A kind of extra-high voltage direct current epoxy insulating material and its preparation method

Abstract

The application belongs to the technical field of high polymer insulating material, and particularly discloses a kind of UHVDC epoxy insulating material and its preparation method.The core of the method is to introduce fluorine-containing polyrotaxan as a modifier in the epoxy crosslinking system: (1) the surface hydroxyl group of the cyclic main body molecule of fluorine-containing polyrotaxan participates in crosslinking, maintains the structural strength of the material and significantly improves the anti-cracking property. (2) During the curing process, the fluorine element contained in the polyrotaxan spontaneously enriches to the surface layer of the material, forming a superficial fluorine layer. This fluorine layer blocks the migration of carriers in the interior of the material to the surface under the direct current field, and effectively reduces the surface energy of the material, inhibits the adsorption and deposition of environmental impurity particles, and prevents the abnormal accumulation of surface charge through the double mechanism of preventing surface charge abnormal accumulation and avoiding the flashover risk caused by electric field distortion, greatly improving the long-term insulation reliability under the UHVDC operating environment. The problem of insulation failure caused by the easy cracking of epoxy material of the pot-type insulator in high-voltage direct-current GIS and the accumulation of surface charge is solved.

Description

Technical Field

[0001] This invention belongs to the field of polymer insulating materials technology, and specifically discloses an ultra-high voltage DC epoxy insulating material and its preparation method. Background Technology

[0002] In ultra-high voltage direct current (UHVDC) gas-insulated switchgear (GIS), basin-type insulators are key components for achieving mechanical support and electrical isolation, and the long-term reliability of their epoxy materials is crucial. The harsh operating environment of UHVDC places dual core requirements on epoxy materials: excellent crack resistance and superior surface withstand voltage performance. The former stems from the fact that under the complex thermo-mechanical-electric coupling field during long-term service, the insulator is susceptible to structural failure due to the initiation and propagation of microcracks; the latter arises because under the action of a unipolar high-voltage DC electric field, charge carriers (ions, space charges) within the material continuously accumulate on the insulator surface driven by the normal electric field component, coupled with the adsorption of surface impurities, causing severe surface electric field distortion, significantly reducing flashover voltage, and is the main cause of DC insulation failure. These two performance aspects directly determine the mechanical integrity and electrical safety of basin-type insulators, and are the cornerstone for ensuring the stable operation of UHVDC systems.

[0003] Currently, the mainstream methods for improving the surface withstand voltage performance of epoxy insulators focus on surface modification techniques, such as surface fluorination, plasma modification, or spraying with fluorinated coatings, aiming to reduce surface energy and suppress charge accumulation. However, these methods have significant limitations: the drastic intervention of the modification process (especially fluorination or plasma treatment) may damage or even destroy the cross-linked network structure of the epoxy matrix surface, impairing the insulator performance; more importantly, the resulting surface functional layer is mainly based on physical adhesion or shallow reaction, lacking strong chemical bonding with the epoxy matrix. Under long-term electro-thermal-mechanical stress and environmental aging, it is extremely prone to degradation and peeling, resulting in a short-lived and unreliable effect in suppressing charge accumulation, poor timeliness, and difficulty in meeting the lifespan requirements of UHVDC equipment. Therefore, these surface modifications do not contribute sufficiently to improving the crack resistance of the material itself and cannot synergistically address the dual mechanical and electrical challenges faced by pot insulators. Summary of the Invention

[0004] One objective of this invention is to provide an ultra-high voltage direct current epoxy insulation material and its preparation method. The active hydroxyl groups on the surface of polyrotaxane participate in cross-linking, becoming embedded components in the epoxy network. Its unique mechanical interlocking structure effectively dissipates stress through slippage, significantly enhancing the material's crack resistance. Simultaneously, during the curing process, fluorine elements on the polyrotaxane spontaneously migrate and accumulate to the surface, forming a shallow fluorine layer chemically bonded to the matrix. This inhibits carrier migration to the surface and reduces the surface energy of the insulator, decreasing the adsorption of impurity particles. This provides a long-term, stable suppression of surface charge accumulation and simultaneously improves the surface withstand voltage performance.

