Nonlinear conductive silicone rubber based on multi-oxide sintered body doping as well as preparation method and application of nonlinear conductive silicone rubber

Abstract

The invention discloses nonlinear conductive silicone rubber based on multi-oxide sintered body doping and a preparation method and application thereof, and belongs to the technical field of cable accessory materials. The invention discloses nonlinear conductive silicone rubber based on multi-oxide sintered body doping. The nonlinear conductive silicone rubber is metal oxide modified silicone rubber; the metal oxide comprises ZnO, Bi2O3, MnO2, Co2O3 and Cr2O3, and the metal oxide comprises ZnO, Bi2O3, MnO2, Co2O3 and Cr2O3; the silicon rubber is silicon rubber grafted with cinnamyl nitrile. According to the invention, Bi2O3 is used as a resistance changing agent to form a thin layer at a ZnO crystal boundary, so that the insulating property of the crystal boundary can be enhanced, the occurrence of breakdown voltage is reduced, and the voltage resistance of the material is improved; the MnO2 is doped into the silicon rubber, so that the potential barrier height can be increased at the ZnO crystal boundary, more charge transfer barriers are introduced at the crystal boundary of the material, the conductivity of the material is reduced, and the electrical insulating property of the silicon rubber is improved. The invention relates to application of nonlinear conductive silicone rubber based on multi-oxide sintered body doping in the field of power transmission and power distribution.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of cable accessory materials, and particularly relates to a nonlinear conductive silicone rubber based on multi-oxide sintered body doping and a preparation method and application thereof. BACKGROUND

[0002] The cable accessory is a key component for connecting the cable and the power equipment and realizing the power transmission, and the insulation performance thereof directly determines the safe and stable operation of the power system. With the development of the power system in the direction of high voltage, large capacity and intelligentization, the problems of electric field distortion, local overheating and aging failure faced by the cable accessory insulation are increasingly prominent, which can seriously affect the insulation performance of the cable accessory and reduce the service life thereof.

[0003] The traditional insulation material cannot intervene in the electric field distribution because the conductive characteristic thereof is linear, the local electric field can reach 3-5 times of the average electric field, far exceeding the tolerance limit of the material, and is easy to cause partial discharge or breakdown; the accumulation of space charge is the core inducement of the electrical aging of the cable accessory insulation, and when the traditional insulation material is subjected to high stress, the electric charge is easy to be injected into the polymer and accumulated, and then the internal electric field distribution of the insulation is uneven. Due to the combined action of the space charge accumulation, the partial discharge and the electrical tree, the insulation performance of the polymer is reduced, the aging of the insulation material is accelerated, and the service life of the cable is shortened.

[0004] At present, most of the methods are to dope pure zinc oxide in the silicone rubber to improve the nonlinear conductive characteristic of the silicone rubber, but the nonlinear conduction voltage of the pure zinc oxide is relatively fixed, and the pure zinc oxide is easy to agglomerate under long-term electric field or high temperature, resulting in the drift of the conductive characteristic, and the addition of too much pure zinc oxide will also increase the dielectric loss of the silicone rubber, and the doping of multiple oxides in the zinc oxide can adjust the barrier height of the grain boundary of the zinc oxide, so that the switching threshold of the silicone rubber under low field and high field is more in line with the actual demand, and the problems of too large leakage current under low field or inability to dissipate the concentrated electric field under high field are avoided. SUMMARY

[0005] One of the purposes of the application is to improve the uniform electric field distribution of the silicone rubber and reduce the ability of the high local electric field strength, so as to ensure the operation stability of the cable accessory under high electric field environment; the second purpose is to improve the nonlinear conductive characteristic of the silicone rubber, hinder the injection and accumulation of the electric charge in the insulation, and improve the service life of the cable material; the third purpose is to optimize the key parameters of the modified silicone rubber, so that the silicone rubber meets the electric field protection requirements of different scenes, and a nonlinear conductive silicone rubber based on multi-oxide sintered body doping and a preparation method and application thereof are provided.

[0006] A nonlinear conductive silicone rubber doped by a multi-oxide sintered body, which is a metal oxide modified silicone rubber; the metal oxide comprises ZnO, Bi2O3, MnO2, Co2O3 and Cr2O3; the silicone rubber is a silicone rubber grafted with cinnamyl cyanide;

[0007] The mass to volume ratio of the ZnO, Bi2O3, MnO2, Co2O3 and Cr2O3 to the silicone rubber grafted with cinnamyl cyanide is 26g:(0.16g~0.21g):(0.13g~0.18g):0.13g:0.13g:120mL.

[0008] A preparation method of a nonlinear conductive silicone rubber doped by a multi-oxide sintered body, which is completed according to the following steps:

[0009] I. Bi2O3, MnO2 and zinc acetate powder are added into deionized water, and continuous stirring is performed to obtain a mixed solution I;

[0010] II. Co2O3, Cr2O3 and sodium hydroxide powder are added into deionized water, and continuous stirring is performed to obtain a mixed solution II;

[0011] III. The mixed solution I is filtered through a water-based microporous filter membrane to obtain a filtered mixed solution I; the filtered mixed solution I is added into the constant-temperature and stirring mixed solution II at a constant speed, and after the addition is completed, a mixed solution III is obtained; the stirring is continued for a period of time, and then the lower precipitate is collected, centrifuged, washed and dried to obtain a reaction product;

[0012] IV. The reaction product is dried and ground into powder, and then placed into a muffle furnace, heated to a calcination temperature, kept at the temperature, and finally cooled to room temperature to obtain a metal oxide mixture containing ZnO;

[0013] V. Equal volumes of A component and B component of liquid silicone rubber are respectively added into a reactor; cinnamyl cyanide is divided into two equal masses, one of which is added into the A component of liquid silicone rubber, and stirred for a period of time to obtain a cinnamyl cyanide grafted silicone rubber A component; the other part of cinnamyl cyanide is added into the B component of liquid silicone rubber, and stirred for a period of time to obtain a cinnamyl cyanide grafted silicone rubber B component;

[0014] VI. The cinnamyl cyanide grafted silicone rubber A component is stirred, and then the metal oxide mixture containing ZnO is added under stirring, and stirred for a period of time to obtain a doped silicone rubber A component;

[0015] VII. The cinnamyl cyanide grafted silicone rubber B component is stirred, and then the metal oxide mixture containing ZnO is added under stirring, and stirred for a period of time to obtain a doped silicone rubber B component;

[0016] The mass of the cinnamon nitrile grafted silicone rubber A in step six is the same as that of the cinnamon nitrile grafted silicone rubber B component in step seven; the mass of the metal oxide mixture containing ZnO in step six is the same as that of the metal oxide mixture containing ZnO in step seven;

[0017] Eight, the doped silicone rubber A component and the doped silicone rubber B component are mixed and stirred for a period of time to obtain a metal oxide modified grafted cinnamon nitrile silicone rubber liquid;

[0018] The mass of the doped silicone rubber A component and the doped silicone rubber B component in step eight is the same;

[0019] The mass ratio of ZnO, Bi2O3, MnO2, Co2O3 and Cr2O3 in the metal oxide modified grafted cinnamon nitrile silicone rubber liquid in step eight to the volume of the grafted cinnamon nitrile silicone rubber liquid is 26g:(0.16g~0.21g):(0.13g~0.18g):0.13g:0.13g:120mL;

[0020] Nine, the metal oxide modified silicone rubber liquid is placed in a vacuum condition, stirred and vacuumed to remove air bubbles introduced into the silicone rubber during stirring to obtain an air bubble-free metal oxide modified silicone rubber liquid;

[0021] Ten, the air bubble-free metal oxide modified silicone rubber liquid is uniformly coated in a clean mold containing a release agent on the surface by using an automatic film coating machine at a constant rate; then the mold is smoothly moved into a flat vulcanizing machine, the mold is closed and matched vulcanization pressure and temperature parameters are set, and one-time vulcanization is completed within a preset time; after vulcanization is completed, the equipment is cooled to room temperature, the mold is opened and the product is taken out, and a one-time vulcanized composite medium is obtained;

[0022] Eleven, the one-time vulcanized composite medium is placed in a high-temperature air oven for secondary vulcanization to obtain a secondary vulcanized composite medium; the secondary vulcanized composite medium is placed at room temperature for a period of time to obtain a multi-oxide sintered body doped nonlinear conductive silicone rubber.

