Silicone rubber composite material with excellent mechanical property and flame retardant property as well as preparation method and application of silicone rubber composite material

Abstract

The invention belongs to the technical field of silicone rubber, and particularly relates to a silicone rubber composite material with excellent mechanical property and flame retardant property as well as a preparation method and application thereof. According to the application, silane coupling agents such as KH570 and the like are introduced into the silicone rubber to modify the expanded graphite and the Pt catalyst, so that the adverse effect of introduction of the expanded graphite on the mechanical property of the silicone rubber composite material is effectively eliminated, the mechanical property of a silicone rubber matrix is improved, and a silicon chain is catalyzed by the Pt catalyst to form a compact network structure; the flame-retardant silicon-carbon composite material has the advantages that the flame-retardant silicon-carbon composite material is modified by the silane coupling agent modified expanded graphite such as KH570, and the quality of an expanded and compact silicon-carbon protective layer and a flame-retardant protective layer is promoted to be improved during combustion, so that the mechanical property and the flame-retardant property of the silicon rubber composite material are improved, and the silicon rubber composite material with excellent comprehensive performance is obtained; the technical problem that the comprehensive performance of the silicone rubber composite material is low due to the fact that the silicone rubber composite material in the prior art is difficult to give consideration to mechanical performance and flame retardant performance is solved.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of silicone rubber, and particularly relates to a silicone rubber composite material with excellent mechanical properties and flame retardant properties, a preparation method and application. BACKGROUND

[0002] Silicone rubber (SR) is widely used in many fields such as transportation, aerospace, construction and electronics due to its good thermal stability, chemical resistance, mechanical flexibility, and weather resistance and oxidation resistance. The high bond energy Si-O-Si bond in the molecular structure of silicone rubber endows it with the above-mentioned excellent physical and chemical properties. However, silicone rubber itself is flammable, and the organic side groups on the polysiloxane chain can be easily ignited under high temperature or flame, which seriously limits its further application in some high fire safety requirement scenarios.

[0003] At present, in order to improve the flame retardant properties of silicone rubber, a lot of attempts have been made in the industry. Among them, introducing flame retardant into the polymer matrix is a relatively economical and effective way. So far, many flame retardant fillers have been widely used to enhance the flame retardant properties of silicone rubber materials. Intumescent graphite (EG) is a commonly used intumescent flame retardant, which is composed of tightly combined carbon atom sheets and can expand and form a large protective layer under high temperature or fire environment. It also has the advantages of good chemical stability, low cost and easy preparation, and shows great advantages in the modification of silicone rubber flame retardant. However, there are still some problems in introducing intumescent graphite (EG) into silicone rubber. The most prominent one is that intumescent graphite (EG) as an inorganic filler has poor interfacial compatibility with silicone rubber as an organic polymer matrix, and with the increase of the addition amount of intumescent graphite (EG), intumescent graphite (EG) will agglomerate, weaken the interaction between molecular segments, and cause the mechanical properties of silicone rubber composite material to decrease significantly. At the same time, the loose and porous structure of intumescent graphite (EG) itself also easily has a negative impact on the mechanical properties of silicone rubber composite material. In some application scenarios, silicone rubber composite material is required to have both flame retardant and mechanical properties. For example, in the application scenarios of automobile engine sealing ring, new energy automobile battery pack sealing element, etc., in addition to the requirement that silicone rubber composite material has good high temperature resistance and flame retardant fireproof performance, it is also required that silicone rubber composite material has good mechanical properties, and it is difficult to cause structural damage due to mechanical stress impact such as vibration and jolt during engine starting and automobile running, so as to avoid the occurrence of safety accidents.

[0004] By using silane coupling agent to modify expanded graphite (EG), the compatibility between the expanded graphite and the silicone rubber matrix can be enhanced, the agglomeration can be reduced, and the part of the adverse effects of the introduction of the expanded graphite on the mechanical properties of the silicone rubber composite material can be eliminated; however, as an organosilicon, the silane coupling agent has an organic group which can also cause the flame retardant performance to decrease, so introducing the conventional silane coupling agent modified expanded graphite (EG) into the silicone rubber composite material is not an ideal modification method, and it is difficult to balance the mechanical properties and the flame retardant performance, which makes the comprehensive performance of the current silicone rubber composite material low, and it is necessary to develop a new type of silicone rubber composite material. SUMMARY

[0005] Therefore, the present application provides a silicone rubber composite material with excellent mechanical properties and flame retardant performance, a preparation method and an application, so as to solve the technical problem that the silicone rubber composite material in the prior art is difficult to balance the mechanical properties and the flame retardant performance, and the comprehensive performance of the silicone rubber composite material is low.

