High-voltage-resistant anti-breakdown automobile wire sheath and preparation method thereof

Abstract

The invention relates to a high-voltage-resistant anti-breakdown automobile wire sheath and a preparation method thereof, and relates to the technical field of automobile wire harnesses, and the high-voltage-resistant anti-breakdown automobile wire sheath comprises a modified styrene-ethylene-butylene-styrene block copolymer, polypropylene, functionalized magnesium hydroxide, melamine polyphosphate, white oil and a functional auxiliary agent. An N-vinylcarbazole group grafted on a styrene-ethylene-butylene-styrene block copolymer molecular chain is used as an electron donor, an anthraquinone derivative chemically bonded on the surface of a magnesium hydroxide particle is used as an electron acceptor, and the N-vinylcarbazole group and the anthraquinone derivative form a large number of charge transfer complexes at an interface through pi-pi interaction. According to the charge transfer complexes, a high-density deep energy level trap is introduced into an energy band structure of the material, so that the charge behavior of the material in a high electric field is changed, and high-performance high-voltage-resistant and anti-breakdown effects are realized.

Description

TECHNICAL FIELD

[0001] The application relates to the technical field of automobile wiring harnesses, in particular to a high-voltage-resistant anti-breakdown automobile wire sheath and a preparation method thereof. BACKGROUND

[0002] With the rapid improvement of the electrification and intelligentization level of automobiles, the safety and reliability of automobile wiring harnesses, as the nerve network of the whole vehicle, are crucial. As the first physical barrier wrapped outside the wires, the core function of the harness sheath has long exceeded the basic bundling and storage, and it must provide comprehensive mechanical protection, environmental protection and crucial electrical insulation protection. On the high-voltage platform of new energy vehicles, the working voltage can reach several hundred or even thousands of volts, which puts forward strict requirements on the long-term high-voltage resistance and anti-breakdown performance of the sheath material. Once the insulation of the sheath fails, it may cause short circuit, corona discharge or even breakdown and fire, which seriously endangers the safety of the whole vehicle. Therefore, developing high-performance high-voltage-resistant anti-breakdown sheath material has become one of the key core technologies to ensure the safe development of the new energy vehicle industry.

[0003] At present, the mainstream method in the industry to improve the high-voltage-resistant anti-breakdown performance of automobile wiring harness sheaths is to select or compound engineering plastics or elastomers with high insulation strength as the base material, such as using environmentally friendly flame-retardant thermoplastic elastomers with excellent heat resistance, polyolefin materials with improved molecular chain interaction through irradiation crosslinking, or high-insulation resin such as polytetrafluoroethylene; at the same time, a large amount of inorganic minerals or traditional flame retardants are added to improve the flame retardant grade to meet the safety standards. Some other researches focus on modifying the base resin through chemical copolymerization, such as introducing silicone segments to improve the flexibility and stability of the material at extreme temperatures. However, these existing methods have their inherent limitations, and high proportion of inorganic fillers will seriously damage the mechanical properties and processability, and the filler and base material interface is weak and easy to become an electrical weak point; and the modification of the base resin often has difficulty in constructing a mechanism to suppress the surge of electric charges at the molecular level.

[0004] Therefore, it is of great significance to develop a high-performance high-voltage-resistant anti-breakdown automobile wiring harness sheath. SUMMARY

[0005] The application provides a high-voltage-resistant anti-breakdown automobile wire sheath and a preparation method thereof, which has high-performance high-voltage-resistant anti-breakdown effect.

[0006] In a first aspect, the high-voltage-resistant anti-breakdown automobile wire sheath provided by the application adopts the following technical solution: A high-voltage resistant anti-breakdown automobile wire sheath is composed of the following components in mass percentage: 15-25% of modified styrene-ethylene-butylene-styrene block copolymer, 25-35% of polypropylene, 15-25% of functionalized magnesium hydroxide, 5-15% of melamine polyphosphate, 5-15% of white oil, and 5-15% of functional additives. The modified styrene-ethylene-butylene-styrene block copolymer is a copolymer grafted with N-vinyl carbazole groups; and the functionalized magnesium hydroxide is magnesium hydroxide modified on the surface with anthraquinone derivative groups through chemical bonding.