[0023] A multi-oxide sintered body doped nonlinear conductive silicone rubber is applied in the field of power transmission and distribution.

[0024] Principle of the application:

[0025] This invention innovates the ability of silicone rubber to homogenize electric field and controls the key parameters of dopants to make silicone rubber meet the requirements under different conditions. In this invention, Bi2O3 and MnO2 powders are added to zinc acetate and stirred, Co2O3 and Cr2O3 are added to sodium hydroxide solution, and the zinc acetate mixed solution is added to the sodium hydroxide mixed solution and stirred. After calcination, the precipitate is added to liquid grafted silicone rubber to obtain liquid-doped metal oxide grafted cinnamonitrile silicone rubber. The specific mechanism is as follows: (1) Since zinc acetate solution is acidic, it can help disperse oxides. Bi2O3 and MnO2 will react with Zn in zinc acetate. 2+ The ions form a soluble complex, but most of the oxides retain their oxidized state and react with Zn in subsequent sodium hydroxide treatments. 2+ (2) Co2O3 and Cr2O3 are added to sodium hydroxide solution respectively; the sodium hydroxide solution will provide an alkaline environment, so that these oxides can be converted into the corresponding metal hydroxides. Then, zinc acetate solution is added to sodium hydroxide solution to form Zn(OH)2 precipitate, and Co(OH)2 and Cr(OH)3 will precipitate together with Zn(OH)2; (3) Finally, after drying the wet precipitate, zinc hydroxide is sintered in muffle furnace to decompose and convert it into ZnO. Meanwhile, Co(OH)2 and Cr(OH)3 will be converted into CoO and Cr2O3, forming inclusions together with zinc oxide to obtain a metal oxide mixture containing ZnO; (4) In this preparation method, Bi2O3 will form a thin layer at the ZnO grain boundary, which helps to generate a Schottky barrier. MnO2 can adjust the height of the barrier at the grain boundary. Co2O3 and Cr2O3, as stabilizers, will regulate the crystal layer suitable for silicone rubber, enhance the interface stability. The thin layer of Bi2O3 at the grain boundary can change the resistance of the grain boundary, making it more stable and preventing the current from breaking down under overvoltage conditions. In addition, it will also improve the nonlinear conductivity of zinc oxide. After adding MnO2 to silicone rubber, more charge transport barriers may be introduced at the grain boundary of the material, increasing the difficulty of charge migration. The results show that the prepared modified silicone rubber has a breakdown electric field strength of 126~155KV / mm at 30℃; 115~143KV / mm at 50℃; and 110~139KV / mm at 70℃. At room temperature, the tensile strength can reach 12.06MPa.

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

[0027] I. This invention involves adding Bi₂O₃ and MnO₂ powders to zinc acetate and stirring, while adding Co₂O₃ and Cr₂O₃ separately to a sodium hydroxide solution. The zinc acetate mixture is then added to the sodium hydroxide mixture and stirred. After calcination, the resulting precipitate is added to liquid-grafted silicone rubber to obtain liquid-doped ZnO-grafted cinnamonitrile silicone rubber. Since the zinc acetate solution is acidic, it helps disperse the oxides, allowing Bi₂O₃ and MnO₂ to react with the ZnO in the zinc acetate. 2+ The ions form a soluble complex, but most of the oxides retain their oxidized state and react with Zn in subsequent sodium hydroxide treatments. 2+ A precipitate is formed by the co-precipitation of zinc oxide and zinc hydroxide. Simultaneously, Co₂O₃ and Cr₂O₃ are added to a sodium hydroxide solution. The sodium hydroxide solution provides an alkaline environment, allowing these oxides to convert into their corresponding metal hydroxides. Then, a zinc acetate solution is added to the sodium hydroxide solution, forming a Zn(OH)₂ precipitate, and Co(OH)₂ and Cr(OH)₃ precipitate together with the Zn(OH)₂. Finally, the wet precipitate is dried and sintered in a muffle furnace to decompose the zinc hydroxide, converting it into ZnO. Simultaneously, Co(OH)₂ and Cr(OH)₃ transform into CoO and Cr₂O₃, forming inclusions with zinc oxide to obtain ZnO doped with metal oxides. This preparation method causes the grain boundary layer existing on the zinc oxide surface to form a grain boundary barrier. Under low electric fields, charge carriers have difficulty overcoming the grain boundary barrier, resulting in extremely low conductivity. Under high electric fields, the strong electric field lowers the grain boundary barrier, allowing charge carriers to cross the barrier and form current, also exhibiting nonlinear conductivity. This causes the modified silicone rubber to exhibit nonlinear conductivity behavior in high field strength regions, with current density increasing exponentially with field strength, equivalent to active current shunting, smoothing out locally excessively high field strengths, and making the overall electric field distribution more uniform. The results show that the prepared modified silicone rubber can achieve a breakdown field strength of 155 KV / mm at 30℃; 143 KV / mm at 50℃; and 139 KV / mm at 70℃. The tensile strength at room temperature is 12.06 MPa.

[0028] II. This invention uses Bi2O3 as a resistive agent to form a thin layer at the grain boundaries of ZnO, which enhances the insulation of the grain boundaries and reduces the occurrence of breakdown voltage. This is because the conductivity of the grain boundary layer is regulated, reducing current leakage when passing through the grain boundaries, thereby improving the voltage withstand performance of the material. In ZnO materials, grain boundaries are often weak points for current breakdown. The thin layer of Bi2O3 at the grain boundaries can change the resistance of the grain boundaries, making them more stable and preventing breakdown under overvoltage conditions. By adjusting the conductivity of the grain boundaries, the presence of Bi2O3 can enhance the nonlinear resistive behavior of ZnO, making the material exhibit lower leakage current at high voltages and higher resistance at low voltages.

[0029] Third, doping MnO2 into silicone rubber increases the potential barrier height at the ZnO grain boundaries, introducing more charge transport barriers and making charge migration more difficult, which reduces its electrical conductivity. Increasing the potential barrier at the grain boundaries helps to prevent current flow, thereby improving the electrical insulation of silicone rubber. MnO2 generally has good chemical stability at high temperatures, thus enhancing the thermal stability of silicone rubber and maintaining its electrical properties more stably at high temperatures.

[0030] Fourth, this invention is simple to operate and suitable for large-scale production. The addition of ZnO will improve the nonlinear conductivity of silicone rubber, and the doped metal oxide can regulate the parameters of ZnO grain boundaries and improve heat resistance. It provides a new research and development idea for enhancing the electrical performance of cable accessories by strengthening silicone rubber as an auxiliary insulation. Attached Figure Description

[0031] Figure 1 (a) is the Weibull distribution diagram of the breakdown field strength of the composite media prepared in Examples 1-3 and Comparative Examples 1-2 at 30°C; (b) is the Weibull distribution diagram of the breakdown field strength of the composite media prepared in Examples 1-3 and Comparative Examples 1-2 at 50°C; and (c) is the Weibull distribution diagram of the breakdown field strength of the composite media prepared in Examples 1-3 and Comparative Examples 1-2 at 70°C.

[0032] Figure 2 (a) shows the change of electrical conductivity current with electric field strength at 30°C for the composite media prepared in Examples 1-3 and Comparative Examples 1-2; (b) shows the change of electrical conductivity current with electric field strength at 50°C for the composite media prepared in Examples 1-3 and Comparative Examples 1-2; and (c) shows the change of electrical conductivity current with electric field strength at 70°C for the composite media prepared in Examples 1-3 and Comparative Examples 1-2.

