Low-smoke high-temperature-resistant polyolefin sheath high-voltage cable for charging electric vehicle

Abstract

The invention relates to the technical field of electric vehicle high-voltage cables, in particular to a low-smoke high-temperature-resistant polyolefin sheath high-voltage cable for charging an electric vehicle. The low-smoke high-temperature-resistant polyolefin sheath high-voltage cable for charging the electric vehicle comprises a cable core and a low-smoke high-temperature-resistant polyolefin sheath layer wrapping the outer side of the cable core, the low-smoke high-temperature-resistant polyolefin sheath layer is prepared from the following raw materials in parts by mass: 80 to 120 parts of high-density polyethylene, 10 to 40 parts of linear low-density polyethylene, 10 to 30 parts of ethylene-vinyl acetate copolymer, 1 to 5 parts of carboxyl-terminated nitrile rubber, 15 to 35 parts of carbon black, 1 to 3 parts of graphene oxide, 1.01 to 2.1 parts of silane coupling agent KH560, 1 to 2 parts of cross-linking agent, 2 to 8 parts of processing aid, 1 to 2 parts of antioxidant and 1 to 2 parts of light stabilizer.

Description

Technical Field

[0001] The present invention relates to the technical field of electric vehicle high-voltage cables, and in particular to a low-smoke, high-temperature-resistant polyolefin sheathed high-voltage cable for charging electric vehicles. Background Art

[0002] The wiring system of new energy electric vehicles can be divided into high-voltage system and low-voltage system. During the transmission of electric energy, high-voltage cables will generate electromagnetic waves in the surrounding area, which will affect the signal transmission of the control line. Usually, a shielding layer needs to be added outside the high-voltage wire core. The high-temperature resistant charging and distribution shielded busbar of new energy electric vehicles is very important for automotive cables.

[0003] According to the different sheath layers of high-voltage cables, they can be divided into oil-impregnated paper insulated high-voltage cables, rubber insulated high-voltage cables, and cross-linked polyolefin high-voltage cables. Oil-impregnated paper insulated high-voltage cables were developed earlier, but are prone to oil dripping; there are many types of rubber insulated high-voltage cables, the rubber is soft and has good bending performance, but the ozone resistance is poor, and they are mostly used for power cables with lower voltage levels.

[0004] Cross-linked polyolefin high-voltage cables have excellent comprehensive performance and good aging resistance, and are particularly advantageous in large current-carrying and high-drop environments. However, there is still a problem that the bent parts are very prone to aging and cracking due to fatigue when bent in use, and the high temperature resistance is poor, which needs to be solved urgently. Summary of the invention

[0005] The purpose of the present invention is to solve the shortcomings of the prior art and to propose a low-smoke, high-temperature-resistant polyolefin sheathed high-voltage cable for charging electric vehicles.

[0006] A low-smoke, high-temperature-resistant polyolefin sheathed high-voltage cable for charging electric vehicles, comprising a cable core and a low-smoke, high-temperature-resistant polyolefin sheath layer coated on the outside of the cable core; the raw materials of the low-smoke, high-temperature-resistant polyolefin sheath layer include, by mass: 80-120 parts of high-density polyethylene, 10-40 parts of linear low-density polyethylene, 10-30 parts of ethylene-vinyl acetate copolymer, 1-5 parts of terminal carboxyl nitrile rubber, 15-35 parts of carbon black, 1-3 parts of graphene oxide, 1.01-2.1 parts of silane coupling agent KH560, 1-2 parts of cross-linking agent, 2-8 parts of processing aid, 1-2 parts of antioxidant, and 1-2 parts of light stabilizer.

[0007] Preferably, the cross-linking agent is at least one of dicumyl peroxide, dibenzoyl peroxide, and tert-butyl hydroperoxide.

[0008] Preferably, the processing aid is polyethylene wax and / or silicone powder.

[0009] Preferably, the antioxidant is at least one of antioxidant 1010, antioxidant BHT, antioxidant DNP, and antioxidant TNP.

[0010] Preferably, the light stabilizer is at least one of light stabilizer 119, light stabilizer 292, light stabilizer 770, light stabilizer 944, and light stabilizer M535.

