A tear-resistant insulation material for low-voltage power cables and a method for producing the same

Abstract

This invention relates to the field of cable material technology, and more particularly to a tear-resistant insulation material for low-voltage power cables and its preparation method. The tear-resistant insulation material for low-voltage power cables, by weight, comprises the following components: 60-100 parts polyethylene, 5-15 parts maleic anhydride-grafted ethylene-octene copolymer, 3-8 parts modified basalt fiber, 1.5-2.5 parts vinyltrimethoxysilane, 0.05-0.15 parts crosslinking catalyst, and 0.2-0.8 parts antioxidant. This invention constructs a functional layer containing disulfide bonds on the surface of basalt fiber through a three-step chemical grafting process and introduces octadecylamine long-chain alkyl groups, achieving a strong bond between the fiber and the matrix. This significantly improves tear resistance while maintaining excellent electrical insulation properties, making it suitable for long-term cable service.

Description

Technical Field

[0001] This invention relates to the field of cable material technology, and in particular to a tear-resistant insulation material for low-voltage power cables and its preparation method. Background Technology

[0002] During the manufacturing, laying, and long-term operation of low-voltage power cables, the insulation layer is subjected to various forms of mechanical stress: tension and bending during manufacturing, dragging and compression during laying, cyclic stress caused by thermal expansion and contraction during operation, and external impacts. These stresses often concentrate around tiny defects inside the insulation layer or at the interface, making them highly susceptible to crack initiation and propagation. Once microcracks appear in the insulation layer, under the combined action of electric field and mechanical stress, the cracks will gradually propagate, eventually leading to insulation breakdown and cable short-circuit accidents. Therefore, endowing the cable insulation layer with excellent tear resistance is key to improving cable operational reliability and extending service life.

[0003] Currently, one common method to improve the tear resistance of cable insulation materials is to add short fibers to the polyethylene matrix for physical reinforcement. For example, Chinese patent CN 104829914A discloses a silane cross-linked polyethylene cable material with high tensile strength, which is made from the following raw materials in parts by weight: 65-75 parts high-density polyethylene, 25-35 parts polypropylene short fibers, 14.5-17.5 parts MC nylon, 16-19 parts isopropyl trioleoyl titanate, 0.2-0.5 parts diphenylamine, 0.3-0.6 parts diphenylethylene, 3-5 parts barium carbonate, 4-7 parts titanium nitride, 5-8 parts calcium nitrate, 10-15 parts tourmaline powder, 30-45 parts bisphenol F epoxy resin, and appropriate amount of water. By adding polypropylene short fibers and blending them with polyethylene, the tensile strength of the cable material is improved by utilizing the bridging effect of the fibers. However, in this technical solution, the fiber and the matrix are only bonded by physical interlocking or van der Waals forces, and the interfacial shear strength is usually low. Under long-term alternating stress, the fiber-matrix interface is prone to debonding, the bridging and pull-out effects of the fiber cannot be fully utilized, and the tear resistance of the material will be reduced.

[0004] Therefore, strengthening the interfacial bond between the fiber and the polyethylene matrix and improving tear resistance are of great practical significance for the long-term safe operation of cables. Summary of the Invention

[0005] This invention proposes a tear-resistant insulation material for low-voltage power cables and its preparation method. The resulting insulation material has excellent tear resistance and is suitable for long-term service of cables.

[0006] The technical solution of the present invention is implemented as follows: The present invention provides a tear-resistant insulation material for low-voltage power cables, comprising the following components by weight: 60-100 parts of polyethylene, 5-15 parts of maleic anhydride-grafted ethylene-octene copolymer, 3-8 parts of modified basalt fiber, 1.5-2.5 parts of vinyltrimethoxysilane, 0.05-0.15 parts of crosslinking catalyst, and 0.2-0.8 parts of antioxidant.

[0007] This invention provides a tear-resistant insulation material for low-voltage power cables, comprising the following components by weight: 60-100 parts of polyethylene, 5-15 parts of maleic anhydride-grafted ethylene-octene copolymer, 3-8 parts of modified basalt fiber, 1.5-2.5 parts of vinyltrimethoxysilane, 0.05-0.15 parts of crosslinking catalyst, and 0.2-0.8 parts of antioxidant.