[0006] The first aspect of the present application provides a silicone rubber composite material with excellent mechanical properties and flame retardant performance, and the raw materials include: a vinyl silicone rubber raw rubber, a hydroxyl silicone oil, fumed silica, a vulcanizing agent, expanded graphite modified by a silane coupling agent containing an unsaturated carbon-carbon double bond, and a Pt catalyst.

[0007] Preferably, the expanded graphite modified by the silane coupling agent containing the unsaturated carbon-carbon double bond is at least one selected from the group consisting of expanded graphite modified by γ-methacryloxypropyltrimethoxysilane (KH570), expanded graphite modified by methacryloxyethoxytriethoxysilane, expanded graphite modified by methacryloxypropyltriethoxysilane, expanded graphite modified by vinyltrimethoxysilane, and expanded graphite modified by vinyltriethoxysilane.

[0008] Preferably, the vinyl silicone rubber raw rubber is at least one selected from the group consisting of a methyl-terminated vinyl silicone rubber raw rubber and a vinyl-terminated vinyl silicone rubber raw rubber.

[0009] Preferably, the vulcanizing agent is at least one selected from the group consisting of dicumyl peroxide, benzoyl peroxide, di-tert-butyl peroxide, and 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane.

[0010] Preferably, in the raw materials of the silicone rubber composite material with excellent mechanical properties and flame retardant performance, 80-120 parts by mass of the vinyl silicone rubber raw rubber, 1-5 parts by mass of the hydroxyl silicone oil, 30-50 parts by mass of the fumed silica, 1-3 parts by mass of the vulcanizing agent, 1-5 parts by mass of the expanded graphite modified by the silane coupling agent containing the unsaturated carbon-carbon double bond, and 0.1-0.5 parts by mass of the Pt catalyst are included.

[0011] The second aspect of this application provides a method for preparing a silicone rubber composite material with both excellent mechanical properties and flame retardant properties, which can prepare the silicone rubber composite material with both excellent mechanical properties and flame retardant properties described in the first aspect, comprising the following steps:

[0012] The steps for modifying expanded graphite are as follows: Silane coupling agent containing unsaturated carbon-carbon double bonds and expanded graphite are added to an alcohol-water mixed solution, and expanded graphite is modified under the catalysis of a catalyst to obtain expanded graphite modified with silane coupling agent containing unsaturated carbon-carbon double bonds.

[0013] The mixing process involves adding vinyl silicone rubber raw material, hydroxyl silicone oil, and fumed silica to a mixing mill and mixing them to obtain a basic mixed rubber compound.

[0014] The open milling process involves transferring the basic rubber compound to an open mill, adding a vulcanizing agent, expanded graphite modified with a silane coupling agent containing unsaturated carbon-carbon double bonds, and a Pt catalyst, and then performing open milling to obtain the compound.

[0015] The vulcanization process involves adding the compounded rubber to a vulcanizing machine for vulcanization to obtain a silicone rubber composite material that combines excellent mechanical properties with flame retardant properties.

[0016] Preferably, in the step of modifying expanded graphite, the mass ratio of the silane coupling agent containing unsaturated carbon-carbon double bonds to expanded graphite is 1:10~30.

[0017] Preferably, the process of modifying expanded graphite includes: stirring for 1-5 hours and ultrasonic treatment for 10-30 minutes.

[0018] Preferably, in the step of modifying expanded graphite, the catalyst used in the process of modifying expanded graphite is at least one of acid or alkali.

[0019] Preferably, in the step of modifying expanded graphite, the catalyst used in the process of modifying expanded graphite is an aqueous solution of hydrochloric acid, and the pH of the aqueous solution of alcohol is 3-5.

[0020] Preferably, in the step of modifying expanded graphite, the post-processing steps after modifying expanded graphite include: sequentially filtering, washing to neutral, and drying at 60~100℃ for 5~10h.

