Radiation-resistant protective cable for nuclear power station and preparation method of radiation-resistant protective cable

Abstract

The invention discloses a radiation-resistant protective cable for a nuclear power station and a preparation method thereof, and belongs to the technical field of cables, the radiation-resistant protective cable for the nuclear power station comprises a cable body and a sheath layer, and the sheath layer comprises the following components in parts by mass: 100 parts of polypropylene resin, 20-40 parts of ethylene propylene diene monomer and 5-12 parts of modified multi-walled carbon nanotubes. 8-15 parts of a heat conduction enhancer, 2-6 parts of an antioxidant, 1-3 parts of a heat stabilizer and 4-8 parts of a plasticizer; the heat conduction reinforcing agent is prepared by carrying out surface modification on composite powder of aluminum nitride and boron nitride through a silane coupling agent. Through the synergistic effect of the modified multi-walled carbon nanotubes and the surface modified heat-conducting enhancer, the heat-conducting property, radiation resistance and heat stability of the cable are remarkably improved on the premise of keeping excellent electrical insulation property.

Description

Technical Field

[0001] This invention relates to the field of cable technology, specifically to a radiation-resistant protective cable for nuclear power plants and its manufacturing method. Background Technology

[0002] With the global energy structure adjustment and the rapid development of nuclear power technology, nuclear power plants, as an important component of clean energy, are playing an increasingly important role in the energy strategies of various countries. The internal cabling system of a nuclear power plant is the neural network for the safe operation of the entire plant, undertaking key functions such as power transmission, control signal transmission, and safety system monitoring. Unlike conventional power plants, nuclear power plant cables need to operate stably for extended periods under extremely harsh environmental conditions, including high-temperature and high-pressure environments, strong radiation fields, and potential accident scenarios. Nuclear power plant cables are classified into safety-grade and non-safety-grade cables according to their safety levels. Safety-grade cables are directly related to critical safety functions such as safe reactor shutdown, residual heat removal, and emergency cooling, and their performance requirements are more stringent. With the development of third-generation and fourth-generation nuclear power technologies, higher requirements have been placed on the radiation resistance, thermal conductivity, flame retardancy, and service life of cable materials, prompting cable technology to develop towards high performance and high reliability.

[0003] Currently, the cable sheathing materials widely used in nuclear power plants mainly include traditional polymer materials such as polyethylene, polypropylene, and ethylene propylene rubber. These materials have many technical defects in a nuclear radiation environment. First, there is the problem of insufficient radiation resistance. Traditional polyolefin materials are prone to molecular chain breakage or cross-linking reactions under gamma ray and neutron radiation, leading to material embrittlement, cracking, and a sharp decrease in mechanical strength. Second, there is the problem of poor thermal conductivity. The thermal conductivity of traditional polymer materials is much lower than that of metal materials, which can easily cause local overheating when the cable is carrying current, thereby accelerating material aging and creating a vicious cycle. Summary of the Invention

[0004] This invention discloses a radiation-resistant protective cable for nuclear power plants and its preparation method. Through the synergistic effect of modified multi-walled carbon nanotubes and surface-modified thermal conductivity enhancers, the thermal conductivity, radiation resistance and thermal stability of the cable are significantly improved while maintaining excellent electrical insulation performance, thus solving the technical problem of low thermal conductivity of cables in the prior art.

[0005] This invention claims protection for a radiation-resistant cable for nuclear power plants, comprising a cable body and a sheath layer, the sheath layer comprising the following components by weight:

[0006] 100 parts polypropylene resin, 20-40 parts EPDM rubber, 5-12 parts modified multi-walled carbon nanotubes, 8-15 parts thermal conductivity enhancer, 2-6 parts antioxidant, 1-3 parts heat stabilizer, and 4-8 parts plasticizer.

[0007] The thermal conductivity enhancer is prepared by surface modification of a composite powder of aluminum nitride and boron nitride with a silane coupling agent.

[0008] Preferably, the method for preparing the modified multi-walled carbon nanotubes includes the following steps:

[0009] Step 1: Mix multi-walled carbon nanotubes with nitric acid solution at a mass ratio of 1:10-15 and stir at room temperature for 20-40 min. After sonication for 1-3 h, filter and wash until neutral. Dry under vacuum at 60 °C for 10-15 h to obtain activated multi-walled carbon nanotubes.

[0010] Step 2: Disperse activated multi-walled carbon nanotubes and boric acid in deionized water at a mass ratio of 1:1.2-1.8, stir and react at 65-75℃ for 3-5 hours, filter and wash to obtain intermediate 1;

[0011] Step 3: Mix intermediate 1 with phosphoric acid solution at a mass ratio of 1:0.15-0.25 and stir at 75-85℃ for 2-4 hours. Wash with acetone 3 times and dry under vacuum at 60℃ for 6-10 hours to obtain intermediate 2.

[0012] Step 4: Disperse intermediate 2 and melamine in ethanol at a mass ratio of 1:2-3, reflux at 85-95℃ for 5-7 hours, filter and wash, and vacuum dry at 60℃ for 10-15 hours to obtain modified multi-walled carbon nanotubes.

[0013] Preferably, the mass ratio of the multi-walled carbon nanotubes to the nitric acid solution is 1:10 to 15.

[0014] Preferably, the concentration of the nitric acid solution is 65 wt%.

[0015] Preferably, the concentration of the phosphoric acid solution is 85 wt%.

[0016] Preferably, the method for preparing the thermal conductivity enhancer includes the following steps:

[0017] Aluminum nitride powder and boron nitride powder were mixed at a mass ratio of 2:1 to 4:1, ball-milled for 1 to 3 hours, and then passed through a 200-mesh sieve to obtain a composite powder. The composite powder was then dispersed in anhydrous ethanol with the silane coupling agent γ-aminopropyltriethoxysilane at a mass ratio of 50:0.8 to 1.2. The mixture was stirred at room temperature for 1 to 3 hours, then heated and stirred at 55 to 65°C for 3 to 5 hours. After filtration and washing, the mixture was vacuum dried at 50°C for 6 to 10 hours to obtain a thermal conductivity enhancer.

[0018] Preferably, the aluminum nitride powder has a particle size of 1 to 3 μm, and the boron nitride powder has a particle size of 0.5 to 2 μm.

[0019] Preferably, the antioxidant is distearate, the heat stabilizer is calcium stearate, and the plasticizer is dioctyl phthalate.

[0020] This invention also protects a method for preparing the above-mentioned radiation-resistant cable for nuclear power plants, comprising the following steps:

[0021] Polypropylene resin, EPDM rubber, antioxidant, heat stabilizer, plasticizer, modified multi-walled carbon nanotubes, and thermal conductivity enhancer are mixed evenly in a high-speed mixer, fed into a twin-screw extruder for melt extrusion molding, and extruded onto the cable body to obtain a radiation-resistant protective cable for nuclear power plants.

[0022] Preferably, the temperature range of the twin-screw extruder is set as follows: 150-170°C for the feeding section, 170-190°C for the compression section, 180-200°C for the homogenization section, 190-210°C for the die head, and the screw speed is 70-90 r / min.

