A multi-stage synergistic grafting crosslinked polyethylene composite insulating material, a preparation method thereof and application thereof in water tree resistance
By constructing a POE-g-MAH – nylon shell – SiO2 nanocore structure through multi-level synergistic grafting technology, the bottleneck in improving the water tree resistance of XLPE insulation material was solved, and a comprehensive improvement in high electrical strength, low dielectric loss and excellent mechanical properties was achieved.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- CHINA THREE GORGES PROJECTS DEV CO LTD
- Filing Date
- 2026-03-17
- Publication Date
- 2026-05-29
AI Technical Summary
In the existing technology, there is a bottleneck in improving the water tree resistance of cross-linked polyethylene (XLPE) insulation materials. Traditional methods are prone to migration and agglomeration, and have weak interfaces, resulting in unsustainable performance and limited adjustment of charge trapping and mechanical stress.
By employing multi-level synergistic grafting technology, a stable three-dimensional composite structure was constructed, in which polyolefin elastomer was grafted with maleic anhydride (POE-g-MAH) as a flexible bridge, nylon copolymer as a polar network, and aminated silica (SiO2) as nano-reaction and physical barrier points. This achieved chemical bonding and structural synergy, and a multi-level synergistic grafted cross-linked polyethylene composite insulation material was prepared.
It achieves long-lasting resistance to water treeing, high electrical strength, low dielectric loss and excellent mechanical properties, completely eliminates phase separation and additive migration problems, and improves the overall performance of the material.
Smart Images
Figure CN122103718A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the technical field of high-voltage cable insulation materials, and relates to an organic-inorganic multi-level synergistic grafting modification technology. This technology can significantly improve the long-term water tree resistance and comprehensive electrical properties of cross-linked polyethylene. Specifically, it relates to a multi-level synergistic grafted cross-linked polyethylene composite insulation material, its preparation method, and its application in water tree resistance. Background Technology
[0002] Cross-linked polyethylene (XLPE) is the mainstream insulation material for high-voltage power cables, but the "water treeing" aging that occurs during use is a major threat to its long-term reliability. To improve the water treeing resistance of XLPE insulation, the traditional technical approach is to add small-molecule polar additives or single nanofillers. However, this technology has problems such as easy migration, easy agglomeration, and weak interface with the matrix, which leads to unsustainable performance of XLPE insulation or causes new insulation weaknesses.
[0003] Existing methods also explore grafting modification techniques to improve the water-tree resistance of XLPE insulation materials, such as single polymer grafting (e.g., PE-g-MAH). While this method improves compatibility, it still faces limitations in enhancing water-tree resistance and has limited ability to regulate charge trapping and mechanical stress. Therefore, constructing a stable, multi-layered composite system that can simultaneously conduct moisture, suppress electrical tree initiation, passivate electric field concentration, and enhance interfacial bonding is a key technological challenge. Summary of the Invention
[0004] The purpose of this invention is to solve the aforementioned problems in the prior art, and to propose a multi-level synergistic grafted cross-linked polyethylene composite insulation material, its preparation method, and its application in water-tree resistance. This invention constructs a stable three-dimensional composite structure using a chemical method, with polyolefin elastomer grafted with maleic anhydride (POE-g-MAH) as a flexible bridge, nylon copolymer as a polar network, and aminated silica (SiO2) as nano-reaction and physical barrier points. Through an innovative preparation process, chemical bonding and structural synergy of the three components at the molecular / nanoscale are achieved, fundamentally realizing the composite insulation material's long-lasting water-tree resistance, high electrical strength, low dielectric loss, and excellent mechanical properties.
