Radiation-resistant halogen-free flame-retardant cable material for nuclear power station cable and preparation method thereof

Abstract

The invention belongs to the technical field of high polymer materials, and particularly relates to a radiation-resistant halogen-free flame-retardant cable material for a nuclear power station cable and a preparation method thereof. The cable material is prepared from the following components in parts by mass: 50 parts of ethylene-vinyl acetate copolymer, 20 parts of ethylene propylene diene monomer, 20 parts of ethylene-octylene copolymer, 10 parts of maleic anhydride grafted ethylene-octylene copolymer, 3 to 6 parts of silicone master batch, 180 to 220 parts of active magnesium hydroxide, 40 to 60 parts of bismuth hydroxide, 10 to 20 parts of flame-retardant synergist, 3 to 6 parts of main antioxidant and 1 to 3 parts of auxiliary antioxidant. 2 to 4 parts of TAIC (triallyl isocyanurate) and 3 to 6 parts of octaphenylcyclotetrasiloxane; the cable material has excellent radiation-resistant stability, halogen-free environment-friendly flame retardance, balanced mechanical properties and long-term thermal stability, the preparation process is simple, and the cost is controllable.

Description

Technical Field

[0001] This invention relates to the field of polymer materials technology, specifically to a radiation-resistant, halogen-free, flame-retardant cable material suitable for nuclear power plant cables and its preparation method. Background Technology

[0002] Currently, the main radiation protection solutions for radiation-resistant cable materials on the market are as follows: 1. Using polymers containing aromatic rings as the base material to achieve radiation resistance; 2. Adding compounds containing aromatic rings as radiation-resistant additives through various processes, such as polyimide and polyphenylene ether; 3. Using oxides of elements with a large number of protons as radiation-resistant additives, such as antimony trioxide. These solutions suffer from drawbacks such as high cost, complex processes, and poor flame retardant performance. This invention achieves excellent radiation resistance and flame retardant performance while reducing material costs by using octaphenylcyclotetrasiloxane and bismuth hydroxide as radiation-resistant additives. Summary of the Invention

[0003] To address the issues of high cost, complex manufacturing process, and insufficient flame retardant properties in existing radiation-resistant cable materials for nuclear power plants, this paper proposes a cable material with excellent radiation resistance, good halogen-free flame retardant effect, low cost, and simple preparation process, along with its preparation method.

[0004] The technical solution adopted in this invention is: The first objective of this invention is to provide a radiation-resistant, halogen-free, flame-retardant cable material for nuclear power plant cables, comprising the following components by weight: 50 parts of ethylene-vinyl acetate copolymer, 20 parts of ethylene propylene diene monomer (EPDM) rubber, 20 parts of ethylene-octene copolymer, 10 parts of maleic anhydride-grafted ethylene-octene copolymer, 3-6 parts of silicone masterbatch, 180-220 parts of active magnesium hydroxide, 40-60 parts of bismuth hydroxide, 10-20 parts of flame retardant synergist, 3-6 parts of primary antioxidant, 1-3 parts of secondary antioxidant, 2-4 parts of TAIC, and 3-6 parts of octaphenylcyclotetrasiloxane.

[0005] Furthermore, the vinyl acetate content in the ethylene-vinyl acetate copolymer is ≥33%.

[0006] Furthermore, the preparation method of the active magnesium hydroxide is as follows: (1) Weigh anhydrous magnesium sulfate and distilled water respectively, prepare a magnesium sulfate solution with a mass fraction of 5.91%, and then heat and stir in an 85℃ water bath for 1 hour to obtain a uniform transparent magnesium sulfate slurry. (2) Transfer the above magnesium sulfate slurry to a carbonized quartz reaction tube with a stirrer, and slowly add 1 mol / L ammonium carbonate solution (dropping rate 2 ml / min) at a water bath temperature of 35°C. Continue stirring until the pH of the slurry stabilizes at 7.0, then stop adding the solution and continue stirring for 15 min to obtain a white magnesium carbonate slurry. (3) Weigh out sodium hydroxide and distilled water respectively, and prepare a sodium hydroxide solution with a mass fraction of 22.58%; slowly add the solution to the magnesium carbonate slurry obtained in step (2), heat in a water bath at 80°C, stir and react for 0.5 h to obtain a milky white magnesium hydroxide slurry; (4) Weigh 0.5g of lauric acid and 4g of sodium hydroxide, add them to a mixed solvent of 20ml of anhydrous ethanol and 50ml of distilled water, heat and stir in an 80℃ water bath for 0.5h until the lauric acid is completely dissolved to form a transparent sodium laurate modified solution; quickly transfer the modified solution to the magnesium hydroxide slurry obtained in step (3), stir in an 80℃ water bath for 0.5h to continue the reaction, and obtain a white slurry of active magnesium hydroxide complex; (5) The composite slurry obtained in step (4) was vacuum filtered (filtration pressure -0.08MPa), the filter cake was collected and washed three times with distilled water (50ml each time); the washed filter cake was transferred to an 80℃ constant temperature oven and dried for 24h. After cooling to room temperature, it was ground through a 100-mesh sieve to obtain active magnesium hydroxide.