[0033] Figure 3 (a) is a line graph showing the tensile strength and elongation at break of the composite media prepared in Examples 1-3 and Comparative Examples 1-2 at 30°C; (b) is a line graph showing the tensile strength and elongation at break of the composite media prepared in Examples 1-3 and Comparative Examples 1-2 at 50°C; and (c) is a line graph showing the tensile strength and elongation at break of the composite media prepared in Examples 1-3 and Comparative Examples 1-2 at 70°C.

[0034] Figure 4 The graph shows the changes in thermal weight loss of the composite media prepared in Examples 1-3 and Comparative Examples 1-2 at 900°C.

[0035] Figure 5 The graphs show the thermal conductivity of the composite media prepared in Examples 1-3 and Comparative Examples 1-2 as a function of temperature.

[0036] Figure 6The relative permittivity-frequency curves of the composite media prepared in Examples 1-3 and Comparative Examples 1-2 are shown.

[0037] Figure 7 Simulation diagram of steady-state electric field distribution of ZnO and composite media prepared in Examples 1-3;

[0038] Figure 8 Infrared spectra of the composite media prepared in Examples 1-3 and Comparative Examples 1-2;

[0039] Figure 9 The upper figure shows the XRD patterns of the composite media prepared in Examples 1-3 and Comparative Example 1, while the lower figure shows the XRD patterns of the metal oxide mixtures containing ZnO in Examples 1-3 and Comparative Example 1. Detailed Implementation

[0040] Specific Implementation Method 1: This implementation method is a nonlinear conductive silicone rubber based on multi-oxide sintered body doping, which is a metal oxide modified silicone rubber; the metal oxides include ZnO, Bi2O3, MnO2, Co2O3 and Cr2O3; the silicone rubber is a silicone rubber grafted with cinnamonitrile.

[0041] The mass ratio of ZnO, Bi2O3, MnO2, Co2O3 and Cr2O3 to the volume ratio of the grafted cinnamonitrile silicone rubber is 26g:(0.16g~0.21g):(0.13g~0.18g):0.13g:0.13g:120mL.

[0042] Specific Implementation Method Two: This implementation method is a preparation method of nonlinear conductive silicone rubber based on multi-oxide sintered body doping, specifically completed according to the following steps:

[0043] 1. Add Bi2O3, MnO2 and zinc acetate powder to deionized water and stir continuously to obtain mixed solution I;

[0044] II. Add Co2O3, Cr2O3 and sodium hydroxide powder to deionized water and stir continuously to obtain mixed solution II;

[0045] 3. Filter mixed solution I through an aqueous microporous membrane to obtain filtered mixed solution I; add the filtered mixed solution I dropwise at a constant rate to mixed solution II which is kept at a constant temperature and stirred. After the addition is complete, mixed solution III is obtained. Continue stirring and reacting for a period of time, then let it stand, collect the lower precipitate, centrifuge, wash, and obtain the reaction product.

[0046] 4. The reaction product is dried, ground into powder, placed in a muffle furnace, heated to the calcination temperature, held at the temperature, and finally cooled to room temperature to obtain a metal oxide mixture containing ZnO.

[0047] 5. Add equal volumes of liquid silicone rubber components A and B to the reactor respectively; divide cinnamonitrile into two equal parts, add one part of cinnamonitrile to liquid silicone rubber component A, stir for a period of time to obtain cinnamonitrile-grafted silicone rubber component A; add the other part of cinnamonitrile to liquid silicone rubber component B, stir for a period of time to obtain cinnamonitrile-grafted silicone rubber component B.

[0048] 6. Stir the cinnamonitrile-grafted silicone rubber component A, then add a metal oxide mixture containing ZnO while stirring, and stir for a period of time to obtain the doped silicone rubber component A.

[0049] 7. Stir the cinnamonitrile-grafted silicone rubber B component, then add a metal oxide mixture containing ZnO under stirring conditions, stir for a period of time, and obtain the doped silicone rubber B component.

[0050] The cinnamonitrile-grafted silicone rubber A mentioned in step six has the same mass as the cinnamonitrile-grafted silicone rubber B mentioned in step seven; the ZnO-containing metal oxide mixture mentioned in step six has the same mass as the ZnO-containing metal oxide mixture mentioned in step seven.

[0051] 8. Mix the doped silicone rubber component A and the doped silicone rubber component B, stir for a period of time, and obtain a silicone rubber liquid modified with metal oxide and grafted with cinnamonitrile.

[0052] The doped silicone rubber A component and the doped silicone rubber B component mentioned in step eight have the same mass;

[0053] In step eight, the mass ratio of ZnO, Bi2O3, MnO2, Co2O3, and Cr2O3 in the metal oxide-modified grafted cinnamonitrile silicone rubber liquid to the volume ratio of the grafted cinnamonitrile silicone rubber liquid is 26g:(0.16g~0.21g):(0.13g~0.18g):0.13g:0.13g:120mL;

[0054] 9. Place the metal oxide modified silicone rubber liquid under vacuum conditions, stir and evacuate to remove the air bubbles introduced into the silicone rubber during stirring, and obtain a bubble-free metal oxide modified silicone rubber liquid.

[0055] 10. Using an automatic coating machine, apply bubble-free metal oxide modified silicone rubber liquid evenly to a clean mold containing a release agent at a constant rate; then smoothly move the mold into a flat vulcanizing machine, close the mold, and set the matching vulcanizing pressure and temperature parameters to complete one vulcanization within a preset time; after vulcanization, wait for the equipment to cool to room temperature, open the mold, and take out the product to obtain a primary vulcanized composite medium.

[0056] 11. The primary vulcanized composite medium is placed in a high-temperature forced-air drying oven for secondary vulcanization to obtain the secondary vulcanized composite medium; the secondary vulcanized composite medium is left to stand at room temperature for a period of time to obtain nonlinear conductive silicone rubber based on multi-oxide sintered body doping.

[0057] Specific Implementation Method Three: This implementation method differs from Specific Implementation Method One or Two in the following ways: the mass ratio of Bi₂O₃, MnO₂, and zinc acetate powder to deionized water in step one is (0.16g~0.21g):(0.13g~0.18g):49g:1040mL; the stirring speed in step one is 2.5r / s~2.8r / s, and the stirring time is 15min; the average particle size of Bi₂O₃ and MnO₂ in step one is 10μm. Other steps are the same as in Specific Implementation Method One or Two.

[0058] Specific Implementation Method Four: This implementation method differs from Specific Implementation Methods One to Three in the following ways: the mass ratio of Co2O3, Cr2O3, and sodium hydroxide powder to deionized water in step two is 0.13g:0.13g:26g:624mL; the stirring speed in step two is 2.5r / s~2.8r / s, and the stirring time is 15min; the average particle size of Co2O3 and Cr2O3 in step two is 10μm. Other steps are the same as in Specific Implementation Methods One to Three.

[0059] Specific Implementation Method Five: This implementation method differs from Specific Implementation Methods One to Four in the following ways: the dropping rate in step three is 45-50 drops per minute; the constant temperature in step three is 70°C; the pore size of the aqueous microporous filter membrane in step three is 0.45-0.50 μm; the mass ratio of Bi₂O₃, MnO₂, Co₂O₃, and Cr₂O₃ in the mixed solution III in step three is (0.16-0.21):(0.13-0.18):0.13:0.13; the stirring reaction time in step three is 10-15 minutes, and the stirring speed is 2.5-2.8 r / s; the settling time in step three is 6-8 hours; the centrifugation speed in step three is 600 r / min, and the centrifugation time is 10-15 minutes. Other steps are the same as in Specific Implementation Methods One to Four.

[0060] Specific Implementation Method Six: This implementation method differs from Specific Implementation Methods One to Five in the following ways: the drying temperature in step four is 70°C~80°C, and the drying time is 8h~10h; the calcination temperature in step four is 300°C, and the holding time is 2h~3h; the heating rate in step four is 1°C / min. Other steps are the same as in Specific Implementation Methods One to Five.

