A halogen-free flame-retardant cable resistant to cracking and a method for manufacturing the same

Abstract

The application discloses a kind of anti-cracking halogen-free flame-retardant cable and preparation method thereof, it is related to crosslinked polyethylene power cable field, the insulating layer of the cable is by high-density polyethylene, low-density polyethylene, fumed silica, crosslinking modifier, zinc borate, lubricant and antioxidant after blending is coated on the surface of copper conductor, is prepared by irradiation crosslinking solidification, the crosslinking modifier is that after amino protection to 4-bromo-1,3,5-triazine-2-amine borate esterification reaction with boronic acid pinacol is obtained boron-containing flame-retardant precursor, then amino deprotection is obtained boron-containing flame-retardant monomer, then boron-containing flame-retardant monomer and phosphorus pentachloride occur phosphorus imidization reaction and are obtained phosphorus-containing flame-retardant intermediate, finally it is made by nucleophilic substitution reaction with 3,6,9,12-tetraoxotetradecan-13-en-1-al.

Description

Technical Field

[0001] This invention relates to the field of cross-linked polyethylene power cable technology, specifically to a crack-resistant halogen-free flame-retardant cable and its preparation method. Background Technology

[0002] Cross-linked polyethylene (XLPE) has become the preferred material for insulation layers of medium and high voltage power cables due to its excellent electrical insulation properties, heat resistance, aging resistance, and high mechanical strength. However, with increasingly stringent safety standards and environmental protection and fire prevention requirements for urban power grids, power cables not only need to possess long-term stable insulation characteristics, but also need to be halogen-free and flame-retardant in the event of a fire to avoid releasing large amounts of toxic hydrogen halide gas during combustion, thereby ensuring the safety of personnel evacuation and reducing secondary pollution to the environment.

[0003] To impart halogen-free flame-retardant properties to cross-linked polyethylene (XLPE) insulation, the mainstream technique in the industry is to add large amounts of inorganic metal flame-retardant fillers such as aluminum hydroxide or magnesium hydroxide to the base resin. However, due to the inherently low flame-retardant efficiency of these inorganic fillers, their addition levels in the formulation are typically consistently high. This high-filler physical blending method, however, can lead to a series of serious structural problems. The highly polar inorganic rigid particles have extremely poor interfacial compatibility with the weakly polar polyethylene matrix, easily forming a "sea-island" structure at the microscopic level, resulting in interface defects. Simultaneously, the high content of rigid particles significantly restricts the microscopic movement freedom of the cross-linked polyethylene network molecular chains, causing the insulation layer to become macroscopically hard and brittle. In practical applications, cables must withstand frequent thermal expansion and contraction caused by seasonal temperature differences during long-term operation, as well as unavoidable bending stress during installation. This embrittlement defect caused by high filler content easily induces stress concentration at the interface, leading to microcracks that gradually expand into through-cracks, seriously threatening the safe operation of the cable within its design life.

[0004] To alleviate the difficulties in processing and flow, as well as the embrittlement of materials in high-filler systems, conventional industrial practices involve adding small-molecule silane coupling agents, titanate coupling agents, or small-molecule plasticizers to coat and modify the surface of inorganic fillers. While small-molecule additives can significantly improve filler dispersibility and melt processing flowability in the short term, their fatal flaw lies in their extremely low molecular weight, resulting in high volatility and migration tendency. When cables operate under prolonged high-temperature conditions, these small-molecule additives overcome the constraints of the cross-linked network and gradually migrate and leak to the insulation surface or conductor interface. This process not only causes the material to become brittle again due to plasticizer loss, but also exacerbates the risk of cracking.

[0005] In summary, the current field of halogen-free flame-retardant cross-linked polyethylene cable technology has long faced the technical challenge of simultaneously achieving high flame retardancy and crack resistance, as well as the migration of small molecule additives. Therefore, this invention provides a crack-resistant halogen-free flame-retardant cable and its preparation method. Summary of the Invention

[0006] To address the shortcomings mentioned in the background section, the present invention aims to provide a crack-resistant halogen-free flame-retardant cable and its preparation method. The crosslinking modifier combines a triazine ring, borate ester, phosphorus element, and alkenyl polyether structure. The flexible polyether in the crosslinking modifier of this invention relieves stress and prevents cracking, while double-bonded polyethylene prevents additive migration. Phosphorus, nitrogen, and boron synergistically form carbon to achieve halogen-free flame retardancy, and the rigid ring improves heat aging resistance, thus solving the problems of easy cracking and performance imbalance in flame-retardant cables.

