High-temperature-resistant silicone sealant

Abstract

The invention discloses a high-temperature-resistant silicone sealant which comprises the following raw materials: 10-100 parts of high-temperature-resistant silicon resin, 10-100 parts of alpha, omega-dihydroxy polydimethylsiloxane, 5-80 parts of a reinforcing agent, 1-20 parts of a cross-linking agent, 1-10 parts of a coupling agent, 1-10 parts of a catalyst, 1-10 parts of heat-resistant nanoparticles and 5-20 parts of an organosilicon polymer containing phenyl or large-volume side groups, the raw materials also comprise 0.5-5 parts of a heat-resistant reinforcing agent, wherein the heat-resistant reinforcing agent is zinc borate or polyborosiloxane. By using the heat-resistant nanoparticles with the cerium oxide and zirconium oxide core-shell structure, a more stable protective layer is formed at high temperature, the thermal oxidation resistance, creep resistance and high-temperature toughness of the sealant are improved, and by adding a small amount of zinc borate or polyborosiloxane heat-resistant enhancer in the formula, the heat resistance of the sealant is improved. Pores and cracks generated by decomposition of organic components are actively filled, so that self-healing protection is realized, and the long-term sealing integrity and ablation resistance of the sealant at an extreme temperature are improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of silicone sealant, in particular to a high-temperature-resistant silicone sealant. BACKGROUND

[0002] With the rapid development of aerospace, new energy vehicles, high-temperature chemical equipment and other fields, there is an urgent need for elastic sealing materials that can work stably in extreme high-temperature environments for a long time. Silicone sealant has become one of the preferred materials due to its excellent high and low temperature resistance, weather resistance and elasticity. Currently, the mainstream technical route to improve the temperature resistance of silicone sealant focuses on two aspects: one is to introduce rigid structures such as aromatic rings and metal hybrid structures into the molecular backbone to improve intrinsic heat resistance; the other is to add heat-resistant nano fillers such as silicon dioxide and aluminum oxide to build a physical heat barrier.

[0003] In the prior art, a high-temperature-resistant silicone sealant and its preparation method with publication number "CN120158268A" are as follows: 10-100 parts of high-temperature-resistant resin, 10-200 parts of alpha, omega-dihydroxy polydimethylsiloxane, 5-40 parts of reinforcing agent, 1-20 parts of crosslinking agent, 1-10 parts of coupling agent, 1-10 parts of catalyst, and 1-10 parts of heat-resistant nanoparticles. The high-temperature-resistant silicone resin includes a Si-O-Si backbone, a metal bond M, a biphenyl structure, and active alkoxy side groups. The molar proportion of the Si-O-Si backbone in the high-temperature-resistant silicone resin is 50-90%, the molar proportion of the metal bond M is 0.1-20%, the molar proportion of the biphenyl structure is 0.1-10%, and the molar proportion of the active alkoxy group is 0.1-10%. The high-temperature-resistant silicone sealant has excellent temperature resistance, durability, and ultraviolet resistance, and is particularly suitable for related fields such as new energy and aerospace that have higher performance requirements. Through specific high-temperature-resistant resin design and unique formula, linear growth and curing crosslinking of the silicone rubber backbone are achieved, thereby obtaining high heat resistance and good adhesion.

[0004] However, the prior art still has some shortcomings, such as:

[0005] 1. The high-temperature-resistant silicone sealant prepared by the above formula uses heat-resistant nanoparticles of boron oxide, cerium oxide, zirconium oxide, molybdenum oxide, tungsten oxide, titanium oxide, and iron oxide, or any combination thereof. The use of a single heat-resistant nanoparticle results in low heat oxidation resistance, creep resistance, and toughness at high temperatures of the sealant.

[0006] 2. Silicone sealant is mainly used for bonding and sealing of equipment in oil-resistant and high-temperature working environments, which will be in a high-temperature environment for a long time. The high-temperature-resistant silicone sealant prepared by the above formula will fail due to polymer decomposition if it is used in a high-temperature environment for a long time, and it cannot self-heal, thereby shortening the service life of the silicone sealant. SUMMARY

[0007] The purpose of this invention is to provide a high-temperature resistant silicone sealant to solve the problems mentioned in the background art.

[0008] To achieve the above objectives, the present invention provides the following technical solution:

[0009] A high-temperature resistant silicone sealant is prepared from raw materials comprising the following parts by weight:

[0010] 10-100 parts of high-temperature resistant silicone resin

[0011] 10-100 parts of α,ω-dihydroxypolydimethylsiloxane

[0012] 5-80 parts of reinforcing agent

[0013] 1-20 parts of crosslinking agent

[0014] 1-10 parts of coupling agent,

[0015] 1-10 parts of catalyst

[0016] 1-10 parts of heat-resistant nanoparticles

[0017] 5-20 parts of organosilicon polymers containing phenyl or bulky side groups.