[0005] To achieve the above objectives, the present invention adopts the following technical solution: a method for preparing ultra-high voltage direct current epoxy insulation material, comprising the following steps:

[0006] S1. Fluorinated cyclodextrin and polyethylene glycol diamine with a molecular weight of 3000-10000 g / mol are dissolved in deionized water. Then, the aqueous solution of fluorinated cyclodextrin is slowly added dropwise to the aqueous solution of polyethylene glycol diamine. After stirring vigorously at 80-100℃, the mixture is naturally cooled to room temperature. The product is freeze-dried to obtain fluorinated quasi-polyrotaxane.

[0007] S2. Fluorinated quasi-polyrotaxane is dissolved in anhydrous N,N-dimethylamide, and the end-capping agent 2,4-dinitrofluorobenzene is slowly added dropwise. The reaction is stirred thoroughly at room temperature. After the reaction is completed, excess acetone is added to precipitate the product. After washing and drying, fluorinated polyrotaxane is obtained.

[0008] S3. The above-mentioned fluorinated polyrotaxane, bisphenol A type epoxy resin, curing agent, and accelerator are thoroughly mixed at 70-90℃ and then degassed under vacuum. The mixture is then poured into a mold and subjected to low-temperature pre-curing and high-temperature curing in sequence. After cooling to room temperature, the mixture is demolded to obtain ultra-high voltage DC epoxy insulation material.

[0009] Further improvements to the preparation method of ultra-high voltage DC epoxy insulation materials:

[0010] Preferably, the mass ratio of fluorinated cyclodextrin to polyethylene glycol diamine in step S1 is (2-5):1.

[0011] Preferably, in step S1, the concentration of fluorinated cyclodextrin in the fluorinated cyclodextrin aqueous solution is 0.06-0.13 g / mL, and the concentration of polyethylene glycol diamine in the polyethylene glycol diamine aqueous solution is 0.02-0.032 g / mL.

[0012] Preferably, in step S2, the concentration of fluorinated quasi-polyrotaxane in anhydrous N,N-dimethylamide is 0.025-0.05 g / mL, and the mass ratio of fluorinated quasi-polyrotaxane to the end-capping agent 2,4-dinitrofluorobenzene is 1:(1-1.5).

[0013] Preferably, in step S3, the mass ratio of fluorinated polyrotaxane to bisphenol A type epoxy resin, curing agent, and accelerator is (3-12):100:(70-100):(0.3-0.6).

[0014] Preferably, the curing agent in step S3 is one of the acid anhydride curing agents.

[0015] Preferably, the curing agent in step S3 is one of methyltetrahydrophthalic anhydride, methylhexahydrophthalic anhydride, and methylnadic anhydride.

[0016] Preferably, the accelerator in step S3 is one of N,N-dimethylbenzylamine and 2,4,6-tris(dimethylaminomethyl)phenol.

[0017] Preferably, in step S3, the temperature for low-temperature pre-curing is controlled at 70-90℃, and the curing time is 4-9 hours; the temperature for high-temperature curing is controlled at 100-130℃, and the curing time is 10-20 hours.

[0018] The second objective of this invention is to provide an ultra-high voltage DC epoxy insulation material prepared by any one of the methods described in the invention.

[0019] The advantages of this invention compared to the prior art are as follows:

[0020] (1) This invention addresses two key technical challenges of existing ultra-high voltage direct current epoxy insulation materials—insufficient bulk crack resistance and poor long-term surface charge suppression capability—by providing a customized molecular network design method. This design is based on the following technical principles:

[0021] Molecular slip dissipation mechanism: Fluorinated polyrotaxane modifiers, chemically bonded and embedded in a cross-linked network, possess a unique cyclic host molecule structure nested on a polymer spool, forming natural molecular-scale "slip ring" units. When the material is subjected to external or internal stress (thermal stress, mechanical stress), these slip ring structures can undergo reversible relative slip motion, dissipating energy through intramolecular friction and highly efficient conformational changes. This nanoscale slip dissipation mechanism can blunt crack tips, effectively preventing the initiation and propagation of microcracks, significantly improving the toughness and resistance to environmental stress cracking of epoxy materials. This mechanism differs from simple toughening agent filling; it relies on the topological characteristics of the modifier itself, enabling it to maintain a high cross-linking density (with polyrotaxane hydroxyl groups participating in the cross-linking reaction) while still possessing excellent stress relaxation capabilities.

