High-tear-resistance irradiation crosslinking low-smoke halogen-free flame-retardant polyolefin insulating material and preparation method thereof

Abstract

The invention relates to a high-tear-resistance irradiation crosslinking low-smoke halogen-free flame-retardant polyolefin insulating material and a preparation method thereof. The high-tear-resistance irradiation crosslinking low-smoke halogen-free flame-retardant polyolefin insulating material comprises the following components in parts by mass: 45-55 parts of ethylene-vinyl acetate, 10-15 parts of metallocene linear low-density polyethylene, 15-20 parts of an elastomer, 8-12 parts of a compatilizer, 125-140 parts of a flame retardant, 1-3 parts of an assistant crosslinker, 2.5-4 parts of an antioxidant and 2-4 parts of a lubricant. Through the synergistic effect of the assistant crosslinking agent and the antioxidant, the tear resistance of the material is remarkably improved while the long-term thermo-oxidative aging performance is ensured, and the obtained insulating material has excellent tear resistance, good thermal aging resistance stability and electrical insulation performance. The invention relates to a high-tear-resistance irradiation crosslinking low-smoke halogen-free flame-retardant polyolefin insulating material and a preparation method thereof. The high-tear-resistance irradiation crosslinking low-smoke halogen-free flame-retardant polyolefin insulating material comprises the following components in parts by mass: 45-55 parts of ethylene-vinyl acetate, 10-15 parts of metallocene linear low-density polyethylene, 15-20 parts of an elastomer, 8-12 parts of a compatilizer, 125-140 parts of a flame retardant, 1-3 parts of an assistant crosslinker, 2.5-4 parts of an antioxidant and 2-4 parts of a lubricant. Through the synergistic effect of the assistant crosslinking agent and the antioxidant, the tear resistance of the material is remarkably improved while the long-term thermo-oxidative aging performance is ensured, and the obtained insulating material has excellent tear resistance, good thermal aging resistance stability and electrical insulation performance.

Description

Technical Field

[0001] This application relates to the field of polymer insulating materials, and in particular to a high tear-resistant, radiation-crosslinked, low-smoke, halogen-free flame-retardant polyolefin insulating material and its preparation method. Background Technology

[0002] Irradiated cross-linked low-smoke halogen-free flame-retardant polyolefin insulation materials are widely used in electrical systems in rail transportation, new energy vehicles, ships, and power transmission due to their excellent heat resistance, flame retardancy, and electrical insulation properties. With the increasing integration of systems, insulation materials face more demanding service environments: on the one hand, they must withstand the high-temperature shock caused by large current switching and the long-term thermo-oxidative aging; on the other hand, during installation, they often need to pass through narrow holes or contact sharp structures, placing higher demands on the material's tear resistance. In current material systems, irradiated cross-linked polyolefins are commonly used for heat resistance grades of 125℃ and 150℃, while silicone rubber is chosen for higher temperature resistance grades. However, silicone rubber is expensive, not resistant to chemical solvents, and has poor tear resistance, making it difficult to meet the long-term reliable operation requirements under complex working conditions.

[0003] While irradiation crosslinking can improve the heat resistance and mechanical strength of materials, its effects on tensile strength and tear strength are not synchronized. Tear resistance depends more on the energy dissipation capacity of molecular chains at the crack tip, and a highly crosslinked network restricts the mobility of molecular chains, making the material more brittle than tough. Furthermore, high-dose irradiation can induce molecular chain breakage, further impairing tear strength. Therefore, excellent tear resistance requires a balance between the degree of crosslinking and toughness.

[0004] In irradiation crosslinking systems, crosslinking aids are often added to improve crosslinking efficiency. However, excessive use or excessively high irradiation doses can lead to overly dense crosslinking networks, severely reducing tear resistance. Meanwhile, insulation materials for high-voltage electrical systems typically need to meet long-term thermo-oxidative aging requirements of over 3000 hours, necessitating the addition of numerous antioxidants. However, traditional hindered phenolic primary antioxidants inhibit crosslinking, forcing an increase in irradiation dose, exacerbating chain breakage, and further weakening tear resistance.

[0005] In the prior art, although there are published patents involving tear-resistant halogen-free flame-retardant materials, they are either mainly composed of metallocene polyethylene, resulting in high hardness and low tear resistance, or they improve compatibility by introducing polar rubber, but significantly reduce the insulation volume resistivity, affecting electrical safety, and none of them provide effective actual tear resistance test data.

