Modified silicone rubber composite material and preparation method thereof, sealing product and oil immersed capacitor

Abstract

The invention provides a modified silicone rubber composite material and a preparation method thereof, a sealing product and an oil immersed capacitor. The modified silicone rubber composite material is prepared from the following preparation raw materials in parts by mass: 60 parts of methyl phenyl silicone rubber, 22 to 26 parts of filler, 2.2 to 2.6 parts of a structure control agent, 0.7 to 0.9 part of a free radical initiator and 0.12 to 0.42 part of 2-phenyl acrylonitrile. The modified silicone rubber composite material has excellent insulating property and has good compatibility with insulating oil.

Description

Technical Field

[0001] This application relates to the field of silicone rubber materials technology, and in particular to a modified silicone rubber composite material and its preparation method, sealing products, and oil-immersed capacitors. Background Technology

[0002] With the rapid development of power systems, capacitors, as an important component of power systems, play a crucial role in reactive power compensation and power factor correction. Their reliability is essential for the safe and stable operation of the entire power system. Oil-immersed capacitors are an important type of capacitor with a wide range of applications, playing a vital role in high-voltage, long-distance, and large-capacity applications.

[0003] Silicone rubber, with its excellent elasticity, hydrophobicity, and insulation properties, is widely used as a sealing and insulating material for oil-immersed capacitors. Compared to traditional silicone rubber, phenyl silicone rubber (PVMQ) exhibits stronger resistance to extreme conditions, making it well-suited for manufacturing sealing and insulating materials for capacitors operating in increasingly complex environments. As a critical component connecting the capacitor to the external environment, the insulation reliability of the sealing and insulating material plays a vital role in the stable operation of the capacitor. The complex operating conditions of oil-immersed capacitors necessitate that the sealing and insulating material possess excellent insulation performance; simultaneously, the heat generated by the capacitor during long-term operation keeps the insulating oil in the tank at a consistently high temperature, thus also placing demands on the thermal stability of the sealing and insulating material.

[0004] In traditional technology, capacitor insulating oil is usually mineral oil, which has the advantages of low cost and excellent performance, but also has disadvantages such as being difficult to degrade and causing significant pollution. Natural ester insulating oil, on the other hand, is almost pollution-free to the environment and has excellent insulation and safety performance, so its application in oil-immersed capacitors has become increasingly widespread in recent years; however, there is a problem of poor compatibility between capacitor sealing insulation materials and natural ester insulating oil, which affects the service life and safety of the capacitor. Summary of the Invention

[0005] Based on this, one or more embodiments of this application provide a modified silicone rubber composite material with good compatibility with natural ester insulating oil, a method for preparing the same, a sealing product, and an oil-immersed capacitor.

[0006] According to a first aspect of the embodiments of this application, a modified silicone rubber composite material is provided, comprising the following raw materials by mass: 60 parts of methylphenyl silicone rubber, 22-26 parts of filler, 2.2-2.6 parts of structure control agent, 0.7-0.9 parts of free radical initiator, and 0.12-0.42 parts of 2-phenylacrylonitrile.

[0007] In one embodiment, the structure control agent includes one or more of hexamethyldisilazane, hydroxyl-terminated polydimethylsiloxane, and diphenyldihydroxysilane.

[0008] In one embodiment, the free radical initiator includes a sulfurizing agent;

[0009] Optionally, the vulcanizing agent includes one or more of di-tert-butyl peroxide, dicumyl peroxide, and 2,4-dichlorobenzoyl peroxide.

[0010] In one embodiment, the filler comprises silica.

[0011] A method for preparing a modified silicone rubber composite material includes the following steps:

[0012] The above-mentioned raw materials for preparing the modified silicone rubber composite material are provided, and the raw materials are mixed to obtain a premix.

[0013] The premix is ​​subjected to vulcanization treatment to obtain the modified silicone rubber composite material.

[0014] In one embodiment, the mixing process includes the following steps:

[0015] The methylphenyl silicone rubber is subjected to open milling to prepare a first compound;

[0016] The first compound, the filler, and the structure control agent are first compounded to prepare a second compound.

[0017] The second compound, the free radical initiator, and the 2-phenylacrylonitrile are subjected to a second compounding to prepare a premix.

