Low-smoke halogen-free high-flame-retardant power cable and preparation method thereof

Abstract

The invention provides a low-smoke halogen-free high-flame-retardant power cable and a preparation method thereof, and the low-smoke halogen-free high-flame-retardant power cable comprises a conductor, an insulating layer and a sheath layer. The sheath layer is prepared from the following raw materials: 25 to 40 parts of ethylene-vinyl acetate copolymer, 15 to 25 parts of linear low-density polyethylene, 5 to 15 parts of metallocene polyethylene, 8 to 15 parts of reactive phosphorus-nitrogen-silicon hybrid compatibilizer, 12 to 22 parts of low-temperature sintered ceramic composite powder, 30 to 45 parts of surface-treated magnesium hydroxide, 15 to 25 parts of surface-treated aluminum hydroxide, 3 to 6 parts of organic modified montmorillonite and 1.5 to 2.5 parts of triallyl isocyanurate. 1.0 to 2.0 parts of a composite antioxidant, 1.0 to 2.5 parts of a calcium-zinc stabilizer and 0.5 to 1.5 parts of silicone master batch. The prepared low-smoke halogen-free high-flame-retardant power cable has excellent flexibility, mechanical property, heat resistance and processability, is stable in flame retardant property and stable in size, and is suitable for safety protection of power cables.

Description

Technical Field

[0001] This invention relates to the field of cable technology, specifically to a low-smoke, halogen-free, high flame-retardant power cable and its preparation method. Background Technology

[0002] Cross-linked polyethylene (XLPE) insulated power cables, with their excellent electrical insulation properties, mechanical strength, and heat resistance, have been widely used in urban power grids, rail transit, high-rise buildings, and other power transmission fields, becoming the mainstream cable product for medium and high voltage power transmission. To meet fire safety requirements in public places and densely populated areas, the outer sheath of these cables often uses low-smoke halogen-free flame-retardant materials to reduce smoke release and toxic gas hazards in fire scenarios, thereby improving the safety of line operation.

[0003] Currently, conventional low-smoke halogen-free flame-retardant sheath materials generally suffer from insufficient comprehensive performance of the matrix resin and poor compatibility of various components, making it difficult to balance flexibility, mechanical strength, processing fluidity, and low-temperature toughness. At the same time, the system exhibits weak charring effect, low interfacial bonding strength, and insufficient melt strength at high temperatures, making it difficult for the cable sheath to form a stable and dense protective structure during combustion. Flame-retardant efficiency, high-temperature structural stability, and dimensional stability all need to be improved, failing to meet the requirements of high-safety-level power cables for low smoke, halogen-free, high flame retardancy, and long-term reliability. Summary of the Invention

[0004] To address the problems existing in the prior art, this invention provides a low-smoke halogen-free high flame-retardant power cable and its preparation method.

[0005] To achieve the above objectives, the present invention provides the following technical solution: This invention discloses a low-smoke, halogen-free, high flame-retardant power cable, comprising a conductor, an insulation layer, and a sheath layer. By weight, the raw materials for preparing the sheath layer include: 25-40 parts of ethylene-vinyl acetate copolymer, 15-25 parts of linear low-density polyethylene, 5-15 parts of metallocene polyethylene, 8-15 parts of reactive phosphorus-nitrogen-silicon hybrid compatibilizer, 12-22 parts of low-temperature sintered ceramic composite powder, 30-45 parts of surface-treated magnesium hydroxide, 15-25 parts of surface-treated aluminum hydroxide, 3-6 parts of organically modified montmorillonite, 1.5-2.5 parts of triallyl isocyanurate, 1.0-2.0 parts of composite antioxidant, 1.0-2.5 parts of calcium-zinc stabilizer, and 0.5-1.5 parts of silicone masterbatch.

[0006] Preferably, the raw materials for preparing the reactive phosphorus-nitrogen-silicon hybrid compatibilizer, by weight, include: 95-105 parts of γ-glycidyl etheroxypropyltrimethoxysilane, 12-15 parts of deionized water, 0.5-0.8 parts of 0.06-0.1 mol / L hydrochloric acid solution, 20-30 parts of melamine, 80-100 parts of anhydrous ethanol, 15-25 parts of pentaerythritol phosphate, 1-2 parts of p-toluenesulfonic acid, and 0.5-1.0 parts of dibutyltin dilaurate.

[0007] Preferably, the preparation method of the reactive phosphorus-nitrogen-silicon hybrid compatibilizer includes the following steps: 1) Under nitrogen protection, γ-glycidoxypropyltrimethoxysilane, deionized water and hydrochloric acid solution were mixed and stirred at a speed of 150~250 r / min. The hydrolysis and condensation reaction was carried out at 25~30℃ for 4~6 h. The temperature was raised to 80~90℃ and the mixture was distilled under reduced pressure at -0.08~-0.1 MPa to remove small molecule byproducts, so as to obtain hyperbranched polysiloxane with terminal epoxy groups. 2) Disperse melamine in anhydrous ethanol, heat to 70-80℃, add pentaerythritol phosphate dropwise, and after the addition is complete, add p-toluenesulfonic acid. Reflux at 80-85℃ for 4-6 hours, cool to 20-30℃, filter, wash 2-3 times with anhydrous ethanol, and dry at 70-80℃ and a vacuum of -0.08 to -0.1 MPa for 6-8 hours to obtain the phosphorus-nitrogen modifier; 3) Add hyperbranched polysiloxane, phosphorus-nitrogen modifier and dibutyltin dilaurate into a mixer and react for 5-8 minutes at 150-160℃ and 60-80 r / min to obtain reactive phosphorus-nitrogen-silicon hybrid compatibilizer.

[0008] Preferably, the raw materials for preparing the low-temperature sintered ceramic composite powder, by weight, include: 40-50 parts of borosilicate glass powder, 20-30 parts of ammonium polyphosphate, 15-20 parts of wollastonite, 5-8 parts of nano zinc oxide, and 8-12 parts of zirconium phosphate.

[0009] Preferably, the preparation method of the low-temperature sintered ceramic composite powder is as follows: borosilicate glass powder, ammonium polyphosphate, wollastonite, nano zinc oxide and zirconium phosphate are placed in a planetary ball mill, anhydrous ethanol is used as the ball milling medium, the ball-to-material mass ratio is (3~5):1, and the mixture is ball-milled at a speed of 350~450 r / min for 5~7 h. The mixed slurry is vacuum dried at 80~90℃ and -0.08~-0.1 MPa for 10~14 h, and after pulverization, it is passed through a 280~325 mesh sieve to obtain the low-temperature sintered ceramic composite powder.

