Polypropylene medium-voltage power cable and preparation method thereof

Abstract

The invention discloses a polypropylene medium-voltage power cable which comprises a plurality of twisted shielding insulation wire cores, and an inner protection layer, a metal armor layer and an outer protection layer are sequentially arranged outside the shielding insulation wire cores. The invention also discloses a preparation method of the polypropylene medium-voltage power cable, and further discloses a modified polypropylene insulating material applied to an insulating layer of the polypropylene medium-voltage power cable and a preparation method of the modified polypropylene insulating material, so that the technical problems that an existing cross-linked polyethylene material is relatively poor in thermal stability, difficult to bear relatively high working temperature and relatively large in environmental pollution are solved. Modified polypropylene is good in thermal stability, and compared with an existing cross-linked polyethylene material, the influence of temperature on the electrical property of the modified polypropylene material is remarkably reduced, that is, when the temperature of the modified polypropylene material is 110 DEG C, the breakdown strength of the modified polypropylene material can also keep about 70% of the electrical property at the temperature of 30 DEG C. The modified polypropylene works for a long time under a high-temperature condition, and the same cross section can bear larger current-carrying capacity.

Description

Technical Field

[0001] This invention relates to the field of power engineering materials technology, specifically to a polypropylene medium-voltage power cable and its preparation method. Background Technology

[0002] With the continuous development of society, people's demand for electricity is increasing, which places higher demands on the power grid system. Currently, medium and high voltage power cables use cross-linked polyethylene (XLPE) as insulation material. This material can only maintain its mechanical and electrical properties at a maximum temperature of 90℃, which restricts the further development of cables. Moreover, XLPE is a thermosetting material, cannot be recycled, and can only be incinerated, causing significant environmental pollution. Furthermore, the cross-linking agents used in XLPE production and the byproducts generated during the cross-linking process can ionize impurities under DC high voltage, which exacerbates the accumulation of space charge in the cable insulation layer, leading to electric field distortion and insulation aging, and in severe cases, even partial discharge and insulation breakdown. Simultaneously, its low softening temperature makes it unsuitable for high-temperature operation, and it also suffers from low mechanical strength.

[0003] Polypropylene is a thermoplastic material with good electrical properties, allowing it to operate for extended periods at high temperatures (110°C), making it a viable alternative to cross-linked polyethylene. However, polypropylene has poor toughness and cannot be used directly as an insulating material. Summary of the Invention

[0004] The technical problem this invention aims to solve is that existing cross-linked polyethylene materials have poor thermal stability, making them unable to withstand high operating temperatures and causing significant environmental pollution. The objective is to provide a polypropylene medium-voltage power cable and its preparation method.

[0005] In a first aspect, the present invention is achieved through the following technical solution: A polypropylene medium-voltage power cable includes multiple stranded shielded and insulated cores, with an inner protective layer, a metal armor layer, and an outer protective layer sequentially disposed outside the shielded and insulated cores.

[0006] As one of the preferred technical solutions, the shielded insulated wire core is provided with three wires, each of which includes a copper conductor and a conductor shielding layer, an insulation layer, an insulation shielding layer and a metal shielding layer sequentially wrapped around the copper conductor.

[0007] As one of the preferred technical solutions, the metal armor layer is a double-layer galvanized steel strip with gap wrapping, and the gap ratio is 45-50%.

[0008] As one of the preferred technical solutions, both the inner and outer protective layers are made of low-smoke halogen-free polyolefin materials.

[0009] As one of the preferred technical solutions, a filler strip, two layers of low-smoke halogen-free fiberglass tape, and non-woven fabric are sequentially arranged between the metal shielding layer and the inner protective layer.

[0010] Secondly, the present invention also provides a method for preparing a polypropylene medium-voltage power cable, characterized by comprising the following steps: Copper rods are pulled and retracted to obtain copper monofilaments, which are then twisted together to obtain conductors. The conductor shielding material, the insulation material, and the insulation shielding material are co-extruded into an insulated wire core. Then, a metal shielding layer is wrapped around the insulated wire core with an overlap rate of 5-15%, resulting in a shielded insulated wire core. After multiple shielded and insulated wire cores are twisted together, they are filled with filler strips, and then wrapped with two layers of low-smoke halogen-free fiberglass tape and an outer layer of non-woven fabric to obtain the cable core. A modified polypropylene insulated medium-voltage power cable is obtained by extruding an inner protective layer over the cable core, then wrapping a metal armor layer around it intermittently, and then extruding an outer protective layer on the outside.

