A non-crosslinked polyethylene semiconductive shielding material, and a preparation method and application thereof

Abstract

The application discloses a non-crosslinked polyethylene semiconductive shielding material and a preparation method and application thereof, and relates to the field of cable materials. The non-crosslinked polyethylene semiconductive shielding material comprises a base resin, conductive carbon black and an additive; the base resin comprises linear low-density polyethylene and polyolefin elastomer in a mass ratio of (7-8.5):(1.5-3), and the melt index of the linear low-density polyethylene under the condition of 190 DEG C and 2.16 kg is less than or equal to 1 g / 10 min. By introducing POE in a specific proportion into the LLDPE base, a blending system with high mechanical strength, low melt viscosity and excellent carbon black dispersity is constructed, so that the rheological properties of the semiconductive shielding material are improved on the basis of higher electrical and mechanical properties, the semiconductive shielding material is easier to process, and the comprehensive requirements of the mechanical, electrical and processing properties of the shielding layer of a medium and high voltage cable are met.

Description

Technical Field

[0001] This application relates to the field of cable materials, and in particular to a non-crosslinked polyethylene semiconductive shielding material, its preparation method, and its application. Background Technology

[0002] Cross-linked polyethylene (XLPE) is currently the most widely used insulation material for medium and high voltage power cables, possessing advantages such as excellent insulation performance, good mechanical properties, and stable chemical properties. However, after extrusion, XLPE requires high-temperature vulcanization pipes for the cross-linking reaction of polyethylene, generating significant energy consumption. Furthermore, energy-intensive degassing treatment of cross-linking byproducts increases carbon emissions throughout the entire production cycle. Simultaneously, due to the stability of its chemical cross-linking bonds, the insulation is difficult to recycle after cable retirement, requiring incineration or landfill disposal, thus polluting the environment.

[0003] Non-crosslinked insulation materials, with their simple processing technology and recyclability, have become a new trend in the research of medium and high voltage cable insulation materials. Thermoplastic polypropylene (PP) and polyethylene (PE) based materials, due to their low-carbon and environmentally friendly characteristics, have become current research hotspots for non-crosslinked cable insulation materials. Meanwhile, the development of high-voltage semi-conductive shielding materials is equally crucial. These are transition layers located between the metal conductor and the cable insulation material, consisting of an inner shield and an outer shield. Their main function is to uniformly distribute the interfacial electric field between the metal conductor and the insulation. As a key factor affecting cable lifespan, the most important aspects of high-voltage cable semi-conductive shielding materials are their conductivity, mechanical properties at operating temperature, and compatibility with the insulation layer. Compatibility with the insulation layer requires good thermal stability, mechanical properties, and insulation compatibility under operating conditions. Furthermore, when forming a three-layer structure (inner shield-insulation-outer shield) through co-extrusion (inner shield-insulation-outer shield), the processing performance, i.e., the rheological properties, of the shielding and insulation layers must be matched; otherwise, the interface between the shielding and insulation layers will be uneven, rendering the product unusable.

[0004] Currently, three-layer co-extrusion is a common method for extruding insulated cables, requiring good compatibility between the outer shielding layer, insulation layer, and inner shielding layer. However, the hardness of non-crosslinked polyethylene insulation materials is significantly greater than that of crosslinked polyethylene, further increasing the processing difficulty of semi-conductive shielding materials prepared on this basis and reducing their compatibility with the insulation materials. Furthermore, the types and properties of non-crosslinked polyethylene-based insulation materials are far from meeting the application requirements of various power cables, which limits the application and promotion of non-crosslinked polyethylene-based insulation materials. Therefore, conducting research on non-crosslinked polyethylene semi-conductive shielding materials and developing shielding materials with good processing performance and electromechanical properties is of significant practical importance. Summary of the Invention

[0005] This application provides a non-crosslinked polyethylene semiconductive shielding material, its preparation method, and its application. By introducing a specific amount of POE elastomer into a linear low-density polyethylene matrix, a blend system with high mechanical strength, low melt viscosity, and excellent carbon black dispersibility is constructed, which improves the rheological processing performance while ensuring the electrical and mechanical properties of the material.

[0006] To address the aforementioned technical problems, one objective of this application is to provide a non-crosslinked polyethylene semi-conductive shielding material, comprising the following components in parts by weight per 100 parts: Matrix resin: 62-78 parts; Conductive carbon black: 20-35 parts; Additives: 2-6 parts; The matrix resin comprises linear low-density polyethylene and polyolefin elastomer in a mass ratio of (7-8.5):(1.5-3), wherein the linear low-density polyethylene has a melt index ≤1 g / 10 min at 190 ℃ and 2.16 kg.

[0007] In some embodiments, the conductive carbon black has an oil absorption value of 150-300 cc / 100 g.

[0008] In some embodiments, the conductive carbon black has a particle size of 10-50 nm.

[0009] In some embodiments, the ash content of the conductive carbon black is ≤0.01%.

[0010] In some embodiments, the conductive carbon black has an oil absorption value of 150-200 cc / 100 g.

[0011] In some embodiments, the conductive carbon black has a particle size of 12-30 nm.

[0012] In some embodiments, the linear low-density polyethylene has a melt index of 0.1-0.6 g / 10 min at 190 °C and 2.16 kg.

[0013] In some embodiments, the linear low-density polyethylene has a density of 0.91 g / cm³. 3 -0.94 g / cm 3 .

[0014] In some embodiments, the polyolefin elastomer has a melt index of 2-4 g / 10 min at 190 °C and 2.16 kg.

[0015] In some embodiments, the density of the polyolefin elastomer is 0.8 g / cm³. 3 -1 g / cm3 .

[0016] In some embodiments, the conductive carbon black is 25-30 parts by weight.

[0017] In some embodiments, the additives include at least one of antioxidants, dispersants, antistatic agents, and heat stabilizers.

[0018] In some embodiments, the adjuvant includes 0.5-3 parts by weight of an antioxidant and 1-3 parts by weight of a dispersant.

[0019] To address the aforementioned technical problems, a second objective of this application is to provide a method for preparing a non-crosslinked polyethylene semiconductive shielding material, comprising the following steps: (1) The additives include antioxidants and dispersants. The matrix resin and antioxidants are mixed evenly and then melt-blended once. The mixture is then extruded by a twin-screw extruder, cold-cut, granulated, and dried to obtain a premix. (2) The conductive carbon black and the dispersant are mixed evenly to obtain a carbon black mixture. The premix is ​​heated and stirred to melt, and then the carbon black mixture is added for secondary melting and blending to obtain a shielding material mixture. (3) The shielding material mixture is extruded, cooled and granulated to obtain a non-crosslinked polyethylene semiconductive shielding material.

[0020] To address the aforementioned technical problems, a third objective of this application is to provide an application of a non-crosslinked polyethylene semiconductive shielding material in the preparation of cable materials.

