches 4.41 MPa, which is a significant improvement over the tensile strength of Comparative Example 1. Although the elongation at break is lower than that of Comparative Example 1, the existing elongation performance can fully meet the engineering requirements of aerospace thermal protection components. Compared with Comparative Example 1, the linear ablation rate and mass ablation rate of Example 2 in the oxyacetylene ablation test are significantly reduced, and its ablation resistance is significantly improved. Compared with Comparative Example 1, the initial thermal decomposition temperature of Example 2 increases from 312.4℃ to 388.4℃, and the high-temperature thermal stability is significantly enhanced. At the same time, the linear ablation rate and mass ablation rate in the oxyacetylene ablation test are significantly reduced, proving that the material can form a stable and dense ceramic protective layer under high-temperature and high-speed particle erosion environment, and its ablation protection ability is significantly better than that of traditional small molecule silane crosslinked modification system.

[0055] With its excellent mechanical properties, high-temperature thermal stability, and low thermal ablation loss characteristics, this composite material can be widely used in the field of polymer thermal protection, including thermal protection structures for aircraft, thermal insulation layers for engines, thermal protection coatings for the outer surface of space probes, and high-temperature fireproof and heat-insulating coatings for buildings, as well as other high-temperature extreme working conditions.

[0056] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A heat-resistant and ablation-resistant condensation-type silicone rubber composite material reinforced with alkoxy hyperbranched organosilicon resin, characterized in that, It is composed of the following components in parts by weight: 100 parts of hydroxyl-terminated silicone rubber, 10-60 parts of alkoxy hyperbranched organosilicon resin, 1-10 parts of boron zincate, 1-10 parts of silicon carbide, 5-30 parts of chopped carbon fiber, 5-30 parts of zirconium oxide, 10-50 parts of magnesium hydroxide, 10-50 parts of aluminum hydroxide, and 0.1-2 parts of organotin catalyst.

2. The alkoxy-based hyperbranched organosilicon resin-reinforced high-temperature resistant and ablation-resistant condensation-type silicone rubber composite material according to claim 1, characterized in that: The hydroxyl-terminated silicone rubber has a viscosity of 2000-50000 mPa·s and a hydroxyl mass fraction of 0.02%-3%.

3. The alkoxy-based hyperbranched organosilicon resin-reinforced high-temperature resistant and ablation-resistant condensation-type silicone rubber composite material according to claim 1, characterized in that: The alkoxy hyperbranched silicone resin has a viscosity of 100-1000 mPa·s and an alkoxy content of 3%-12%.

4. The alkoxy-based hyperbranched organosilicon resin-reinforced high-temperature resistant and ablation-resistant condensation-type silicone rubber composite material according to claim 1, characterized in that: The zinc borate is selected from one or more of zinc borate 3, 5-hydrate, zinc borate 7-hydrate, zinc borate 1-hydrate, and anhydrous zinc borate.

5. The alkoxy-based hyperbranched organosilicon resin-reinforced high-temperature resistant and ablation-resistant condensation-type silicone rubber composite material according to claim 1, characterized in that: The organotin catalyst is selected from one or more of dibutyltin dilaurate, stannous octanoate, dibutyltin diacetate, di(dodecyl sulfide)dibutyltin, and dioctyltin.

6. The preparation method of the alkoxy-based hyperbranched organosilicon resin-reinforced high-temperature resistant and ablation-resistant condensation-type silicone rubber composite material according to any one of claims 1 to 5, characterized in that: Includes the following steps: 1) Add alkoxy hyperbranched silicone resin to hydroxyl-terminated silicone rubber and mix thoroughly; 2) Add zirconium oxide, zinc borate, silicon carbide, short-cut carbon fiber, magnesium hydroxide, and aluminum hydroxide filler, mix well, and then heat. 3) After the system has cooled, add the organotin catalyst and mix. 4) Apply the adhesive to the surface of the substrate or mold and cure it to obtain a temperature-resistant and ablation-resistant silicone rubber composite material.

7. The preparation method of the alkoxy-based hyperbranched organosilicon resin-reinforced high-temperature resistant and ablation-resistant condensation-type silicone rubber composite material according to claim 6, characterized in that: In step 2), the heating temperature is 100-120℃ and the heating time is 1-1.5h.

8. The preparation method of the alkoxy-based hyperbranched organosilicon resin-reinforced high-temperature resistant and ablation-resistant condensation-type silicone rubber composite material according to claim 6, characterized in that: In step 4), the curing temperature is 20-30℃ and the moisture curing time is 10-12h.

9. The application of the alkoxy hyperbranched organosilicon resin-reinforced high-temperature resistant and ablation-resistant condensation-type silicone rubber composite material according to any one of claims 1 to 5 in the field of polymer thermal protection composite materials technology.

10. The application according to claim 9, characterized in that: This includes thermal protection structures for aircraft, thermal insulation layers for engines, thermal protection for the outer surface of detectors, and high-temperature fireproof and heat-insulating coatings for buildings.

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