[0007] By adopting the above technical solution, N-vinyl carbazole is grafted to the molecular chain of the styrene-ethylene-butylene-styrene block copolymer, which gives the copolymer unique electrical functions. The large rigid conjugated structure of the carbazole group as an electron-rich donor can not only effectively suppress the polarization relaxation of the polymer segment under a high electric field to improve the volume resistivity, but more importantly, can have a synergistic effect with the functionalized magnesium hydroxide modified on the surface to become the structural basis for constructing a micro charge transfer mechanism. The anthraquinone carboxylic acid derivative is chemically bonded to the surface of the functionalized magnesium hydroxide particles, so that the inorganic particle surface firmly anchors the electron-deficient acceptor group, giving it electrical functions on its flame-retardant effect.

[0008] When the above two are uniformly dispersed in the continuous phase of polypropylene, the carbazole donors and anthraquinone acceptors distributed at the two-phase interface spontaneously form a large number of micro charge transfer complexes by virtue of the π-π stacking effect. These charge transfer complexes introduce a uniform distribution of deep level traps in the material's forbidden band, forming an energy dissipation network throughout the material body. Under the action of a high-voltage electric field, high-energy electrons accelerated by the field are efficiently captured by these deep level traps before accumulating enough energy to break the chemical bonds of the polymer. Subsequently, the energy of the captured electrons is converted into a small amount of heat energy in the form of exciting lattice vibrations through the charge transfer and relaxation processes within the charge transfer complex, which is non-destructively dissipated, thereby suppressing the carrier multiplication effect that leads to avalanche breakdown. This "electron trap-energy dissipation" mechanism enables the wire sheath to have high-performance high-voltage resistant anti-breakdown effect.

[0009] In addition to the above-mentioned improvement in electrical performance, the interaction between the above-mentioned carbazole donor and anthraquinone acceptor also alleviates the problem of poor interfacial compatibility between inorganic fillers and organic matrix in high polymer composites. Through strong π-π interaction and charge effect, the interfacial adhesion between the modified styrene-ethylene-butylene-styrene block copolymer and the functionalized magnesium hydroxide is enhanced, and this strong interfacial bonding effectively reduces the micron / nanometer-sized pores formed by interfacial debonding or filler agglomeration. The densified microstructure not only pushes up the starting voltage of partial discharge, but also forms a physical barrier to prevent the penetration of water vapor and corrosive media, thereby simultaneously improving the moisture and heat aging resistance of the material. The chemical bonding at the interface also avoids the drawbacks of easy migration of small molecule additives, ensuring the long-term stability of the electrical performance.

[0010] In addition, when the functionalized magnesium hydroxide is thermally decomposed, it plays a solid-phase flame-retardant role by absorbing heat, releasing water vapor, and forming a magnesium oxide barrier layer. The introduction of melamine polyphosphate releases inert gas and promotes matrix carbonization upon thermal decomposition, forming an effective gas-phase and condensed-phase flame-retardant supplement. The synergy of the two enables the material to achieve a high flame-retardant grade at a relatively low total filler load, avoiding the negative impact of high filler content on the mechanical properties and processing flowability of the material. More importantly, the flame-retardant mechanism of the selected melamine polyphosphate does not interfere with the above-mentioned charge transfer complex mechanism, thereby achieving parallel optimization and synergistic gain of flame-retardant performance and high-voltage resistance.

[0011] Optionally, the preparation method of the modified styrene-ethylene-butylene-styrene block copolymer comprises the following steps: S1. Dissolve 2.0-4.0 parts of N-vinylcarbazole, 0.5-1.5 parts of styrene, and 0.05-0.1 parts of dicumyl peroxide in propyl alcohol, and spray onto the surface of 100 parts of styrene-ethylene-butylene-styrene block copolymer, roll mix in a sealed container for 30-35 min, and then stand at room temperature for 12-15 h; S2. Add the S1 mixture to a twin-screw extruder for reactive extrusion grafting, control the reaction section temperature of the extruder at 170-180°C, and the screw rotation speed at 200-250 rpm. After vacuum devolatilization, granulation, and drying, the modified styrene-ethylene-butylene-styrene block copolymer is obtained.