[0021] Preferably, in the intensive mixing step, the mixing temperature is 100~150℃ and the mixing time is 1~5min;

[0022] In the aforementioned refining step, the refining temperature is 60~100℃ and the time is 1~5min;

[0023] In the vulcanization step, the vulcanization temperature is 150~200℃, the time is 3~10min, and the pressure is 10~20MPa.

[0024] The third aspect of this application provides the application of the silicone rubber composite material described in the first aspect, which possesses both excellent mechanical properties and flame retardant properties, in the fields of transportation, aerospace, construction, or electronics.

[0025] Compared with the prior art, the silicone rubber composite material, preparation method, and application provided in this application, which possess both excellent mechanical properties and flame retardant properties, have at least the following beneficial effects:

[0026] 1. The silicone rubber composite material provided in this application, which possesses both excellent mechanical properties and flame retardant properties, introduces expanded graphite modified with silane coupling agents such as KH570 into the silicone rubber matrix. The organic segment structure of the silane coupling agent enhances the compatibility between the expanded graphite and the silicone rubber, eliminating some of the adverse effects of the introduced expanded graphite on the mechanical properties of the silicone rubber composite material. Furthermore, the organic segment structure of silane coupling agents such as KH570 contains unsaturated carbon-carbon double bonds (C=C) and other groups. During the vulcanization or crosslinking reaction of the silicone rubber, these groups crosslink or copolymerize with the active groups such as vinyl groups on the silicone rubber chain, forming a chemical bond. This improves the bonding force between the expanded graphite and the silicone rubber matrix, effectively preventing the expanded graphite from agglomerating and detaching during mixing and use, and increasing the crosslinking density of the silicone rubber chain, thereby further enhancing the mechanical properties of the silicone rubber composite material.

[0027] 2. The silicone rubber composite material with excellent mechanical and flame-retardant properties provided in this application introduces a Pt catalyst into the silicone rubber matrix. The Pt catalyst can catalyze the formation of a dense network structure between silicon chains and synergize with expanded graphite modified by silane coupling agents such as KH570. This promotes the formation of an expanded and dense silicon-carbon protective layer when the silicone rubber is burning, improving the quality of the original "worm-like" graphitized carbon flame-retardant protective layer of expanded graphite. As a result, the mechanical and flame-retardant properties of the silicone rubber composite material are improved. Attached Figure Description

[0028] To more clearly illustrate the technical solutions in the specific embodiments of this application or the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this application. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0029] Figure 1 This is a schematic diagram of the preparation method of the silicone rubber composite material with excellent mechanical properties and flame retardant properties provided in Embodiment 1 of this application. Detailed Implementation

[0030] This application provides a silicone rubber composite material with both excellent mechanical properties and flame retardant properties, as well as its preparation method and application, to solve the technical problem that silicone rubber composite materials in the prior art are difficult to balance mechanical properties and flame retardant properties, resulting in low overall performance of silicone rubber composite materials.

[0031] The technical solutions of this application will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this application. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0032] Example 1

[0033] This embodiment provides a method for preparing a silicone rubber composite material with both excellent mechanical properties and flame retardant properties, the process flow diagram of which is shown below. Figure 1 As shown, the process includes steps of modifying expanded graphite and sequentially performing internal mixing, open milling, and sulfidation.

[0034] The steps for modifying expanded graphite include:

[0035] After drying expanded graphite (EG) at 80°C for 8 hours and cooling to room temperature, 1g of γ-methacryloxypropyltrimethoxysilane (KH570) and 20g of expanded graphite (EG) were weighed at a mass ratio of 1:20.

[0036] First, 1g of γ-methacryloxypropyltrimethoxysilane was added to anhydrous ethanol, and the pH of the anhydrous ethanol was adjusted to 4 using hydrochloric acid aqueous solution. Then, 20g of expanded graphite was added, and the mixture was stirred at room temperature for 3 hours and sonicated for 20 minutes to promote the modification of expanded graphite under hydrochloric acid catalysis. After the modification reaction was completed, the solid product was filtered and collected. The solid product was washed until the washing liquid was neutral. Next, the washed product was dried at 80°C for 8 hours to obtain modified expanded graphite, which is expanded graphite modified with silane coupling agent containing unsaturated carbon-carbon double bonds.

[0037] The steps of mixing, refining, and vulcanization in sequence include:

[0038] Prepare 100 phr of methyl vinyl silicone rubber (MVQ) raw rubber and 4 phr of hydroxyl silicone oil (OH-PDMS).