[0010] Preferably, the composite antioxidant is prepared by compounding antioxidant 1010 and antioxidant 168 in a mass ratio of 1:2.

[0011] This invention also discloses a method for preparing a low-smoke, halogen-free, high flame-retardant power cable, comprising the following steps: S1, Premixed Intensive Mixture: According to the formula, take ethylene-vinyl acetate copolymer, linear low-density polyethylene and metallocene polyethylene and put them into a mixer, and plasticize them for 3-5 minutes at 100~110℃ and 40~50r / min. Add reactive phosphorus-nitrogen-silicon hybrid compatibilizer, organic modified montmorillonite, composite antioxidant, and calcium-zinc stabilizer, and continue mixing at 110~120℃ for 3~5 minutes; Then add surface-treated magnesium hydroxide, surface-treated aluminum hydroxide, low-temperature sintered ceramic composite powder and silicone masterbatch, and mix at 120~130℃ for 5~8 minutes, controlling the discharge temperature at 130~140℃ to obtain the compounded rubber. S2, Extrusion granulation: The compounded rubber compound is fed into a twin-screw extruder, extruded and granulated, cooled, air-dried at room temperature and then granulated to obtain the base granules for the sheath layer; S3, crosslinking aid blending and homogenization: The sheath layer base granules are mixed with triallyl isocyanurate at 40-50°C for 2-4 minutes to obtain sheath granules containing crosslinking aids. S4. Cable forming: The sheathing granules containing crosslinking aids are extruded through a single screw extruder and coated onto the metal shielding layer of the cable core to form a sheathing layer. The formed cable is then placed under an electron accelerator with an irradiation dose of 80~120kGy for irradiation crosslinking to obtain a low-smoke halogen-free high flame-retardant power cable.

[0012] Preferably, in step S2, the temperatures of each section of the extruder are set as follows: Zone 1 130~140℃, Zone 2 140~150℃, Zone 3 150~160℃, Zone 4 155~165℃, and the die head 150~160℃, with a screw speed of 250~350 r / min; the extruded material is cooled by circulating water at 15~25℃.

[0013] Preferably, in step S4, the extruder temperature is set as follows: 140~150℃ for the feeding section, 150~160℃ for the compression section, 160~170℃ for the homogenization section, and 155~165℃ for the die head, with a sheath layer thickness of 1.2~2.0mm.

[0014] The beneficial effects of this invention are as follows: Ethylene-vinyl acetate copolymer, linear low-density polyethylene, and metallocene polyethylene are blended as matrix resins to give the sheathing material good flexibility, mechanical strength, heat resistance, processing fluidity, and low-temperature toughness. Reactive phosphorus-nitrogen-silicon hybrid compatibilizers improve the compatibility between components, enhance the interfacial bonding strength between fillers and matrix resins, and catalyze char formation. Low-temperature sintered ceramicized composite powders can form a dense ceramic phase under high-temperature conditions, improving the high-temperature structural stability of the sheathing layer. Surface-treated magnesium hydroxide and surface-treated aluminum hydroxide can endothermally decompose and release water vapor at high temperatures, diluting oxygen in the combustion environment and generating a refractory layer, thus providing flame retardancy. Organically modified montmorillonite can form a physical barrier layer, extending the gas and heat transfer path during combustion. Triallyl isocyanurate promotes the formation of a three-dimensional network structure in the sheathing material, improving the high-temperature melt strength and dimensional stability. Composite antioxidants and calcium-zinc stabilizers enhance the thermal stability of the sheathing material and slow down its thermal aging. Silicone masterbatch improves the processing performance of the sheathing material, making the components more uniformly mixed.

[0015] γ-glycidoxypropyltrimethoxysilane can serve as a skeletal raw material for reactive phosphorus-nitrogen-silicon hybrid compatibilizers. The trimethoxysilane group in its molecule can undergo hydrolysis-condensation reactions to form a hyperbranched structure, and the terminal epoxy groups can provide sites for subsequent grafting reactions. The combination of deionized water and 0.06–0.1 mol / L hydrochloric acid solution can promote the hydrolysis-condensation reaction of γ-glycidoxypropyltrimethoxysilane. The hydrochloric acid solution can adjust the pH of the reaction system to control the rate of the hydrolysis-condensation reaction. Melamine can serve as a nitrogen source; the amino groups in its molecule can react with pentaerythritol phosphorus... Nitrogen is introduced through the reaction of esters; anhydrous ethanol can be used as a solvent to disperse raw materials such as melamine, providing a uniform reaction environment; pentaerythritol phosphate can be used as a phosphorus source, and the active phosphate groups in its molecule can react with the amino groups of melamine to introduce phosphorus; p-toluenesulfonic acid can be used as a catalyst to accelerate the reaction process between melamine and pentaerythritol phosphate; dibutyltin dilaurate can be used as a catalyst to promote the ring-opening grafting reaction between the terminal epoxy groups of hyperbranched polysiloxanes and the amino groups in the phosphorus and nitrogen modifier, so that the reaction components can form a hybrid structure through chemical bonding.

[0016] Borosilicate glass powder can soften and melt at high temperatures to form a binder phase, binding other components together; ammonium polyphosphate can decompose at high temperatures to generate polyphosphoric acid, catalyzing the carbonization of the material and promoting the fusion of the carbon layer and the glass phase; wollastonite can serve as a reinforcing framework, improving the structural strength of the ceramic layer formed under high-temperature conditions; nano-zinc oxide can act as a catalyst, promoting the low-temperature eutectic reaction between the components and accelerating the ceramicization process; zirconium phosphate can serve as a reinforcing framework, working synergistically with wollastonite and participating in the formation of a Zr-O-Si bond network, improving the density and structural stability of the ceramic layer. Detailed Implementation

[0017] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0018] Example 1: This embodiment discloses a low-smoke, halogen-free, high-flame-retardant power cable, comprising a conductor, an insulation layer, and a sheath layer. By weight, the raw materials for preparing the sheath layer include: 25 parts ethylene-vinyl acetate copolymer, 15 parts linear low-density polyethylene, 5 parts metallocene polyethylene, 8 parts reactive phosphorus-nitrogen-silicon hybrid compatibilizer, 12 parts low-temperature sintered ceramic composite powder, 30 parts surface-treated magnesium hydroxide, 15 parts surface-treated aluminum hydroxide, 3 parts organically modified montmorillonite, 1.5 parts triallyl isocyanurate, 1 part composite antioxidant, 1 part calcium-zinc stabilizer, and 0.5 parts silicone masterbatch. The composite antioxidant is composed of antioxidant 1010 and antioxidant 168 compounded at a mass ratio of 1:2.