[0007] Furthermore, the flame retardant synergist is zinc borate.

[0008] Furthermore, the primary antioxidant is antioxidant 1010.

[0009] Furthermore, the auxiliary antioxidant is antioxidant 168.

[0010] The second objective of this invention is to provide a method for preparing radiation-crosslinked, radiation-resistant, halogen-free, low-smoke, flame-retardant cable material for nuclear power plant cables, comprising the following steps: Step 1: Weigh the raw materials of each component according to the formula ratio; Step 2: Add all raw materials to a mixer at a temperature of 140-160℃ and melt-mix for 10-20 minutes; Step 3: Add the molten material obtained in Step 2 to a twin-screw extruder, extrude and granulate it at a temperature of 160-180℃, and air-cool it to room temperature to obtain the cable material.

[0011] Compared with existing technologies, the radiation-resistant halogen-free flame-retardant cable material for nuclear power plant cables and its preparation method provided by this invention have the following advantages: This invention employs a multi-component resin blend system consisting of ethylene-vinyl acetate copolymer, ethylene propylene diene monomer (EPDM) rubber, and ethylene-octene copolymer, and introduces maleic anhydride-grafted POE as a compatibilizer, effectively resolving the contradiction between flexibility, strength, and processability in a single resin matrix. Specifically, the high VA content of EVA enhances the wettability of the matrix to inorganic flame retardants, EPDM imparts excellent weather resistance and aging resistance, and POE strengthens the toughness and impact resistance of the matrix. Furthermore, the polar groups of maleic anhydride-grafted POE can form chemical bonds with the hydroxyl groups on the surface of inorganic flame retardants, significantly improving the dispersion uniformity of inorganic powders in the organic matrix and avoiding the deterioration of material mechanical properties caused by high levels of flame retardant filler. This invention employs a composite flame-retardant system composed of magnesium hydroxide, bismuth hydroxide, and zinc borate, achieving a multi-layered flame-retardant mechanism involving physical cooling, chemical flame suppression, and synergistic char formation. The active magnesium hydroxide, modified with sodium laurate, exhibits enhanced surface hydrophobicity, resulting in more uniform dispersion in the matrix and the ability to decompose and release water of crystallization at high temperatures. This physical cooling inhibits combustion while simultaneously generating a dense MgO char layer to block oxygen and heat transfer. Combined with the synergistic effect of zinc borate, this further promotes char layer formation and prevents dripping during combustion. Bismuth hydroxide, in addition to being a radiation-resistant additive, decomposes during combustion to generate bismuth trioxide, which synergistically catalyzes polymer crosslinking with zinc borate to form char, enhancing the density of the char layer. This invention utilizes the synergistic effect of primary antioxidant 1010 and secondary antioxidant 168 to effectively capture free radicals generated during polymer processing and service, thus inhibiting oxidative degradation. TAIC (tracene propyl isocyanurate), as a crosslinking agent, can form a three-dimensional crosslinked network with the resin matrix during processing, further enhancing the material's thermal stability and radiation resistance. The silicone masterbatch can reduce melt viscosity, improve material processing fluidity, and avoid extrusion granulation difficulties caused by high-filler systems. The cable material of this invention is prepared using a process that only requires internal melting and mixing, and twin-screw extrusion granulation. The process is simple and the cost is controllable, providing key material support for the safe and reliable operation of cables in nuclear power plants. Detailed Implementation

[0012] The present invention will be further described below through specific embodiments, but this is not a limitation of the present invention. Those skilled in the art can make various modifications or improvements based on the basic idea of ​​the present invention, but as long as they do not depart from the basic idea of ​​the present invention, they are all within the protection scope of the present invention.