[0018] In one embodiment, the vulcanization treatment includes a first vulcanization treatment and a second vulcanization treatment performed sequentially;

[0019] The temperature of the first vulcanization treatment is 165℃~175℃, the time is 17min~23min, and the pressure is 14MPa~15MPa.

[0020] The second vulcanization treatment is carried out at a temperature of 195℃~205℃ for 3h~5h.

[0021] In one embodiment, after the premix is ​​vulcanized, the following step is further included: the vulcanized premix is ​​left to stand at room temperature for 20h to 28h.

[0022] According to a second aspect of the embodiments of this application, a sealing article is provided, comprising the modified silicone rubber composite material described above or the modified silicone rubber composite material prepared by the above-described method.

[0023] According to a third aspect of the embodiments of this application, an oil-immersed capacitor is provided, including the sealing article described above.

[0024] Compared with traditional technologies, this application has the following advantages:

[0025] In the modified silicone rubber composite material of this application, the free radical initiator decomposes to generate tert-butoxy free radicals, which attack the vinyl or methyl groups on the side chains of methylphenyl silicone rubber molecules, generating silicone rubber macromolecular free radicals. Simultaneously, the tert-butoxy free radicals attack the vinyl and carbon-nitrogen triple bonds on 2-phenylacrylonitrile, undergoing a free radical addition reaction to generate 2-phenylacrylonitrile free radicals. When the silicone rubber macromolecular free radicals encounter the 2-phenylacrylonitrile free radicals, a stable covalent bond is formed through coupling termination. This gives the modified silicone rubber composite material a stable cross-linked network structure, thereby improving its insulation and mechanical properties. Furthermore, the introduction of polar groups such as cyano and phenyl groups can capture more freely moving electrons and reduce electron collisions with the molecular chains, thus altering the polarity of the modified silicone rubber composite material and improving its compatibility with insulating oils. Attached Figure Description

[0026] To more clearly illustrate the technical solutions of the specific embodiments of this application, the drawings used in the description of the specific embodiments 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 based on these drawings.

[0027] Figure 1 The infrared spectra of the modified silicone rubber composites prepared in Examples 1-3 and Comparative Example 1 before and after oil immersion are shown.

[0028] Figure 2 This is a schematic diagram of the chemical mechanism of crosslinking between 2-phenylacrylonitrile and methylphenyl silicone rubber. Detailed Implementation

[0029] To make the above-mentioned objectives, features, and advantages of this application more apparent and understandable, a detailed description of specific embodiments of this application is provided. Many specific details are set forth in the following description to provide a thorough understanding of this application. However, this application can be implemented in many other ways different from those described herein, and those skilled in the art can make similar modifications without departing from the spirit of this application. Therefore, this application is not limited to the specific embodiments disclosed below.

[0030] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. Unless otherwise specifically stated, all raw materials, reagents, instruments, and equipment used in this application are commercially available or can be prepared by existing methods.

[0031] The terms "and / or," "or / and," and "and / or" as used herein include any one of two or more of the related listed items, as well as any and all combinations of the related listed items. These arbitrary and all combinations include any two related listed items, any more related listed items, or a combination of all related listed items. It should be noted that when at least three items are connected by at least two conjunctions selected from "and / or," "or / and," and "and / or," it should be understood that in this application, the technical solution undoubtedly includes technical solutions connected by "logical AND," and also undoubtedly includes technical solutions connected by "logical OR." For example, "A and / or B" includes three parallel solutions: A, B, and A+B. For example, the technical solution of "A, and / or, B, and / or, C, and / or, D" includes any one of A, B, C, and D (that is, a technical solution that is connected by "logical OR"), as well as any and all combinations of A, B, C, and D, that is, combinations of any two or three of A, B, C, and D, and also combinations of all four of A, B, C, and D (that is, a technical solution that is connected by "logical AND").

[0032] In this application, the terms "multiple", "various", "multiple times", "multi-dimensional", etc., unless otherwise specified, refer to a quantity greater than or equal to 2. For example, "one or more" means one or more than or equal to two.

[0033] The terms “combinations of,” “any combination of,” and “any combination of” used in this article include all suitable combinations of any two or more of the listed items.