[0023] The present invention has the following beneficial effects:

[0024] (1) In the preparation process of modified multi-walled carbon nanotubes, the present invention generates a large number of active groups such as carboxyl and hydroxyl groups on the surface of multi-walled carbon nanotubes through nitric acid activation treatment. Then, boric acid modification treatment introduces boron-oxygen bond structure on the surface of carbon nanotubes, which enhances the flame retardant properties of the material. Phosphoric acid modification treatment further forms phosphate ester bonds on the surface, giving the material excellent flame retardant synergistic effect. At the same time, melamine functionalization treatment grafts nitrogen-containing heterocyclic structures on the surface of carbon nanotubes, forming a molecular network structure with the ability to capture free radicals. The surface of the modified multi-walled carbon nanotubes contains abundant heteroatom functional groups such as boron, phosphorus, and nitrogen. These functional groups form strong chemical bonds with the matrix material, which significantly improves the compatibility and interfacial bonding strength between the filler and the matrix. The presence of boron atoms enhances the thermal stability of the material, phosphorus atoms provide excellent flame retardant properties, and nitrogen atoms endow the material with the ability to capture radiation-generated free radicals. The modified carbon nanotubes form a three-dimensional conductive network in the matrix, effectively shielding electromagnetic radiation. At the same time, the nitrogen-containing functional groups on their surface can capture radiation-generated free radicals and inhibit the radiation degradation reaction of the material.

[0025] (2) In this invention, aluminum nitride and boron nitride composite powder is surface modified with silane coupling agent and used as thermal conductivity enhancer to form good interfacial compatibility with polymer matrix, thereby constructing a continuous thermal conductivity path in the material and enhancing the thermal conductivity of the cable.

[0026] (3) The present invention prepares a radiation-resistant cable for nuclear power plants. Through the synergistic effect of modified multi-walled carbon nanotubes and surface-modified thermal conductivity enhancers, the thermal conductivity, radiation resistance and thermal stability of the cable are significantly improved while maintaining excellent electrical insulation performance. Detailed Implementation

[0027] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments. 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 of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0028] The multi-walled carbon nanotubes used in this application are from Xuzhou Jiechuang New Materials Technology Co., Ltd., CAS number 308068-56-6, with a particle size of 10-30 nm in diameter and 5-20 μm in length; the aluminum nitride powder used is from Shanghai Naio Nanotechnology Co., Ltd., with a particle size of 1 μm; the boron nitride powder used is from Beijing Forsman Technology Co., Ltd., with a particle size of 0.5-2 μm; the polypropylene resin used is from Shandong Fanglei Coatings Co., Ltd., model 518; the EPDM rubber used is from Shanghai Shengchuang Petrochemical Co., Ltd., grade 3722P; and the distearate thiopropionate used is from Wuhan Xingzhongcheng Technology Co., Ltd., product name antioxidant DSTOP, CAS number 693-36-7.

[0029] Example 1

[0030] Step 1: Preparation of modified multi-walled carbon nanotubes: Multi-walled carbon nanotubes were reacted with 65wt% nitric acid solution at a mass ratio of 1:12 at room temperature for 30 min, ultrasonically treated for 2 h, filtered and washed until neutral, and vacuum dried at 60℃ for 12 h to obtain activated multi-walled carbon nanotubes.

[0031] Step 2, Boric acid modification treatment: Activated multi-walled carbon nanotubes and boric acid were dispersed in deionized water at a mass ratio of 1:1.5, and stirred at 70°C for 4 hours. After filtration and washing, intermediate 1 was obtained.

[0032] Step 3, Phosphoric acid modification treatment: Intermediate 1 and 85wt% phosphoric acid solution were stirred at 80℃ for 3h at a mass ratio of 1:0.2, washed 3 times with acetone, and dried under vacuum at 60℃ for 8h to obtain intermediate 2.

[0033] Step 4, melamine functionalization: Intermediate 2 and melamine are dispersed in ethanol at a mass ratio of 1:2.5, and refluxed at 90°C for 6 hours. After filtration and washing, the mixture is vacuum dried at 60°C for 12 hours to obtain modified multi-walled carbon nanotubes.

[0034] Step 5: Preparation of thermal conductivity enhancer: Aluminum nitride powder (particle size 2μm) and boron nitride powder (particle size 1μm) are mixed at a mass ratio of 3:1, ball-milled for 2 hours, and then passed through a 200-mesh sieve to obtain a composite powder. The composite powder is dispersed in anhydrous ethanol with the silane coupling agent γ-aminopropyltriethoxysilane at a mass ratio of 50:1, stirred at room temperature for 2 hours, then heated and stirred at 60°C for 4 hours. After filtration and washing, it is vacuum dried at 50°C for 8 hours to obtain the thermal conductivity enhancer.

[0035] Step Six: Sheath Preparation: 100 parts of polypropylene resin, 30 parts of EPDM rubber, 8 parts of modified multi-walled carbon nanotubes, 12 parts of thermal conductivity enhancer, 4 parts of distearate thiopropionate, 2 parts of calcium stearate, and 6 parts of dioctyl phthalate are mixed evenly in a high-speed mixer. The mixture is then fed into a twin-screw extruder for melt extrusion molding, extruding and coating the cable body to obtain a radiation-resistant protective cable for nuclear power plants. Twin-screw extruder temperature settings: feeding section 160℃, compression section 180℃, homogenization section 190℃, die head 200℃, screw speed 80 r / min.

[0036] Example 2

[0037] Step 1: Preparation of modified multi-walled carbon nanotubes: Multi-walled carbon nanotubes were reacted with 65wt% nitric acid solution at a mass ratio of 1:10 at room temperature for 20 min, ultrasonically treated for 1 h, filtered and washed until neutral, and vacuum dried at 60℃ for 10 h to obtain activated multi-walled carbon nanotubes.

[0038] Step 2, Boric acid modification treatment: Activated multi-walled carbon nanotubes and boric acid were dispersed in deionized water at a mass ratio of 1:1.2, and stirred at 65°C for 3 hours. After filtration and washing, intermediate 1 was obtained.

[0039] Step 3, Phosphoric acid modification: Intermediate 1 and 85wt% phosphoric acid solution were stirred at 75℃ for 2h at a mass ratio of 1:0.15, washed 3 times with acetone, and dried under vacuum at 60℃ for 6h to obtain intermediate 2.

[0040] Step 4, melamine functionalization: Intermediate 2 and melamine are dispersed in ethanol at a mass ratio of 1:2, refluxed at 85°C for 5 hours, filtered and washed, and then vacuum dried at 60°C for 10 hours to obtain modified multi-walled carbon nanotubes.

[0041] Step 5: Preparation of thermal conductivity enhancer: Aluminum nitride powder (particle size 1 μm) and boron nitride powder (particle size 0.5 μm) are mixed at a mass ratio of 2:1, ball-milled for 1 hour, and then passed through a 200-mesh sieve to obtain a composite powder. The composite powder is dispersed in anhydrous ethanol with silane coupling agent γ-aminopropyltriethoxysilane at a mass ratio of 50:0.8, stirred at room temperature for 1 hour, then heated and stirred at 55°C for 3 hours. After filtration and washing, it is vacuum dried at 50°C for 6 hours to obtain the thermal conductivity enhancer.

