Synergistic reinforced composite insulator silicone rubber and preparation method thereof

Abstract

The invention belongs to the technical field of high-performance rubber composite materials, and particularly discloses synergistically enhanced composite insulator silicone rubber. The composite insulator silicone rubber provided by the invention is prepared from the following components in parts by weight: 80 to 120 parts of methyl vinyl silicone rubber raw rubber, 100 to 130 parts of aluminum hydroxide, 22 to 32 parts of fumed silica, 1.5 to 3.5 parts of methyl silicone oil, 2.5 to 7 parts of hydroxyl silicone oil, 1 to 3 parts of vinyl silicone oil, 1 to 2.5 parts of silane coupling agent, 0.2 to 0.4 part of vulcanizing agent and 2 to 4 parts of ferric oxide. According to the invention, through scientific proportioning and function synergy of the methyl silicone oil, the hydroxyl silicone oil and the vinyl silicone oil, and by matching with a proper mixing process, the mechanical property, the electrical insulation property, the processability and the long-term service stability of the material are remarkably improved while excellent flame retardance is realized. The invention also provides a preparation method of the silicone rubber.

Description

Technical Field

[0001] This invention relates to the field of high-performance rubber composite materials technology, and in particular to a synergistically reinforced composite insulator silicone rubber and its preparation method. Background Technology

[0002] In power systems, especially in power plants and substations where fire safety requirements are extremely high, the flame-retardant performance of external insulation equipment such as composite insulators has become a mandatory requirement. Aluminum hydroxide (ATH), as a highly efficient and environmentally friendly halogen-free flame-retardant filler, is widely used in the flame-retardant modification of silicone rubber. However, to achieve a sufficient flame-retardant rating (such as UL94 V-0), the ATH filler content usually needs to reach 120-160 phr (per hundred parts of rubber), which brings severe technical challenges to the material: Significantly deteriorated mechanical properties: High content of rigid inorganic particles severely hinders the movement and orientation of rubber molecular chains, leading to a sharp decrease in tensile strength, tear strength, and elongation at break, and increased brittleness. Deteriorated processing performance: High filler content causes a significant increase in rubber viscosity, increases mixing energy consumption, makes filler dispersion difficult, and easily leads to "filler clumps" and local stress concentration. Prominent filler-matrix interface problems: Significant differences in physical and chemical properties exist between a large number of inorganic fillers and the silicone rubber matrix, resulting in low interfacial bonding strength, which becomes a weak link in stress transmission and the starting point of failure. Electrical performance and durability risks: Filler agglomeration and interface defects can easily become the starting point for charge accumulation and partial discharge under high voltage electric fields, leading to a decrease in the material's resistance to tracking and accelerating the electrical and thermal aging processes.

[0003] In addition, common methods for improving the properties of highly filled flame-retardant silicone rubber include: treating the reinforcing filler silica with a single type of silicone oil (such as hydroxyl silicone oil) to improve dispersibility; and treating inorganic fillers with silane coupling agents to improve interfacial bonding. However, these methods often focus on solving a single problem. For example, while hydroxyl silicone oil can improve silica dispersion, it has limited contribution to reducing system viscosity and improving processing fluidity, and it cannot provide long-term hydrophobic recovery capability; coupling agent treatment can improve the interface, but it cannot optimize the crosslinking structure of the rubber network. Especially in composite insulator applications that require simultaneous high flame retardancy, high strength, high insulation, and long-term aging resistance, a single modification method is insufficient to achieve optimal comprehensive performance.

[0004] Therefore, there is an urgent need to develop a new synergistic modification technology to systematically solve the performance contradictions of highly filled flame-retardant silicone rubber from multiple levels, such as filler dispersion, interface optimization, network structure regulation and functional endowment. Summary of the Invention

[0005] This invention aims to at least solve one of the technical problems existing in the prior art. To this end, this invention provides a synergistically reinforced composite insulator silicone rubber. Through the scientific ratio and functional synergy of methyl silicone oil, hydroxyl silicone oil, and vinyl silicone oil, combined with an appropriate mixing process, this invention achieves excellent flame retardancy while significantly improving the material's mechanical properties, electrical insulation properties, processability, and long-term service stability.