[0034] In this document, the term "suitable" as used in phrases such as "suitable combination," "suitable method," and "any suitable method" refers to the ability to implement the technical solution of this application, solve the technical problem of this application, and achieve the expected technical effect of this application.

[0035] In this application, terms such as "further," "even further," and "particularly" are used to describe purposes and indicate differences in content, but should not be construed as limiting the scope of protection of this application.

[0036] In this application, the terms "first aspect," "second aspect," "third aspect," "fourth aspect," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance or quantity, nor should they be construed as implicitly indicating the importance or quantity of the indicated technical features. Moreover, "first," "second," "third," "fourth," etc., serve only as a non-exhaustive enumeration and should be understood not to constitute a closed limitation on quantity.

[0037] In this application, the technical features described in an open-ended manner include both closed technical solutions consisting of the listed features and open technical solutions that include the listed features.

[0038] In this application, numerical intervals (i.e., numerical ranges) are involved. Unless otherwise specified, the selected numerical distributions within the aforementioned numerical intervals are considered continuous and include the two endpoints (i.e., the minimum and maximum values) of the numerical range, as well as every value between these two endpoints. Unless otherwise specified, when a numerical interval refers only to integers within that interval, it includes the two endpoint integers of the numerical range, as well as every integer between the two endpoints. In this document, this is equivalent to directly listing every integer. For example, if t is an integer selected from 1 to 10, it means that t is any integer selected from the group of integers consisting of 1, 2, 3, 4, 5, 6, 7, 8, 9, and 10. Furthermore, when multiple ranges are provided to describe features or characteristics, these ranges can be merged. In other words, unless otherwise specified, the ranges disclosed herein should be understood to include any and all subranges to which they are included.

[0039] Unless otherwise specified, the temperature parameters in this application are permitted to be either constant-temperature treatment or variations within a certain temperature range. It should be understood that the constant-temperature treatment allows temperature fluctuations within the precision range of the instrument control, such as ±5℃, ±4℃, ±3℃, ±2℃, or ±1℃.

[0040] In this application, "room temperature" or "normal temperature" generally refers to 4℃~35℃, for example, 20℃±5℃. In some embodiments of this application, "room temperature" or "normal temperature" refers to 10℃~30℃. In some embodiments of this application, "room temperature" or "normal temperature" refers to 20℃~30℃.

[0041] Some embodiments of this application provide a modified silicone rubber composite material, which, by mass parts, comprises the following raw materials: 60 parts of methylphenyl silicone rubber, 22-26 parts of filler, 2.2-2.6 parts of structure control agent, 0.7-0.9 parts of free radical initiator, and 0.12-0.42 parts of 2-phenylacrylonitrile.

[0042] In the modified silicone rubber composite material of this application, the free radical initiator can decompose to generate tert-butoxy free radicals, which attack the vinyl or methyl groups on the side chains of methylphenyl silicone rubber molecules, generating silicone rubber macromolecular free radicals. Simultaneously, the tert-butoxy free radicals attack the vinyl and carbon-nitrogen triple bonds on 2-phenylacrylonitrile, undergoing a free radical addition reaction to generate 2-phenylacrylonitrile free radicals. When the silicone rubber macromolecular free radicals encounter the 2-phenylacrylonitrile free radicals, a stable covalent bond is formed through coupling termination. This results in a stable cross-linked network structure, increased molecular chain density, and reduced free volume in the modified silicone rubber composite material, effectively blocking insulating oil molecules. The reduced free volume also effectively suppresses electron acceleration and weakens the impact of electrons on the molecular chains, thereby improving insulation performance. Furthermore, the increased cross-linking density of the modified silicone rubber composite material enhances its mechanical properties.

[0043] Incorporating 2-phenylacrylonitrile, containing a cyano group, carbon-carbon double bonds, and a benzene ring, into silicone rubber can improve its breakdown performance over a wider temperature range. Specifically, the cyano group is a strongly polar group, and the imine bond (C=N) formed after the reaction is also a strongly polar group. Introduced into silicone rubber, it can form deep traps within the material, capturing electrons and reducing the probability of collisional ionization. The phenyl group, with its large volume, effectively provides steric hindrance to accelerated electrons, reducing the acceleration distance. Simultaneously, the phenyl group also provides a good buffering effect against collisions of high-energy electrons. Increased crosslinking reduces the free volume within the material, decreasing electron injection and transport, thereby improving breakdown performance.

