A water treeing resistant polyethylene insulation material, its preparation method and use

Abstract

The application provides an anti-water-treeing polyethylene insulating material and a preparation method and application thereof, and belongs to the technical field of high polymer materials. Through cooperation of different components in the composite crosslinking agent, the crosslinking degree can be within a reasonable range under the condition that the temperature is 170-190 DEG C during extrusion of the cable, thereby affecting the crystallinity, controlling the ratio of the crosslinking degree and the crystallinity of the insulating material to be 1.8-2.1, and endowing the insulating material with excellent anti-water-treeing performance when the crosslinking degree and the crystallinity of the cable insulating layer reach a certain degree. Moreover, the raw material of the application contains a surface-modified silicon dioxide material, which has good dispersibility and also participates in crosslinking, can form a network structure between particles, prevents water from penetrating, and effectively prevents growth and diffusion of water trees.

Description

Technical Field

[0001] This invention relates to the field of polymer materials technology, and in particular to a water-tree resistant polyethylene insulation material, its preparation method, and its application. Background Technology

[0002] Polyethylene (PE) resin is widely used in power cable insulation. Currently, almost all medium-voltage power cables ranging from 6 to 35kV use cross-linked polyethylene (XLPE) insulation. When cables operate in humid environments for extended periods, the combination of an electric field and water can cause dendritic discharge channels within the cable, a phenomenon known as water treeing. This leads to insulation breakdown in a short time and is a major cause of cable damage. Cables manufactured using water-tree resistant XLPE insulation can significantly extend the lifespan of power infrastructure cables, increasing it from 20 to 40 years, which is particularly important for applications in humid environments such as offshore wind power and rail transportation.

[0003] There is considerable domestic research on the formation mechanism and influencing factors of water trees in cables. It is generally believed that the formation of water-containing microporous structures is due to the permeation of water molecules, which then leads to the breakage of polymer molecular chains under the influence of an electric field, resulting in water tree formation. Another mechanism suggests that water tree formation is a chemical reaction theory; under the influence of an electric field, water is ionized into free radicals, which then react with the polymer, leading to oxidative degradation of the material and the formation of water trees. Polyethylene is a crystalline polymer, but its crystallinity decreases after cross-linking, making it more susceptible to water tree formation.

[0004] Patent CN116589774A discloses a water-tree resistant cable insulation material and its preparation method. A graftable antioxidant containing hydrophilic polar groups is melt-grafted onto a low-density polyethylene macromolecular chain. The hydrophilic groups adsorb water, slowing down the migration and diffusion of water in the insulation, and increasing the crystallinity of the material, thus inhibiting the initiation and growth of water trees in the insulation. Patent CN119119613A discloses a water-tree resistant and electrical-tree resistant cable insulation material and its preparation method. A mixed solution of polyethylene, polyvinyl alcohol, and polyacrylic acid is subjected to a photo-initiated reaction under ultraviolet light, inducing the formation of supramolecular dynamic covalent bonds between polyvinyl alcohol and polyacrylic acid, achieving self-healing ability and excellent water-tree and electrical-tree resistant properties. Patent CN116656026A discloses a water-tree resistant cross-linked polyethylene cable material. The raw materials include polyethylene, modified SiO2 nanofiller, vinyltrimethoxysilane, cross-linking agent, and antioxidant, prepared through a three-step method. Patent CN111849052A discloses a corrosion-resistant and water-tree-resistant shielding material and its preparation method, wherein the water-tree-resistant masterbatch is polymethyl methacrylate and the conductive shielding masterbatch is graphite powder. The aforementioned prior art suffers from complex processes or poor water-tree-resistant performance. Summary of the Invention

[0005] In view of this, the present invention provides a water-tree resistant polyethylene insulation material, which improves the water-tree resistant performance by controlling the ratio of crosslinking degree to crystallinity of the insulation material through the combination of different components in the composite crosslinking agent.

[0006] The water-tree resistant polyethylene insulation material of the present invention is composed of the following components in parts by weight: 95-100 parts of PE resin; 0.4-0.6 parts of composite antioxidant; 0.9-1.1 parts of composite crosslinking agent; and 2.5-3.5 parts of modified barrier agent.

[0007] Preferably, the PE resin is LDPE. More preferably, the LDPE has a melt flow rate (MFR) (2.16 kg / 190°C) of 1.8–2.1 g / 10 min, a density of 0.918–920 g / cm³, and an ash content ≤0.01%.