[0007] The objective of this invention can be achieved through the following technical solutions: A crack-resistant, halogen-free flame-retardant cable, comprising the following steps: The first step involves blending high-density polyethylene, low-density polyethylene, fumed silica, crosslinking modifier, zinc borate, lubricant, and antioxidant, then melt-extruding the mixture and coating it onto the surface of a copper conductor. This process is followed by irradiation crosslinking and curing to form an insulating layer, resulting in an insulated wire core. The second step is to twist the insulated wire cores together and fill the gaps with filler material to form a filler layer; The third step is to wrap the inner lining material around the filling layer to form the inner lining layer. Step 4: Weave armored metal wires on the outside of the inner lining layer with a weaving density of ≥90% to form an armored layer; Step 5: Extrude the sheath material over the armor layer to form a protective layer, thus obtaining a crack-resistant halogen-free flame-retardant cable; The crosslinking modifier is prepared by amino-protecting 4-bromo-1,3,5-triazine-2-amine and then reacting it with pinacol diboronate to obtain a boron-containing flame retardant precursor, followed by amino deprotection to obtain a boron-containing flame retardant monomer, then reacting the boron-containing flame retardant monomer with phosphorus pentachloride to obtain a phosphorus-containing flame retardant intermediate, and finally reacting it with 3,6,9,12-tetraoxotetradec-13en-1-ol for nucleophilic substitution.

[0008] More preferably, the lubricant in the first step is any one of polyethylene wax, oxidized polyethylene wax, or zinc stearate.

[0009] More preferably, the antioxidant in the first step is either antioxidant 1076 or antioxidant 1010.

[0010] More preferably, the mass ratio of high-density polyethylene, low-density polyethylene, fumed silica, crosslinking modifier, zinc borate, lubricant and antioxidant in the first step is 60~70:30~40:1~3:3~5:5~8:2~3:0.3~0.5.

[0011] More preferably, the filling material in the second step is any one of glass fiber filaments, aramid filaments, cotton thread, or non-woven fabric.

[0012] More preferably, the inner lining material in the third step is either polyethylene or nonwoven fabric.

[0013] More preferably, the armor wire in the fourth step is any one of galvanized steel wire, stainless steel wire, copper wire, and aluminum alloy wire.

[0014] More preferably, the sheath material in the fifth step is either high-density polyethylene or polyurethane.

[0015] More preferably, the method for preparing the crosslinking modifier includes the following steps: S1. Take 4-bromo-1,3,5-triazine-2-amine and dichloromethane into a reactor, and add triethylamine and 4-dimethylaminopyridine to it in sequence. Under ice-water bath conditions, slowly add ditert-butyl dicarbonate. After the addition is complete, restore the temperature to room temperature and stir the reaction for 1-2 hours to obtain a nitrogen-containing flame retardant monomer. S2. Under a nitrogen atmosphere, nitrogen-containing flame retardant monomer, pinacol diborate, potassium acetate, tetra(triphenylphosphine)palladium and 1,4-dioxane are sequentially added to the reactor and refluxed at 100~110℃ for 18~24h to obtain a boron-containing flame retardant precursor. S3. Add the boron-containing flame retardant precursor and dichloromethane to the reactor, and slowly add trifluoroacetic acid dropwise while stirring at room temperature. After the addition is complete, concentrate the mixture by rotary evaporation under reduced pressure, and adjust the pH of the system to 7-8 with saturated sodium bicarbonate aqueous solution to obtain the boron-containing flame retardant monomer. S4. Add boron-containing flame retardant monomer, phosphorus pentachloride, triethylamine and chlorobenzene to the reactor, heat to 100~110℃, react for 3~4h to obtain phosphorus-containing flame retardant intermediate; S5. Add phosphorus-containing flame retardant intermediate, 3,6,9,12-tetraoxotetradec-13en-1-ol, magnesium chloride, triethylamine and tetrahydrofuran into a reactor, and reflux at 66~68℃ for 16~18h to obtain crosslinking modifier.

[0016] More preferably, the molar ratio of 4-bromo-1,3,5-triazine-2-amine, triethylamine, 4-dimethylaminopyridine and ditert-butyl dicarbonate in step S1 is 1:2.0~2.5:0.1~0.3:1~1.2.