[0013] Unless otherwise specified, the methods used in the following examples and comparative examples are all prior art; reagents not specifically mentioned are conventional reagents, all of which can be purchased from conventional reagent manufacturers and distributors. Information such as the manufacturers or CAS numbers of some raw materials is as follows: Ethylene-vinyl acetate copolymer, CAS number 24937-78-8; EPDM rubber was purchased from Shanghai Tingyuan Plastics Technology Co., Ltd. Ethylene-octene copolymer, purchased from Suzhou Damai Plastics Co., Ltd.; Maleic anhydride-grafted ethylene-octene copolymer was purchased from Wuxi Yiyuan New Material Technology Co., Ltd. Silicone masterbatch was purchased from Chengdu Silike Technology Co., Ltd. Bismuth hydroxide, CAS No. 10361-43-0, was purchased from Shandong Jinshengtai Chemical Co., Ltd. TAIC, CAS No. 1025-15-6, was purchased from Shanghai Dunmei New Materials Technology Co., Ltd. Octaphenylcyclotetrasiloxane was purchased from Jinan World Chemical Co., Ltd. Zinc borate was purchased from Shandong Wuwei Flame Retardant Technology Co., Ltd. Antioxidant 1010, CAS number 6683-19-8; Antioxidant 168, CAS number 31570-04-4.

[0014] Example 1: A radiation-resistant, halogen-free, flame-retardant cable material for nuclear power plant cables, comprising the following components (100g / part) by weight: 50 parts ethylene-vinyl acetate copolymer, 20 parts ethylene propylene diene monomer (EPDM) rubber, 20 parts ethylene-octene copolymer, 10 parts maleic anhydride-grafted ethylene-octene copolymer, 3 parts silicone masterbatch, 180 parts activated magnesium hydroxide, 40 parts bismuth hydroxide, 10 parts flame retardant synergist (zinc borate), 3 parts primary antioxidant (antioxidant 1010), 1 part secondary antioxidant (antioxidant 168), 2 parts TAIC, and 3 parts octaphenylcyclotetrasiloxane. The specific preparation steps are as follows: Step 1: Weigh the raw materials of each component according to the formula ratio; Step 2: Add all raw materials to a mixer at 160℃ and melt-mix for 20 minutes; Step 3: Add the molten material obtained in Step 2 to a twin-screw extruder, extrude and granulate it at a temperature of 160°C, and air-cool it to room temperature to obtain the cable material.

[0015] The preparation method of activated magnesium hydroxide is as follows: (1) Weigh 22g of anhydrous magnesium sulfate, transfer it to 350ml of distilled water to prepare a magnesium sulfate solution, and then heat and stir it in an 85℃ water bath for 1h to obtain a uniform transparent magnesium sulfate slurry. (2) Transfer the above magnesium sulfate slurry to a carbonized quartz reaction tube with a stirrer, and slowly add 1 mol / L ammonium carbonate solution (dropping rate 2 ml / min) at a water bath temperature of 35°C. Continue stirring until the pH of the slurry stabilizes at 7.0, then stop adding the solution and continue stirring for 15 min to obtain a white magnesium carbonate slurry. (3) Weigh 35g of sodium hydroxide, dissolve it in 120ml of distilled water to prepare a sodium hydroxide solution; slowly add the solution to the magnesium carbonate slurry obtained in step (2), heat it in a water bath at 80℃, stir and react for 0.5h to obtain a milky white magnesium hydroxide slurry; (4) Weigh 0.5g of lauric acid and 4g of sodium hydroxide, add them to a mixed solvent of 20ml of anhydrous ethanol and 50ml of distilled water, heat and stir in an 80℃ water bath for 0.5h until the lauric acid is completely dissolved to form a transparent sodium laurate modified solution; quickly transfer the modified solution to the magnesium hydroxide slurry obtained in step (3), stir in an 80℃ water bath for 0.5h to continue the reaction, and obtain a white slurry of active magnesium hydroxide complex; (5) The composite slurry obtained in step (4) was vacuum filtered (filtration pressure -0.08MPa), the filter cake was collected and washed three times with distilled water (50ml each time); the washed filter cake was transferred to an 80℃ constant temperature oven and dried for 24h. After cooling to room temperature, it was ground through a 100-mesh sieve to obtain active magnesium hydroxide.