[0008] Preferably, the composite antioxidant is a compound obtained by mixing pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] (1010) and tris(2,4-di-tert-butylphenyl) phosphite (168) in a mass ratio of (2-5):(1-4). More preferably, the mass ratio is (3-4):(2-3).

[0009] Preferably, the composite crosslinking agent is two or more of oxide compounds and isocyanurate compounds; the oxide compound is at least one of dicumyl peroxide (DCP), benzoyl peroxide (BPO), 1,4-di-tert-butylperoxyisopropylbenzene (BIPB), and 2,5-dimethyl-2,5-di-tert-butylperoxyhexane (Bi25); and the isocyanurate compound is at least one of triallyl isocyanurate (TAIC) and triglycidyl isocyanate (TGIC).

[0010] More preferably, the composite crosslinking agent is a compound obtained by mixing dicumyl peroxide (DCP), 2,5-dimethyl-2,5-di-tert-butylperoxide (Bi25), and triallyl isocyanurate (TAIC) in a mass ratio of (2-4):(3-5):(1-4). More preferably, the mass ratio is (2.5-3.5):(3.5-4.5):(2-3).

[0011] Preferably, the modified barrier agent is silica modified with a surface modifier; the silica is fumed silica nanoparticles with a particle size of 5-20 nm; and the surface modifier is a silane compound.

[0012] More preferably, the particle size of the fumed silica nanoparticles is 10-15 nm; the silane compound is at least one of vinyltrimethoxysilane (VTMS), vinyltriethoxysilane (VTES), and phenyltrimethoxysilane.

[0013] More preferably, the preparation method of the modified barrier agent includes the following steps:

[0014] (1) Alcohololysis of surface modifier: Dilute the surface modifier with ethanol to obtain a solution with a surface modifier mass ratio of 10% to 30%, stir at room temperature for 1.0 to 1.5 hours, and then let stand for 1.0 hours to obtain the alcohol-hydrolyzed surface modifier;

[0015] (2) Silica surface treatment: Add silica to a high-speed mixer with a rotation speed of 3000 rpm, add alcoholysis surface modifier, stir and heat to above 90°C and keep warm until the ethanol is completely evaporated.

[0016] This invention also provides a method for preparing a cross-linked polyethylene insulation material with high water-tree resistance, comprising the following steps:

[0017] 1) Add LDPE resin, composite antioxidant, composite crosslinking agent and modified barrier agent to a high-speed mixer and mix evenly to obtain a mixture;

[0018] 2) The mixture is granulated at a temperature of 120℃~140℃, preferably 125℃~135℃.

[0019] The present invention also provides the application of the cross-linked polyethylene insulation material with high water tree resistance, and the cross-linked polyethylene insulation material is used to prepare cable insulation layer. During the preparation process, the temperature of the extruder is 170℃~190℃, preferably 175℃~185℃.

[0020] The cross-linking degree of the cable insulation layer is 81% to 84%, and the cross-linking degree: crystallinity = 1.8 to 2.1.

[0021] Compared with the prior art, the present invention has the following beneficial effects:

[0022] This invention, through the combination of different components in a composite crosslinking agent, allows for a reasonable degree of crosslinking under extrusion cable conditions of 170℃-190℃, thereby influencing crystallinity and controlling the ratio of crosslinking degree to crystallinity of the insulation material to be between 1.8 and 2.1. When the crosslinking degree and crystallinity of the cable insulation layer reach a certain level, the insulation material acquires excellent anti-water-tree properties. Furthermore, the raw materials of this invention contain surface-modified silica, which has good dispersibility and also participates in crosslinking, forming a network structure between particles that prevents moisture penetration and effectively inhibits the growth and spread of water trees. Detailed Implementation

[0023] This invention provides a water-tree resistant polyethylene insulation material, which is composed of the following components in parts by weight: 95-100 parts of PE resin; 0.4-0.6 parts of composite antioxidant; 0.9-1.1 parts of composite crosslinking agent; and 2.5-3.5 parts of modified barrier agent.

[0024] Preferably, the PE resin is LDPE. More preferably, the LDPE has a melt flow rate (MFR) (2.16 kg / 190°C) of 1.8–2.1 g / 10 min, a density of 0.918–920 g / cm³, and an ash content ≤0.01%. In a specific embodiment of the present invention, the LDPE is J182A produced by Qilu Petrochemical Company.