[0021] Compared with the prior art, this application has the following beneficial effects: 1. The non-crosslinked polyethylene semiconductive shielding material provided in this application introduces a specific proportion of POE into the LLDPE matrix, which reduces the melt viscosity and matrix rigidity of the blend system, so that it can still maintain a certain degree of flexibility and ductility after high carbon black filling. It constructs a blend system with high mechanical strength, low melt viscosity and excellent carbon black dispersibility, and significantly improves the rheological properties and processing properties of the shielding material while maintaining high electromechanical properties.

[0022] 2. This application is based on a thermoplastic polymer system and does not contain chemical cross-linking structures, allowing for efficient recycling and reuse through conventional thermoplastic processing methods after the cable's service life. Furthermore, this material exhibits good compatibility with commercially available polyethylene waste plastics and can be used as a functional component in the recycling system of polyolefin mixed waste plastics, avoiding the environmental burden of traditional cross-linked shielding materials that can only be landfilled or incinerated due to their non-melting nature. Therefore, this application not only reduces energy consumption during the production stage but also achieves resource closure at the end of its entire life cycle, aligning with the development direction of green cables and the circular economy. Attached Figure Description

[0023] Figure 1 This is a torque-speed relationship diagram of the non-crosslinked polyethylene semiconductive shielding material in Example 1 and Comparative Examples 1-3 of this application; Figure 2 The tensile curve of the non-crosslinked polyethylene semiconductive shielding material in Example 1 of this application; Figure 3 The tensile curve of the non-crosslinked polyethylene semiconductive shielding material in Comparative Example 2 of this application; Figure 4 The above are DSC curves of the non-crosslinked polyethylene semiconductive shielding materials in Example 1 and Comparative Examples 1 and 4 of this application. Figure 5 The XRD patterns of the non-crosslinked polyethylene semiconductive shielding materials in Example 1 and Comparative Examples 4-5 of this application are shown. Figure 6 This is a SEM image of the fracture surface of the non-crosslinked polyethylene semiconductive shielding material in Example 1 of this application after low-temperature brittle fracture. Detailed Implementation

[0024] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of this application.

[0025] It should be understood that the terminology used in this application is merely for describing particular implementations and is not intended to limit the application. Furthermore, for numerical ranges in this application, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Any stated value or intermediate value within a stated range, as well as each smaller range between any other stated value or intermediate value within said range, is also included in this application. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0026] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art described herein. While only preferred methods and materials are described herein, any methods and materials similar or equivalent to those described herein may be used in the implementation or testing of this application. All references to this specification are incorporated by way of citation to disclose and describe methods and / or materials associated with those references. In the event of any conflict with any incorporated reference, the content of this specification shall prevail.

[0027] As used in this article: In these embodiments, unless otherwise specified, the portions and percentages are all by weight.

[0028] "And / or" is used to indicate that one or both of the described situations may occur, for example, A and / or B includes (A and B) and (A or B).

[0029] This application provides a non-crosslinked polyethylene semi-conductive shielding material, comprising the following components in parts by weight per 100 parts: Matrix resin: 62-78 parts; Conductive carbon black: 20-35 parts; Additives: 2-6 parts; The matrix resin comprises linear low-density polyethylene and polyolefin elastomer in a mass ratio of (7-8.5):(1.5-3), wherein the linear low-density polyethylene has a melt index ≤1 g / 10 min at 190 ℃ and 2.16 kg.

[0030] LLDPE, as the main chain polymer in this application, possesses high crystallinity, excellent heat resistance, good mechanical strength, and electrical insulation properties, making it an ideal matrix for constructing a highly stable non-crosslinked polyethylene cable shielding layer. Its low melt index ensures the material's mechanical strength and long-term thermal stability. However, pure LLDPE, due to its regular molecular chains and dense crystalline regions, exhibits high melt viscosity and poor flowability, easily leading to stress concentration during extrusion molding. Furthermore, when combined with highly filled conductive carbon black, the melt viscosity becomes excessively high, resulting in poor processability. During three-layer co-extrusion, interfacial stress easily arises with the insulation layer, affecting the cable's structural integrity. By introducing a specific proportion of POE into the LLDPE matrix, the introduction of POE reduces the melt viscosity and matrix rigidity of the blend system, allowing it to maintain a certain degree of flexibility and ductility even after carbon black filling. This creates a blend system that combines high mechanical strength, low melt viscosity, and excellent carbon black dispersion. Simultaneously, conductive carbon black preferentially distributes in the amorphous region, and the presence of POE further broadens the distribution range of the amorphous region, helping carbon black particles to disperse more uniformly and form three-dimensional conductive pathways, thereby reducing volume resistivity. Without the need for crosslinking, this not only meets the comprehensive requirements of medium and high voltage cables for the mechanical and electrical properties of the shielding layer but also improves rheological and processing properties, providing technical support for the application of non-crosslinked polyethylene cables in medium and high voltage fields.

[0031] In some embodiments, the matrix resin comprises linear low-density polyethylene and polyolefin elastomers in a mass ratio of any one of 7:3, 7.5:2.5, 8:2, 8.5:3, or a range between any two.

[0032] In some embodiments, the conductive carbon black has an oil absorption value of 150-300 cc / 100 g.

[0033] In some embodiments, the oil absorption value of the conductive carbon black is a range of any one or any two of the following: 150 cc / 100 g, 160 cc / 100 g, 170 cc / 100 g, 180 cc / 100 g, 190 cc / 100 g, 200 cc / 100 g, 210 cc / 100 g, 220 cc / 100 g, 230 cc / 100 g, 240 cc / 100 g, 250 cc / 100 g, 260 cc / 100 g, 270 cc / 100 g, 280 cc / 100 g, 290 cc / 100 g, and 300 cc / 100 g.

[0034] In some embodiments, the conductive carbon black has a particle size of 10-50 nm.

[0035] In some embodiments, the particle size of the conductive carbon black is any one or a range between any two of 10 nm, 15 nm, 20 nm, 25 nm, 30 nm, 35 nm, 40 nm, and 50 nm.

[0036] In some embodiments, the conductive carbon black has an ash content of ≤0.01%, and the low ash content reduces the interference of impurities on electrical properties.

[0037] In some embodiments, the conductive carbon black has an oil absorption value of 150-200 cc / 100 g.

[0038] In some embodiments, the conductive carbon black has a particle size of 12-30 nm.

[0039] The oil absorption value and particle size of the conductive carbon black in this application are preferably within the above-mentioned range. The high specific surface area of ​​the conductive carbon black is conducive to the formation of a continuous conductive network, and the moderate oil absorption value can ensure that it is easy to disperse and not agglomerate during the blending process, thereby improving the mechanical and rheological properties of the material, promoting the uniform dispersion of conductive carbon black in the material system, forming a uniform three-dimensional conductive network, and reducing the volume resistivity.

[0040] In some embodiments, the linear low-density polyethylene has a melt index of 0.1-0.6 g / 10 min at 190 °C and 2.16 kg.

[0041] In some embodiments, the melt index of the linear low-density polyethylene at 190 °C and 2.16 kg is a range of any one or any two of 0.1 g / 10 min, 0.2 g / 10 min, 0.3 g / 10 min, 0.4 g / 10 min, 0.5 g / 10 min, and 0.6 g / 10 min.