[0006] The present invention also provides a method for preparing the silicone rubber.

[0007] In a first aspect, the present invention provides a composite insulator silicone rubber, wherein the components of the silicone rubber, by weight, include: 80-120 parts of methyl vinyl silicone rubber raw rubber, 100-130 parts of aluminum hydroxide, 22-32 parts of fumed silica, 1.5-3.5 parts of methyl silicone oil, 2.5-7 parts of hydroxyl silicone oil, 1-3 parts of vinyl silicone oil, 1-2.5 parts of silane coupling agent, 0.2-0.4 parts of vulcanizing agent, and 2-4 parts of iron oxide.

[0008] This invention constructs a synergistic modification system composed of three functionally complementary silicone oils. Methyl silicone oil primarily serves as a processing aid and functional imparting agent; its low viscosity effectively reduces the mixing viscosity of highly filled systems, improving processing fluidity. Simultaneously, an appropriate amount of small-molecule methyl silicone oil, after vulcanization, acts as a controllable hydrophobic migration source, endowing the material with durable surface hydrophobic recovery capabilities. Hydroxyl silicone oil is then utilized as a key structure control agent and filler surface treatment agent; its terminal active silanol groups can chemically or physically interact with the silanol groups on the surface of fumed silica, effectively disrupting silica aggregates and achieving nanoscale dispersion in the rubber matrix, thereby constructing an efficient reinforcing network, which is fundamental to obtaining high mechanical strength. Vinyl silicone oil is used as a crosslinking network... The "designer" and regulator, with its vinyl groups on its molecular chain, can act as additional crosslinking points, cooperating with the vinyl groups of the matrix raw rubber in the peroxide-induced crosslinking reaction. By controlling its vinyl content, the crosslinking density and network uniformity of the final vulcanized rubber can be finely adjusted, thereby balancing the material's hardness, modulus, elasticity, and elongation. Finally, the alkoxy groups of the silane coupling agent can be hydrolyzed and react with the hydroxyl groups on the surface of inorganic fillers such as aluminum hydroxide. The vinyl groups or other organic functional groups at the other end can co-crosslink with the rubber matrix or generate strong interactions, thereby building a strong "molecular bridge" between the inorganic filler and the organic matrix, significantly improving interfacial adhesion and reducing interfacial defects.

[0009] According to some embodiments of the present invention, the vinyl content in the methyl vinyl silicone rubber raw rubber is 0.1~0.2wt%, and its molecular weight is 4×10⁻⁶. 5 ~9×10 5 .

[0010] According to some embodiments of the present invention, the weight ratio of the methyl silicone oil, hydroxyl silicone oil and vinyl silicone oil is (0.8~1.5):(2~4):1.

[0011] This invention also improves the overall performance of silicone rubber by precisely controlling the dosage ratio of the three silicone oil modifiers, coordinating their modifying effects, and avoiding some performance indicators failing to meet the standards.

[0012] According to some embodiments of the present invention, the viscosity of the methyl silicone oil is 80~500 mm. 4 / s (25℃); the viscosity of the hydroxyl silicone oil is 50~500cSt (25℃); the viscosity of the vinyl silicone oil is 200~800mPa·s (25℃), and the vinyl content is 5.4~6.0wt%.

[0013] According to some embodiments of the present invention, the specific surface area of ​​the fumed silica is 185~225 m². 2 / g; The fumed silica is premixed with the hydroxyl silicone oil before use, and the treatment temperature is 40~60℃ for 20~40min.

[0014] According to some embodiments of the present invention, the average particle size of the aluminum hydroxide is 1~3 μm.

