High-toughness XLPE overhead insulated cable and preparation method thereof
By using a blend matrix of low-density polyethylene, linear low-density polyethylene, and high-density polyethylene, modified with nano-inorganic fillers, and employing dual-terminal vinyl silicone oil and vinyl silane coupling agents, the toughness and strength issues of cross-linked polyethylene insulation materials were resolved, achieving a balance between high toughness and strength.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- NINGGUO MINGFU CABLE CO LTD
- Filing Date
- 2026-02-06
- Publication Date
- 2026-05-12
AI Technical Summary
Cross-linked polyethylene insulation materials are prone to crack propagation when subjected to external forces, leading to the destruction of the insulation layer. Existing toughening methods have problems such as poor interfacial compatibility and stress concentration, resulting in a decrease in the toughness of the material.
Low-density polyethylene, linear low-density polyethylene and high-density polyethylene are blended as the matrix, modified with nano-inorganic fillers, and the interfacial compatibility is improved by double-ended vinyl silicone oil and vinyl silane coupling agent to form chemical bridging. The crosslinking network density is adjusted by combining a flexible phase.
It significantly improves the toughness and impact strength of the material, avoids brittleness, ensures that the material maintains flexibility and elasticity after cross-linking, enhances interfacial bonding, and maximizes the toughening effect of particles.
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Abstract
Description
Technical Field
[0001] This application relates to the technical field of insulated cables, and in particular to a high-toughness XLPE overhead insulated cable and its preparation method. Background Technology
[0002] Cables are key equipment for DC power transmission, and their main raw materials include natural rubber, polyvinyl chloride, synthetic rubber, polyethylene, and cross-linked polyethylene. Among them, cross-linked polyethylene has become the mainstream insulation material due to its excellent heat resistance and mechanical properties, and its long-term operating temperature can reach 90℃. However, due to its three-dimensional network structure, the cross-linking structure restricts the slippage and orientation of molecular chains, making the material prone to cracking and rapid propagation when subjected to external forces such as impact, bending, or ground subsidence. This can lead to insulation layer damage and create short-circuit hazards.
[0003] Existing methods for toughening cross-linked polyethylene include adding micron- or nano-sized inorganic fillers to improve the material's stiffness and heat resistance. However, the poor interfacial compatibility between inorganic fillers and the polymer matrix makes them prone to agglomeration, causing stress concentration and potentially becoming crack initiation sites, leading to a decrease in material toughness. Summary of the Invention
[0004] To improve the toughness of cross-linked polyethylene cable material, this application provides a high-toughness XLPE overhead insulated cable and its preparation method.
[0005] Firstly, this application provides a high-toughness XLPE overhead insulated cable, employing the following technical solution: A high-toughness XLPE overhead insulated cable includes a cable core and an insulation layer. The insulation layer is made of an insulating material, which includes the following raw materials in parts by weight: 50-60 parts of low-density polyethylene, 15-25 parts of linear low-density polyethylene, 15-25 parts of high-density polyethylene, 8-12 parts of modified nano-inorganic filler, 6-14 parts of double-ended vinyl silicone oil, 8-12 parts of initiator, 0.5-1 part of light stabilizer, 0.1-1 part of antioxidant, and 0.2-1 part of lubricant. The modified nano-inorganic filler is prepared by modifying nano-inorganic fillers with silane coupling agents.
[0006] By adopting the above technical solution, this application uses a blend of low-density polyethylene, linear low-density polyethylene and high-density polyethylene as the matrix to form the skeleton of the insulating material. Low-density polyethylene can provide excellent processing fluidity, linear low-density polyethylene can improve the tear resistance and puncture resistance of the material, and high-density polyethylene can improve the rigidity and strength of the material. The blending of the three can balance processability, toughness and strength.
[0007] Modifying nano-inorganic fillers can improve their dispersion uniformity. When the material is subjected to impact and tension, it can induce energy dissipation effects such as crazes and shearing, effectively preventing crack propagation and significantly improving the toughness and impact strength of the material.