[0011] The preparation method of the above-mentioned low-smoke and high-temperature-resistant polyolefin sheath high-voltage cable for electric vehicle charging includes the following steps:

[0012] S1. Add carbon black and graphene oxide to anhydrous ethanol, ultrasonically treat for 1 - 2 h, add silane coupling agent KH560, stir at 60 - 80 °C for 1 - 2 h, filter, wash, dry, and pulverize to obtain pretreated carbon black;

[0013] S2. Add carboxyl-terminated nitrile rubber to the pretreated carbon black, homogenize at 150 - 170 °C for 1 - 5 min, mix at 80 - 95 °C for 1 - 2 h, add high-density polyethylene, linear low-density polyethylene, ethylene-vinyl acetate copolymer, antioxidant, crosslinking agent, processing aid, carbon black, silane coupling agent KH560, and light stabilizer, knead at 80 - 95 °C for 20 - 30 min to obtain a premix;

[0014] S3. Extrude the premix to coat the outside of the cable core and dry.

[0015] Preferably, in S1, the ultrasonic frequency is 50 - 60 kHz.

[0016] Preferably, the mass ratio of the carbon black used in S1 to the carbon black used in S2 is 10 - 20:5 - 15.

[0017] Preferably, the mass ratio of the silane coupling agent used in S1 to the silane coupling agent used in S2 is 0.01 - 0.1:1 - 2.

[0018] Preferably, in S3, a twin-screw extruder is used for extrusion, and the temperatures of each zone of the twin-screw extruder are: zone 1: 120 - 140 °C, zone 2: 145 - 152 °C, zone 3: 160 - 170 °C, zone 4: 175 - 185 °C, and the head: 180 - 190 °C.

[0019] Beneficial effects:

[0020] The high-voltage cable of the present invention has both excellent shielding effect, is resistant to high temperature of 125 °C, has high tensile strength and excellent impact resistance, can meet the long-term use of new energy electric vehicles under harsh conditions, and is especially used for high-power shielded busbars for electric vehicle charging and power distribution, having excellent prospects.

[0021] The present invention utilizes the compounding of carbon black and graphene oxide, and binds an organic adsorption layer on its surface. It not only has high heat resistance stability, but also effectively improves its dispersibility in the matrix, has better interfacial compatibility, and the carboxyl groups in the carboxyl-terminated nitrile rubber further react with epoxy groups to bind nitrile copolymer segments in the organic layer. When subjected to external force impact, stress can be buffered, absorbed and dispersed through molecular chains, improving the toughness of the polyethylene matrix; at the same time, under the action of a cross-linking agent, it can entangle with the polyethylene matrix to form a more stable network structure, significantly improving the high-temperature resistance of the polyethylene matrix and reducing the occurrence of fire accidents.

[0022] The present invention uses polyethylene as the main component, and prepares a sheath layer by compounding carboxyl-terminated nitrile rubber, ethylene-vinyl acetate copolymer and other auxiliary materials. It not only endows the high-voltage cable with excellent impact resistance and high-temperature resistance at 125 °C, but also has a remarkable smoke suppression effect.

[0023] The present invention uses a polyolefin resin with excellent performance as the base material. It not only has a low carbon black content, but also the obtained sheath layer has good shielding effect, making the cable have very good mechanical properties and anti-cracking properties. It is suitable for the high-voltage cable sheath layer with high requirements for mechanical properties, anti-cracking and high-temperature resistance, etc., and can better ensure the normal use and operation of the cable. At the same time, the preparation process of the present invention is simple, with small equipment investment, high efficiency and low cost. Brief Description of the Drawings

[0024] Figure 1 It is a comparison chart of the tensile strength and impact strength of the polyolefin sheath layers of the high-voltage cables obtained in Example 5 and Comparative Examples 1-2.

[0025] Figure 2 It is a comparison chart of the electromagnetic shielding effectiveness of the high-voltage cables obtained in Example 5 and Comparative Examples 1-2 and the retention rate of electromagnetic shielding effectiveness after heat treatment at 125 °C for 168 h.