[0044] As an example, the mass fraction of the filler can be 22, 23, 24, 25, or 26 parts, or any value within the range formed by any two of the above points.

[0045] In some of these embodiments, the filler includes silica.

[0046] Furthermore, the filler also includes one or more of aluminum hydroxide and ceramic fillers.

[0047] As an example, the mass fraction of the structure control agent can be 2.2 parts, 2.3 parts, 2.4 parts, 2.5 parts, 2.6 parts, or any value within the range formed by any two of the above point values.

[0048] In some embodiments, the structure control agent includes one or more of hexamethyldisilazane, hydroxyl-terminated polydimethylsiloxane, and diphenyldihydroxysilane.

[0049] As an example, the mass fraction of the free radical initiator can be 0.7 parts, 0.8 parts, 0.9 parts, or any value within the range formed by any two of the above point values.

[0050] In some of these embodiments, the free radical initiator includes a sulfiding agent.

[0051] Furthermore, the vulcanizing agent includes one or more of di-tert-butyl peroxide, dicumyl peroxide, and 2,4-dichlorobenzoyl peroxide.

[0052] As an example, the mass fractions of 2-phenylacrylonitrile can be 0.12 parts, 0.13 parts, 0.14 parts, 0.15 parts, 0.16 parts, 0.17 parts, 0.18 parts, 0.19 parts, 0.2 parts, 0.21 parts, 0.22 parts, 0.23 parts, 0.24 parts, 0.25 parts, 0.26 parts, 0.27 parts, 0.28 parts, 0.29 parts, 0.3 parts, 0.31 parts, 0.32 parts, 0.33 parts, 0.34 parts, 0.35 parts, 0.36 parts, 0.37 parts, 0.38 parts, 0.39 parts, 0.4 parts, 0.41 parts, or 0.42 parts, or any value within the range formed by any two of the above point values.

[0053] Further, the mass fraction of 2-phenylacrylonitrile is 0.2 to 0.35 parts; even further, the mass fraction of 2-phenylacrylonitrile is 0.3 parts.

[0054] With increasing 2-phenylacrylonitrile content, the crosslinking reaction between it and methylphenyl silicone rubber becomes more intense, thereby promoting the degree of crosslinking in the modified silicone rubber composite material. This reduces the internal free volume, decreases the distance between molecular chains, restricts electron movement within the material, shortens the free path, reduces the generation of high-energy electrons, and weakens the impact of electrons on the molecular chains of the modified silicone rubber composite material. Simultaneously, with increasing 2-phenylacrylonitrile content, the number of introduced imine bonds also increases. These bonds exhibit significant electronegativity, forming numerous traps within the material and effectively capturing electrons, significantly inhibiting their free movement; thus, the insulation properties of the modified silicone rubber composite material are significantly improved.

[0055] If the content of 2-phenylacrylonitrile is too high, the cross-linking reaction will cause the distance between molecules to continue to decrease, and a large number of molecular chains will begin to aggregate, which will cause the electric field inside the modified silicone rubber composite material to be distorted and reduce its insulation performance.

[0056] In some embodiments, the phenyl content in the methylphenyl silicone rubber is 15% to 25% by mass.

[0057] As an example, the mass content of phenyl in methylphenyl silicone rubber can be 15%, 16%, 17%, 18%, 19%, 20%, 21%, 22%, 23%, 24%, 25%, or any value within the range of any two of the above points.

[0058] Some embodiments of this application also provide a method for preparing a modified silicone rubber composite material, including steps S10 and S20:

[0059] Step S10: Provide the raw materials for preparing the above-mentioned modified silicone rubber composite material, and perform a mixing treatment on the raw materials to obtain a premix;

[0060] Step S20: The premix is ​​vulcanized to obtain the modified silicone rubber composite material.

[0061] In some embodiments, the mixing process in step S10 includes the following steps:

[0062] Step S11: The methylphenyl silicone rubber is subjected to open milling to prepare the first compound;

[0063] Step S12: Perform a first compounding of the first compound, filler, and structure control agent to prepare a second compound;

[0064] Step S13: Perform a second compounding of the second compound, the free radical initiator, and 2-phenylacrylonitrile to prepare a premix.