[0008] The addition of dual-terminated vinyl silicone oil is a core element of this application, serving a dual function as a crosslinking network regulator and a flexible phase. Firstly, during the crosslinking reaction of the initiator, the vinyl groups at both ends of the dual-terminated vinyl silicone oil participate in the reaction. However, its long, flexible siloxane backbone (-Si-O-Si-) possesses a high degree of freedom of movement (high chain flexibility) within the polyethylene matrix, effectively adding an internal plasticizing segment to the dense polyethylene crosslinking network. This effectively reduces the overall density of the crosslinking network, preventing brittleness caused by excessively dense local crosslinking points, allowing the material to maintain good flexibility and elasticity after crosslinking. Furthermore, the silicone oil molecules themselves constitute a flexible phase dispersed within the polyethylene matrix. When the material is subjected to stress, these flexible micro-regions can absorb and disperse energy through their own deformation, further enhancing the material's toughness.
[0009] This application mainly achieves the joint guarantee of toughness and strength of cross-linked polyethylene insulation materials through the dual synergistic toughening effects of nano-inorganic fillers, cross-linked network density adjustment, and flexible phase.
[0010] Preferably, the viscosity of the dual-terminated vinyl silicone oil is 1000-6000 cSt.
[0011] By adopting the above technical solution, the viscosity is directly proportional to the molecular weight of the dual-terminated vinyl silicone oil. Its molecular chain is relatively short, resulting in limited toughening effect; if its molecular weight is too long, it may lead to difficulty in dispersion in the polyethylene matrix, and may even cause its own long chains to become entangled, resulting in phase separation from the matrix, thus reducing the mechanical properties and toughness of the material. Therefore, a viscosity range of 1000-6000 cSt is the optimal range.
[0012] Preferably, the amount of the dual-terminated vinyl silicone oil added is 9.5-10.5 parts by weight.
[0013] By adopting the above technical solution, the amount of double-ended polyethylene silicone oil used is within the preferred range, which can take into account both the strength and toughness of the insulation material.
[0014] Preferably, the silane coupling agent is a vinylsilane coupling agent.
[0015] By employing the above technical solution, vinyl silane coupling agents can achieve chemical bridging between inorganic nanofillers and the matrix. During peroxide-induced crosslinking, the vinyl groups on the coupling agent can participate in the crosslinking reaction of polyethylene, so that the modified nanofillers are no longer merely physically dispersed in the matrix, but are chemically bonded to the polyethylene crosslinking network. This chemical bridging significantly enhances the interfacial bonding between the filler and the matrix, allowing stress to be more effectively transferred from the matrix to the rigid filler, maximizing the toughening effect of the particles, while avoiding early failure caused by interfacial debonding.
[0016] Preferably, the vinyl silane coupling agent is one or more of vinyltriethoxysilane, acryloyloxymethyltrimethoxysilane, 7-octenyltrimethoxysilane, γ-methacryloyloxypropyltrimethoxysilane, vinyltriisopropoxysilane, and vinyltributylone oxime silane.
[0017] Preferably, the average particle size of the nano-inorganic filler is 50-200 nm.
[0018] By adopting the above technical solutions, fillers with particle sizes within this range have a large specific surface area, a large contact area with the polymer matrix, and a significant interfacial effect. More importantly, fillers of this size can most effectively induce the aforementioned energy dissipation mechanisms such as crazes and shear bands. If the particle size is too large, it tends to resemble traditional fillers, resulting in a decrease in toughening effect and potentially brittleness; if the particle size is too small, the surface energy is extremely high, making it difficult to disperse and prone to agglomeration.
[0019] Preferably, the lubricant is zinc stearate.
[0020] By adopting the above technical solution, the addition of zinc stearate can reduce friction between materials and equipment during processing, lower energy consumption, and prevent material degradation. Simultaneously, zinc stearate has good compatibility with polyolefins, is not prone to precipitation, and helps ensure the smoothness of the insulating material surface and the stability of its insulation performance.