[0022] Controllable directional surface enrichment: During the curing and crosslinking process of epoxy resin, the fluorinated groups carried on polyrotaxane are driven by the interfacial energy gradient (low surface energy characteristics), spontaneously migrating and preferentially enriching in the surface region of the material. Crucially, this enrichment process occurs simultaneously with the participation of polyrotaxane in the epoxy crosslinking reaction via hydroxyl groups. This means that the formed fluorine-rich surface layer is not a simple physical coating or adsorption layer, but rather firmly bonded to the epoxy matrix crosslinking network through chemical bonds. This bonding method ensures excellent interfacial adhesion and long-term stability between the fluorine layer and the matrix.

[0023] Charge suppression mechanism: The fluorine-containing layer alters the shallow surface energy level structure of the material, significantly hindering the migration of charge carriers to the surface caused by the normal electric field. This is one of the key factors in improving the surface withstand voltage of the insulator. Furthermore, the shallow fluorine-containing layer imparts extremely low critical surface tension to the material surface, significantly reducing the adsorption tendency of suspended impurity particles in the environment on the insulator surface. This greatly suppresses surface charge carrier accumulation and avoids electric field distortion caused by the additional field strength, thus preventing premature surface flashover.

[0024] (2) Traditional technologies rely on post-treatment modifications to the surface, such as surface fluorination, plasma treatment, or spraying with fluorinated coatings. While these methods can improve surface properties (such as reducing surface energy) in the short term, they have fundamental drawbacks: on the one hand, the intense processing (such as high-energy particle bombardment and strong chemical reactions) can damage or even destroy the cross-linked network structure of the epoxy matrix surface, potentially weakening the material's bulk insulation and mechanical properties; on the other hand, and more importantly, the resulting surface functional layer is mainly based on physical adsorption or shallow physicochemical reactions, lacking a strong chemical bond with the epoxy matrix. Under the long-term electrical, thermal, and mechanical stress cycles and environmental aging effects, it is extremely prone to degradation, peeling, or failure.

[0025] (3) The present invention provides an ultra-high voltage DC epoxy insulation material and its preparation method, which has the following advantages: Fluorinated polyrotaxane is introduced into the epoxy crosslinking network through chemical bonding, achieving synergistic bulk modification. This modifier significantly enhances the material's crack resistance and toughness through the mobility of its molecular slip ring structure; simultaneously, a chemically bonded shallow fluorine layer is spontaneously formed during the curing process. This layer can effectively block bulk charge migration and reduce surface energy to inhibit contaminant adsorption, thus stably suppressing surface charge accumulation. The present invention overcomes the shortcomings of traditional surface treatments, such as high destructiveness, poor timeliness, and inability to synergistically improve performance, enabling the insulation material to possess both excellent crack resistance and insulation strength under ultra-high voltage DC conditions. Detailed Implementation

[0026] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0027] Example 1

[0028] This embodiment provides a method for preparing ultra-high voltage direct current epoxy insulation material, the specific steps of which are as follows:

[0029] S1. Dissolve 20g of fluorinated cyclodextrin and 4g of polyethylene glycol diamine (molecular weight 6000g / mol) in 200mL of deionized water respectively. Then, slowly add the aqueous solution of fluorinated cyclodextrin to the aqueous solution of polyethylene glycol diamine. After stirring vigorously at 80℃ for 2h, cool naturally to room temperature and freeze-dry for 24h to obtain fluorinated quasi-polyrotaxane.

[0030] The molecular structure of fluorinated cyclodextrin is as follows:

[0031] ;

[0032] S2. Dissolve 15g of fluorinated quasi-polyrotaxane in 300mL of anhydrous N,N-dimethylamide, slowly add 15g of end-capping agent 2,4-dinitrofluorobenzene, stir the reaction thoroughly at room temperature, add excess acetone after the reaction is completed to precipitate the product, wash and dry to obtain fluorinated polyrotaxane.

[0033] S3. The above-mentioned fluorinated polyrotaxane (5g) is thoroughly mixed with bisphenol A type epoxy resin (100g), methyltetrahydrophthalic anhydride curing agent (88.9g), and N,N-dimethylbenzylamine accelerator (0.5g) at 80°C and then degassed under vacuum. The mixture is then poured into a mold and subjected to low-temperature pre-curing and high-temperature curing in sequence. The low-temperature pre-curing temperature is 80°C and the time is 7h; the high-temperature curing temperature is 110°C and the time is 16h. After curing, the mixture is naturally cooled to room temperature and then demolded to obtain ultra-high voltage DC epoxy insulation material 1.