[0012] By adopting the technical scheme, spraying the propanol solution ensures initial uniform distribution of reaction components on the surface of the copolymer, subsequent room temperature standing enables the solvent and monomer to fully penetrate into the interior to reach a swelling state, laying a foundation for subsequent homogeneous grafting. Reactive extrusion is carried out under precise temperature control, which effectively initiates graft polymerization and avoids thermal degradation of the copolymer main chain. In combination with screw rotation speed and vacuum devolatilization, finally, pure and structurally stable modified styrene-ethylene-butylene-styrene block copolymer is obtained, ensuring that the carbazole groups are stably and uniformly grafted on the molecular chain in the form of chemical bonds.

[0013] Optionally, the preparation method of the functionalized magnesium hydroxide comprises the following steps: S1, take 1.0-2.0 parts of KH-550 into a solvent, adjust the pH to 4-5, hydrolyze for 30-40 min, then add 1.5-2.5 parts of anthraquinone carboxylic acid derivative, stir at 60-65℃ for 1-2h; S2, take 100 parts of magnesium hydroxide powder into the solution obtained in S1, reflux and stir at 80-90℃ for 3-5h, after filtration, washing and drying, the functionalized magnesium hydroxide is obtained.

[0014] By adopting the technical scheme, in step S1, the KH-550 is subjected to controllable hydrolysis in a weak acid environment to form active silicon hydroxyl groups, and then reacts with the anthraquinone carboxylic acid derivative at a mild temperature to pre-construct a modifier with both silane coupling agent and anthraquinone acceptor groups. In step S2, the modifier solution is stirred with the magnesium hydroxide powder under reflux conditions for a long time to ensure that the hydrolyzed components at the silane end and the hydroxyl groups on the surface of the magnesium hydroxide undergo sufficient dehydration condensation to form a firm Si-O-Mg chemical bond, thereby chemically anchoring the anthraquinone acceptor group on the surface of the filler.

[0015] Optionally, the anthraquinone carboxylic acid derivative is anthraquinone-2-carboxylic acid or 1-aminoanthraquinone-2-carboxylic acid.

[0016] By adopting the technical scheme, the molecular structures of anthraquinone-2-carboxylic acid and 1-aminoanthraquinone-2-carboxylic acid both contain carboxyl functional groups, ensuring that they can stably undergo amide or ionic bonding reactions with the pre-treated silane coupling agent, thereby being reliably anchored on the surface of the filler. More importantly, both of these derivatives retain the complete anthraquinone planar conjugated structure, making them strong electron acceptors.

[0017] Optionally, the polypropylene is a high-impact copolymerized polypropylene with a melt mass flow rate of 0.5-3.0g / 10min.

[0018] By adopting the technical scheme, the material has optimal processing fluidity when melt blending in the twin-screw extruder, so that the material can fully infiltrate and uniformly coat the modified styrene-ethylene-butylene-styrene block copolymer elastomer and the surface functionalized magnesium hydroxide filler, which is the basis for building a uniform and dense multiphase structure and a stable donor-acceptor interface.

[0019] Optionally, the white oil has a kinematic viscosity of 60-100 mm 2 / s at 40℃.

[0020] By adopting the technical scheme, the specific viscosity range ensures that the white oil has suitable fluidity at the processing temperature, can fully infiltrate and uniformly swell the modified styrene-ethylene-butylene-styrene block copolymer, and promote the uniform dispersion of each component, especially the functionalized filler, in the subsequent mixing process, thereby reducing defects caused by local component unevenness.

[0021] Optionally, the functional aid includes a hindered phenolic antioxidant, an ethylene bis-stearamide lubricant, a maleic anhydride grafted polypropylene compatibilizer, and a triallyl isocyanurate crosslinking aid.

[0022] By adopting the technical scheme, the hindered phenolic antioxidant captures free radicals to inhibit thermal oxidative aging; the lubricant optimizes the melt flowability and demolding property; the maleic anhydride grafted polypropylene as a high-efficiency compatibilizer further promotes the compatibility between the PP phase and the modified SEBS phase, and strengthens the integrity of the multiphase structure; and the crosslinking aid can induce the formation of a moderate crosslinking network under specific conditions, thereby improving the material's resistance to deformation and heat resistance.