[0021] Secondly, this application provides a method for preparing a high-toughness XLPE overhead insulated cable, using the following technical solution: A method for preparing an anti-aging composite polyvinyl chloride (PVC) overhead insulated cable, wherein the high-toughness XLPE overhead insulated cable is prepared by preparing an insulation layer from an insulation material, and then covering the cable core with the insulation layer. The method for preparing the insulation material includes the following steps: The raw materials for the insulating material are mixed evenly, and then the mixture is fed into the first stage of the two-stage compounding extrusion unit, a co-rotating twin-screw compounding mill, for compounding and extrusion. The mixture stays in the screw for 350-500 seconds to obtain the extruded material. The feed section temperature is set at 135-150℃, the compression section at 160-175℃, the homogenization section at 185-200℃, the discharge section at 160-170℃, and the main machine speed at 400-600 rpm. The extruded material is fed into a second-stage single-screw extruder. The temperature of the single-screw extruder is set to 125-140℃ and the speed to 100-300rpm. The material is then extruded, pelletized, and used to obtain insulating material.
[0022] By adopting the above technical solutions, in the first-stage co-rotating twin-screw extruder, the high speed, high shear, and multiple mixing stages ensure the full dispersion of nanofillers and the highly uniform mixing of each component. Strictly controlling the residence time (350-500s) is the balance point to ensure uniform mixing and prevent overheating and degradation. In the second-stage single-screw extruder, at lower temperatures and speeds, it mainly serves to build pressure, vent air, and stabilize extrusion, ensuring the regularity of granulation and the density of the material, and avoiding bubble formation.
[0023] In summary, this application includes at least one of the following beneficial technical effects: 1. This application uses a blend of low-density polyethylene, linear low-density polyethylene, and high-density polyethylene as the matrix to form the skeleton structure of the insulating material. Modification of the nano-inorganic filler improves its dispersion uniformity. Under impact and tension, it induces energy dissipation effects such as crazes and shearing, effectively preventing crack propagation and significantly improving the material's toughness and impact strength. The addition of dual-terminated vinyl silicone oil is a core key point of this application, serving a dual function as a crosslinking network regulator and a flexible phase. First, in the crosslinking reaction of the initiator, the two vinyl groups of the dual-terminated vinyl silicone oil participate in the reaction. However, its long, flexible siloxane backbone (-Si-O-Si-) has a high degree of freedom of movement (high chain flexibility) within the polyethylene matrix, equivalent to adding an internal plasticizing segment to the dense polyethylene crosslinking network. This effectively reduces the overall density of the crosslinking network, avoiding brittleness caused by excessively dense local crosslinking points, allowing the material to maintain good flexibility and elasticity after crosslinking. Furthermore, the silicone oil molecules themselves constitute a flexible phase dispersed within the polyethylene matrix. When the material is subjected to stress, these flexible microregions can absorb and disperse energy through their own deformation, further improving the material's toughness. This application mainly achieves the dual guarantee of toughness and strength of cross-linked polyethylene insulation materials through the synergistic toughening effects of nano-inorganic fillers, cross-linked network density adjustment, and flexible phase.
[0024] 2. Vinyl silane coupling agents can achieve chemical bridging between inorganic nanofillers and the matrix. During peroxide-induced crosslinking, the vinyl groups on the coupling agent can participate in the crosslinking reaction of polyethylene, so that the modified nanofillers are no longer merely physically dispersed in the matrix, but are connected to the polyethylene crosslinking network through chemical bonds. This chemical bridging greatly enhances the interfacial bonding force between the filler and the matrix, allowing stress to be transferred more effectively from the matrix to the rigid filler, maximizing the toughening effect of the particles, while avoiding early failure caused by interfacial debonding.
[0025] 3. The tensile strength of the insulating materials prepared in this application can reach 25.1 MPa or above, with a maximum of 27.1 MPa; its elongation at break can also be maintained between 435-462%; at the same time, its impact embrittlement performance is good, and no breakage occurs; indicating that the insulating materials of this application have excellent mechanical properties and toughness. Detailed Implementation
[0026] The following provides a more detailed description of this application in conjunction with specific details.
