Direct-current 10kV-35kV chemical cross-linked polyethylene insulating material and preparation process thereof

Abstract

The invention relates to the technical field of insulating materials, in particular to a direct-current 10kV-35kV chemical crosslinked polyethylene insulating material and a preparation process thereof. The direct-current 10kV-35kV chemical crosslinked polyethylene insulating material is prepared from the following raw materials in parts by weight: 55-65 parts of polyethylene resin; 1.2 parts of a charge inhibitor; 1.5 to 2.5 parts of lead zirconate titanate; and 0.8 to 1.5 parts of bismuth telluride nanosheets. The piezoelectric effect of lead zirconate titanate and the thermoelectric response of the bismuth telluride nanosheet are combined, charges are actively neutralized under an electric field and a temperature gradient, space charge accumulation is radically eliminated, barium titanate coats aluminum oxide composite powder to form a dielectric constant gradient interface, electric field distribution is smoothed, and partial discharge is inhibited; liquid crystal macromolecules are directionally arranged in cooperation with a shear-induced orientation process, a molecular-level charge barrier is constructed, the breakdown field strength is remarkably improved, trace magnesium oxide serves as a charge inhibitor, efficient utilization is achieved through nanoscale dispersion and surface modification, and the raw material cost is reduced.

Description

Technical Field

[0001] This invention relates to the field of insulation materials technology, specifically to a DC 10kV to 35kV chemically cross-linked polyethylene insulation material and its preparation process. Background Technology

[0002] Insulating materials are functional materials that effectively prevent the passage of electric current, playing a crucial role in power systems by isolating conductors from external electrical contact. In the field of power cables, insulating materials wrap around the conductive core to form a physical barrier, ensuring the safe transmission of electrical energy along a predetermined path while preventing accidents such as leakage and short circuits. DC transmission cables have particularly stringent requirements for the electrical stability of their insulating materials, needing to withstand long-term high electric fields to resist problems such as conductivity loss, space charge accumulation, and electrical treeing.

[0003] Generally, although traditional cross-linked polyethylene (XLPE) insulation materials have excellent processability and mechanical strength, they exhibit significant defects under a DC electric field. Space charge accumulates, and charge carriers under DC voltage tend to accumulate in the insulation to form space charge, leading to local electric field distortion and accelerating material aging. At the same time, charge migration is intensified under a temperature gradient of 20°C to 70°C, inducing the risk of insulation breakdown.

[0004] Based on this, the present invention provides a DC 10kV to 35kV chemically cross-linked polyethylene insulation material and its preparation process to solve the above-mentioned technical problems. Summary of the Invention

[0005] The purpose of this invention is to provide a DC 10kV to 35kV chemically cross-linked polyethylene insulation material and its preparation process, thereby solving the problems mentioned in the background art.

[0006] To achieve the above objectives, the present invention provides the following technical solution: This invention proposes a DC 10kV to 35kV chemically cross-linked polyethylene insulation material, which is composed of the following raw materials in parts by weight: polyethylene resin: 55-65 parts; charge inhibitor: 1.2 parts; lead zirconate titanate: 1.5-2.5 parts; bismuth telluride nanosheets: 0.8-1.5 parts; cross-linking agent: 1.2-1.8 parts; cross-linking network reinforcing agent: 0.5-1.0 parts; polyaniline microspheres: 0.05-0.12 parts; hexagonal boron nitride nanotubes: 1.0-2.0 parts; medium gradient filler: 3-6 parts; ion trapping agent: 0.3-0.8 parts; flame retardant synergist: 2-4 parts; liquid crystal polymer: 1.5-3.0 parts; zinc mercaptobenzothiazole salt: 0.2-0.5 parts; fluorophlogopite flakes: 4-8 parts; electron trapping agent: 0.1-0.3 parts; The charge suppressor is magnesium oxide.

[0007] Optionally, the crosslinking agent is di-tert-butyl peroxide.