[0008] Polyethylene is preferred as the matrix resin, especially long-chain branched linear low-density polyethylene. Its long-chain branched structure imparts high melt strength, facilitating the orientation of short fibers along the flow direction during processing and ensuring the molding stability of extrusion coating. The maleic anhydride-grafted ethylene-octene copolymer (POE-g-MAH) contains both anhydride groups that react with the amino groups on the modified basalt fiber surface and a polyolefin backbone compatible with the polyethylene matrix. During melt blending, the anhydride groups undergo a ring-opening reaction with the terminal amino groups retained in the functional layer on the modified basalt fiber surface, forming stable amide bonds. Simultaneously, its polyethylene backbone is tightly bonded to the matrix polyethylene through molecular chain entanglement and co-crystallization, thereby enhancing the bonding force between the modified basalt fiber and the matrix. The modified basalt fiber is the reinforcing phase of this invention. Its surface undergoes a three-step chemical grafting process to construct a functional layer containing disulfide bonds and introduce octadecylamine long-chain alkyl groups, which significantly improves the insulation material's tear strength, interfacial toughness, and self-healing ability simultaneously.

[0009] Based on the above technical solutions, preferably, the preparation method of the modified basalt fiber includes the following steps: S1. Basalt fibers are placed in a γ-aminopropyltriethoxysilane solution for amination modification to obtain amination-modified basalt fibers. S2. Aminated modified basalt fiber and hexamethylene diisocyanate trimer are dispersed in DMF and reacted to obtain modified basalt fiber intermediate; S3. The modified basalt fiber intermediate is dispersed in DMF with octadecylamine and cystamine to obtain modified basalt fiber.

[0010] This application utilizes the high strength and high modulus of basalt fiber as a reinforcing phase and constructs a functional layer on the fiber surface through a three-step chemical grafting process. First, amino groups are introduced onto the surface of basalt fibers. Then, the HDI trimer is grafted onto the surface of basalt fibers by reacting the -NCO groups of hexamethylene diisocyanate trimer (HDI trimer). Next, a mixed system of cystamine and octadecylamine is used to react with the remaining -NCO groups of the HDI trimer. Cystamine, as a bifunctional chain extender, constructs a functional layer containing disulfide bonds. This functional layer can fill the interfacial micro-defects between the basalt fiber and the matrix, strengthen the interfacial bonding between the basalt fiber and the matrix, and effectively limit crack propagation when subjected to tearing stress. The reversible breakage and recombination of the disulfide bonds introduced by cystamine endows the material interface with self-healing ability. Octadecylamine, as a monofunctional end-capping agent, introduces long-chain alkyl groups to impart hydrophobicity to the fiber surface, improve the dispersibility of basalt fibers in the polyolefin matrix, inhibit the aggregation of basalt fibers, and simultaneously construct a hydrophobic protective layer on the surface of the basalt fibers to block water vapor intrusion and stabilize the electrical performance of the cable insulation. In addition, HDI trimer, as an aliphatic polyisocyanate, has a saturated chain structure that endows the functional layer with excellent resistance to yellowing and weathering, making it suitable for long-term outdoor use of cables.

[0011] Based on the above technical solutions, preferably, in step S1, the mass ratio of the basalt fiber to γ-aminopropyltriethoxysilane is 1:0.02 to 0.10.

[0012] Based on the above technical solutions, preferably, in step S1, the amination modification reaction temperature is 50-80℃ and the reaction time is 2-6h.

[0013] Based on the above technical solutions, preferably, in step S1, the length of the basalt fiber is 100-500 μm and the aspect ratio is 20-60.

[0014] Specifically, when the length of basalt fibers is too short, the reinforcing effect is not obvious; when it is too long, they are difficult to disperse evenly in the matrix. A suitable aspect ratio can take into account both the bridging effect and processing fluidity of basalt fibers, ensuring the reinforcing effect of basalt fibers while avoiding the problems of insufficient reinforcing effect when basalt fibers are too short and easy entanglement and agglomeration when basalt fibers are too long.