[0042] Step Six: Sheath Preparation: 100 parts polypropylene resin, 20 parts EPDM rubber, 5 parts modified multi-walled carbon nanotubes, 8 parts thermal conductivity enhancer, 2 parts distearate thiopropionate, 1 part calcium stearate, and 4 parts dioctyl phthalate are mixed evenly in a high-speed mixer. The mixture is then fed into a twin-screw extruder for melt extrusion molding, extruding and coating the cable body to obtain a radiation-resistant protective cable for nuclear power plants. Twin-screw extruder temperature settings: feeding section 150℃, compression section 170℃, homogenization section 180℃, die head 190℃, screw speed 70 r / min.

[0043] Example 3

[0044] Step 1: Preparation of modified multi-walled carbon nanotubes: Multi-walled carbon nanotubes were reacted with 65wt% nitric acid solution at a mass ratio of 1:15 at room temperature for 40 min, ultrasonically treated for 3 h, filtered and washed until neutral, and vacuum dried at 60℃ for 15 h to obtain activated multi-walled carbon nanotubes.

[0045] Step 2, Boric acid modification treatment: Activated multi-walled carbon nanotubes and boric acid were dispersed in deionized water at a mass ratio of 1:1.8, and stirred at 75°C for 5 hours. After filtration and washing, intermediate 1 was obtained.

[0046] Step 3, Phosphoric acid modification: Intermediate 1 and 85wt% phosphoric acid solution were stirred at 85℃ for 4h at a mass ratio of 1:0.25, washed 3 times with acetone, and dried under vacuum at 60℃ for 10h to obtain intermediate 2.

[0047] Step 4, melamine functionalization: Intermediate 2 and melamine are dispersed in ethanol at a mass ratio of 1:3, refluxed at 95°C for 7 hours, filtered and washed, and then vacuum dried at 60°C for 15 hours to obtain modified multi-walled carbon nanotubes.

[0048] Step 5: Preparation of thermal conductivity enhancer: Aluminum nitride powder (particle size 3μm) and boron nitride powder (particle size 2μm) are mixed at a mass ratio of 4:1, ball-milled for 3 hours, and then passed through a 200-mesh sieve to obtain a composite powder. The composite powder is dispersed in anhydrous ethanol with silane coupling agent γ-aminopropyltriethoxysilane at a mass ratio of 50:1.2, stirred at room temperature for 3 hours, then heated and stirred at 65°C for 5 hours. After filtration and washing, it is vacuum dried at 50°C for 10 hours to obtain the thermal conductivity enhancer.

[0049] Step Six: Sheath Preparation: 100 parts of polypropylene resin, 40 parts of EPDM rubber, 12 parts of modified multi-walled carbon nanotubes, 15 parts of thermal conductivity enhancer, 6 parts of distearate thiopropionate, 3 parts of calcium stearate, and 8 parts of dioctyl phthalate are mixed evenly in a high-speed mixer. The mixture is then fed into a twin-screw extruder for melt extrusion molding, extruding and coating the cable body to obtain a radiation-resistant protective cable for nuclear power plants. Twin-screw extruder temperature settings: feeding section 170℃, compression section 190℃, homogenization section 200℃, die head 210℃, screw speed 90 r / min.

[0050] Example 4

[0051] Step 1: Preparation of modified multi-walled carbon nanotubes: Multi-walled carbon nanotubes were reacted with 65wt% nitric acid solution at a mass ratio of 1:11 at room temperature for 25 min, ultrasonically treated for 1.5 h, filtered and washed until neutral, and vacuum dried at 60℃ for 11 h to obtain activated multi-walled carbon nanotubes.

[0052] Step 2, Boric acid modification treatment: Activated multi-walled carbon nanotubes and boric acid were dispersed in deionized water at a mass ratio of 1:1.3, and stirred at 68°C for 3.5 h. After filtration and washing, intermediate 1 was obtained.

[0053] Step 3, Phosphoric acid modification treatment: Intermediate 1 and 85wt% phosphoric acid solution were stirred at 78℃ for 2.5h at a mass ratio of 1:0.18, washed 3 times with acetone, and dried under vacuum at 60℃ for 7h to obtain intermediate 2.

[0054] Step 4, melamine functionalization: Intermediate 2 and melamine were dispersed in ethanol at a mass ratio of 1:2.2 and refluxed at 88°C for 5.5 h. After filtration and washing, the mixture was vacuum dried at 60°C for 11 h to obtain modified multi-walled carbon nanotubes.

[0055] Step 5: Preparation of thermal conductivity enhancer: Aluminum nitride powder (particle size 1.5 μm) and boron nitride powder (particle size 0.8 μm) were mixed at a mass ratio of 2.5:1, ball-milled for 1.5 h, and then passed through a 200-mesh sieve to obtain a composite powder. The composite powder was dispersed in anhydrous ethanol with the silane coupling agent γ-aminopropyltriethoxysilane at a mass ratio of 50:0.9, stirred at room temperature for 1.5 h, then heated and stirred at 58 °C for 3.5 h, filtered and washed, and then vacuum dried at 50 °C for 7 h to obtain the thermal conductivity enhancer.

[0056] Step Six: Sheath Preparation: 100 parts polypropylene resin, 25 parts EPDM rubber, 7 parts modified multi-walled carbon nanotubes, 10 parts thermal conductivity enhancer, 3 parts distearate thiopropionate, 1.5 parts calcium stearate, and 5 parts dioctyl phthalate are mixed evenly in a high-speed mixer. The mixture is then fed into a twin-screw extruder for melt extrusion molding, extruding and coating the cable body to obtain a radiation-resistant protective cable for nuclear power plants. Twin-screw extruder temperature settings: feeding section 155℃, compression section 175℃, homogenization section 185℃, die head 195℃, screw speed 75 r / min.

[0057] Example 5

[0058] Step 1: Preparation of modified multi-walled carbon nanotubes: Multi-walled carbon nanotubes were reacted with 65wt% nitric acid solution at a mass ratio of 1:13 at room temperature for 35 min, ultrasonically treated for 2.5 h, filtered and washed until neutral, and vacuum dried at 60℃ for 13 h to obtain activated multi-walled carbon nanotubes.

[0059] Step 2, Boric acid modification treatment: Activated multi-walled carbon nanotubes and boric acid were dispersed in deionized water at a mass ratio of 1:1.6, and stirred at 72°C for 4.5 h. After filtration and washing, intermediate 1 was obtained.

[0060] Step 3, Phosphoric acid modification treatment: Intermediate 1 and 85wt% phosphoric acid solution were stirred at 82℃ for 3.5h at a mass ratio of 1:0.22, washed 3 times with acetone, and dried under vacuum at 60℃ for 9h to obtain intermediate 2.

[0061] Step 4, melamine functionalization: Intermediate 2 and melamine were dispersed in ethanol at a mass ratio of 1:2.8 and refluxed at 92°C for 6.5 h. After filtration and washing, the mixture was vacuum dried at 60°C for 13 h to obtain modified multi-walled carbon nanotubes.