[0017] More preferably, the molar ratio of the nitrogen-containing flame retardant monomer, pinacol diborate, potassium acetate and tetrakis(triphenylphosphine)palladium in step S2 is 1:1~1.2:2.5~3:0.03~0.05.

[0018] More preferably, the molar ratio of the boron-containing flame-retardant precursor to trifluoroacetic acid in step S3 is 1:10~15.

[0019] More preferably, the molar ratio of boron-containing monomer, phosphorus pentachloride and triethylamine in step S4 is 1:1~1.2:3~3.3.

[0020] More preferably, the molar ratio of the phosphorus-containing flame-retardant intermediate, 3,6,9,12-tetraoxotetradec-13en-1-ol, magnesium chloride and triethylamine in step S5 is 1:3.3~3.5:0.1~0.3:3.0~3.5.

[0021] The beneficial effects of this invention are: The long, flexible ether segments of the crosslinking modifier in this invention effectively dissipate internal stress caused by temperature changes or external bending through the thermal motion of molecular segments in the crosslinking network, preventing stress concentration at rigid crosslinking nodes. Simultaneously, the active double bonds at both ends are grafted onto the main chain of the crosslinked polyethylene, avoiding long-term failure caused by the migration of free plasticizers. This allows the insulating layer to maintain a high degree of crosslinking while achieving excellent elongation at break and resistance to thermal shock.

[0022] This invention utilizes phosphorus, nitrogen, and boron elements within the crosslinking modifier molecule to form a highly efficient char-forming synergistic system. During combustion, the ether chain provides the carbon source, phosphorus promotes the dehydration and char formation of the matrix and releases phosphorus-containing free radicals into the gas phase, capturing high-energy free radicals in the combustion chain reaction and severing the combustion chain from the gas phase. The triazine nitrogen heterocycle releases non-flammable gas, which forms bubbles inside the char layer, driving the char layer to expand and form a thick and highly porous heat-insulating char layer. The pinacol borate ester structure transforms into a glassy substance at high temperatures, solidifying the originally loose porous char layer into a dense and tough ceramic physical barrier, blocking the inward penetration of oxygen and heat. This multi-layered flame-retardant mechanism of phosphorus-promoted char, nitrogen-foaming, and boron-enhanced allows the material to form a dense heat-insulating layer even with low addition amounts, effectively inhibiting flame spread and molten dripping, achieving excellent halogen-free flame-retardant effects.

[0023] Furthermore, the conjugated rigid skeleton of the rigid nitrogen heterocycle in the crosslinking modifier molecule, connected to pinacol borate ester, significantly improves the overall thermal stability of the molecule. During combustion, it acts as a rigid node in the expanded char layer, significantly enhancing the mechanical strength and resistance to hot air erosion of the expanded char layer, preventing large-area collapse and cracking of the char layer under continuous impact from high-temperature flames. At the same time, the presence of this rigid unit makes it difficult for the modifier's molecular chain to break or rearrange during long-term high-temperature operation of the cable, effectively inhibiting the degradation of flame retardants caused by long-term thermal aging, thereby ensuring the long-term flame retardant stability and electrical reliability of the cable insulation layer throughout its entire life cycle. Detailed Implementation

[0024] The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0025] The CAS number of 3,6,9,12-tetraoxotetradec-13en-1-ol used in the following examples and comparative examples is 7287-58-3.