[0039] 40 phr of fumed silica (SiO2), 2 phr of dicumyl peroxide (DCP) as a sulfiding agent, 4 phr of expanded graphite modified with silane coupling agent containing unsaturated carbon-carbon double bonds, and 0.25 phr of Pt catalyst are prepared for use.

[0040] First, add 100 phr of methyl vinyl silicone rubber raw rubber, 4 phr of hydroxyl silicone oil and 40 phr of fumed silica into a mixer and mix at 130°C for 3 minutes to obtain a uniform basic compound.

[0041] The basic mixed rubber compound is then transferred to a two-roll mill, and 2 phr of vulcanizing agent dicumyl peroxide, 4 phr of expanded graphite modified with silane coupling agent containing unsaturated carbon-carbon double bonds, and 0.25 phr of Pt catalyst (2000 ppm concentration) are added in sequence. The mixture is then milled at 80°C to obtain the compound and left to stand at room temperature for 12 hours.

[0042] The compounded rubber was then placed into the mold of a flat vulcanizing machine and vulcanized for 5 minutes at 170°C and 17MPa. After cooling and demolding, the final silicone rubber composite material was obtained, named SR / 4MEG(KH570) / Pt-0.25. This silicone rubber composite material has both excellent mechanical properties and flame retardant properties.

[0043] Example 2

[0044] This embodiment provides a method for preparing a silicone rubber composite material. As the first comparative embodiment, the difference from Embodiment 1 is that no Pt catalyst is added. The method includes the steps of modifying expanded graphite and sequentially performing internal mixing, open milling, and vulcanization.

[0045] The steps for modifying expanded graphite include:

[0046] After drying expanded graphite (EG) at 80°C for 8 hours and cooling to room temperature, 1g of γ-methacryloxypropyltrimethoxysilane (KH570) and 20g of expanded graphite (EG) were weighed at a mass ratio of 1:20.

[0047] First, 1g of γ-methacryloxypropyltrimethoxysilane was added to anhydrous ethanol, and the pH of the anhydrous ethanol was adjusted to 4 using hydrochloric acid aqueous solution. Then, 20g of expanded graphite was added, and the mixture was stirred at room temperature for 3 hours and sonicated for 20 minutes to promote the modification of expanded graphite under hydrochloric acid catalysis. After the modification reaction was completed, the solid product was filtered and collected. The solid product was washed until the washing liquid was neutral. Next, the washed product was dried at 80°C for 8 hours to obtain modified expanded graphite, which is expanded graphite modified with silane coupling agent containing unsaturated carbon-carbon double bonds.

[0048] The steps of mixing, refining, and vulcanization in sequence include:

[0049] Prepare 100 phr of methyl vinyl silicone rubber (MVQ) raw rubber, 4 phr of hydroxyl silicone oil (OH-PDMS), 40 phr of fumed silica (SiO2), 2 phr of vulcanizing agent dicumyl peroxide (DCP), and 4 phr of expanded graphite modified with silane coupling agent containing unsaturated carbon-carbon double bonds.

[0050] First, add 100 phr of methyl vinyl silicone rubber raw rubber, 4 phr of hydroxyl silicone oil and 40 phr of fumed silica into a mixer and mix at 130°C for 3 minutes to obtain a uniform basic compound.

[0051] The basic mixed rubber compound is then transferred to a two-roll mill, and 2 phr of vulcanizing agent dicumyl peroxide and 4 phr of expanded graphite modified with silane coupling agent containing unsaturated carbon-carbon double bonds are added in sequence. The mixture is then milled at 80°C to obtain the compound and left to stand at room temperature for 12 hours.

[0052] The compounded rubber is then placed into the mold of a flat vulcanizing machine and vulcanized for 5 minutes at 170°C and 17MPa. After cooling and demolding, the final silicone rubber composite material is obtained, named SR / 4MEG (KH570).

[0053] Example 3

[0054] This embodiment provides a method for preparing a silicone rubber composite material. As a second comparative embodiment, the difference from Embodiment 1 is that the modified expanded graphite used is γ-aminopropyltriethoxysilane (KH550), which includes the steps of modifying expanded graphite and sequentially mixing, open milling and vulcanization.