[0062] Step 5: Preparation of thermal conductivity enhancer: Aluminum nitride powder (particle size 2.5 μm) and boron nitride powder (particle size 1.5 μm) were mixed at a mass ratio of 3.5:1, ball-milled for 2.5 h, and then passed through a 200-mesh sieve to obtain a composite powder. The composite powder was dispersed in anhydrous ethanol with the silane coupling agent γ-aminopropyltriethoxysilane at a mass ratio of 50:1.1, stirred at room temperature for 2.5 h, then heated and stirred at 62 °C for 4.5 h, filtered and washed, and then vacuum dried at 50 °C for 9 h to obtain the thermal conductivity enhancer.

[0063] Step Six: Sheath Preparation: 100 parts of polypropylene resin, 35 parts of EPDM rubber, 10 parts of modified multi-walled carbon nanotubes, 13 parts of thermal conductivity enhancer, 5 parts of distearate thiopropionate, 2.5 parts of calcium stearate, and 7 parts of dioctyl phthalate are mixed evenly in a high-speed mixer. The mixture is then fed into a twin-screw extruder for melt extrusion molding, extruding and coating the cable body to obtain a radiation-resistant protective cable for nuclear power plants. Twin-screw extruder temperature settings: feeding section 165℃, compression section 185℃, homogenization section 195℃, die head 205℃, screw speed 85 r / min.

[0064] Comparative Example 1: Compared with Example 1, no modification treatment was performed on the multi-walled carbon nanotubes.

[0065] Step 1: Preparation of thermal conductivity enhancer: Aluminum nitride powder (particle size 2μm) and boron nitride powder (particle size 1μm) are mixed at a mass ratio of 3:1, ball-milled for 2 hours, and then passed through a 200-mesh sieve to obtain a composite powder. The composite powder is dispersed in anhydrous ethanol with the silane coupling agent γ-aminopropyltriethoxysilane at a mass ratio of 50:1, stirred at room temperature for 2 hours, then heated and stirred at 60°C for 4 hours. After filtration and washing, it is vacuum dried at 50°C for 8 hours to obtain the thermal conductivity enhancer.

[0066] Step 2, Sheath Layer Preparation: 100 parts of polypropylene resin, 30 parts of EPDM rubber, 8 parts of multi-walled carbon nanotubes, 12 parts of thermal conductivity enhancer, 4 parts of distearate thiopropionate, 2 parts of calcium stearate, and 6 parts of dioctyl phthalate are mixed evenly in a high-speed mixer. The mixture is then fed into a twin-screw extruder for melt extrusion molding, extruding and coating the cable body to obtain a radiation-resistant protective cable for nuclear power plants. Twin-screw extruder temperature settings: feeding section 160℃, compression section 180℃, homogenization section 190℃, die head 200℃, screw speed 80 r / min.

[0067] Comparative Example 2: Compared with Example 1, the thermal conductivity enhancer was not surface modified with silane coupling agent.

[0068] Step 1: Preparation of modified multi-walled carbon nanotubes: Multi-walled carbon nanotubes were reacted with 65wt% nitric acid solution at a mass ratio of 1:12 at room temperature for 30 min, ultrasonicated for 2 h, filtered and washed until neutral, and vacuum dried at 60℃ for 12 h to obtain activated multi-walled carbon nanotubes. The activated multi-walled carbon nanotubes were dispersed with boric acid at a mass ratio of 1:1.5 in deionized water and stirred at 70℃ for 4 h. After filtration and washing, intermediate 1 was obtained. Intermediate 1 was reacted with 85wt% phosphoric acid solution at a mass ratio of 1:0.2 at 80℃ for 3 h, washed three times with acetone, and vacuum dried at 60℃ for 8 h to obtain intermediate 2. Intermediate 2 was dispersed with melamine at a mass ratio of 1:2.5 in ethanol and refluxed at 90℃ for 6 h. After filtration and washing, it was vacuum dried at 60℃ for 12 h to obtain modified multi-walled carbon nanotubes.

[0069] Step 2: Preparation of unmodified thermal conductivity enhancer: Aluminum nitride powder (particle size 2μm) and boron nitride powder (particle size 1μm) are mixed at a mass ratio of 3:1, ball-milled for 2 hours and then passed through a 200-mesh sieve to obtain the unmodified thermal conductivity enhancer.

[0070] Step 3: Sheath preparation: 100 parts of polypropylene resin, 30 parts of EPDM rubber, 8 parts of modified multi-walled carbon nanotubes, 12 parts of unmodified thermal conductivity enhancer, 4 parts of distearate thiopropionate, 2 parts of calcium stearate, and 6 parts of dioctyl phthalate are mixed evenly in a high-speed mixer. The mixture is then fed into a twin-screw extruder for melt extrusion molding, extruding and coating the cable body to obtain a radiation-resistant protective cable for nuclear power plants. Twin-screw extruder temperature settings: feeding section 160℃, compression section 180℃, homogenization section 190℃, die head 200℃, screw speed 80 r / min.

[0071] Comparative Example 3: Compared with Example 1, the amount of EPDM rubber used was excessive.

[0072] Step 1: Preparation of modified multi-walled carbon nanotubes: Multi-walled carbon nanotubes were reacted with 65wt% nitric acid solution at a mass ratio of 1:12 at room temperature for 30 min, ultrasonicated for 2 h, filtered and washed until neutral, and vacuum dried at 60℃ for 12 h to obtain activated multi-walled carbon nanotubes. The activated multi-walled carbon nanotubes were dispersed with boric acid at a mass ratio of 1:1.5 in deionized water and stirred at 70℃ for 4 h. After filtration and washing, intermediate 1 was obtained. Intermediate 1 was reacted with 85wt% phosphoric acid solution at a mass ratio of 1:0.2 at 80℃ for 3 h, washed three times with acetone, and vacuum dried at 60℃ for 8 h to obtain intermediate 2. Intermediate 2 was dispersed with melamine at a mass ratio of 1:2.5 in ethanol and refluxed at 90℃ for 6 h. After filtration and washing, it was vacuum dried at 60℃ for 12 h to obtain modified multi-walled carbon nanotubes.

[0073] Step 2: Preparation of thermal conductivity enhancer: Aluminum nitride powder (particle size 2μm) and boron nitride powder (particle size 1μm) are mixed at a mass ratio of 3:1, ball-milled for 2 hours, and then passed through a 200-mesh sieve to obtain a composite powder. The composite powder is dispersed in anhydrous ethanol with the silane coupling agent γ-aminopropyltriethoxysilane at a mass ratio of 50:1, stirred at room temperature for 2 hours, then heated and stirred at 60°C for 4 hours. After filtration and washing, it is vacuum dried at 50°C for 8 hours to obtain the thermal conductivity enhancer.