[0065] In some embodiments, before the open milling of methylphenyl silicone rubber, the following steps are included: adjusting the two-roll gap of the open mill to 1.3 mm, controlling the speed ratio of the front roll to the rear roll to 1:1.2, and preheating the temperature of the roll shaft to 60°C.

[0066] In some embodiments, the mixing time for methylphenyl silicone rubber is 10 min to 15 min.

[0067] In some embodiments, the first compound, filler, and structure control agent are mixed for 30 minutes.

[0068] In some embodiments, before compounding the second compound, the free radical initiator, and 2-phenylacrylonitrile, the following step is included: placing the second compound at room temperature and pressure for 22-26 hours. It is understood that this period of time at room temperature and pressure allows the components to be fully mixed with the methylphenyl silicone rubber.

[0069] In some embodiments, the mixing time for the second compound, the free radical initiator, and 2-phenylacrylonitrile is 10 min to 15 min.

[0070] In some embodiments, the vulcanization treatment includes a first vulcanization treatment and a second vulcanization treatment performed sequentially;

[0071] The temperature of the first vulcanization treatment is 165℃~175℃, the time is 17min~23min, and the pressure is 14MPa~15MPa.

[0072] The second vulcanization treatment is carried out at a temperature of 195℃~205℃ for 3h~5h.

[0073] As an example, the temperature of the first vulcanization treatment can be 165℃, 166℃, 167℃, 168℃, 169℃, 170℃, 171℃, 172℃, 173℃, 174℃, or 175℃; the time of the first vulcanization treatment can be 17min, 18min, 19min, 20min, 21min, 22min, or 23min; the pressure of the first vulcanization treatment can be 14MPa, 14.1MPa, 14.2MPa, 14.3MPa, 14.4MPa, 14.5MPa, 14.6MPa, 14.7MPa, 14.8MPa, 14.9MPa, or 15MPa; or any value within the range formed by any two of the above points.

[0074] As an example, the temperature of the second vulcanization treatment can be 195℃, 196℃, 197℃, 198℃, 199℃, 200℃, 201℃, 202℃, 203℃, 204℃, or 205℃; the time of the second vulcanization treatment can be 3h, 4h, or 5h; or any value within the range formed by any two of the above point values.

[0075] In some embodiments, after the premix is ​​vulcanized, the following step is further included: the vulcanized premix is ​​left to stand at room temperature for 20h to 28h.

[0076] As an example, the resting time can be 20h, 21h, 22h, 23h, 24h, 25h, 26h, 27h, 28h, or any value within the range formed by any two of the above points.

[0077] Some embodiments of this application also provide a sealing article comprising the modified silicone rubber composite material described above or the modified silicone rubber composite material prepared by the above-described method.

[0078] Some embodiments of this application also provide an oil-immersed capacitor, including the sealing article described above.

[0079] Sealing products containing the above-mentioned modified silicone rubber composite material have good compatibility with natural ester insulating oil, and are not prone to mutual corrosion, degradation or performance deterioration during the operation of oil-immersed capacitors.

[0080] The present application will be further described below with reference to specific embodiments and comparative examples, but these should not be construed as limiting the scope of protection of the present application. Unless otherwise specified, the raw materials involved in the following specific embodiments are all commercially available, the instruments used are all commercially available, and the processes involved are conventionally selected by those skilled in the art unless otherwise specified.

[0081] Example 1

[0082] (1) Adjust the roller pitch of the two rollers of the open mill to 1.3 mm, and operate the front and rear rollers at a constant speed ratio of 1:1.2. After preheating the roller shaft to 60°C, add 60 g of methyl phenyl silicone rubber to the open mill and mill for 10 min until the methyl phenyl silicone rubber is evenly coated on the roller shaft. The methyl phenyl silicone rubber is IOTA 3120 (Ph-20%), which was purchased from Anhui Aiyota Silicone Oil Co., Ltd.

[0083] (2) Add 24g of silica and 2.4g of structure control agent (hexamethyldisilazane) to the open mill in sequence, mix for 30min until silica is evenly distributed, and prepare the compound.