[0006] Therefore, developing an irradiated crosslinked low-smoke halogen-free flame-retardant polyolefin insulation material that combines excellent tear resistance, meets long-term thermo-oxidative aging requirements, and has high electrical safety is of great practical significance. Summary of the Invention

[0007] To improve the tear resistance of insulating materials, this application provides a high tear-resistant irradiated crosslinked low-smoke halogen-free flame-retardant polyolefin insulating material and its preparation method.

[0008] In the first aspect, this application provides a high tear-resistant, radiation-crosslinked, low-smoke, halogen-free flame-retardant polyolefin insulation material, which adopts the following technical solution: A high tear-resistant, radiation-crosslinked, low-smoke, halogen-free, flame-retardant polyolefin insulation material, comprising the following components in parts by weight: 45-55 parts of ethylene-vinyl acetate, 10-15 parts of metallocene linear low-density polyethylene, 15-20 parts of elastomer, 8-12 parts of compatibilizer, 125-140 parts of flame retardant, 1-3 parts of crosslinking agent, 2.5-4 parts of antioxidant, and 2-4 parts of lubricant.

[0009] By adopting the above technical solution, ethylene-vinyl acetate serves as the basic matrix, providing flexibility and processability. Metallocene linear low-density polyethylene enhances the system's heat resistance and electrical insulation. Elastomers strengthen tear resistance and low-temperature toughness. The polyolefin matrix formed by these three components takes into account both the basic mechanical properties and core insulation requirements of the insulation material. The synergistic ratio of each component improves the contradictions between crosslinking degree and tear resistance, thermo-oxidative aging and crosslinking efficiency, and flame retardancy and mechanical properties in existing technologies. This allows the insulation material to simultaneously meet the requirements of high tear resistance, radiation crosslinking, low-smoke halogen-free flame retardancy, and long-term thermo-oxidative aging.

[0010] Preferably, the vinyl acetate monomer content in the ethylene-vinyl acetate is 18-40 wt%, and the melt mass flow rate is 2.0-6.0 g / 10 min (190℃ / 2.16 kg).

[0011] By adopting the above technical solution, the content of vinyl acetate monomer in ethylene-vinyl acetate is limited to the above range, ensuring that the molecular chain has sufficient polarity to anchor a large amount of inorganic flame retardant, improving the dispersibility of filler, and reducing the phenomenon of excessive vinyl acetate causing a decrease in the heat resistance of insulating materials. At the same time, controlling the melt mass flow rate within the above range ensures suitable fluidity during mixing and extrusion. The above ethylene-vinyl acetate can efficiently carry flame retardants and has good compatibility with metallocene linear low-density polyethylene and elastomers.

[0012] Preferably, the metallocene linear low-density polyethylene has a density of 0.916-0.926 g / cm³. 3 The melt mass flow rate is 1.0-4.0 g / 10 min (190℃ / 2.16 kg).

[0013] By adopting the above technical solution, metallocene linear low-density polyethylene has a narrow molecular weight distribution and a uniform comonomer distribution. The density in the above range is within the linear low-density range, which ensures that the material has a certain degree of crystallinity to maintain heat resistance and mechanical strength, while maintaining good flexibility and reducing the phenomenon of the material becoming too rigid and brittle. The melt mass flow rate in the above range enables it to provide structural support in the blend system, and will not affect the dispersion of flame retardants and other additives due to excessive viscosity.

[0014] Preferably, the elastomer is a polyolefin elastomer with a density of 0.86-0.90 g / cm³. 3 The melt flow rate is 1.0-3.0 g / 10 min (190℃ / 2.16 kg).

[0015] By adopting the above technical solution, the preferred elastomer has a high content of comonomers and obvious rubber phase characteristics within the above density range, which can endow the material with high tear resistance. When subjected to tear stress, the dispersed phase of the elastomer can induce crazes and absorb energy, effectively passivating the crack tip and preventing the crack from propagating rapidly. The preferred melt index is within the above range, which can be well dispersed in the matrix and improve the overall stability of the system.

[0016] Preferably, the compatibilizer includes any one of polyolefin elastomer grafted with maleic anhydride, polyethylene grafted with maleic anhydride, and ethylene propylene diene monomer (EPDM) rubber grafted with maleic anhydride, with a grafting rate of 0.6-1.2%.

[0017] By adopting the above technical solutions, the compatibilizers all have excellent compatibility. The grafted maleic anhydride polar groups can interact with or form hydrogen bonds with the hydroxyl groups on the surface of the inorganic flame retardant, which significantly reduces the interfacial tension between the two phases, thereby enabling the flame retardant to be uniformly dispersed and eliminating interfacial defects between the filler and the matrix.