[0011] Thirdly, the present invention also provides a modified polypropylene insulating material, applied to the insulation layer of the polypropylene medium-voltage power cable in this embodiment, comprising the following components by weight: 40-60 parts polypropylene, 18-34 parts elastomer material, 4-7 parts ethylene monomer, and nano-... 3-6 parts, silica lime inorganic filler 2-3 parts, and benzoyl peroxide 1-3 parts.

[0012] As one of the preferred technical solutions, the elastomer material comprises the following components by weight: 12-20 parts of hydrogenated styrene-butadiene block copolymer, 3-6 parts of ethylene-vinyl acetate copolymer, and 3-8 parts of ethylene propylene diene monomer (EPDM) rubber.

[0013] Fourthly, a method for preparing a modified polypropylene insulating material includes the following steps: S1, polypropylene, hydrogenated styrene-butadiene block copolymer, ethylene propylene diene monomer rubber, ethylene-vinyl acetate copolymer, and benzoyl peroxide are added to a torque rheometer in a certain proportion for blending. After blending, the mixture is cooled to room temperature by cooling circulating water to form the first blend particles. S2, the first blend particles obtained in step S1, ethylene monomer, nanoparticles Place in a vacuum chamber to dry until all raw materials are dry; S3, the dried first blend particles obtained in step S2, ethylene monomer, and nanoparticles... Add it to the internal mixer in a certain proportion, and let the second blend cool to room temperature; S4. The second blend obtained in step S3 and silica lime are placed in a two-roll mill in a certain proportion at room temperature. After the milling is uniform, the third blend is obtained. S5. Place the third blend obtained in step S4 into a flat vulcanizing machine at a temperature of 200°C for 15 minutes to obtain modified polypropylene insulation material.

[0014] As one of the preferred technical solutions, in step S1, the four temperature zones of the torque rheometer are all set to 200℃, and the rotation speed is set to 60-65 rpm; the mixing time is set to 8-10 minutes; in step S2, the drying temperature of the vacuum chamber is 70℃, and the drying time is 24-28 hours; in step S3, the mixing temperature of the internal mixer is 180-185℃, and the time is 14-17 minutes; in step S4, the open mill temperature is room temperature; and in step S5, the temperature of the flat vulcanizing machine is 200℃, and the time is 15 minutes.

[0015] Compared with the prior art, the present invention has the following advantages and beneficial effects: 1. Modified polypropylene exhibits excellent thermal stability. Compared to existing cross-linked polyethylene materials, the effect of temperature on the electrical properties of the modified polypropylene material in this application is significantly reduced. Specifically, the modified polypropylene material in this application can maintain approximately 70% of its electrical properties at 30°C while retaining its breakdown strength at 110°C. Modified polypropylene can withstand greater current carrying capacity for the same cross-section during prolonged operation at high temperatures.

[0016] 2. The mechanical properties of modified polypropylene are not much different from those of cross-linked polyethylene (XLPE), so it can be used as a substitute for XLPE.

[0017] 3. At the same temperature, modified polypropylene materials have higher volume resistivity and better insulation performance.

[0018] 4. Modified polypropylene is a thermoplastic material that can be repeatedly recycled and is environmentally friendly. Attached Figure Description

[0019] To more clearly illustrate the technical solutions of the exemplary embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly described below. It should be understood that the following drawings only show some embodiments of the present invention and should not be considered as a limitation of the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort. In the drawings: Figure 1 This is a schematic diagram of the structure of the polypropylene medium-voltage power cable of the present invention; The attached diagram shows the markings and corresponding component names: 1-Copper conductor, 2-Conductor shielding layer, 3-Insulation layer, 4-Insulation shielding layer, 5-Metallic shielding layer, 6-Rubber strip, 7-Low smoke halogen-free fiberglass tape, 8-Non-woven fabric, 9-Inner protective layer, 10-Metallic armor layer, 11-Outer protective layer. Detailed Implementation

[0020] To make the objectives, technical solutions, and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the embodiments and accompanying drawings. The illustrative embodiments and descriptions of the present invention are only used to explain the present invention and are not intended to limit the present invention.

[0021] Example 1 like Figure 1 As shown, a modified polypropylene insulated power cable includes three stranded shielded insulated cores. Each insulated core includes a copper conductor and a conductor shielding layer, an insulation layer, an insulation shielding layer, and a metal shielding layer sequentially wrapped around the copper conductor.

