Rail transit vehicle irradiation cross-linking control cable and preparation process thereof

Abstract

The application discloses a kind of irradiation crosslinking control cables for rail transit vehicles and preparation process thereof, and relates to the field of cable.The application is designed by the "sheet-ball" synergistic modification system of nano layered double hydroxide and nano zirconium carbide, and the matching optimization of irradiation crosslinking process is matched, which breaks through the technical bottleneck that multiple core performances of existing irradiation crosslinking control cables for rail transit vehicles are difficult to consider, and realizes the synergistic improvement of high wear resistance, high oil resistance, high flame retardant low smoke and excellent mechanical properties, which can be fully adapted to the complex and severe service conditions of rail transit vehicles.

Description

Technical Field

[0001] This invention relates to the field of cables, and more specifically to an irradiated cross-linked control cable for rail transit vehicles and its manufacturing process. Background Technology

[0002] With the rapid development of my country's rail transit industry, the requirements for operating speed, carrying density, and service reliability of rail transit vehicles such as high-speed rail, subway, and urban rail are constantly increasing. As the core transmission component of the vehicle's electrical control system, the performance of control cables directly determines the safety and stability of vehicle operation. Rail transit vehicle control cables operate in the complex and harsh working environment inside the locomotive cabin for extended periods. They must withstand mechanical scratches during installation and wiring, continuous friction caused by high-frequency vibrations of the vehicle body during operation, and long-term corrosion from high-temperature oil contaminants inside the cabin. Furthermore, they must meet the mandatory safety and environmental protection requirements for halogen-free, low-smoke, and highly flame-retardant materials in standards such as TB / T1484 "Locomotive and Rolling Stock Cables" and GB / T19666 "General Rules for Flame-Retardant and Fire-Resistant Wires and Cables".

[0003] Irradiated cross-linked polyolefin materials have become the mainstream matrix material for control cables used in rail transit vehicles due to their excellent temperature resistance, mechanical properties, environmental friendliness, and processing performance. However, current technologies for irradiated cross-linked control cables used in rail transit vehicles still have several insurmountable technical shortcomings, failing to fully meet the stringent performance requirements of the rapidly developing industry. These are as follows: Firstly, the wear and scratch resistance is insufficient, failing to meet the requirements for long-term stable service. During the operation of rail transit vehicles, cables inevitably suffer from hard scratches during installation and continuous reciprocating friction caused by vehicle vibration during operation. Conventional irradiated cross-linked polyolefin formulations have a high coefficient of friction and poor wear resistance, making them prone to sheath wear and cracking during long-term service, which can lead to insulation failure, short circuits, and other safety accidents. Existing single wear-resistant filler modification schemes often have the problem of difficulty in balancing hardness improvement and toughness maintenance, and the improvement in wear resistance is limited, failing to meet the wear resistance requirements for long-term stable operation of rail transit vehicles.

[0004] Secondly, its poor high-temperature oil resistance makes it unsuitable for the oily conditions of locomotives. Rail transit vehicles contain large amounts of lubricating oil, hydraulic oil, diesel fuel, and other oily media. Cables are constantly immersed in this high-temperature oily environment. Conventional polyolefin materials, especially those with high-filler flame-retardant systems, have poor interfacial bonding between the filler and the polymer matrix, making them prone to oil penetration, material swelling, and significant degradation of mechanical properties. This fails to meet the stringent high-temperature oil resistance requirements of rail transit vehicle cable standards, drastically shortening the cable's service life.

[0005] Third, achieving both high flame retardancy and excellent mechanical properties is a common pain point in the industry. The rail transit sector has mandatory requirements for halogen-free, low-smoke, and high flame retardancy in vehicle cables, necessitating the addition of large amounts of inorganic flame-retardant fillers to the polymer matrix. However, high filler content disrupts the structural continuity of the polymer matrix, leading to a significant decrease in tensile strength and elongation at break, and a substantial increase in brittleness. This makes the material prone to cracking and failure under bending and long-term vibration conditions, creating a common industry problem of "improved flame retardancy performance - deteriorated mechanical properties." Existing technologies struggle to achieve a balance between these two aspects.

