Low conductance temperature dependent direct current epoxy resin and preparation method and application thereof

Abstract

This invention belongs to the field of high-voltage insulation technology, specifically disclosing a low-conductivity temperature-dependent DC epoxy resin, its preparation method, and its application. The resin comprises the following components by mass fraction: 100 parts of an epoxy resin matrix blend; 40-110 parts of a curing agent; and 0.001-0.1 parts of an accelerator. The epoxy resin matrix blend includes: 80-97 parts of flexible segment epoxy resin as the matrix; and 3-20 parts of Cardo structure fluorene-type epoxy resin containing high rigidity and thermal stability as a modifier. This invention, using the aforementioned low-conductivity temperature-dependent DC epoxy resin, its preparation method, and its application, achieves optimized control of the internal electric field distribution of high-voltage DC insulation under wide temperature range and large temperature difference conditions, thereby improving equipment operational reliability.

Description

Technical Field

[0001] This invention relates to the field of high voltage insulation technology, and in particular to a low conductivity temperature-dependent DC epoxy resin, its preparation method, and its application. Background Technology

[0002] Epoxy resin is a key insulating material for high-voltage direct current (HVDC) equipment. It is widely used in critical equipment and components such as HVDC bushings, GIS cable terminals, and GIS insulators, undertaking the core tasks of electrical insulation and mechanical support. As HVDC transmission technology develops towards higher voltage levels and larger transmission capacities, the insulation structure of the equipment is constantly increasing, and the reliability requirements are becoming increasingly stringent.

[0003] The insulation design concept of high-voltage direct current (HVDC) equipment still draws to some extent on the field strength control methods of AC equipment, mainly achieving electric field homogenization through geometric optimization. However, there are significant differences between the electric field distribution mechanism of DC insulation structure and AC insulation. Under AC conditions, the electric field distribution inside the insulation is mainly controlled by the dielectric constant and geometric structure of the medium, and the dielectric constant is relatively less affected by temperature. Therefore, when the operating voltage and temperature range are constant, the electric field distribution inside the equipment is relatively stable. Unlike AC equipment, the electric field distribution inside the insulation under DC conditions mainly depends on the conductivity of the material and its spatial distribution, and the conductivity is highly sensitive to temperature. On the one hand, conductors generate significant heat during actual power equipment operation, and the maximum operating temperature of the insulation can reach over 100℃. On the other hand, under high voltage levels (such as ultra-high voltage and extra-high voltage), the epoxy insulation thickness can reach hundreds of millimeters, and the intrinsic thermal conductivity of epoxy resin is low, which inevitably leads to a large temperature gradient from the inside to the outside of the insulation under heavy load conditions. Under these conditions, the conductivity of epoxy resin insulation material changes with temperature in a significantly nonlinear manner, causing the electric field inside the equipment insulation to dynamically migrate, thus deviating from the original design.

[0004] Meanwhile, high-voltage direct current (HVDC) equipment operates in a complex environment, affected by multiple factors such as load current fluctuations, ambient temperature changes, polarity reversal, start-up and shutdown shocks, and space charge accumulation. This results in a stronger dynamic coupling characteristic between the internal temperature field and electric field distribution of the insulation. Especially under conditions of polarity reversal and sudden load changes, the electric field redistribution process lags behind the applied voltage change, easily causing local transient electric stress concentration and significantly increasing the risk of insulation failure.

[0005] For equipment insulation design under DC conditions, the main approach is to trade size for margin, i.e., using insulation dimensions of higher voltage levels for lower voltage level equipment. This method has achieved some temporary success in equipment below 500kV, but it does not fundamentally solve the problem. With the development of ±500kV and higher voltage level DC transmission projects, relying solely on traditional geometric optimization and increased insulation dimensions is insufficient to meet the reliable operation requirements of high-voltage DC equipment. In addition to "shape control," equipment insulation design must also consider "performance control," i.e., by adjusting the DC conductivity and thermal properties of the insulation material to achieve synergistic optimization of the internal electric and temperature fields of the insulation.

[0006] In existing technologies, research on the regulation of electrical conductivity properties of high-voltage direct current (HVDC) epoxy insulation materials mainly focuses on functional filler modification, the introduction of nonlinear conductive materials, and interface coating design. Introducing inorganic micro / nano particles, semi-conductive fillers, or functional molecules into the epoxy matrix can improve the temperature dependence of the material's conductivity and enhance the uniformity of the electric field distribution to some extent. However, these modification techniques still face many problems in practical applications, such as difficulties in filler dispersion, increased system viscosity, complex molding processes, interface parameter mismatch, and decreased breakdown performance. Especially for large-sized and structurally complex HVDC equipment, these issues are more likely to lead to localized defects and long-term reliability problems.