[0042] The linear low-density polyethylene of this application preferably adopts the above-mentioned lower melt index range. The LLDPE with a lower melt index often has longer molecular chains or more long branches in the molecules, which improves the physical entanglement effect between molecules. After adding conductive carbon black for dispersion, the slippage ability between molecular chains under tensile conditions is improved, which improves the ductility of the material, improves mechanical properties and long-term thermal stability.

[0043] In some embodiments, the linear low-density polyethylene has a density of 0.91 g / cm³. 3 -0.94 g / cm 3 .

[0044] In some embodiments, the polyolefin elastomer has a melt index of 2-4 g / 10 min at 190 °C and 2.16 kg.

[0045] In some embodiments, the melt index of the polyolefin elastomer at 190 °C and 2.16 kg is any one of 2 g / 10 min, 2.5 g / 10 min, 3 g / 10 min, 3.5 g / 10 min, 4 g / 10 min, or a range between any two.

[0046] In some embodiments, the density of the polyolefin elastomer is 0.8 g / cm³. 3 -1 g / cm 3 .

[0047] In some embodiments, the conductive carbon black is 25-30 parts by weight.

[0048] In some embodiments, the conductive carbon black is in the range of any one or any two of 25 parts, 26 parts, 27 parts, 28 parts, 29 parts, and 30 parts by weight.

[0049] The semiconductive shielding material of this application reduces the rigidity of the matrix due to the introduction of POE, so that the highly conductive carbon black can still maintain a certain degree of flexibility and ductility after filling. By controlling the conductive carbon black within the above-mentioned preferred range, sufficient conductive carbon black can be used to improve the electrical properties of the material and reduce the volume resistivity. At the same time, excessive filling of conductive carbon black is avoided, which leads to the common embrittlement phenomenon of the system and ensures the mechanical properties of the material.

[0050] In some embodiments, the additives include at least one of antioxidants, dispersants, antistatic agents, and heat stabilizers.

[0051] In some embodiments, the adjuvant includes 0.5-3 parts by weight of an antioxidant and 1-3 parts by weight of a dispersant.

[0052] In some embodiments, the antioxidant includes at least one of antioxidant 300, antioxidant 1010, and antioxidant 1035.

[0053] In some embodiments, the dispersant includes at least one of ethylene bis-stearamide, white oil, and zinc stearate.

[0054] In this application, the antioxidant effectively inhibits the oxidative degradation of polyethylene chains under high-temperature processing conditions, extending the service life of the material, and is particularly suitable for power cable systems operating in high-temperature environments for extended periods. The dispersant significantly improves the dispersibility of conductive carbon black in the matrix resin, prevents agglomeration, reduces the melt friction coefficient, and enhances the stability and surface finish of the extrusion process. The antioxidant and dispersant not only improve the processing stability of the material but also indirectly enhance the consistency of electrical properties and long-term service reliability.

[0055] This application also provides a method for preparing a non-crosslinked polyethylene semiconductive shielding material, comprising the following steps: (1) The additives include antioxidants and dispersants. The matrix resin and antioxidants are mixed evenly and then melt-blended once. The mixture is then extruded by a twin-screw extruder, cold-cut, granulated, and dried to obtain a premix. (2) The conductive carbon black and the dispersant are mixed evenly to obtain a carbon black mixture. The premix is ​​heated and stirred to melt, and then the carbon black mixture is added for secondary melting and blending to obtain a shielding material mixture. (3) The shielding material mixture is extruded, cooled and granulated to obtain a non-crosslinked polyethylene semiconductive shielding material.

[0056] In some embodiments, in step (1), all raw materials are pre-dried at 60-80 °C for 20-24 h.

[0057] In the subsequent melt blending process of this application, if the moisture in the raw materials is not sufficiently removed, bubbles or micropores will form under shear force, leading to an increase in internal defects and affecting the consistency of electrical and mechanical properties. Furthermore, trace amounts of moisture adsorbed on the surface of conductive carbon black can easily cause carbon black aggregation, thus affecting the uniformity of material dispersion. Therefore, drying the raw materials to remove moisture and prevent the formation of bubbles or degradation during high-temperature melting can ensure the stability of the final material quality.

[0058] In some embodiments, the primary melt blending in step (1) is preferably carried out using a twin-screw extruder, a reciprocating screw extruder, or a mixer.

[0059] In some embodiments, in step (1), the temperature of the first melt blending is 140-160 °C. From the feed port to the die head, the cylinder temperature is set in 6-8 zones and has a distribution pattern of gradient heating followed by a drop, so as to take into account melting plasticization, mixing homogenization and melt stability.

[0060] The preferred temperature distribution example is divided into eight zones, from the feed port to the die head: 140 ℃, 150 ℃, 160 ℃, 160 ℃, 160 ℃, 160 ℃, 160 ℃, 150 ℃. This lower initial temperature is conducive to the forward movement of the melt, helps the melt gradually absorb heat, and avoids local overheating or material agglomeration due to sudden temperature rise; maintaining a higher constant temperature in the middle zone is conducive to the full movement and mutual diffusion of polymer chain segments, achieving uniform dispersion; and moderate cooling near the die head reduces melt viscosity fluctuations, ensuring smooth extrusion and molding of the material.

[0061] In some embodiments, in step (1), the rotation speed of the primary melt blending is 30-50 r / min.

[0062] This application preferably uses the above-mentioned rotational speed range to avoid insufficient shear force due to excessively low speed. Too low a speed makes it difficult to effectively disperse POE particles and promote their uniform dispersion in the LLDPE matrix, easily leading to phase separation or local enrichment, affecting the microscopic uniformity of the blend. Simultaneously, it avoids excessively long material residence time, which could cause localized overheating or thermo-oxidative aging. Excessively high speeds also avoid introducing excessive shear force, leading to localized temperature increases, preventing polymer scorching, and introducing impurities.

[0063] In some embodiments, in step (2), the secondary melt blending is preferably carried out in a twin-screw extruder, a Busch mill, a mixer, or a torque rheometer.

[0064] In some embodiments, in step (2), the secondary melt blending temperature is 170-190 °C, the rotation speed is 40-60 r / min, and the blending time is 10-20 min.

[0065] This application premixes conductive carbon black and a dispersant evenly, ensuring the dispersant uniformly coats the surface of the conductive carbon black, reducing its surface energy and preventing agglomeration during subsequent high-temperature blending. The premix is ​​melted and plasticized before adding the carbon black mixture to prevent premature oxidation or agglomeration at low temperatures. Simultaneously, controlling the mixing temperature at 170-190℃ prevents thermo-oxidative degradation of the polyethylene chains at high temperatures. This temperature, slightly higher than the initial melt-blending temperature, helps overcome the viscosity increase caused by high carbon black filler, improving fluidity. In other words, it ensures the premix is ​​in a good flowable state to accommodate the highly filled carbon black. Combined with a shear speed of 40-60 r / min, sufficient dispersing shear force is provided while avoiding excessive mechanical degradation.

[0066] This application also provides the application of a non-crosslinked polyethylene semiconductive shielding material in the preparation of cable materials.