[0016] Example 2: A radiation-resistant, halogen-free, flame-retardant cable material for nuclear power plant cables, comprising the following components (150g / part) by weight: 50 parts ethylene-vinyl acetate copolymer, 20 parts ethylene propylene diene monomer (EPDM) rubber, 20 parts ethylene-octene copolymer, 10 parts maleic anhydride-grafted ethylene-octene copolymer, 5 parts silicone masterbatch, 210 parts activated magnesium hydroxide, 50 parts bismuth hydroxide, 15 parts flame retardant synergist (zinc borate), 4 parts primary antioxidant (antioxidant 1010), 2 parts secondary antioxidant (antioxidant 168), 3 parts TAIC, and 5 parts octaphenylcyclotetrasiloxane. The specific preparation steps are as follows: Step 1: Weigh the raw materials of each component according to the formula ratio; Step 2: Add all raw materials to a mixer at 140℃ and melt-mix for 15 minutes; Step 3: Add the molten material obtained in Step 2 to a twin-screw extruder, extrude and granulate it at a temperature of 170°C, and air-cool it to room temperature to obtain the cable material.

[0017] The preparation method of activated magnesium hydroxide is as follows: (1) Weigh 22g of anhydrous magnesium sulfate, transfer it to 350ml of distilled water to prepare a magnesium sulfate solution, and then heat and stir it in an 85℃ water bath for 1h to obtain a uniform transparent magnesium sulfate slurry. (2) Transfer the above magnesium sulfate slurry to a carbonized quartz reaction tube with a stirrer, and slowly add 1 mol / L ammonium carbonate solution (dropping rate 2 ml / min) at a water bath temperature of 35°C. Continue stirring until the pH of the slurry stabilizes at 7.0, then stop adding the solution and continue stirring for 15 min to obtain a white magnesium carbonate slurry. (3) Weigh 35g of sodium hydroxide, dissolve it in 120ml of distilled water to prepare a sodium hydroxide solution; slowly add the solution to the magnesium carbonate slurry obtained in step (2), heat it in a water bath at 80℃, stir and react for 0.5h to obtain a milky white magnesium hydroxide slurry; (4) Weigh 0.5g of lauric acid and 4g of sodium hydroxide, add them to a mixed solvent of 20ml of anhydrous ethanol and 50ml of distilled water, heat and stir in an 80℃ water bath for 0.5h until the lauric acid is completely dissolved to form a transparent sodium laurate modified solution; quickly transfer the modified solution to the magnesium hydroxide slurry obtained in step (3), stir in an 80℃ water bath for 0.5h to continue the reaction, and obtain a white slurry of active magnesium hydroxide complex; (5) The composite slurry obtained in step (4) was vacuum filtered (filtration pressure -0.08MPa), the filter cake was collected and washed three times with distilled water (50ml each time); the washed filter cake was transferred to an 80℃ constant temperature oven and dried for 24h. After cooling to room temperature, it was ground through a 100-mesh sieve to obtain active magnesium hydroxide.

[0018] Example 3: A radiation-resistant, halogen-free, flame-retardant cable material for nuclear power plant cables, comprising the following components (200g / part) by weight: 50 parts ethylene-vinyl acetate copolymer, 20 parts ethylene propylene diene monomer (EPDM) rubber, 20 parts ethylene-octene copolymer, 10 parts maleic anhydride-grafted ethylene-octene copolymer, 6 parts silicone masterbatch, 220 parts activated magnesium hydroxide, 60 parts bismuth hydroxide, 20 parts flame retardant synergist (zinc borate), 6 parts primary antioxidant (antioxidant 1010), 3 parts secondary antioxidant (antioxidant 168), 4 parts TAIC, and 6 parts octaphenylcyclotetrasiloxane. The specific preparation steps are as follows: Step 1: Weigh the raw materials of each component according to the formula ratio; Step 2: Add all raw materials to a mixer at 150℃ and melt-mix for 10 minutes; Step 3: Add the molten material obtained in Step 2 to a twin-screw extruder, extrude and granulate it at a temperature of 180°C, and air-cool it to room temperature to obtain the cable material.