[0018] Preferably, the flame retardant comprises any one or a mixture of aluminum hydroxide and magnesium hydroxide, and the D50 of the flame retardant is 0.7-1.5 μm.

[0019] By adopting the above technical solution, the flame retardant has a small particle size, which helps to disperse evenly under high filling amount, avoiding stress concentration and mechanical property deterioration caused by large particles. In addition, the microparticles can fully combine with the matrix resin under the synergistic effect of the compatibilizer, which improves the flame retardant performance while reducing the negative impact on the tear resistance of the material.

[0020] Preferably, the crosslinking agent comprises a hydroxyl-terminated hyperbranched polyester with 10-25 hydroxyl groups / mol and a molecular weight of 1000-3000 g / mol.

[0021] By adopting the above technical solution, hyperbranched molecules initiate a local but reasonably distributed cross-linked network from a single point, avoiding over-crosslinked hard spots caused by local aggregation of small molecules, forming a non-uniform network structure. After cross-linking, its flexible core, as a nano-elastomer phase, can effectively absorb and dissipate tearing energy and inhibit crack propagation. At the same time, its macromolecular characteristics eliminate the hidden dangers of migration and volatilization of small molecule additives, improving the long-term stability of the product.

[0022] Preferably, the antioxidant comprises a primary antioxidant, a secondary antioxidant, and a metal ion passivator, wherein the mass ratio of the primary antioxidant, the secondary antioxidant, and the metal ion passivator is (1-1.5):(1.5-2.5):(0.2-0.5).

[0023] By adopting the above technical solution, the primary antioxidant is preferably HP136, which can effectively capture free radicals and protect the integrity of the molecular chain. The secondary antioxidant is preferably a combination of 168 and 412S, which can provide long-term thermal stability protection in different temperature ranges. The metal ion passivator is preferably benzotriazole, which forms a protective film by chelating with copper ions, inhibiting the catalytic aging of the insulating material by the copper conductor, and its structure does not contain strong free radical capturing groups, thus having little impact on crosslinking.

[0024] Secondly, this application provides a method for preparing a high tear-resistant, radiation-crosslinked, low-smoke, halogen-free flame-retardant polyolefin insulation material, employing the following technical solution: A method for preparing a high tear-resistant, radiation-crosslinked, low-smoke, halogen-free flame-retardant polyolefin insulation material includes the following steps: Weigh out various materials and put them into an internal mixer for mixing. After the mixing is completed, discharge the material and add it to a twin-screw extruder for mixing. After mixing, extrude and pelletize the material using a single screw extruder. Finally, dry and cool the material to obtain the material particles, namely, high tear resistance, radiation crosslinking, low smoke, halogen-free flame retardant polyolefin insulation material.

[0025] Preferably, the thickness of the material particles is 2-4 mm.

[0026] By adopting the above technical solution, the thickness of the material particles is limited to the above range. In the subsequent irradiation crosslinking, high-energy rays can penetrate the particles uniformly, so that the internal molecular chains can achieve uniform crosslinking. This reduces the stress concentration points formed by uneven crosslinking, so that the prepared insulation material has the same tear resistance and heat resistance. At the same time, particles of this thickness are not easy to stick together, have good storage stability, and are easy to feed in subsequent processing.

[0027] In summary, this application includes at least one of the following beneficial technical effects: This invention innovatively introduces hydroxyl-terminated hyperbranched polyester as a co-crosslinking agent, replacing traditional small-molecule multifunctional co-crosslinking agents such as TMPTMA, TAIC, and ethylene glycol dimethacrylate. During the irradiation crosslinking process, the hydroxyl-terminated hyperbranched polyester molecules can initiate a localized but more rationally distributed crosslinking network from a single point, effectively avoiding excessive crosslinking caused by local aggregation of small molecules. It also fundamentally eliminates migration and volatilization problems, improving the long-term stability of the product. After crosslinking, the flexible core of the hydroxyl-terminated hyperbranched polyester, as a nano-elastomer phase in the polymer network, can effectively absorb and dissipate energy, inhibiting crack propagation. Therefore, while significantly improving the degree of crosslinking, it does not sacrifice or even improves the tear resistance of the material, breaking the constraint that traditional small molecules "become brittle after crosslinking."