[0015] Based on the above technical solutions, preferably, in step S2, the mass ratio of the aminated modified basalt fiber to the hexamethylene diisocyanate trimer is 1:0.2 to 0.4.

[0016] Based on the above technical solutions, preferably, in step S2, the reaction is carried out under inert gas protection, the reaction temperature is 10-60℃, and the reaction time is 2-8h.

[0017] Based on the above technical solutions, preferably, in step S3, the mass ratio of the modified basalt fiber intermediate to octadecylamine and cystamine is 1:0.02~0.06:0.08~0.2.

[0018] By controlling the total amount of amino groups in S3 to be excessive relative to the -NCO groups in the modified basalt fiber intermediate, the terminal amino groups are retained on the surface of the functional layer, thereby forming an amide bond chemical anchor with POE-g-MAH.

[0019] Based on the above technical solutions, preferably, in step S3, the reaction temperature is 20-60℃ and the reaction time is 1-6h.

[0020] Based on the above technical solutions, preferably, the polyethylene is a long-chain branched linear low-density polyethylene; the crosslinking catalyst is dibutyltin dilaurate; and the antioxidant is one or more of antioxidant 1010, antioxidant 168, and antioxidant 1076.

[0021] Based on the above technical solutions, preferably, the grafting rate of the maleic anhydride-grafted ethylene-octene copolymer is 0.5% to 2.0%, and the melt index is 0.5 to 5.0 g / 10 min at 190°C and 2.16 kg load.

[0022] This invention also provides a method for preparing a tear-resistant insulation material for low-voltage power cables, comprising the following steps: S1. Weigh each raw material component according to the weight parts and mix them evenly to obtain a mixture; S2. The mixture is melt-blended and extruded in a twin-screw extruder to obtain granules; S3. After extruding the granulated material and coating it onto the cable conductor, it is placed in warm water for cross-linking to obtain the tear-resistant insulation material for low-voltage power cables.

[0023] Based on the above technical solution, preferably, in step S2, the melt blending temperature is 160–200°C, and the screw speed of the twin-screw extruder is 150–300 rpm. Based on the above technical solutions, preferably, in step S3, the extrusion coating temperature is 170-190℃; the crosslinking temperature in the warm water is 80-95℃ and the time is 4-8h.

[0024] The tear-resistant insulation material for low-voltage power cables and its preparation method provided by this invention have the following advantages over the prior art: (1) This invention achieves in-situ growth of a functional layer containing disulfide bonds on the surface of basalt fibers through a three-step chemical grafting process, and introduces long-chain alkyl groups, thereby significantly improving the tear resistance and interfacial hydrophobicity of the insulation material. Basalt fibers themselves have high strength, high modulus, and excellent heat resistance and corrosion resistance, making them an ideal toughening material for cable insulation. First, amino groups are introduced onto the surface of basalt fibers through a silane coupling agent. Then, multiple isocyanate groups are introduced onto the fiber surface through the reaction of hexamethylene diisocyanate trimer with the amino groups. Next, an interfacial polymerization reaction is carried out between the isocyanate groups and a mixed chain extender of octadecylamine and cystamine, thereby growing a functional layer containing disulfide bonds in situ on the surface of basalt fibers. This functional layer fills micro-defects at the interface between basalt fibers and the matrix, effectively limiting crack propagation under tearing stress. The disulfide bonds introduced by cystamine endow the functional layer with reversible self-healing capabilities. Octadecylamine, as a monofunctional end-capping agent, forms a dense hydrophobic layer on the fiber surface with its long-chain alkyl groups, significantly reducing surface energy and inhibiting moisture accumulation at the basalt fiber-matrix interface, thus delaying water treeing aging. Simultaneously, the flexibility of the long-chain alkyl groups provides a certain degree of lubrication, reducing friction and wear. Furthermore, HDI trimer, as an aliphatic polyisocyanate, endows the functional layer with excellent resistance to yellowing and weathering due to its saturated chain structure, making it suitable for long-term outdoor use of cables.