[0034] Example 2

[0035] This embodiment provides a method for preparing ultra-high voltage DC epoxy insulation material. The specific steps are the same as in Example 1, except that: in step S1, 13g of fluorinated cyclodextrin and 3.2g of polyethylene glycol diamine (molecular weight of 3000g / mol) are dissolved in 100mL of deionized water respectively; in step S2, the above-mentioned fluorinated quasi-polyrotaxane (12g) is dissolved in 300mL of anhydrous N,N-dimethylamide, and 18g of end-capping agent 2,4-dinitrofluorobenzene is slowly added dropwise.

[0036] Ultimately, ultra-high voltage direct current epoxy insulation material 2 was obtained.

[0037] Example 3

[0038] This embodiment provides a method for preparing ultra-high voltage DC epoxy insulation material. The specific steps are the same as in Example 1, except that: in step S1, 12g of fluorinated cyclodextrin and 6g of polyethylene glycol diamine (molecular weight of 10000g / mol) are dissolved in 200mL of deionized water respectively; in step S2, the above-mentioned fluorinated quasi-polyrotaxane (7.5g) is dissolved in 300mL of anhydrous N,N-dimethylamide, and 9g of end-capping agent 2,4-dinitrofluorobenzene is slowly added dropwise.

[0039] Ultimately, ultra-high voltage direct current epoxy insulation material 3 was obtained.

[0040] Example 4

[0041] This embodiment provides a method for preparing ultra-high voltage DC epoxy insulation material. The specific steps are the same as in Embodiment 1, except that in step S3, the above-mentioned fluorinated polyrotaxane (3g) is thoroughly mixed with bisphenol A type epoxy resin (100g), methyltetrahydrophthalic anhydride curing agent (70g), and N,N-dimethylbenzylamine accelerator (0.3g) at 80°C and then degassed under vacuum; finally, ultra-high voltage DC epoxy insulation material 4 is obtained.

[0042] Example 5

[0043] This embodiment provides a method for preparing ultra-high voltage DC epoxy insulation material. The specific steps are the same as in Embodiment 1, except that in step S3, the above-mentioned fluorinated polyrotaxane (12g) is thoroughly mixed with bisphenol A type epoxy resin (100g), methyltetrahydrophthalic anhydride curing agent (100g), and N,N-dimethylbenzylamine accelerator (0.6g) at 80°C and then degassed under vacuum; finally, ultra-high voltage DC epoxy insulation material 5 is obtained.

[0044] Example 6

[0045] This embodiment provides a method for preparing ultra-high voltage DC epoxy insulation material. The specific steps are the same as in Embodiment 1, except that: in step S3, the low-temperature pre-curing temperature is 90°C and the time is 4 hours; the high-temperature curing temperature is 130°C and the time is 10 hours; finally, ultra-high voltage DC epoxy insulation material 6 is obtained.

[0046] Example 7

[0047] This embodiment provides a method for preparing ultra-high voltage DC epoxy insulation material. The specific steps are the same as in Embodiment 1, except that: in step S3, the low-temperature pre-curing temperature is 70°C and the time is 9 hours; the high-temperature curing temperature is 100°C and the time is 20 hours; finally, ultra-high voltage DC epoxy insulation material 7 is obtained.

[0048] Comparative Example 1

[0049] This embodiment provides a method for preparing ultra-high voltage DC epoxy insulation material. The specific steps are the same as in Embodiment 1, except that steps S1 and S2 are not performed. Instead, bisphenol A type epoxy resin (100g), curing agent (methyltetrahydrophthalic anhydride, 88.9g), and accelerator (N,N-dimethylbenzylamine, 0.5g) are thoroughly mixed at 60°C and then degassed under vacuum. The mixture is then poured into a mold and subjected to low-temperature pre-curing and high-temperature curing in sequence. The low-temperature pre-curing temperature is 80°C for 7 hours, and the high-temperature curing temperature is 110°C for 16 hours. After curing, the material is naturally cooled to room temperature and then demolded to obtain ordinary epoxy insulation material 1.

[0050] Comparative Example 2

[0051] This embodiment provides a method for preparing ultra-high voltage DC epoxy insulation material. The specific steps are the same as in Embodiment 1, except that: in step S1, β-cyclodextrin is used instead of fluorinated cyclodextrin, and then step S2 is performed to obtain ordinary polyrotaxane; then step S3 is performed to obtain ordinary epoxy insulation material 2.