[0005] The technical solution of this invention is: This invention provides a method for preparing a multi-level synergistic grafted cross-linked polyethylene composite insulation material, comprising the following steps: (1) Aminated silica (NH2-SiO2) nanoparticles were uniformly dispersed in anhydrous ethanol, and nylon copolymer solution was added. Under the action of a catalyst, the mixture was stirred at 60~80℃ for 4~8 hours. After the reaction was completed, the mixture was washed, filtered, and vacuum dried to obtain powdered SiO2@Nylon composite. (2) Maleic anhydride grafted polyolefin elastomer (POE-g-MAH) and SiO2@Nylon powder obtained in step (1) are mixed in a weight ratio of (5:1) to (1:1) and melt-blended at 160 to 190°C for 5 to 15 minutes to obtain ternary grafted masterbatch POE-g-MAH / SiO2@Nylon; (3) Mix the low-density polyethylene matrix resin, the ternary grafted masterbatch POE-g-MAH / SiO2@Nylon obtained in step (2), crosslinking agent, antioxidant, and other processing aids in proportion, melt blend at 120~150℃, and extrude granulate to obtain the composite insulation material.
[0006] Furthermore, in step (1), the catalyst is 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride (EDC), and the mass ratio of the aminated silica nanoparticles to the nylon copolymer and the catalyst EDC is 1:1:0.5.
[0007] Furthermore, the average particle size of the aminated silica nanoparticles in step (1) is 10~50 nm, and the amino content is 0.5~2.0 mmol / g.
[0008] Furthermore, the nylon copolymer is at least one of nylon 6 / 6, nylon 6 / 12, or nylon 6 / 10 copolymer, and its relative viscosity is 2.0 to 2.8; the nylon copolymer solution is a solution obtained by dissolving the nylon copolymer in formic acid or m-cresol.
[0009] Furthermore, in step (2), the grafting rate of maleic anhydride in the maleic anhydride-grafted polyolefin elastomer is 0.8%-1.5%.
[0010] Further, in step (3), the reactants are premixed uniformly according to the following ratio: 100 parts of low-density polyethylene matrix resin, 3-15 parts of ternary grafted masterbatch, 1.5-2.5 parts of crosslinking agent, 0.3-1.0 parts of antioxidant, and 0.1-0.5 parts of other processing aids; wherein: The crosslinking agent is dicumyl peroxide (DCP); the antioxidants include 4,4'-thiobis(6-tert-butyl-3-methylphenol) (antioxidant 300), pentaerythritol ester [β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] (antioxidant 1010) or octadecyl ester of β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate (antioxidant 1076); the other processing aids include the molecular weight regulator 2,4-diphenyl-4-methyl-1-pentene (AMSD).
[0011] The present invention also provides a multi-level synergistic grafted cross-linked polyethylene composite insulation material, wherein the multi-level synergistic grafted cross-linked polyethylene composite insulation material is prepared by any of the preparation methods described above.
[0012] The present invention further provides the application of the multi-level synergistic grafted cross-linked polyethylene composite insulation material prepared by any of the above-described preparation methods, or the application of the multi-level synergistic grafted cross-linked polyethylene composite insulation material in the preparation of water-tree resistant cables.
[0013] Furthermore, the composite insulation material is used to manufacture high-voltage cross-linked polyethylene insulated power cables with a rated voltage of 6 kV and above, and the resulting cables have anti-water treeing properties.
[0014] Furthermore, the composite insulation material is used to manufacture 35 kV to 220 kV high voltage and ultra-high voltage cross-linked polyethylene insulated power cables with water tree resistance.
[0015] The beneficial effects of this invention are: This invention creatively constructs a multi-level chemical bonding structure of "POE-g-MAH – nylon shell – SiO2 nanonucleus" to achieve synergistic enhancement of water tree resistance and mechanical properties in cross-linked polyethylene composite insulation materials.