[0025] (2) In this invention, the terminal amino groups remaining in the functional layer on the surface of the modified basalt fiber undergo a ring-opening reaction with the anhydride groups of POE-g-MAH to form stable amide bonds. The polyethylene backbone of POE-g-MAH has excellent compatibility with the polyethylene matrix, and they are tightly bound together through molecular chain entanglement and co-crystallization, thereby firmly anchoring the modified basalt fiber into the polyethylene matrix. When the insulation material is subjected to tearing stress, breaking this chemical anchoring interface requires breaking the amide bonds, which requires higher energy than overcoming the frictional force in traditional physical blending systems. Therefore, the critical energy required for tearing is significantly increased, resulting in a significant improvement in tear strength compared to traditional physical blending systems.

[0026] (3) The preparation process of the present invention does not require complex equipment modification. It can be achieved by adding only a fiber surface modification step to the existing silane cross-linked cable production line. It is highly compatible with the existing production line, easy to operate, and has low production cost, making it suitable for large-scale industrial production. The resulting insulation material has high tear strength, excellent electrical insulation properties and good interface self-healing ability, which can meet the service requirements of low-voltage power cables under long-term complex working conditions. Detailed Implementation

[0027] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the 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] It should be noted that the polyethylene used in all embodiments and comparative examples of this invention is long-chain branched linear low-density polyethylene with a melt index of 1.5 g / 10 min at 190°C and 2.16 kg load; the grafting rate of the maleic anhydride-grafted ethylene-octene copolymer is 1.2%, and the melt index is 2.0 g / 10 min at 190°C and 2.16 kg load; the basalt fiber has a length of 300 μm and a diameter of 7.5 μm and was purchased from Sichuan Qianyi Composite Materials Co., Ltd.

[0029] Example 1

[0030] This embodiment provides a method for preparing tear-resistant insulation material for low-voltage power cables, including the following steps: Weigh out 80 parts by weight of polyethylene, 10 parts by weight of maleic anhydride-grafted ethylene-octene copolymer, 5.5 parts by weight of modified basalt fiber, 2 parts by weight of vinyltrimethoxysilane, 0.1 parts by weight of dibutyltin dilaurate, and 0.5 parts by weight of antioxidant 1010, and mix them evenly to obtain a mixture. Melt-blend and extrude the mixture in a twin-screw extruder at a melt-blending temperature of 180°C and a screw speed of 220 rpm to obtain granules. Extrude the granules at 180°C to coat the cable conductor, and then place them in 90°C warm water for crosslinking for 6 hours to obtain the tear-resistant insulation material for low-voltage power cables.

[0031] The preparation method of modified basalt fiber is as follows: S1. Take 10g of basalt fiber and place it in 100mL of ethanol-water mixed solution (ethanol to water volume ratio of 9:1) containing 0.6g of γ-aminopropyltriethoxysilane. Adjust the pH to 4.5 with acetic acid and react at 65℃ for 4h. After the reaction is complete, filter, wash with ethanol, and vacuum dry at 80℃ for 4h to obtain aminated modified basalt fiber.

[0032] S2. Take 10g of aminated modified basalt fiber and 3g of hexamethylene diisocyanate trimer, disperse them in 150ml of DMF, react at 35℃ for 5 hours under nitrogen protection, filter after the reaction is completed, wash with DMF, and vacuum dry at 80℃ for 4 hours to obtain the modified basalt fiber intermediate.

[0033] S3. Take 10g of modified basalt fiber intermediate, add 0.4g of octadecylamine and 1.4g of cystamine, disperse in 150mL of DMF, react at 40℃ for 3.5h, filter after the reaction is complete, wash with DMF, and vacuum dry at 80℃ for 4h to obtain modified basalt fiber.