[0027] raw material The raw materials used in the embodiments of this application are all commercially available products. Among them, the linear low-density polyethylene is model 7042, manufactured by China National Petroleum Corporation; the high-density polyethylene is model HDPE 25055E, manufactured by Dow Chemical Company; the low-density polyethylene is model 2426H, manufactured by China National Petroleum Corporation; the double-ended vinyl silicone oil is manufactured by Momentive Performance Materials; the light stabilizer is model UV-326; the antioxidant is antioxidant 1010; and the lubricant is zinc stearate. Example
[0028] Examples 1-3 A high-toughness XLPE overhead insulated cable includes a cable core and an insulation layer. The insulation layer is made of an insulating material. The raw materials and their quantities are shown in Table 1. The preparation method is as follows: S1. Preparation of modified nano-inorganic fillers Nano-silica (average particle size of 100 nm) was dispersed in a 1:1 volume ratio ethanol / water mixed solution. After ultrasonic dispersion, 7-octenyltrimethoxysilane was added, the temperature was raised to 75 °C, and the reaction was stirred for 2 h. Then, the mixture was filtered and dried to obtain the modified nano-inorganic filler. The mass ratio of nano-silica, solution and 7-octenyltrimethoxysilane is 10:200:1. S2. Take the raw materials according to the amount in Table 1, mix the raw materials evenly, and then feed the mixture into the first stage co-rotating twin-screw extruder of the two-stage compounding extruder unit for compounding and extrusion. The first stage co-rotating twin-screw extruder is a Φ75 type twin-screw extruder with a length-to-diameter ratio of 48:1. The mixture stays in the screw for 400s to obtain the extruded material. Set the feed section temperature to 140℃, the compression section temperature to 165℃, the homogenization section temperature to 190℃, the discharge section temperature to 165℃, and the main engine speed to 450rpm. The extruded material is fed into a second-stage single-screw extruder, and the temperature of the single-screw extruder is set to 130℃ and the speed to 100rpm. The material is then extruded, pelletized, and used to obtain insulating material.
[0029] The dual-end vinyl silicone oil is designated VS-1000, with a viscosity of 1000 cSt at 25°C.
[0030] Table 1. Raw materials and dosage (kg) for Examples 1-3
[0031] Example 4 A high-toughness XLPE overhead insulated cable differs from Example 2 in that its 7-octenyltrimethoxysilane is replaced with an equimolar amount of methyltriethoxysilane, while the remaining steps are the same as in Example 2.
[0032] Example 5 A high-toughness XLPE overhead insulated cable differs from Example 2 in that its double-ended vinyl silicone oil is VS-3000 with a viscosity of 3000 cSt at 25°C, while the remaining steps are the same as in Example 2.
[0033] Example 6 A high-toughness XLPE overhead insulated cable differs from Example 2 in that its double-ended vinyl silicone oil is VS-6000 with a viscosity of 6000 cSt at 25°C, while the remaining steps are the same as in Example 2.
[0034] Example 7 A high-toughness XLPE overhead insulated cable differs from Example 6 in that the amount of vinyl silicone oil added to both ends is 6 kg, while the remaining steps are the same as in Example 6.
[0035] Example 8 A high-toughness XLPE overhead insulated cable differs from Example 6 in that the amount of vinyl silicone oil added to both ends is 14 kg, while the remaining steps are the same as in Example 6.
[0036] Comparative Example 1 A high-toughness XLPE overhead insulated cable differs from Example 2 in that its modified nano-inorganic filler is replaced with an equal mass of nano-silica (average particle size of 100nm), while the remaining steps are the same as in Example 2.
[0037] Comparative Example 2 A high-toughness XLPE overhead insulated cable differs from Example 2 in that its double-ended vinyl silicone oil is VS-10000 with a viscosity of 10000 cSt at 25°C, while the remaining steps are the same as in Example 2.
[0038] Performance testing Detection methods / test methods Insulation materials for high-toughness XLPE overhead insulated cables were prepared according to the preparation methods of Examples 1-8 and Comparative Examples 1-2, and then tested according to the following testing methods. The test results are shown in Table 1.
[0039] The tests were conducted according to the testing methods in JB / T 10260-2014.
[0040] Table 1. Detection results of Examples 1-8 and Comparative Examples 1-2
[0041] As can be seen from the test data in Table 1, the tensile strength of the insulating materials prepared in this application can reach 25.1 MPa or above, with a maximum of 27.1 MPa; its elongation at break can also be maintained between 435-462%; at the same time, its impact embrittlement performance is good, and no breakage occurs; indicating that the insulating materials of this application have excellent mechanical properties and toughness.