[0025] Preferably, the composite antioxidant is a compound obtained by mixing pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] (1010) and tris(2,4-di-tert-butylphenyl) phosphite (168) in a mass ratio of (2-5):(1-4). More preferably, the mass ratio is (3-4):(2-3).

[0026] Preferably, the composite crosslinking agent is two or more of oxide compounds and isocyanurate compounds; the oxide compound is at least one of dicumyl peroxide (DCP), benzoyl peroxide (BPO), 1,4-di-tert-butylperoxyisopropylbenzene (BIPB), and 2,5-dimethyl-2,5-di-tert-butylperoxyhexane (Bi25); and the isocyanurate compound is at least one of triallyl isocyanurate (TAIC) and triglycidyl isocyanate (TGIC).

[0027] More preferably, the composite crosslinking agent is a compound obtained by mixing dicumyl peroxide (DCP), 2,5-dimethyl-2,5-di-tert-butylperoxide (Bi25), and triallyl isocyanurate (TAIC) in a mass ratio of (2-4):(3-5):(1-4). More preferably, the mass ratio is (2.5-3.5):(3.5-4.5):(2-3).

[0028] Preferably, the modified barrier agent is silica modified with a surface modifier; the silica is fumed silica nanoparticles with a particle size of 5-20 nm; and the surface modifier is a silane compound.

[0029] More preferably, the particle size of the fumed silica nanoparticles is 10-15 nm; the silane compound is at least one selected from vinyltrimethoxysilane (VTMS), vinyltriethoxysilane (VTES), and phenyltrimethoxysilane. In a specific embodiment of the present invention, the silane compound is vinyltriethoxysilane (VTES), specifically silane coupling agent A-151 purchased from Nanjing Shuguang Chemical Group Co., Ltd.; the fumed silica nanoparticles are purchased from Shandong Shouguang Changtai New Materials Co., Ltd.

[0030] More preferably, the preparation method of the modified barrier agent includes the following steps:

[0031] (1) Alcohololysis of surface modifier: Dilute the surface modifier with ethanol to obtain a solution with a surface modifier mass ratio of 10% to 30%, stir at room temperature for 1.0 to 1.5 hours, and then let stand for 1.0 hours to obtain the alcohol-hydrolyzed surface modifier;

[0032] (2) Silica surface treatment: Add silica to a high-speed mixer with a speed of 3000 rpm, add alcoholysis surface modifier, stir and heat to above 90°C and keep warm until the ethanol is completely evaporated.

[0033] Preferably, the surface modifier for alcoholysis in step (2) is added at 3.0% to 5.0% of the weight of silica.

[0034] This invention also provides a method for preparing a cross-linked polyethylene insulation material with high water-tree resistance, comprising the following steps:

[0035] 1) Add LDPE resin, composite antioxidant, composite crosslinking agent and modified barrier agent to a high-speed mixer and mix evenly to obtain a mixture;

[0036] 2) The mixture is granulated at a temperature of 120℃~140℃, preferably 125℃~135℃.

[0037] The present invention also provides the application of the cross-linked polyethylene insulation material with high water tree resistance, and the cross-linked polyethylene insulation material is used to prepare cable insulation layer. During the preparation process, the temperature of the extruder is 170℃~190℃, preferably 175℃~185℃.

[0038] The cross-linking degree of the cable insulation layer is 81% to 84%, and the cross-linking degree: crystallinity = 1.8 to 2.1.

[0039] The present invention will be further described below with reference to embodiments. In the specific embodiments of the present invention, the methods described are all conventional methods in the art unless otherwise specified; the raw materials are all commercially available conventional products unless otherwise specified. The proportions of the raw materials are all mass ratios unless otherwise specified.

[0040] Example 1

[0041] A cross-linked polyethylene insulation material with high water tree resistance is composed of the following components in parts by weight: 100 parts PE resin; 0.5 parts composite antioxidant; 1.0 part composite cross-linking agent; and 3.0 parts modified barrier agent.

[0042] The composite antioxidant is a compound obtained by combining pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] (1010) and tris(2,4-di-tert-butylphenyl) phosphite (168) in a mass ratio of 3.5:2.5.