[0006] Fourth, the overall performance cannot be synergistically improved. Existing modification solutions mostly optimize a single performance weakness, often leading to the deterioration of other core performances while improving one performance aspect. They cannot simultaneously meet the multiple stringent requirements of rail transit vehicle control cables for high wear resistance, high oil resistance, high flame retardancy, low smoke, and excellent mechanical properties, making it difficult to adapt to the performance needs of high-quality development in the rail transit industry. Summary of the Invention

[0007] To address the aforementioned shortcomings of existing technologies, this invention provides an irradiated cross-linked control cable for rail transit vehicles and its manufacturing process. Through the synergistic design of the formulation system and the matching optimization of the irradiated cross-linking process, the performance bottlenecks of existing technologies are overcome, achieving simultaneous improvements in multiple core cable performance characteristics and fully adapting to the demanding service conditions of rail transit vehicles.

[0008] To achieve the above-mentioned objectives, the technical solution adopted by this invention is as follows: A radiation cross-linked control cable for rail transit vehicles is provided, which comprises, from the inside out, a conductor, an insulation layer and a sheath layer; the insulation layer is obtained by mixing and blending a base resin, a flame retardant system and processing aids, extruding and granulating the resulting insulation layer particles, and then extruding them again. The sheath layer is obtained by mixing and kneading a base resin, modified nanoparticles, flame retardant system and processing aids, extruding and granulating to obtain sheath layer particles, and then extruding and radiation crosslinking treatment. The modified nanopowder is obtained by mixing magnesium aluminum hydrotalcite and nano zirconium carbide, and then coating it with a surface treatment agent; the surface treatment agent is an aluminum zirconium coupling agent or a titanate coupling agent.

[0009] The present invention also provides a manufacturing process for the above-mentioned irradiated cross-linked control cable for rail transit vehicles, comprising the following specific steps: S1: Weigh magnesium aluminum hydrotalcite and nano zirconium carbide and mix them evenly. After uniform mixing, under high-speed mixing, dilute the surface treatment agent with anhydrous ethanol and spray it onto the surface of the mixed powder. The mass ratio of the mixed powder to the surface treatment agent is 20:1~3. Then, treat it at a temperature of 80~100℃ for 15~25 minutes to obtain modified nano powder. S2: Add 15-35 parts of modified nanoparticles, 30-50 parts of linear low-density polyethylene, 30-40 parts of ethylene-vinyl acetate copolymer, 10-20 parts of ultra-high molecular weight polysiloxane, 60-90 parts of modified magnesium hydroxide, 20-30 parts of aluminum hypophosphite, 1.5-3 parts of antioxidant, and 1-2 parts of lubricant to a mixer and mix at 110-130℃ for 10-20 minutes. Then add 2-5 parts of triallyl isocyanurate and 1-3 parts of trimethylolpropane trimethacrylate and continue mixing for 3-5 minutes. Granulate the mixed material through a twin-screw extruder, controlling the extrusion temperature at 140-170℃ to obtain sheath layer granules. S3: Add 40-60 parts of linear low-density polyethylene, 20-40 parts of ethylene-vinyl acetate copolymer, 80-120 parts of modified magnesium hydroxide, 20-30 parts of aluminum hypophosphite, 1.5-3 parts of antioxidant, and 1-2 parts of lubricant to a mixer and mix at 110-130℃ for 10-20 minutes. Then add 2-5 parts of triallyl isocyanurate and 1-3 parts of trimethylolpropane trimethacrylate and continue mixing for 3-5 minutes. Granulate the mixed material through a twin-screw extruder, controlling the extrusion temperature at 140-170℃ to obtain insulating layer granules. S4: The insulating granules are coated onto the conductor core using an extruder. The extrusion temperature is controlled at 150~180℃ and the extrusion speed is 15~30m / min to form the insulating layer. S5: The sheathing layer granules are coated on the outside of the insulation layer through an extruder. The extrusion temperature is controlled at 150~180℃ and the extrusion speed is 15~30m / min to form the sheathing layer. S6: The extruded cable is cross-linked by irradiation using an electron accelerator; during irradiation cross-linking, the absorbed dose is 80~150kGy and the dose rate is ≤20kGy / s.

[0010] Furthermore, the mass ratio of magnesium aluminum hydrotalcite to nano-zirconium carbide is 4:1 to 2:3.

[0011] Furthermore, the mass ratio of magnesium aluminum hydrotalcite to nano-zirconium carbide is 3:2.