[0026] Figure 3 It is a comparison chart of the retention rate of tensile strength and impact strength of the polyolefin sheath layers of the high-voltage cables obtained in Example 5 and Comparative Examples 1-2 after heat treatment at 125 °C for 168 h.

[0027] Figure 4 It is a comparison chart of the shrinkage rate of the polyolefin sheath layers of the high-voltage cables obtained in Example 5 and Comparative Examples 1-2. Detailed Embodiments

[0028] The present invention will be further explained below in conjunction with specific embodiments.

[0029] Example 1

[0030] A low-smoke and high-temperature resistant polyolefin sheath high-voltage cable for electric vehicle charging, comprising a cable core and a low-smoke and high-temperature resistant polyolefin sheath layer wrapped outside the cable core; the raw materials of the low-smoke and high-temperature resistant polyolefin sheath layer include: 8000 g of high-density polyethylene, 1000 g of linear low-density polyethylene, 1000 g of ethylene-vinyl acetate copolymer, 100 g of carboxyl-terminated nitrile rubber, 1500 g of carbon black, 100 g of graphene oxide, 101 g of silane coupling agent KH560, 100 g of dibenzoyl peroxide, 200 g of silicone powder, 100 g of antioxidant DNP, and 100 g of light stabilizer 119.

[0031] The preparation method of the above-mentioned low-smoke and high-temperature resistant polyolefin sheath high-voltage cable for electric vehicle charging comprises the following steps:

[0032] S1. Add 1500 g of carbon black and graphene oxide to 5000 g of absolute ethanol, ultrasonically treat for 1 h, the ultrasonic frequency is 50 kHz, add 1 g of silane coupling agent KH560, stir at a temperature of 60 °C for 1 h, the stirring speed is 100 r / min, filter, wash with deionized water, vacuum dry, and pulverize to obtain pretreated carbon black;

[0033] S2. Add carboxyl-terminated nitrile rubber to the pretreated carbon black, homogenize at a high speed at a temperature of 150 °C for 1 min, the homogenization speed is 5000 r / min, mix at a temperature of 80 °C for 1 h, send it into a high-speed kneader, add high-density polyethylene, linear low-density polyethylene, ethylene-vinyl acetate copolymer, antioxidant DNP, dibenzoyl peroxide, silicone powder, 500 g of carbon black, 100 g of silane coupling agent KH560, and light stabilizer 119, stir at a speed of 300 r / min for 20 min, and the kneading temperature is 80 °C to obtain a premix;

[0034] S3. Send the premix into a twin-screw extruder to extrude and wrap it outside the cable core, and place it in a blast drying oven to dry at a temperature of 80 °C for 2 h;

[0035] Among them, the temperatures of each zone of the twin-screw extruder are: zone 1 is 120 °C, zone 2 is 145 °C, zone 3 is 160 °C, zone 4 is 175 °C, and the die head is 180 °C.

[0036] Example 2

[0037] A low-smoke and high-temperature resistant polyolefin sheath high-voltage cable for electric vehicle charging, comprising a cable core and a low-smoke and high-temperature resistant polyolefin sheath layer coated on the outer side of the cable core; the raw materials of the low-smoke and high-temperature resistant polyolefin sheath layer include: 12000 g of high-density polyethylene, 4000 g of linear low-density polyethylene, 3000 g of ethylene-vinyl acetate copolymer, 500 g of carboxyl-terminated nitrile rubber, 3500 g of carbon black, 300 g of graphene oxide, 210 g of silane coupling agent KH560, 200 g of tert-butyl hydroperoxide, 800 g of silicone powder, 200 g of antioxidant TNP, and 200 g of light stabilizer 2922.

[0038] The preparation method of the above-mentioned low-smoke and high-temperature resistant polyolefin sheath high-voltage cable for electric vehicle charging comprises the following steps:

[0039] S1. Add 2000 g of carbon black and graphene oxide into 10000 g of absolute ethanol, ultrasonically treat for 2 h, the ultrasonic frequency is 60 kHz, add 10 g of silane coupling agent KH560, stir at a temperature of 80 °C for 2 h, the stirring speed is 500 r / min, filter, wash with deionized water, and vacuum dry to obtain pretreated carbon black.