[0019] The raw materials for preparing the reactive phosphorus-nitrogen-silicon hybrid compatibilizer, by weight, include: 95 parts of γ-glycidyl etheroxypropyltrimethoxysilane, 12 parts of deionized water, 0.5 parts of 0.06 mol / L hydrochloric acid solution, 20 parts of melamine, 80 parts of anhydrous ethanol, 15 parts of pentaerythritol phosphate, 1 part of p-toluenesulfonic acid, and 0.5 parts of dibutyltin dilaurate.

[0020] The preparation method of reactive phosphorus-nitrogen-silicon hybrid compatibilizer includes the following steps: 1) Under nitrogen protection, γ-glycidoxypropyltrimethoxysilane, deionized water and hydrochloric acid solution were mixed and stirred at 150 r / min. The hydrolysis and condensation reaction was carried out at 25 °C for 4 h. The temperature was raised to 80 °C and the mixture was distilled under reduced pressure at -0.08 MPa to remove small molecule byproducts, so as to obtain hyperbranched polysiloxane with terminal epoxy groups. 2) Melamine was dispersed in anhydrous ethanol, heated to 70°C, and pentaerythritol phosphate was added dropwise. After the addition was complete, p-toluenesulfonic acid was added, and the mixture was refluxed at 80°C for 4 hours. After cooling to 20°C, the mixture was filtered, washed twice with anhydrous ethanol, and dried at 70°C and a vacuum of -0.08 MPa for 6 hours to obtain the phosphorus-nitrogen modifier. 3) Add hyperbranched polysiloxane, phosphorus-nitrogen modifier and dibutyltin dilaurate into a mixer and react for 5 min at 150℃ and 60 r / min to obtain a reactive phosphorus-nitrogen-silicon hybrid compatibilizer.

[0021] The raw materials for preparing the low-temperature sintered ceramic composite powder, by weight, include: 40 parts borosilicate glass powder, 20 parts ammonium polyphosphate, 15 parts wollastonite, 5 parts nano zinc oxide, and 8 parts zirconium phosphate.

[0022] The preparation method of low-temperature sintered ceramic composite powder is as follows: Borosilicate glass powder, ammonium polyphosphate, wollastonite, nano zinc oxide and zirconium phosphate are placed in a planetary ball mill, anhydrous ethanol is used as the ball milling medium, the ball-to-material mass ratio is 3:1, and the mixture is ball-milled at 350 r / min for 5 h. The mixture is then vacuum dried at 80℃ and -0.08 MPa for 10 h. After pulverization, it is passed through a 280 mesh sieve to obtain low-temperature sintered ceramic composite powder.

[0023] This embodiment also discloses a method for preparing a low-smoke halogen-free, high flame-retardant power cable, comprising the following steps: S1, Premixed Intensive Mixture: According to the formula, ethylene-vinyl acetate copolymer, linear low-density polyethylene, and metallocene polyethylene are put into a mixer and plasticized for 3 minutes at 100℃ and 40r / min. Add reactive phosphorus-nitrogen-silicon hybrid compatibilizer, organic modified montmorillonite, composite antioxidant, and calcium-zinc stabilizer, and continue mixing at 110℃ for 3 minutes; Then add surface-treated magnesium hydroxide, surface-treated aluminum hydroxide, low-temperature sintered ceramic composite powder and silicone masterbatch, mix at 120℃ for 5 minutes, control the discharge temperature at 130℃, and obtain the mixed rubber compound. S2, Extrusion granulation: The compounded rubber compound was fed into a twin-screw extruder for extrusion and granulation. The temperatures of each section of the extruder were set as follows: Zone 1 130℃, Zone 2 140℃, Zone 3 150℃, Zone 4 155℃, and Die Head 150℃. The screw speed was 250 r / min. The extruded material was cooled with 15℃ circulating water, air-dried at room temperature, and then pelletized to obtain the basic granules for the sheath layer. S3, crosslinking aid blending and homogenization: The sheath base granules were mixed with triallyl isocyanurate at 40°C for 2 min to obtain sheath granules containing crosslinking aids. S4. Cable forming: The sheathing granules containing crosslinking aids are extruded through a single-screw extruder to coat the metal shielding layer of the cable core, forming a sheathing layer. The extruder temperature is set as follows: feeding section 140℃, compression section 150℃, homogenization section 160℃, die head 155℃, and sheathing layer thickness 1.2mm. The formed cable is then placed under an electron accelerator with an irradiation dose of 80kGy for crosslinking to obtain a low-smoke halogen-free, high flame-retardant power cable.

[0024] Example 2: This embodiment discloses a low-smoke, halogen-free, high flame-retardant power cable, comprising a conductor, an insulation layer, and a sheath layer. By weight, the raw materials for preparing the sheath layer include: 40 parts ethylene-vinyl acetate copolymer, 25 parts linear low-density polyethylene, 15 parts metallocene polyethylene, 15 parts reactive phosphorus-nitrogen-silicon hybrid compatibilizer, 22 parts low-temperature sintered ceramicized composite powder, 45 parts surface-treated magnesium hydroxide, 25 parts surface-treated aluminum hydroxide, 6 parts organically modified montmorillonite, 2.5 parts triallyl isocyanurate, 2 parts composite antioxidant, 2.5 parts calcium-zinc stabilizer, and 1.5 parts silicone masterbatch. The composite antioxidant is composed of antioxidant 1010 and antioxidant 168 compounded at a mass ratio of 1:2.

[0025] The raw materials for preparing the reactive phosphorus-nitrogen-silicon hybrid compatibilizer, by weight, include: 105 parts of γ-glycidyl etheroxypropyltrimethoxysilane, 15 parts of deionized water, 0.8 parts of 0.1 mol / L hydrochloric acid solution, 30 parts of melamine, 100 parts of anhydrous ethanol, 25 parts of pentaerythritol phosphate, 2 parts of p-toluenesulfonic acid, and 1 part of dibutyltin dilaurate.