[0022] In addition, the shielded and insulated conductor is provided with an inner protective layer, a metal armor layer and an outer protective layer in sequence; the metal armor layer is a double-layer galvanized steel strip with gap wrapping, and the gap ratio is 45-50%; both the inner and outer protective layers are made of low-smoke halogen-free polyolefin materials.

[0023] Furthermore, between the metal shielding layer and the inner protective layer, there are also filler strips, two layers of low-smoke halogen-free fiberglass tape, and non-woven fabric arranged in sequence.

[0024] The modified polypropylene insulation material used in the insulation layer comprises the following components by weight: 40 parts polypropylene (PP), 16 parts hydrogenated styrene-butadiene block copolymer (SEBS), 4 parts ethylene monomer, and nano-... 3 parts, silica lime 2 parts, ethylene propylene diene monomer (EPDM) rubber 4 parts, ethylene-vinyl acetate copolymer (EVA) 3 parts, benzoyl peroxide (BPO) 2 parts; In the aforementioned components, polypropylene, along with elastomers such as hydrogenated styrene-butadiene block copolymer (SEBS), ethylene propylene diene monomer (EPDM), and ethylene-vinyl acetate copolymer (EVA), exists as a dispersed phase within the continuous PP matrix in the PP / elastomer blend system. With the application of strain, the elastomer absorbs some energy and transfers stress to the surrounding PP matrix through plastic deformation, thereby preventing crack propagation. This mechanism is known as the "crazing" effect; when subjected to external forces, microcracks (crazing) are generated in the PP matrix, and these crazings are terminated by the elastomer particles, preventing further fracture and significantly improving the toughness of the polypropylene material.

[0025] Benzoyl peroxide (BPO) can decompose at higher temperatures to generate free radicals, which, in the molten state, can promote the grafting reaction between the elastomer and the PP polymer. The preferred mass ratio of polypropylene (PP) to hydrogenated styrene-butadiene block copolymer (SEBS) is (1.5-4):1. SEBS, as a novel elastomer material, effectively enhances the toughness of polypropylene (PP) when grafted onto it.

[0026] Ethylene monomers and nano The addition of [a specific ingredient] effectively improves the insulation performance of polypropylene blends. A large number of deep trap energy levels are introduced at the microscopic interfaces between the polymer monomers and nanoparticles and the matrix material. These deep trap energy levels can trap high-speed charge carriers, reducing their mobility. Simultaneously, the trapped charges can improve the electric field distribution near the electrodes, ultimately enhancing the insulation performance.

[0027] Silica lime, an inorganic filler, can effectively improve the heat resistance, dimensional stability, and hardness of polypropylene blends. The principle behind this is that it allows for the uniform dispersion of various elastomers and functional groups within the PP-based material. Furthermore, silica lime is inexpensive, which can reduce the production cost of polypropylene materials.

[0028] A method for preparing modified polypropylene insulation material: S1. Polypropylene (PP), hydrogenated styrene-butadiene block copolymer (SEBS), ethylene propylene diene monomer (EPDM), ethylene-vinyl acetate copolymer (EVA), and benzoyl peroxide (BPO) were added to a torque rheometer for blending. All four temperature zones of the torque rheometer were set to 200℃, the rotation speed to 60 r / min, and the blending time to 8 min. After cooling to room temperature using circulating cooling water, the first blend particles were prepared. Specifically, 20 g of polypropylene (PP), 8 g of hydrogenated styrene-butadiene block copolymer (SEBS), 2 g of ethylene propylene diene monomer (EPDM), 1.5 g of ethylene-vinyl acetate copolymer (EVA), and 1 g of benzoyl peroxide (BPO) were added.

[0029] S2, the first blend particles obtained in step S1, ethylene monomer, nanoparticles The raw materials were dried in a 70℃ vacuum oven for 24 hours to ensure complete drying. Ethylene monomer and nano-polymers were added during this process. The weights are 2g and 1.5g respectively.

[0030] S3, in step S2, the dried first blend particles, ethylene monomer, and nanoparticles... Add the mixture to a mixing mill in a certain proportion. Set the temperature in the mixing mill to 180°C and the time to 15 minutes. Then let the second blend cool to room temperature.

[0031] S4. The second blend obtained in step S3 and silica lime are placed in a two-roll mill at a certain ratio and the temperature is room temperature. After milling until homogeneous, a third blend is obtained. The amount of silica lime used is 1g.

[0032] S5. Place the third blend obtained in step S4 into a flat vulcanizing machine at a temperature of 200°C for 15 minutes to obtain the modified polypropylene insulation material.