[0040] S2. Add carboxyl-terminated nitrile rubber to the pretreated carbon black, homogenize at a high speed at a temperature of 170 °C for 5 min, the homogenization speed is 10000 r / min, mix at a temperature of 95 °C for 2 h, feed it into a high-speed kneader, add high-density polyethylene, linear low-density polyethylene, ethylene-vinyl acetate copolymer, antioxidant TNP, tert-butyl hydroperoxide, silicone powder, 1500 g of carbon black, 200 g of silane coupling agent KH560, and light stabilizer 292, stir at a speed of 600 r / min for 30 min, and the kneading temperature is 95 °C to obtain a premix.

[0041] S3. Feed the premix into a twin-screw extruder to extrude and coat it on the outer side of the cable core, and place it in a blast drying oven to dry at a temperature of 90 °C for 4 h.

[0042] Among them, the temperatures of each zone of the twin-screw extruder are: zone 1 is 140 °C, zone 2 is 152 °C, zone 3 is 170 °C, zone 4 is 185 °C, and the head is 190 °C.

[0043] Example 3

[0044] A low-smoke and high-temperature resistant polyolefin sheath high-voltage cable for electric vehicle charging, comprising a cable core and a low-smoke and high-temperature resistant polyolefin sheath layer wrapped around the outer side of the cable core; the raw materials of the low-smoke and high-temperature resistant polyolefin sheath layer include: 9000 g of high-density polyethylene, 3000 g of linear low-density polyethylene, 1500 g of ethylene-vinyl acetate copolymer, 400 g of carboxyl-terminated nitrile rubber, 2600 g of carbon black, 150 g of graphene oxide, 178 g of silane coupling agent KH560, 180 g of dicumyl peroxide, 300 g of polyethylene wax, 170 g of antioxidant BHT, and 120 g of light stabilizer 770.

[0045] The preparation method of the above-mentioned low-smoke and high-temperature resistant polyolefin sheath high-voltage cable for electric vehicle charging comprises the following steps:

[0046] S1. Add 1800 g of carbon black and graphene oxide to 7000 g of absolute ethanol, ultrasonically treat for 100 min, the ultrasonic frequency is 51 kHz, add 8 g of silane coupling agent KH560, stir at a temperature of 65 °C for 100 min, the stirring speed is 200 r / min, filter, wash with deionized water, and vacuum dry to obtain pretreated carbon black;

[0047] S2. Add carboxyl-terminated nitrile rubber to the pretreated carbon black, homogenize at a high speed at a temperature of 165 °C for 2 min, the homogenization speed is 9000 r / min, mix at a temperature of 85 °C for 100 min, send it into a high-speed kneader, add high-density polyethylene, linear low-density polyethylene, ethylene-vinyl acetate copolymer, antioxidant BHT, dicumyl peroxide, polyethylene wax, 800 g of carbon black, 170 g of silane coupling agent KH560, and light stabilizer 770, stir at a speed of 400 r / min for 28 min, and the kneading temperature is 85 °C to obtain a premix;

[0048] S3. Send the premix into a twin-screw extruder to extrude and coat it on the outer side of the cable core, and place it in a blast drying oven to dry at a temperature of 88 °C for 2.5 h;

[0049] Among them, the temperatures of each zone of the twin-screw extruder are: zone 1 is 135 °C, zone 2 is 146 °C, zone 3 is 168 °C, zone 4 is 178 °C, and the head is 188 °C.

[0050] Example 4

[0051] A low-smoke and high-temperature-resistant polyolefin sheath high-voltage cable for electric vehicle charging, comprising a cable core and a low-smoke and high-temperature-resistant polyolefin sheath layer coated on the outer side of the cable core; the raw materials of the low-smoke and high-temperature-resistant polyolefin sheath layer include: 11000 g of high-density polyethylene, 2000 g of linear low-density polyethylene, 2500 g of ethylene-vinyl acetate copolymer, 200 g of carboxyl-terminated nitrile rubber, 2400 g of carbon black, 250 g of graphene oxide, 132 g of silane coupling agent KH560, 120 g of dicumyl peroxide, 700 g of polyethylene wax, 130 g of antioxidant BHT, and 180 g of light stabilizer M535.