[0026] Example 1: A method for preparing a crosslinking modifier, comprising the following steps: S1. Take 11.2g of 4-bromo-1,3,5-triazine-2-amine and 120mL of dichloromethane into a reactor, and add 16g of triethylamine and 1.5g of 4-dimethylaminopyridine to it in sequence. Under ice-water bath conditions, slowly add 14mL of ditert-butyl dicarbonate. After the addition is complete, return to room temperature and stir the reaction for 2h. After the reaction is completed, quench with water, then extract with dichloromethane, wash with saturated brine, dry with anhydrous sodium sulfate, filter and concentrate under reduced pressure to obtain nitrogen-containing flame retardant monomer. S2. Under a nitrogen atmosphere, 10.5 g of nitrogen-containing flame retardant monomer, 10.7 g of pinacol diborate, 10.4 g of potassium acetate, 1.12 g of tetrakis(triphenylphosphine)palladium and 100 mL of 1,4-dioxane were added sequentially to the reactor and refluxed at 110 °C for 24 h. After the reaction was completed, the reaction solution was extracted with ethyl acetate, dried with anhydrous sodium sulfate, and then filtered, concentrated and eluted by column chromatography to obtain the boron-containing flame retardant precursor. S3. Add 7.5g of boron-containing flame retardant precursor and 30mL of dichloromethane to the reactor. Slowly add 22mL of trifluoroacetic acid dropwise while stirring at room temperature. After the addition is complete, concentrate the mixture by rotary evaporation under reduced pressure. Adjust the pH of the system to 8 with saturated sodium bicarbonate aqueous solution. Extract with ethyl acetate and retain the organic phase. Wash the organic phase with saturated brine, dry it with anhydrous sodium sulfate, filter it, and finally concentrate it under reduced pressure to obtain the boron-containing flame retardant monomer. S4. Add 3.1g of boron-containing flame retardant monomer, 3.2g of phosphorus pentachloride, 5.8mL of triethylamine and 40mL of chlorobenzene to the reactor, heat to 110℃, react for 4h, cool to room temperature after the reaction is completed, filter and wash the filter cake with dry n-hexane, then place the solid in a vacuum drying oven to dry to constant weight to obtain phosphorus-containing flame retardant intermediate. S5. Add 3g of phosphorus-containing flame retardant intermediate, 7mL of 3,6,9,12-tetraoxotetradec-13en-1-ol, 0.12g of magnesium chloride, 3.7mL of triethylamine and 20mL of tetrahydrofuran to the reactor, and reflux at 67℃ for 18h. After the reaction is completed, filter to remove the solid, concentrate the filtrate under reduced pressure and elute by column chromatography to obtain the crosslinking modifier.

[0027] Example 2: A crack-resistant halogen-free flame-retardant cable, comprising the following steps: Step 1: 60g of high-density polyethylene, 40g of low-density polyethylene, 1g of fumed silica, 3g of the crosslinking modifier prepared in Example 1, 5g of zinc borate, 2g of polyethylene wax and 0.3g of antioxidant 1076 are mixed, melt-extruded and coated onto the surface of a copper conductor, and then irradiated for crosslinking and curing to form an insulating layer, thus obtaining an insulated wire core. The second step is to twist the insulated wire cores together and fill the gaps with glass fiber filaments to form a filling layer. The third step is to wrap polyethylene around the filler layer to form an inner liner layer; Step 4: Use galvanized steel wire to weave the inner lining layer with a weaving density of ≥90% to form an armor layer; Step 5: Extruding high-density polyethylene over the armor layer to form a protective layer, resulting in a crack-resistant, halogen-free, flame-retardant cable.

[0028] Example 3 A crack-resistant halogen-free flame-retardant cable, comprising the following steps: Step 1: 65g of high-density polyethylene, 35g of low-density polyethylene, 2g of fumed silica, 4g of the crosslinking modifier prepared in Example 1, 6.5g of zinc borate, 2.5g of oxidized polyethylene wax and 0.4g of antioxidant 1010 are mixed, melt-extruded and coated onto the surface of a copper conductor, and then irradiated for crosslinking and curing to form an insulating layer, thus obtaining an insulated wire core. The second step is to twist the insulated wire cores together and fill the gaps with aramid fibers to form a filling layer. The third step is to wrap the non-woven fabric around the filling layer to form the inner lining layer; Step 4: Weave stainless steel wire outside the inner lining layer with a weaving density of ≥90% to form an armor layer; Step 5: Extrude polyurethane onto the outside of the armor layer to form a protective layer, resulting in a crack-resistant, halogen-free, flame-retardant cable.

[0029] Example 4 A crack-resistant halogen-free flame-retardant cable, comprising the following steps: Step 1: 70g of high-density polyethylene, 30g of low-density polyethylene, 3g of fumed silica, 5g of the crosslinking modifier prepared in Example 1, 8g of zinc borate, 3g of zinc stearate and 0.5g of antioxidant 1076 are mixed and melt-extruded and coated onto the surface of a copper conductor. Then, they are irradiated and crosslinked to form an insulating layer, thus obtaining an insulated wire core. The second step is to twist the insulated wire cores together and fill the gaps with non-woven fabric to form a filling layer. The third step is to wrap the non-woven fabric of the inner lining layer around the filling layer to form the inner lining layer. Step 4: Aluminum alloy wire is woven on the outside of the inner lining layer with a weaving density of ≥90% to form an armor layer; Step 5: Extrude high-density polyethylene sheathing material onto the outside of the armor layer to form a protective layer, thus obtaining a crack-resistant halogen-free flame-retardant cable.