[0018] Furthermore, the heat-resistant nanoparticles are preferably cerium oxide@zirconia core-shell structures. This core-shell structure uses cerium oxide as the core and zirconia as the shell. The cerium oxide core has excellent oxygen storage and release capabilities, which can effectively capture free radicals generated at high temperatures and inhibit matrix oxidation. The zirconia shell has high hardness, high toughness, and low thermal conductivity, which can provide a physical barrier and phase transformation toughening effect. The two are tightly combined through the core-shell structure, which solves the problem of easy aggregation and single function of single particles, and realizes the synergy of anti-oxidation and physical enhancement.

[0019] Furthermore, the raw materials also include 0.5-5 parts of a heat-resistant reinforcing agent, which is zinc borate or polyborosiloxane. This component acts as a "sacrificial" heat-resistant agent, which can melt or transform into a glassy / ceramic substance at ultra-high temperatures, actively sealing microcracks and pores caused by matrix decomposition, and providing ultimate protection for the material.

[0020] Furthermore, the organosilicon polymer containing phenyl or large-volume side groups is preferably methylphenyl silicone oil. The introduction of phenyl increases the spacing and free volume of the molecular chains, effectively reducing the movement resistance of polymer chain segments at high temperatures, thereby better maintaining elasticity after high temperature and thermal aging.

[0021] Furthermore, the preparation method of the cerium oxide@zirconia core-shell structure is as follows: cerium oxide nanoparticles are dispersed in a precursor solution containing a zirconium source (such as zirconium oxychloride). By precisely controlling the pH value, temperature, and concentration, zirconium oxide is epitaxially grown on the surface of each cerium oxide particle in a homogeneous precipitation manner, forming a complete and uniform shell layer. After washing, drying, and calcining at 500-800℃, a core-shell nanoparticle with good crystallinity is obtained. Before use, it is recommended to modify its surface with a silane coupling agent (such as KH-560) to improve its dispersibility in the organic phase.

[0022] Furthermore, the structural feature of the high-temperature resistant silicone resin lies in the introduction of dynamic covalent bonds into its molecular chain. A specific preferred structure is: (C2H5O)3-Si-(CH2)3-SS-(CH2)3-Si-(OC2H5)3. The (C2H5O)3Si- at ​​both ends of this structure are triethoxysilyl groups, which can participate in hydrolysis and condensation reactions to anchor the entire molecule into the silicone network. The -SS- in the middle is a disulfide bond, which, as a dynamic covalent bond, can undergo reversible breakage and exchange under heat or catalysis. The -(CH2)3- is a propyl chain, which acts as a flexible spacer group. When this structure is used as part of the high-temperature resistant silicone resin or as a separate crosslinking agent, it can introduce dynamic crosslinking points into the sealant network, giving the material stress relaxation and potential self-healing capabilities.

[0023] The reinforcing agent is one or more of fumed silica, precipitated silica, and calcium carbonate; the crosslinking agent is one or more of methyltrimethoxysilane, vinyltrimethoxysilane, and tetraethyl orthosilicate; the coupling agent is one or more of γ-aminopropyltriethoxysilane and γ-(2,3-epoxypropoxy)propyltrimethoxysilane; and the catalyst is one or a combination of two of tetrabutyl titanate and dibutyltin dilaurate.

[0024] The present invention also provides a method for preparing the high-temperature resistant silicone sealant, comprising the following steps:

[0025] S1. Pretreatment: Heat-resistant nanoparticles (cerium oxide@zirconia core-shell particles) are mixed with a portion of coupling agent in a solvent, surface treated, and then dried for later use;

[0026] S2. Preparation of base adhesive: Under a dry and inert atmosphere, α,ω-dihydroxypolydimethylsiloxane, high-temperature resistant silicone resin, and organosilicon polymer containing phenyl or large-volume side groups are added to a planetary mixer and stirred until homogeneous;

[0027] S3. Filler dispersion: Add reinforcing agent, pretreated heat-resistant nanoparticles, heat-resistant reinforcing agent (such as zinc borate) and remaining coupling agent to the mixture in step 2, and disperse it under vacuum at high speed until uniform to obtain a homogeneous paste.