[0028] This innovative approach utilizes HP136, a carbon-center free radical scavenger, to replace traditional hindered phenolic, aromatic amine, hydroxylamine, and hindered amine primary antioxidants. This reduces the decrease in crosslinking efficiency and degree of crosslinking caused by the primary antioxidant capturing alkyl free radicals during radiation crosslinking, as well as the consumption of antioxidants. This eliminates the need to further increase the irradiation dose to enhance crosslinking, leading to more macromolecular chain breakage side reactions and consuming even more antioxidants, thus reducing tear resistance and long-term thermo-oxidative aging performance. By combining auxiliary antioxidants at different temperature ranges, and synergistically using benzotriazole metal ion passivators, the long-term thermo-oxidative aging performance requirements of the material are met while further minimizing the impact on radiation crosslinking, inhibiting degradation reactions, and allowing the generated free radicals to be more effectively used in the crosslinking reaction, thus reducing the impact on the material's tear strength. Detailed Implementation

[0029] The present application will be further described in detail below with reference to the embodiments: Raw material description: All raw materials in the examples are commercially available; ethylene-vinyl acetate was purchased from Yangzi Petrochemical BASF, model 6110MC; metallocene linear low-density polyethylene was purchased from ExxonMobil Chemical, model 3518; elastomer was purchased from Mitsui Chemicals, model DF810; lubricant was purchased from Silike Technology Co., Ltd., model LYSI-301. Example 1

[0030] Preparation of high tear-resistant, radiation-crosslinked, low-smoke, halogen-free flame-retardant polyolefin insulation material: Prepare materials according to the following mass proportions: The composition includes 55 parts ethylene-vinyl acetate, 15 parts metallocene linear low-density polyethylene, 20 parts elastomer, 10 parts compatibilizer, 130 parts flame retardant, 1.5 parts co-crosslinking agent, 3 parts antioxidant, and 3 parts lubricant. The compatibilizer was purchased from Sirida Plastics Co., Ltd. (model TRD-201LM); the flame retardant was purchased from Zhongchao New Materials Co., Ltd. (model 701); the co-crosslinking agent was purchased from Wuhan Hyperbranched Resin Technology Co., Ltd. (model H102); and the antioxidants include primary antioxidant (HP136), secondary antioxidants (168 and 412S), and metal passivator (benzotriazole, CAS number 95-14-7). The mass ratio of HP136, 168, 412S, and benzotriazole is 1:0.5:1.2:0.3.

[0031] Weigh out all materials and set them aside. Put them into a mixer and set the mixing temperature to 160℃ and the mixing time to 15 minutes. After mixing, discharge the material at a temperature of 155℃. The temperature of the material after mixing is 80℃ after feeding through a twin-cone feeder. Then feed the material into a twin-screw extruder for mixing. The temperature of each zone during mixing is 75℃, 75℃, 80℃, 80℃, 80℃, 80℃, and 80℃ respectively. The average speed of the twin screws is 230 rpm. Then extrude and pelletize the material through a single screw. The temperature of each zone during extrusion is 100℃, 110℃, 120℃, 125℃, and 130℃ respectively. The screw speed is 130 rpm and the pelletizer speed is 190 rpm. Finally, after drying and cooling with hot air in a fluidized bed, material particles with a thickness of 2 mm are obtained, which is a high tear-resistant, radiation-crosslinked, low-smoke, halogen-free flame-retardant polyolefin insulation material. Example 2

[0032] Preparation of high tear-resistant, radiation-crosslinked, low-smoke, halogen-free flame-retardant polyolefin insulation material: Prepare materials according to the following mass proportions: The composition includes 55 parts ethylene-vinyl acetate, 20 parts metallocene linear low-density polyethylene, 15 parts elastomer, 10 parts compatibilizer, 130 parts flame retardant, 1.5 parts co-crosslinking agent, 3 parts antioxidant, and 3 parts lubricant. The compatibilizer was purchased from Sirida Plastics Co., Ltd., model TRD-200P; the flame retardant was purchased from Shendao, model S-6; the co-crosslinking agent was purchased from Wuhan Hyperbranched Resin Technology Co., Ltd., model H102; the antioxidants include primary antioxidant (HP136), secondary antioxidants (168 and 412S), and metal passivator (benzotriazole), with a mass ratio of HP136, 168, 412S, and benzotriazole of 0.7:0.5:1.5:0.3.