[0034] Example 2

[0035] This embodiment provides a method for preparing tear-resistant insulation material for low-voltage power cables, including the following steps: Weigh out 60 parts by weight of polyethylene, 5 parts by weight of maleic anhydride-grafted ethylene-octene copolymer, 3 parts by weight of modified basalt fiber, 1.5 parts by weight of vinyltrimethoxysilane, 0.05 parts by weight of dibutyltin dilaurate, and 0.2 parts by weight of antioxidant 1010. Mix them evenly to obtain a mixture. Melt-blend and extrude the mixture in a twin-screw extruder at a melt-blending temperature of 160°C and a screw speed of 150 rpm to obtain granules. Extrude the granules at 170°C to coat the cable conductor, and then place them in 80°C warm water for crosslinking for 8 hours to obtain the tear-resistant insulation material for low-voltage power cables.

[0036] The preparation method of modified basalt fiber is as follows: S1. Take 10g of basalt fiber and place it in 100mL of ethanol-water mixed solution (ethanol to water volume ratio of 9:1) containing 0.2g of γ-aminopropyltriethoxysilane. Adjust the pH to 4 with acetic acid and react at 80℃ for 1h. After the reaction is complete, filter, wash with ethanol, and vacuum dry at 80℃ for 4h to obtain aminated modified basalt fiber.

[0037] S2. Take 10g of aminated modified basalt fiber and 2g of hexamethylene diisocyanate trimer, disperse them in 150mL of DMF, react at 10℃ for 8h under nitrogen protection, filter after the reaction is complete, wash with DMF, and vacuum dry at 80℃ for 4h to obtain the modified basalt fiber intermediate.

[0038] S3. Take 10g of modified basalt fiber intermediate, add 0.2g of octadecylamine and 0.8g of cystamine, disperse in 150mL of DMF, react at 20℃ for 6h, filter after the reaction is complete, wash with DMF, and vacuum dry at 80℃ for 4h to obtain modified basalt fiber.

[0039] Example 3

[0040] This embodiment provides a method for preparing tear-resistant insulation material for low-voltage power cables, including the following steps: Weigh out 100 parts by weight of polyethylene, 15 parts by weight of maleic anhydride-grafted ethylene-octene copolymer, 8 parts by weight of modified basalt fiber, 2.5 parts by weight of vinyltrimethoxysilane, 0.15 parts by weight of dibutyltin dilaurate, and 0.8 parts by weight of antioxidant 1010, and mix them evenly to obtain a mixture. Melt-blend and extrude the mixture in a twin-screw extruder at a melt-blending temperature of 200°C and a screw speed of 300 rpm to obtain granules. Extrude the granules at 190°C to coat the cable conductor, and then place them in 95°C warm water for crosslinking for 4 hours to obtain the tear-resistant insulation material for low-voltage power cables.

[0041] The preparation method of modified basalt fiber is as follows: S1. Take 10g of basalt fiber and place it in 100mL of ethanol-water mixed solution (ethanol to water volume ratio of 9:1) containing 1g of γ-aminopropyltriethoxysilane. Adjust the pH to 5 with acetic acid and react at 50℃ for 6h. After the reaction is completed, filter, wash with ethanol, and vacuum dry at 80℃ for 4h to obtain aminated modified basalt fiber.

[0042] S2. Take 10g of aminated modified basalt fiber and 4g of hexamethylene diisocyanate trimer, disperse them in 150mL of DMF, react at 60℃ for 2h under nitrogen protection, filter after the reaction is complete, wash with DMF, and vacuum dry at 80℃ for 4h to obtain the modified basalt fiber intermediate.

[0043] S3. Take 10g of modified basalt fiber intermediate, add 0.6g of octadecylamine and 2g of cystamine, disperse in 150mL of DMF, react at 60℃ for 1h, filter after the reaction is complete, wash with DMF, and vacuum dry at 80℃ for 4h to obtain modified basalt fiber.

[0044] Comparative Example 1 This comparative example provides a method for preparing insulation material for low-voltage power cables, including the following steps: Weigh out 80 parts by weight of polyethylene, 10 parts by weight of maleic anhydride-grafted ethylene-octene copolymer, 5.5 parts by weight of basalt fiber, 2 parts by weight of vinyltrimethoxysilane, 0.1 parts by weight of dibutyltin dilaurate, and 0.5 parts by weight of antioxidant 1010, and mix them evenly to obtain a mixture. Melt-blend and extrude the mixture in a twin-screw extruder at a melt-blending temperature of 180°C and a screw speed of 220 rpm to obtain granules. Extrude the granules at 180°C to coat the cable conductor, and then place them in 90°C warm water for crosslinking for 6 hours to obtain the tear-resistant insulation material for low-voltage power cables.