[0019] The preparation method of activated magnesium hydroxide is as follows: (1) Weigh 22g of anhydrous magnesium sulfate, transfer it to 350ml of distilled water to prepare a magnesium sulfate solution, and then heat and stir it in an 85℃ water bath for 1h to obtain a uniform transparent magnesium sulfate slurry. (2) Transfer the above magnesium sulfate slurry to a carbonized quartz reaction tube with a stirrer, and slowly add 1 mol / L ammonium carbonate solution (dropping rate 2 ml / min) at a water bath temperature of 35°C. Continue stirring until the pH of the slurry stabilizes at 7.0, then stop adding the solution and continue stirring for 15 min to obtain a white magnesium carbonate slurry. (3) Weigh 35g of sodium hydroxide, dissolve it in 120ml of distilled water to prepare a sodium hydroxide solution; slowly add the solution to the magnesium carbonate slurry obtained in step (2), heat it in a water bath at 80℃, stir and react for 0.5h to obtain a milky white magnesium hydroxide slurry; (4) Weigh 0.5g of lauric acid and 4g of sodium hydroxide, add them to a mixed solvent of 20ml of anhydrous ethanol and 50ml of distilled water, heat and stir in an 80℃ water bath for 0.5h until the lauric acid is completely dissolved to form a transparent sodium laurate modified solution; quickly transfer the modified solution to the magnesium hydroxide slurry obtained in step (3), stir in an 80℃ water bath for 0.5h to continue the reaction, and obtain a white slurry of active magnesium hydroxide complex; (5) The composite slurry obtained in step (4) was vacuum filtered (filtration pressure -0.08MPa), the filter cake was collected and washed three times with distilled water (50ml each time); the washed filter cake was transferred to an 80℃ constant temperature oven and dried for 24h. After cooling to room temperature, it was ground through a 100-mesh sieve to obtain active magnesium hydroxide.

[0020] Comparative Example 1 The difference from Example 3 is that the ethylene-methyl methacrylate copolymer replaces the ethylene-vinyl acetate copolymer in the raw materials, while the amount remains the same; The other steps and preparation process are the same as in Example 3.

[0021] Comparative Example 2 The difference from Example 3 is that bismuth carbonate replaces bismuth hydroxide in the raw materials, while the amount remains the same; The other steps and preparation process are the same as in Example 3.

[0022] Comparative Example 3 The difference from Example 3 is that methylphenylcyclotrisiloxane replaces octaphenylcyclotetrasiloxane in the raw materials, while the amount remains the same; The other steps and preparation process are the same as in Example 3.

[0023] Experimental Example: Performance Testing 1. Test materials: Radiation-resistant halogen-free flame-retardant cable materials prepared according to the embodiments and comparative examples of this invention.

[0024] 2. Test methods: (1) Radiation resistance test: According to the standard GB / T18380.12-2008 "Cables and optical cables - Burning test under flame conditions - Part 12: Vertical flame propagation test of single insulated wires and cables - 1kW premixed flame test method", the radiation resistance appendix is ​​as follows. Sample preparation: The cable materials of each embodiment and comparative example were pressed into 1mm thick sheets using a flat vulcanizing machine, and then punched into standard specimens of 100mm×15mm×1mm, with 3 parallel specimens per group. Test procedure: A cobalt-60 gamma-ray irradiation source was used, with the irradiation dose set at 500 kGy (typical value of cumulative radiation dose during long-term service of nuclear power plant cables), and the irradiation environment temperature at 23±2℃ and humidity at 50±5%. After irradiation, the samples were placed in an environment of 23±2℃ and left to stand for 24 hours. The tensile strength and elongation at break of the samples before and after irradiation were tested using an electronic universal testing machine (accuracy grade 0.5). The performance retention rate was calculated (retention rate = performance value after irradiation / performance value before irradiation × 100%). The volume resistivity of the irradiated sample was tested simultaneously (according to GB / T1410-2006) to evaluate the effect of radiation on electrical insulation performance. (2) Halogen-free flame retardant performance test Standards followed: UL94-2021 "Tests on the flammability of plastic materials for use in equipment and appliance components" (vertical burning method) and GB / T17650.2-1998 "Test methods for gases released during combustion of materials derived from cables or optical fibers - Part 2: Determination of acidity of gases by measuring pH and conductivity". Sample preparation: Vertical combustion specimens: pressed into strips measuring 127mm × 12.7mm × 1.6mm, 5 specimens per group; Smoke and toxicity samples: pressed into 50mm×50mm×3mm cubes, 3 samples per group; Test steps: Vertical burning: Fix the sample vertically, ignite the bottom of the sample with a 19mm flame for 10s, remove the flame, and record the afterburning time; if the afterburning is ≤10s, ignite again for 10s, record the second afterburning time and whether the sample drippings ignite the degreased cotton 300mm below, and determine the flame retardant rating (V-0 / V-1 / V-2). Acid mist release: Place the sample in a sealed combustion chamber and ignite it. Collect the condensate of the combustion gas and test the pH value (≥4.3 is acceptable) and conductivity (≤10μS / mm is acceptable) to evaluate the halogen-free characteristics.