[0067] To further illustrate this application, the following detailed description is provided in conjunction with embodiments, but these should not be construed as limiting the scope of protection of this application. Table 1 below shows the sources and types of raw materials used in the embodiments and comparative examples of this application. Unless otherwise specified, all raw materials used are commercially available, and the same raw materials were used in parallel experiments.

[0068] Table 1 - Sources and types of raw materials used in the embodiments and comparative examples of this application Example 1 A non-crosslinked polyethylene semiconductive shielding material, based on a total weight of 100 g, comprises 72.5 g of matrix resin, 25 g of conductive carbon black, and 2.5 g of additives. The matrix resin comprises linear low-density polyethylene (LLDPE) and polyolefin elastomer (POE) in a mass ratio of 8:2; the LLDPE is Borealis FB2230 with a density of 0.923 g / cm³. 3 The melt flow index is 0.25 g / 10 min (190℃, 2.16 kg); the POE is Dow Chemical 8450, with a density of 0.9 g / cm³. 3 The melt flow index is 3.0 g / 10 min (190 ℃, 2.16 kg); the particle size of the conductive carbon black is 30 nm, the oil absorption value is 174 cc / 100 g, and the ash content is ≤0.1%; the additives include 1 g of antioxidant and 1.5 g of dispersant, the antioxidant is antioxidant 300, and the dispersant is ethylene bis-stearamide.

[0069] The preparation method of the above-mentioned non-crosslinked polyethylene semiconductive shielding material includes the following steps: (1) The raw materials were dried at 70 ℃ for 24 h to remove moisture. Then, LLDPE, POE and antioxidant were mixed evenly and placed in a twin-screw extruder for one melt blending. The speed was set to 30 rpm. The temperatures of each zone from the feed port to the die head were set to 140 ℃, 150 ℃, 160 ℃, 160 ℃, 160 ℃, 160 ℃, 160 ℃, 150 ℃. After extrusion and water cooling by twin screw extruder, the mixture was connected to a pelletizer for granulation. Then, it was dried for 24 h to obtain the premix. (2) Mix the conductive carbon black and the dispersant evenly to obtain a carbon black mixture. Place the premix in a torque rheometer that has been preheated to 180 °C, start the rotor, control the speed to 50 r / min, process for 2 min to melt and plasticize the premix, add the carbon black mixture for secondary melting and blending for 10 min to make the torque tend to be constant, and continue to knead for 5 min to obtain a molten and uniformly mixed shielding material mixture. (3) The shielding material mixture is added to the extruder and extruded. The extruder is heated to 180 ℃ and the die head temperature is 160 ℃. After cooling, it is connected to the pelletizer for granulation to obtain 3-4 mm non-crosslinked polyethylene semi-conductive shielding material.

[0070] Example 2 A non-crosslinked polyethylene semi-conductive shielding material, based on a total weight of 100 g, comprises 63 g of matrix resin, 35 g of conductive carbon black, and 2 g of additives. The matrix resin comprises linear low-density polyethylene (LLDPE) and polyolefin elastomer (POE) in a mass ratio of 8:2; the LLDPE is Borealis FB2230 with a density of 0.923 g / cm³. 3 The melt flow index is 0.25 g / 10 min (190 °C, 2.16 kg); the POE is Dow Chemical 8450, with a density of 0.9 g / cm³. 3 The melt flow index is 3.0 g / 10 min (190 ℃, 2.16 kg); the particle size of the conductive carbon black is 30 nm, the oil absorption value is 174 cc / 100 g, and the ash content is ≤0.1%; the additives include 1 g of antioxidant and 1 g of dispersant, the antioxidant is antioxidant 300, and the dispersant is ethylene bis-stearamide.

[0071] The preparation method of the above-mentioned non-crosslinked polyethylene semiconductive shielding material includes the following steps: (1) The raw materials were dried at 60 °C for 24 h to remove moisture. Then, LLDPE, POE and antioxidant were mixed evenly and placed in a twin-screw extruder for one melt blending. The speed was set to 40 rpm. The temperatures of each zone from the feed port to the die head were set to 140 °C, 150 °C, 160 °C, 160 °C, 160 °C, 160 °C, 160 °C, 160 °C, 150 °C. After extrusion and water cooling by twin screw extruder, the mixture was connected to a pelletizer for granulation. Then, it was dried for 24 h to obtain the premix. (2) Mix the conductive carbon black and the dispersant evenly to obtain a carbon black mixture. Place the premix in a torque rheometer that has been preheated to 170 °C, start the rotor, control the speed to 40 r / min, process for 2 min to melt and plasticize the premix, add the carbon black mixture for secondary melting and blending for 10 min to make the torque tend to be constant, and continue to knead for 5 min to obtain a molten and uniformly mixed shielding material mixture. (3) The shielding material mixture is added to the extruder and extruded. The extruder is heated to 180 ℃ and the die head temperature is 160 ℃. After cooling, it is connected to the pelletizer for granulation to obtain 3-4 mm non-crosslinked polyethylene semi-conductive shielding material.

[0072] Example 3 A non-crosslinked polyethylene semi-conductive shielding material, based on a total weight of 100 g, comprises 75 g of matrix resin, 20 g of conductive carbon black, and 5 g of additives. The matrix resin comprises linear low-density polyethylene (LLDPE) and polyolefin elastomer (POE) in a mass ratio of 8:2; the LLDPE is Borealis FB2230 with a density of 0.923 g / cm³. 3 The melt flow index is 0.25 g / 10 min (190 °C, 2.16 kg); the POE is Dow Chemical 8450, with a density of 0.9 g / cm³. 3 The melt flow index is 3.0 g / 10 min (190 ℃, 2.16 kg); the particle size of the conductive carbon black is 30 nm, the oil absorption value is 174 cc / 100 g, and the ash content is ≤0.1%; the additives include 2 g of antioxidant and 3 g of dispersant, the antioxidant is antioxidant 300, and the dispersant is ethylene bis-stearamide.

[0073] The preparation method of the above-mentioned non-crosslinked polyethylene semiconductive shielding material includes the following steps: (1) The raw materials were dried at 80 °C for 24 h to remove moisture. Then, LLDPE, POE and antioxidant were mixed evenly and placed in a twin-screw extruder for one melt blending. The speed was set to 30 rpm. The temperatures of each zone from the feed port to the die head were set to 140 °C, 150 °C, 160 °C, 160 °C, 160 °C, 160 °C, 160 °C, 160 °C, 150 °C. After extrusion and water cooling by twin screw extruder, the mixture was connected to a pelletizer for granulation. Then, it was dried for 24 h to obtain the premix. (2) Mix the conductive carbon black and the dispersant evenly to obtain a carbon black mixture. Place the premix in a torque rheometer that has been preheated to 190 °C, start the rotor, control the speed to 60 r / min, process for 2 min to melt and plasticize the premix, add the carbon black mixture for secondary melting and blending for 10 min to make the torque tend to be constant, and continue to knead for 5 min to obtain a molten and uniformly mixed shielding material mixture. (3) The shielding material mixture is added to the extruder and extruded. The extruder is heated to 160 ℃ and the die head temperature is 150 ℃. After cooling, it is connected to the pelletizer for granulation to obtain 3-4 mm non-crosslinked polyethylene semi-conductive shielding material.