[0043] The composite crosslinking agent is a compound obtained by mixing dicumyl peroxide (DCP), 2,5-dimethyl-2,5-di-tert-butylperoxide (Bi25), and triallyl isocyanurate (TAIC) in a mass ratio of 3:4:2.5.

[0044] The modified barrier agent is fumed nano-silica modified by a surface modifier (silane coupling agent A-151).

[0045] The particle size of the fumed silica nanoparticles is 15 nm. The surface modification process consists of the following steps:

[0046] (1) Alcohololysis of silane coupling agent: The silane coupling agent is diluted with ethanol to obtain a solution with a mass content of 20% silane coupling agent. The solution is stirred at room temperature for 1.5 hours and then left to stand for 1.0 hours to obtain the alcoholyzed silane coupling agent.

[0047] (2) Silica surface treatment: Add fumed nano silica to a high-speed mixer, add alcoholyzed silane coupling agent, the amount of silane coupling agent (pure) is 4.0% of the weight of silica, stir and heat to above 90°C and keep warm until the ethanol is completely evaporated.

[0048] The preparation method of cross-linked polyethylene insulation material with high water-tree resistance is as follows:

[0049] 1) Add LDPE resin, composite antioxidant, composite crosslinking agent and modified barrier agent to a high-speed mixer with a speed of 3000 rpm and mix evenly to obtain a mixture;

[0050] 2) The mixture is subjected to twin-screw granulation at a granulation temperature of 130°C to obtain the cross-linked polyethylene insulation material.

[0051] The cable insulation layer was prepared using cross-linked polyethylene insulation material with high water-tree resistance, and the extruder temperature was 180℃. The degree of cross-linking of the cable insulation layer was 82%, and the cross-linking degree: crystallinity ratio was 2.0.

[0052] Example 2

[0053] A cross-linked polyethylene insulation material with high water tree resistance is composed of the following components in parts by weight: 100 parts PE resin; 0.4 parts composite antioxidant; 1.1 parts composite cross-linking agent; and 2.5 parts modified barrier agent.

[0054] The composite antioxidant is a compound obtained by mixing 1010 and 168 in a mass ratio of 3.5:2.5.

[0055] The composite crosslinking agent is a compound obtained by mixing DCP, Bis25 and TAIC in a mass ratio of 2.5:4:2.

[0056] The modified barrier agent is fumed silica modified with a surface modifier (silane coupling agent A-151). The fumed silica nanoparticles have a particle size of 15 nm. The surface modification process consists of the following steps:

[0057] (1) Alcohololysis of silane coupling agent: The silane coupling agent is diluted with ethanol to obtain a solution with a mass content of 15% silane coupling agent. The solution is stirred at room temperature for 1.5 hours and then left to stand for 1.0 hours to obtain the alcoholyzed silane coupling agent.

[0058] (2) Silica surface treatment: Add fumed nano silica to a high-speed mixer, add alcoholyzed silane coupling agent, the amount of silane coupling agent (pure) is 5.0% of the weight of silica, stir and heat to above 90°C and keep warm until the ethanol is completely evaporated.

[0059] The preparation method of cross-linked polyethylene insulation material with high water-tree resistance is as follows:

[0060] 1) Add LDPE resin, composite antioxidant, composite crosslinking agent and modified barrier agent to a high-speed mixer with a speed of 3000 rpm and mix evenly to obtain a mixture;

[0061] 2) The mixture is subjected to twin-screw granulation at a granulation temperature of 140°C to obtain the cross-linked polyethylene insulation material.

[0062] The cable insulation layer was prepared using cross-linked polyethylene insulation material with high water-tree resistance, and the extruder temperature was 190℃. The degree of cross-linking of the cable insulation layer was 84%, and the cross-linking degree: crystallinity ratio was 2.1.

[0063] Example 3

[0064] A cross-linked polyethylene insulation material with high water tree resistance is composed of the following components in parts by weight: 100 parts PE resin; 0.6 parts composite antioxidant; 0.9 parts composite cross-linking agent; and 3.0 parts modified barrier agent.

[0065] The composite antioxidant is a compound obtained by mixing 1010 and 168 in a mass ratio of 3:3.

[0066] The composite crosslinking agent is a compound obtained by mixing DCP, Bis25 and TAIC in a mass ratio of 3.5:4.5:2.

[0067] The modified barrier agent is fumed nano-silica modified by a surface modifier (silane coupling agent A-151).