[0074] Step 3: Sheath preparation: 100 parts of polypropylene resin, 50 parts of EPDM rubber, 8 parts of modified multi-walled carbon nanotubes, 12 parts of thermal conductivity enhancer, 4 parts of distearate thiopropionate, 2 parts of calcium stearate, and 6 parts of dioctyl phthalate are mixed evenly in a high-speed mixer. The mixture is then fed into a twin-screw extruder for melt extrusion molding, extruding and coating the cable body to obtain a radiation-resistant protective cable for nuclear power plants. Twin-screw extruder temperature settings: feeding section 160℃, compression section 180℃, homogenization section 190℃, die head 200℃, screw speed 80 r / min.

[0075] Comparative Example 4: Compared with Example 1, the amount of modified multi-walled carbon nanotubes used was too small.

[0076] Step 1: Preparation of modified multi-walled carbon nanotubes: Multi-walled carbon nanotubes were reacted with 65wt% nitric acid solution at a mass ratio of 1:12 at room temperature for 30 min, ultrasonicated for 2 h, filtered and washed until neutral, and vacuum dried at 60℃ for 12 h to obtain activated multi-walled carbon nanotubes. The activated multi-walled carbon nanotubes were dispersed with boric acid at a mass ratio of 1:1.5 in deionized water and stirred at 70℃ for 4 h. After filtration and washing, intermediate 1 was obtained. Intermediate 1 was reacted with 85wt% phosphoric acid solution at a mass ratio of 1:0.2 at 80℃ for 3 h, washed three times with acetone, and vacuum dried at 60℃ for 8 h to obtain intermediate 2. Intermediate 2 was dispersed with melamine at a mass ratio of 1:2.5 in ethanol and refluxed at 90℃ for 6 h. After filtration and washing, it was vacuum dried at 60℃ for 12 h to obtain modified multi-walled carbon nanotubes.

[0077] Step 2: Preparation of thermal conductivity enhancer: Aluminum nitride powder (particle size 2μm) and boron nitride powder (particle size 1μm) are mixed at a mass ratio of 3:1, ball-milled for 2 hours, and then passed through a 200-mesh sieve to obtain a composite powder. The composite powder is dispersed in anhydrous ethanol with the silane coupling agent γ-aminopropyltriethoxysilane at a mass ratio of 50:1, stirred at room temperature for 2 hours, then heated and stirred at 60°C for 4 hours. After filtration and washing, it is vacuum dried at 50°C for 8 hours to obtain the thermal conductivity enhancer.

[0078] Step 3: Sheath preparation: 100 parts of polypropylene resin, 30 parts of EPDM rubber, 3 parts of modified multi-walled carbon nanotubes, 12 parts of thermal conductivity enhancer, 4 parts of distearate thiopropionate, 2 parts of calcium stearate, and 6 parts of dioctyl phthalate are mixed evenly in a high-speed mixer. The mixture is then fed into a twin-screw extruder for melt extrusion molding, extruding and coating the cable body to obtain a radiation-resistant protective cable for nuclear power plants. Twin-screw extruder temperature settings: feeding section 160℃, compression section 180℃, homogenization section 190℃, die head 200℃, screw speed 80 r / min.

[0079] Comparative Example 5: Compared with Example 1, the amount of thermal conductivity enhancer used was excessive.

[0080] Step 1: Preparation of modified multi-walled carbon nanotubes: Multi-walled carbon nanotubes were reacted with 65wt% nitric acid solution at a mass ratio of 1:12 at room temperature for 30 min, ultrasonicated for 2 h, filtered and washed until neutral, and vacuum dried at 60℃ for 12 h to obtain activated multi-walled carbon nanotubes. The activated multi-walled carbon nanotubes were dispersed with boric acid at a mass ratio of 1:1.5 in deionized water and stirred at 70℃ for 4 h. After filtration and washing, intermediate 1 was obtained. Intermediate 1 was reacted with 85wt% phosphoric acid solution at a mass ratio of 1:0.2 at 80℃ for 3 h, washed three times with acetone, and vacuum dried at 60℃ for 8 h to obtain intermediate 2. Intermediate 2 was dispersed with melamine at a mass ratio of 1:2.5 in ethanol and refluxed at 90℃ for 6 h. After filtration and washing, it was vacuum dried at 60℃ for 12 h to obtain modified multi-walled carbon nanotubes.

[0081] Step 2: Preparation of thermal conductivity enhancer: Aluminum nitride powder (particle size 2μm) and boron nitride powder (particle size 1μm) are mixed at a mass ratio of 3:1, ball-milled for 2 hours, and then passed through a 200-mesh sieve to obtain a composite powder. The composite powder is dispersed in anhydrous ethanol with the silane coupling agent γ-aminopropyltriethoxysilane at a mass ratio of 50:1, stirred at room temperature for 2 hours, then heated and stirred at 60°C for 4 hours. After filtration and washing, it is vacuum dried at 50°C for 8 hours to obtain the thermal conductivity enhancer.

[0082] Step 3: Sheath preparation: 100 parts of polypropylene resin, 30 parts of EPDM rubber, 8 parts of modified multi-walled carbon nanotubes, 18 parts of thermal conductivity enhancer, 4 parts of distearate thiopropionate, 2 parts of calcium stearate, and 6 parts of dioctyl phthalate are mixed evenly in a high-speed mixer. The mixture is then fed into a twin-screw extruder for melt extrusion molding, extruding and coating the cable body to obtain a radiation-resistant protective cable for nuclear power plants. Twin-screw extruder temperature settings: feeding section 160℃, compression section 180℃, homogenization section 190℃, die head 200℃, screw speed 80 r / min.

[0083] Comparative Example 6: Compared with Example 1, the aluminum nitride content in the thermal conductivity enhancer used was too low.

[0084] Step 1: Preparation of modified multi-walled carbon nanotubes: Multi-walled carbon nanotubes were reacted with 65wt% nitric acid solution at a mass ratio of 1:12 at room temperature for 30 min, ultrasonicated for 2 h, filtered and washed until neutral, and vacuum dried at 60℃ for 12 h to obtain activated multi-walled carbon nanotubes. The activated multi-walled carbon nanotubes were dispersed with boric acid at a mass ratio of 1:1.5 in deionized water and stirred at 70℃ for 4 h. After filtration and washing, intermediate 1 was obtained. Intermediate 1 was reacted with 85wt% phosphoric acid solution at a mass ratio of 1:0.2 at 80℃ for 3 h, washed three times with acetone, and vacuum dried at 60℃ for 8 h to obtain intermediate 2. Intermediate 2 was dispersed with melamine at a mass ratio of 1:2.5 in ethanol and refluxed at 90℃ for 6 h. After filtration and washing, it was vacuum dried at 60℃ for 12 h to obtain modified multi-walled carbon nanotubes.

[0085] Step 2: Preparation of thermal conductivity enhancer: Aluminum nitride powder (particle size 2μm) and boron nitride powder (particle size 1μm) are mixed at a mass ratio of 1:1, ball-milled for 2 hours, and then passed through a 200-mesh sieve to obtain a composite powder. The composite powder is dispersed in anhydrous ethanol with the silane coupling agent γ-aminopropyltriethoxysilane at a mass ratio of 50:1, stirred at room temperature for 2 hours, then heated and stirred at 60°C for 4 hours. After filtration and washing, it is vacuum dried at 50°C for 8 hours to obtain the thermal conductivity enhancer.