[0074] Example 4 A non-crosslinked polyethylene semiconductive shielding material, differing from Example 1, comprises, per 100 g total weight, 72.5 g of matrix resin, 25 g of conductive carbon black, and 2.5 g of additives. The matrix resin comprises linear low-density polyethylene (LLDPE) and polyolefin elastomer (POE) in a mass ratio of 8.5:1.5; the LLDPE is Borealis FB2230 with a density of 0.923 g / cm³. 3 The melt flow index is 0.25 g / 10 min (190 °C, 2.16 kg); the POE is Dow Chemical 8450, with a density of 0.9 g / cm³. 3 The melt flow index is 3.0 g / 10 min (190 ℃, 2.16 kg); the conductive carbon black has a particle size of 30 nm, an oil absorption value of 174 cc / 100g, and an ash content of ≤0.1%; the additives include 1 g of antioxidant and 1.5 g of dispersant, the antioxidant being antioxidant 300 and the dispersant being ethylene bis-stearamide.

[0075] Example 5 A non-crosslinked polyethylene semiconductive shielding material, differing from Example 1, comprises, per 100 g total weight, 72.5 g of matrix resin, 25 g of conductive carbon black, and 2.5 g of additives. The matrix resin comprises linear low-density polyethylene (LLDPE) and polyolefin elastomer (POE) in a mass ratio of 7:3; the LLDPE is Borealis FB2230 with a density of 0.923 g / cm³. 3 The melt flow index is 0.25 g / 10 min (190 °C, 2.16 kg); the POE is Dow Chemical 8450, with a density of 0.9 g / cm³. 3The melt flow index is 3.0 g / 10 min (190 ℃, 2.16 kg); the particle size of the conductive carbon black is 30 nm, the oil absorption value is 174 cc / 100 g, and the ash content is ≤0.1%; the additives include 1 g of antioxidant and 1.5 g of dispersant, the antioxidant is antioxidant 300, and the dispersant is ethylene bis-stearamide.

[0076] Example 6 A non-crosslinked polyethylene semiconductive shielding material, differing from Example 1, comprises, per 100 g total weight, 77.5 g of matrix resin, 20 g of conductive carbon black, and 2.5 g of additives. The matrix resin comprises linear low-density polyethylene (LLDPE) and polyolefin elastomer (POE) in a mass ratio of 8:2; the LLDPE is Borealis FB2230 with a density of 0.923 g / cm³. 3 The melt flow index is 0.25 g / 10 min (190 °C, 2.16 kg); the POE is Dow Chemical 8450, with a density of 0.9 g / cm³. 3 The melt flow index is 3.0 g / 10 min (190 ℃, 2.16 kg); the particle size of the conductive carbon black is 30 nm, the oil absorption value is 174 cc / 100 g, and the ash content is ≤0.1%; the additives include 1 g of antioxidant and 1.5 g of dispersant, the antioxidant is antioxidant 300, and the dispersant is ethylene bis-stearamide.

[0077] Example 7 A non-crosslinked polyethylene semiconductive shielding material, differing from Example 1, comprises, per 100 g total weight, 67.5 g of matrix resin, 30 g of conductive carbon black, and 2.5 g of additives. The matrix resin comprises linear low-density polyethylene (LLDPE) and polyolefin elastomer (POE) in a mass ratio of 8:2; the LLDPE is Borealis FB2230 with a density of 0.923 g / cm³. 3 The melt flow index is 0.25 g / 10 min (190 °C, 2.16 kg); the POE is Dow Chemical 8450, with a density of 0.9 g / cm³. 3 The melt flow index is 3.0 g / 10 min (190 ℃, 2.16 kg); the particle size of the conductive carbon black is 30 nm, the oil absorption value is 174 cc / 100 g, and the ash content is ≤0.1%; the additives include 1 g of antioxidant and 1.5 g of dispersant, the antioxidant is antioxidant 300, and the dispersant is ethylene bis-stearamide.

[0078] Example 8 A non-crosslinked polyethylene semiconductive shielding material, differing from Example 1, comprises, per 100 g total weight, 62.5 g of matrix resin, 35 g of conductive carbon black, and 2.5 g of additives. The matrix resin comprises linear low-density polyethylene (LLDPE) and polyolefin elastomer (POE) in a mass ratio of 8:2; the LLDPE is Borealis FB2230 with a density of 0.923 g / cm³. 3 The melt flow index is 0.25 g / 10 min (190 °C, 2.16 kg); the POE is Dow Chemical 8450, with a density of 0.9 g / cm³. 3 The melt flow index is 3.0 g / 10 min (190 ℃, 2.16 kg); the particle size of the conductive carbon black is 30 nm, the oil absorption value is 174 cc / 100 g, and the ash content is ≤0.1%; the additives include 1 g of antioxidant and 1.5 g of dispersant, the antioxidant is antioxidant 300, and the dispersant is ethylene bis-stearamide.

[0079] Example 9 A non-crosslinked polyethylene semiconductive shielding material, differing from Example 1, comprises, per 100 g total weight, 72.5 g of matrix resin, 25 g of conductive carbon black, and 2.5 g of additives. The matrix resin comprises linear low-density polyethylene (LLDPE) and polyolefin elastomer (POE) in a mass ratio of 8:2; the LLDPE is Borealis FB2230 with a density of 0.923 g / cm³. 3 The melt flow index is 0.25 g / 10 min (190 °C, 2.16 kg); the POE is Dow Chemical 8450, with a density of 0.9 g / cm³. 3 The melt flow index is 3.0 g / 10 min (190 ℃, 2.16 kg); the conductive carbon black has a particle size of 30 nm, an oil absorption value of 290 cc / 100 g, and an ash content of ≤0.1%; the additives include 1 g of antioxidant and 1.5 g of dispersant, the antioxidant being antioxidant 300 and the dispersant being ethylene bis-stearamide.

[0080] Example 10 A non-crosslinked polyethylene semiconductive shielding material, differing from Example 1, comprises, per 100 g total weight, 72.5 g of matrix resin, 25 g of conductive carbon black, and 2.5 g of additives. The matrix resin comprises linear low-density polyethylene (LLDPE) and polyolefin elastomer (POE) in a mass ratio of 8:2; the LLDPE is Borealis FB2230 with a density of 0.923 g / cm³. 3 The melt flow index is 0.25 g / 10 min (190 °C, 2.16 kg); the POE is Dow Chemical 8450, with a density of 0.9 g / cm³.3 The melt flow index is 3.0 g / 10 min (190 ℃, 2.16 kg); the particle size of the conductive carbon black is 12 nm, the oil absorption value is 330 cc / 100 g, and the ash content is ≤0.1%; the additives include 1 g of antioxidant and 1.5 g of dispersant, the antioxidant is antioxidant 300, and the dispersant is ethylene bis-stearamide.