[0052] The preparation method of the above low-smoke and high-temperature-resistant polyolefin sheath high-voltage cable for electric vehicle charging comprises the following steps:

[0053] S1. Add 1200 g of carbon black and graphene oxide to 9000 g of absolute ethanol, ultrasonically treat for 80 min, the ultrasonic frequency is 57 kHz, add 2 g of silane coupling agent KH560, stir at a temperature of 75 °C for 80 min, the stirring speed is 400 r / min, filter, wash with deionized water, and vacuum dry to obtain pretreated carbon black.

[0054] S2. Add carboxyl-terminated nitrile rubber to the pretreated carbon black, perform high-speed homogenization at a temperature of 155 °C for 4 min, the homogenization speed is 7000 r / min, mix at a temperature of 90 °C for 80 min, send it into a high-speed kneader, add high-density polyethylene, linear low-density polyethylene, ethylene-vinyl acetate copolymer, antioxidant BHT, dicumyl peroxide, polyethylene wax, 1200 g of carbon black, 130 g of silane coupling agent KH560, and light stabilizer M535, stir at a speed of 500 r / min for 22 min, and the kneading temperature is 90 °C to obtain a premix.

[0055] S3. Send the premix into a twin-screw extruder to extrude and coat it on the outer side of the cable core, and place it in a blast drying oven to dry at a temperature of 82 °C for 3.5 h.

[0056] Among them, the temperatures of each zone of the twin-screw extruder are: zone 1 is 125 °C, zone 2 is 150 °C, zone 3 is 162 °C, zone 4 is 182 °C, and the head is 182 °C.

[0057] Example 5

[0058] A low-smoke and high-temperature-resistant polyolefin sheath high-voltage cable for electric vehicle charging, comprising a cable core and a low-smoke and high-temperature-resistant polyolefin sheath layer wrapped around the outside of the cable core; the raw materials of the low-smoke and high-temperature-resistant polyolefin sheath layer include: 10000 g of high-density polyethylene, 2500 g of linear low-density polyethylene, 2000 g of ethylene-vinyl acetate copolymer, 300 g of carboxyl-terminated nitrile rubber, 2500 g of carbon black, 200 g of graphene oxide, 155 g of silane coupling agent KH560, 150 g of dicumyl peroxide, 500 g of polyethylene wax, 150 g of antioxidant 1010, and 150 g of light stabilizer 944.

[0059] The preparation method of the above low-smoke and high-temperature-resistant polyolefin sheath high-voltage cable for electric vehicle charging comprises the following steps:

[0060] S1. Add 1500 g of carbon black and graphene oxide to 8000 g of absolute ethanol, ultrasonically treat for 90 min, the ultrasonic frequency is 54 kHz, add 5 g of silane coupling agent KH560, stir at 70 °C for 90 min, the stirring speed is 300 r / min, filter, wash with deionized water, vacuum dry, and pulverize to obtain pretreated carbon black;

[0061] S2. Add carboxyl-terminated nitrile rubber to the pretreated carbon black, homogenize at 160 °C for 3 min at a high speed, the homogenization speed is 8000 r / min, mix at 88 °C for 90 min, send it into a high-speed kneader, add high-density polyethylene, linear low-density polyethylene, ethylene-vinyl acetate copolymer, antioxidant 1010, dicumyl peroxide, polyethylene wax, 1000 g of carbon black, 150 g of silane coupling agent KH560, and light stabilizer 944, stir at a speed of 450 r / min for 25 min, and the kneading temperature is 88 °C to obtain a premix;

[0062] S3. Send the premix into a twin-screw extruder to extrude and coat it on the outside of the cable core, and place it in a blast drying oven to dry at 85 °C for 3 h;

[0063] Among them, the temperatures of each zone of the twin-screw extruder are: zone 1 is 130 °C, zone 2 is 148 °C, zone 3 is 165 °C, zone 4 is 180 °C, and the head is 185 °C.