[0015] According to some embodiments of the present invention, the silane coupling agent includes at least one of vinyltrimethoxysilane or vinyltriethoxysilane.

[0016] According to some embodiments of the present invention, the vulcanizing agent includes 2,5-dimethyl-2,5-bis(tert-butylperoxy)hexane or bis(2,4-dichlorobenzoyl peroxide).

[0017] A second aspect of the present invention provides a method for preparing composite insulator silicone rubber as described in the first aspect of the present invention, comprising the following steps:

[0018] S1. Mix fumed silica and hydroxyl silicone oil at 40~60℃ for 20~40min to obtain surface-modified silica;

[0019] S2. Put the raw methyl vinyl silicone rubber into a mixer, add methyl silicone oil and vinyl silicone oil in sequence, and mix. Then add surface-modified silica, aluminum hydroxide, silane coupling agent and iron oxide, and mix at 50~70℃ under vacuum for 30~60 minutes.

[0020] S3. Cool the mixed rubber compound to below 60°C on a two-roll mill, add a vulcanizing agent, pass through thin sheets, and perform molding vulcanization to obtain composite insulator silicone rubber.

[0021] According to some embodiments of the present invention, in step S3, the vulcanization conditions are: temperature 160~180℃, pressure 8~15MPa, and time 10~20min.

[0022] The beneficial effects of this invention are:

[0023] (1) The silicone rubber of the present invention has an excellent balance of comprehensive performance: through the synergistic effect of three silicone oils and coupling agents, the contradiction between "flame retardancy-mechanical properties-processability-electrical properties" in high-filled flame-retardant silicone rubber is successfully resolved. When the ATH filling amount is as high as 100~130 phr, the material can still maintain excellent tensile strength (4.71 MPa) and tear strength (22.56 kN / m), while achieving the UL94 V-0 flame retardant rating;

[0024] (2) The silicone rubber of the present invention has excellent electrical insulation and leakage resistance: good filler dispersion and strong filler-matrix interface greatly reduce the micro-defects inside the material, giving it a high volume resistivity (1.98×10⁻⁶). 13 Ω·cm);

[0025] (3) The silicone rubber of the present invention has durable surface properties and aging resistance: by utilizing the controllable hydrophobic migration ability provided by methyl silicone oil, combined with a uniform and stable cross-linking network, the material can still maintain good surface hydrophobicity and mechanical property retention rate after long-term outdoor aging (ultraviolet, damp heat).

[0026] (4) The silicone rubber of the present invention has good processing adaptability: the lubricating effect of methyl silicone oil significantly improves the mixing and molding processing performance of high-filled rubber, reduces production energy consumption, and is suitable for large-scale industrial production.

[0027] Other features and advantages of the invention will be set forth in the description which follows, and will be apparent in part from the description, or may be learned by practicing the invention. Detailed Implementation

[0028] The following will describe the concept and technical effects of the present invention clearly and completely with reference to embodiments, so as to fully understand the purpose, features and effects of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are all within the scope of protection of the present invention.

[0029] Unless otherwise specified in the examples, the procedures should be performed under standard conditions or conditions recommended by the manufacturer. Reagents or instruments whose manufacturers are not specified are all commercially available products.

[0030] The raw material components used in the examples are shown in Table 1 below:

[0031] Example 1

[0032] This embodiment provides a synergistically reinforced composite insulator silicone rubber and its preparation method.

[0033] The components of this silicone rubber, by weight, are: 100 parts of methyl vinyl silicone rubber raw rubber, 120 parts of aluminum hydroxide, 30 parts of fumed silica, 3 parts of methyl silicone oil, 5 parts of hydroxyl silicone oil, 1.5 parts of vinyl silicone oil, 1 part of silane coupling agent, 0.2 parts of vulcanizing agent, and 2 parts of iron oxide.