[0023] Optionally, a method for preparing a high-pressure-resistant anti-puncture automobile wire sheath includes the following steps: S1, mixing the modified styrene-ethylene-butylene-styrene block copolymer and the white oil according to the ratio, and standing for 12-24h at 35-40℃ to obtain an oil-extended modified elastomer; S2, adding the oil-extended modified elastomer obtained in S1, polypropylene, functionalized magnesium hydroxide, melamine polyphosphate, and a functional aid into a high-speed mixer, stirring at low speed first and then at high speed until the material temperature rises to 80-85℃; S3, melt blending the mixed material obtained in S2 in a twin-screw extruder, with the shear section temperature set to 180-190℃ and the dispersion assembly section temperature set to 195-200℃; S4, extruding, water cooling, granulating, and drying through the extruder die to obtain a high-pressure-resistant anti-puncture automobile wire sheath.

[0024] By adopting the technical scheme, the modified copolymer is subjected to oiling and aging for a long time at 35-40°C in the S1 step, which ensures that the white oil fully and uniformly penetrates and swells the elastomer phase, not only improving the fluidity for subsequent processing, but more importantly, enabling the carbazole groups grafted on the molecular chain of the copolymer to fully stretch, creating conditions for effective contact with the anthraquinone groups on the surface of the filler in subsequent melt blending. The S2 step adopts a step-by-step premixing of low speed first and high speed later, and the material is heated to 80-85°C in stirring, which realizes the initial uniform wrapping and pre-dispersion of all solid components in the elastomer and polypropylene matrix at a temperature lower than the melting point of the polymer, avoiding the decomposition of additives or uneven dispersion that may be caused by direct high-temperature mixing. The S3 melt blending step sets a double-temperature zone, in which the shearing section at 180-190°C mainly completes the melting of polypropylene and the preliminary dispersion of the filler; and the slightly higher temperature dispersion assembly section at 195-200°C provides sufficient thermodynamic power and residence time, promoting the optimized distribution of the oil-filled modified copolymer and polypropylene, and driving the formation and stabilization of the charge transfer complex interface layer between the anthraquinone groups on the surface of the filler and the carbazole groups on the molecular chain of the copolymer. Finally, through the S4 step of extrusion granulation, a wire harness sheath with uniform structure and consistent performance is obtained.

[0025] In summary, the present application includes at least one of the following beneficial technical effects: 1. By grafting N-vinyl carbazole groups on the molecular chain of styrene-ethylene-butylene-styrene block copolymer as electron donors, and chemically bonding anthraquinone derivatives on the surface of magnesium hydroxide particles as electron acceptors, a large number of charge transfer complexes are formed at the interface through π-π interaction. These charge transfer complexes introduce a high density of deep level traps in the energy band structure of the material, thereby changing the charge behavior of the material under high electric field. When a high voltage is applied, the accelerated high-energy electrons are preferentially captured by these deep traps before initiating destructive avalanche multiplication. Subsequently, the energy of the captured electrons is converted into lattice vibration energy in a non-radiative manner through the charge oscillation and relaxation process of the charge transfer complex, improving the high-voltage withstand and anti-breakdown effect of the material. In addition, this strong donor-acceptor interaction enhances the interfacial adhesion between the filler and the polymer matrix, reduces micro defects and pores caused by interfacial incompatibility, and ensures the long-term stability of the electrical performance; 2. Functionalized magnesium hydroxide plays a solid-phase flame-retardant role. Upon heating, it decomposes, absorbing a large amount of heat and releasing water vapor to dilute oxygen and generate a heat-resistant magnesium oxide barrier that covers the polymer surface. Melamine polyphosphate, on the other hand, primarily plays a gas-phase and condensed-phase flame-retardant role. Upon heating, it decomposes to produce non-flammable gases such as ammonia and nitrogen, further diluting flammable gases. Simultaneously, the generated polyphosphates promote the dehydration and carbonization of the polymer matrix, forming a dense and stable expanded char layer. The synergistic effect of these two components creates a complementary flame-retardant effect, achieving a high flame-retardant rating with a relatively low total filler content, avoiding the damage to the material's mechanical properties and processing flowability caused by high filler content. Furthermore, the flame-retardant mechanism of the selected melamine polyphosphate does not interfere with the charge-transfer complex mechanism, thus achieving parallel optimization and synergistic gains in flame-retardant performance and high-voltage insulation performance. Detailed Implementation