[0061] Specific Implementation Method Seven: This implementation method differs from Specific Implementation Methods One to Six in the following ways: the silicone rubber component A mentioned in step five is POWERSIL® 745-LG-7046-A-CN, purchased from Wacker Chemie; the silicone rubber component B is POWERSIL® 745-LG-7046-B-CN, purchased from Wacker Chemie; the mass ratio of one part cinnamonitrile to liquid silicone rubber component A in step five is 0.35: 59.65; the mass ratio of one part cinnamonitrile to liquid silicone rubber component B in step five is 0.35: 59.65. Other steps are the same as in Specific Implementation Methods One to Six.

[0062] Specific Implementation Method Eight: This implementation method differs from Specific Implementation Methods One through Seven in the following ways: the stirring speed in steps Five, Six, Seven, and Eight is 2.4 r / s to 3.0 r / s, and the stirring time is 1 h to 2 h; the stirring and vacuuming time in step Nine is 2 h to 3 h, and the stirring speed is 2.4 r / s to 3.0 r / s; the temperature for the primary vulcanization in step Ten is 160℃ to 170℃, and the time is 10 min to 20 min; the pressure of the flat vulcanizing machine in step Ten is 15 MPa; and the size of the mold in step Ten is 100 mm. 100mm 0.175mm. The other steps are the same as those in specific embodiments one through seven.

[0063] Specific Implementation Method Nine: This implementation method differs from Specific Implementation Methods One to Eight in the following ways: the secondary vulcanization temperature in step eleven is 195℃~205℃, and the secondary vulcanization time is 3h~5h; the composite medium after secondary vulcanization in step eleven is allowed to stand at room temperature for 20h~28h; the nonlinear conductive silicone rubber based on multi-oxide sintered body doping described in step eleven has a breakdown field strength of 126~155KV / mm at 30℃; 115~143KV / mm at 50℃; and 110~139KV / mm at 70℃; the tensile strength can reach 12.06MPa at room temperature. Other steps are the same as in Specific Implementation Methods One to Eight.

[0064] Specific Implementation Method 10: This implementation method is an application of nonlinear conductive silicone rubber based on multi-oxide sintered body doping in the field of power transmission and distribution.

[0065] The beneficial effects of the present invention are verified using the following embodiments:

[0066] Example 1: A method for preparing nonlinear conductive silicone rubber based on multi-oxide sintered body doping, specifically completed according to the following steps:

[0067] 1. Add Bi2O3, MnO2 and zinc acetate powder to deionized water and stir continuously at a speed of 2.5 r / s for 15 min to obtain mixed solution I;

[0068] The mass ratio of Bi2O3, MnO2, and zinc acetate powder to deionized water in step one is 0.16g:0.18g:49g:1040mL;

[0069] The average particle size of Bi2O3 and MnO2 mentioned in step one is 10 μm;

[0070] II. Add Co2O3, Cr2O3, and sodium hydroxide powder to deionized water and stir continuously at a speed of 2.5 r / s for 15 min to obtain mixed solution II;

[0071] The mass ratio of Co2O3, Cr2O3, and sodium hydroxide powder to deionized water in step two is 0.13g:0.13g:26g:624mL;

[0072] The average particle size of Co2O3 and Cr2O3 mentioned in step two is 10 μm;

[0073] 3. Filter mixed solution I through an aqueous microporous membrane to obtain filtered mixed solution I; add the filtered mixed solution I dropwise at a constant rate to mixed solution II at 70℃ and under stirring. After the addition is complete, mixed solution III is obtained. Continue stirring at a speed of 2.5 r / s for 15 min, then let it stand for 6 h, collect the lower precipitate, centrifuge at a speed of 600 r / min for 15 min, wash, and obtain the reaction product.

[0074] In step three, the dripping rate is 50 drops per minute;

[0075] The pore size of the water-based microporous filter membrane mentioned in step three is 0.50 μm;

[0076] In step three, the mass ratio of Bi₂O₃, MnO₂, Co₂O₃, and Cr₂O₃ in the mixed solution III is 0.16 g: 0.18 g: 0.13 g: 0.13 g.

[0077] 4. The reaction product was dried at 70°C for 9 hours, ground into powder, and then placed in a muffle furnace. The temperature was increased from room temperature to 300°C at a rate of 1°C / min, held for 2 hours, and finally cooled to room temperature to obtain a metal oxide mixture containing ZnO.

[0078] 5. Add equal volumes of liquid silicone rubber components A and B to the reactor respectively; divide cinnamonitrile into two equal parts, add one part of cinnamonitrile to liquid silicone rubber component A, stir for 1 hour to obtain cinnamonitrile-grafted silicone rubber component A; add the other part of cinnamonitrile to liquid silicone rubber component B, stir for 1 hour to obtain cinnamonitrile-grafted silicone rubber component B.

[0079] The silicone rubber component A mentioned in step five is model number POWERSIL®745-LG-7046-A-CN, purchased from Wacker Chemie; the silicone rubber component B is model number POWERSIL®745-LG-7046-B-CN, purchased from Wacker Chemie.

[0080] In step five, the mass ratio of one part cinnamonitrile to component A of the liquid silicone rubber is 0.35: 59.65;

[0081] In step five, the mass ratio of one part cinnamonitrile to component B of the liquid silicone rubber is 0.35: 59.65;

[0082] 6. Stir the cinnamonitrile-grafted silicone rubber component A, then add a metal oxide mixture containing ZnO while stirring, and stir for 1 hour to obtain the doped silicone rubber component A.

[0083] 7. Stir the cinnamonitrile-grafted silicone rubber B component, then add a metal oxide mixture containing ZnO under stirring conditions, stir for 1 hour, and obtain the doped silicone rubber B component.

[0084] The cinnamonitrile-grafted silicone rubber A mentioned in step six has the same mass as the cinnamonitrile-grafted silicone rubber B mentioned in step seven; the ZnO-containing metal oxide mixture mentioned in step six has the same mass as the ZnO-containing metal oxide mixture mentioned in step seven.

[0085] 8. Mix the doped silicone rubber component A and the doped silicone rubber component B, and stir for 1 hour to obtain a silicone rubber liquid modified with metal oxide and grafted with cinnamonitrile.

[0086] The doped silicone rubber A component and the doped silicone rubber B component mentioned in step eight have the same mass;

[0087] The stirring speed described in steps five, six, seven, and eight is 2.4 r / s;

[0088] In step eight, the mass ratio of ZnO, Bi2O3, MnO2, Co2O3, and Cr2O3 in the metal oxide-modified grafted cinnamonitrile silicone rubber liquid to the volume ratio of the grafted cinnamonitrile silicone rubber liquid is 26g:0.16g:0.18g:0.13g:0.13g:120mL.

[0089] 9. The metal oxide modified silicone rubber liquid was placed under vacuum conditions and stirred at a stirring speed of 2.4 r / s for 2 hours to remove the air bubbles introduced into the silicone rubber during the stirring process, so as to obtain a bubble-free metal oxide modified silicone rubber liquid.

[0090] 10. Using an automatic coating machine, apply bubble-free metal oxide modified silicone rubber liquid evenly to a clean mold containing a release agent at a constant rate; then smoothly move the mold into a flat vulcanizing machine, close the mold, and set the matching vulcanizing pressure and temperature parameters to complete one vulcanization within a preset time; after vulcanization, wait for the equipment to cool to room temperature, open the mold, and take out the product to obtain a primary vulcanized composite medium.

[0091] The temperature for the first vulcanization in step ten is 165°C, and the time is 15 minutes.

[0092] The pressure of the flat vulcanizing machine described in step ten is 15 MPa;

[0093] The mold described in step ten has a size of 100mm. 100mm 0.175mm;

[0094] XI. The primary vulcanized composite medium is placed in a high-temperature forced-air drying oven for secondary vulcanization to obtain the secondary vulcanized composite medium; the secondary vulcanized composite medium is left to stand at room temperature for 24 hours to obtain nonlinear conductive silicone rubber based on multi-oxide sintered body doping (denoted as ZnO-0.6%Bi2O3, 0.7% MnO2 / SiR-CIN or ZnO-0.6%Bi2O3, 0.7% MnO2, 0.5% Co2O3, 0.5%Cr2O3 / SiR-CIN).