[0025] (3) Mechanical property testing According to the standard GB / T1040.3-2006 "Determination of tensile properties of plastics - Part 3: Test conditions for films and sheets" Sample preparation: 100mm × 15mm × 1mm specimens as used in radiation resistance testing. Test procedure: Set the tensile speed of the electronic universal testing machine to 50 mm / min, test the tensile strength (MPa) and elongation at break (%), take the average value of 5 parallel samples, and test the Shore A hardness of the sample at the same time (according to GB / T2411-2008). (4) Thermal stability performance test Standard based on: GB / T2951.31-2008 "General Test Methods for Insulation and Sheath Materials of Cables and Optical Fibers - Part 31: Determination of Antioxidant Content in Polyolefin Insulation and Sheath Materials A: Liquid Extraction Method / Method B: Thermogravimetric Analysis (TGA)" Sample preparation: Take 10mg of cable material powder as a sample. Test Procedure: Using a thermogravimetric analyzer (TGA) under a nitrogen atmosphere (flow rate 50 mL / min) and a heating rate of 10 °C / min, thermogravimetric curves were tested in the range of 30–600 °C. The 5% thermogravimetric temperature (T5%) and the maximum thermogravimetric rate temperature (Tmax) were recorded to evaluate long-term thermal stability. 3. Test results are shown in Table 1.

[0026] Table 1. Performance test results of cable materials obtained from the examples and comparative examples. Performance indicators Example 1 Example 2 Example 3 Comparative Example 1 Comparative Example 2 Comparative Example 3 Tensile strength (MPa) before irradiation 12.8 13.5 14.2 12.5 13.8 13.6 Tensile strength after irradiation (MPa) 11.0 11.9 12.8 7.3 9.2 8.9 Tensile strength retention rate (%) 85.9 88.1 90.1 58.4 66.7 65.4 Elongation at break before irradiation (%) 385 410 430 370 405 400 Elongation at break after irradiation (%) 330 355 380 175 220 210 Elongation at break retention rate (%) 85.7 86.6 88.4 47.3 54.3 52.5 Volume resistivity after irradiation (Ω·cm) <![CDATA[2.5×10 14 ]]> <![CDATA[3.1×10 14 ]]> <![CDATA[3.5×10 14 ]]> <![CDATA[8.2×10 12 ]]> <![CDATA[1.1×10 13 ]]> <![CDATA[9.5×10 12 ]]> UL 94 flame retardant rating V-0 V-0 V-0 V-1 V-2 (dripping ignition) V-1 pH value after combustion 5.2 5.5 5.8 4.8 4.5 4.7 Electrical conductivity after combustion (μS / mm) 6.8 6.2 5.5 8.5 9.2 8.8 Shore A hardness 78 80 82 75 81 80 5% thermogravimetric temperature T5% (°C) 325 332 340 305 318 315 Maximum thermogravimetric temperature Tmax (°C) 420 428 435 402 415 412 As shown in Table 1, the performance test results of the radiation-resistant halogen-free flame-retardant cable material obtained in the embodiments of the present invention are all good, and it has excellent radiation resistance and flame retardant properties; while the performance of each comparative example is affected to varying degrees.