[0055] The steps for modifying expanded graphite include:

[0056] After drying expanded graphite (EG) at 80°C for 8 hours and cooling to room temperature, 1g of γ-aminopropyltriethoxysilane (KH550) and 20g of expanded graphite (EG) were weighed at a mass ratio of 1:20.

[0057] First, 1g of γ-methacryloxypropyltrimethoxysilane was added to anhydrous ethanol, and the pH of the anhydrous ethanol was adjusted to 4 using hydrochloric acid aqueous solution. Then, 20g of expanded graphite was added, and the mixture was stirred at room temperature for 3 hours and sonicated for 20 minutes to promote the modification of expanded graphite under hydrochloric acid catalysis. After the modification reaction was completed, the solid product was filtered and collected. The solid product was washed until the washing liquid was neutral. Next, the washed product was dried at 80°C for 8 hours to obtain modified expanded graphite, which is the expanded graphite modified by silane coupling agent KH550.

[0058] The steps of mixing, refining, and vulcanization in sequence include:

[0059] Prepare 100 phr of methyl vinyl silicone rubber (MVQ) raw rubber and 4 phr of hydroxyl silicone oil (OH-PDMS).

[0060] 40 phr of fumed silica (SiO2), 2 phr of dicumyl peroxide (DCP) as a vulcanizing agent, and 4 phr of silane coupling agent KH550 modified expanded graphite were prepared for use.

[0061] First, add 100 phr of methyl vinyl silicone rubber raw rubber, 4 phr of hydroxyl silicone oil and 40 phr of fumed silica into a mixer and mix at 130°C for 3 minutes to obtain a uniform basic compound.

[0062] The basic mixed rubber compound is then transferred to a two-roll mill, and 2 phr of vulcanizing agent dicumyl peroxide and 4 phr of expanded graphite modified with silane coupling agent KH550 are added in sequence. The mixture is then milled at 80°C to obtain the compound and left to stand at room temperature for 12 hours.

[0063] The compounded rubber is then placed into the mold of a flat vulcanizing machine and vulcanized for 5 minutes at 170°C and 17MPa. After cooling and demolding, the final silicone rubber composite material is obtained, named SR / 4MEG (KH550).

[0064] Example 4

[0065] This embodiment provides a method for preparing a silicone rubber composite material. As the third comparative embodiment, ordinary expanded graphite is introduced into the silicone rubber, including the steps of sequential internal mixing, open milling and vulcanization.

[0066] The steps of mixing, refining, and vulcanization in sequence include:

[0067] Prepare 100 phr of methyl vinyl silicone rubber (MVQ) raw rubber and 4 phr of hydroxyl silicone oil (OH-PDMS).

[0068] 40 phr of fumed silica (SiO2), 2 phr of dicumyl peroxide (DCP) as a vulcanizing agent, and 6 phr of expanded graphite are ready for use.

[0069] First, add 100 phr of methyl vinyl silicone rubber raw rubber, 4 phr of hydroxyl silicone oil and 40 phr of fumed silica into a mixer and mix at 130°C for 3 minutes to obtain a uniform basic compound.

[0070] The basic mixed rubber compound is then transferred to a two-roll mill, and 2 phr of vulcanizing agent dicumyl peroxide and 6 phr of expanded graphite are added in sequence. The mixture is then milled at 80°C to obtain the compound and left to stand at room temperature for 12 hours.

[0071] The compounded rubber is then placed into the mold of a flat vulcanizing machine and vulcanized for 5 minutes at 170°C and 17MPa. After cooling and demolding, the final silicone rubber composite material is obtained, named SR / 6MEG.

[0072] Example 5

[0073] This embodiment provides a method for preparing a silicone rubber composite material. As the fourth comparative embodiment, ordinary expanded graphite is introduced into the silicone rubber, including the steps of sequential internal mixing, open milling and vulcanization.

[0074] The steps of mixing, refining, and vulcanization in sequence include:

[0075] Prepare 100 phr of methyl vinyl silicone rubber (MVQ) raw rubber and 4 phr of hydroxyl silicone oil (OH-PDMS).

[0076] 40 phr of fumed silica (SiO2), 2 phr of dicumyl peroxide (DCP) vulcanizing agent, and 4 phr of expanded graphite are ready for use.