[0095] The temperature for the secondary vulcanization described in step eleven is 200℃, and the time for the secondary vulcanization is 4 hours.

[0096] In the metal oxide mixture containing ZnO described in Example 1, the mass of Bi2O3 is 0.6% of the mass of ZnO, the mass of MnO2 is 0.7% of the mass of ZnO, the mass of Co2O3 is 0.5% of the mass of ZnO, and the mass of Cr2O3 is 0.5% of the mass of ZnO.

[0097] Example 2: The difference between this example and Example 1 is that the mass ratio of Bi2O3, MnO2, and zinc acetate powder to deionized water in step one is 0.18g:0.16g:49g:1040mL; the mass ratio of Bi2O3, MnO2, Co2O3, and Cr2O3 in the mixed solution III in step three is 0.18g:0.16g:0.13g:0.13g.

[0098] In step eight, the mass ratio of ZnO, Bi₂O₃, MnO₂, Co₂O₃, and Cr₂O₃ to the volume ratio of the grafted cinnamonitrile silicone rubber liquid is 26 g: 0.18 g: 0.16 g: 0.13 g: 0.13 g: 120 mL. Step eleven yields a nonlinear conductive silicone rubber based on multi-oxide sintered body doping (denoted as ZnO-0.7%Bi₂O₃, 0.6% MnO₂ / SiR-CIN or ZnO-0.7%Bi₂O₃, 0.6% MnO₂, 0.5% Co₂O₃, 0.5% Cr₂O₃ / SiR-CIN). Other steps and parameters are the same as in Example 2.

[0099] In the metal oxide mixture containing ZnO described in Example 2, the mass of Bi2O3 is 0.7% of the mass of ZnO, the mass of MnO2 is 0.6% of the mass of ZnO, the mass of Co2O3 is 0.5% of the mass of ZnO, and the mass of Cr2O3 is 0.5% of the mass of ZnO.

[0100] Example 3: The difference between this example and Example 1 is that the mass ratio of Bi2O3, MnO2, and zinc acetate powder to deionized water in step one is 0.21g:0.13g:49g:1040mL; the mass ratio of Bi2O3, MnO2, Co2O3, and Cr2O3 in the mixed solution III in step three is 0.21g:0.13g:0.13g:0.13g.

[0101] In step eight, the mass ratio of ZnO, Bi₂O₃, MnO₂, Co₂O₃, and Cr₂O₃ to the volume ratio of the grafted cinnamonitrile silicone rubber liquid is 26 g: 0.21 g: 0.13 g: 0.13 g: 0.13 g: 120 mL. Step eleven yields a nonlinear conductive silicone rubber based on multi-oxide sintered body doping (denoted as ZnO-0.8%Bi₂O₃, 0.5% MnO₂ / SiR-CIN or ZnO-0.8%Bi₂O₃, 0.5% MnO₂, 0.5% Co₂O₃, 0.5% Cr₂O₃ / SiR-CIN). Other steps and parameters are the same as in Example 2.

[0102] In the metal oxide mixture containing ZnO described in Example 3, the mass of Bi2O3 is 0.8% of the mass of ZnO, the mass of MnO2 is 0.5% of the mass of ZnO, the mass of Co2O3 is 0.5% of the mass of ZnO, and the mass of Cr2O3 is 0.5% of the mass of ZnO.

[0103] Comparative Example 1: The differences between this example and Example 1 are as follows: In step one, the mass ratio of Bi₂O₃, MnO₂, and zinc acetate powder to the volume ratio of deionized water is 0 g:0 g:49 g:1040 mL; in step three, the mass ratio of Bi₂O₃, MnO₂, Co₂O₃, and Cr₂O₃ in the mixed solution III is 0 g:0 g:0 g:0 g; in step eight, the mass ratio of ZnO, Bi₂O₃, MnO₂, Co₂O₃, and Cr₂O₃ to the volume ratio of the cinnamonitrile-grafted silicone rubber liquid is 26 g:0 g:0 g:0 g:0 g:120 mL; and in step eleven, a nonlinear conductive silicone rubber based on ZnO doping is obtained (denoted as ZnO / SiR-CIN or ZnO-SiR-CIN). All other steps and parameters are the same as in Example 2.

[0104] Comparative Example 2: The preparation method of the organic small molecule cinnamonitrile-grafted silicone rubber composite medium (SiR-CIN) is carried out according to the following steps:

[0105] 1. Add equal volumes of liquid silicone rubber components A and B to the reactor respectively; divide cinnamonitrile into two equal parts, add one part of cinnamonitrile to liquid silicone rubber component A, stir for 1 hour to obtain cinnamonitrile-grafted silicone rubber component A; add the other part of cinnamonitrile to liquid silicone rubber component B, stir for 1 hour to obtain cinnamonitrile-grafted silicone rubber component B.

[0106] The silicone rubber component A mentioned in step one is model number POWERSIL®745-LG-7046-A-CN, purchased from Wacker Chemie; the silicone rubber component B is model number POWERSIL®745-LG-7046-B-CN, purchased from Wacker Chemie.

[0107] In step one, the mass ratio of one part cinnamonitrile to component A of liquid silicone rubber is 0.35: 59.65;

[0108] In step one, the mass ratio of one part cinnamonitrile to component B of liquid silicone rubber is 0.35: 59.65;

[0109] 2. Mix equal volumes of cinnamonitrile-grafted silicone rubber component A and cinnamonitrile-grafted silicone rubber component B, and stir for 1 hour to obtain cinnamonitrile-grafted silicone rubber liquid.

[0110] The stirring speed described in steps one and two is 2.4 r / s;

[0111] 3. The silicone rubber liquid grafted with cinnamonitrile was placed under vacuum conditions, stirred at a speed of 2.4 r / s and vacuumed for 2 hours to remove the air bubbles introduced into the silicone rubber during the stirring process, so as to obtain a silicone rubber liquid grafted with cinnamonitrile without air bubbles.

[0112] 4. The automatic coating machine uniformly applies the cinnamonitrile-grafted silicone rubber liquid to a clean mold containing a release agent at a constant rate; then the mold is smoothly moved into the flat vulcanizing machine, the mold is closed and the matching vulcanizing pressure and temperature parameters are set, and vulcanization is completed within a preset time; after vulcanization, the equipment is allowed to cool to room temperature, the mold is opened and the product is taken out to obtain a vulcanized composite medium.

[0113] The temperature for the first vulcanization in step four is 165°C, and the time is 15 minutes.

[0114] The pressure of the flat vulcanizing machine described in step four is 15 MPa;

[0115] The mold described in step four has a size of 100mm. 100mm 0.175mm;

[0116] 5. Place the primary vulcanized composite medium in a high-temperature forced-air oven for secondary vulcanization to obtain the secondary vulcanized composite medium; let the secondary vulcanized composite medium stand at room temperature for 24 hours to obtain the organic small molecule cinnamonitrile grafted silicone rubber composite medium (denoted as SiR-CIN).

[0117] Figure 1 (a) is the Weibull distribution diagram of the breakdown field strength of the composite media prepared in Examples 1-3 and Comparative Examples 1-2 at 30°C; (b) is the Weibull distribution diagram of the breakdown field strength of the composite media prepared in Examples 1-3 and Comparative Examples 1-2 at 50°C; and (c) is the Weibull distribution diagram of the breakdown field strength of the composite media prepared in Examples 1-3 and Comparative Examples 1-2 at 70°C.