[0033] A method for preparing a modified polypropylene insulated power cable: The round copper rod is drawn and retracted to the required outer diameter using a 13-die copper wire drawing machine, and then twisted together to obtain the conductor. Specifically, the outer diameter of the round copper rod is preferably 8mm.

[0034] The conductor shielding material, the modified polypropylene insulation material prepared above, and the insulation shielding material are sequentially extruded onto the stranded conductor through a three-layer co-extrusion process to obtain an insulated wire core. Specifically, both the conductor shielding material and the insulation shielding material include ethylene-propylene rubber (EPR) and its copolymers, carbon nanotubes and graphene, crosslinking agents, antioxidants, and processing aids; all materials are well-known components and will not be described in detail here.

[0035] In this embodiment, the metal shielding layer is a copper strip, and the copper strip thickness is preferably 1.2 mm; then the copper strip is wrapped around the insulated wire core to obtain the shielded insulated wire core.

[0036] The three obtained shielded and insulated cores are twisted together and filled with filler strips, with the filler strips accounting for 4-5% of the total cable weight. Then, two layers of low-smoke halogen-free fiberglass tape and one layer of non-woven fabric are wrapped around the outside to obtain the cable core. The thickness of both the low-smoke halogen-free fiberglass tape and the non-woven fabric is 0.2 mm.

[0037] A low-smoke, halogen-free polyolefin inner protective layer is extruded over the cable core, and two layers of galvanized steel strip (metal armor layer) are wrapped around the outer gap to obtain the armored wire core, wherein the steel strip is 0.5mm thick.

[0038] A layer of low-smoke halogen-free polyolefin sheath is extruded over the armored conductor. The sheath thickness is controlled to be 1.5~5.0mm according to the size of the cable cross-section, thus obtaining a modified polypropylene insulated power cable.

[0039] Test results: In terms of mechanical strength, the modified polypropylene insulated power cable prepared in Example 1 had an elongation at break of 465% and a tensile strength of 32 MPa; in terms of electrical properties, at a temperature of 30°C, the volume resistivity of the modified polypropylene insulated power cable was... The breakdown strength is 492 kV / mm, and the volume resistivity of the modified polypropylene insulated power cable is Ω·m. The breakdown strength is 421 kV / mm, and the volume resistivity of the modified polypropylene insulated power cable is Ω·m. Ω・m, breakdown strength is 342kV / mm.

[0040] Example 2 Based on Example 1, the modified polypropylene insulation material formulation in this example is: 50 parts polypropylene (PP), 12 parts hydrogenated styrene-butadiene block copolymer (SEBS), 6 parts ethylene monomer, and nano-... 4.2 parts, silica lime 2.2 parts, ethylene propylene diene monomer (EPDM) rubber 3 parts, ethylene-vinyl acetate copolymer (EVA) 3.6 parts, benzoyl peroxide (BPO) 2.4 parts.

[0041] Preparation method of modified polypropylene insulation material: Same as steps S1-S5 of Example 1, except that in step S3, the mixing temperature is 183℃ and the time is 16 minutes. The following are added: 25g polypropylene (PP), 6g hydrogenated styrene-butadiene block copolymer (SEBS), 1.5g ethylene propylene diene monomer (EPDM), 1.8g ethylene-vinyl acetate copolymer (EVA), 1.2g benzoyl peroxide (BPO), 3g ethylene monomer, and nano-polymers. 2.1g and silica lime 1.1g.

[0042] Preparation method of modified polypropylene insulated power cable: The steps are roughly the same as those in Example 1, except that the filling amount of the filler strip is increased by 8%.

[0043] Test results: In terms of mechanical strength, the modified polypropylene insulated power cable prepared in Example 2 had an elongation at break of 483% and a tensile strength of 31 MPa; in terms of electrical properties, at a temperature of 30°C, the volume resistivity of the modified polypropylene insulated power cable was... The breakdown strength is 462 kV / mm, and the volume resistivity of the modified polypropylene insulated power cable is Ω·m. The breakdown strength is 397 kV / mm, and the volume resistivity of the modified polypropylene insulated power cable is Ω·m. Ω・m, breakdown strength is 321kV / mm.