[0012] Furthermore, the magnesium aluminum hydrotalcite is a nano-layered double hydroxide with stearate or dodecylbenzenesulfonate anions between the layers, an interlayer spacing of 2.5~3.5nm, and a particle size D90≤100nm; the average particle size of the nano-zirconium carbide is 30~80nm.

[0013] Furthermore, the antioxidant is a mixture of antioxidant 1010 and antioxidant DSTP in any proportion.

[0014] Furthermore, the lubricant is polyethylene wax or silicone powder.

[0015] The beneficial effects of this invention are as follows: Compared with existing technologies, this invention, through the design of a "sheet-sphere" synergistic modification system of nano-layered double hydroxides and nano-zirconium carbide, combined with the matching optimization of the irradiation crosslinking process, breaks through the technical bottleneck of existing irradiation crosslinking control cables for rail transit vehicles, which struggle to achieve multiple core performance characteristics simultaneously. It achieves a synergistic improvement in high wear resistance, high oil resistance, high flame retardancy, low smoke, and excellent mechanical properties, making it fully adaptable to the complex and harsh service conditions of rail transit vehicles. This invention utilizes the nano-layered double hydroxide sheet structure to form a physical barrier framework, combined with spherical nano-zirconium carbide filling the gaps between the sheets. The synergy of these two components increases the material hardness by 13.2%~17.6% compared to single fillers, reduces the coefficient of friction to below 0.2, and achieves over 800 wear-resistant scratch cycles, far exceeding the level of conventional formulations. Through a closed loop of "structural density → increased hardness → enhanced wear resistance," it achieves a leapfrog improvement in wear resistance.

[0016] The high-density network formed by irradiation crosslinking synergistically with the nanosheet barrier effectively inhibits oil penetration and swelling, enabling the material to maintain excellent performance stability after high-temperature oil immersion, meeting the stringent oil resistance requirements of locomotives. It also solves the industry pain point of easy embrittlement in traditional high flame-retardant filler systems, maintaining excellent mechanical properties while adding large amounts of flame retardants. The material of this invention has a limiting oxygen index ≥38% and a smoke density transmittance ≥92% in flame mode, fully complying with the safety and environmental protection requirements of the rail transit field and possessing extremely high engineering application value. Detailed Implementation

[0017] The specific embodiments of the present invention are described below to enable those skilled in the art to understand the present invention. However, it should be understood that the present invention is not limited to the scope of the specific embodiments. For those skilled in the art, various changes are obvious as long as they are within the spirit and scope of the present invention as defined and determined by the appended claims. All inventions utilizing the concept of the present invention are protected.

[0018] Unless otherwise specified, all raw materials used in the embodiments of this invention are commercially available industrial-grade pure materials.