[0081] Example 11 A non-crosslinked polyethylene semiconductive shielding material differs from Example 1 in that, in step (2), conductive carbon black and dispersant are mixed evenly to obtain a carbon black mixture. The premix is ​​placed in a torque rheometer preheated to 160 °C, the rotor is started, the rotation speed is controlled at 50 r / min, and the premix is ​​processed for 2 min to melt and plasticize. The carbon black mixture is added and kneaded for another 10 min to make the torque tend to be constant. Then, the mixture is kneaded for another 5 min to obtain a molten and uniformly mixed shielding material mixture.

[0082] Comparative Example 1 A non-crosslinked polyethylene semiconductive shielding material, differing from Example 1, comprises, per 100 g total weight, 72.5 g of matrix resin, 25 g of conductive carbon black, and 2.5 g of additives. The matrix resin is linear low-density polyethylene (LLDPE); the LLDPE is Borealis FB2230 with a density of 0.923 g / cm³. 3 The melt flow index is 0.25 g / 10 min (190 ℃, 2.16 kg); the particle size of the conductive carbon black is 30 nm, the oil absorption value is 174 cc / 100 g, and the ash content is ≤0.1%; the additives include 1 g of antioxidant and 1.5 g of dispersant, the antioxidant is antioxidant 300, and the dispersant is ethylene bis-stearamide.

[0083] Comparative Example 2 A non-crosslinked polyethylene semiconductive shielding material, differing from Example 1, comprises, per 100 g total weight, 72.5 g of matrix resin, 25 g of conductive carbon black, and 2.5 g of additives. The matrix resin comprises high-density polyethylene (HDPE) and polyolefin elastomer (POE) in a mass ratio of 8:2; the HDPE density is 0.945 g / cm³. 3 Melt index is 0.75 g / 10 min (190℃, 2.16 kg); POE is Dow Chemical 8450, density is 0.9 g / cm³. 3The melt flow index is 3.0 g / 10 min (190 ℃, 2.16 kg); the particle size of the conductive carbon black is 30 nm, the oil absorption value is 174 cc / 100 g, and the ash content is ≤0.1%; the additives include 1 g of antioxidant and 1.5 g of dispersant, the antioxidant is antioxidant 300, and the dispersant is ethylene bis-stearamide.

[0084] Comparative Example 3 A non-crosslinked polyethylene semiconductive shielding material, differing from Example 1, comprises, per 100 g total weight, 72.5 g of matrix resin, 25 g of conductive carbon black, and 2.5 g of additives. The matrix resin comprises linear low-density polyethylene (LLDPE) and polyolefin elastomer (POE) in a mass ratio of 8:2; the LLDPE is Exxon LL6301 with a density of 0.936 g / cm³ and a melt index of 5 g / 10 min (190 °C, 2.16 kg); the POE is Dow Chemical 8450 with a density of 0.9 g / cm³. 3 The melt flow index is 3.0 g / 10 min (190 ℃, 2.16 kg); the particle size of the conductive carbon black is 30 nm, the oil absorption value is 174 cc / 100 g, and the ash content is ≤0.1%; the additives include 1 g of antioxidant and 1.5 g of dispersant, the antioxidant is antioxidant 300, and the dispersant is ethylene bis-stearamide.

[0085] Comparative Example 4 A non-crosslinked polyethylene semiconductive shielding material, differing from Example 1, comprises, per 100 g total weight, 72.5 g of matrix resin, 25 g of conductive carbon black, and 2.5 g of additives. The matrix resin comprises linear low-density polyethylene (LLDPE) and polyolefin elastomer (POE) in a mass ratio of 6:4; the LLDPE is Borealis FB2230 with a density of 0.923 g / cm³. 3 The melt flow index is 0.25 g / 10 min (190 °C, 2.16 kg); the POE is Dow Chemical 8450, with a density of 0.9 g / cm³. 3 The melt flow index is 3.0 g / 10 min (190 ℃, 2.16 kg); the particle size of the conductive carbon black is 30 nm, the oil absorption value is 174 cc / 100 g, and the ash content is ≤0.1%; the additives include 1 g of antioxidant and 1.5 g of dispersant, the antioxidant is antioxidant 300, and the dispersant is ethylene bis-stearamide.

[0086] Comparative Example 5 A non-crosslinked polyethylene semiconductive shielding material, differing from Example 1, comprises, per 100 g total weight, 72.5 g of matrix resin, 25 g of conductive carbon black, and 2.5 g of additives. The matrix resin comprises linear low-density polyethylene (LLDPE) and polyolefin elastomer (POE) in a mass ratio of 9:1; the LLDPE is Borealis FB2230 with a density of 0.923 g / cm³. 3 The melt flow index is 0.25 g / 10 min (190 °C, 2.16 kg); the POE is Dow Chemical 8450, with a density of 0.9 g / cm³. 3 The melt flow index is 3.0 g / 10 min (190 ℃, 2.16 kg); the particle size of the conductive carbon black is 30 nm, the oil absorption value is 174 cc / 100 g, and the ash content is ≤0.1%; the additives include 1 g of antioxidant and 1.5 g of dispersant, the antioxidant is antioxidant 300, and the dispersant is ethylene bis-stearamide.

[0087] Comparative Example 6 A non-crosslinked polyethylene semi-conductive shielding material, differing from Example 1, comprises, per 100 g total weight, 72.5 g of matrix resin, 25 g of conductive carbon black, and 2.5 g of additives. The matrix resin comprises linear low-density polyethylene (LLDPE) and ethylene-vinyl acetate copolymer (EVA) in a mass ratio of 8:2; the LLDPE is Borealis FB2230 with a density of 0.923 g / cm³. 3 The melt flow index was 0.25 g / 10 min (190 ℃, 2.16 kg); the density of the ethylene-vinyl acetate copolymer (EVA) was 0.951 g / cm³. 3 The melt index is 3.0 g / 10 min (190 ℃, 2.16 kg), and the vinyl acetate (VA) content is 28%. The conductive carbon black has a particle size of 30 nm, an oil absorption value of 174 cc / 100 g, and an ash content of ≤0.1%. The additives include 1 g of antioxidant and 1.5 g of dispersant. The antioxidant is antioxidant 300, and the dispersant is ethylene bis-stearamide.

[0088] Comparative Example 7 A non-crosslinked polyethylene semi-conductive shielding material, differing from Example 1, comprises, per 100 g total weight, 72.5 g of matrix resin, 25 g of conductive carbon black, and 2.5 g of additives. The matrix resin comprises linear low-density polyethylene (LLDPE) and ethylene-butyl acrylate copolymer (EBA) in a mass ratio of 8:2; the LLDPE is Borealis FB2230 with a density of 0.923 g / cm³. 3The melt flow index was 0.25 g / 10 min (190 ℃, 2.16 kg); the density of the ethylene-butyl acrylate copolymer (EBA) was 0.930 g / cm³. 3 The melt index is 2.0 g / 10 min (190 ℃, 2.16 kg), and the butyl acrylate (BA) content is 30%. The conductive carbon black has a particle size of 30 nm, an oil absorption value of 174 cc / 100 g, and an ash content of ≤0.1%. The additives include 1 g of antioxidant and 1.5 g of dispersant. The antioxidant is antioxidant 300, and the dispersant is ethylene bis-stearamide.