[0008] Optionally, the crosslinking network enhancer is 4,4'-diaminodiphenyl ether.

[0009] Optionally, the dielectric gradation filler is barium titanate-coated alumina composite powder.

[0010] Optionally, the preparation process of the barium titanate-coated alumina composite powder is as follows: A1. Pretreatment of alumina core: Alpha alumina powder with a particle size of 1.8μm was stirred at 60℃ for 30 minutes in a mixed acid solution with a volume ratio of HNO3 / HF = 3:1, and then washed and dried to achieve a purity of ≥99.99%. A2. Plasma activation: The acid-washed powder was treated with 2.45 GHz microwave plasma for 5 minutes in an Ar / O2=4:1 atmosphere to generate Al⁺ active sites on the surface; A3. Gradient coating reaction: The activated powder was subjected to ultrasonic atomization spraying of a mixture of 0.8 mol / L tetrabutyl titanate ethanol solution and 0.5 mol / L barium acetate nano-sol in a fluidized bed at 400℃ to trigger the self-propagating reaction of cerium ammonium nitrate. The powder was then cooled at a gradient from 50℃ / min to 10℃ / min to form an 80nm barium titanate shell. A4. Oxygen vacancy control: The coated powder was then treated at 600°C for 45 minutes in a reducing atmosphere of N2 / H2 = 95:5 to achieve an oxygen vacancy concentration of 10¹. 8 -10¹ 9 cm⁻³; A5. Surface passivation: Finally, the powder is vapor-deposited in tetraethyl orthosilicate vapor at 250℃ / 0.1 MPa for 20 minutes to form a 5-nm amorphous SiO2 layer on the surface, thus obtaining barium titanate-coated alumina composite powder.

[0011] Optionally, the flame retardant synergist is zinc borate.

[0012] Optionally, the electron trapping agent is molybdenum trioxide.

[0013] Optionally, the ion trapping agent is zirconium phosphate.

[0014] Based on the above-mentioned DC 10kV to 35kV chemically cross-linked polyethylene insulation material, this invention also proposes a preparation process for a DC 10kV to 35kV chemically cross-linked polyethylene insulation material, comprising the following steps: S1. First, perform pre-dispersion processing of the functional masterbatch using a twin-screw extruder with a screw diameter of 65mm and an aspect ratio of 48. Add 55-65 parts by weight of polyethylene resin, 1.0-2.0 parts by weight of hexagonal boron nitride nanotubes, and 4-8 parts by weight of fluorophlogopite flakes through the main feed port. Control the temperature in Zone 1 to 90℃; Zone 2, 110℃; 120℃ in three zones; Die head temperature 105℃; 1.5-2.5 parts by weight of surface-treated lead zirconate titanate, 0.8-1.5 parts by weight of bismuth telluride nanosheets, and 1.2 parts by weight of magnesium oxide were injected into the side feed port. The screw speed was controlled at 180-220 rpm, and the vacuum degree was maintained at -0.08 to -0.1 MPa. Finally, 0.05-0.12 parts by weight of polyaniline microspheres and 0.3-0.8 parts by weight of zirconium phosphate in ethanol suspension were injected at the end of the melting section. Functional masterbatch with a particle size of about 3 mm was obtained by underwater pelletizing. S2. Then, a dynamic crosslinking reaction is carried out. The functional masterbatch and the remaining polyethylene resin are added from the first-stage feed port using a two-stage reactive extruder and melted at 130-140℃ and 8-12MPa pressure. At the same time, 1.2-1.8 parts by weight of di-tert-butyl peroxide are injected. In the second-stage reaction section at 160-170℃ and 15-18MPa, 0.5-1.0 parts by weight of 4,4'-diaminodiphenyl ether and 1.5-3.0 parts by weight of liquid crystal polymer are injected. At the end of the reaction section, 2-4 parts by weight of zinc borate and 0.1-0.3 parts by weight of molybdenum trioxide premixed powder are added. The mixture is then extruded through a die to form a gel-state substrate. S3. Next, a shear-induced orientation process is implemented. Using a rotational stretch rheometer, the temperature is gradually reduced from 175℃ to 155℃ at a rate of 2℃ / min. At 175℃, the mixture is treated at a shear rate of 3000s⁻¹ for 10 minutes to align the liquid crystal polymer along the extrusion direction. When the temperature is reduced to 165℃, a stretching ratio of 1.8 is applied. Finally, during the 155℃ holding stage, 0.2-0.5 parts by weight of a toluene solution of zinc mercaptobenzothiazole salt is injected to complete the crosslinking network fixation. S4. Finally, gradient vulcanization molding is carried out using a vertical fully automatic vulcanizing tank. First, it is preheated in a nitrogen environment of 140℃ and 0.8MPa for 20-30 minutes, then vulcanized in saturated steam at 185-190℃ and 1.5-1.8MPa for 15-20 minutes. Finally, the pressure is reduced in stages at a rate of 0.05MPa / min, while simultaneously cooling from 160℃ to 80℃ with atomized deionized water. The entire process lasts for 50 minutes.