[0026] Preparation Example 1 The modified styrene-ethylene-butene-styrene block copolymer is prepared by the following steps: S1. Dissolve 3.0 parts of N-vinylcarbazole, 1.0 part of styrene and 0.55 parts of dicumyl peroxide in propanol, and spray it onto the surface of 100 parts of styrene-ethylene-butene-styrene block copolymer. Mix by rolling in a sealed container for 30 min, and then let it stand at room temperature for 12 h. S2. The mixture from S1 is added to a twin-screw extruder for reactive extrusion grafting. The temperature of the reaction section of the extruder is controlled at 180℃ and the screw speed is 230 rpm. After vacuum devolatilization, pelleting and drying, the modified styrene-ethylene-butene-styrene block copolymer is obtained.

[0027] Preparation Example 2 S1. Take 1.5 parts of KH-550 and add it to the solvent, adjust the pH to 4.5, hydrolyze for 30 min, then add 2.0 parts of anthraquinone-2-carboxylic acid, and stir at 60℃ for 2 h. S2. Take 100 parts of magnesium hydroxide powder and add it to S1 to obtain a solution. Reflux and stir at 85°C for 4 hours. After filtration, washing and drying, functionalized magnesium hydroxide is obtained.

[0028] Example 1 A high-voltage resistant and breakdown-proof automotive wiring sheath is composed of the following components by weight percentage: 15% modified styrene-ethylene-butene-styrene block copolymer, 35% polypropylene, 25% functionalized magnesium hydroxide, 10% melamine polyphosphate, 10% white oil, and 5% functional additives; The modified styrene-ethylene-butylene-styrene block copolymer 15-25% is specifically obtained by Preparation Example 1; the polypropylene is a high-impact copolymerized polypropylene with a melt mass-flow rate of 0.5-3.0 g / 10 min; the functionalized magnesium hydroxide is specifically obtained by Preparation Example 2; the white oil is a hydrogenated naphthenic oil with a kinematic viscosity of 60-100 mm 2 / s at 40℃; and the functional auxiliary is composed of a hindered phenolic antioxidant, an ethylene bis-stearamide lubricant, a maleic anhydride grafted polypropylene compatibilizer, and a triallyl isocyanurate crosslinking auxiliary in a mass ratio of 1:1:1:1.

[0029] A preparation method of a high-pressure-resistant anti-breakdown automobile wire sheath, comprising the following steps: S1, mixing the modified styrene-ethylene-butylene-styrene block copolymer and the white oil according to the proportion, and standing for 12 hours at 40℃ to obtain an oil-extended modified elastomer; S2, adding the oil-extended modified elastomer obtained in S1, the polypropylene, the functionalized magnesium hydroxide, the melamine polyphosphate, and the functional auxiliary into a high-speed mixer, stirring at a low speed first and then at a high speed until the material temperature rises to 80℃; S3, adding the mixture obtained in S2 into a double-screw extruder for melt blending, with the temperature of the shearing section set to 180℃ and the temperature of the dispersion assembly section set to 195℃; S4, extruding through the extruder die, water-cooling, granulating, and drying to obtain a high-pressure-resistant anti-breakdown automobile wire sheath.

[0030] Example 2 A high-pressure-resistant anti-breakdown automobile wire sheath, which is different from Example 1 in that it is composed of the following components in mass percentage: 20% of the modified styrene-ethylene-butylene-styrene block copolymer, 30% of the polypropylene, 20% of the functionalized magnesium hydroxide, 10% of the melamine polyphosphate, 15% of the white oil, and 5% of the functional auxiliary.

[0031] Example 3 A high-pressure-resistant anti-breakdown automobile wire sheath, which is different from Example 1 in that it is composed of the following components in mass percentage: 25% of the modified styrene-ethylene-butylene-styrene block copolymer, 25% of the polypropylene, 15% of the functionalized magnesium hydroxide, 10% of the melamine polyphosphate, 20% of the white oil, and 5% of the functional auxiliary.