[0026] The preparation method of reactive phosphorus-nitrogen-silicon hybrid compatibilizer includes the following steps: 1) Under nitrogen protection, γ-glycidoxypropyltrimethoxysilane, deionized water and hydrochloric acid solution were mixed and stirred at 250 r / min. The hydrolysis and condensation reaction was carried out at 30 °C for 6 h. The temperature was raised to 90 °C and the mixture was distilled under reduced pressure at -0.1 MPa to remove small molecule byproducts, so as to obtain hyperbranched polysiloxane with terminal epoxy groups. 2) Melamine was dispersed in anhydrous ethanol, heated to 80°C, and pentaerythritol phosphate was added dropwise. After the addition was complete, p-toluenesulfonic acid was added, and the mixture was refluxed at 85°C for 6 hours. After cooling to 30°C, the mixture was filtered, washed three times with anhydrous ethanol, and dried at 80°C and a vacuum of -0.1 MPa for 8 hours to obtain the phosphorus-nitrogen modifier. 3) Hyperbranched polysiloxane, phosphorus-nitrogen modifier and dibutyltin dilaurate are added to a mixer and reacted at 160℃ and 80r / min for 8min to obtain a reactive phosphorus-nitrogen-silicon hybrid compatibilizer.

[0027] The raw materials for preparing the low-temperature sintered ceramic composite powder, by weight, include: 50 parts borosilicate glass powder, 30 parts ammonium polyphosphate, 20 parts wollastonite, 8 parts nano zinc oxide, and 12 parts zirconium phosphate.

[0028] The preparation method of low-temperature sintered ceramic composite powder is as follows: Borosilicate glass powder, ammonium polyphosphate, wollastonite, nano zinc oxide and zirconium phosphate are placed in a planetary ball mill, anhydrous ethanol is used as the ball milling medium, the ball-to-material mass ratio is 5:1, and the mixture is ball-milled at 450 r / min for 7 h. The mixture is then vacuum dried at 90℃ and -0.1 MPa for 14 h. After pulverization, it is passed through a 325 mesh sieve to obtain low-temperature sintered ceramic composite powder.

[0029] This embodiment also discloses a method for preparing a low-smoke halogen-free, high flame-retardant power cable, comprising the following steps: S1, Premixed Intensive Mixture: According to the formula, ethylene-vinyl acetate copolymer, linear low-density polyethylene, and metallocene polyethylene are put into a mixer and plasticized for 5 minutes at 110℃ and 50r / min. Add reactive phosphorus-nitrogen-silicon hybrid compatibilizer, organic modified montmorillonite, composite antioxidant, and calcium-zinc stabilizer, and continue mixing at 120℃ for 5 minutes; Then add surface-treated magnesium hydroxide, surface-treated aluminum hydroxide, low-temperature sintered ceramic composite powder and silicone masterbatch, mix at 130℃ for 8 minutes, control the discharge temperature at 140℃, and obtain the mixed rubber compound. S2, Extrusion granulation: The compounded rubber compound was fed into a twin-screw extruder for extrusion and granulation. The temperatures of each section of the extruder were set as follows: Zone 1 140℃, Zone 2 150℃, Zone 3 160℃, Zone 4 165℃, and Die Head 160℃. The screw speed was 350 r / min. The extruded material was cooled with 25℃ circulating water, air-dried at room temperature, and then pelletized to obtain the basic granules for the sheath layer. S3, crosslinking aid blending and homogenization: The sheath base granules were mixed with triallyl isocyanurate at 50°C for 4 min to obtain sheath granules containing crosslinking aids. S4. Cable forming: The sheathing granules containing crosslinking aids are extruded through a single-screw extruder to coat the metal shielding layer of the cable core, forming a sheathing layer. The extruder temperature is set as follows: 150℃ for the feeding section, 160℃ for the compression section, 170℃ for the homogenization section, and 165℃ for the die head. The sheathing layer thickness is 2.0mm. The formed cable is then placed under an electron accelerator with an irradiation dose of 120kGy for crosslinking to obtain a low-smoke, halogen-free, and highly flame-retardant power cable.

[0030] Example 3: This embodiment discloses a low-smoke, halogen-free, high flame-retardant power cable, comprising a conductor, an insulation layer, and a sheath layer. By weight, the raw materials for preparing the sheath layer include: 30 parts ethylene-vinyl acetate copolymer, 20 parts linear low-density polyethylene, 10 parts metallocene polyethylene, 11 parts reactive phosphorus-nitrogen-silicon hybrid compatibilizer, 17 parts low-temperature sintered ceramicized composite powder, 37 parts surface-treated magnesium hydroxide, 20 parts surface-treated aluminum hydroxide, 5 parts organically modified montmorillonite, 2 parts triallyl isocyanurate, 1.5 parts composite antioxidant, 1.8 parts calcium-zinc stabilizer, and 1 part silicone masterbatch. The composite antioxidant is composed of antioxidant 1010 and antioxidant 168 compounded at a mass ratio of 1:2.

[0031] The raw materials for preparing the reactive phosphorus-nitrogen-silicon hybrid compatibilizer, by weight, include: 100 parts of γ-glycidyl etheroxypropyltrimethoxysilane, 14 parts of deionized water, 0.7 parts of 0.08 mol / L hydrochloric acid solution, 25 parts of melamine, 90 parts of anhydrous ethanol, 20 parts of pentaerythritol phosphate, 1.5 parts of p-toluenesulfonic acid, and 0.8 parts of dibutyltin dilaurate.

[0032] The preparation method of reactive phosphorus-nitrogen-silicon hybrid compatibilizer includes the following steps: 1) Under nitrogen protection, γ-glycidoxypropyltrimethoxysilane, deionized water and hydrochloric acid solution were mixed and stirred at 200 r / min. The hydrolysis and condensation reaction was carried out at 28℃ for 5 h. The temperature was raised to 85℃ and the mixture was distilled under reduced pressure at -0.09 MPa to remove small molecule byproducts, so as to obtain hyperbranched polysiloxane with terminal epoxy groups. 2) Melamine was dispersed in anhydrous ethanol, heated to 75°C, and pentaerythritol phosphate was added dropwise. After the addition was complete, p-toluenesulfonic acid was added, and the mixture was refluxed at 82°C for 5 hours. After cooling to 25°C, the mixture was filtered, washed three times with anhydrous ethanol, and dried at 75°C and a vacuum of -0.09 MPa for 7 hours to obtain the phosphorus-nitrogen modifier. 3) Hyperbranched polysiloxane, phosphorus-nitrogen modifier and dibutyltin dilaurate are added to a mixer and reacted at 155℃ and 70r / min for 7min to obtain a reactive phosphorus-nitrogen-silicon hybrid compatibilizer.