[0015] Optionally, in step S2, the extruder has a first-stage diameter of 90 mm and an aspect ratio of 36, and a second-stage diameter of 120 mm and an aspect ratio of 42.

[0016] Compared with the prior art, the beneficial effects of the present invention are: The present invention proposes a DC 10kV to 35kV chemically cross-linked polyethylene insulation material and its preparation process, which breaks through traditional limitations through multiple innovations. Combining the piezoelectric effect of lead zirconate titanate and the thermoelectric response of bismuth telluride nanosheets, it actively neutralizes charges under electric field and temperature gradients, eliminating space charge accumulation at the source. Barium titanate-coated alumina composite powder forms a dielectric constant gradient interface, smoothing the electric field distribution and suppressing partial discharge. At the same time, the shear-induced orientation process enables the liquid crystal polymer to align in an oriented manner, constructing a molecular-level charge barrier, which significantly improves the breakdown field strength. Furthermore, trace amounts of magnesium oxide are used as charge inhibitors, and efficient utilization is achieved through nanoscale dispersion and surface modification, reducing raw material costs. Detailed Implementation

[0017] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0018] I. Materials: Unless otherwise specified, all chemically cross-linked polyethylene insulation materials for DC 10kV to 35kV proposed in this invention are commercially available. The DC 10kV to 35kV chemically cross-linked polyethylene insulation material is composed of the following raw materials in parts by weight: polyethylene resin: 55-65 parts; charge inhibitor: 1.2 parts; lead zirconate titanate: 1.5-2.5 parts; bismuth telluride nanosheets: 0.8-1.5 parts; cross-linking agent: 1.2-1.8 parts; cross-linking network reinforcing agent: 0.5-1.0 parts; polyaniline microspheres: 0.05-0.12 parts; hexagonal boron nitride nanotubes: 1.0-2.0 parts; medium gradient filler: 3-6 parts; ion trapping agent: 0.3-0.8 parts; flame retardant synergist: 2-4 parts; liquid crystal polymer: 1.5-3.0 parts; zinc mercaptobenzothiazole salt: 0.2-0.5 parts; fluorophlogopite flakes: 4-8 parts; electron trapping agent: 0.1-0.3 parts; The charge suppressor is magnesium oxide.

[0019] It should also be noted that the crosslinking agent is di-tert-butyl peroxide.

[0020] It should also be noted that the cross-linking network reinforcing agent is 4,4'-diaminodiphenyl ether.

[0021] It should also be noted that the medium-gradient filler is barium titanate-coated alumina composite powder.