[0042] Through Examples 2 and 4 and Comparative Example 1, vinyl silane coupling agents can achieve chemical bridging between inorganic nanofillers and the matrix. During peroxide-induced crosslinking, the vinyl groups on the coupling agent can participate in the crosslinking reaction of polyethylene, so that the modified nanofillers are no longer merely physically dispersed in the matrix, but are chemically bonded to the polyethylene crosslinking network. This chemical bridging significantly enhances the interfacial bonding between the filler and the matrix, allowing stress to be more effectively transferred from the matrix to the rigid filler, maximizing the toughening effect of the particles, while avoiding early failure caused by interfacial debonding.
[0043] Based on Examples 2, 5, and 6 and Comparative Example 2, the viscosity is directly proportional to the molecular weight of the double-ended vinyl silicone oil. Shorter molecular chains result in limited toughening effects, while excessively long molecular weights may lead to difficulty in dispersion within the polyethylene matrix, or even cause long-chain entanglement and phase separation from the matrix, thus reducing the material's mechanical properties and toughness. Therefore, a viscosity range of 1000-6000 cSt is preferred. Based on Examples 7-8, a dosage of 10 kg of double-ended polyethylene silicone oil is optimal, balancing the strength and toughness of the insulating material.
[0044] This specific embodiment is merely an explanation of the present invention and is not intended to limit the invention. After reading this specification, those skilled in the art can make modifications to this embodiment without contributing any inventive step, but such modifications are protected by patent law as long as they are within the scope of the claims of the present invention.
Claims
1. A high-toughness XLPE overhead insulated cable, characterized in that: It includes a cable core and an insulation layer. The insulation layer is made of an insulating material, which includes the following raw materials in parts by weight: 50-60 parts of low-density polyethylene, 15-25 parts of linear low-density polyethylene, 15-25 parts of high-density polyethylene, 8-12 parts of modified nano-inorganic filler, 6-14 parts of double-ended vinyl silicone oil, 8-12 parts of initiator, 0.5-1 part of light stabilizer, 0.1-1 part of antioxidant, and 0.2-1 part of lubricant. The modified nano-inorganic filler is prepared by modifying nano-inorganic fillers with silane coupling agents.
2. The high-toughness XLPE overhead insulated cable according to claim 1, characterized in that: The viscosity of the dual-terminated vinyl silicone oil is 1000-6000 cSt.
3. The high-toughness XLPE overhead insulated cable according to claim 2, characterized in that: The amount of the dual-terminated vinyl silicone oil added is 9.5-10.5 parts by weight.
4. The high-toughness XLPE overhead insulated cable according to claim 1, characterized in that: The silane coupling agent is a vinylsilane coupling agent.
5. A high-toughness XLPE overhead insulated cable according to claim 4, characterized in that: The vinyl silane coupling agent is one or more of vinyltriethoxysilane, acryloyloxymethyltrimethoxysilane, 7-octenyltrimethoxysilane, γ-methacryloyloxypropyltrimethoxysilane, vinyltriisopropoxysilane, and vinyltributylone oxime silane.
6. The high-toughness XLPE overhead insulated cable according to claim 1, characterized in that: The average particle size of the nano-inorganic filler is 50-200 nm.
7. The high-toughness XLPE overhead insulated cable according to claim 1, characterized in that: The lubricant is zinc stearate.
8. A method for preparing an anti-aging composite polyvinyl chloride overhead insulated cable according to any one of claims 1-7, characterized in that: The high-toughness XLPE overhead insulated cable is made by preparing an insulation layer from an insulation material, and then covering the cable core with the insulation layer. The preparation method of the insulation material includes the following steps: The raw materials for the insulating material are mixed evenly, and then the mixture is fed into the first stage of the two-stage compounding extrusion unit, a co-rotating twin-screw compounding mill, for compounding and extrusion. The mixture stays in the screw for 350-500 seconds to obtain the extruded material. The feed section temperature is set at 135-150℃, the compression section at 160-175℃, the homogenization section at 185-200℃, the discharge section at 160-170℃, and the main machine speed at 400-600 rpm. The extruded material is fed into a second-stage single-screw extruder. The temperature of the single-screw extruder is set to 125-140℃ and the speed to 100-300rpm. The material is then extruded, pelletized, and used to obtain insulating material.