[0033] Weigh out all materials and put them into a mixer. Set the mixing temperature to 160℃ and the mixing time to 15 minutes. After mixing, discharge the material at a temperature of 165℃. The temperature of the material after mixing is 100℃ via a twin-cone feeder. Then, feed the material into a twin-screw extruder for mixing. The temperatures of each zone during mixing are 75℃, 75℃, 80℃, 80℃, 80℃, 80℃, and 80℃ respectively. The average speed of the twin screws is 230 rpm. Then, extrude the material into pellets using a single screw. The temperatures of each zone during extrusion are 100℃, 110℃, 120℃, 125℃, and 130℃ respectively. The screw speed is 130 rpm, and the pelletizer speed is 190 rpm. Finally, after hot air drying and cooling in a fluidized bed, material particles with a thickness of 4 mm are obtained, which yields a high tear-resistant, radiation-crosslinked, low-smoke, halogen-free flame-retardant polyolefin insulation material. Example 3

[0034] Preparation of high tear-resistant, radiation-crosslinked, low-smoke, halogen-free flame-retardant polyolefin insulation material: Prepare materials according to the following mass proportions: The composition includes 55 parts ethylene-vinyl acetate, 15 parts metallocene linear low-density polyethylene, 20 parts elastomer, 10 parts compatibilizer, 130 parts flame retardant, 1.5 parts co-crosslinking agent, 3 parts antioxidant, and 3 parts lubricant. The compatibilizer was purchased from Sirida Plastics Co., Ltd., model TRD-201LM; the flame retardant was purchased from Zhongchao New Materials Co., Ltd., model 701; the co-crosslinking agent was purchased from Wuhan Hyperbranched Resin Technology Co., Ltd., model H103; the antioxidants include primary antioxidant (HP136), secondary antioxidants (168 and 412S), and metal passivator (benzotriazole), with a mass ratio of HP136, 168, 412S, and benzotriazole of 1:0.5:1.2:0.3.

[0035] Weigh out all materials and put them into a mixer. Set the mixing temperature to 160℃ and the mixing time to 15 minutes. After mixing, discharge the material at a temperature of 160℃. The temperature of the material after mixing is 90℃ via a twin-cone feeder. Then, feed the material into a twin-screw extruder for mixing. The temperatures of each zone during mixing are 75℃, 75℃, 80℃, 80℃, 80℃, 80℃, and 80℃ respectively. The average rotation speed of the twin screws is 230 rpm. Then, extrude the material into pellets using a single screw. The temperatures of each zone during extrusion are 100℃, 110℃, 120℃, 125℃, and 130℃ respectively. The screw rotation speed is 130 rpm, and the pelletizer rotation speed is 190 rpm. Finally, after drying and cooling with hot air in a fluidized bed, material particles with a thickness of 3 mm are obtained, which yields a high tear-resistant, radiation-crosslinked, low-smoke, halogen-free, flame-retardant polyolefin insulation material. Example 4

[0036] Preparation of high tear-resistant, radiation-crosslinked, low-smoke, halogen-free flame-retardant polyolefin insulation material: Prepare materials according to the following mass proportions: The composition includes 50 parts ethylene-vinyl acetate, 15 parts metallocene linear low-density polyethylene, 20 parts elastomer, 10 parts compatibilizer, 130 parts flame retardant, 2 parts co-crosslinking agent, 4 parts antioxidant, and 3 parts lubricant. The compatibilizer was purchased from Sirida Plastics Co., Ltd., model TRD-201LM; the flame retardant was purchased from Zhongchao New Materials Co., Ltd., model 701; the co-crosslinking agent was purchased from Wuhan Hyperbranched Resin Technology Co., Ltd., model H102; the antioxidant includes primary antioxidant (HP136), secondary antioxidants (168 and 412S), and metal passivator (benzotriazole), with a mass ratio of HP136, 168, 412S, and benzotriazole of 1:1:1.5:0.5.

[0037] Weigh out all materials and put them into a mixer. Set the mixing temperature to 160℃ and the mixing time to 15 minutes. After mixing, discharge the material at a temperature of 160℃. The temperature of the material after mixing is 90℃ via a twin-cone feeder. Then, feed the material into a twin-screw extruder for mixing. The temperatures of each zone during mixing are 75℃, 75℃, 80℃, 80℃, 80℃, 80℃, and 80℃ respectively. The average rotation speed of the twin screws is 230 rpm. Then, extrude the material into pellets using a single screw. The temperatures of each zone during extrusion are 100℃, 110℃, 120℃, 125℃, and 130℃ respectively. The screw rotation speed is 130 rpm, and the pelletizer rotation speed is 190 rpm. Finally, after drying and cooling with hot air in a fluidized bed, material particles with a thickness of 3 mm are obtained, which yields a high tear-resistant, radiation-crosslinked, low-smoke, halogen-free, flame-retardant polyolefin insulation material. Example 5