[0077] First, add 100 phr of methyl vinyl silicone rubber raw rubber, 4 phr of hydroxyl silicone oil and 40 phr of fumed silica into a mixer and mix at 130°C for 3 minutes to obtain a uniform basic compound.

[0078] The basic mixed rubber compound is then transferred to a two-roll mill, and 2 phr of vulcanizing agent dicumyl peroxide and 4 phr of expanded graphite are added in sequence. The mixture is then milled at 80°C to obtain the compound and left to stand at room temperature for 12 hours.

[0079] The compounded rubber is then placed into the mold of a flat vulcanizing machine and vulcanized for 5 minutes at 170°C and 17MPa. After cooling and demolding, the final silicone rubber composite material is obtained, named SR / 4MEG.

[0080] Example 6

[0081] This embodiment provides a method for preparing silicone rubber material. As the fifth comparative embodiment, it includes the steps of sequential mixing, open milling, and vulcanization.

[0082] The steps of mixing, refining, and vulcanization in sequence include:

[0083] Prepare 100 phr of methyl vinyl silicone rubber (MVQ) raw rubber and 4 phr of hydroxyl silicone oil (OH-PDMS).

[0084] 40 phr of fumed silica (SiO2) and 2 phr of dicumyl peroxide (DCP) as a vulcanizing agent;

[0085] First, add 100 phr of methyl vinyl silicone rubber raw rubber, 4 phr of hydroxyl silicone oil and 40 phr of fumed silica into a mixer and mix at 130°C for 3 minutes to obtain a uniform basic compound.

[0086] The basic mixed rubber compound is then transferred to a two-roll mill, 2 phr of vulcanizing agent dicumyl peroxide is added, and the mixture is milled at 80°C to obtain the compound, which is then left to stand at room temperature for 12 hours.

[0087] The compounded rubber is then placed into the mold of a flat vulcanizing machine and vulcanized for 5 minutes at 170°C and 17MPa. After cooling and demolding, the final silicone rubber material, named SR, is obtained.

[0088] Experimental Example 1

[0089] This experiment tests the mechanical properties, flame retardant properties, and thermal stability of the silicone rubber composite materials provided in Examples 1-5 and the silicone rubber material provided in Example 6.

[0090] The mechanical performance tests included tensile strength and elongation at break tests according to GB / T 528-2009; the flame retardant performance tests included limiting oxygen index tests according to GB / T 10707-2008, vertical burning tests according to UL-94 standard, and tests for combustion parameters such as peak heat release rate, time to peak heat release rate, and total heat release according to ISO 5660-1; thermogravimetric analysis was also performed under a nitrogen atmosphere according to GB / T 14837.3-2018; the test results are shown in Table 1.

[0091] Table 1: Performance Test Results

[0092]

[0093] As shown in Table 1, the silicone rubber material (SR) provided in Example 6, without the introduction of any expanded graphite, exhibits good mechanical properties such as tensile strength and elongation at break, but has a low limiting oxygen index of only 23.4%, making it prone to combustion and unable to pass the vertical combustion test. In contrast, the silicone rubber composite material (SR / 6MEG) provided in Example 4, after the introduction of expanded graphite, shows an improved limiting oxygen index, making it less prone to combustion and able to pass the vertical combustion test. Simultaneously, combustion parameters such as peak heat release rate and total heat release decrease, indicating that the silicone rubber composite material (SR / 6MEG) provided in Example 4, after combustion, shows a significant improvement in its limiting oxygen index due to the introduction of expanded graphite. Expanded graphite can expand at high temperatures to form "worm-like" graphitized carbon, which then transforms into an expanded and continuous physical barrier, reducing the rate and amount of heat release. However, the mechanical properties of the silicone rubber composite material (SR / 6MEG) provided in Example 4, such as tensile strength and elongation at break, decreased significantly. In addition, the mechanical properties of the silicone rubber composite material (SR / 4MEG) provided in Example 5, such as tensile strength and elongation at break, also decreased when a small amount of expanded graphite was introduced. This indicates that directly introducing expanded graphite into the silicone rubber matrix is ​​not an ideal modification method, and will result in lower overall performance of the silicone rubber composite material (SR / 6MEG).