[0028] S4. Catalysis and final mixing: Cool the paste to below room temperature, add crosslinking agent and catalyst, and stir evenly under vacuum and low shear conditions;

[0029] S5. Degassing and Filling: The final adhesive material is placed under high vacuum to remove air bubbles, and then filled into a moisture-proof container to obtain the product.

[0030] Compared with the prior art, the beneficial effects of the present invention are:

[0031] 1. By using heat-resistant nanoparticles with a cerium oxide@zirconia core-shell structure, and taking advantage of the antioxidant properties of cerium oxide and the phase transformation toughening properties of zirconia, a more stable protective layer is formed at high temperatures, while inhibiting the embrittlement of the matrix. The composite filler can more effectively synergistically improve the heat oxidation resistance, creep resistance and high-temperature toughness of the sealant.

[0032] 2. By adding a small amount of zinc borate or polyborosiloxane heat-resistant reinforcing agent to the formula, these substances will melt or form a glassy ceramic phase at high temperatures (e.g., >400℃), actively filling the pores and cracks caused by the decomposition of organic components, achieving self-healing protection, and significantly improving the long-term sealing integrity and ablation resistance of the sealant at extreme temperatures (>500℃).

[0033] 3. By adding a small amount of organosilicon polymers containing phenyl or large-volume side groups to the raw materials, these large-volume groups can increase the rigid free volume of the molecular chain, better maintain elasticity at high temperatures, and improve the residual elasticity and crack resistance of the sealant after high-temperature thermal cycling while maintaining excellent heat resistance.

[0034] 4. In the synthesis of high-temperature resistant silicone resin, dynamic covalent bonds such as disulfide bonds that can be reversibly exchanged at high temperatures are introduced. By controlling the hydrolysis and condensation rate of the crosslinking agent, a gradient crosslinking network from dense to sparse is formed, which can further enhance the high-temperature self-healing ability of the sealant material and dissipate stress, thereby maintaining a longer service life under thermal shock or mechanical vibration conditions.

[0035] Through the scientific formulation and synergistic effect of the above components, this invention achieves the best balance of high temperature resistance, high temperature elasticity, thermal shock resistance and long-term durability without sacrificing initial strength and construction performance, making it particularly suitable for high-end industrial fields with extremely high reliability requirements. Detailed Implementation

[0036] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the examples. 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.

[0037] Example 1

[0038] 1. Raw material preparation:

[0039] High-temperature resistant silicone resin (containing dynamic disulfide bond structure): 50 parts

[0040] α,ω-dihydroxypolydimethylsiloxane (viscosity 10000 mPa·s): 100 parts

[0041] Methylphenyl silicone oil (phenyl content 25%): 15 parts

[0042] Fumed silica: 25 parts

[0043] Cerium oxide@zirconia core-shell nanoparticles (treated with KH-560): 8 parts

[0044] Zinc borate: 2 parts

[0045] γ-aminopropyltriethoxysilane: 3 parts

[0046] Methyltrimethoxysilane: 8 parts

[0047] Tetrabutyl titanate: 1.5 parts

[0048] Dibutyltin dilaurate: 0.1 parts

[0049] 2. Preparation process:

[0050] S1. Sonicate cerium oxide@zirconia core-shell particles with 1 part γ-aminopropyltriethoxysilane in ethanol for 1 hour, then dry;

[0051] S2. Under nitrogen protection, add α,ω-dihydroxypolydimethylsiloxane, high-temperature resistant silicone resin, and methylphenyl silicone oil to a planetary mixer and mix at low speed for 20 minutes;

[0052] S3. Add fumed silica, the core-shell particles prepared in step a, zinc borate and the remaining 2 parts of coupling agent. Mix at low speed first, then disperse at high speed under a vacuum of -0.095MPa for 60 minutes until the paste is uniform and fine.

[0053] S4. Cool the paste to below 25°C, add methyltrimethoxysilane, tetrabutyl titanate and dibutyltin dilaurate, and stir at low speed under vacuum for 30 minutes;

[0054] S5. Finally, degas under a high vacuum of -0.1MPa for 20 minutes, fill into aluminum tubes, and seal for storage.

[0055] Examples 2-4

[0056] Adjust the dosage of each component, and the specific ratio is shown in Table 1. The preparation method is the same as in Example 1.

[0057] Table 1: Raw material ratio table for Examples 1-4 (parts by weight)

[0058]

[0059] Comparative Example 1: Commercially available ordinary high-temperature resistant silicone resin (without dynamic disulfide bonds and special structures) was used, and no methyl phenyl silicone oil, core-shell particles and zinc borate were added. The rest were the same as in Example 1.