[0038] Preparation of high tear-resistant, radiation-crosslinked, low-smoke, halogen-free flame-retardant polyolefin insulation material: Prepare materials according to the following mass proportions: The composition includes 50 parts ethylene-vinyl acetate, 15 parts metallocene linear low-density polyethylene, 20 parts elastomer, 10 parts compatibilizer, 130 parts flame retardant, 2 parts co-crosslinking agent, 4 parts antioxidant, and 3 parts lubricant. The compatibilizer was purchased from Sirida Plastics Co., Ltd., model TRD-201LM; the flame retardant was purchased from Zhongchao New Materials Co., Ltd., model 701; the co-crosslinking agent was purchased from Wuhan Hyperbranched Resin Technology Co., Ltd., model H103; the antioxidant includes primary antioxidant (HP136), secondary antioxidants (168 and 412S), and metal passivator (benzotriazole), with a mass ratio of HP136, 168, 412S, and benzotriazole of 1.5:0.5:1.5:0.5.

[0039] Weigh out all materials and put them into a mixer. Set the mixing temperature to 160℃ and the mixing time to 15 minutes. After mixing, discharge the material at a temperature of 160℃. The temperature of the material after mixing is 90℃ via a twin-cone feeder. Then, feed the material into a twin-screw extruder for mixing. The temperatures of each zone during mixing are 75℃, 75℃, 80℃, 80℃, 80℃, 80℃, and 80℃ respectively. The average rotation speed of the twin screws is 230 rpm. Then, extrude the material into pellets using a single screw. The temperatures of each zone during extrusion are 100℃, 110℃, 120℃, 125℃, and 130℃ respectively. The screw rotation speed is 130 rpm, and the pelletizer rotation speed is 190 rpm. Finally, after drying and cooling with hot air in a fluidized bed, material particles with a thickness of 3 mm are obtained, which yields a high tear-resistant, radiation-crosslinked, low-smoke, halogen-free, flame-retardant polyolefin insulation material.

[0040] Comparative Example 1 Preparation of high tear-resistant, radiation-crosslinked, low-smoke, halogen-free flame-retardant polyolefin insulation material: Prepare materials according to the following mass proportions: 50 parts of ethylene-vinyl acetate, 15 parts of metallocene linear low-density polyethylene, 20 parts of elastomer, 10 parts of compatibilizer, 130 parts of flame retardant, 1.5 parts of crosslinking agent, 3 parts of antioxidant, and 3 parts of lubricant; wherein, the compatibilizer was purchased from Sirida Plastics Co., Ltd., model TRD-201LM; the flame retardant was purchased from Zhongchao New Materials Co., Ltd., model 701; the crosslinking agent was purchased from Hunan Minhe Chemical Co., Ltd., model TAIC; the antioxidants include primary antioxidant (1010) and secondary antioxidants (168 and 1024), and the mass ratio of 1010, 168 and 1024 is 1:1.5:0.5.

[0041] Weigh out all materials and put them into a mixer. Set the mixing temperature to 160℃ and the mixing time to 15 minutes. After mixing, discharge the material at a temperature of 160℃. The temperature of the material after mixing is 90℃ via a twin-cone feeder. Then, feed the material into a twin-screw extruder for mixing. The temperatures of each zone during mixing are 75℃, 75℃, 80℃, 80℃, 80℃, 80℃, and 80℃ respectively. The average rotation speed of the twin screws is 230 rpm. Then, extrude the material into pellets using a single screw. The temperatures of each zone during extrusion are 100℃, 110℃, 120℃, 125℃, and 130℃ respectively. The screw rotation speed is 130 rpm, and the pelletizer rotation speed is 190 rpm. Finally, after drying and cooling with hot air in a fluidized bed, material particles with a thickness of 3 mm are obtained, which yields a high tear-resistant, radiation-crosslinked, low-smoke, halogen-free, flame-retardant polyolefin insulation material.

[0042] Comparative Example 2 Preparation of high tear-resistant, radiation-crosslinked, low-smoke, halogen-free flame-retardant polyolefin insulation material: Prepare materials according to the following mass proportions: The composition includes 50 parts ethylene-vinyl acetate, 15 parts metallocene linear low-density polyethylene, 20 parts elastomer, 10 parts compatibilizer, 130 parts flame retardant, 1.5 parts co-crosslinking agent, 3 parts antioxidant, and 3 parts lubricant. The compatibilizer was purchased from Sirida Plastics Co., Ltd., model TRD-201LM; the flame retardant was purchased from Zhongchao New Materials Co., Ltd., model 701; the co-crosslinking agent was purchased from Hunan Minhe Chemical Co., Ltd., model TAIC; the antioxidants include primary antioxidant (HP136), secondary antioxidants (168 and 412S), and metal passivator (benzotriazole), with a mass ratio of HP136, 168, 412S, and benzotriazole of 1:0.5:1:0.5.