[0086] Step 3: Sheath preparation: 100 parts of polypropylene resin, 30 parts of EPDM rubber, 8 parts of modified multi-walled carbon nanotubes, 12 parts of thermal conductivity enhancer, 4 parts of distearate thiopropionate, 2 parts of calcium stearate, and 6 parts of dioctyl phthalate are mixed evenly in a high-speed mixer. The mixture is then fed into a twin-screw extruder for melt extrusion molding, extruding and coating the cable body to obtain a radiation-resistant protective cable for nuclear power plants. Twin-screw extruder temperature settings: feeding section 160℃, compression section 180℃, homogenization section 190℃, die head 200℃, screw speed 80 r / min.

[0087] Comparative Example 7: Compared with Example 1, the preparation of modified multi-walled carbon nanotubes lacked the modification treatment of multi-walled carbon nanotubes using melamine.

[0088] Step 1: Preparation of modified multi-walled carbon nanotubes: Multi-walled carbon nanotubes were reacted with 65wt% nitric acid solution at a mass ratio of 1:12 at room temperature for 30 min, ultrasonicated for 2 h, filtered and washed until neutral, and vacuum dried at 60℃ for 12 h to obtain activated multi-walled carbon nanotubes. The activated multi-walled carbon nanotubes were dispersed with boric acid at a mass ratio of 1:1.5 in deionized water and stirred at 70℃ for 4 h. After filtration and washing, intermediate 1 was obtained. Intermediate 1 was reacted with 85wt% phosphoric acid solution at a mass ratio of 1:0.2 at 80℃ for 3 h, washed three times with acetone, and vacuum dried at 60℃ for 8 h to obtain modified multi-walled carbon nanotubes.

[0089] Step 2: Preparation of thermal conductivity enhancer: Aluminum nitride powder (particle size 2μm) and boron nitride powder (particle size 1μm) are mixed at a mass ratio of 3:1, ball-milled for 2 hours, and then passed through a 200-mesh sieve to obtain a composite powder. The composite powder is dispersed in anhydrous ethanol with the silane coupling agent γ-aminopropyltriethoxysilane at a mass ratio of 50:1, stirred at room temperature for 2 hours, then heated and stirred at 60°C for 4 hours. After filtration and washing, it is vacuum dried at 50°C for 8 hours to obtain the thermal conductivity enhancer.

[0090] Step 3: Sheath preparation: 100 parts of polypropylene resin, 30 parts of EPDM rubber, 8 parts of modified multi-walled carbon nanotubes, 12 parts of thermal conductivity enhancer, 4 parts of distearate thiopropionate, 2 parts of calcium stearate, and 6 parts of dioctyl phthalate are mixed evenly in a high-speed mixer. The mixture is then fed into a twin-screw extruder for melt extrusion molding, extruding and coating the cable body to obtain a radiation-resistant protective cable for nuclear power plants. Twin-screw extruder temperature settings: feeding section 160℃, compression section 180℃, homogenization section 190℃, die head 200℃, screw speed 80 r / min.

[0091] Comparative Example 8: The extrusion temperature was too high compared to Example 1.

[0092] Step 1: Preparation of modified multi-walled carbon nanotubes: Multi-walled carbon nanotubes were reacted with 65wt% nitric acid solution at a mass ratio of 1:12 at room temperature for 30 min, ultrasonicated for 2 h, filtered and washed until neutral, and vacuum dried at 60℃ for 12 h to obtain activated multi-walled carbon nanotubes. The activated multi-walled carbon nanotubes were dispersed with boric acid at a mass ratio of 1:1.5 in deionized water and stirred at 70℃ for 4 h. After filtration and washing, intermediate 1 was obtained. Intermediate 1 was reacted with 85wt% phosphoric acid solution at a mass ratio of 1:0.2 at 80℃ for 3 h, washed three times with acetone, and vacuum dried at 60℃ for 8 h to obtain intermediate 2. Intermediate 2 was dispersed with melamine at a mass ratio of 1:2.5 in ethanol and refluxed at 90℃ for 6 h. After filtration and washing, it was vacuum dried at 60℃ for 12 h to obtain modified multi-walled carbon nanotubes.

[0093] Step 2: Preparation of thermal conductivity enhancer: Aluminum nitride powder (particle size 2μm) and boron nitride powder (particle size 1μm) are mixed at a mass ratio of 3:1, ball-milled for 2 hours, and then passed through a 200-mesh sieve to obtain a composite powder. The composite powder is dispersed in anhydrous ethanol with the silane coupling agent γ-aminopropyltriethoxysilane at a mass ratio of 50:1, stirred at room temperature for 2 hours, then heated and stirred at 60°C for 4 hours. After filtration and washing, it is vacuum dried at 50°C for 8 hours to obtain the thermal conductivity enhancer.

[0094] Step 3: Sheath preparation: 100 parts of polypropylene resin, 30 parts of EPDM rubber, 8 parts of modified multi-walled carbon nanotubes, 12 parts of thermal conductivity enhancer, 4 parts of distearate thiopropionate, 2 parts of calcium stearate, and 6 parts of dioctyl phthalate are mixed evenly in a high-speed mixer. The mixture is then fed into a twin-screw extruder for melt extrusion molding, extruding and coating the cable body to obtain a radiation-resistant protective cable for nuclear power plants. Twin-screw extruder temperature settings: feeding section 140℃, compression section 160℃, homogenization section 170℃, die head 180℃, screw speed 60 r / min.

[0095] Comparative Example 9: Compared with Example 1, the preparation of modified multi-walled carbon nanotubes lacked the use of boric acid to modify the multi-walled carbon nanotubes.

[0096] Step 1: Preparation of modified multi-walled carbon nanotubes: Multi-walled carbon nanotubes were reacted with 65wt% nitric acid solution at a mass ratio of 1:12 at room temperature for 30 min, ultrasonicated for 2 h, filtered and washed until neutral, and vacuum dried at 60℃ for 12 h to obtain activated multi-walled carbon nanotubes. The activated multi-walled carbon nanotubes were reacted with 85wt% phosphoric acid solution at a mass ratio of 1:0.2 at 80℃ for 3 h, washed three times with acetone, and vacuum dried at 60℃ for 8 h to obtain intermediate 2. Intermediate 2 was dispersed with melamine at a mass ratio of 1:2.5 in ethanol and refluxed at 90℃ for 6 h. After filtration and washing, it was vacuum dried at 60℃ for 12 h to obtain modified multi-walled carbon nanotubes.

[0097] Step 2: Preparation of thermal conductivity enhancer: Aluminum nitride powder (particle size 2μm) and boron nitride powder (particle size 1μm) are mixed at a mass ratio of 3:1, ball-milled for 2 hours, and then passed through a 200-mesh sieve to obtain a composite powder. The composite powder is dispersed in anhydrous ethanol with the silane coupling agent γ-aminopropyltriethoxysilane at a mass ratio of 50:1, stirred at room temperature for 2 hours, then heated and stirred at 60°C for 4 hours. After filtration and washing, it is vacuum dried at 50°C for 8 hours to obtain the thermal conductivity enhancer.