[0033] The raw materials for preparing the low-temperature sintered ceramic composite powder, by weight, include: 45 parts borosilicate glass powder, 25 parts ammonium polyphosphate, 17 parts wollastonite, 7 parts nano zinc oxide, and 10 parts zirconium phosphate.

[0034] The preparation method of low-temperature sintered ceramic composite powder is as follows: Borosilicate glass powder, ammonium polyphosphate, wollastonite, nano zinc oxide and zirconium phosphate are placed in a planetary ball mill, anhydrous ethanol is used as the ball milling medium, the ball-to-material mass ratio is 4:1, and the mixture is ball-milled at 400 r / min for 6 h. The mixture is then vacuum dried at 85℃ and -0.09 MPa for 12 h. After pulverization, it is passed through a 300 mesh sieve to obtain low-temperature sintered ceramic composite powder.

[0035] This embodiment also discloses a method for preparing a low-smoke halogen-free, high flame-retardant power cable, comprising the following steps: S1, Premixed Intensive Mixture: According to the formula, ethylene-vinyl acetate copolymer, linear low-density polyethylene, and metallocene polyethylene are put into a mixer and plasticized at 105℃ and 45r / min for 4min. Add reactive phosphorus-nitrogen-silicon hybrid compatibilizer, organic modified montmorillonite, composite antioxidant, and calcium-zinc stabilizer, and continue mixing at 115℃ for 4 minutes; Then add surface-treated magnesium hydroxide, surface-treated aluminum hydroxide, low-temperature sintered ceramic composite powder and silicone masterbatch, mix at 125℃ for 7 minutes, control the discharge temperature at 135℃, and obtain the mixed rubber compound. S2, Extrusion granulation: The compounded rubber compound was fed into a twin-screw extruder for extrusion and granulation. The temperatures of each section of the extruder were set as follows: Zone 1 135℃, Zone 2 145℃, Zone 3 155℃, Zone 4 160℃, and Die Head 155℃. The screw speed was 300 r / min. The extruded material was cooled with 20℃ circulating water, air-dried at room temperature, and then pelletized to obtain the basic granules for the sheath layer. S3, crosslinking aid blending and homogenization: The sheath base granules were mixed with triallyl isocyanurate at 45°C for 3 minutes to obtain sheath granules containing crosslinking aids. S4. Cable forming: The sheathing granules containing crosslinking aids are extruded through a single-screw extruder to cover the metal shielding layer of the cable core, forming a sheathing layer. The extruder temperature is set as follows: feeding section 145℃, compression section 155℃, homogenization section 165℃, die head 160℃, and sheathing layer thickness 1.6mm. The formed cable is then placed under an electron accelerator with an irradiation dose of 100kGy for irradiation crosslinking to obtain a low-smoke halogen-free, high flame-retardant power cable.

[0036] Comparative Example 1: A low-smoke, halogen-free, high flame-retardant power cable and its preparation method are disclosed. The only difference between this cable and Example 3 is that the reactive phosphorus-nitrogen-silicon hybrid compatibilizer is not added, but replaced by an equal mass of maleic anhydride-grafted polyolefin elastomer (POE-g-MAH).

[0037] Comparative Example 2: A low-smoke, halogen-free, high flame-retardant power cable and its preparation method are disclosed. The only difference between this cable and Example 3 is that the low-temperature sintered ceramic composite powder is not added, but replaced with an equal mass of aluminum hydroxide.

[0038] Comparative Example 3: A low-smoke, halogen-free, high flame-retardant power cable and its preparation method are disclosed. The only difference between this cable and Example 3 is that the reactive phosphorus-nitrogen-silicon hybrid compatibilizer and the low-temperature sintered ceramic composite powder are not added, but are replaced by equal masses of POE-g-MAH and aluminum hydroxide, respectively.

[0039] Comparative Example 4: A low-smoke, halogen-free, high flame-retardant power cable and its preparation method are disclosed. The only difference between this cable and Example 3 is that the reactive phosphorus-nitrogen-silicon hybrid compatibilizer is replaced with a hyperbranched polysiloxane without grafted phosphorus-nitrogen modifier.

[0040] Comparative Example 5: A low-smoke, halogen-free, high flame-retardant power cable and its preparation method are disclosed. The only difference between this cable and Example 3 is that the low-temperature sintered ceramic composite powder is replaced with a single borosilicate glass powder.

[0041] Comparative Example 6: A low-smoke, halogen-free, high flame-retardant power cable and its preparation method are disclosed. The only difference between this cable and Example 3 is that no organically modified montmorillonite is added.

[0042] Comparative Example 7: A low-smoke, halogen-free, high flame-retardant power cable and its preparation method are disclosed, the only difference between this cable and Example 3 is that triallyl isocyanurate is not added.

[0043] The tensile strength, elongation at break, limiting oxygen index, smoke density rating, flame retardancy rating, peak heat release rate, high-temperature ceramization molding performance, thermal aging performance, volume resistivity, and moisture resistance of the cables obtained in Examples 1-3 and Comparative Examples 1-7 were tested. The testing methods and standards for each performance are as follows: 1. Tensile strength and elongation at break According to GB / T 1040.3-2006 "Determination of tensile properties of plastics - Part 3: Test conditions for films and sheets", the sheath material was made into dumbbell-shaped specimens, and the tensile strength and elongation at break were tested at a tensile rate of 250 mm / min.

[0044] 2. Limiting Oxygen Index The limiting oxygen index was tested according to GB / T 2406.2-2009, "Determination of oxygen index of plastics - Part 2: Room temperature test".

[0045] 3. Smoke density grade According to GB / T 8627-2007 "Test Method for Smoke Density of Building Materials under Combustion or Decomposition", the maximum smoke density was tested in the flaming mode.

[0046] 4. Flame retardant rating The flammability rating of the cable was tested according to GB 31247-2014, "Classification of Flammability of Cables and Optical Fibers".

[0047] 5. Peak heat release rate According to ISO 5660-1, "Test methods for heat release rate of building materials - Part 1: Cone calorimeter method", a cone calorimeter was used at a heat flux of 35 kW / m³. 2 Tested under the specified conditions.