[0094] Furthermore, Table 1 also shows that, compared with the silicone rubber composites provided in Examples 4-5, the silicone rubber composite (SR / 4MEG(KH550)) provided in Example 3, after introducing silane coupling agent-modified expanded graphite into the silicone rubber matrix, exhibits significantly improved mechanical properties such as tensile strength. This indicates that the silane coupling agent KH550, due to the formation of covalent Si-O-Si bonds between the siloxane alkyl group at one end and the hydroxyl functional groups on the EG surface under hydrochloric acid catalysis, firmly "grafts" the silane molecules onto the EG surface for modification, while the other end of the organic chain segment structure features similar to... The similarity of organic groups in the main chain of silicone rubber facilitates further physical interactions (entanglement, van der Waals forces) between it and the silicone rubber matrix. The introduction of this "organic-inorganic" amphiphilic molecule improves the polarity difference between EG, which is originally more hydrophilic and more oleophobic, and organosilicon rubber, achieving compatibility and dispersion at the molecular level. This eliminates some of the adverse effects of the introduction of expanded graphite on the mechanical properties of silicone rubber composites, thereby improving the mechanical properties of silicone rubber composites. However, due to the presence of organic segments, the flame retardant properties of silicone rubber composites will decrease slightly.

[0095] Furthermore, Table 1 shows that different silane coupling agents modified with expanded graphite produce different performance improvements when introduced into the silicone rubber matrix. Compared with the silicone rubber composite material provided in Example 3, the silicone rubber composite material (SR / 4MEG(KH570)) provided in Example 2, after introducing expanded graphite modified with silane coupling agent KH570 into the silicone rubber matrix, exhibits better performance. This is because the organic segments of KH570 contain unsaturated carbon-carbon double bonds (C=C) and carbonyl groups (C=O). The carbonyl groups can enhance the hydrogen bonding and dipole interactions with the siloxane chains and other polar groups in the matrix, which is beneficial for the expanded graphite to be encapsulated and impregnated in the matrix, promoting uniform dispersion. During the vulcanization or crosslinking reaction of silicone rubber, the C=C bond can crosslink or copolymerize with the active groups such as vinyl groups on the silicone rubber chain to form a chemical bond, which improves the bonding force between expanded graphite and the silicone rubber matrix. This effectively prevents the expanded graphite from agglomerating and falling off during mixing and use. Furthermore, by participating in chemical reactions such as vulcanization or crosslinking, it helps to increase the crosslinking density of the silicone rubber chain. As a result, compared with the silicone rubber composite material provided in Example 3, the mechanical properties such as tensile strength and elongation at break of the silicone rubber composite material (SR / 4MEG(KH570)) provided in Example 2 are improved. However, the flame retardant performance is still not as good as the silicone rubber composite material with expanded graphite directly introduced, and the overall performance is not ideal.

[0096] Furthermore, Table 1 shows that, compared to the silicone rubber composite material provided in Example 2, the SR / 4MEG(KH570) / Pt-0.25 provided in Example 1, with the addition of platinum (Pt) as a catalyst in the presence of a vulcanizing agent, can further improve the mechanical properties, flame retardant properties, and thermal stability of the silicone rubber composite material. This is because the synergistic addition of the Pt catalyst and expanded graphite to the silicone rubber allows the Pt catalyst to catalyze the formation of a dense network structure between the silicon chains, thereby improving the mechanical properties, thermal stability, and flame retardant properties of the silicone rubber. Simultaneously, at high temperatures, the Pt catalyst also… It can promote the organic-inorganic conversion and increase the residual rate of silicone rubber matrix. Under the combined action of silane coupling agent modified expanded graphite and Pt catalyst, an expanded and dense silicon-carbon protective layer can be formed when silicone rubber is burned. MEG expands when heated to form a "worm-like" structure, which prolongs the propagation path of combustible gas and heat. The Pt catalyst promotes the formation of silicon-carbon layer and further improves the quality of protective layer. The silane coupling agent modified expanded graphite and Pt catalyst work together to effectively reduce the heat release rate and total heat release, thereby improving the flame retardant performance and thermal stability of silicone rubber composite material.

[0097] The experimental results above show that the technical solution provided in this application, based on the introduction of silane coupling agent modified expanded graphite into silicone rubber composite material, improves the type of silane coupling agent and introduces Pt catalyst, thus obtaining a silicone rubber composite material with both excellent flame retardant properties and mechanical properties, as well as good thermal stability.

[0098] The above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application.