[0084] (3) The prepared compound was placed at room temperature for 24 hours to ensure that each component was fully mixed with the silicone rubber matrix.

[0085] (4) Adjust the roller distance of the two rollers of the open mill to 1.3 mm, and operate the front and rear rollers at a constant speed ratio of 1:1.2. After preheating the roller shaft to 60°C, add the prepared compound to the open mill and mix for 15 min to remove the gas. Then add 0.9 g of free radical initiator (di-tert-butyl oxide) and 0.12 g of 2-phenylacrylonitrile to the compound and mix for 15 min.

[0086] (5) Take out the compound and cool it to room temperature. Add an appropriate amount of the prepared compound to a polyester film mold with dimensions of 100mm x 100mm x 0.175mm. Set the temperature of the flat vulcanizing machine to 170℃ and the pressure to 15MPa for vulcanization. The vulcanization time is 20min.

[0087] (6) The compound after primary vulcanization is placed in a 200℃ forced-air oven for secondary vulcanization for 4 min to obtain the composite material after secondary vulcanization; the composite material after secondary vulcanization is left to stand at room temperature for 24 h to prepare the modified silicone rubber composite material.

[0088] Example 2

[0089] The example is basically the same as Example 1, except that the mass of 2-phenylacrylonitrile is different in step (4); specifically, the mass of 2-phenylacrylonitrile in Example 2 is 0.3g.

[0090] Example 3

[0091] The example is basically the same as Example 1, except that the mass of 2-phenylacrylonitrile is different in step (4); specifically, the mass of 2-phenylacrylonitrile in Example 3 is 0.42g.

[0092] Comparative Example 1

[0093] (1) Adjust the roller pitch of the two rollers of the open mill to 1.3 mm, and operate the front and rear rollers at a constant speed ratio of 1:1.2. After preheating the roller shaft to 60°C, add 60 g of methyl phenyl silicone rubber to the open mill and mill for 10 min until the methyl phenyl silicone rubber is evenly coated on the roller shaft. The methyl phenyl silicone rubber is IOTA 3120 (Ph-20%), which was purchased from Anhui Aiyota Silicone Oil Co., Ltd.

[0094] (2) Add 24g of silica and 2.4g of structure control agent (hexamethyldisilazane) to the open mill in sequence, mix for 30min until silica is evenly distributed, and prepare the compound.

[0095] (3) The prepared compound was placed at room temperature for 24 hours to ensure that each component was fully mixed with the silicone rubber matrix.

[0096] (4) Adjust the roller distance of the two rollers of the open mill to 1.3 mm, and operate the front and rear rollers at a constant speed ratio of 1:1.2. After preheating the roller shaft to 60°C, add the prepared compound to the open mill and mix for 15 min to remove the gas; then add 0.9 g of free radical initiator (di-tert-butyl oxide) to the compound and mix for 15 min.

[0097] (5) Take out the compound and cool it to room temperature. Add an appropriate amount of the prepared compound to a polyester film mold with dimensions of 100mm x 100mm x 0.175mm. Set the temperature of the flat vulcanizing machine to 170℃ and the pressure to 15MPa for vulcanization. The vulcanization time is 20min.

[0098] (6) The compound after primary vulcanization is placed in a 200℃ forced-air oven for secondary vulcanization for 4 min to obtain the composite material after secondary vulcanization; the composite material after secondary vulcanization is left to stand at room temperature for 24 h to prepare the modified silicone rubber composite material.

[0099] Comparative Example 2

[0100] It is basically the same as Example 1, except that 2-phenylacrylonitrile in step (4) is replaced with an equal mass of cinnamonitrile.

[0101] The modified silicone rubber composite materials prepared in the above examples and comparative examples were poured into petri dishes, and then natural ester insulating oil was poured in until the samples were completely submerged. The petri dishes were placed in a nitrogen atmosphere and kept at room temperature in the dark for 24 hours. The samples immersed in the insulating oil were taken out, the surface oil stains were wiped clean, and the samples were placed in a nitrogen atmosphere and kept at room temperature in the dark for 24 hours to obtain the modified silicone rubber composite material after oil immersion treatment.