[0048] 6. High-temperature ceramic forming performance The sample was placed in a muffle furnace and heated to 1000℃ at a rate of 20℃ / min, and held for 30 min. The residual carbon rate was calculated as: (mass after calcination / mass before calcination) × 100%. After calcination, the ceramic sheet was tested for bending strength according to GB / T 6569-2006, with a span of 30 mm.

[0049] 7. Thermal aging performance According to GB / T 2951.12-2008, "General Test Methods for Insulation and Sheath Materials of Cables and Optical Fibers", after aging in hot air at 135℃ for 168 hours, the tensile strength retention rate is calculated as: tensile strength after aging / tensile strength before aging × 100%.

[0050] 8. Volume resistivity Tested at 20℃ according to GB / T 1410-2006, "Test Methods for Volume Resistivity and Surface Resistivity of Solid Insulating Materials".

[0051] 9.Moisture resistance According to GB / T2423.3-2016 "Environmental Testing for Electrical and Electronic Products - Part 2: Test Methods - Cab: Constant Damp Heat Test", after being placed in an environment of 85℃ and 85% relative humidity for 1000 hours, the insulation resistance retention rate = insulation resistance after damp heat / insulation resistance before damp heat × 100%.

[0052] The results are shown in Tables 1 and 2.

[0053] Table 1. Test results of mechanical and electrical properties Group Tensile strength (MPa) Elongation at break (%) Tensile strength retention rate after aging (%) <![CDATA[Volume resistivity (×10 14 Ω·m)]]> Insulation resistance retention rate after moisture resistance (%) Example 1 17.8 305 92 2.6 86 Example 2 19.2 335 94 3.2 88 Example 3 21.5 360 97 3.9 91 Comparative Example 1 16.2 265 84 2.1 76 Comparative Example 2 17.8 275 86 2.4 78 Comparative Example 3 14.0 210 72 1.6 63 Comparative Example 4 16.8 280 86 2.3 78 Comparative Example 5 16.5 273 83 2.2 77 Comparative Example 6 18.6 305 88 2.7 81 Comparative Example 7 15.5 235 76 2.0 70 Table 2. Test results of flame retardant properties and high-temperature ceramic forming properties Group Oxygen index (%) Smoke density (SDR) <![CDATA[Peak heat release rate (kW / m 2 )]]> Flame retardant rating Carbon residue rate at 1000℃ (%) Flexural strength of ceramic layer (MPa) Example 1 39.5 125 195 B1 55 21.5 Example 2 42.0 110 175 B1 61 24.8 Example 3 44.5 95 155 B1 68 28.5 Comparative Example 1 35.2 160 250 B2 43 15.8 Comparative Example 2 37.8 145 230 B1 39 10.2 Comparative Example 3 30.8 205 345 B2 28 6.5 Comparative Example 4 36.5 150 240 B1 46 17.2 Comparative Example 5 34.8 165 260 B2 37 8.2 Comparative Example 6 41.2 113 178 B1 58 23.9 Comparative Example 7 34.2 175 275 B2 43 16.5 Using Example 3 as the control group, the performance differences and causes of Comparative Examples 1-7 are analyzed as follows: Comparative Example 1: Replacing the reactive phosphorus-nitrogen-silicon hybrid compatibilizer with POE-g-MAH resulted in a decrease in tensile strength from 21.5 MPa to 16.2 MPa (a decrease of 24.7%), elongation at break from 360% to 265% (a decrease of 26.4%), tensile strength retention after aging from 97% to 84% (a decrease of 13.4%), and volume resistivity from 3.9 × 10⁻⁶ MPa. 14 Ω·m decreased to 2.1×10 14 The insulation resistance after moisture resistance decreased from 91% to 76% (a decrease of 46.2%), and the insulation resistance retention rate after moisture resistance decreased from 91% to 76% (a decrease of 16.5%). Regarding flame retardant performance, the oxygen index decreased from 44.5% to 35.2% (a decrease of 20.9%), the smoke density increased from 95 to 160 (an increase of 68.4%), and the peak heat release rate decreased from 155 kW / m³. 2 Increased to 250kW / m 2 (Increase of 61.3%), flame retardant rating decreased from B1 to B2, char residue at 1000℃ decreased from 68% to 43% (decrease of 36.8%), and flexural strength of ceramic layer decreased from 28.5 MPa to 15.8 MPa (decrease of 44.6%). These data indicate that the absence of reactive phosphorus-nitrogen-silicon hybrid compatibilizers led to a degradation of the filler-matrix interface from chemical bonding to physical entanglement, significantly weakening interfacial bonding and reducing stress transfer efficiency. Consequently, mechanical and electrical insulation properties declined simultaneously. Simultaneously, the lack of a phosphorus-nitrogen synergistic char-forming structure drastically reduced catalytic char-forming efficiency, resulting in insufficient char layer density and an inability to effectively promote the fusion and sintering of the glass phase and residual char at high temperatures, leading to a significant deterioration in the strength of the ceramic protective layer.

[0054] Comparative Example 2: Replacing the low-temperature sintered ceramic composite powder with aluminum hydroxide resulted in a decrease in elongation at break from 360% to 275% (a decrease of 23.6%), an oxygen index from 44.5% to 37.8% (a decrease of 15.1%), an increase in smoke density from 95 to 145 (an increase of 52.6%), and a peak heat release rate from 155 kW / m³. 2 Increased to 230kW / m 2 (Increase of 48.4%), the char residue at 1000℃ decreased from 68% to 39% (decrease of 42.6%), and the flexural strength of the ceramic layer decreased from 28.5MPa to 10.2MPa (decrease of 64.2%). This comparative example shows that the lack of low-temperature sintered ceramic composite powder causes the material to lose glass phase bonding and silicate framework support at high temperatures. Although aluminum hydroxide decomposes and absorbs heat and provides some refractory residue, the lack of synergistic effect of ammonium polyphosphate catalytic char formation and low-temperature eutectic of borosilicate glass powder prevents the formation of a dense ceramic layer, resulting only in loose inorganic residue. Therefore, the char residue and ceramic strength decrease significantly. At the same time, due to the failure of the ceramic protection mechanism, the heat and flue gas release during combustion increase significantly.