Claims

1. A silicone rubber composite material possessing both excellent mechanical properties and flame-retardant properties, characterized in that, The raw materials include: vinyl silicone rubber raw rubber, hydroxyl silicone oil, fumed silica, vulcanizing agent, expanded graphite modified with silane coupling agent containing unsaturated carbon-carbon double bonds, and Pt catalyst.

2. The silicone rubber composite material with both excellent mechanical properties and flame retardant properties according to claim 1, characterized in that, The expanded graphite modified with the silane coupling agent containing unsaturated carbon-carbon double bonds is selected from at least one of γ-methacryloxypropyltrimethoxysilane modified expanded graphite, methacryloxyethoxytriethoxysilane modified expanded graphite, methacryloxypropyltriethoxysilane modified expanded graphite, vinyltrimethoxysilane modified expanded graphite, and vinyltriethoxysilane modified expanded graphite.

3. The silicone rubber composite material with both excellent mechanical properties and flame retardant properties according to claim 1, characterized in that, The vinyl silicone rubber raw material is selected from at least one of methyl-terminated vinyl silicone rubber raw material and vinyl-terminated vinyl silicone rubber raw material.

4. The silicone rubber composite material with both excellent mechanical properties and flame retardant properties according to claim 1, characterized in that, The vulcanizing agent is selected from at least one of dicumyl peroxide, benzoyl peroxide, di-tert-butyl peroxide, and 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane.

5. A silicone rubber composite material with both excellent mechanical properties and flame retardant properties according to claim 1, characterized in that, The raw materials of the silicone rubber composite material with excellent mechanical properties and flame retardant properties, calculated by mass parts, include: 80-120 parts by mass of vinyl silicone rubber raw rubber, 1-5 parts by mass of hydroxyl silicone oil, 30-50 parts by mass of fumed silica, 1-3 parts by mass of vulcanizing agent, 1-5 parts by mass of expanded graphite modified with silane coupling agent containing unsaturated carbon-carbon double bonds, and 0.1-0.5 parts by mass of Pt catalyst.

6. A method for preparing a silicone rubber composite material with both excellent mechanical properties and flame retardant properties, characterized in that, The preparation of the silicone rubber composite material with excellent mechanical properties and flame retardant properties as described in any one of claims 1-5 includes the following steps: The steps for modifying expanded graphite are as follows: Silane coupling agent containing unsaturated carbon-carbon double bonds and expanded graphite are added to an alcohol-water mixed solution, and expanded graphite is modified under the catalysis of a catalyst to obtain expanded graphite modified with silane coupling agent containing unsaturated carbon-carbon double bonds. The mixing process involves adding vinyl silicone rubber raw material, hydroxyl silicone oil, and fumed silica to a mixing mill and mixing them to obtain a basic mixed rubber compound. The steps of open milling are as follows: the basic mixed rubber compound is transferred to an open mill, and vulcanizing agent, expanded graphite modified with silane coupling agent containing unsaturated carbon-carbon double bonds and Pt catalyst are added and the mixture is opened to obtain the compound. The vulcanization process involves adding the compounded rubber to a vulcanizing machine for vulcanization to obtain a silicone rubber composite material that combines excellent mechanical properties with flame retardant properties.

7. The method for preparing a silicone rubber composite material with both excellent mechanical properties and flame retardant properties according to claim 6, characterized in that, In the step of modifying expanded graphite, the mass ratio of the silane coupling agent containing unsaturated carbon-carbon double bonds to expanded graphite is 1:10~30.

8. The method for preparing a silicone rubber composite material with both excellent mechanical properties and flame retardant properties according to claim 6, characterized in that, The steps of modifying expanded graphite include: stirring for 1-5 hours and ultrasonic treatment for 10-30 minutes.

9. The method for preparing a silicone rubber composite material with both excellent mechanical properties and flame retardant properties according to claim 6, characterized in that, In the intensive mixing step, the mixing temperature is 100~150℃ and the mixing time is 1~5min; In the aforementioned refining step, the refining temperature is 60~100℃ and the time is 1~5min; In the vulcanization step, the vulcanization temperature is 150~200℃, the time is 3~10 minutes, and the pressure is... 10~20MPa.

10. The application of the silicone rubber composite material with excellent mechanical properties and flame retardant properties as described in any one of claims 1-5 in the fields of transportation, aerospace, construction or electronics.

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