[0043] Weigh out all materials and put them into a mixer. Set the mixing temperature to 160℃ and the mixing time to 15 minutes. After mixing, discharge the material at a temperature of 160℃. The temperature of the material after mixing is 90℃ via a twin-cone feeder. Then, feed the material into a twin-screw extruder for mixing. The temperatures of each zone during mixing are 75℃, 75℃, 80℃, 80℃, 80℃, 80℃, and 80℃ respectively. The average rotation speed of the twin screws is 230 rpm. Then, extrude the material into pellets using a single screw. The temperatures of each zone during extrusion are 100℃, 110℃, 120℃, 125℃, and 130℃ respectively. The screw rotation speed is 130 rpm, and the pelletizer rotation speed is 190 rpm. Finally, after drying and cooling with hot air in a fluidized bed, material particles with a thickness of 3 mm are obtained, which yields a high tear-resistant, radiation-crosslinked, low-smoke, halogen-free, flame-retardant polyolefin insulation material.

[0044] Comparative Example 3 Preparation of high tear-resistant, radiation-crosslinked, low-smoke, halogen-free flame-retardant polyolefin insulation material: Prepare materials according to the following mass proportions: 50 parts of ethylene-vinyl acetate, 15 parts of metallocene linear low-density polyethylene, 20 parts of elastomer, 10 parts of compatibilizer, 130 parts of flame retardant, 2 parts of crosslinking agent, 3 parts of antioxidant, and 3 parts of lubricant; wherein, the compatibilizer was purchased from Sirida Plastics Co., Ltd., model TRD-201LM; the flame retardant was purchased from Zhongchao New Materials Co., Ltd., model 701; the crosslinking agent was purchased from Wuhan Hyperbranched Resin Technology Co., Ltd., model H103; the antioxidants include primary antioxidant (1010) and secondary antioxidants (168 and 1024), and the mass ratio of 1010, 168 and 1024 is 1:1.5:0.5.

[0045] Weigh out all materials and put them into a mixer. Set the mixing temperature to 160℃ and the mixing time to 15 minutes. After mixing, discharge the material at a temperature of 160℃. The temperature of the material after mixing is 90℃ via a twin-cone feeder. Then, feed the material into a twin-screw extruder for mixing. The temperatures of each zone during mixing are 75℃, 75℃, 80℃, 80℃, 80℃, 80℃, and 80℃ respectively. The average rotation speed of the twin screws is 230 rpm. Then, extrude the material into pellets using a single screw. The temperatures of each zone during extrusion are 100℃, 110℃, 120℃, 125℃, and 130℃ respectively. The screw rotation speed is 130 rpm, and the pelletizer rotation speed is 190 rpm. Finally, after drying and cooling with hot air in a fluidized bed, material particles with a thickness of 3 mm are obtained, which yields a high tear-resistant, radiation-crosslinked, low-smoke, halogen-free, flame-retardant polyolefin insulation material.

[0046] Performance testing The following performance tests were performed on the samples from Examples 1-5 and Comparative Examples 1-3: (1) Main performance Using GB / T 1040.3 as the test reference, the tensile strength and elongation at break of the specimens were tested respectively. Each specimen was tested 3 times, and the average value was taken. The test results were filled in Table 1. Using GB / T 2951.21 as the testing reference, the thermal extension of the samples was tested. Each sample was tested 3 times, and the average value was taken. The test results were filled in Table 1. Using LV216-2 as the testing reference, the tear strength of the samples was tested. Each sample was tested 3 times, and the average value was taken. The test results were recorded in Table 1.

[0047] (2) Typical performance characteristics of automotive high voltage wires (EV-YJ-125 AC1000 / DC1500V 25mm) 2 ) The thermal extension of the samples was tested. Each sample was tested 3 times, the average value was taken, and the test results were recorded in Table 2. Using LV216-2 as the testing reference, the tear strength of the samples was tested. Each sample was tested 3 times, and the average value was taken. The test results were recorded in Table 2.

[0048] (3) 150℃×10d thermo-oxidative aging Using ISO 6722-1 as the testing reference, the change rate of tensile strength and the change rate of elongation at break of the specimens were tested respectively. Each specimen was tested 3 times, and the test results were recorded in Table 3. After the test, the specimen surface was observed to see if there was any winding crack, and the results were recorded in Table 3.