[0064] Comparative Example 1

[0065] A low-smoke and high-temperature resistant polyolefin sheath high-voltage cable for electric vehicle charging, comprising a cable core and a low-smoke and high-temperature resistant polyolefin sheath layer coated on the outer side of the cable core; the raw materials of the low-smoke and high-temperature resistant polyolefin sheath layer include: 10000 g of high-density polyethylene, 2500 g of linear low-density polyethylene, 2000 g of ethylene-vinyl acetate copolymer, 300 g of carboxyl-terminated nitrile rubber, 2500 g of carbon black, 200 g of graphene oxide, 155 g of silane coupling agent KH560, 150 g of dicumyl peroxide, 500 g of polyethylene wax, 150 g of antioxidant 1010, and 150 g of light stabilizer 944.

[0066] The preparation method of the above-mentioned low-smoke and high-temperature resistant polyolefin sheath high-voltage cable for electric vehicle charging comprises the following steps:

[0067] S1. Add carboxyl-terminated nitrile rubber to the pretreated carbon black, homogenize at a high speed for 3 min at a temperature of 160 °C, with a homogenization speed of 8000 r / min, mix for 90 min at a temperature of 88 °C, feed it into a high-speed kneader, and add high-density polyethylene, linear low-density polyethylene, ethylene-vinyl acetate copolymer, antioxidant 1010, dicumyl peroxide, polyethylene wax, carbon black, graphene oxide, silane coupling agent KH560, and light stabilizer 944, and stir at a speed of 450 r / min for 25 min, with a kneading temperature of 88 °C, to obtain a premix;

[0068] S2. Feed the premix into a twin-screw extruder to extrude and coat it on the outer side of the cable core, and place it in a blast drying oven to dry for 3 h at a temperature of 85 °C;

[0069] Among them, the temperatures of each zone of the twin-screw extruder are: zone 1 at 130 °C, zone 2 at 148 °C, zone 3 at 165 °C, zone 4 at 180 °C, and the die head at 185 °C.

[0070] Comparative Example 2

[0071] A low-smoke and high-temperature resistant polyolefin sheath high-voltage cable for electric vehicle charging, comprising a cable core and a low-smoke and high-temperature resistant polyolefin sheath layer coated on the outer side of the cable core; the raw materials of the low-smoke and high-temperature resistant polyolefin sheath layer include: 10000 g of high-density polyethylene, 2500 g of linear low-density polyethylene, 2000 g of ethylene-vinyl acetate copolymer, 300 g of carboxyl-terminated nitrile rubber, 2500 g of carbon black, 200 g of graphene oxide, 155 g of silane coupling agent KH560, 150 g of dicumyl peroxide, 500 g of polyethylene wax, 150 g of antioxidant 1010, and 150 g of light stabilizer 944.

[0072] The preparation method of the above-mentioned low-smoke and high-temperature resistant polyolefin sheath high-voltage cable for electric vehicle charging comprises the following steps:

[0073] S1. Add 1500 g of carbon black and graphene oxide to 8000 g of absolute ethanol, ultrasonically treat for 90 min at an ultrasonic frequency of 54 kHz, add 5 g of silane coupling agent KH560, stir at 70 °C for 90 min at a stirring speed of 300 r / min, filter, wash with deionized water, and vacuum dry and crush to obtain pretreated carbon black;

[0074] S2. Feed the pretreated carbon black and carboxyl-terminated nitrile rubber into a high-speed kneader, add high-density polyethylene, linear low-density polyethylene, ethylene-vinyl acetate copolymer, antioxidant 1010, dicumyl peroxide, polyethylene wax, 1000 g of carbon black, 150 g of silane coupling agent KH560, and light stabilizer 944, stir at a speed of 450 r / min for 25 min, and the kneading temperature is 88 °C to obtain a premix;

[0075] S3. Feed the premix into a twin-screw extruder to extrude and coat it on the outside of the cable core, and place it in a blast drying oven to dry at 85 °C for 3 h;

[0076] Among them, the temperatures of each zone of the twin-screw extruder are: zone 1 at 130 °C, zone 2 at 148 °C, zone 3 at 165 °C, zone 4 at 180 °C, and the die head at 185 °C.