[0060] Performance testing: The sealants obtained in Examples 1-4 and Comparative Example 1 were made into standard test pieces, and after curing at room temperature for 7 days, performance testing was carried out. The results are shown in Table 2.

[0061] Table 2: Performance Test Results

[0062]

[0063] Results analysis:

[0064] As shown in Table 2, after undergoing harsh thermal aging, Examples 1-3 of the present invention (containing methylphenyl silicone oil, core-shell particles, and a dynamic structure) exhibited a significantly higher elongation at break retention rate (72%-82%) than Example 4 and Comparative Example 1. This indicates that the introduced phenyl-containing organosilicon polymer played a decisive role in maintaining high-temperature elasticity. Simultaneously, Examples 1-3 also demonstrated exceptionally strong thermal shock resistance, thanks to the stress relaxation function of the dynamic disulfide bonds and the toughening effect of the core-shell particles. Although Example 4 initially showed acceptable performance, it lacked a flexible phase and a synergistic heat-resistant system, resulting in a sharp decline in performance and poor thermal shock resistance after thermal aging. Comparative Example 1 exhibited the worst overall performance.

[0065] In summary, this invention, through unique formulation design, successfully prepared a silicone sealant that combines ultra-high temperature resistance, excellent high-temperature elasticity retention, and outstanding thermal shock resistance, solving the bottleneck problems of existing technologies and possessing extremely high industrial application value.

[0066] 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 sealant, comprising the following raw materials: 10-100 parts of high-temperature resistant silicone resin and 10-100 parts of α,ω-dihydroxypolydimethylsiloxane, 5-80 parts of reinforcing agent, 1-20 parts of crosslinking agent, 1-10 parts of coupling agent, 1-10 parts of catalyst, and 1-10 parts of heat-resistant nanoparticles, characterized in that: The raw materials also include 5-20 parts of organosilicon polymers containing phenyl or bulky side groups.

2. The high-temperature resistant silicone sealant according to claim 1, characterized in that: The heat-resistant nanoparticles have a cerium oxide@zirconia core-shell structure.

3. The high-temperature resistant silicone sealant according to claim 1, characterized in that: The raw materials also include 0.5-5 parts of a heat-resistant reinforcing agent, which is zinc borate or polyborosiloxane.

4. The high-temperature resistant silicone sealant according to claim 1, characterized in that: The organosilicon polymer containing phenyl or bulky side groups is methylphenyl silicone oil.

5. The high-temperature resistant silicone sealant according to claim 2, characterized in that: The cerium oxide@zirconia core-shell structure is obtained by dispersing cerium oxide nanoparticles in a precursor solution containing a zirconium source, and then precisely controlling the pH value, temperature and concentration to allow zirconium oxide (ZrO2) to precipitate and grow uniformly on the surface of each cerium oxide particle, eventually forming a complete shell. After washing, drying and calcining at an appropriate temperature, cerium oxide@zirconia core-shell nanoparticles with good crystallinity are obtained.

6. The high-temperature resistant silicone sealant according to claim 1, characterized in that: The molecular formula of the high-temperature resistant silicone resin is: (C2H5O)3-Si-(CH2)3-SS-(CH2)3-Si-(C2H5O)3.

7. The high-temperature resistant silicone sealant according to claim 6, characterized in that: The high-temperature resistant silicone resin has (C2H5O)3Si- at ​​both ends of its molecular formula, which are triethoxysilyl groups; -SS- in the middle is a disulfide bond; and -(CH2)3- is a propyl chain.

8. A method for preparing the high-temperature resistant silicone sealant as described in any one of claims 1-7, characterized in that, Includes the following steps: S1. Pretreatment: Heat-resistant nanoparticles are mixed with a portion of the coupling agent in a solvent, surface treated, and then dried for later use; S2. Preparation of base adhesive: Under a dry and inert atmosphere, α,ω-dihydroxypolydimethylsiloxane, high-temperature resistant silicone resin, and organosilicon polymer containing phenyl or large-volume side groups are added to a planetary mixer and stirred until homogeneous; S3. Filler dispersion: Add reinforcing agent, pretreated heat-resistant nanoparticles, heat-resistant reinforcing agent and remaining coupling agent to the mixture in step 2, and disperse it under vacuum at high speed until uniform to obtain a homogeneous paste. S4. Catalysis and final mixing: Cool the paste to below room temperature, add crosslinking agent and catalyst, and stir evenly under vacuum and low shear conditions; S5. Degassing and Filling: The final adhesive material is placed under high vacuum to remove air bubbles, and then filled into a moisture-proof container to obtain the product.

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