[0045] The difference between Comparative Example 1 and Example 1 is that the basalt fibers are not modified.

[0046] Comparative Example 2 This comparative example provides a method for preparing insulation material for low-voltage power cables, including the following steps: Weigh out 80 parts by weight of polyethylene, 10 parts by weight of maleic anhydride-grafted ethylene-octene copolymer, 5.5 parts by weight of modified basalt fiber, 2 parts by weight of vinyltrimethoxysilane, 0.1 parts by weight of dibutyltin dilaurate, and 0.5 parts by weight of antioxidant 1010, and mix them evenly to obtain a mixture. Melt-blend and extrude the mixture in a twin-screw extruder at a melt-blending temperature of 180°C and a screw speed of 220 rpm to obtain granules. Extrude the granules at 180°C to coat the cable conductor, and then place them in 90°C warm water for crosslinking for 6 hours to obtain the tear-resistant insulation material for low-voltage power cables.

[0047] The preparation method of modified basalt fiber is as follows: S1. Take 10g of basalt fiber and place it in 100mL of ethanol-water mixed solution (ethanol to water volume ratio of 9:1) containing 0.6g of γ-aminopropyltriethoxysilane. Adjust the pH to 4.5 with acetic acid and react at 65℃ for 4h. After the reaction is complete, filter, wash with ethanol, and vacuum dry at 80℃ for 4h to obtain aminated modified basalt fiber.

[0048] The difference between Comparative Example 2 and Example 1 is that the basalt fiber is only modified by amination.

[0049] Comparative Example 3 This comparative example provides a method for preparing insulation material for low-voltage power cables, including the following steps: Weigh out 80 parts by weight of polyethylene, 10 parts by weight of maleic anhydride-grafted ethylene-octene copolymer, 5.5 parts by weight of modified basalt fiber, 2 parts by weight of vinyltrimethoxysilane, 0.1 parts by weight of dibutyltin dilaurate, and 0.5 parts by weight of antioxidant 1010, and mix them evenly to obtain a mixture. Melt-blend and extrude the mixture in a twin-screw extruder at a melt-blending temperature of 180°C and a screw speed of 220 rpm to obtain granules. Extrude the granules at 180°C to coat the cable conductor, and then place them in 90°C warm water for crosslinking for 6 hours to obtain the tear-resistant insulation material for low-voltage power cables.

[0050] The preparation method of modified basalt fiber is as follows: S1. Take 10g of basalt fiber and place it in 100mL of ethanol-water mixed solution (ethanol to water volume ratio of 9:1) containing 0.6g of γ-aminopropyltriethoxysilane. Adjust the pH to 4.5 with acetic acid and react at 65℃ for 4h. After the reaction is complete, filter, wash with ethanol, and vacuum dry at 80℃ for 4h to obtain aminated modified basalt fiber.

[0051] S2. Take 10g of aminated modified basalt fiber and 3g of hexamethylene diisocyanate trimer, disperse them in 150ml of DMF, react at 35℃ for 5 hours under nitrogen protection, filter after the reaction is completed, wash with DMF, and vacuum dry at 80℃ for 4 hours to obtain the modified basalt fiber intermediate.

[0052] S3. Take 10g of modified basalt fiber intermediate, add 1.4g of cystamine, disperse in 150mL of DMF, react at 40℃ for 3.5h, filter after the reaction is complete, wash with DMF, and vacuum dry at 80℃ for 4h to obtain modified basalt fiber.

[0053] The difference between Comparative Example 3 and Example 1 is that octadecylamine is not added in the basalt fiber modification step S3.