[0019] Example 1 The modified nanopowders were prepared using the following steps: S1: Weigh 12 parts of magnesium aluminum hydrotalcite and 8 parts of nano zirconium carbide and mix them evenly. After uniform mixing, under high-speed mixing, dilute 2 parts of surface treatment agent with anhydrous ethanol and spray it onto the surface of the mixed powder. Maintain the temperature at 80~100℃ for 15~25 minutes to obtain modified nanoparticles. The interlayer anion of magnesium aluminum hydrotalcite is stearate and the interlayer spacing is 3.0. In specific implementation, the surface treatment agent can also be 1 or 3 parts. S2: The modified nanopowder obtained in S1 is added to a mixer along with 40 parts of linear low-density polyethylene, 30 parts of ethylene-vinyl acetate copolymer, 15 parts of ultra-high molecular weight polysiloxane, 80 parts of modified magnesium hydroxide, 25 parts of aluminum hypophosphite, 2 parts of antioxidant, and 1.5 parts of silicone powder. The mixture is then kneaded at 110-130℃ for 10-20 minutes. Then, 3 parts of triallyl isocyanurate and 2 parts of trimethylolpropane trimethacrylate are added, and the mixture is kneaded for another 3-5 minutes. The kneaded material is then granulated using a twin-screw extruder at an extrusion temperature of 140-170℃ to obtain sheath layer granules. The antioxidant is a mixture of antioxidant 1010 and antioxidant DSTP in a 1:1 mass ratio. In specific implementation, linear low-density polyethylene can be 30 or 50 parts; ethylene-vinyl acetate copolymer can be 35 or 40 parts; ultra-high molecular weight polysiloxane can be 10 or 20 parts; modified magnesium hydroxide can be 60, 70 or 90 parts; aluminum hypophosphite can be 20 or 30 parts; antioxidant can be 1.5, 2.5 or 3 parts; lubricant can be 1 or 2 parts; triallyl isocyanurate can be 2, 4 or 5 parts; trimethylolpropane trimethacrylate can be 1, 2, 2.5 or 3 parts; and lubricant can be polyethylene wax. S3: Add 40 parts of linear low-density polyethylene, 30 parts of ethylene-vinyl acetate copolymer, 80 parts of modified magnesium hydroxide, 25 parts of aluminum hypophosphite, 2 parts of antioxidant, and 1.5 parts of lubricant to a mixer and mix at 110~130℃ for 10~20 minutes. Then add 3 parts of triallyl isocyanurate and 2 parts of trimethylolpropane trimethacrylate and continue mixing for 3~5 minutes. Granulate the mixed material through a twin-screw extruder, controlling the extrusion temperature at 140~170℃ to obtain insulating layer granules. The antioxidant is a mixture of antioxidant 1010 and antioxidant DSTP in a mass ratio of 1:1. In specific implementation, the linear low-density polyethylene can be 30 or 50 parts; the ethylene-vinyl acetate copolymer can be 35 or 40 parts; the modified magnesium hydroxide can be 60, 70 or 90 parts; the aluminum hypophosphite can be 20 or 30 parts; the antioxidant can be 1.5, 2.5 or 3 parts; the lubricant can be 1 or 2 parts; the triallyl isocyanurate can be 2, 4 or 5 parts; the trimethylolpropane trimethacrylate can be 1, 2, 2.5 or 3 parts; and the lubricant can be polyethylene wax. S4: The insulating granules are coated onto the conductor core using an extruder. The extrusion temperature is controlled at 150~180℃ and the extrusion speed is 15~30m / min to form the insulating layer. S5: The sheathing layer granules are coated on the outside of the insulation layer through an extruder. The extrusion temperature is controlled at 150~180℃ and the extrusion speed is 15~30m / min to form the sheathing layer. S6: The extruded cable is cross-linked by irradiation using an electron accelerator; during irradiation cross-linking, the absorbed dose is 80~150kGy and the dose rate is ≤20kGy / s.

[0020] The prepared cable was tested, and the test items and results are shown in Table 1 below; Table 1

[0021] As shown in Table 1, the cable prepared using the method of this invention exhibits excellent oil resistance: the high-density cross-linked network and nanosheet barrier work together to ensure high tensile strength retention and minimal weight change after high-temperature oil immersion, meeting the stringent oil resistance requirements of locomotives and rolling stock. It also demonstrates good comprehensive mechanical properties: even with the addition of a large amount of flame retardant, it maintains high tensile strength and elongation at break, solving the problem of brittleness in traditional flame-retardant materials. Furthermore, it possesses flame-retardant and low-smoke characteristics: a limiting oxygen index ≥38%, and smoke density transmittance ≥92% in flame mode, meeting the stringent safety and environmental protection requirements of rail transit vehicles.

[0022] To verify the effect of irradiation crosslinking on improving the high-temperature stability of materials, an uncrosslinked pure matrix sample was used as a control. An uncrosslinked pure matrix cable sample was obtained by irradiation crosslinking without the addition of triallyl isocyanurate and trimethylolpropane trimethacrylate, using a formulation without electron accelerator crosslinking.

[0023] According to GB / T 2951.21-2008 standard, the thermal elongation test (200℃, 0.2MPa, 15min) was conducted. The thermal elongation rate of the comparative sample was 350%, and permanent deformation was observed. After thermal aging at 150℃ for 168h, the tensile strength retention rate was 58%.

[0024] The sample prepared using the formulation of this invention and the irradiation crosslinking method (absorbed dose 120 kGy) showed a thermal elongation of 45%, no permanent deformation, and a thermal aging tensile strength retention rate of 92%. This indicates that, with the assistance of the TAIC / TMPTMA crosslinking sensitization system, electron beam irradiation enables the LLDPE / EVA molecular chains to form a stable crosslinked network, significantly improving high-temperature stability.