[0034] Among them, the average particle size of aluminum hydroxide is 2 μm, and the specific surface area of ​​fumed silica is 200 m². 2 / g, the kinematic viscosity of methyl silicone oil is 200mm. 4 / s, the viscosity of the hydroxyl silicone oil is 200cSt and the hydroxyl content is 1.5wt%, the viscosity of the vinyl silicone oil is 500mPa·s and the vinyl content is 5.6wt%, the silane coupling agent is vinyltrimethoxysilane and the vulcanizing agent is 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane.

[0035] The preparation steps of this silicone rubber are as follows:

[0036] 1) Pretreatment: Weigh out fumed silica and hydroxyl silicone oil by weight, add them to a high-speed mixer, and mix at 50°C for 30 min to obtain hydroxyl silicone oil-coated modified silica.

[0037] 2) First stage mixing: Put the raw methyl vinyl silicone rubber into the internal mixer (initial temperature 45℃), add methyl silicone oil and vinyl silicone oil in sequence, and mix for 2 minutes; then add modified silica, aluminum hydroxide, silane coupling agent and iron oxide, raise the temperature of the internal mixer to 60℃, and mix under vacuum for 45 minutes until the rubber compound is uniform.

[0038] 3) Two-stage mixing and vulcanization: The above rubber compound is cooled to below 50°C on a two-roll mill, vulcanizing agent is added, and the mixture is passed through a thin mill 5 times to produce sheets; the rubber compound is placed in a mold and molded and vulcanized on a flat vulcanizing machine at 170°C and 12MPa for 15 minutes to obtain composite insulator silicone rubber.

[0039] Example 2

[0040] This embodiment provides synergistically reinforced composite insulator silicone rubber.

[0041] This embodiment is basically the same as Embodiment 1, except that the weight parts of each component are adjusted as follows: 100 parts of methyl vinyl silicone rubber raw rubber, 100 parts of aluminum hydroxide, 25 parts of fumed silica, 2 parts of methyl silicone oil, 6 parts of hydroxyl silicone oil, 1 part of vinyl silicone oil, 1.5 parts of silane coupling agent, 0.3 parts of vulcanizing agent, and 3 parts of iron oxide.

[0042] The final composite insulator silicone rubber was obtained.

[0043] Example 3

[0044] This embodiment provides synergistically reinforced composite insulator silicone rubber.

[0045] This embodiment is basically the same as Embodiment 1, except that the weight parts of each component are adjusted as follows: 100 parts of methyl vinyl silicone rubber raw rubber, 130 parts of aluminum hydroxide, 28 parts of fumed silica, 3 parts of methyl silicone oil, 4 parts of hydroxyl silicone oil, 2 parts of vinyl silicone oil, 1.8 parts of silane coupling agent, 0.2 parts of vulcanizing agent, and 2 parts of iron oxide.

[0046] The final composite insulator silicone rubber was obtained.

[0047] Example 4

[0048] This embodiment provides synergistically reinforced composite insulator silicone rubber.

[0049] This embodiment is basically the same as Embodiment 1, except that the weight parts of each component are adjusted as follows: 100 parts of methyl vinyl silicone rubber raw rubber, 120 parts of aluminum hydroxide, 30 parts of fumed silica, 1.5 parts of methyl silicone oil, 2.8 parts of hydroxyl silicone oil, 1.2 parts of vinyl silicone oil, 2 parts of silane coupling agent, 0.4 parts of vulcanizing agent, and 2 parts of iron oxide.

[0050] The final composite insulator silicone rubber was obtained.

[0051] Example 5

[0052] This embodiment provides synergistically reinforced composite insulator silicone rubber.

[0053] This embodiment is basically the same as Embodiment 1, except that the weight parts of each component are adjusted as follows: 100 parts of methyl vinyl silicone rubber raw rubber, 120 parts of aluminum hydroxide, 30 parts of fumed silica, 2.4 parts of methyl silicone oil, 5 parts of hydroxyl silicone oil, 2.5 parts of vinyl silicone oil, 2 parts of silane coupling agent, 0.3 parts of vulcanizing agent, and 3 parts of iron oxide.