[0054] Comparative Example 4 This comparative example provides a method for preparing a tear-resistant insulation material for low-voltage power cables, including the following steps: Weigh out 80 parts by weight of polyethylene, 10 parts by weight of maleic anhydride-grafted ethylene-octene copolymer, 5.5 parts by weight of modified basalt fiber, 2 parts by weight of vinyltrimethoxysilane, 0.1 parts by weight of dibutyltin dilaurate, and 0.5 parts by weight of antioxidant 1010, and mix them evenly to obtain a mixture. Melt-blend and extrude the mixture in a twin-screw extruder at a melt-blending temperature of 180°C and a screw speed of 220 rpm to obtain granules. Extrude the granules at 180°C to coat the cable conductor, and then place them in 90°C warm water for crosslinking for 6 hours to obtain the tear-resistant insulation material for low-voltage power cables.

[0055] The preparation method of modified basalt fiber is as follows: S1. Take 10g of basalt fiber and place it in 100mL of ethanol-water mixed solution (ethanol to water volume ratio of 9:1) containing 0.6g of γ-aminopropyltriethoxysilane. Adjust the pH to 4.5 with acetic acid and react at 65℃ for 4h. After the reaction is complete, filter, wash with ethanol, and vacuum dry at 80℃ for 4h to obtain aminated modified basalt fiber.

[0056] S2. Take 10g of aminated modified basalt fiber and 3g of hexamethylene diisocyanate trimer, disperse them in 150ml of DMF, react at 35℃ for 5 hours under nitrogen protection, filter after the reaction is completed, wash with DMF, and vacuum dry at 80℃ for 4 hours to obtain the modified basalt fiber intermediate.

[0057] S3. Take 10g of modified basalt fiber intermediate, add 0.4g of octadecylamine, disperse in 150mL of DMF, react at 40℃ for 3.5h, filter after the reaction is complete, wash with DMF, and vacuum dry at 80℃ for 4h to obtain modified basalt fiber.

[0058] The difference between Comparative Example 4 and Example 1 is that cystamine is not added in the basalt fiber modification step S3.

[0059] Performance testing: The tensile strength and tear strength of the insulation material were tested according to GB / T 2951.11-2008 "General Test Methods for Insulation and Sheath Materials of Cables and Optical Fibers - Part 11: General Test Methods—Thickness and Dimensional Measurements—Mechanical Properties Tests"; the volume resistivity of the insulation material was tested according to GB / T 31838.2-2019 "Dielectric and Resistive Properties of Solid Insulating Materials - Part 2: Resistivity (DC Method)—Volume Resistivity and Volume Resistivity"; and the water absorption rate of the material was tested according to GB / T 2951.13-2008 "General Test Methods for Insulation and Sheath Materials of Cables and Optical Fibers - Part 13: General Test Methods—Density Determination—Water Absorption Test—Shrinkage Test". The test results are shown in the table below.

[0060] Table 1 Performance test results of Examples 1-3 and Comparative Examples 1-4

[0061] As shown in Table 1, the tear-resistant insulation materials for low-voltage power cables prepared in Examples 1-3 of this application exhibit excellent tear resistance, mechanical strength, electrical insulation properties, and long-term service stability. Specifically, Example 1 shows a tear strength of 56.2 kN / m, a tensile strength of 22.5 MPa, and a volume resistivity of 3.3 × 10⁻⁶. 15 The absorbance is Ω·m and the water absorption rate is 0.12%. This application demonstrates that a functional layer containing disulfide bonds is constructed on the surface of basalt fiber through a three-step chemical grafting process, and octadecylamine long-chain alkyl groups are introduced. This achieves a strong bond between the fiber and the matrix, significantly improving tear resistance while maintaining excellent electrical insulation properties, making it suitable for long-term cable service.

[0062] Comparative Example 1 uses unmodified basalt fiber, and its performance is significantly lower than that of Example 1. This indicates that the unmodified fiber and the polyethylene matrix are only bonded by physical interlocking or van der Waals forces, resulting in low interfacial bonding strength. Under tear stress, the fiber is easily pulled out, and the bridging and pull-out effects of the fiber cannot be fully utilized, resulting in poor tear resistance.