[0022] It should also be noted that the preparation process of barium titanate-coated alumina composite powder is as follows: A1. Pretreatment of alumina core: Alpha alumina powder with a particle size of 1.8μm was stirred at 60℃ for 30 minutes in a mixed acid solution with a volume ratio of HNO3 / HF = 3:1, and then washed and dried to achieve a purity of ≥99.99%. A2. Plasma activation: The acid-washed powder was treated with 2.45 GHz microwave plasma for 5 minutes in an Ar / O2=4:1 atmosphere to generate Al⁺ active sites on the surface; A3. Gradient coating reaction: The activated powder was subjected to ultrasonic atomization spraying of a mixture of 0.8 mol / L tetrabutyl titanate ethanol solution and 0.5 mol / L barium acetate nano-sol in a fluidized bed at 400℃ to trigger the self-propagating reaction of cerium ammonium nitrate. The powder was then cooled at a gradient from 50℃ / min to 10℃ / min to form an 80nm barium titanate shell. A4. Oxygen vacancy control: The coated powder was then treated at 600°C for 45 minutes in a reducing atmosphere of N2 / H2 = 95:5 to achieve an oxygen vacancy concentration of 10¹. 8 -10¹ 9 cm⁻³; A5. Surface passivation: Finally, the powder is vapor-deposited in tetraethyl orthosilicate vapor at 250℃ / 0.1 MPa for 20 minutes to form a 5-nm amorphous SiO2 layer on the surface, thus obtaining barium titanate-coated alumina composite powder.

[0023] It should also be noted that the flame retardant synergist is zinc borate.

[0024] It should also be noted that the electron trapping agent is molybdenum trioxide.

[0025] It should also be noted that the ion trapping agent is zirconium phosphate.

[0026] II. Process: Based on the above-mentioned DC 10kV to 35kV chemically cross-linked polyethylene insulation material, this invention also proposes a preparation process for a DC 10kV to 35kV chemically cross-linked polyethylene insulation material, comprising the following steps: S1. First, perform pre-dispersion processing of the functional masterbatch using a twin-screw extruder with a screw diameter of 65mm and an aspect ratio of 48. Add 55-65 parts by weight of polyethylene resin, 1.0-2.0 parts by weight of hexagonal boron nitride nanotubes, and 4-8 parts by weight of fluorophlogopite flakes through the main feed port. Control the temperature in Zone 1 to 90℃; Zone 2, 110℃; 120℃ in three zones; Die head temperature 105℃; 1.5-2.5 parts by weight of surface-treated lead zirconate titanate, 0.8-1.5 parts by weight of bismuth telluride nanosheets, and 1.2 parts by weight of magnesium oxide were injected into the side feed port. The screw speed was controlled at 180-220 rpm, and the vacuum degree was maintained at -0.08 to -0.1 MPa. Finally, 0.05-0.12 parts by weight of polyaniline microspheres and 0.3-0.8 parts by weight of zirconium phosphate in ethanol suspension were injected at the end of the melting section. Functional masterbatch with a particle size of about 3 mm was obtained by underwater pelletizing. S2. Then, a dynamic crosslinking reaction is carried out. The functional masterbatch and the remaining polyethylene resin are added from the first-stage feed port using a two-stage reactive extruder and melted at 130-140℃ and 8-12MPa pressure. At the same time, 1.2-1.8 parts by weight of di-tert-butyl peroxide are injected. In the second-stage reaction section at 160-170℃ and 15-18MPa, 0.5-1.0 parts by weight of 4,4'-diaminodiphenyl ether and 1.5-3.0 parts by weight of liquid crystal polymer are injected. At the end of the reaction section, 2-4 parts by weight of zinc borate and 0.1-0.3 parts by weight of molybdenum trioxide premixed powder are added. The mixture is then extruded through a die to form a gel-state substrate. S3. Next, a shear-induced orientation process is implemented. Using a rotational stretch rheometer, the temperature is gradually reduced from 175℃ to 155℃ at a rate of 2℃ / min. At 175℃, the mixture is treated at a shear rate of 3000s⁻¹ for 10 minutes to align the liquid crystal polymer along the extrusion direction. When the temperature is reduced to 165℃, a stretching ratio of 1.8 is applied. Finally, during the 155℃ holding stage, 0.2-0.5 parts by weight of a toluene solution of zinc mercaptobenzothiazole salt is injected to complete the crosslinking network fixation. S4. Finally, gradient vulcanization molding is carried out using a vertical fully automatic vulcanizing tank. First, it is preheated in a nitrogen environment of 140℃ and 0.8MPa for 20-30 minutes, then vulcanized in saturated steam at 185-190℃ and 1.5-1.8MPa for 15-20 minutes. Finally, the pressure is reduced in stages at a rate of 0.05MPa / min, while simultaneously cooling from 160℃ to 80℃ with atomized deionized water. The entire process lasts for 50 minutes.