[0052] Comparative Example 3

[0053] This embodiment provides a method for preparing ultra-high voltage DC epoxy insulation material. The specific steps are the same as in Embodiment 1, except that the molecular weight of polyethylene glycol diamine in step S1 is 20000 g / mol.

[0054] Finally, ordinary epoxy insulation material 3 was obtained.

[0055] Comparative Example 4

[0056] This embodiment provides a method for preparing ultra-high voltage DC epoxy insulation material. The specific steps are the same as in Embodiment 1, except that the amount of fluorinated polyrotaxane added in step S3 is 20g; and the ordinary epoxy insulation material 4 is finally obtained.

[0057] Comparative Example 5

[0058] This embodiment provides a method for preparing ultra-high voltage DC epoxy insulation material. The specific steps are the same as in Embodiment 1, except that: in step S3, the low-temperature pre-curing temperature is 100°C and the time is 3 hours; the high-temperature curing temperature is 150°C and the time is 9 hours; finally, ordinary epoxy insulation material 5 is obtained.

[0059] The epoxy insulation samples prepared in the above embodiments and comparative examples were subjected to impact strength tests, surface flashover tests, and withstand voltage tests. The impact strength test followed the national standard GB / T 1043.1-2008. The surface flashover test followed the national standard, using finger electrodes with a spacing of 20 mm, and the test temperature was room temperature. The surface flashover voltage was increased uniformly at a rate of 1 kV / s until surface flashover occurred. The surface withstand voltage duration was achieved by subjecting the sample to a withstand voltage of 0.9 times the surface flashover voltage for an extended period until surface flashover occurred.

[0060] Table 1 Performance tests of epoxy insulation samples prepared in Examples 1-7 and Comparative Examples 1-5

[0061] ;

[0062] As shown in Examples 1-7 of Table 1, by changing variables such as the amount of fluorinated cyclodextrin, the molecular weight of polyethylene glycol diamine, the addition ratio of fluorinated polyrotaxane, the types of curing agents and accelerators, and the curing temperature and time, the preparation method provided in this application can effectively achieve a synergistic improvement in its crack resistance and surface pressure resistance to meet the requirements of ultra-high voltage direct current applications. The mechanism for improving crack resistance is as follows: the surface of fluorinated polyrotaxane is rich in hydroxyl groups, which can participate in the curing process together with the resin and curing agent to form a cross-linked network, which is beneficial to increasing the cross-linking density and maintaining the overall rigidity of the network. Based on the high strength of the network, the special mechanical structure of polyrotaxane enhances the crack resistance of the material. When the insulator is subjected to stress impact during production, installation, and operation, the stress is transferred to the polyrotaxane through the high-strength network. The polyrotaxane undergoes slip motion to relax the stress, hindering the development of cracks caused by the breakage of chemical bonds, thereby achieving a significant improvement in crack resistance. The mechanism for improving surface withstand voltage performance is as follows: During the curing process, due to suitable temperature and time, the fluorinated groups introduced on the surface of polyrotaxane gradually migrate to the surface until curing is complete, forming a fluorinated layer in the shallow surface of the material. This fluorinated layer changes the energy level structure of the shallow surface, hindering electrons migrating from the bulk and reducing the surface charge content. On the other hand, it increases the surface energy of the material, making it difficult for impurity particles to be adsorbed. Under the synergistic effect, the accumulation of surface charge in the insulating material is improved, the degree of electric field distortion is suppressed, and the surface withstand voltage time is increased.

[0063] As shown in Example 1 and Comparative Example 1, ordinary epoxy insulation materials without the introduction of fluorinated polyrotaxane structures have insufficient impact strength and surface withstand voltage duration to meet the requirements of ultra-high voltage direct current (UHVDC) scenarios. As shown in Example 1 and Comparative Example 2, while the introduction of unfluorinated polyrotaxane improves impact strength, its insulation strength still falls short of requirements. As shown in Example 1 and Comparative Example 3, the fluorinated polyrotaxane structure utilizes high-molecular-weight chain polyethylene glycol diamine, but its impact strength improvement is not significant, and its surface withstand voltage duration decreases. This may be because the excessively long chain molecules generate excessive steric hindrance and provide excessive network movement capability. As shown in Example 1 and Comparative Example 4, an excessively high proportion of fluorinated polyrotaxane addition leads to a deterioration in impact strength and surface withstand voltage duration. This may be because the excess fluorinated polyrotaxane structure disrupts the epoxy cross-linked network structure. As shown in Example 1 and Comparative Example 5, inappropriate curing temperature and time cannot effectively allow the fluorinated structure to accumulate in the shallow surface layer of the material during curing, resulting in a minimal improvement in surface withstand voltage duration.