[0030] Comparative Example 1: A crack-resistant halogen-free flame-retardant cable, comprising the following steps: Step 1: 70g of high-density polyethylene, 30g of low-density polyethylene, 3g of fumed silica, 5g of trimethylolpropane trimethacrylate, 8g of zinc borate, 3g of zinc stearate and 0.5g of antioxidant 1076 are mixed, melt-extruded and coated onto the surface of a copper conductor, and then irradiated for cross-linking and curing to form an insulating layer, thus obtaining an insulated wire core. The second step is to twist the insulated wire cores together and fill the gaps with non-woven fabric to form a filling layer. The third step is to wrap the non-woven fabric of the inner lining layer around the filling layer to form the inner lining layer. Step 4: Aluminum alloy wire is woven on the outside of the inner lining layer with a weaving density of ≥90% to form an armor layer; Step 5: Extrude high-density polyethylene sheathing material onto the outside of the armor layer to form a protective layer, thus obtaining a crack-resistant halogen-free flame-retardant cable.

[0031] The difference between this comparative example and Example 1 is that the crosslinking modifier is replaced with trimethylolpropane trimethacrylate, while the rest of the preparation process is the same as in Example 4.

[0032] Performance testing The insulation layers in Examples 1-5 and Comparative Example 1 were subjected to performance tests: The tensile strength and elongation at break of the insulation layer of each group of cross-linked polyethylene insulated power cables were tested in accordance with GB / T2951.21-2008 "General Test Methods for Insulation and Sheath Materials of Cables and Optical Cables", and the elongation at break retention rate after heat aging at 150℃ for 168h was also tested. The flame retardancy rating of each group of cable sheath materials was tested in accordance with GB / T19666-2019 "General Rules for Flame Retardant and Fire Resistant Wires, Cables or Optical Cables". The mechanical properties and flame retardancy test results are shown in Table 1.

[0033] Table 1: Statistical Table of Mechanical Properties and Flame Retardant Properties Test Results

[0034] As shown in Table 1, the tensile strength, elongation at break, and retention rate after thermal aging of Examples 2-4 are all superior to those of Comparative Example 1, indicating that the stress dissipation of the flexible ether segments and the chemical anchoring of the active double bonds jointly endow the cable with excellent long-term crack resistance. At the same time, the flame retardant rating of the examples all reached V-0, which is superior to V-3 of the comparative example, confirming the high efficiency of multiple synergistic char formation mechanisms within the molecule. The comprehensive data show that the present invention, through modification with a crosslinking modifier, enables the cable of the present invention to have excellent crack resistance, long-term thermal stability, and halogen-free flame retardancy.

[0035] The foregoing has provided a detailed description of one embodiment of the present invention, but this description is merely a preferred embodiment and should not be construed as limiting the scope of the invention. All equivalent variations and modifications made within the scope of the claims of this invention should still fall within the patent coverage of this invention.

Claims

1. A method for preparing a crack-resistant halogen-free flame-retardant cable, characterized in that, Includes the following steps: The first step involves blending high-density polyethylene, low-density polyethylene, fumed silica, crosslinking modifier, zinc borate, lubricant, and antioxidant, then melt-extruding the mixture and coating it onto the surface of a copper conductor. This process is followed by irradiation crosslinking and curing to form an insulating layer, resulting in an insulated wire core. The second step is to twist the insulated wire cores together and fill the gaps with filler material to form a filler layer; The third step is to wrap the inner lining material around the filling layer to form the inner lining layer. Step 4: Weave armored metal wires on the outside of the inner lining layer with a weaving density of ≥90% to form an armored layer; Step 5: Extrude the sheath material over the armor layer to form a protective layer, thus obtaining a crack-resistant halogen-free flame-retardant cable; The crosslinking modifier is prepared by amino-protecting 4-bromo-1,3,5-triazine-2-amine and then reacting it with pinacol diboronate to obtain a boron-containing flame retardant precursor, followed by amino deprotection to obtain a boron-containing flame retardant monomer, then reacting the boron-containing flame retardant monomer with phosphorus pentachloride to obtain a phosphorus-containing flame retardant intermediate, and finally reacting it with 3,6,9,12-tetraoxotetradec-13en-1-ol for nucleophilic substitution.