[0077] Peel off the polyolefin sheath layers of the high-voltage cables obtained in Example 5 and Comparative Examples 1-2, and measure the tensile strength with reference to GB / T 2951.11-2008 "General Test Methods for Insulating and Sheathing Materials of Cables and Optical Fibre Cables - Part 11: General Test Methods - Measurement of Thickness and Outer Dimensions - Mechanical Property Tests", and measure the impact strength with reference to GB / T 1843-2008 "Determination of Izod Impact Strength of Plastics".

[0078] As Figure 1 shown, the tensile strength and impact strength of the polyolefin sheath layer of the high-voltage cable obtained in Example 5 are the highest, superior to those of Comparative Examples 1-2 (P < 0.05).

[0079] Test the electromagnetic shielding effectiveness of the high-voltage cables obtained in Example 5 and Comparative Examples 1-2 in a wide frequency range of 4 - 18 GHz. Subsequently, heat-treat each group of specimens in an environment of 125 °C for 168 h, and test the electromagnetic shielding effectiveness retention rate again.

[0080] As Figure 2 shown, the electromagnetic shielding effectiveness of the high-voltage cable obtained in Example 5 is the highest, superior to those of Comparative Examples 1-2 (P < 0.05); its electromagnetic shielding effectiveness retention rate is still the highest after heat treatment at 125 °C for 168 h, superior to those of Comparative Examples 1-2 (P < 0.05).

[0081] The high-voltage cables obtained in Example 5 and Comparative Examples 1-2 were heat-treated in an environment of 125 °C for 168 h, and then the polyolefin sheath layer was peeled off, and the tensile strength retention rate and impact strength retention rate were tested again.

[0082] As Figure 3 shown, after the high-voltage cable obtained in Example 5 was heat-treated at 125 °C for 168 h, the tensile strength retention rate and impact strength retention rate of its polyolefin sheath layer were still the highest, better than those of Comparative Examples 1-2 (P < 0.05).

[0083] Refer to GB / T 2951.13-2008 "General test methods for insulating and sheathing materials of cables and optical cables - Part 13: General test methods - Methods for determination of density, water absorption test, shrinkage test" to determine the anti-shrinkage performance of the high-voltage cables obtained in Example 5 and Comparative Examples 1-2.

[0084] As Figure 4 shown, the shrinkage rates of the high-voltage cables obtained in Example 5 and Comparative Examples 1-2 were both low, and there was no significant difference (P > 0.05).

[0085] In view of the best shielding effect and the mechanical properties of the sheath layer of the high-voltage cable obtained in Example 5, refer to GB / T19666-2019 "General rules for flame-retardant and fire-resistant wires, cables and optical cables" to determine the bundle flame-retardant performance and low-smoke performance of the high-voltage cable obtained in Example 5. The high-voltage cable obtained in Example 5 meets the requirements of Class A flame retardancy and low smoke.

[0086] The applicant believes that: This is because the present invention uses the compounding of carbon black and graphene oxide, and combines an organic adsorption layer on its surface, which not only has high heat stability, but also effectively improves its dispersion in the matrix, has better interfacial compatibility, and the carboxyl group in the carboxyl-terminated nitrile rubber further reacts with the epoxy group to combine the nitrile copolymer chain segment in the organic layer. When subjected to external force impact, it can buffer through molecular chains, absorb and disperse stress, and improve the toughness of the polyethylene matrix; at the same time, under the action of the cross-linking agent, it can entangle with the polyethylene matrix to form a more stable network structure, significantly improving the high-temperature resistance of the polyethylene matrix and reducing the occurrence of fire accidents. The present invention uses polyethylene as the main component, and uses carboxyl-terminated nitrile rubber, ethylene-vinyl acetate copolymer and other auxiliary materials to compound and prepare the sheath layer, which not only makes the high-voltage cable have excellent impact resistance and high-temperature resistance at 125 °C, but also has a significant smoke suppression effect.