[0118] Depend on Figure 1It is known that at 30℃, the addition of ZnO reduces the breakdown field strength of cinnamonitrile-grafted silicone rubber from 157.2 kV / mm to 146.4 kV / mm. This is because ZnO, as a semiconductor filler, forms a Schottky barrier with silicone rubber. When the electric field is low, the barrier can hinder charge injection, but when the electric field exceeds a critical value, the barrier breaks down, and a large amount of charge is injected into the matrix. At the same time, the conductivity of ZnO distorts the electric field distribution, leading to local field concentration and ultimately reducing the overall breakdown strength. Furthermore, there is a thin interfacial layer between ZnO and silicone rubber. The dielectric constant and conductivity of silicone rubber and zinc oxide are mismatched, easily forming space charge accumulation regions and electric field distortion points. Simultaneously, the thin interfacial layer contains microscopic defects, which become breakdown initiation points, accelerating insulation failure and leading to a decrease in breakdown strength. The addition of Bi₂O₃ facilitates the formation of a Schottky barrier. Barrier mismatch leads to significant charge retention at the interface, resulting in strong electric field distortion. Furthermore, the greater difference in conductivity between Bi₂O₃ and ZnO / silicone rubber further disrupts electric field uniformity, causing the breakdown strength to decrease with increasing Bi₂O₃ content. The introduction of Bi₂O₃ increases the number of interfaces, and its poor compatibility with ZnO and silicone rubber makes it prone to forming thick, defect-rich interfacial layers. MnO₂, on the other hand, can regulate the barrier height at the interface and improve its conductivity. Therefore, a higher MnO₂ content enhances the ability to optimize interfacial conductivity matching, thereby reducing space charge accumulation and homogenizing the electric field to some extent, thus improving breakdown strength. However, as temperature increases, the breakdown strength of all doped systems decreases. This is because high temperatures reduce the stability of the interfacial barrier, accelerate charge injection and migration, and further enlarge defects in the interfacial layer and voids caused by thermal expansion, ultimately exacerbating the decline in breakdown strength.

[0119] Figure 2 (a) shows the change of electrical conductivity current with electric field strength at 30°C for the composite media prepared in Examples 1-3 and Comparative Examples 1-2; (b) shows the change of electrical conductivity current with electric field strength at 50°C for the composite media prepared in Examples 1-3 and Comparative Examples 1-2; and (c) shows the change of electrical conductivity current with electric field strength at 70°C for the composite media prepared in Examples 1-3 and Comparative Examples 1-2.

[0120] Depend on Figure 2It can be seen that at 30℃, the conductivity of silicone rubber is directly proportional to the electric field strength, and there is no nonlinear relationship. After grafting cinnamonitrile onto silicone rubber, the composite silicone rubber exhibits nonlinear characteristics. The nonlinear characteristics are more obvious after adding ZnO. Moreover, as the Bi2O3 content increases, its nonlinear coefficient gradually increases, and the threshold field strength gradually decreases. This is because there are grain boundary layers between ZnO grains, forming a large number of Schottky barriers. When the electric field is low, the potential barrier hinders carrier migration, resulting in extremely low conductivity. When the electric field reaches the threshold strength, the barrier breaks down, a large number of carriers jump, and the conductivity rises sharply, exhibiting nonlinear characteristics. When ZnO is doped into silicone rubber, this piezoresistive mechanism of the grain boundary barrier is retained, causing the composite insulating material to exhibit nonlinear conductivity. Bi2O3 is a key dopant for ZnO. It is enriched in the grain boundary layer, which increases the height difference of the grain boundary barrier. When the electric field is low, the conductivity increases slowly. When the electric field exceeds the threshold, the barrier breaks down, causing the conductivity to rise sharply. Therefore, with the increase of Bi2O3 content, the nonlinear coefficient of the silicone rubber composite medium increases. The increase of Bi2O3 content will increase the defect density of the grain boundary layer. These defects are equivalent to weak points in the barrier, which reduces the electric field strength required to break down the grain boundary barrier. Therefore, with the increase of Bi2O3 content, its threshold field strength decreases. As the temperature rises, the overall conductivity of the silicone rubber composite medium increases and the threshold electric field strength decreases. This is because as the temperature rises, the thermal kinetic energy of the charge carriers increases, making it easier to overcome the resistance of the grain boundary barrier. At the same time, thermal excitation generates more charge carriers. The combined effect of these two factors causes the conductivity to increase significantly with increasing temperature. Furthermore, as the temperature rises, the thermal stability of the grain boundary barrier decreases, and the electric field threshold required for charge carrier transitions decreases. Therefore, the threshold electric field strength decreases with increasing temperature.

[0121] Figure 3 (a) is a line graph showing the tensile strength and elongation at break of the composite media prepared in Examples 1-3 and Comparative Examples 1-2 at 30°C; (b) is a line graph showing the tensile strength and elongation at break of the composite media prepared in Examples 1-3 and Comparative Examples 1-2 at 50°C; and (c) is a line graph showing the tensile strength and elongation at break of the composite media prepared in Examples 1-3 and Comparative Examples 1-2 at 70°C.

[0122] Depend on Figure 3 It can be seen that silicone rubber itself is an elastomer with weak mechanical properties. After adding ZnO, a bond is formed between ZnO and the silicone rubber matrix, and the load can be transferred to the rigid filler through the interface, thereby improving the tensile strength and modulus of the material.

[0123] The stress curve of ZnO / SiR-CIN in the figure is significantly higher than that of pure SiR-CIN, which intuitively demonstrates the reinforcing effect of ZnO. Bi2O3 and MnO2 can improve the interfacial bonding force between ZnO and the silicone rubber matrix, making load transfer more efficient and thus increasing tensile stress. Furthermore, an appropriate amount of Bi2O3 can optimize the interfacial compatibility between ZnO and the silicone rubber matrix, enhancing the bonding force between particles and the matrix, allowing the load to be transferred more efficiently from the matrix to the rigid ZnO particles, thereby improving the mechanical properties of the material. MnO2 can inhibit the agglomeration of ZnO particles, making the filler more uniformly dispersed in the silicone rubber matrix, reducing stress concentration caused by particle agglomeration, and thus improving the mechanical properties of the material. Excessive or imbalanced Bi2O3 and MnO2 will form a "weak interfacial layer" at the interface, reducing load transfer efficiency and thus deteriorating the mechanical properties, although still significantly higher than those of pure silicone rubber. As the temperature increases, the thermal motion of the molecular chains in the silicone rubber matrix intensifies, weakening the intermolecular forces, leading to a decrease in the tensile strength and modulus of the material with increasing temperature.

[0124] Figure 4 The graph shows the changes in thermal weight loss of the composite media prepared in Examples 1-3 and Comparative Examples 1-2 at 900°C.

[0125] Depend on Figure 4 It can be seen that pure SiR-CIN has a low weight loss onset temperature, a fast weight loss rate, and a relatively high residual mass. This is because the thermal decomposition process of pure silicone rubber is relatively mild but continuous, lacking the thermal barrier and catalytic regulation of inorganic fillers, leading to gradual decomposition at high temperatures. The residual part may be incompletely decomposed carbon or silicon-based residues. Compared with pure SiR-CIN, ZnO / SiR-CIN has a significantly higher weight loss onset temperature, a faster weight loss rate, and a lower final residual mass. This is because ZnO, as an inorganic filler, delays heat transfer through physical barrier, improving initial thermal stability; on the other hand, it may participate in the catalytic decomposition reaction of silicone rubber, making the decomposition process more concentrated. The combined catalytic effect of Bi2O3 and MnO2 alters the decomposition pathway of silicone rubber. Different ratios result in different numbers and distributions of catalytically active sites, leading to differences in weight loss onset temperature and weight loss rate.

[0126] Figure 5 The graphs show the thermal conductivity of the composite media prepared in Examples 1-3 and Comparative Examples 1-2 as a function of temperature.