[0063] Comparative Example 2 only underwent amination modification without a functional layer, and its performance decreased compared to Example 1. This indicates that only by introducing amino groups with POE-g-MAH through KH550 to form amide bonds to achieve chemical anchoring, although the interfacial bonding is enhanced, the lack of a functional layer to fill interfacial micro-defects and limit crack propagation leads to insufficient tear resistance and long-term stability.

[0064] Comparative Example 3, which did not use octadecylamine, had a tear strength comparable to Example 1, but a water absorption rate as high as 0.41%. This indicates that the long-chain alkyl grafting of octadecylamine can improve the surface hydrophobicity and effectively inhibit the accumulation of water at the fiber-matrix interface. Without octadecylamine, water molecules are more easily adsorbed and penetrate into the micro-defects at the interface, accelerating the initiation and spread of water trees under the action of an electric field. The service stability under long-term humid conditions cannot be guaranteed.

[0065] Comparative Example 4 did not use cystamine, but only octadecylamine. Octadecylamine is a monofunctional end-capping agent, and cannot construct a cross-linked structure by bridging different active isocyanate sites with two amino groups like cystamine. This results in insufficient interfacial bonding strength between the modified basalt fiber and the matrix, and a decrease in tear resistance.

[0066] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A tear resistant insulation compound for low voltage power cables, characterized in that: By weight, it comprises the following components: 60-100 parts of polyethylene, 5-15 parts of maleic anhydride-grafted ethylene-octene copolymer, 3-8 parts of modified basalt fiber, 1.5-2.5 parts of vinyltrimethoxysilane, 0.05-0.15 parts of crosslinking catalyst, and 0.2-0.8 parts of antioxidant.

2. The low-voltage power cable tear-resistant insulation compound according to claim 1, characterized in that: The preparation method of the modified basalt fiber includes the following steps: S1. Basalt fibers are placed in a γ-aminopropyltriethoxysilane solution for amination modification to obtain amination-modified basalt fibers. S2. Aminated modified basalt fiber and hexamethylene diisocyanate trimer are dispersed in DMF and reacted to obtain modified basalt fiber intermediate; S3. The modified basalt fiber intermediate is dispersed in DMF with octadecylamine and cystamine to obtain modified basalt fiber.

3. The low-voltage power cable tear-resistant insulation compound according to claim 2, characterized in that: In step S1, the mass ratio of the basalt fiber to γ-aminopropyltriethoxysilane is 1:0.02 to 0.

10.

4. The low-voltage power cable tear-resistant insulation compound according to claim 2, characterized in that: In step S1, the basalt fiber has a length of 100-500 μm and an aspect ratio of 20-60.

5. The tear-resistant insulation material for low-voltage power cables according to claim 2, characterized in that: In step S2, the mass ratio of the aminated modified basalt fiber to the hexamethylene diisocyanate trimer is 1:0.2 to 0.

4.

6. The tear-resistant insulation material for low-voltage power cables according to claim 2, characterized in that: In step S2, the reaction is carried out under inert gas protection, at a temperature of 10–60°C, and for a time of 2–8 hours.

7. The tear-resistant insulation material for low-voltage power cables according to claim 2, characterized in that: In step S3, the mass ratio of the modified basalt fiber intermediate to octadecylamine and cystamine is 1:0.02-0.06:0.08-0.

2.

8. The tear-resistant insulation material for low-voltage power cables according to claim 2, characterized in that: In step S3, the reaction temperature is 20–60°C and the reaction time is 1–6 h.

9. The tear-resistant insulation material for low-voltage power cables according to claim 1, characterized in that: The polyethylene is a long-chain branched linear low-density polyethylene; the crosslinking catalyst is dibutyltin dilaurate; and the antioxidant is one or more of antioxidant 1010, antioxidant 168, and antioxidant 1076.

10. A method for preparing a tear-resistant insulating material for low-voltage power cables as described in any one of claims 1-9, characterized in that: Includes the following steps: S1. Weigh each raw material component according to the weight parts and mix them evenly to obtain a mixture; S2. The mixture is melt-blended and extruded in a twin-screw extruder to obtain granules; S3. After extruding the granulated material and coating it onto the cable conductor, it is placed in warm water for cross-linking to obtain the tear-resistant insulation material for low-voltage power cables.

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