[0016] In terms of multi-level water conduction and blocking: the nylon shell, as a strongly polar phase, can uniformly and stably adsorb and bind water molecules, preventing them from aggregating and forming high-field-strength water nuclei under an electric field; the imide bond between POE-g-MAH and nylon, and the amide bond between nylon and SiO2, form a strong interface without weaknesses, completely eliminating the phase separation and additive migration problems of traditional blends, and ensuring the permanence of performance; the nano-SiO2 core, as a rigid physical barrier, can effectively pin and deflect the growth path of water trees, preventing their penetrating development.
[0017] In terms of electric field homogenization and charge trap optimization: the nano-core-shell structure, as a well-dispersed nanoscale dielectric unit, can homogenize the micro electric field inside the polyethylene matrix and reduce local field concentration; the unique interface region generated by the nylon / SiO2 interface and chemical bonding can introduce a large number of deep charge traps, capture and bind high-energy charge carriers (such as injected electrons), significantly reduce electrical current and space charge accumulation, thereby significantly reducing dielectric loss (tanδ) and improving insulation reliability under DC.
[0018] In terms of synergistic enhancement of mechanical properties: the POE-g-MAH flexible bridge flexibly connects the rigid nano core-shell unit with the LDPE matrix, which can induce crazes and shear bands when subjected to stress, absorbing a large amount of energy; the stiffening effect of the nylon shell can improve the modulus and heat resistance of the material.
[0019] Ultimately, the composite material achieved a perfect balance between toughness and rigidity, polarity and non-polarity, and organic and inorganic properties, with overall performance far exceeding that of simple blending systems. Attached Figure Description
[0020] Figure 1 This is a schematic diagram illustrating the preparation process of the core-shell structured nanocomposite (SiO2@Nylon). Figure 2 This is a schematic diagram of the structure of the multi-level grafted synergistic water tree-resistant composite insulation material of the present invention (showing POE-g-MAH / SiO2@Nylon composite units dispersed in the LDPE matrix and connected by chemical bonds). Figure 3 A comparison curve of dielectric loss tangent (tanδ) for each sample under an electric field of 30 kV / mm; Figure 4 Microscopic images comparing the water tree morphology of the example and the comparative sample. Detailed Implementation
[0021] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.
[0022] To further understand the present invention, it will be further described in conjunction with the accompanying drawings and embodiments.
[0023] This invention provides a method for preparing a multi-level synergistic grafted cross-linked polyethylene composite insulation material, comprising the following steps: Step 1: Preparation of core-shell structured nanocomposite (SiO2@Nylon) Preparation steps are as follows Figure 1 As shown, aminated silica nanoparticles (NH2-SiO2) with an average particle size of 10-50 nm and an amino content of 0.5-2.0 mmol / g were uniformly ultrasonically dispersed in anhydrous ethanol. Nylon copolymer dissolved in formic acid or m-cresol solution was added. Under the action of a catalyst, the mixture was stirred at 60-80℃ for 4-8 hours, causing the carboxyl or amino groups at the nylon chain ends to undergo amidation or ionic bonding with the amino groups on the surface of NH2-SiO2, forming a "core-shell structured nanocomposite" with SiO2 as the core and nylon copolymer as the molecular shell. After the reaction, the mixture was washed, filtered, and vacuum dried to obtain powdered SiO2@Nylon composite.
[0024] Step 2: Preparation of ternary grafted masterbatch (POE-g-MAH / SiO2@Nylon) A polyolefin elastomer grafted with maleic anhydride (POE-g-MAH) at a grafting rate of 0.8%-1.5% was mixed with the SiO2@Nylon core-shell composite obtained in step 1 at a weight ratio of (5:1) to (1:1), and melt-blended at 160-190°C for 5-15 minutes. In the molten state, the anhydride groups (-MAH) on the POE-g-MAH molecular chain react in situ with the amino groups (-NH2) at the ends of the nylon molecular chains in the core-shell composite, generating imide bonds. This achieves chemical bonding between the POE chain and SiO2@Nylon, resulting in the composite as shown below. Figure 2 The interface shown is a robust ternary grafted masterbatch.