[0127] Depend on Figure 5It can be seen that the thermal conductivity of pure SiR-CIN is significantly lower than that of the system containing inorganic fillers, and it changes slowly with temperature. This is because the thermal conduction of the silicone rubber matrix is ​​mainly phonon conduction, and its thermal conductivity is inherently low. After the introduction of ZnO, the thermal conductivity is significantly improved. This is because the thermal conductivity of ZnO is much higher than that of the silicone rubber matrix, forming a thermally conductive pathway within the matrix and enhancing its heat transfer capability. Furthermore, the thermal conductivity increases slightly with increasing temperature. The thermal conductivity of silicone rubber after adding Bi₂O₃ and MnO₂ is higher than that of the system containing only ZnO, and the thermal conductivity increases with increasing Bi₂O₃ and decreasing MnO₂ proportions. This is because the thermal conductivity of Bi₂O₃ and MnO₂ complements that of ZnO, and the particle packing and interfacial contact of multiple fillers facilitate the construction of a continuous thermally conductive network, reducing the interfacial barrier to heat transfer. The ratio of ZnO-0.8%Bi₂O₃ and 0.5%MnO₂ may result in more uniform filler dispersion and smoother thermal pathways, thus leading to the highest thermal conductivity. The thermal conductivity of all filler-containing systems increases slightly with increasing temperature because higher temperatures intensify phonon vibrations and enhance interparticle thermal motion, which is beneficial for heat transfer. However, due to the limitations of the matrix's own thermal conduction mechanism, the effect of temperature on the thermal conductivity of pure SiR-CIN is negligible.

[0128] Figure 6 The relative permittivity-frequency curves of the composite media prepared in Examples 1-3 and Comparative Examples 1-2 are shown.

[0129] Depend on Figure 6 It can be seen that pure SiR-CIN has the lowest relative permittivity, and it hardly fluctuates with frequency. This is because the polarization mechanism of pure silicone rubber is mainly electronic and atomic polarization. This type of polarization has a fast response speed and a stable degree of polarization over a wide frequency range, resulting in a low permittivity. After introducing ZnO, the relative permittivity increases to about 3.0, and then decreases slightly with frequency. The reason is that ZnO has a higher dielectric constant than silicone rubber, and its introduction introduces an additional polarization effect through interfacial polarization. However, the interfacial polarization response lags at high frequencies, resulting in a slight decrease in dielectric constant. The relative dielectric constant further increases after the introduction of Bi2O3 and MnO2 composite fillers, reaching a maximum of 4.0. Moreover, the dielectric constant increases with the increase of Bi2O3 ratio and the decrease of MnO2 ratio. The higher the Bi2O3 ratio, the more interfacial polarization sites there are, and the higher the dielectric constant. Bi2O3 and MnO2 themselves have certain nonlinear electrical properties. When combined with ZnO, they form multiple nonlinear sites inside the material. The barrier transitions and carrier capture and release processes of these sites under the action of an electric field are highly nonlinear, thereby significantly enhancing the overall nonlinear performance of the material.

[0130] Figure 7 Simulation diagram of steady-state electric field distribution of ZnO and composite media prepared in Examples 1-3;

[0131] Depend onFigure 7 It can be seen that when pure zinc oxide is doped, the maximum electric field strength appears in the main insulation, with a value of 8.73 kV / mm, and the electric field strength at the root of the stress cone is 1.86 kV / mm. However, after doping with Bi2O3 and MnO2, the main insulation still has a maximum electric field strength, but the value is not much different. The electric field strength at the root of the stress cone changes significantly. When the ratio of Bi2O3 to MnO2 is 0.6:0.7, the electric field strength at the root of the stress cone is the largest, at 2.39 kV / mm. However, when the ratio of Bi2O3 to MnO2 is 0.7:0.6 and 0.8:0.5, the electric field strength at the root of the stress cone is significantly reduced compared with pure zinc oxide. In particular, when the ratio of Bi2O3 to MnO2 is 0.7:0.6, it is reduced to 1.33 kV / mm. This shows that appropriate doping with Bi2O3 and MnO2 can greatly improve the ability to optimize the electric field distribution, reduce the electric field at the root of the stress cone, and ensure the safe operation of the cable.

[0132] Figure 8 Infrared spectra of the composite media prepared in Examples 1-3 and Comparative Examples 1-2;

[0133] Depend on Figure 8 It can be seen that in the range of 3200~3600cm -1 At the corresponding hydroxyl group, SiR-CIN exhibits a significant absorption peak in this region, due to the hydroxyl groups at the ends of the silicone rubber chains. The peak intensity decreases after doping with metal oxides because the metal ions coordinate with the hydroxyl groups, reducing the vibrational absorption of OH groups. Meanwhile, the peak intensity increases at 2956 cm⁻¹. -1 The peaks at saturated alkyl groups CH2 and CH3 correspond to this region because the organic side chains of silicone rubber absorb in this range. The strong peak of SiR-CIN is due to the vibration of its CH bonds. The peak intensity decreases significantly after ZnO doping, possibly because the interaction between ZnO and the organic chain disrupts the CH vibration environment. The peaks of samples containing Bi2O3 and MnO2 are relatively preserved, indicating that these two oxides have weak interference with the organic chain. -1 The antisymmetric stretching vibration of Si-O-Si is a characteristic peak of silicone rubber, and all samples show strong absorption in this range, approximately 700~800 cm⁻¹. -1 This corresponds to the Si-C stretching vibration; in the range of 600~800 cm⁻¹. -1 The range corresponds to the vibration of the Co-O bond; in the range of 500~700cm. -1 The interval corresponds to the vibration of the Cr-O bond; for samples containing Bi₂O₃ and MnO₂, the range is 580–600 cm⁻¹. -1Characteristic peaks appear, and their positions change with the Bi / Mn ratio. The peaks shift slightly to lower wavenumbers as the Bi content increases, demonstrating the presence and ratio of Bi-O and Mn-O bonds and their influence on vibration. Because the doping levels of these four oxides are low, their characteristic peaks are masked by the strong peaks of the matrix due to their weak intensity. However, the introduction of these four oxides alters the microstructure of the composite material, such as crystallinity and particle dispersion, thereby affecting the scattering or absorption efficiency of infrared light, leading to subtle differences in the baseline or peak shape in certain regions of the overall image.

[0134] Figure 9 The upper figure shows the XRD patterns of the composite media prepared in Examples 1-3 and Comparative Example 1, and the lower figure shows the XRD patterns of the metal oxide mixtures containing ZnO in Examples 1-3 and Comparative Example 1.

[0135] Depend on Figure 9 It can be seen that the diffraction peaks of pure ZnO in both images are at the same position, corresponding to the characteristic crystal planes of the hexagonal wurtzite structure, indicating that the crystal structure of the ZnO matrix has not been fundamentally changed by the SiR-CIN matrix and the doped metal elements. After doping with Bi2O3, MnO2, Co2O3, and Cr2O3, no obvious impurity phase diffraction peaks appeared, possibly because the doping amount was low and no independent crystal phase was formed. The diffraction peak intensities changed after doping, with different peak intensities corresponding to different Bi2O3 and MnO2 ratios, indicating that the doping ratio has a regulatory effect on the ZnO crystallization process. Although the baseline of zinc oxide doped into silicone rubber is slightly higher than that of zinc oxide powder, the peak positions are basically the same. This indicates that the SiR-CIN matrix did not change the crystal structure of ZnO and the doped phase. In terms of crystallinity, both the composite medium after metal oxide doping with silicone rubber and the metal oxide powder have relatively higher diffraction peak intensities for ZnO-0.7% Bi2O3, 0.6% MnO2, 0.5% Co2O3, 0.5% Cr2O3 / SiR-CIN.

[0136] Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Anyone skilled in the art can make various modifications and alterations without departing from the spirit and scope of the present invention. Therefore, the scope of protection of the present invention should be determined by the claims.

Claims

1. A multi-oxide sinter-based doped non-linear conductive silicone rubber, characterized by The nonlinear conductive silicone rubber doped based on the multi-oxide sintered body is metal oxide modified silicone rubber; the metal oxide includes ZnO, Bi2O3, MnO2, Co2O3 and Cr2O3; the silicone rubber is silicone rubber grafted with cinnamyl cyanide; The mass and volume ratio of ZnO, Bi2O3, MnO2, Co2O3 and Cr2O3 to the silicone rubber grafted with cinnamyl cyanide is 26g:(0.16g-0.21g):(0.13g-0.18g):0.13g:0.13g:120mL.