[0032] Comparative Example 1 A high-pressure-resistant anti-breakdown automobile wire sheath, which is different from Example 1 in that the modified styrene-ethylene-butylene-styrene block copolymer is replaced by an equal amount of unmodified styrene-ethylene-butylene-styrene block copolymer.

[0033] Comparative Example 2 A high-voltage resistant anti-breakdown automobile wire sheath, which is different from example 1 in that the functional magnesium hydroxide is replaced by an equal amount of ordinary magnesium hydroxide.

[0034] Comparative example 3 A high-voltage resistant anti-breakdown automobile wire sheath, which is different from example 1 in that the melamine polyphosphate is replaced by an equal amount of polypropylene.

[0035] Comparative example 4 A high-voltage resistant anti-breakdown automobile wire sheath, which is different from example 1 in that the modified styrene-ethylene-butylene-styrene block copolymer, functional magnesium hydroxide is replaced by an equal amount of unmodified styrene-ethylene-butylene-styrene block copolymer, ordinary magnesium hydroxide.

[0036] Comparative example 5 A high-voltage resistant anti-breakdown automobile wire sheath, which is different from example 1 in that the mass percentage of polypropylene is 29.5%, and 0.5% of small molecule carbazole is added.

[0037] Test example Dielectric strength: refer to IEC 60243-1, test in oil medium by short-time voltage rise method, take the average value of 5 samples; Volume resistivity: refer to IEC 60093, test at 500V DC voltage using high resistance meter; Flame retardant grade: refer to UL 94, test vertical burning grade of 1.6mm and 3.2mm thickness; Comparative tracking index: refer to IEC 60112, evaluate the material's resistance to tracking performance; Tensile properties: refer to ISO 527-2, test tensile strength and elongation at break; Corona resistance life: refer to modified method of ASTM D2275, test the time of sample to breakdown in air at a certain field strength (25 kV / mm) and frequency; Performance retention rate after long-term heat aging: refer to IEC 60216, test the ratio of dielectric strength to initial value after aging the sample in a 135℃ oven for 168h; The specific test results are shown in Table 1.

[0038] Table 1

[0039] From the performance test data table of Table 1 of Examples 1-3, it can be seen that after adjusting the component ratio, the three examples all maintain good comprehensive performance. Example 2 has higher mechanical strength due to high filler, and Example 3 has better toughness due to high elastomer. This shows that the synergistic system has good formulation adjustment space, and can be optimized according to the different emphasis of wire harness on softness and strength.

[0040] From the performance test data table of Table 1 of Examples 1-3 and Comparative Examples 1-2 and Comparative Example 4, it can be seen that the electrical properties of Comparative Example 1 and Comparative Example 2 all decrease significantly and by a similar magnitude. This shows that a single modification cannot achieve the best effect, and performance improvement depends on the complete charge transfer complex network formed by the interface of the carbazole donor and the anthraquinone acceptor.

[0041] From the performance test data table of Table 1 of Examples 1-3 and Comparative Examples 4-5, it can be seen that by physically mixing small molecule carbazole to simulate the "donor" function, its initial electrical performance is slightly improved compared to Comparative Example 4, but far from Examples 1-3.

[0042] From the performance test data table of Table 1 of Examples 1-3 and Comparative Example 3, it can be seen that the flame retardant level of Comparative Example 3 without melamine polyphosphate is severely reduced to V-2, proving that magnesium hydroxide alone cannot achieve high-grade flame retardation. However, the gap in electrical performance between it and Example 1 is less than other electrical comparative examples, which shows that the addition of melamine polyphosphate, while improving the flame retardant level, has very limited negative impact on the core electrical performance.

[0043] Please note that any combination of the technical features of the above examples can be made. In order to make the description simple, all possible combinations of the technical features in the above examples are not described, however, as long as the combination of the technical features does not exist contradictory, it should be considered as the scope of the description. The above examples only express several embodiments of the present application, and the description is more specific and detailed, but it should not be interpreted as limiting the scope of the patent. It should be noted that for those skilled in the art, without departing from the concept of the present application, a number of modifications and improvements can be made, which are within the scope of the present application. Therefore, the scope of the patent of the present application should be subject to the appended claims.