[0068] The particle size of the fumed silica nanoparticles is 10 nm. The surface modification process consists of the following steps:

[0069] (1) Alcohololysis of silane coupling agent: The silane coupling agent is diluted with ethanol to obtain a solution with a mass content of 30% silane coupling agent. The solution is stirred at room temperature for 1.5 hours and then left to stand for 1.0 hours to obtain the alcoholyzed silane coupling agent.

[0070] (2) Silica surface treatment: Add fumed nano silica to a high-speed mixer, add alcoholyzed silane coupling agent, the amount of silane coupling agent (pure) is 3.0% of the weight of silica, stir and heat to above 90°C and keep warm until the ethanol is completely evaporated.

[0071] The preparation method of cross-linked polyethylene insulation material with high water-tree resistance is as follows:

[0072] 1) Add LDPE resin, composite antioxidant, composite crosslinking agent and modified barrier agent to a high-speed mixer with a speed of 3000 rpm and mix evenly to obtain a mixture;

[0073] 2) The mixture is subjected to twin-screw granulation at a granulation temperature of 120°C to obtain the cross-linked polyethylene insulation material.

[0074] The cable insulation layer was prepared using cross-linked polyethylene insulation material with high water-tree resistance, and the extruder temperature was 170℃. The degree of cross-linking of the cable insulation layer was 81%, and the cross-linking degree: crystallinity ratio was 1.8.

[0075] Example 4

[0076] A cross-linked polyethylene insulation material with high water tree resistance is composed of the following components in parts by weight: 100 parts PE resin; 0.5 parts composite antioxidant; 1.1 parts composite cross-linking agent; and 2.5 parts modified barrier agent.

[0077] The composite antioxidant is a compound obtained by mixing 1010 and 168 in a mass ratio of 3:2.

[0078] The composite crosslinking agent is a compound obtained by mixing DCP, Bis25 and TAIC in a mass ratio of 2.5:3.5:2.5.

[0079] The modified barrier agent is fumed nano-silica modified by a surface modifier (silane coupling agent A-151).

[0080] The particle size of the fumed silica nanoparticles is 15 nm. The surface modification process consists of the following steps:

[0081] (1) Alcohololysis of silane coupling agent: The silane coupling agent is diluted with ethanol to obtain a solution with a mass content of 20% silane coupling agent. The solution is stirred at room temperature for 1.5 hours and then left to stand for 1.0 hours to obtain the alcoholyzed silane coupling agent.

[0082] (2) Silica surface treatment: Add fumed nano silica to a high-speed mixer, add alcoholyzed silane coupling agent, the amount of silane coupling agent (pure) is 4.0% of the weight of silica, stir and heat to above 90°C and keep warm until the ethanol is completely evaporated.

[0083] The preparation method of cross-linked polyethylene insulation material with high water-tree resistance is as follows:

[0084] 1) Add LDPE resin, composite antioxidant, composite crosslinking agent and modified barrier agent to a high-speed mixer with a speed of 3000 rpm and mix evenly to obtain a mixture;

[0085] 2) The mixture is subjected to twin-screw granulation at a granulation temperature of 140°C to obtain the cross-linked polyethylene insulation material.

[0086] The cable insulation layer was prepared using cross-linked polyethylene insulation material with high water-tree resistance, and the extruder temperature was 175℃. The degree of cross-linking of the cable insulation layer was 81%, and the cross-linking degree: crystallinity ratio was 1.9.

[0087] Example 5

[0088] A cross-linked polyethylene insulation material with high water tree resistance is composed of the following components in parts by weight: 100 parts PE resin; 0.4 parts composite antioxidant; 0.9 parts composite cross-linking agent; and 3.5 parts modified barrier agent.

[0089] The composite antioxidant is a compound obtained by mixing 1010 and 168 in a mass ratio of 3.5:3.

[0090] The composite crosslinking agent is a compound obtained by mixing DCP, Bis25 and TAIC in a mass ratio of 3.5:3.5:2.

[0091] The modified barrier agent is fumed nano-silica modified by a surface modifier (silane coupling agent A-151).

[0092] The particle size of the fumed silica nanoparticles is 12 nm. The surface modification process consists of the following steps:

[0093] (1) Alcohololysis of silane coupling agent: The silane coupling agent is diluted with ethanol to obtain a solution with a mass content of 20% silane coupling agent. The solution is stirred at room temperature for 1.5 hours and then left to stand for 1.0 hours to obtain the alcoholyzed silane coupling agent.