2. The method for preparing a crack-resistant halogen-free flame-retardant cable according to claim 1, characterized in that, The lubricant in the first step is any one of polyethylene wax, oxidized polyethylene wax, or zinc stearate, and the antioxidant is any one of antioxidant 1076 or antioxidant 1010.

3. The method for preparing a crack-resistant halogen-free flame-retardant cable according to claim 1, characterized in that, The mass ratio of high-density polyethylene, low-density polyethylene, fumed silica, crosslinking modifier, zinc borate, lubricant and antioxidant in the first step is 60~70:30~40:1~3:3~5:5~8:2~3:0.3~0.

5.

4. The method for preparing a crack-resistant halogen-free flame-retardant cable according to claim 1, characterized in that, The filling material in the second step is any one of glass fiber filaments, aramid filaments, cotton thread, or non-woven fabric; the inner lining material in the third step is any one of polyethylene or non-woven fabric.

5. The method for preparing a crack-resistant halogen-free flame-retardant cable according to claim 1, characterized in that, The armor wire in the fourth step is any one of galvanized steel wire, stainless steel wire, copper wire, and aluminum alloy wire; the sheath material in the fifth step is any one of high-density polyethylene and polyurethane.

6. The method for preparing a crack-resistant halogen-free flame-retardant cable according to claim 1, characterized in that, The preparation method of the crosslinking modifier includes the following steps: S1. Take 4-bromo-1,3,5-triazine-2-amine and dichloromethane into a reactor, and add triethylamine and 4-dimethylaminopyridine to it in sequence. Under ice-water bath conditions, slowly add ditert-butyl dicarbonate. After the addition is complete, restore the temperature to room temperature and stir the reaction for 1-2 hours to obtain a nitrogen-containing flame retardant monomer. S2. Under a nitrogen atmosphere, nitrogen-containing flame retardant monomer, pinacol diborate, potassium acetate, tetra(triphenylphosphine)palladium and 1,4-dioxane are sequentially added to the reactor and refluxed at 100~110℃ for 18~24h to obtain a boron-containing flame retardant precursor. S3. Add the boron-containing flame retardant precursor and dichloromethane to the reactor, and slowly add trifluoroacetic acid dropwise while stirring at room temperature. After the addition is complete, concentrate the mixture by rotary evaporation under reduced pressure, and adjust the pH of the system to 7-8 with saturated sodium bicarbonate aqueous solution to obtain the boron-containing flame retardant monomer. S4. Add boron-containing flame retardant monomer, phosphorus pentachloride, triethylamine and chlorobenzene to the reactor, heat to 100~110℃, react for 3~4h to obtain phosphorus-containing flame retardant intermediate; S5. Add phosphorus-containing flame retardant intermediate, 3,6,9,12-tetraoxotetradec-13en-1-ol, magnesium chloride, triethylamine and tetrahydrofuran into a reactor, and reflux at 66~68℃ for 16~18h to obtain crosslinking modifier.

7. The method for preparing a crack-resistant halogen-free flame-retardant cable according to claim 6, characterized in that, In step S1, the molar ratio of 4-bromo-1,3,5-triazine-2-amine, triethylamine, 4-dimethylaminopyridine, and ditert-butyl dicarbonate is 1:2.0~2.5:0.1~0.3:1~1.2; in step S2, the molar ratio of nitrogen-containing flame-retardant monomer, pinacol diborate, potassium acetate, and tetrakis(triphenylphosphine)palladium is 1:1~1.2:2.5~3:0.03~0.

05.

8. The method for preparing a crack-resistant halogen-free flame-retardant cable according to claim 6, characterized in that, The molar ratio of the boron-containing flame-retardant precursor to trifluoroacetic acid in step S3 is 1:10~15; the molar ratio of the boron-containing monomer, phosphorus pentachloride, and triethylamine in step S4 is 1:1~1.2:3~3.

3.

9. The method for preparing a crack-resistant halogen-free flame-retardant cable according to claim 6, characterized in that, The molar ratio of the phosphorus-containing flame-retardant intermediate, 3,6,9,12-tetraoxotetradec-13en-1-ol, magnesium chloride, and triethylamine in step S5 is 1:3.3~3.5:0.1~0.3:3.0~3.

5.

10. A crack-resistant, halogen-free flame-retardant cable, characterized in that, It is prepared by the preparation method described in any one of claims 1 to 9.

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