[0049] Table 1. Test results of key performance characteristics of Examples 1-5 and Comparative Examples 1-3

[0050] Table 2 Test results of key performance characteristics of typical automotive high-voltage wire products in Examples 1-5 and Comparative Examples 1-3

[0051] Table 3 Test results of main performance characteristics of Examples 1-5 and Comparative Examples 1-3 under thermo-oxidative aging at 150℃ for 10 days

[0052] This specific embodiment is merely an explanation of this application and is not intended to limit it. Based on the above description, those skilled in the art can make various changes and modifications without departing from the technical concept of this application. The technical scope of this application is not limited to the contents of the specification but must be determined according to the scope of the claims.

Claims

1. A high tear-resistant, radiation-crosslinked, low-smoke, halogen-free flame-retardant polyolefin insulating material, characterized in that: The components include the following parts by mass: 45-55 parts of ethylene-vinyl acetate, 10-15 parts of metallocene linear low-density polyethylene, 15-20 parts of elastomer, 8-12 parts of compatibilizer, 125-140 parts of flame retardant, 1-3 parts of crosslinking agent, 2.5-4 parts of antioxidant, and 2-4 parts of lubricant.

2. The high tear-resistant, radiation-crosslinked, low-smoke, halogen-free flame-retardant polyolefin insulation material according to claim 1, characterized in that: The ethylene-vinyl acetate monomer content in the ethylene-vinyl acetate is 18-40 wt%, and the melt mass flow rate is 2.0-6.0 g / 10 min (190℃ / 2.16 kg).

3. The high tear-resistant, radiation-crosslinked, low-smoke, halogen-free flame-retardant polyolefin insulation material according to claim 1, characterized in that: The density of the metallocene linear low-density polyethylene is 0.916-0.926 g / cm³. 3 The melt mass flow rate is 1.0-4.0 g / 10 min (190℃ / 2.16 kg).

4. The high tear-resistant, radiation-crosslinked, low-smoke, halogen-free flame-retardant polyolefin insulation material according to claim 1, characterized in that: The elastomer is a polyolefin elastomer with a density of 0.86-0.90 g / cm³. 3 The melt flow rate is 1.0-3.0 g / 10 min (190℃ / 2.16 kg).

5. The high tear-resistant, radiation-crosslinked, low-smoke, halogen-free flame-retardant polyolefin insulation material according to claim 1, characterized in that: The compatibilizer includes any one of polyolefin elastomer grafted with maleic anhydride, polyethylene grafted with maleic anhydride, and ethylene propylene diene monomer (EPDM) rubber grafted with maleic anhydride, with a grafting rate of 0.6-1.2%.

6. The high tear-resistant, radiation-crosslinked, low-smoke, halogen-free flame-retardant polyolefin insulation material according to claim 1, characterized in that: The flame retardant includes any one or a mixture of aluminum hydroxide and magnesium hydroxide, and the D50 of the flame retardant is 0.7-1.5 μm.

7. The high tear-resistant, radiation-crosslinked, low-smoke, halogen-free flame-retardant polyolefin insulation material according to claim 1, characterized in that: The crosslinking agent comprises a hydroxyl-terminated hyperbranched polyester with 10-25 hydroxyl groups / mol and a molecular weight of 1000-3000 g / mol.

8. The high tear-resistant, radiation-crosslinked, low-smoke, halogen-free flame-retardant polyolefin insulation material according to claim 1, characterized in that: The antioxidant comprises a primary antioxidant, a secondary antioxidant, and a metal ion passivator, wherein the mass ratio of the primary antioxidant, the secondary antioxidant, and the metal ion passivator is (1-1.5):(1.5-2.5):(0.2-0.5).

9. A high tear-resistant, radiation-crosslinked, low-smoke, halogen-free flame-retardant polyolefin insulating material as described in any one of claims 1-8, characterized in that: Includes the following steps: Weigh out various materials and put them into an internal mixer for mixing. After the mixing is completed, discharge the material and add it to a twin-screw extruder for mixing. After mixing, extrude and pelletize the material using a single screw extruder. Finally, dry and cool the material to obtain the material particles, namely, high tear resistance, radiation crosslinking, low smoke, halogen-free flame retardant polyolefin insulation material.

10. The method for preparing a high tear-resistant, radiation-crosslinked, low-smoke, halogen-free flame-retardant polyolefin insulation material according to claim 9, characterized in that: The thickness of the material particles is 2-4 mm.

Images