[0054] The final composite insulator silicone rubber was obtained.

[0055] Example 6

[0056] This embodiment provides synergistically reinforced composite insulator silicone rubber.

[0057] This embodiment is basically the same as Embodiment 1, except that the weight parts of each component are adjusted as follows: 100 parts of methyl vinyl silicone rubber raw rubber, 120 parts of aluminum hydroxide, 30 parts of fumed silica, 3.5 parts of methyl silicone oil, 7 parts of hydroxyl silicone oil, 3 parts of vinyl silicone oil, 1.5 parts of silane coupling agent, 0.3 parts of vulcanizing agent, and 4 parts of iron oxide.

[0058] The final composite insulator silicone rubber was obtained.

[0059] Comparative Example 1

[0060] This comparative example provides synergistically reinforced composite insulator silicone rubber.

[0061] This comparative example is basically the same as Example 1, except that the weight parts of each component in this comparative example are adjusted as follows: 100 parts of methyl vinyl silicone rubber raw rubber, 110 parts of aluminum hydroxide, 25 parts of fumed silica, 0 parts of methyl silicone oil, 7.5 parts of hydroxyl silicone oil, 3.5 parts of vinyl silicone oil, 1 part of silane coupling agent, 0.2 parts of vulcanizing agent, and 3 parts of iron oxide.

[0062] The final composite insulator silicone rubber was obtained.

[0063] Comparative Example 2

[0064] This comparative example provides synergistically reinforced composite insulator silicone rubber.

[0065] This comparative example is basically the same as Example 1, except that the weight parts of each component in this comparative example are adjusted as follows: 100 parts of methyl vinyl silicone rubber raw rubber, 130 parts of aluminum hydroxide, 28 parts of fumed silica, 3 parts of methyl silicone oil, 0 parts of hydroxyl silicone oil, 3.2 parts of vinyl silicone oil, 1 part of silane coupling agent, 0.2 parts of vulcanizing agent, and 3 parts of iron oxide.

[0066] The final composite insulator silicone rubber was obtained.

[0067] Comparative Example 3

[0068] This comparative example provides synergistically reinforced composite insulator silicone rubber.

[0069] This comparative example is basically the same as Example 1, except that the weight parts of each component in this comparative example are adjusted as follows: 100 parts of methyl vinyl silicone rubber raw rubber, 100 parts of aluminum hydroxide, 30 parts of fumed silica, 3 parts of methyl silicone oil, 4 parts of hydroxyl silicone oil, 0 parts of vinyl silicone oil, 1 part of silane coupling agent, 0.2 parts of vulcanizing agent, and 3 parts of iron oxide.

[0070] The final composite insulator silicone rubber was obtained.

[0071] Performance testing:

[0072] The properties of the composite insulator silicone rubber prepared in each embodiment and comparative example were tested, specifically its tensile strength, elongation at break, tear strength, Shore A hardness, volume resistivity, surface resistivity, hydrophobic angle, dielectric constant, breakdown strength, and UL94 flame retardancy rating. The results are shown in Table 2 below.

[0073] The performance test results above show that this invention systematically solves the performance contradictions of highly filled flame-retardant silicone rubber through a ternary synergistic system of methyl silicone oil, hydroxyl silicone oil, and vinyl silicone oil. Specifically, hydroxyl silicone oil, as a structure control agent, constructs a robust reinforcing network through efficient dispersion and surface treatment of fumed silica, providing the material with excellent mechanical strength (tensile strength up to 4.71 MPa) and high volume resistivity (optimal 1.98 × 10⁻⁶). 13 The base is Ω·m); vinyl silicone oil, as a network modifier, introduces controllable crosslinking points to finely regulate the density and uniformity of the crosslinked network, thereby endowing the material with excellent elongation at break (up to 241%) and balanced hardness; methyl silicone oil, as a processing aid and functional migration source, provides controllable hydrophobic migration capability while ensuring good processing fluidity of the high-filling system, ensuring surface stability during long-term service.