[0102] According to GB / T 1408.2-2016 / IEC 60243-2:2013, the breakdown strength of the modified silicone rubber composite material before and after oil impregnation was tested at 30℃, 50℃, and 70℃. The results are shown in Table 1.

[0103] Table 1

[0104]

[0105] As shown in Table 1, crosslinking modification with 2-phenylacrylonitrile can effectively improve the breakdown strength of silicone rubber under different temperature conditions. Furthermore, as the content of 2-phenylacrylonitrile increases, the breakdown strength first increases and then decreases. When the content of 2-phenylacrylonitrile is 0.5 wt% of methylphenyl silicone rubber, the modified silicone rubber composite material prepared has the highest breakdown strength.

[0106] As the temperature increases, the breakdown strength of the modified silicone rubber prepared in each embodiment and comparative example decreases. This is because the increase in temperature promotes the thermal motion of molecules, enhances the mobility of the polymer long chains, overcomes the entanglement between the original molecular chains, and increases the free volume inside the material, providing a longer free path for electron acceleration. Furthermore, the high temperature itself increases the energy of electrons, increasing the probability of high-energy electrons impacting the molecular chains.

[0107] Further comparison of the breakdown strength of the same sample before and after oil immersion treatment at the same temperature reveals that the breakdown strength of the modified silicone rubber composite material increases after oil immersion. This is because, during the immersion process, some insulating oil molecules penetrate into the interior of the composite material's molecular chains, repairing internal defects and reducing electric field distortion. Simultaneously, the presence of numerous ester groups in the insulating oil molecules introduces more traps into the material, creating a stronger trapping effect on freely moving electrons, thus improving the composite material's breakdown performance.

[0108] Comparing methylphenyl silicone rubber modified with cinnamonitrile crosslinking, it can be seen that the breakdown performance of the modified materials is superior to that of the pure materials, with the 2-phenylacrylonitrile-modified sample exhibiting even better performance. Although the two are isomers, their group positions differ: the carbon-carbon double bond of 2-phenylacrylonitrile is an isolated alkene bond located at the molecule's end; while the alkene bond of cinnamonitrile is located inside the molecule. Comparatively, the carbon-carbon double bond of 2-phenylacrylonitrile has stronger reactivity, resulting in a higher crosslinking efficiency. Simultaneously, the orderly arrangement of the cinnamonitrile molecular groups facilitates π-π conjugation, creating additional electron transport paths and reducing breakdown performance. Therefore, the 2-phenylacrylonitrile-modified sample exhibits better performance.

[0109] Figure 1 The images show the infrared spectra of the modified silicone rubber composites prepared in Examples 1-3 and Comparative Example 1 before and after oil impregnation treatment. This is because 2-phenylacrylonitrile undergoes the following reaction under the catalysis of a free radical initiator: Figure 2 The reaction is shown; while 2-phenylacrylonitrile itself has significant characteristic peaks, including one located at 2240 cm⁻¹. -1 The cyanide bond (C≡N) is located at 1640 cm⁻¹. -1 The carbon-carbon double bond (C=C). Figure 1 The modified silicone rubber composite material was shown to be 2240 cm⁻¹ -1 The absence of an absorption peak at 1640 cm⁻¹ indicates that the nitrile group introduced into 2-phenylacrylonitrile has fully reacted with the silicone rubber backbone; as the content of 2-phenylacrylonitrile increases, the absorption peak at 1640 cm⁻¹ increases. -1 The absorption peak showed almost no change, indicating that the carbon-carbon double bond introduced by 2-phenylacrylonitrile had fully reacted with the silicone rubber backbone. The oil-impregnated sample showed a peak at 1750 cm⁻¹. -1 The appearance of a new absorption peak indicates that the natural ester insulating oil molecules entered the modified silicone rubber composite material after impregnation. There are a large number of ester groups in the insulating oil molecules, and the carbon-oxygen double bonds (C=O) in them cause the corresponding absorption peaks to appear in the composite medium.

[0110] The contact angles of the modified silicone rubber composites prepared in Examples 1-3 and Comparative Example 1 with pure silicone rubber before and after oil immersion treatment were further tested, and the results are shown in Table 2.