[0055] Comparative Example 3: The tensile strength of the composite powder, which simultaneously lacked a reactive phosphorus-nitrogen-silicon hybrid compatibilizer and low-temperature sintering ceramicized powder, decreased from 21.5 MPa to 14.0 MPa (a decrease of 34.9%), the elongation at break decreased from 360% to 210% (a decrease of 41.7%), the tensile strength retention after aging decreased from 97% to 72% (a decrease of 25.8%), and the volume resistivity decreased from 3.9 × 10⁻⁶ MPa. 14 Ω·m decreased to 1.6 × 10 14 The insulation resistance after moisture resistance decreased from 91% to 63% (a decrease of 30.8%), while the flame retardant and high-temperature ceramic forming properties showed comprehensive deterioration: the oxygen index decreased from 44.5% to 30.8% (a decrease of 30.8%), the smoke density increased from 95 to 205 (an increase of 115.8%), and the peak heat release rate decreased from 155 kW / m³. 2 Increased to 345kW / m 2 (Increase of 122.6%), flame retardant rating decreased to B2, char residue at 1000℃ decreased from 68% to 28% (decrease of 58.8%), and ceramic layer flexural strength decreased from 28.5MPa to 6.5MPa (decrease of 77.2%). This comparative example confirms that the lack of synergy between the two innovative components leads to the loss of the synergistic effect of interface compatibilization, catalytic char formation, and ceramic sintering. At high temperatures, the material lacks both dense char layer protection and high-strength ceramic skeleton support, resulting in severe dripping during combustion. The overall performance is significantly lower than when only one component is missing, confirming the irreplaceable nature of the reactive compatibilization-char formation catalysis-ceramic sintering three-dimensional synergistic system constructed in this invention.

[0056] Comparative Example 4: When hyperbranched polysiloxane without grafted phosphorus-nitrogen modifier was used to replace the reactive phosphorus-nitrogen-silicon hybrid compatibilizer, the tensile strength decreased from 21.5 MPa to 16.8 MPa (a decrease of 21.9%), the oxygen index decreased from 44.5% to 36.5% (a decrease of 18.0%), the smoke density increased from 95 to 150 (an increase of 57.9%), and the peak heat release rate increased from 155 kW / m³. 2 Increased to 240kW / m 2 (Increase of 54.8%), the char residue at 1000℃ decreased from 68% to 46% (decrease of 32.4%), and the flexural strength of the ceramic layer decreased from 28.5 MPa to 17.2 MPa (decrease of 39.6%). These results indicate that while hyperbranched polysiloxanes can provide interfacial compatibilization, they lack a phosphorus-nitrogen synergistic char-forming structure, failing to form a stable phosphorus-nitrogen char layer during combustion. This significantly reduces catalytic char formation efficiency, resulting in a loose high-temperature char residue structure and deteriorated wetting and sintering effect with the glass phase. Consequently, the strength and flame retardant properties of the ceramic layer decrease simultaneously. This demonstrates that the chemical grafting of phosphorus-nitrogen modifiers and hyperbranched polysiloxanes is crucial for achieving synergistic char-ceramization.

[0057] Comparative Example 5: Replacing the low-temperature sintered ceramic composite powder with a single borosilicate glass powder resulted in a decrease in the oxygen index from 44.5% to 34.8% (a decrease of 21.8%), an increase in smoke density from 95 to 165 (an increase of 73.7%), and a peak heat release rate from 155 kW / m³. 2 Increased to 260kW / m 2 (Increase of 67.7%), flame retardant rating decreased to B2, char residue at 1000℃ decreased from 68% to 37% (decrease of 45.6%), and flexural strength of ceramic layer decreased from 28.5MPa to 8.2MPa (decrease of 71.2%). This comparative example shows that although single glass powder can melt at high temperatures, it lacks the catalytic carbonization of ammonium polyphosphate, the reinforcement of the wollastonite framework, and the low-temperature eutectic catalytic system of zirconium phosphate-nano zinc oxide. Therefore, it cannot form an organic-inorganic composite carbon layer and a Zr-O-Si bonded network. The density and strength of the ceramic layer are severely insufficient, and the char residue is significantly reduced. This proves that the precise formulation of multiple components in low-temperature sintered ceramic composite powder is a necessary condition for achieving high-temperature self-supporting protection.

[0058] Comparative Example 6: Without the addition of organically modified montmorillonite, the smoke density increased from 95 to 113 (an increase of 18.9%), and the peak heat release rate increased from 155 kW / m³. 2 Increased to 178kW / m 2 (Increase of 14.8%), the char residue at 1000℃ decreased from 68% to 58% (decrease of 14.7%), and the flexural strength of the ceramic layer decreased from 28.5 MPa to 23.9 MPa (decrease of 16.1%). These results indicate that the absence of organically modified montmorillonite eliminates the physical barrier effect of the nanosheets, shortens the gas and heat diffusion path during combustion, and increases flue gas release. Simultaneously, the nanosheets lose their role as a carrier for the ceramicization reaction, leading to a decrease in the structural stability of the high-temperature char residue and a corresponding reduction in the strength of the ceramic layer.

[0059] Comparative Example 7: Without the addition of triallyl isocyanurate, tensile strength decreased from 21.5 MPa to 15.5 MPa (a decrease of 27.9%), elongation at break decreased from 360% to 235% (a decrease of 34.7%), tensile strength retention after aging decreased from 97% to 76% (a decrease of 21.6%), insulation resistance retention after moisture resistance decreased from 91% to 70% (a decrease of 23.1%), oxygen index decreased from 44.5% to 34.2% (a decrease of 23.1%), smoke density increased from 95 to 175 (an increase of 84.2%), and peak heat release rate decreased from 155 kW / m³. 2 Increased to 275kW / m 2(Increase of 77.4%), flame retardant rating decreased to B2, char residue at 1000℃ decreased from 68% to 43% (decrease of 36.8%), and flexural strength of ceramic layer decreased from 28.5 MPa to 16.5 MPa (decrease of 42.1%). These results indicate that the absence of crosslinking aids significantly reduced the irradiation crosslinking density, resulting in insufficient high-temperature melt strength and a tendency for melting and dripping during combustion, making it impossible to maintain a stable char layer structure. Simultaneously, the lack of a three-dimensional network structure led to decreased filler dispersion stability, reduced interfacial bonding strength, and overall deterioration of mechanical and flame retardant properties.