[0027] It should also be noted that in step S2, the first-stage diameter of the extruder is 90 mm with an aspect ratio of 36, and the second-stage diameter is 120 mm with an aspect ratio of 42.

[0028] Example 1: In this example, DC 10kV to 35kV chemically cross-linked polyethylene insulation material is prepared according to the following process: S1. Functional Masterbatch Pre-dispersion: 60 parts polyethylene resin, 1.5 parts hexagonal boron nitride nanotubes, 5 parts barium titanate-coated alumina composite powder, and 6 parts fluorophlogopite flakes were added to a twin-screw extruder (Φ65mm, L / D=48); Zone 1: 90℃, Zone 2: 110℃, Zone 3: 120℃, Die: 105℃; Side feed injection of 2.0 parts lead zirconate titanate, 1.0 parts bismuth telluride nanosheets, and 1.2 parts magnesium oxide, screw speed: 200 rpm, vacuum degree: -0.09 MPa; At the end of the melt section, 0.08 parts polyaniline microspheres and 0.5 parts zirconium phosphate in ethanol solution were injected, and underwater pelleting was performed to obtain 3mm masterbatch; S2. Dynamic crosslinking reaction: Masterbatch and remaining resin are added to a two-stage extruder (stage 1 Φ90mm L / D=36, stage 2 Φ120mm L / D=42); 1.5 parts of di-tert-butyl peroxide are injected at 135℃ / 10MPa in stage 1; 0.8 parts of 4,4'-diaminodiphenyl ether and 2.0 parts of liquid crystal polymer melt are injected at 165℃ / 16MPa in stage 2; 3 parts of zinc borate and 0.2 parts of molybdenum trioxide are added at the end, and the gel matrix is ​​extruded. S3. Shear-induced orientation: The substrate was sheared at 175°C for 3000 s⁻¹ for 10 min in a rotational rheometer; cooled to 165°C (2°C / min) and subjected to a stretching ratio of 1.8; 0.3 parts of mercaptobenzothiazole zinc salt toluene solution were injected at 155°C; S4. Gradient vulcanization: Preheat with nitrogen at 140℃ / 0.8MPa for 25min; vulcanize with saturated steam at 185℃ / 1.6MPa for 18min; reduce pressure by 0.05MPa / min and cool with atomized water from 160℃ to 80℃ for 50min.