[0025] Step 3: Preparation of composite insulation material 100 parts of low-density polyethylene (LDPE) matrix resin, 3-15 parts of the ternary grafted masterbatch (POE-g-MAH / SiO2@Nylon) obtained in step 2, 1.5-2.5 parts of crosslinking agent, 0.3-1.0 parts of antioxidant, and 0.1-0.5 parts of other processing aids are premixed according to the weight ratio, melt-blended at 120-180℃, and extruded and granulated to obtain the composite insulation material.
[0026] This invention provides three embodiments and two comparative examples (the formulations of which are shown in Table 1) for preparing insulating materials. All samples were molded and cross-linked under the same conditions to form standard test pieces.
[0027] Example 1 This embodiment provides a method for preparing a multi-level synergistic grafted cross-linked polyethylene composite insulation material, including the following steps: (1) Preparation of core-shell structured nanocomposite (SiO2@Nylon): 25 kg of aminated SiO2 nanoparticles were weighed and added to anhydrous ethanol for ultrasonic dispersion. The nanoparticles were then uniformly dispersed in anhydrous ethanol. Then, a solution of formic acid containing 25 kg of nylon 6 / 6 was added to the solution. 12.5 kg of EDC was added to the solution, and the mixture was stirred at 70 °C for 6 hours. After the reaction was completed, the nanoparticles were washed, filtered, and vacuum dried to obtain powdered SiO2@Nylon composite. (2) Preparation of ternary grafted masterbatch (POE-g-MAH / SiO2@Nylon): POE-g-MAH and the SiO2@Nylon powder obtained in step (1) are added to a mixer or twin-screw extruder in a weight ratio of 3:1. They are melt-blended at 180°C for 10 minutes to allow MAH and -NH2 to react fully. The mixture is then extruded and granulated to obtain the ternary grafted masterbatch POE-g-MAH / SiO2@Nylon. (3) Preparation of composite insulation material: The LDPE matrix resin, the ternary grafted masterbatch obtained in step (2), the crosslinking agent DCP, the antioxidant 300, and the molecular weight regulator AMSD are added into a high-speed mixer according to the weight proportions in Table 1 and premixed evenly. Then, the mixture is melt-blended, extruded and granulated, cooled and granulated by a twin-screw extruder at 140°C (the die head temperature must be lower than the decomposition temperature of the crosslinking agent) to obtain the composite insulation material.
[0028] Example 2 This embodiment provides a method for preparing a multi-level synergistic grafted cross-linked polyethylene composite insulation material, including the following steps: (1) Preparation of core-shell structured nanocomposite (SiO2@Nylon): 10 kg of aminated SiO2 nanoparticles were weighed and added to anhydrous ethanol for ultrasonic dispersion. The particles were then uniformly dispersed in anhydrous ethanol. Then, a solution of m-cresol containing 10 kg of nylon 6 / 12 was added. 5 kg of EDC was added to the solution, and the mixture was stirred at 60 °C for 4 hours. After the reaction was completed, the particles were washed, filtered, and vacuum dried to obtain powdered SiO2@Nylon composite. (2) Preparation of ternary grafted masterbatch (POE-g-MAH / SiO2@Nylon): Add POE-g-MAH and SiO2@Nylon powder obtained in step (1) in a weight ratio of 5:1 to a mixer or twin-screw extruder, melt-blend at 160°C for 15 minutes to allow MAH and -NH2 to react fully, then extrude and granulate to obtain ternary grafted masterbatch POE-g-MAH / SiO2@Nylon. (3) Preparation of composite insulation material: The LDPE matrix resin, the ternary grafted masterbatch obtained in step (2), the crosslinking agent DCP, the antioxidant 1010, and the molecular weight regulator AMSD are added into a high-speed mixer according to the weight proportions in Table 1 and premixed evenly. Then, the mixture is melt-blended, extruded and granulated, cooled and granulated by a twin-screw extruder at 120°C (the die head temperature must be lower than the decomposition temperature of the crosslinking agent) to obtain the composite insulation material.