[0027] The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit the invention. Any person skilled in the art can modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by those skilled in the art without departing from the spirit and technical concept disclosed in the present invention should still be covered by the claims of the present invention.

Claims

1. A radiation-resistant, halogen-free, flame-retardant cable material for nuclear power plant cables, characterized in that, The composition by weight is as follows: 50 parts ethylene-vinyl acetate copolymer, 20 parts ethylene propylene diene monomer (EPDM) rubber, 20 parts ethylene-octene copolymer, 10 parts maleic anhydride-grafted ethylene-octene copolymer, 3-6 parts silicone masterbatch, 180-220 parts active magnesium hydroxide, 40-60 parts bismuth hydroxide, 10-20 parts flame retardant synergist, 3-6 parts primary antioxidant, 1-3 parts secondary antioxidant, 2-4 parts TAIC, and 3-6 parts octaphenylcyclotetrasiloxane.

2. The radiation-resistant, halogen-free, flame-retardant cable material for nuclear power plant cables as described in claim 1, characterized in that, The vinyl acetate content in the ethylene-vinyl acetate copolymer is ≥33%.

3. The radiation-resistant, halogen-free, flame-retardant cable material for nuclear power plant cables as described in claim 1, characterized in that, The preparation method of the active magnesium hydroxide is as follows: (1) Weigh anhydrous magnesium sulfate and distilled water respectively, prepare a magnesium sulfate solution with a mass fraction of 5.91%, and then heat and stir in an 85℃ water bath for 1 hour to obtain a uniform transparent magnesium sulfate slurry. (2) Transfer the above magnesium sulfate slurry to a carbonized quartz reaction tube with a stirrer, and slowly add 1 mol / L ammonium carbonate solution at a water bath temperature of 35°C. Continue stirring until the pH of the slurry stabilizes at 7.0, then stop adding the solution and continue stirring for 15 minutes to obtain a white magnesium carbonate slurry. (3) Weigh out sodium hydroxide and distilled water respectively, and prepare a sodium hydroxide solution with a mass fraction of 22.58%; slowly add the solution to the magnesium carbonate slurry obtained in step (2), heat in a water bath at 80°C, stir and react for 0.5 h to obtain a milky white magnesium hydroxide slurry; (4) Weigh 0.5g of lauric acid and 4g of sodium hydroxide, add them to a mixed solvent of 20ml of anhydrous ethanol and 50ml of distilled water, heat and stir in an 80℃ water bath for 0.5h until the lauric acid is completely dissolved to form a transparent sodium laurate modified solution. The modified liquid was quickly transferred to the magnesium hydroxide slurry obtained in step (3), and the reaction was continued for 0.5 h by stirring in a water bath at 80°C to obtain a white slurry of active magnesium hydroxide composite. (5) The composite slurry obtained in step (4) was vacuum filtered, the filter cake was collected and washed three times with distilled water; the washed filter cake was transferred to an 80°C constant temperature oven and dried for 24 hours. After cooling to room temperature, it was ground through a 100-mesh sieve to obtain active magnesium hydroxide.

4. The radiation-resistant, halogen-free, flame-retardant cable material for nuclear power plant cables as described in claim 1, characterized in that, The flame retardant synergist zinc borate.

5. The radiation-resistant, halogen-free, flame-retardant cable material for nuclear power plant cables as described in claim 1, characterized in that, The primary antioxidant is antioxidant 1010.

6. The radiation-resistant, halogen-free, flame-retardant cable material for nuclear power plant cables as described in claim 1, characterized in that, The auxiliary antioxidant is antioxidant 168.

7. A method for preparing radiation-crosslinked, radiation-resistant, halogen-free, low-smoke, flame-retardant cable material for nuclear power plant cables as described in any one of claims 1-6, characterized in that, Includes the following steps: Step 1: Weigh the raw materials of each component according to the formula ratio; Step 2: Add all raw materials to a mixer at a temperature of 140-160℃ and melt-mix for 10-20 minutes; Step 3: Add the molten material obtained in Step 2 to a twin-screw extruder, extrude and granulate it at a temperature of 160-180℃, and air-cool it to room temperature to obtain the cable material.