[0025] Example 2 To investigate the effect of nanopowder fillers on cable performance, different methods of adding nanopowder were set up, with the remaining raw materials and steps being the same as in Example 1. Different cables were prepared, and the surface properties of the prepared cables were tested. The addition methods and test results are shown in Table 2 below. Table 2

[0026] As shown in Table 2, the compounding method of this invention can reduce the surface friction coefficient of the cable to 0.2, while the surface friction coefficient of conventional cables prepared using single fillers or no fillers is above 0.7. Furthermore, the hardness of the composite filler group is increased by 13.2%~17.6% compared to the single filler, the surface density is significantly improved, and the wear resistance exhibits a non-linear abrupt change, achieving a macroscopic performance closed loop of "structural density → increased hardness → enhanced wear resistance". A single magnesium aluminum hydrotalcite has micropores on its surface, a layered cross-section, a water absorption rate of 0.32%, and a longitudinal and transverse tensile strength difference of 3.8 MPa; using the compounding method of this invention, the surface is free of pinholes, the cross-section is smooth, the water absorption rate is reduced to 0.08%, and the longitudinal and transverse tensile strength difference is only 0.9 MPa.

[0027] The pure matrix has a tensile stress of 3.2 MPa and a flexural modulus of 280 MPa at 100% tensile strength. However, after adding a composite filler of modified magnesium aluminum hydrotalcite and nano-zirconium carbide using the method of this invention, the tensile stress increases to 6.8 MPa and the flexural modulus increases to 560 MPa. The material's resistance to tensile / flexural deformation is significantly enhanced, and there is no local cracking, proving that a uniformly dispersed inorganic rigid skeleton is formed.

[0028] Example 3 To investigate the effect of surface treatment agents on cable performance, a method was set up where no surface treatment agent was added. Magnesium aluminum hydrotalcite and nano-zirconium carbide were directly mixed and then kneaded in S2. The remaining raw materials and steps were the same as in Example 1. Different cables were prepared, and the mechanical properties of the prepared cables were tested. The test results are shown in Table 3 below. Table 3

[0029] As shown in Table 3, the mechanical properties are significantly improved after the addition of the coupling agent, and there are no filler detachment pits on the tensile cross-section. This proves that the coupling agent enhances the interfacial bonding force between inorganic particles and organic matrix, realizes the tight integration of organic and inorganic networks, and the stress can be effectively transferred.

[0030] Example 4 To investigate the effect of ultra-high molecular weight polysiloxane on cable performance, comparative examples with different amounts of ultra-high molecular weight polysiloxane were set up. The remaining raw materials and steps were the same as in Example 1. Different cables were prepared, and the mechanical properties of the prepared cables were tested. The addition method and test results are shown in Table 4 below. Table 4

[0031] As shown in Table 4, ultra-high molecular weight polysiloxane can form a lubricating layer on the material surface, thereby reducing the coefficient of friction. The "plate-sphere" composite structure provides hard support for the lubricating layer, preventing wear of the lubricating layer. Moreover, the hardness only decreases slightly after adding ultra-high molecular weight polysiloxane, achieving a synergistic effect of "low friction + high wear resistance" (1+1>2).

[0032] Example 5 To investigate the effect of magnesium aluminum hydrotalcite on cable performance, comparative examples of different magnesium aluminum hydrotalcites were set up. The remaining raw materials and steps were the same as in Example 1. Different cables were prepared, and the mechanical properties of the prepared cables were tested. The performance characteristics of magnesium aluminum hydrotalcite and the corresponding test results are shown in Table 5 below. Table 5

[0033] As shown in Table 5, when the interlayer spacing of magnesium aluminum hydrotalcite is 2.5~3.5nm, the mechanical properties, surface condition and processing stability of the material are optimal, which proves that the magnesium aluminum hydrotalcite sheets are fully intercalated and peeled off and uniformly dispersed; when the interlayer spacing is <2.5nm, it is easy to agglomerate, and when it is >3.5nm, the sheets collapse, both of which lead to performance degradation. Stearate / dodecylbenzenesulfonate is a long-chain hydrophobic anion that has good compatibility with the linear low-density polyethylene / ethylene-vinyl acetate copolymer matrix, which is far superior to unmodified magnesium aluminum carbonate hydrotalcite, ensuring intercalation and dispersion effects.