[0044] Example 3 Modified polypropylene insulation material formulation: 36 parts polypropylene (PP), 20 parts hydrogenated styrene-butadiene block copolymer (SEBS), 4 parts ethylene monomer, nano... 3.4 parts, silica lime 2.4 parts, ethylene propylene diene monomer (EPDM) rubber 4.8 parts, ethylene-vinyl acetate copolymer (EVA) 4 parts, benzoyl peroxide (BPO) 1.6 parts. Among these, 18g of polypropylene (PP), 10g of hydrogenated styrene-butadiene block copolymer (SEBS), 2.4g of EPDM rubber, 2g of ethylene-vinyl acetate copolymer (EVA), 0.8g of benzoyl peroxide (BPO), 2g of ethylene monomer, and nano- 1.7g and silica lime 1.2g.

[0045] Preparation method: Follow the steps S1-S5 of Example 1, except that the drying time in step S2 is 28 hours and the mixing temperature in step S3 is 182°C and the time is 17 minutes.

[0046] Preparation of modified polypropylene insulated power cable: The steps are the same as in Example 1, except that the wrapping gap ratio of galvanized steel strip is 46%.

[0047] Test results: In terms of mechanical strength, the modified polypropylene insulated power cable prepared in Example 3 had an elongation at break of 501% and a tensile strength of 29 MPa; in terms of electrical properties, at a temperature of 30°C, the volume resistivity of the modified polypropylene insulated power cable was... The breakdown strength is 452 kV / mm, and the volume resistivity of the modified polypropylene insulated power cable is Ω·m. The breakdown strength is 387 kV / mm, and the volume resistivity of the modified polypropylene insulated power cable is Ω·m. Ω・m, breakdown strength is 313kV / mm.

[0048] Example 4 Modified polypropylene insulation material formulation: 60 parts polypropylene (PP), 15 parts hydrogenated styrene-butadiene block copolymer (SEBS), 7 parts ethylene monomer, nano... 5.2 parts, silica lime 3 parts, ethylene propylene diene monomer (EPDM) rubber 8 parts, ethylene-vinyl acetate copolymer (EVA) 6 parts, benzoyl peroxide (BPO) 2 parts.

[0049] Preparation method: Follow steps S1-S5 of Example 1, except that in step S1, the torque rheometer speed is adjusted to 62 r / min and the mixing time is 8.5 minutes; in step S3, the mixing temperature is 185℃ and the time is 14 minutes. The following components are added: 30g polypropylene (PP), 7.5g hydrogenated styrene-butadiene block copolymer (SEBS), 4g ethylene propylene diene monomer (EPDM), 3g ethylene-vinyl acetate copolymer (EVA), 1g benzoyl peroxide (BPO), 3.5g ethylene monomer, and nano-polymers. 2.6g and silica lime 1.5g.

[0050] Preparation of modified polypropylene insulated power cable: The steps of Example 1 are followed, except that the extrusion thickness of the outer protective layer is increased by 0.1 mm.

[0051] Test results: In terms of mechanical strength, the modified polypropylene insulated power cable prepared in Example 4 had an elongation at break of 523% and a tensile strength of 28 MPa; in terms of electrical properties, at a temperature of 30°C, the volume resistivity of the modified polypropylene insulated power cable was... The breakdown strength is 425 kV / mm, and the volume resistivity of the modified polypropylene insulated power cable is Ω·m. The breakdown strength is 364 kV / mm, and the volume resistivity of the modified polypropylene insulated power cable is Ω·m. Ω・m, breakdown strength is 294kV / mm.

[0052] Comparative Example 1 (XLPE): The steps are largely the same as in Example 1, except that cross-linked polyethylene (XLPE) insulation is used as the insulation layer, ultimately resulting in a XLPE insulated power cable. It should be noted that the preparation method of XLPE insulation differs from that of modified polypropylene insulation. XLPE insulation is typically produced by mixing polyethylene with a cross-linking agent (such as peroxide or silane) and then subjecting the polyethylene molecular chains to a cross-linking reaction through processes such as heating.

[0053] Based on the mechanical and electrical performance tests conducted on the cross-linked polyethylene and polypropylene power cables obtained in the various embodiments, as shown in Tables 1 and 2, the following data were obtained: Table 1 Comparison of Mechanical Strength

[0054] Table 2 Comparison of Electrical Performance

[0055] The above experiments revealed that the polypropylene insulated power cables prepared in Examples 1-4 are significantly superior to the cross-linked polyethylene insulated power cables in terms of mechanical strength and electrical performance; among them, Example 1 has the best performance.