[0098] Step 3: Sheath preparation: 100 parts of polypropylene resin, 30 parts of EPDM rubber, 8 parts of modified multi-walled carbon nanotubes, 12 parts of thermal conductivity enhancer, 4 parts of distearate thiopropionate, 2 parts of calcium stearate, and 6 parts of dioctyl phthalate are mixed evenly in a high-speed mixer. The mixture is then fed into a twin-screw extruder for melt extrusion molding, extruding and coating the cable body to obtain a radiation-resistant protective cable for nuclear power plants. Twin-screw extruder temperature settings: feeding section 160℃, compression section 180℃, homogenization section 190℃, die head 200℃, screw speed 80 r / min.

[0099] Comparative Example 10: Compared with Example 1, phosphoric acid was not used to modify the multi-walled carbon nanotubes during the preparation of the modified multi-walled carbon nanotubes.

[0100] Step 1: Preparation of modified multi-walled carbon nanotubes: Multi-walled carbon nanotubes were reacted with 65wt% nitric acid solution at a mass ratio of 1:12 at room temperature for 30 min, ultrasonicated for 2 h, filtered and washed until neutral, and vacuum dried at 60℃ for 12 h to obtain activated multi-walled carbon nanotubes. The activated multi-walled carbon nanotubes were dispersed with boric acid at a mass ratio of 1:1.5 in deionized water and stirred at 70℃ for 4 h. After filtration and washing, intermediate 1 was obtained. Intermediate 1 was dispersed with melamine at a mass ratio of 1:2.5 in ethanol and refluxed at 90℃ for 6 h. After filtration and washing, it was vacuum dried at 60℃ for 12 h to obtain modified multi-walled carbon nanotubes.

[0101] Step 2: Preparation of thermal conductivity enhancer: Aluminum nitride powder (particle size 2μm) and boron nitride powder (particle size 1μm) are mixed at a mass ratio of 3:1, ball-milled for 2 hours, and then passed through a 200-mesh sieve to obtain a composite powder. The composite powder is dispersed in anhydrous ethanol with the silane coupling agent γ-aminopropyltriethoxysilane at a mass ratio of 50:1, stirred at room temperature for 2 hours, then heated and stirred at 60°C for 4 hours. After filtration and washing, it is vacuum dried at 50°C for 8 hours to obtain the thermal conductivity enhancer.

[0102] Step 3: Sheath preparation: 100 parts of polypropylene resin, 30 parts of EPDM rubber, 8 parts of modified multi-walled carbon nanotubes, 12 parts of thermal conductivity enhancer, 4 parts of distearate thiopropionate, 2 parts of calcium stearate, and 6 parts of dioctyl phthalate are mixed evenly in a high-speed mixer. The mixture is then fed into a twin-screw extruder for melt extrusion molding, extruding and coating the cable body to obtain a radiation-resistant protective cable for nuclear power plants. Twin-screw extruder temperature settings: feeding section 160℃, compression section 180℃, homogenization section 190℃, die head 200℃, screw speed 80 r / min.

[0103] Performance testing was conducted on the radiation-resistant protective cables for nuclear power plants prepared in Examples 1-5 and Comparative Examples 1-10.

[0104] 1. Thermal conductivity test:

[0105] Step 1: Prepare circular samples of the sheath material with a diameter of 25 mm and a thickness of 2 mm, and prepare 5 parallel samples for each group.

[0106] Step 2: Place the sample on the test platform of the laser thermal conductivity meter, ensuring that the sample is in full contact with the probe.

[0107] Step 3: Set the laser power to 0.1W and the pulse time to 1s, and record the temperature change curve.

[0108] Step 4: Calculate the thermal conductivity based on the temperature change curve and take the average value of 5 samples.

[0109] 2. Radiation resistance test:

[0110] Step 1: Prepare dumbbell-shaped tensile specimens from the sheath material, according to standard GB / T 1040.2-2022.

[0111] Step 2: Place the sample in a 60Co γ-ray irradiation device and irradiate it at room temperature. The irradiation dose rate is 10 kGy / h, and the total dose is 1000 kGy.

[0112] Step 3: After irradiation, place the product in a standard environment for 24 hours and then perform mechanical property testing.

[0113] Step 4: Test the tensile strength and elongation at break according to GB / T 1040.2-2022 standard and compare them with the unirradiated sample.

[0114] 3. Thermal stability test:

[0115] Step 1: Take 5-10 mg of sample and place it in an aluminum crucible.

[0116] Step 2: Under nitrogen protection, heat the material from room temperature to 600°C at a heating rate of 10°C / min, and use a thermogravimetric analyzer (TGA) to determine the thermal decomposition temperature and mass loss of the material.

[0117] Step 3: Record the mass loss curve and determine the 5% mass loss temperature (T5%) and the 50% mass loss temperature (T50%).

[0118] 4. Electrical insulation performance test:

[0119] Step 1: Prepare a circular sample of the sheath material with a diameter of 100 mm and a thickness of 1 mm. Step 2: Test the sample after conditioning in a standard environment for 48 hours.

[0120] Step 3: Apply a 500V DC voltage for 1 minute and record the resistance value.

[0121] Step 4: Calculate the volume resistivity according to the sample size in accordance with GB / T1408.1-2016 standard.

[0122] Test Result Data Table

[0123] Table 1. Thermal conductivity test results

[0124] sample Thermal conductivity (W / m·K) Example 1 1.85 Example 2 1.72 Example 3 1.92 Example 4 1.78 Example 5 1.88 Comparative Example 1 1.23 Comparative Example 2 1.41 Comparative Example 3 1.58 Comparative Example 4 1.35 Comparative Example 5 1.62 Comparative Example 6 1.48 Comparative Example 7 1.52 Comparative Example 8 1.33 Comparative Example 9 1.46 Comparative Example 10 1.49

[0125] Table 2. Radiation resistance test results

[0126]

[0127] Table 3. Thermal stability test results

[0128]

[0129]

[0130] Table 4. Electrical insulation performance test results

[0131]

[0132]

[0133] Data Analysis

[0134] As shown in Table 1, the thermal conductivity of Example 1 reached 1.85 W / m·K. Example 3, due to the higher dosage of modified multi-walled carbon nanotubes and thermal conductivity enhancers, achieved a thermal conductivity of 1.92 W / m·K, which is higher than Example 1. Comparative Example 1, without multi-walled carbon nanotube modification, had a thermal conductivity of only 1.23 W / m·K, which is lower than Example 1. This indicates that multi-walled carbon nanotube modification can improve the thermal conductivity of the cable. Comparative Example 2, due to the lack of surface modification of the thermal conductivity enhancer, had poor compatibility with the matrix, resulting in a lower thermal conductivity. Comparative Example 4, due to insufficient dosage of modified multi-walled carbon nanotubes and an imperfect thermal conductivity pathway, also had a lower thermal conductivity. This demonstrates that the modified multi-walled carbon nanotubes and surface-modified thermal conductivity enhancers of this invention synergistically improve the thermal conductivity of the cable.