[0060] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A low-smoke, halogen-free, high flame-retardant power cable, comprising a conductor, an insulation layer, and a sheath layer, characterized in that, The raw materials for preparing the sheath layer, by weight, include: 25-40 parts of ethylene-vinyl acetate copolymer, 15-25 parts of linear low-density polyethylene, 5-15 parts of metallocene polyethylene, 8-15 parts of reactive phosphorus-nitrogen-silicon hybrid compatibilizer, 12-22 parts of low-temperature sintered ceramic composite powder, 30-45 parts of surface-treated magnesium hydroxide, 15-25 parts of surface-treated aluminum hydroxide, 3-6 parts of organically modified montmorillonite, 1.5-2.5 parts of triallyl isocyanurate, 1.0-2.0 parts of composite antioxidant, 1.0-2.5 parts of calcium-zinc stabilizer, and 0.5-1.5 parts of silicone masterbatch.

2. The low-smoke halogen-free high flame-retardant power cable according to claim 1, characterized in that, The raw materials for preparing the reactive phosphorus-nitrogen-silicon hybrid compatibilizer, by weight, include: 95-105 parts of γ-glycidyl etheroxypropyltrimethoxysilane, 12-15 parts of deionized water, 0.5-0.8 parts of 0.06-0.1 mol / L hydrochloric acid solution, 20-30 parts of melamine, 80-100 parts of anhydrous ethanol, 15-25 parts of pentaerythritol phosphate, 1-2 parts of p-toluenesulfonic acid, and 0.5-1.0 parts of dibutyltin dilaurate.

3. The low-smoke halogen-free high flame-retardant power cable according to claim 2, characterized in that, The preparation method of the reactive phosphorus-nitrogen-silicon hybrid compatibilizer includes the following steps: 1) Under nitrogen protection, γ-glycidoxypropyltrimethoxysilane, deionized water and hydrochloric acid solution were mixed and stirred at a speed of 150~250 r / min. The hydrolysis and condensation reaction was carried out at 25~30℃ for 4~6 h. The temperature was raised to 80~90℃ and the mixture was distilled under reduced pressure at -0.08~-0.1 MPa to remove small molecule byproducts, so as to obtain hyperbranched polysiloxane with terminal epoxy groups. 2) Disperse melamine in anhydrous ethanol, heat to 70-80℃, add pentaerythritol phosphate dropwise, and after the addition is complete, add p-toluenesulfonic acid. Reflux at 80-85℃ for 4-6 hours, cool to 20-30℃, filter, wash 2-3 times with anhydrous ethanol, and dry at 70-80℃ and a vacuum of -0.08 to -0.1 MPa for 6-8 hours to obtain the phosphorus-nitrogen modifier; 3) Add hyperbranched polysiloxane, phosphorus-nitrogen modifier and dibutyltin dilaurate into a mixer and react for 5-8 minutes at 150-160℃ and 60-80 r / min to obtain reactive phosphorus-nitrogen-silicon hybrid compatibilizer.

4. The low-smoke halogen-free high flame-retardant power cable according to claim 1, characterized in that, The raw materials for preparing the low-temperature sintered ceramic composite powder, by weight, include: 40-50 parts of borosilicate glass powder, 20-30 parts of ammonium polyphosphate, 15-20 parts of wollastonite, 5-8 parts of nano zinc oxide, and 8-12 parts of zirconium phosphate.

5. The low-smoke halogen-free high flame-retardant power cable according to claim 4, characterized in that, The preparation method of the low-temperature sintered ceramic composite powder is as follows: Borosilicate glass powder, ammonium polyphosphate, wollastonite, nano zinc oxide and zirconium phosphate are placed in a planetary ball mill, anhydrous ethanol is used as the ball milling medium, the ball-to-material mass ratio is (3~5):1, and the mixture is ball-milled at a speed of 350~450 r / min for 5~7 h. The mixed slurry is vacuum dried at 80~90℃ and -0.08~-0.1 MPa for 10~14 h. After pulverization, it is passed through a 280~325 mesh sieve to obtain the low-temperature sintered ceramic composite powder.

6. The low-smoke halogen-free high flame-retardant power cable according to claim 1, characterized in that, The composite antioxidant is composed of antioxidant 1010 and antioxidant 168 in a mass ratio of 1:

2.

7. A method for preparing a low-smoke halogen-free, high flame-retardant power cable according to any one of claims 1-6, characterized in that, Includes the following steps: S1, Premixed Intensive Mixture: According to the formula, ethylene-vinyl acetate copolymer, linear low-density polyethylene, and metallocene polyethylene are put into a mixer and plasticized for 3-5 minutes at 100-110℃ and 40-50r / min. Add reactive phosphorus-nitrogen-silicon hybrid compatibilizer, organic modified montmorillonite, composite antioxidant, and calcium-zinc stabilizer, and continue mixing at 110~120℃ for 3~5 minutes; Then add surface-treated magnesium hydroxide, surface-treated aluminum hydroxide, low-temperature sintered ceramic composite powder and silicone masterbatch, and mix at 120~130℃ for 5~8 minutes, controlling the discharge temperature at 130~140℃ to obtain the compounded rubber. S2, Extrusion granulation: The compounded rubber compound is fed into a twin-screw extruder, extruded and granulated, cooled, air-dried at room temperature and then granulated to obtain the base granules for the sheath layer; S3, crosslinking aid blending and homogenization: The sheath layer base granules are mixed with triallyl isocyanurate at 40-50°C for 2-4 minutes to obtain sheath granules containing crosslinking aids. S4. Cable forming: The sheathing granules containing crosslinking aids are extruded through a single screw extruder and coated onto the metal shielding layer of the cable core to form a sheathing layer. The formed cable is then placed under an electron accelerator with an irradiation dose of 80~120kGy for irradiation crosslinking to obtain a low-smoke halogen-free high flame-retardant power cable.

8. The method for preparing a low-smoke halogen-free, high flame-retardant power cable according to claim 7, characterized in that, In step S2, the temperatures of each section of the extruder are set as follows: Zone 1 130~140℃, Zone 2 140~150℃, Zone 3 150~160℃, Zone 4 155~165℃, and the die head 150~160℃; the screw speed is 250~350 r / min; the extruded material is cooled by circulating water at 15~25℃.

9. The method for preparing a low-smoke halogen-free, high flame-retardant power cable according to claim 7, characterized in that, In step S4, the extruder temperature is set as follows: feeding section 140~150℃, compression section 150~160℃, homogenization section 160~170℃, die head 155~165℃, and sheath layer thickness 1.2~2.0mm.