[0089] Table 2 - Components and contents of non-crosslinked polyethylene semiconductive shielding materials in the embodiments and comparative examples of this application Performance testing The non-crosslinked polyethylene semiconductive shielding materials prepared in the above examples and comparative examples were made into test samples for performance testing. The sample preparation steps were as follows: the required mass of semiconductive shielding material was placed into the sample mold in the flat vulcanizing machine, preheated at 180 ℃ and 5 MPa for 4 min, and then hot-pressed at 180 ℃ and 10 MPa for 10 min to obtain the test sample of non-crosslinked polyethylene cable semiconductive shielding material.

[0090] 1. Torque Test: The torque was tested using the mixing chamber of the German Polylab QC torque rheometer at 160 ℃ and different speeds of 10-50 rpm. Figure 1 The torque-speed relationship of the test samples of Example 1 and Comparative Examples 1-3 at 160 °C is shown in Table 3. Meanwhile, the torques of the test samples of the Examples and Comparative Examples measured at 160 °C and 20 rpm are shown in Table 3. The torque-speed relationship measured by the torque rheometer can represent the rheological properties of a material under applied shear force. Torque reflects the degree of resistance of a material to externally applied shear stress. The smaller the torque, the less the material resists shear stress, and the better the material's fluidity at high temperatures. Therefore, the magnitude of the torque reflects the rheological characteristics of the material. Materials with larger torques have higher viscosity, but their disadvantages include difficult processing, high processing energy consumption, lack of elasticity, and potential brittleness. Materials with smaller torques have better elasticity and flexibility, are easier to shape and process, and require less processing energy, but their disadvantage may be lower strength.

[0091] 2. Tensile curve and elongation at break test: The CMT4503-5kN microcomputer-controlled electronic universal testing machine of Dongguan Yitong Testing Equipment Technology Co., Ltd. was used to test the samples of Examples 1-9 and Comparative Examples 1-6 in accordance with GB / T 1040.2-2006. Figure 2 The stretching curve of Example 1 is shown. Figure 3 The tensile curve of Comparative Example 2 is shown, and the elongation at break of the Examples and Comparative Examples are shown in Table 3 below.

[0092] 3. Volume resistivity: At room temperature, the test samples of the examples and comparative examples were tested using a four-electrode system. Referring to the GB / T 1551-2009 standard, the testing instrument was the DX200H four-probe conductor / semiconductor resistivity tester from Xi'an Honghu Testing Instruments Co., Ltd. The test results are shown in Table 3 below.

[0093] 4. DSC Test: DSC tests were performed using a TA DSC Q2000 thermal flow differential scanning calorimeter (USA) to analyze the samples from Example 1 and Comparative Examples 1 and 4. The sample mass was 5 mg, and nitrogen gas was introduced at a flow rate of 50 mL / min as a protective atmosphere. The DSC curve comparison results are shown below. Figure 4 As shown.

[0094] 5. XRD Testing: The samples from Example 1 and Comparative Examples 4-5 were scanned using a D8 ADVANCEA 25 X-ray diffractometer. The measurement range (2θ) was 10°-50°, the X-ray wavelength was 0.154 nm, the voltage and current were set to 40 V and 40 A respectively, and the sampling interval was 0.2 s. The XRD patterns obtained are shown below. Figure 5 As shown.

[0095] 6. Electron Microscopy Testing: The sample from Example 1 was cut into strips of 20×5×1 mm, immersed in liquid nitrogen for 5 min until it reached a glassy state, and then fractured brittlely, yielding a smooth low-temperature brittle fracture surface. The low-temperature brittle fracture surface of the sample was observed using an electron microscope to determine the dispersion of carbon black particles. Figure 6 The microscopic results of the low-temperature brittle fracture surface of the semiconductive shielding material prepared in Example 1 are shown.

[0096] Table 3 - Performance test results of the semiconductive shielding materials in the embodiments and comparative examples of this application like Figure 1The torque-speed relationship graph shows that the torque of Example 1 and Comparative Examples 1-3 increases with the increase of speed, which is consistent with the rheological characteristics of polymer composite materials of non-Newtonian fluids. This indicates that the semi-conductive shielding material used in this application reduces the viscosity of the material at the same temperature and shear rate due to the change of the matrix resin, but does not change the rheological characteristics of the fluid.

[0097] As shown in Table 3, compared with Example 1, Comparative Example 1 did not add POE elastomer. Although Comparative Example 1 has excellent electrical and mechanical properties, low volume resistivity and high elongation at break, its torque is large and its flowability is too poor, resulting in poor processability. This shows that adding POE to LLDPE helps to improve the processing performance of semiconductive shielding materials.

[0098] As shown in Table 3 and Figure 2-3 As shown, compared to Example 1, Comparative Example 2 uses high-density polyethylene to replace linear low-density polyethylene in an equal amount. By testing the stress-strain curves of multiple samples from Example 1 and Comparative Example 2 under tension, the average value of the elongation at break is obtained to reflect the difference in mechanical properties of the semiconductive shielding materials. The tensile curve of Comparative Example 2 shows that its average elongation at break is about 52%, and the data dispersion is very large, indicating that its mechanical properties are worse than those of Example 1.

[0099] As shown in Table 3, compared with Example 1, the shielding material prepared in Comparative Example 3 uses a blend of high melt index LLDPE and POE as the matrix resin. Although the material has good rheological properties and low volume resistivity, its elongation at break is too low. This is because LLDPE with a high melt index is used, which often has shorter molecular chains or fewer long branches, reducing the physical entanglement effect between molecules. After adding conductive carbon black for dispersion, the slippage ability between molecular chains under tension is further reduced, resulting in poorer material ductility and a significant decrease in mechanical properties. This illustrates the necessity of using low melt index linear low-density polyethylene in this application.

[0100] like Figure 4 As shown, the DSC curves of Example 1 and Comparative Example 1 are similar, both showing a single melting peak at a melting temperature of approximately 126 °C. This indicates that, compared to Comparative Example 1, the melting temperature of the semiconductive shielding material is almost unaffected by the addition of an appropriate amount of POE, ensuring the material's heat resistance. However, in Comparative Example 4, when the amount of POE added exceeds the limits specified in this application, the DSC melting curve of Comparative Example 4 shows two melting peaks, with one peak near a lower temperature of 97 °C. This indicates that the heat resistance of the semiconductive shielding material in Comparative Example 4 is somewhat reduced.

[0101] like Figure 5As shown, the X-ray diffraction patterns of the semiconductive shielding materials in Examples 1 and Comparative Examples 4-5 after adding POE still exhibit the crystalline characteristics of LLDPE, showing peaks at 2θ = 21.4° and 23.8° on the XRD patterns. These peaks correspond to the (110) and (200) crystal planes of polyethylene crystals, indicating that changing the matrix resin ratio does not change the basic crystalline structure of the material. Based on the half-width at half-maximum and angle of the diffraction peaks on the XRD patterns, the average grain size of the matrix resin in the semiconductive shielding material was approximately calculated. According to the Scherrer equation, the average grain sizes of Examples 1, Comparative Examples 4, and Comparative Examples 5 were 16.2 nm, 17.1 nm, and 15.4 nm, respectively. The proportion of POE in the matrix resin of Examples 1 and Comparative Examples 4-5 gradually increased, indicating that the higher the POE content, the smaller the grain size of the semiconductive shielding material. This shows that the different POE contents in the matrix resin do indeed affect the microstructure of the semiconductive shielding material, thereby affecting its electrical and mechanical properties.