[0135] As shown in Table 2, Example 1 exhibited excellent radiation resistance, maintaining a tensile strength retention rate of 87.0% and an elongation at break retention rate of 82.1% after irradiation with 1000 kGy. Example 3, due to its higher content of modified multi-walled carbon nanotubes, formed a more complete radiation-resistant network structure, and its strength retention rate also reached 87.0%. Comparative Example 1, using unmodified carbon nanotubes, could not effectively capture radiation-generated free radicals, resulting in a lower strength retention rate compared to Example 1. Comparative Example 7, lacking melamine functionalization, had insufficient active groups on the carbon nanotube surface, leading to decreased radiation resistance and a lower strength retention rate. Comparative Example 8, due to its excessively low extrusion temperature, had an insufficiently dense material structure, resulting in more severe radiation damage and a significant decrease in strength retention rate.

[0136] As shown in Table 3, Example 1 exhibits a 5% mass loss temperature (T5%) of 385℃, a 50% mass loss temperature (T50%) of 465℃, and a mass residue rate of 18.5% at 600℃, demonstrating good thermal stability. Example 3, containing more inorganic fillers, shows a slightly improved thermal stability, with a T5% reaching 388℃. Comparative Example 1, lacking modification treatment, suffers from poor material structural stability, with a T5% of only 345℃, 40℃ lower than Example 1. Comparative Example 8, due to improper processing temperature, exhibits numerous internal structural defects, resulting in the worst thermal stability, with a T5% of only 342℃. Comparative Example 4, with insufficient modified carbon nanotube content, fails to effectively improve the material's thermal stability, achieving a T5% of 351℃.

[0137] As can be seen from Table 4, the volume resistivity of Example 1 reaches 2.8 × 10⁻⁶. 15 With a resistivity of Ω·cm, it exhibits excellent electrical insulation properties. In Example 3, due to thorough modification treatment, the resistivity reaches 2.9 × 10⁻⁶. 15 The resistivity of Comparative Example 1 was 3.6% higher than that of Example 1 due to the poor dispersion of unmodified carbon nanotubes, which formed conductive pathways. 15 The resistivity was Ω·cm, a decrease of 35.7% compared to Example 1; Comparative Example 8, due to improper processing conditions, had an increase in internal defects and the lowest resistivity, only 1.7 × 10⁻⁶. 15 The resistivity of Comparative Example 4 was 39.3% lower than that of Example 1, due to insufficient modified carbon nanotube content. Although the formation of conductive pathways was avoided, the overall performance balance was poor, with a resistivity of 1.9 × 10⁻⁶. 15 Ω·cm.

[0138] In summary, this invention significantly improves the thermal conductivity, radiation resistance, and thermal stability of cables while maintaining excellent electrical insulation performance through the synergistic effect of modified multi-walled carbon nanotubes and surface-modified thermal conductivity enhancers.

[0139] Although embodiments of the present invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principles and spirit of the present invention. All equivalent changes and improvements made within the scope of the present invention should still fall within the patent coverage of the present invention.

Claims

1. A radiation-resistant protective cable for nuclear power plants, characterized in that, It includes a cable body and a sheath layer, the sheath layer comprising the following components by parts by weight: 100 parts polypropylene resin, 20-40 parts EPDM rubber, 5-12 parts modified multi-walled carbon nanotubes, 8-15 parts thermal conductivity enhancer, 2-6 parts antioxidant, 1-3 parts heat stabilizer, and 4-8 parts plasticizer. The thermal conductivity enhancer is prepared by surface modification of a composite powder of aluminum nitride and boron nitride with a silane coupling agent.

2. The radiation-resistant cable for nuclear power plants according to claim 1, characterized in that, The method for preparing the modified multi-walled carbon nanotubes includes the following steps: Step 1: Mix multi-walled carbon nanotubes with nitric acid solution at a mass ratio of 1:10-15 and stir at room temperature for 20-40 min. After sonication for 1-3 h, filter and wash until neutral. Dry under vacuum at 60 °C for 10-15 h to obtain activated multi-walled carbon nanotubes. Step 2: Disperse activated multi-walled carbon nanotubes and boric acid in deionized water at a mass ratio of 1:1.2-1.8, stir and react at 65-75℃ for 3-5 hours, filter and wash to obtain intermediate 1; Step 3: Mix intermediate 1 with phosphoric acid solution at a mass ratio of 1:0.15-0.25 and stir at 75-85℃ for 2-4 hours. Wash with acetone 3 times and dry under vacuum at 60℃ for 6-10 hours to obtain intermediate 2. Step 4: Disperse intermediate 2 and melamine in ethanol at a mass ratio of 1:2-3, reflux at 85-95℃ for 5-7 hours, filter and wash, and vacuum dry at 60℃ for 10-15 hours to obtain modified multi-walled carbon nanotubes.

3. The radiation-resistant protective cable for nuclear power plants according to claim 2, characterized in that, The mass ratio of the multi-walled carbon nanotubes to the nitric acid solution is 1:10-15.

4. The radiation-resistant cable for nuclear power plants according to claim 2, characterized in that, The concentration of the nitric acid solution is 65 wt%.

5. The radiation-resistant protective cable for nuclear power plants according to claim 2, characterized in that, The concentration of the phosphoric acid solution is 85 wt%.

6. The radiation-resistant protective cable for nuclear power plants according to claim 1, characterized in that, The preparation method of the thermal conductivity enhancer includes the following steps: Aluminum nitride powder and boron nitride powder were mixed at a mass ratio of 2:1 to 4:1, ball-milled for 1 to 3 hours, and then passed through a 200-mesh sieve to obtain a composite powder. The composite powder was then dispersed in anhydrous ethanol with the silane coupling agent γ-aminopropyltriethoxysilane at a mass ratio of 50:0.8 to 1.

2. The mixture was stirred at room temperature for 1 to 3 hours, then heated and stirred at 55 to 65°C for 3 to 5 hours. After filtration and washing, the mixture was vacuum dried at 50°C for 6 to 10 hours to obtain a thermal conductivity enhancer.

7. The radiation-resistant protective cable for nuclear power plants according to claim 1, characterized in that, The aluminum nitride powder has a particle size of 1–3 μm, and the boron nitride powder has a particle size of 0.5–2 μm.

8. The radiation-resistant cable for nuclear power plants according to claim 1, characterized in that, The antioxidant is distearate, the heat stabilizer is calcium stearate, and the plasticizer is dioctyl phthalate.

9. A method for preparing the radiation-resistant protective cable for nuclear power plants according to claims 1-8, characterized in that, Includes the following steps: Polypropylene resin, EPDM rubber, antioxidant, heat stabilizer, plasticizer, modified multi-walled carbon nanotubes, and thermal conductivity enhancer are mixed evenly in a high-speed mixer, fed into a twin-screw extruder for melt extrusion molding, and extruded onto the cable body to obtain a radiation-resistant protective cable for nuclear power plants.

10. The preparation method according to claim 9, characterized in that, The temperature range of the twin-screw extruder is set as follows: feeding section 150-170℃, compression section 170-190℃, homogenization section 180-200℃, die head 190-210℃, and screw speed 70-90 r / min.

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