2. A method of preparing a multi-oxide sinter doped nonlinear conductive silicone rubber according to claim 1, characterized in that The preparation method is specifically completed by the following steps: I. Bi2O3, MnO2 and zinc acetate powder are added into deionized water, and continuous stirring is carried out to obtain a mixed solution I; II. Co2O3, Cr2O3 and sodium hydroxide powder are added into deionized water, and continuous stirring is carried out to obtain a mixed solution II; III. The mixed solution I is filtered through a water-based microporous filter membrane to obtain a filtered mixed solution I; the filtered mixed solution I is added into the constant-temperature and stirring mixed solution II at a constant speed, and after the addition is completed, a mixed solution III is obtained; the stirring is continued for a period of time, and then the lower precipitate is collected, centrifuged, washed and dried to obtain a reaction product; IV. The reaction product is dried, ground into powder, and then placed into a muffle furnace, heated to a calcination temperature, kept warm, and finally cooled to room temperature to obtain a metal oxide mixture containing ZnO; V. Equal volume of A component and B component of liquid silicone rubber are respectively added into a reactor; cinnamyl cyanide is divided into two equal masses, one of which is added into the A component of liquid silicone rubber, and stirred for a period of time to obtain cinnamyl cyanide grafted silicone rubber A component; the other part of cinnamyl cyanide is added into the B component of liquid silicone rubber, and stirred for a period of time to obtain cinnamyl cyanide grafted silicone rubber B component; VI. The cinnamyl cyanide grafted silicone rubber A component is stirred, and then the metal oxide mixture containing ZnO is added under stirring, and stirred for a period of time to obtain doped silicone rubber A component; VII. The cinnamyl cyanide grafted silicone rubber B component is stirred, and then the metal oxide mixture containing ZnO is added under stirring, and stirred for a period of time to obtain doped silicone rubber B component; The mass of the cinnamyl cyanide grafted silicone rubber A component in step VI is the same as that of the cinnamyl cyanide grafted silicone rubber B component in step VII; the mass of the metal oxide mixture containing ZnO in step VI is the same as that of the metal oxide mixture containing ZnO in step VII; VIII. The doped silicone rubber A component and the doped silicone rubber B component are mixed and stirred for a period of time to obtain metal oxide modified cinnamyl cyanide grafted silicone rubber liquid; The mass of the doped silicone rubber A component in step VIII is the same as that of the doped silicone rubber B component in step VIII. The mass ratio of ZnO, Bi2O3, MnO2, Co2O3 and Cr2O3 to the volume of the grafted cinnamaldehyde nitrile silicone rubber liquid in the metal oxide modified grafted cinnamaldehyde nitrile silicone rubber liquid in step eight is 26 g: (0.16 g-0.21 g): (0.13 g-0.18 g): 0.13 g: 0.13 g: 120 mL; Nine, the metal oxide modified silicone rubber liquid is placed in a vacuum condition, stirred and vacuumed to remove the air bubbles introduced into the silicone rubber during stirring, to obtain an air bubble-free metal oxide modified silicone rubber liquid; Ten, the air bubble-free metal oxide modified silicone rubber liquid is uniformly coated into a clean mold containing a release agent on the surface by using an automatic film coating machine at a constant rate; then the mold is smoothly moved into a flat curing machine, the mold is closed and the matching curing pressure and temperature parameters are set, and the first vulcanization is completed within a preset time; after vulcanization is completed, the equipment is cooled to room temperature, the mold is opened and the product is taken out, to obtain a first vulcanization composite medium; Eleven, the first vulcanization composite medium is placed in a high-temperature air oven for secondary vulcanization, to obtain a secondary vulcanized composite medium; the secondary vulcanized composite medium is left to stand for a period of time in a room temperature environment, to obtain a multi-oxide sintered body doped nonlinear conductive silicone rubber.

3. A method of preparing a multi-oxide sinter doped based nonlinear conductive silicone rubber according to claim 2, characterized in that The mass ratio of Bi2O3, MnO2, zinc acetate powder to the volume of deionized water in step one is (0.16 g-0.21 g): (0.13 g-0.18 g): 49 g: 1040 mL; the stirring speed in step one is 2.5 r / s-2.8 r / s, and the stirring time is 15 min; the average particle size of Bi2O3 and MnO2 in step one is 10 μm.

4. The method for preparing nonlinear conductive silicone rubber based on multi-oxide sintered body doping according to claim 2, characterized in that... The mass ratio of Co2O3, Cr2O3, sodium hydroxide powder to the volume of deionized water in step two is 0.13 g: 0.13 g: 26 g: 624 mL; the stirring speed in step two is 2.5 r / s-2.8 r / s, and the stirring time is 15 min; the average particle size of Co2O3 and Cr2O3 in step two is 10 μm.

5. The method for preparing nonlinear conductive silicone rubber based on multi-oxide sintered body doping according to claim 2, characterized in that... The dropping speed in step three is 1 minute 45-50 drops; the constant temperature in step three is 70°C; the pore size of the water-based microporous filter membrane in step three is 0.45-0.50 μm; the mass ratio of Bi2O3, MnO2, Co2O3 and Cr2O3 in the mixed solution III in step three is (0.16-0.21): (0.13-0.18): 0.13: 0.13; the stirring reaction time in step three is 10 min-15 min, and the stirring speed is 2.5 r / s-2.8 r / s; the standing time in step three is 6 h-8 h; the centrifugation speed in step three is 600 r / min, and the centrifugation time is 10 min-15 min.

6. A method of preparing a multi-oxide sinter doped based nonlinear conductive silicone rubber according to claim 2, characterized in that The temperature of the drying in step four is 70°C~80°C, and the time of the drying is 8h~10h; the temperature of the calcination in step four is 300℃, and the time of the heat preservation is 2h~3h; the rate of the temperature rise in step four is 1℃ / min.

7. A method of preparing a multi-oxide sinter doped based nonlinear conductive silicone rubber according to claim 2, characterized in that The model of the silicone rubber A component in step five is POWERSIL 745-LG-7046-A-CN; the model of the silicone rubber B component in step five is POWERSIL 745-LG-7046-B-CN; the mass ratio of one part of the cinnamyl cyanide to the A component of the liquid silicone rubber in step five is 0.35:59.65; the mass ratio of one part of the cinnamyl cyanide to the B component of the liquid silicone rubber in step five is 0.35:59.

65.

8. A method of preparing a multi-oxide sinter doped based nonlinear conductive silicone rubber according to claim 2, characterized in that The stirring speed in the step five, the step six, the step seven and the step eight is 2.4r / s~3.0r / s, and the stirring time is 1h~2h; the stirring and vacuumizing time in the step nine is 2h~3h, and the stirring speed is 2.4r / s~3.0r / s; the temperature of the primary vulcanization in the step ten is 160℃~170℃, and the time is 10min~20min; the pressure of the flat vulcanization machine in the step ten is 15MPa; the size of the mold in the step ten is 100mm 100mm 0.175mm.

9. A method of preparing a multi-oxide sinter doped based nonlinear conductive silicone rubber according to claim 2, characterized in that The temperature of the secondary vulcanization in step eleven is 195℃~205℃, and the time of the secondary vulcanization is 3h~5h; the time of the standing of the composite medium after the secondary vulcanization in step eleven in the room temperature environment is 20h~28h; the breakdown field strength of the nonlinear conductive silicone rubber based on the multi-oxide sintered body doping is 126~155KV / mm at 30℃, is 115~143KV / mm at 50℃, and is 110~139KV / mm at 70℃; the tensile strength can reach 12.06MPa at room temperature.

10. Use of a multi-oxide sinter doped non-linear conductive silicone rubber according to claim 1, characterized in that The nonlinear conductive silicone rubber based on the multi-oxide sintered body doping is applied in the field of power transmission and distribution. The nonlinear conductive silicone rubber based on the multi-oxide sintered body doping is applied in the field of power transmission and distribution.

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