[0029] Example 2: In this example, the amount of polyethylene resin is 55 parts, the amount of lead zirconate titanate is 1.5 parts, and other process parameters are the same as in Example 1. Example 3: In this example, the amount of polyethylene resin is 65 parts, the amount of lead zirconate titanate is 2.5 parts, and other process parameters are the same as in Example 1. Example 4: In this example, the shear rate is 2500 s⁻¹, and other process parameters are the same as in Example 1; Example 5: In this example, the vulcanization temperature is 190°C, and other process parameters are the same as in Example 1. The raw materials and process parameters for Examples 1 to 5 are shown in Table 1: Table 1: Material Composition (parts by weight) of Examples Comparative Example 1: In this comparative example, the amount of polyethylene resin was 50 parts, and other process parameters were the same as in Example 1. Comparative Example 2: In this comparative example, the amount of polyethylene resin was 70 parts, the amount of lead zirconate titanate was 3.0 parts, and other process parameters were the same as in Example 1. Comparative Example 3: In this comparative example, the shear rate was 1500 s⁻¹, and other process parameters were the same as in Example 1. Comparative Example 4: In this comparative example, the shear rate was 4000 s⁻¹, and other process parameters were the same as in Example 1. Comparative Example 5: In this comparative example, the vulcanization temperature was 200°C, and other process parameters were the same as in Example 1. The raw materials and process parameters for Comparative Examples 1 to 5 are shown in Table 2: Table 2: Comparative Example Material Composition (Parts by Weight) III. Performance Testing: Raw material samples were prepared according to the components and process parameters of the examples and comparative examples, and the sample performance was tested according to the following standards: a. Space charge test: 70℃ / 13kV / mm, according to IEC 62895; b. DC breakdown: 20℃ & 70℃, voltage boost rate 1kV / s; c. Electrical tree aging: Record the failure time at 1.8 times the rated voltage (U0=35kV); d. Thermal elongation: 200℃ / 0.2MPa, 15min; The performance parameters of the samples prepared in Examples 1 to 5 are shown in Table 3: Table 3: Performance Comparison of Examples The performance parameters of the samples prepared in Comparative Examples 1 to 5 are shown in Table 4: Table 4: Comparison of Performance of Comparative Examples IV. Data Analysis Conclusions: Based on Tables 1 to 4, the necessity of the component intervals in Examples 1 to 5 of the present invention is verified: In the samples prepared in Examples 1 to 5, 55-65 parts of polyethylene resin were used. In performance tests a, b, c, and d, all properties were superior to those of the comparative examples. Specifically, in Comparative Example 1, 50 parts of polyethylene resin resulted in insufficient melt strength, an extrusion eccentricity of 12%, and a 26% decrease in breakdown field strength. In Comparative Example 2, 70 parts of polyethylene resin resulted in poor crosslinking network density and a thermal elongation deformation rate exceeding 8%. In the samples prepared in Examples 1 to 5, there were 1.5-2.5 parts of lead zirconate titanate. The performance of each item in performance tests a, b, c, and d was better than that of the comparative example. Specifically, in Comparative Example 2, there were 3.0 parts of lead zirconate titanate. Agglomeration caused the space charge density to rise to 0.92 C / m³. Furthermore, since the shear rate of 2500-3500 s⁻¹ in Examples 1 to 5 of the present invention is 2500-3500 s⁻¹, compared with the shear rate of 1500 s⁻¹ in Comparative Example 3, the liquid crystal orientation of Comparative Example 3 is insufficient, and the electrical tree lifetime is reduced by 27%. The shear rate of Comparative Example 4 is 4000 s⁻¹, and the shear heat-induced pre-crosslinking reduces the breakdown field strength by 20%. At the same time, the vulcanization temperature process parameters of the present invention are 185-190℃, while that of Comparative Example 5 is 200℃, which leads to over-vulcanization and embrittlement, and the thermal elongation deformation rate increases to 15.4%. In summary, the component ranges in Examples 1 to 5 of the present invention are scientifically sound.

[0030] Furthermore, because the sample prepared in Example 1 of this invention ensures melt strength with 60 parts polyethylene, maximizes the piezoelectric effect with 2.0 parts lead zirconate titanate, achieves a liquid crystal molecular orientation parameter of 0.82 with a shear rate of 3000 s⁻¹, and optimizes the crosslinking density gradient with vulcanization at 185℃, while also having a space charge density of 0.38 C / m³ and an electrical tree lifetime of >180 h, Example 1 of this invention, through the synergistic optimization of component range and process parameters, achieves a comprehensive breakthrough in core indicators such as charge suppression, electrical strength, and mechanical stability, meeting the 40-year lifespan requirement of ±35kV DC cables. Therefore, Example 1 is the best embodiment of this invention.