[0074] The significant performance degradation in the comparative data, from the perspectives of processability, reinforcement, and toughness, respectively, indirectly confirms the indispensability of the three components. Ultimately, the formulation of Example 1, due to its precise balance across the functional windows of the three components, achieves high levels of all key properties (strength, toughness, hardness, and insulation) simultaneously, realizing optimal comprehensive performance that is difficult to achieve with a single component or binary system, fully demonstrating the synergistic inventiveness and technological advancement of this invention.

[0075] The embodiments of the present invention have been described in detail above. However, the present invention is not limited to the above embodiments. Within the scope of knowledge possessed by those skilled in the art, various changes can be made without departing from the spirit of the present invention. Furthermore, the embodiments of the present invention and the features thereof can be combined with each other unless otherwise specified.

Claims

1. A composite insulator silicone rubber, characterized in that, The components of the silicone rubber, by weight, include: 80-120 parts of methyl vinyl silicone rubber raw rubber, 100-130 parts of aluminum hydroxide, 22-32 parts of fumed silica, 1.5-3.5 parts of methyl silicone oil, 2.5-7 parts of hydroxyl silicone oil, 1-3 parts of vinyl silicone oil, 1-2.5 parts of silane coupling agent, 0.2-0.4 parts of vulcanizing agent, and 2-4 parts of iron oxide.

2. The composite insulator silicone rubber according to claim 1, characterized in that, The methyl vinyl silicone rubber raw material has a vinyl content of 0.1~0.2wt% and a molecular weight of 4×10⁻⁶. 5 ~9×10 5 .

3. The composite insulator silicone rubber according to claim 1, characterized in that, The weight ratio of the methyl silicone oil, hydroxyl silicone oil and vinyl silicone oil is (0.8~1.5):(2~4):

1.

4. The composite insulator silicone rubber according to claim 1, characterized in that, The viscosity of the methyl silicone oil is 80~500 mm. 4 / s (25℃); the viscosity of the hydroxyl silicone oil is 50~500cSt (25℃); the viscosity of the vinyl silicone oil is 200~800mPa·s (25℃), and the vinyl content is 5.4~6.0wt%.

5. The composite insulator silicone rubber according to claim 1, characterized in that, The specific surface area of ​​the fumed silica is 185~225 m². 2 / g; The fumed silica is premixed with the hydroxyl silicone oil before use, and the treatment temperature is 40~60℃ for 20~40min.

6. The composite insulator silicone rubber according to claim 1, characterized in that, The average particle size of the aluminum hydroxide is 1~3μm.

7. The composite insulator silicone rubber according to claim 1, characterized in that, The silane coupling agent includes at least one of vinyltrimethoxysilane or vinyltriethoxysilane.

8. The composite insulator silicone rubber according to claim 1, characterized in that, The vulcanizing agent includes 2,5-dimethyl-2,5-bis(tert-butylperoxy)hexane or bis(2,4-dichlorobenzoyl peroxide).

9. The method for preparing composite insulator silicone rubber according to any one of claims 1 to 8, characterized in that, Includes the following steps: S1. Mix fumed silica and hydroxyl silicone oil at 40~60℃ for 20~40min to obtain surface-modified silica; S2. Put the raw methyl vinyl silicone rubber into a mixer, add methyl silicone oil and vinyl silicone oil in sequence, and mix. Then add surface-modified silica, aluminum hydroxide, silane coupling agent and iron oxide, and mix at 50~70℃ under vacuum for 30~60 minutes. S3. Cool the mixed rubber compound to below 60°C on a two-roll mill, add a vulcanizing agent, pass through thin sheets, and perform molding vulcanization to obtain composite insulator silicone rubber.

10. The preparation method according to claim 9, characterized in that, In step S3, the vulcanization conditions are: temperature 160~180℃, pressure 8~15MPa, and time 10~20min.

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