[0029] Example 3 This embodiment provides a method for preparing a multi-level synergistic grafted cross-linked polyethylene composite insulation material, including the following steps: (1) Preparation of core-shell structured nanocomposite (SiO2@Nylon): 25 kg of aminated SiO2 nanoparticles were weighed and added to anhydrous ethanol for ultrasonic dispersion. The nanoparticles were then uniformly dispersed in anhydrous ethanol. Then, a solution containing 25 kg of nylon 6 / 10 in formic acid or m-cresol was added. 12.5 kg of EDC was added to the solution, and the mixture was stirred at 80 °C for 8 hours. After the reaction was completed, the nanoparticles were washed, filtered, and vacuum dried to obtain powdered SiO2@Nylon composite. (2) Preparation of ternary grafted masterbatch (POE-g-MAH / SiO2@Nylon): Add POE-g-MAH and SiO2@Nylon powder obtained in step (1) in a weight ratio of 1:1 into a mixer or twin-screw extruder, melt-blend at 190°C for 5 minutes to allow MAH and -NH2 to react fully, then extrude and granulate to obtain ternary grafted masterbatch POE-g-MAH / SiO2@Nylon. (3) Preparation of composite insulation material: The LDPE matrix resin, the ternary grafted masterbatch obtained in step (2), the crosslinking agent DCP, the antioxidant 1076, and the molecular weight regulator AMSD are added into a high-speed mixer according to the weight proportions in Table 1 and premixed evenly. Then, the mixture is melt-blended, extruded, granulated, cooled, and pelletized by a twin-screw extruder at 150°C (the die head temperature must be lower than the decomposition temperature of the crosslinking agent) to obtain the composite insulation material.
[0030] Table 1. Composite insulation material formulations (parts by weight) for Examples 1-3 and Comparative Examples 1-2
[0031] Note: The masterbatch composition in Examples 1-3 is: POE-g-MAH : SiO2@Nylon = 70:30 (weight ratio), where SiO2 accounts for 30% of SiO2@Nylon.
[0032] Comparative Example 1 Composite insulating materials were prepared using the formula in Table 1 and existing traditional processes, including twin-screw extrusion granulation, mixing, and absorption.
[0033] Comparative Example 2 The preparation method is simple blending, that is, POE-g-MAH, nylon 6 / 6, aminated SiO2 and LDPE are directly melt-blended in one step to prepare composite insulating material.
[0034] The performance of the standard test pieces made from the composite insulating materials of Examples 1-3 and Comparative Examples 1-2 was tested, and the results are shown in Table 2 below.
[0035] Table 2 Performance test results of standard test pieces made from composite insulating materials of Examples 1-3 and Comparative Examples 1-2
[0036] Note: Water tree length: is the average value after aging using the water needle electrode method (5 kV / mm, 20℃, 30 days).
[0037] Analysis of the performance test results in Table 2 shows that: Electrical performance: Test results are as follows Figure 3 As shown, the volume resistivity and breakdown strength of Examples 1 to 3 are significantly higher than those of Comparative Examples 1 and 2, and the tanδ is significantly reduced, demonstrating the superior effect of the multi-level grafting structure in optimizing charge transport and homogenizing the electric field. Comparative Example 2, due to simple blending leading to interface defects, actually experienced a performance decrease.
[0038] Water tree resistance performance: Test results are as follows Figure 4 As shown, the anti-water tree performance (water tree length <50 μm) of Examples 1 to 3 far exceeds that of pure XLPE and is also significantly better than that of simple blend systems (which have the risk of phase separation and migration); this verifies the key role of stable chemical bonding structure in the long-term inhibition of water treeing.
[0039] Mechanical properties: Examples 1 to 3 show that while maintaining high elongation, tensile strength is enhanced, demonstrating a synergistic toughening and strengthening effect of "combining rigidity and flexibility".