[0056] Furthermore, at the same temperature, the modified polypropylene material exhibits higher volume resistivity and better insulation performance. At different temperatures, the effects of Examples 1-4 on the material are significantly reduced compared to cross-linked polyethylene. This indicates that the modified polypropylene insulated power cable can withstand a higher temperature range than cross-linked polyethylene material and can carry a greater current-carrying capacity at the same cross-section.

[0057] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A polypropylene medium-voltage power cable, characterized in that, It includes multiple stranded shielded and insulated wire cores, with an inner protective layer, a metal armor layer, and an outer protective layer arranged sequentially around the shielded and insulated wire cores.

2. The polypropylene medium-voltage power cable according to claim 1, characterized in that, The shielded insulated wire core is provided with three wires. Each shielded insulated wire core includes a copper conductor and a conductor shielding layer, an insulation layer, an insulation shielding layer and a metal shielding layer that are sequentially wrapped around the copper conductor.

3. The polypropylene medium-voltage power cable according to claim 1, characterized in that, The metal armor layer is a double-layer galvanized steel strip with gap wrapping, and the gap ratio is 45-50%.

4. The polypropylene medium-voltage power cable according to claim 1, characterized in that, Both the inner and outer protective layers are made of low-smoke halogen-free polyolefin materials.

5. The polypropylene medium-voltage power cable according to claim 2, characterized in that, Between the metal shielding layer and the inner protective layer, there are also filler strips, two layers of low-smoke halogen-free fiberglass tape and non-woven fabric arranged in sequence.

6. A method for preparing a polypropylene medium-voltage power cable, characterized in that, Includes the following steps: Copper rods are pulled and retracted to obtain copper monofilaments, which are then twisted together to obtain conductors. The conductor shielding material, the insulation material, and the insulation shielding material are co-extruded into an insulated wire core. Then, a metal shielding layer is wrapped around the insulated wire core with an overlap rate of 5-15%, resulting in a shielded insulated wire core. After multiple shielded and insulated wire cores are twisted together, they are filled with filler strips, and then wrapped with two layers of low-smoke halogen-free fiberglass tape and an outer layer of non-woven fabric to obtain the cable core. An inner protective layer is extruded over the cable core, and then a metal armor layer is wrapped around it intermittently to obtain an armored core. Finally, an outer protective layer is extruded over the outer side to obtain a modified polypropylene insulated medium-voltage power cable.

7. A modified polypropylene insulating material, used in the insulation layer of a polypropylene medium-voltage power cable according to any one of claims 1-5, characterized in that, The composition by weight includes the following components: 40-60 parts polypropylene, 18-34 parts elastomer material, 4-7 parts ethylene monomer, and nano-materials. 3-6 parts, silica lime inorganic filler 2-3 parts, and benzoyl peroxide 1-3 parts.

8. The modified polypropylene insulating material according to claim 7, characterized in that, The elastomer material comprises the following components by weight: 12-20 parts of hydrogenated styrene-butadiene block copolymer, 3-6 parts of ethylene-vinyl acetate copolymer, and 3-8 parts of ethylene propylene diene monomer (EPDM) rubber.

9. A method for preparing a modified polypropylene insulating material, characterized in that, Includes the following steps: S1, polypropylene, hydrogenated styrene-butadiene block copolymer, ethylene propylene diene monomer rubber, ethylene-vinyl acetate copolymer, and benzoyl peroxide are added to a torque rheometer in a certain proportion for blending. After blending, the mixture is cooled to room temperature by cooling circulating water to form the first blend particles. S2, the first blend particles obtained in step S1, ethylene monomer, nanoparticles Place in a vacuum chamber to dry until all raw materials are dry; S3, the dried first blend particles obtained in step S2, ethylene monomer, and nanoparticles... Add it to the internal mixer in a certain proportion, and let the second blend cool to room temperature; S4. The second blend obtained in step S3 and silica lime are put into a two-mill in a certain proportion and milled until uniform to obtain the third blend. S5. The third blend obtained in step S4 is placed into a flat vulcanizing machine to finally obtain modified polypropylene insulation material.

10. The method for preparing the modified polypropylene insulation material according to claim 9, characterized in that, In step S1, the four temperature zones of the torque rheometer are all set to 200℃, and the rotation speed is set to 60-65 rpm; the blending time is set to 8-10 minutes; in step S2, the drying temperature of the vacuum chamber is 70℃, and the drying time is 24-28 hours; in step S3, the internal mixer temperature is 180-185℃, and the time is 14-17 minutes; in step S4, the open mill temperature is room temperature; in step S5, the flat vulcanizing machine temperature is 200℃, and the time is 15 minutes.

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