Claims

1. A radiation cross-linked control cable for rail transit vehicles, characterized in that, From the inside out, it includes a conductor, an insulating layer, and a sheath layer; the insulating layer is obtained by mixing and blending a base resin, a flame retardant system, and processing aids, followed by extrusion and granulation to obtain insulating layer particles, which are then extruded again. The sheath layer is obtained by mixing and kneading a base resin, modified nanoparticles, flame retardant system and processing aids, extruding and granulating to obtain sheath layer particles, and then extruding and radiation crosslinking treatment. The modified nanopowder is obtained by mixing magnesium aluminum hydrotalcite and nano zirconium carbide, and then coating it with a surface treatment agent; the surface treatment agent is an aluminum zirconium coupling agent or a titanate coupling agent.

2. The manufacturing process of the irradiated cross-linked control cable for rail transit vehicles according to claim 1, characterized in that, The specific steps are as follows: S1: Weigh magnesium aluminum hydrotalcite and nano zirconium carbide and mix them evenly. After uniform mixing, under high-speed mixing, dilute the surface treatment agent with anhydrous ethanol and spray it onto the surface of the mixed powder. The mass ratio of the mixed powder to the surface treatment agent is 20:1~3. Then, treat it at a temperature of 80~100℃ for 15~25 minutes to obtain modified nano powder. S2: Add 15-35 parts of modified nanoparticles, 30-50 parts of linear low-density polyethylene, 30-40 parts of ethylene-vinyl acetate copolymer, 10-20 parts of ultra-high molecular weight polysiloxane, 60-90 parts of modified magnesium hydroxide, 20-30 parts of aluminum hypophosphite, 1.5-3 parts of antioxidant, and 1-2 parts of lubricant to a mixer and mix at 110-130℃ for 10-20 minutes. Then add 2-5 parts of triallyl isocyanurate and 1-3 parts of trimethylolpropane trimethacrylate and continue mixing for 3-5 minutes. Granulate the mixed material through a twin-screw extruder, controlling the extrusion temperature at 140-170℃ to obtain sheath layer granules. S3: Add 40-60 parts of linear low-density polyethylene, 20-40 parts of ethylene-vinyl acetate copolymer, 80-120 parts of modified magnesium hydroxide, 20-30 parts of aluminum hypophosphite, 1.5-3 parts of antioxidant, and 1-2 parts of lubricant to a mixer and mix at 110-130℃ for 10-20 minutes. Then add 2-5 parts of triallyl isocyanurate and 1-3 parts of trimethylolpropane trimethacrylate and continue mixing for 3-5 minutes. Granulate the mixed material through a twin-screw extruder, controlling the extrusion temperature at 140-170℃ to obtain insulating layer granules. S4: The insulating granules are coated onto the conductor core using an extruder. The extrusion temperature is controlled at 150~180℃ and the extrusion speed is 15~30m / min to form the insulating layer. S5: The sheathing layer granules are coated on the outside of the insulation layer through an extruder. The extrusion temperature is controlled at 150~180℃ and the extrusion speed is 15~30m / min to form the sheathing layer. S6: The extruded cable is cross-linked by irradiation using an electron accelerator; during irradiation cross-linking, the absorbed dose is 80~150kGy and the dose rate is ≤20kGy / s.

3. The preparation process according to claim 2, characterized in that, The mass ratio of the magnesium aluminum hydrotalcite to nano-zirconium carbide is 4:1 to 2:

3.

4. The preparation process according to claim 3, characterized in that, The mass ratio of the magnesium aluminum hydrotalcite to nano-zirconium carbide is 3:

2.

5. The preparation process according to claim 4, characterized in that, The magnesium-aluminum hydrotalcite is a nano-layered double hydroxide with stearate or dodecylbenzenesulfonate anions between the layers, an interlayer spacing of 2.5~3.5nm, and a particle size D90≤100nm; the nano-zirconium carbide has an average particle size of 30~80nm.

6. The preparation process according to claim 2, characterized in that, The antioxidant is a mixture of antioxidant 1010 and antioxidant DSTP in any proportion.

7. The preparation process according to claim 2, characterized in that, The lubricant is polyethylene wax or silicone powder.

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