[0031] In the description of this specification, references to terms such as "an embodiment," "example," "specific example," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0032] The preferred embodiments of the present invention disclosed above are merely illustrative of the invention. These preferred embodiments do not exhaustively describe all details, nor do they limit the invention to the specific implementations described. Clearly, many modifications and variations can be made based on the content of this specification. This specification selects and specifically describes these embodiments to better explain the principles and practical applications of the invention, thereby enabling those skilled in the art to better understand and utilize the invention. The invention is limited only by the claims and their full scope and equivalents.

Claims

1. A DC 10kV to 35kV chemically cross-linked polyethylene insulation material, characterized in that, It is composed of the following raw materials in parts by weight: polyethylene resin: 55-65 parts; charge inhibitor: 1.2 parts; lead zirconate titanate: 1.5-2.5 parts; bismuth telluride nanosheets: 0.8-1.5 parts; crosslinking agent: 1.2-1.8 parts; crosslinking network reinforcing agent: 0.5-1.0 parts; polyaniline microspheres: 0.05-0.12 parts; hexagonal boron nitride nanotubes: 1.0-2.0 parts; medium gradient filler: 3-6 parts; ion trapping agent: 0.3-0.8 parts; flame retardant synergist: 2-4 parts; liquid crystal polymer: 1.5-3.0 parts; zinc mercaptobenzothiazole: 0.2-0.5 parts; fluorophlogopite flakes: 4-8 parts; electron trapping agent: 0.1-0.3 parts; The charge suppressor is magnesium oxide.

2. The DC 10kV to 35kV chemically cross-linked polyethylene insulation material according to claim 1, characterized in that, The crosslinking agent is di-tert-butyl peroxide.

3. The DC 10kV to 35kV chemically cross-linked polyethylene insulation material according to claim 2, characterized in that, The crosslinking network enhancer is 4,4'-diaminodiphenyl ether.

4. The DC 10kV to 35kV chemically cross-linked polyethylene insulation material according to claim 3, characterized in that, The medium-elasticity filler is barium titanate-coated alumina composite powder.

5. A DC 10kV to 35kV chemically cross-linked polyethylene insulation material according to claim 4, characterized in that, The preparation process of the barium titanate-coated alumina composite powder is as follows: A1. Pretreatment of alumina core: Alpha alumina powder with a particle size of 1.8μm was stirred at 60℃ for 30 minutes in a mixed acid solution with a volume ratio of HNO3 / HF = 3:1, and then washed and dried to achieve a purity of ≥99.99%. A2. Plasma activation: The acid-washed powder was treated with 2.45 GHz microwave plasma for 5 minutes in an Ar / O2=4:1 atmosphere to generate Al⁺ active sites on the surface; A3. Gradient coating reaction: The activated powder was subjected to ultrasonic atomization spraying of a mixture of 0.8 mol / L tetrabutyl titanate ethanol solution and 0.5 mol / L barium acetate nano-sol in a fluidized bed at 400℃ to trigger the self-propagating reaction of cerium ammonium nitrate. The powder was then cooled at a gradient from 50℃ / min to 10℃ / min to form an 80nm barium titanate shell. A4. Oxygen vacancy control: The coated powder was then treated at 600℃ for 45 minutes in a reducing atmosphere of N2 / H2 = 95:5 to achieve an oxygen vacancy concentration of 10¹. 8 -10¹ 9 cm⁻³; A5. Surface passivation: Finally, the powder is vapor-deposited in tetraethyl orthosilicate vapor at 250℃ / 0.1 MPa for 20 minutes to form a 5-nm amorphous SiO2 layer on the surface, thus obtaining barium titanate-coated alumina composite powder.