[0094] (2) Silica surface treatment: Add fumed nano silica to a high-speed mixer, add alcoholyzed silane coupling agent, the amount of silane coupling agent (pure) is 5.0% of the weight of silica, stir and heat to above 90°C and keep warm until the ethanol is completely evaporated.

[0095] The preparation method of cross-linked polyethylene insulation material with high water-tree resistance is as follows:

[0096] 1) Add LDPE resin, composite antioxidant, composite crosslinking agent and modified barrier agent to a high-speed mixer with a speed of 3000 rpm and mix evenly to obtain a mixture;

[0097] 2) The mixture is subjected to twin-screw granulation at a granulation temperature of 130°C to obtain the cross-linked polyethylene insulation material.

[0098] The cable insulation layer was prepared using cross-linked polyethylene insulation material with high water-tree resistance, and the extruder temperature was 185℃. The degree of cross-linking of the cable insulation layer was 82%, and the cross-linking degree: crystallinity ratio was 2.0.

[0099] Comparative Example 1

[0100] The raw material composition and preparation method are the same as in Example 1, except that the crosslinking agent in Comparative Example 1 is dicumyl peroxide (DCP).

[0101] The cross-linking degree of the obtained cable insulation layer is 86%, and the cross-linking degree: crystallinity = 3.0.

[0102] Comparative Example 2

[0103] The raw material composition and preparation method are the same as in Example 1, except that the crosslinking agent in Comparative Example 2 is triallyl isocyanurate (TAIC).

[0104] The cross-linking degree of the obtained cable insulation layer is 72%, and the cross-linking degree: crystallinity = 1.5.

[0105] Comparative Example 3

[0106] The raw material composition and preparation method are the same as in Example 1, except that the crosslinking agent in Comparative Example 3 is an unmodified fumed nano-silica with a particle size of 15 nm.

[0107] The cross-linking degree of the obtained cable insulation layer is 80%, and the cross-linking degree: crystallinity = 1.9.

[0108] Comparative Example 4

[0109] The raw material composition and preparation method are the same as in Example 1. The difference is that the extruder temperature for preparing the cable insulation layer in Comparative Example 4 is 160°C, and the crosslinking degree of the cable insulation layer is 70%, with a crosslinking degree: crystallinity ratio of 1.4.

[0110] Comparative Example 5

[0111] The raw material composition and preparation method are the same as in Example 1, except that the extruder temperature for preparing the cable insulation layer in Comparative Example 5 is 200°C. The degree of crosslinking of the cable insulation layer is 87%, and the ratio of crosslinking degree to crystallinity is 3.5.

[0112] Performance tests were conducted on the cable insulation layers prepared using visual acuity samples 1-5 and comparative examples 1-5.

[0113] Performance testing methods:

[0114] Tensile strength and elongation at break were tested according to GB / T 1040.2—2022 "Determination of tensile properties of plastics - Part 2: Test conditions for molded and extruded plastics", using type II specimens and a tensile speed of 250 mm·min⁻¹.

[0115] Thermal elongation performance was tested according to GB / T 2951.5—1997 "General Test Methods for Cable Insulation and Sheath Materials", using Type II specimens, at a test temperature of 200℃ for 15 minutes.

[0116] The gel content was tested according to Appendix A of JB / T 10437—2004 "Cross-linkable polyethylene insulation materials for wires and cables".

[0117] The length of water tree was tested in accordance with DL / T 1070—2007 "Test Method and Requirements for Identification of Water Tree Resistance of Medium Voltage Cross-linked Cables".

[0118] The performance test results are shown in Tables 1 and 2:

[0119] Table 1

[0120]

[0121] Table 2

[0122]

[0123] Compared to Example 1, Comparative Example 1 used a single crosslinking agent, dicumyl peroxide (DCP), resulting in a high degree of crosslinking in the cable insulation layer, with a higher crosslinking-to-crystallinity ratio. Comparative Example 2 used a single crosslinking agent, triallyl isocyanurate (TAIC), resulting in a low degree of crosslinking in the cable insulation layer, with a lower crosslinking-to-crystallinity ratio. In both cases, the water-tree resistance of the insulation material was poor.