[0007] Therefore, the performance regulation of insulation materials for high-voltage direct current (HVDC) equipment remains a key technical issue that urgently needs to be addressed in this field, and it is of great significance for ensuring the safe operation of HVDC transmission systems. Summary of the Invention

[0008] The purpose of this invention is to provide a low conductivity temperature-dependent DC epoxy resin, its preparation method, and its application, so as to achieve optimized control of the internal electric field distribution of high-voltage DC insulation under wide temperature range and large temperature difference conditions, thereby improving the reliability of equipment operation.

[0009] To achieve the above objectives, the present invention provides a low conductivity temperature-dependent DC epoxy resin, comprising the following components by mass fraction: 100 parts of epoxy resin matrix blend; 40-110 parts of curing agent; Accelerator 0.001~0.1 parts.

[0010] The epoxy resin matrix blends include: 80-97 parts of flexible segment epoxy resin were used as the matrix; 3 to 20 parts of Cardo structure fluorene epoxy resin with high rigidity and thermal stability were used as modifiers.

[0011] The cured product of this epoxy resin composition exhibits excellent electrical insulation, mechanical, and thermal properties. In particular, the cured product shows low temperature dependence on electrical conductivity under DC conditions. Addressing the issue of nonlinear conductivity changes with temperature in high-voltage DC epoxy resin insulation under wide temperature ranges and large temperature gradients, leading to easily distorted electric field distribution, this paper modifies the flexible segment epoxy resin system by using a fluorene-type epoxy resin with a high rigidity, low polarity, and high thermal stability Cardo structure. This modulates the molecular chain rigidity, cross-linking network structure, and carrier transport behavior of the cured system, thereby reducing the dependence of the material's DC conductivity on temperature changes and improving its high-temperature conductivity stability. Simultaneously, by rationally matching anhydride curing agents and accelerators, the resulting epoxy resin composition possesses excellent casting and processing properties, electrical insulation properties, heat resistance, and mechanical properties, making it suitable for the preparation of high-voltage or ultra-high-voltage DC insulation components.

[0012] Preferably, the flexible segment epoxy resin is a general-purpose aromatic epoxy resin or alicyclic epoxy resin with low steric hindrance and no biphenyl structure.

[0013] Preferably, the flexible segmental epoxy resin is one or more selected from electrical bisphenol A type epoxy resin, bisphenol F type epoxy resin, triglycidyl-m-aminophenol, resorcinol diglycidyl ether, 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexylcarboxylate, and 4,4-diaminodiphenylmethane tetraglycidylamine. For example, bisphenol A type epoxy resin or a blend of bisphenol A and resorcinol diglycidyl ether can be used.

[0014] Preferably, the fluorene-type epoxy resin containing the highly rigid and thermally stable Cardo structure has large-volume side groups and high steric hindrance. The fluorene-type epoxy resin is one or more of 9,9-bis[4-(2,3-epoxypropoxyethoxy)phenyl]fluorene, 9,9-bis[(2,3-epoxypropoxy)phenyl]fluorene, and 9,9-bis(6-glycidyloxy-2-naphthyl]fluorene.

[0015] For example, if 80 parts of flexible segment epoxy resin are selected, 20 parts of a highly rigid Cardo structure fluorene-type resin modifier should be used; if 85 parts of flexible segment epoxy resin are selected, 15 parts of a highly rigid Cardo structure fluorene-type resin modifier should be used. 9,9-bis[(2,3-epoxypropoxy)phenyl]fluorene-type epoxy resin can be used alone as a modifier, or a blend of 9,9-bis[(2,3-epoxypropoxy)phenyl]fluorene-type epoxy resin and 9,9-bis(6-glycidyloxy-2-naphthyl]fluorene-type epoxy resin can be used as a modifier.

[0016] Preferably, the epoxy value of the epoxy resin matrix blend is 0.25~0.53 eq / 100g.

[0017] Preferably, the curing agent is an anhydride-based curing agent, and the anhydride-based curing agent is one or more selected from hexahydrophthalic anhydride, methylhexahydrophthalic anhydride, methyltetrahydrophthalic anhydride, tetrahydrophthalic anhydride, nadic anhydride, or methylnadic anhydride. For example, 90 parts of methylhexahydrophthalic anhydride can be used as the curing agent, or a blend of 95 parts of methylhexahydrophthalic anhydride and methyltetrahydrophthalic anhydride can be used as the curing agent.

[0018] Preferably, the accelerator is one or more of tertiary amine accelerators, imidazole accelerators, boron haloamine complexes, and metal carboxylates. For example, the accelerator can be 0.01 parts, 0.03 parts, 0.06 parts, etc.