Claims

1. A high-voltage resistant and breakdown-proof automotive wiring sheath, characterized in that, It is composed of the following components by weight percentage: 15-25% modified styrene-ethylene-butene-styrene block copolymer, 25-35% polypropylene, 15-25% functionalized magnesium hydroxide, 5-15% melamine polyphosphate, 5-15% white oil, and 5-15% functional additives; The modified styrene-ethylene-butene-styrene block copolymer is a copolymer grafted with N-vinylcarbazole groups; the functionalized magnesium hydroxide is magnesium hydroxide with anthraquinone derivative groups chemically bonded to its surface.

2. The high-voltage resistant and breakdown-proof automotive wiring sheath according to claim 1, characterized in that, The preparation method of the modified styrene-ethylene-butene-styrene block copolymer includes the following steps: S1. Dissolve 2.0-4.0 parts of N-vinylcarbazole, 0.5-1.5 parts of styrene and 0.05-0.1 parts of dicumyl peroxide in propanol, and spray it onto the surface of 100 parts of styrene-ethylene-butene-styrene block copolymer. Mix in a sealed container for 30-35 minutes, and then let it stand at room temperature for 12-15 hours. S2. The mixture from S1 is added to a twin-screw extruder for reactive extrusion grafting. The temperature of the reaction section of the extruder is controlled at 170-180℃ and the screw speed is 200-250 rpm. After vacuum devolatilization, pelleting and drying, the modified styrene-ethylene-butene-styrene block copolymer is obtained.

3. The high-voltage resistant and anti-breakdown automotive wiring sheath according to claim 1, characterized in that, The preparation method of the functionalized magnesium hydroxide includes the following steps: S1. Take 1.0-2.0 parts of KH-550 and add it to the solvent. Adjust the pH to 4-5 and hydrolyze for 30-40 minutes. Then add 1.5-2.5 parts of anthraquinone carboxylic acid derivative and stir at 60-65℃ for 1-2 hours. S2. Take 100 parts of magnesium hydroxide powder and add it to S1 to obtain a solution. Reflux and stir at 80-90℃ for 3-5 hours. After filtration, washing and drying, functionalized magnesium hydroxide is obtained.

4. The high-voltage resistant and breakdown-proof automotive wiring sheath according to claim 3, characterized in that, The anthraquinone carboxylic acid derivative is anthraquinone-2-carboxylic acid or 1-aminoanthraquinone-2-carboxylic acid.

5. A high-voltage resistant and anti-breakdown automotive wiring sheath according to claim 1, characterized in that, The polypropylene is a high-impact copolymer polypropylene with a melt flow rate of 0.5-3.0 g / 10 min.

6. The high-voltage resistant and breakdown-proof automotive wiring sheath according to claim 1, characterized in that, The white oil has a kinematic viscosity of 60-100 mm at 40°C. 2 / s of hydrogenated naphthenic oil.

7. A high-voltage resistant and anti-breakdown automotive wiring sheath according to claim 1, characterized in that, The functional additives include hindered phenolic antioxidants, ethylene bis-stearamide lubricants, maleic anhydride-grafted polypropylene compatibilizers, and triallyl isocyanurate crosslinking aids.

8. A method for preparing a high-voltage resistant and breakdown-proof automotive wiring sheath according to any one of claims 1-7, characterized in that, Includes the following steps: S1. The modified styrene-ethylene-butene-styrene block copolymer is mixed with white oil in a certain proportion and allowed to stand for 12-24 hours at 35-40℃ to obtain the oil-extended modified elastomer. S2. Add the oil-extended modified elastomer, polypropylene, functionalized magnesium hydroxide, melamine polyphosphate and functional additives obtained in S1 to a high-speed mixer, stir at low speed first, then stir at high speed until the material temperature rises to 80-85℃. S3. Add the mixture obtained in S2 to a twin-screw extruder for melt blending. Set the temperature of the shearing section to 180-190℃ and the temperature of the dispersion and assembly section to 195-200℃. S4. The high-voltage resistant and anti-breakdown automotive wiring sheath is obtained by extruding through an extruder die, water cooling, pelletizing and drying.

Images