[0124] Comparative Example 3 used unmodified silica as a barrier agent. The unmodified barrier agent had poor dispersion, which affected the crosslinking degree and crystallinity of the insulation material. At the same time, it could not block water vapor, resulting in poor water tree resistance of the insulation material.

[0125] In Comparative Example 4, the lower temperature during cable fabrication resulted in a lower degree of cross-linking and a lower ratio of cross-linking to crystallinity. Conversely, in Comparative Example 5, the higher temperature during cable fabrication resulted in a higher degree of cross-linking and a higher ratio of cross-linking to crystallinity. In both cases, the water-tree resistance of the insulation material was poor.

[0126] It can be seen that if the extrusion temperature is too low, the crystallinity of the insulation material is high, and the incomplete decomposition of the crosslinking agent results in low crosslinking. If the temperature is too high, the crosslinking is too high, which affects the crystallinity. Under both conditions, the water-tree resistance of the insulation material will be poor.

[0127] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A water-tree resistant polyethylene insulation material, characterized in that, It is composed of the following components in parts by weight: 95-100 parts of PE resin; 0.4-0.6 parts of composite antioxidant; 0.9-1.1 parts of composite crosslinking agent; and 2.5-3.5 parts of modified barrier agent.

2. The water-tree resistant polyethylene insulation material according to claim 1, characterized in that, The PE resin is LDPE.

3. The water-tree resistant polyethylene insulation material according to claim 1, characterized in that, The composite antioxidant is a compound obtained by mixing pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] with tris(2,4-di-tert-butylphenyl) phosphite in a mass ratio of (2-5):(1-4).

4. The water-tree resistant polyethylene insulation material according to claim 1, characterized in that, The composite crosslinking agent is two or more of oxide compounds and isocyanurate compounds; the oxide compound is at least one of dicumyl peroxide, benzoyl peroxide, 1,4-di-tert-butylperoxyisopropylbenzene, and 2,5-dimethyl-2,5-di-tert-butylperoxyhexane; the isocyanurate compound is at least one of triallyl isocyanurate and triglycidyl isocyanurate.

5. The water-tree resistant polyethylene insulation material according to claim 4, characterized in that, The composite crosslinking agent is a compound obtained by mixing dicumyl peroxide, 2,5-dimethyl-2,5-di-tert-butylperoxide and triallyl isocyanurate in a mass ratio of (2-4):(3-5):(1-4).

6. The water-tree resistant polyethylene insulation material according to claim 1, characterized in that, The modified barrier agent is silica modified with a surface modifier; the silica is fumed silica nanoparticles with a particle size of 5-20 nm; and the surface modifier is a silane compound.

7. The water-tree resistant polyethylene insulation material according to claim 6, characterized in that, The particle size of the fumed silica nanoparticles is 10-15 nm; the silane compound is at least one of vinyltrimethoxysilane, vinyltriethoxysilane, and phenyltrimethoxysilane.

8. The water-tree resistant polyethylene insulation material according to claim 6, characterized in that, The preparation method of the modified barrier agent includes the following steps: (1) Alcohololysis of surface modifier: Dilute the surface modifier with ethanol to obtain a solution with a surface modifier mass ratio of 10% to 30%, stir at room temperature for 1.0 to 1.5 hours, and then let stand for 1.0 hours to obtain the alcohol-hydrolyzed surface modifier; (2) Silica surface treatment: Add silica to a high-speed mixer with a rotation speed of 3000 rpm, add alcoholysis surface modifier, stir and heat to above 90°C and keep warm until the ethanol is completely evaporated.

9. The method for preparing water-tree resistant polyethylene insulation material according to claim 1, characterized in that, Includes the following steps: 1) Add LDPE resin, composite antioxidant, composite crosslinking agent and modified barrier agent to a high-speed mixer and mix evenly to obtain a mixture; 2) The mixture is granulated at a temperature of 120℃~140℃, preferably 125℃~135℃.

10. The application of the water-tree resistant polyethylene insulation material according to claim 1, characterized in that, The cross-linked polyethylene insulating material is used to prepare the cable insulation layer. During the preparation process, the temperature of the extruder is 170℃~190℃, preferably 175℃~185℃. The cross-linking degree of the cable insulation layer is 81% to 84%, and the cross-linking degree: crystallinity = 1.8 to 2.1.

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