6. A DC 10kV to 35kV chemically cross-linked polyethylene insulation material according to claim 5, characterized in that, The flame retardant synergist is zinc borate.

7. A DC 10kV to 35kV chemically cross-linked polyethylene insulation material according to claim 6, characterized in that, The electron trapping agent is molybdenum trioxide.

8. A DC 10kV to 35kV chemically cross-linked polyethylene insulation material according to claim 7, characterized in that, The ion trapping agent is zirconium phosphate.

9. The preparation process of a DC 10kV to 35kV chemically cross-linked polyethylene insulating material according to any one of claims 1 to 8, characterized in that, Includes the following steps: S1. First, perform pre-dispersion processing of the functional masterbatch using a twin-screw extruder with a screw diameter of 65mm and an aspect ratio of 48. Add 55-65 parts by weight of polyethylene resin, 1.0-2.0 parts by weight of hexagonal boron nitride nanotubes, and 4-8 parts by weight of fluorophlogopite flakes through the main feed port. Control the temperature in Zone 1 to 90℃; Zone 2, 110℃; 120℃ in Zone 3; Die head temperature 105℃; 1.5-2.5 parts by weight of surface-treated lead zirconate titanate, 0.8-1.5 parts by weight of bismuth telluride nanosheets, and 1.2 parts by weight of magnesium oxide were injected into the side feed port. The screw speed was controlled at 180-220 rpm, and the vacuum degree was maintained at -0.08 to -0.1 MPa. Finally, 0.05-0.12 parts by weight of polyaniline microspheres and 0.3-0.8 parts by weight of zirconium phosphate in ethanol suspension were injected at the end of the melting section. Functional masterbatch with a particle size of about 3 mm was obtained by underwater pelletizing. S2. Then, a dynamic crosslinking reaction is carried out. The functional masterbatch and the remaining polyethylene resin are added from the first-stage feed port using a two-stage reactive extruder and melted at 130-140℃ and 8-12MPa pressure. At the same time, 1.2-1.8 parts by weight of di-tert-butyl peroxide are injected. In the second-stage reaction section at 160-170℃ and 15-18MPa, 0.5-1.0 parts by weight of 4,4'-diaminodiphenyl ether and 1.5-3.0 parts by weight of liquid crystal polymer are injected. At the end of the reaction section, 2-4 parts by weight of zinc borate and 0.1-0.3 parts by weight of molybdenum trioxide premixed powder are added. The mixture is then extruded through a die to form a gel-state substrate. S3. Next, a shear-induced orientation process is implemented. Using a rotational stretch rheometer, the temperature is gradually reduced from 175℃ to 155℃ at a rate of 2℃ / min. At 175℃, the mixture is treated at a shear rate of 3000s⁻¹ for 10 minutes to align the liquid crystal polymer along the extrusion direction. When the temperature is reduced to 165℃, a stretching ratio of 1.8 is applied. Finally, during the 155℃ holding stage, 0.2-0.5 parts by weight of a toluene solution of zinc mercaptobenzothiazole salt is injected to complete the crosslinking network fixation. S4. Finally, gradient vulcanization molding is carried out using a vertical fully automatic vulcanizing tank. First, it is preheated in a nitrogen environment of 140℃ and 0.8MPa for 20-30 minutes, then vulcanized in saturated steam at 185-190℃ and 1.5-1.8MPa for 15-20 minutes. Finally, the pressure is reduced in stages at a rate of 0.05MPa / min, while simultaneously cooling from 160℃ to 80℃ with atomized deionized water. The entire process lasts for 50 minutes.

10. The preparation process of a DC 10kV to 35kV chemically cross-linked polyethylene insulating material according to claim 9, characterized in that, In step S2, the extruder has a first-stage diameter of 90 mm and an aspect ratio of 36, and a second-stage diameter of 120 mm and an aspect ratio of 42.

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