[0111] Table 2

[0112]

[0113] Table 2 shows that with increasing 2-phenylacrylonitrile addition, the contact angle of the modified silicone rubber composite material with natural ester insulating oil increases, resulting in better compatibility. As the amount of 2-phenylacrylonitrile increases, the crosslinking reaction with silicone rubber becomes more vigorous, thus promoting the degree of crosslinking in the composite material and reducing the distance between molecular chains. These molecular chain conformations can effectively block small molecules of external insulating oil. Simultaneously, the large benzene ring in 2-phenylacrylonitrile provides significant steric hindrance, also playing a certain role in blocking small molecules of insulating oil. The enhanced molecular chain polarity also contributes to improving the compatibility of the composite medium. Compared to the cinnamonitrile-modified sample, the 2-phenylacrylonitrile-modified sample exhibits better compatibility with insulating oil. This is because cinnamonitrile has a relatively low crosslinking efficiency and forms relatively longer crosslinked branches, resulting in less constraint on the molecular chains and easier swelling.

[0114] After oil impregnation, the contact angle of the modified silicone rubber composite material with natural ester insulating oil decreased, indicating a decline in their compatibility. Although the cross-linked structure provides some barrier effect against small molecules of the insulating oil, some insulating oil molecules still penetrate the interior of the modified silicone rubber composite material and adsorb onto its surface, making their polarity and surface energy closer to that of the oil, thus reducing the contact angle. Simultaneously, these molecules cause the molecular chains on the composite surface to expand and undergo a slight swelling effect, making the material surface smoother and further reducing the contact angle of the composite medium with the natural ester insulating oil.

[0115] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0116] The embodiments described above are merely illustrative of several implementation methods of this application, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this application should be determined by the appended claims.

Claims

1. A modified silicone rubber composite material, characterized in that, The raw materials, by mass, include the following: 60 parts of methylphenyl silicone rubber, 22-26 parts of filler, 2.2-2.6 parts of structure control agent, 0.7-0.9 parts of free radical initiator, and 0.12-0.42 parts of 2-phenylacrylonitrile.

2. The modified silicone rubber composite material according to claim 1, characterized in that, The structure control agent includes one or more of hexamethyldisilazane, hydroxyl-terminated polydimethylsiloxane, and diphenyldihydroxysilane.

3. The modified silicone rubber composite material according to claim 1, characterized in that, The free radical initiator includes a sulfurizing agent; Optionally, the vulcanizing agent includes one or more of di-tert-butyl peroxide, dicumyl peroxide, and 2,4-dichlorobenzoyl peroxide.

4. The modified silicone rubber composite material according to any one of claims 1 to 3, characterized in that, The filler includes silica.

5. A method for preparing a modified silicone rubber composite material, characterized in that, Includes the following steps: The raw materials for preparing the modified silicone rubber composite material according to any one of claims 1 to 4 are provided, and the raw materials are subjected to a mixing treatment to obtain a premix; The premix is ​​subjected to vulcanization treatment to obtain the modified silicone rubber composite material.

6. The method for preparing the modified silicone rubber composite material according to claim 5, characterized in that, The mixing process includes the following steps: The methylphenyl silicone rubber is subjected to open milling to prepare a first compound; The first compound, the filler, and the structure control agent are first compounded to prepare a second compound. The second compound, the free radical initiator, and the 2-phenylacrylonitrile are subjected to a second compounding to prepare a premix.

7. The method for preparing the modified silicone rubber composite material according to claim 5, characterized in that, The vulcanization process includes a first vulcanization process and a second vulcanization process performed sequentially. The temperature of the first vulcanization treatment is 165℃~175℃, the time is 17min~23min, and the pressure is 14MPa~15MPa. The second vulcanization treatment is carried out at a temperature of 195℃~205℃ for 3h~5h.

8. The method for preparing the modified silicone rubber composite material according to any one of claims 5 to 7, characterized in that, After the premix is ​​vulcanized, the following step is also included: the vulcanized premix is ​​left to stand at room temperature for 20h~28h.

9. A sealing product, characterized in that, The modified silicone rubber composite material includes the modified silicone rubber composite material prepared by any one of claims 1 to 4 or any one of claims 5 to 8.

10. An oil-immersed capacitor, characterized in that, Includes the sealing article as described in claim 9.

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