[0064] Those skilled in the art should understand that the above descriptions are merely several specific embodiments of the present invention, and not all embodiments. It should be noted that many modifications and improvements can be made by those skilled in the art, and all modifications or improvements not exceeding the scope of the claims should be considered within the protection scope of the present invention.

Claims

1. A method for preparing an ultra-high voltage direct current epoxy insulating material, characterized in that, Includes the following steps: S1. Fluorinated cyclodextrin and polyethylene glycol diamine with a molecular weight of 3000-10000 g / mol are dissolved in deionized water. Then, the aqueous solution of fluorinated cyclodextrin is slowly added dropwise to the aqueous solution of polyethylene glycol diamine. After stirring vigorously at 80-100℃, the mixture is naturally cooled to room temperature. The product is freeze-dried to obtain fluorinated quasi-polyrotaxane. S2. Fluorinated quasi-polyrotaxane is dissolved in anhydrous N,N-dimethylamide, and the end-capping agent 2,4-dinitrofluorobenzene is slowly added dropwise. The reaction is stirred thoroughly at room temperature. After the reaction is completed, excess acetone is added to precipitate the product. After washing and drying, fluorinated polyrotaxane is obtained. S3. The above-mentioned fluorinated polyrotaxane, bisphenol A epoxy resin, curing agent, and accelerator are thoroughly mixed at 70-90℃ and then degassed under vacuum. The mass ratio of fluorinated polyrotaxane to bisphenol A epoxy resin, curing agent, and accelerator is (3-12):100:(70-100):(0.3-0.6). The mixture is then poured into a mold and subjected to low-temperature pre-curing and high-temperature curing in sequence. The low-temperature pre-curing temperature is controlled at 70-90℃ and the curing time is 4-9 hours. The high-temperature curing temperature is controlled at 100-130℃ and the curing time is 10-20 hours. After cooling to room temperature, the material is demolded to obtain the ultra-high voltage DC epoxy insulation material.

2. The method for preparing an ultra-high voltage direct current epoxy insulation material according to claim 1, characterized in that, In step S1, the mass ratio of fluorinated cyclodextrin to polyethylene glycol diamine is (2-5):

1.

3. A method for preparing an ultra-high voltage direct current epoxy insulating material according to claim 1 or 2, characterized in that, In step S1, the concentration of fluorinated cyclodextrin in the aqueous solution of fluorinated cyclodextrin is 0.06-0.13 g / mL, and the concentration of polyethylene glycol diamine in the aqueous solution of polyethylene glycol diamine is 0.02-0.032 g / mL.

4. A method for preparing an ultra-high voltage direct current epoxy insulating material according to claim 1 or 2, characterized in that, In step S2, the concentration of fluorinated quasi-polyrotaxane in anhydrous N,N-dimethylamide is 0.025-0.05 g / mL, and the mass ratio of fluorinated quasi-polyrotaxane to the end-capping agent 2,4-dinitrofluorobenzene is 1:(1-1.5).

5. The method for preparing an ultra-high voltage direct current epoxy insulating material according to claim 1, characterized in that, The curing agent in step S3 is one of the acid anhydride curing agents.

6. The method for preparing an ultra-high voltage direct current epoxy insulation material according to claim 1, characterized in that, The curing agent in step S3 is one of methyltetrahydrophthalic anhydride, methylhexahydrophthalic anhydride, or methylnadic anhydride.

7. The method for preparing an ultra-high voltage direct current epoxy insulating material according to claim 1, characterized in that, The accelerator in step S3 is one of N,N-dimethylbenzylamine and 2,4,6-tris(dimethylaminomethyl)phenol.

8. An ultra-high voltage direct current epoxy insulation material prepared by the preparation method of an ultra-high voltage direct current epoxy insulation material according to any one of claims 1-7.