[0102] As shown in Table 3, compared to Example 1, the POE content in the matrix resin of Comparative Example 4 is too high. Although the material has the best processing performance, the excessive POE leads to an excessively high volume resistivity. This is because the addition of POE elastic resin reduces the crystallinity of the matrix resin in the semiconductive shielding material and increases the content of amorphous regions. While this helps to improve the uniformity of conductive carbon black dispersion, it reduces the effective conductive path, resulting in an increase in the DC resistivity of the semiconductive shielding material. The higher the POE content, the greater the DC resistivity of the shielding material, and the greater the increase in resistivity of the semiconductive shielding material at high temperatures, which does not meet the requirements for cable shielding materials.

[0103] As shown in Table 3, compared with Example 1, the POE content in the matrix resin of Comparative Example 5 is too low. Although the DC resistivity and mechanical strength of the semiconductive shielding material are good, the torque is too high, indicating that the added POE is not enough to fully improve the processing performance of the shielding material.

[0104] As shown in Table 3, compared to Example 1, Comparative Examples 6-7 used EVA and EBA instead of POE elastomers, respectively. In Example 1 of this application, POE is a pure nonpolar elastomer, and its molecular chain structure is highly compatible with LLDPE. The two can achieve homogeneous dispersion at the molecular level through blending. However, EVA and EBA in Comparative Examples 6-7 contain polar ester side chains, which have poor compatibility with LLDPE and can only exist in the form of micron-scale dispersed phases. In the semiconductive shielding material system of this invention, conductive carbon black tends to be distributed in the amorphous region. When EVA / EBA exists as a dispersed phase, the carbon black preferentially aggregates at the interface rather than forming a continuous conductive network.

[0105] As shown in Table 3, compared with Example 1, the conductive carbon black in the semiconductive shielding materials of Examples 9-10 has a larger oil absorption value of 290-330 cc / 100 g. This high oil absorption carbon black has a high structure and large specific surface area, which is conducive to the formation of conductive pathways and makes the volume resistivity of Examples 9-10 lower than that of Example 1. However, the high structure of the carbon black particles has strong van der Waals forces and is prone to agglomeration, which leads to a gradual increase in melt flow resistance. At the same time, the number of polar groups on the carbon black surface increases, which catalyzes the oxidative degradation of polyethylene molecular chains during processing and aging, causing the elongation at break to decrease from 458% to 442% and 401%.

[0106] In summary, the semiconductive shielding materials of this application exhibit superior overall performance across various aspects, demonstrating excellent volume resistivity and elongation at break, as well as low torque. The material prepared in Example 1 demonstrates the best performance. Figure 6 The scanning electron microscope image of Example 1 shows that the carbon black is uniformly dispersed. In this application, an appropriate amount of POE is added to the LLDPE matrix resin. Although the elongation at break of the semiconductive shielding material decreases somewhat, the elongation at break in all examples is above 400%, indicating a weak impact. Conductive carbon black tends to disperse in the amorphous region, which has a certain impact on the compatibility of POE and LLDPE, leading to a slight decrease in elongation at break. If the POE content is too high, it will increase the volume resistivity of the semiconductive shielding material; if the POE content is too low, the melt viscosity of the corresponding semiconductive shielding material will increase, resulting in poor processability. Therefore, using LLDPE and POE as the matrix resin for the semiconductive shielding material results in a more uniform distribution of conductive carbon black, possessing superior electrical properties (volume resistivity below 50 Ω·cm) and rheological properties (torque less than 10 N·m), exhibiting excellent electrical and rheological properties.

[0107] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of this application. It should be understood that the above descriptions are merely specific embodiments of this application and are not intended to limit the scope of protection of this application. In particular, it should be noted that any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the scope of protection of this application for those skilled in the art.

Claims

1. A non-crosslinked polyethylene semiconductive shielding material, characterized in that, Based on 100 parts by weight, it includes the following components: Matrix resin: 62-78 parts; Conductive carbon black: 20-35 parts; Additives: 2-6 parts; The matrix resin comprises linear low-density polyethylene and polyolefin elastomer in a mass ratio of (7-8.5):(1.5-3), wherein the linear low-density polyethylene has a melt index ≤1g / 10 min at 190 ℃ and 2.16 kg.

2. The non-crosslinked polyethylene semiconductive shielding material as described in claim 1, characterized in that, The oil absorption value of the conductive carbon black is 150-300 cc / 100 g; And / or, the particle size of the conductive carbon black is 10-50 nm; And / or, the ash content of the conductive carbon black is ≤0.01%.

3. The non-crosslinked polyethylene semiconductive shielding material as described in claim 2, characterized in that, The oil absorption value of the conductive carbon black is 150-200 cc / 100 g; And / or, the particle size of the conductive carbon black is 12-30 nm.

4. The non-crosslinked polyethylene semiconductive shielding material as described in claim 1, characterized in that, The linear low-density polyethylene has a melt index of 0.1-0.6 g / 10 min at 190 ℃ and 2.16 kg. And / or, the linear low-density polyethylene has a density of 0.91 g / cm³. 3 -0.94 g / cm 3 .

5. The non-crosslinked polyethylene semiconductive shielding material as described in claim 1, characterized in that, The polyolefin elastomer has a melt index of 2-4 g / 10 min at 190 °C and 2.16 kg. And / or, the density of the polyolefin elastomer is 0.8 g / cm³. 3 -1 g / cm 3 .

6. The non-crosslinked polyethylene semiconductive shielding material as described in claim 1, characterized in that, The conductive carbon black is in the form of 25-30 parts by weight.

7. The non-crosslinked polyethylene semiconductive shielding material as described in claim 1, characterized in that, The additives include at least one of antioxidants, dispersants, antistatic agents, and heat stabilizers.

8. The non-crosslinked polyethylene semiconductive shielding material as described in claim 1, characterized in that, The adjuvants include 0.5-3 parts by weight of antioxidant and 1-3 parts by weight of dispersant.

9. A method for preparing a non-crosslinked polyethylene semiconductive shielding material as described in any one of claims 1-8, characterized in that, Includes the following steps: (1) The additives include antioxidants and dispersants. The matrix resin and antioxidants are mixed evenly and then melt-blended once. The mixture is then extruded by a twin-screw extruder, cold-cut, granulated, and dried to obtain a premix. (2) The conductive carbon black and the dispersant are mixed evenly to obtain a carbon black mixture. The premix is ​​heated and stirred to melt, and then the carbon black mixture is added for secondary melting and blending to obtain a shielding material mixture. (3) The shielding material mixture is extruded, cooled and granulated to obtain a non-crosslinked polyethylene semiconductive shielding material.

10. The application of a non-crosslinked polyethylene semiconductive shielding material as described in any one of claims 1-8 in the preparation of cable materials.

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