[0040] Therefore, it can be seen that the present invention has successfully prepared a high-voltage cable XLPE composite insulation material with excellent water tree resistance and comprehensive performance improvement through ingenious multi-level grafting design, which has significant industrial application prospects.
[0041] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, alterations, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.
Claims
1. A method for preparing a multi-level synergistic grafted cross-linked polyethylene composite insulation material, characterized in that, Includes the following steps: (1) Aminated silica nanoparticles were uniformly dispersed in anhydrous ethanol, and nylon copolymer solution was added. Under the action of a catalyst, the mixture was stirred at 60~80℃ for 4~8 hours. After the reaction was completed, the mixture was washed, filtered, and vacuum dried to obtain powdered SiO2@Nylon composite. (2) The maleic anhydride-grafted polyolefin elastomer and the SiO2@Nylon powder obtained in step (1) are mixed in a weight ratio of (5:1) to (1:1), and melt-blended at 160 to 190°C for 5 to 15 minutes to obtain the ternary grafted masterbatch POE-g-MAH / SiO2@Nylon. (3) Mix the low-density polyethylene matrix resin, the ternary grafted masterbatch POE-g-MAH / SiO2@Nylon obtained in step (2), crosslinking agent, antioxidant, and other processing aids in proportion, melt blend at 120~150℃, and extrude granulate to obtain the composite insulation material.
2. The preparation method according to claim 1, characterized in that, In step (1), the catalyst is 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride, and the mass ratio of the aminated silica nanoparticles to the nylon copolymer and the catalyst is 1:1:0.
5.
3. The preparation method according to claim 1, characterized in that, The average particle size of the aminated silica nanoparticles in step (1) is 10~50 nm, and the amino content is 0.5~2.0 mmol / g; The nylon copolymer is at least one of nylon 6 / 6, nylon 6 / 12 or nylon 6 / 10 copolymer, and its relative viscosity is 2.0 to 2.8; the nylon copolymer solution is a solution obtained by dissolving the nylon copolymer in formic acid or m-cresol.
4. The preparation method according to claim 1, characterized in that, The grafting rate of maleic anhydride in the maleic anhydride-grafted polyolefin elastomer in step (2) is 0.8%-1.5%.
5. The preparation method according to claim 1, characterized in that, In step (3), the reactants are premixed uniformly according to the following ratio: 100 parts of low-density polyethylene matrix resin, 3-15 parts of ternary grafted masterbatch, 1.5-2.5 parts of crosslinking agent, 0.3-1.0 parts of antioxidant, and 0.1-0.5 parts of other processing aids; wherein: The crosslinking agent is dicumyl peroxide; the antioxidant includes 4,4'-thiobis(6-tert-butyl-3-methylphenol), pentaerythritol ester of [β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] or octadecyl ester of β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate; the other processing aids include the molecular weight regulator 2,4-diphenyl-4-methyl-1-pentene.
6. A multi-level synergistic grafted cross-linked polyethylene composite insulation material, characterized in that, The multi-level synergistic grafted cross-linked polyethylene composite insulation material is prepared by the preparation method described in any one of claims 1-5.
7. The application of the multi-level synergistic grafted cross-linked polyethylene composite insulation material prepared by the preparation method according to any one of claims 1-5 or the multi-level synergistic grafted cross-linked polyethylene composite insulation material according to claim 6 in the preparation of water-tree resistant cables.
8. The application according to claim 7, characterized in that, The composite insulation material is used to manufacture high-voltage cross-linked polyethylene insulated power cables with a rated voltage of 6 kV and above, and the resulting cables have anti-water treeing properties.
9. The application according to claim 8, characterized in that, The composite insulation material is used to manufacture 35 kV to 220 kV high voltage and ultra-high voltage cross-linked polyethylene insulated power cables with water tree resistance.