[0087] The above is only a preferred specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art within the technical scope disclosed by the present invention, according to the technical solution of the present invention and its inventive concept, makes equivalent substitutions or changes, and should be covered by the protection scope of the present invention.

Claims

1. A low-smoke, high-temperature-resistant polyolefin sheathed high-voltage cable for electric vehicle charging, characterized in that: It includes a cable core and a low-smoke, high-temperature-resistant polyolefin sheath layer coated on the outside of the cable core; The raw materials of the low-smoke and high-temperature resistant polyolefin sheath layer include, by mass: 80-120 parts of high-density polyethylene, 10-40 parts of linear low-density polyethylene, 10-30 parts of ethylene-vinyl acetate copolymer, 1-5 parts of terminal carboxyl nitrile rubber, 15-35 parts of carbon black, 1-3 parts of graphene oxide, 1.01-2.1 parts of silane coupling agent KH560, 1-2 parts of cross-linking agent, 2-8 parts of processing aid, 1-2 parts of antioxidant, and 1-2 parts of light stabilizer.

2. The low-smoke, high-temperature-resistant polyolefin sheathed high-voltage cable for electric vehicle charging according to claim 1 is characterized in that: The cross-linking agent is at least one of dicumyl peroxide, dibenzoyl peroxide and tert-butyl hydroperoxide.

3. The low-smoke, high-temperature-resistant polyolefin sheathed high-voltage cable for electric vehicle charging according to claim 1 is characterized in that: The processing aid is polyethylene wax and / or silicone powder.

4. The low-smoke, high-temperature-resistant polyolefin sheathed high-voltage cable for electric vehicle charging according to claim 1 is characterized in that: The antioxidant is at least one of antioxidant 1010, antioxidant BHT, antioxidant DNP and antioxidant TNP.

5. The low-smoke, high-temperature-resistant polyolefin sheathed high-voltage cable for electric vehicle charging according to claim 1, characterized in that: The light stabilizer is at least one of light stabilizer 119, light stabilizer 292, light stabilizer 770, light stabilizer 944, and light stabilizer M535.

6. A method for preparing a low-smoke, high-temperature-resistant polyolefin sheathed high-voltage cable for electric vehicle charging as claimed in any one of claims 1 to 5, characterized in that: The steps include: S1. Add carbon black and graphene oxide to anhydrous ethanol and ultrasonically treat for 1-2 hours, add silane coupling agent KH560, stir at 60-80° C. for 1-2 hours, filter, wash, dry, and crush to obtain pretreated carbon black; S2, add carboxyl-terminated nitrile rubber to the pretreated carbon black, homogenize at 150-170° C. for 1-5 min, mix at 80-95° C. for 1-2 h, add high-density polyethylene, linear low-density polyethylene, ethylene-vinyl acetate copolymer, antioxidant, crosslinking agent, processing aid, carbon black, silane coupling agent KH560, light stabilizer, knead at 80-95° C. for 20-30 min to obtain a premix; S3, extrude the premix and coat it on the outside of the cable core, and dry it.

7. The method for preparing the low-smoke, high-temperature-resistant polyolefin sheathed high-voltage cable for electric vehicle charging according to claim 6, characterized in that: In S1, the ultrasound frequency is 50-60kHz.

8. The method for preparing the low-smoke, high-temperature-resistant polyolefin sheathed high-voltage cable for electric vehicle charging according to claim 6, characterized in that: The mass ratio of carbon black used in S1 to carbon black used in S2 is 10-20:5-15.

9. The method for preparing the low-smoke, high-temperature-resistant polyolefin sheathed high-voltage cable for electric vehicle charging according to claim 6, characterized in that: The mass ratio of the silane coupling agent used in S1 to the silane coupling agent used in S2 is 0.01-0.1:1-2.

10. The method for preparing the low-smoke, high-temperature-resistant polyolefin sheathed high-voltage cable for electric vehicle charging according to claim 6, characterized in that: S3 uses a twin-screw extruder for extrusion, and the temperatures of the zones of the twin-screw extruder are: zone 1 120-140°C, zone 2 145-152°C, zone 3 160-170°C, zone 4 175-185°C, and die head 180-190°C.

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