[0019] This invention also proposes a method for preparing a low conductivity-temperature dependent DC epoxy resin, comprising the following steps: Step 1: Heat and melt-blend the epoxy resin matrix and the fluorene-type resin containing a high-rigidity Cardo structure to obtain an epoxy resin matrix blend. In this step, the temperature can be appropriately increased according to the type and viscosity of the resin to improve the blending uniformity. For example, mechanical stirring can be performed at 120°C to ensure that the two resins are fully mixed. Step 2: Mix the epoxy resin blend, curing agent and accelerator, and then degas at a constant temperature of 80℃ to obtain an epoxy resin composition. Stirring should ensure that the system is homogeneous to avoid curing defects caused by uneven concentration of local components. Ensure that there are no obvious bubbles inside the resin after curing. The degassing time should be adjusted according to the total amount of the composition, the viscosity of the system and the equipment conditions to ensure that there are no obvious residual bubbles in the system, thereby avoiding voids, defects or local electric field distortion inside the cured material. Step 3: Pour the epoxy resin composition obtained in Step 2 into a preheated mold and cure it under gradient temperature conditions; Step 4: After curing, the composition is allowed to cool naturally to room temperature to obtain the cured epoxy resin product.

[0020] Preferably, the melt blending temperature range is 100~160℃; Specifically, under gradient temperature conditions: Multi-stage gradient curing is employed, with gradient temperature conditions ranging from 90 to 200℃. For example, curing at 90℃ for 4 hours followed by curing at 150℃ for 6 hours can be used, or a combination of curing at 90℃ for 2 hours, curing at 130℃ for 2 hours, and curing at 200℃ for 10 hours can be selected.

[0021] This invention also proposes the application of a low conductivity temperature-dependent DC epoxy resin in the preparation of insulating components for high-voltage DC equipment, wherein the epoxy resin composition is applied to the casting molding of epoxy casting equipment or insulating parts or the preparation of prefabricated insulating parts.

[0022] Therefore, the present invention employs the above-mentioned low-conductivity temperature-dependent DC epoxy resin, its preparation method, and its application, with the following beneficial effects: This invention modifies a flexible segmental epoxy resin system by using a fluorene-type epoxy resin with a Cardo structure, which possesses high rigidity, nonpolarity, and high thermal stability. While ensuring the system's processing performance, it effectively controls the molecular chain rigidity, cross-linking network structure, and charge transport characteristics of the cured product, thereby reducing the dependence of the material's DC conductivity on temperature changes. This allows the resulting cured epoxy resin to meet the performance requirements of high-voltage or ultra-high-voltage DC equipment for insulation materials. The introduction of the Cardo rigid structure improves the glass transition temperature, thermal dimensional stability, and high-temperature dielectric properties of the cured system. Simultaneously, its rigid aromatic ring structure and steric hindrance effect help control the segment mobility and free volume structure of the cured network, altering the internal trap distribution and carrier migration behavior. This results in a cured epoxy resin with lower conductivity-temperature dependence and superior high-temperature conductivity stability compared to traditional bisphenol A epoxy / anhydride systems. Consequently, during high-voltage DC operation, the epoxy resin system can reduce conductivity differences caused by temperature gradients, which helps improve the internal electric field distribution of the equipment and reduces the risk of local electric field distortion and charge accumulation.

[0023] Compared to nanoparticle-filled modification methods, this invention primarily achieves control over electrical conductivity and temperature characteristics through molecular structure design and resin compounding modification. It eliminates the need for large-scale introduction of inorganic fillers, reducing problems such as uneven dispersion, agglomeration, increased interfacial defects, significantly increased system viscosity, degassing difficulties, and decreased casting stability associated with inorganic fillers in the resin system. This invention is more conducive to maintaining the casting fluidity, process adaptability, and batch production stability of epoxy systems, making it suitable for the molding and engineering applications of complex insulating components.

[0024] The epoxy resin formulation prepared in this invention possesses excellent electrical insulation, mechanical properties, and heat resistance, making it suitable for the fabrication of high-voltage or ultra-high-voltage DC insulation components. In high-voltage DC equipment, due to conductor heating, ambient temperature changes, and multi-material coupling, significant temperature gradients easily form internally, leading to uneven spatial distribution of conductivity and dynamic electric field migration in the insulation material. The epoxy resin formulation of this invention reduces the sensitivity of DC conductivity to temperature changes, thereby minimizing electric field distortion and localized field concentration. This helps suppress space charge accumulation, partial discharge, and thermo-electric coupling aging, thus improving the reliability and long-term operational stability of high-voltage or ultra-high-voltage DC insulation. Furthermore, the epoxy resin formulation preparation process of this invention has good compatibility with existing epoxy casting processes and can be prepared using conventional processes such as melt blending, vacuum degassing, and gradient curing, demonstrating significant engineering application value.

[0025] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0026] Figure 1 This is a schematic diagram of the process flow of Embodiment 1 of the present invention; Figure 2 This is a graph showing the conductivity-temperature dependence characteristics of embodiments and comparative examples of the present invention. Detailed Implementation

[0027] The technical solution of the present invention will be further described below with reference to the accompanying drawings and embodiments.

[0028] Unless otherwise defined, the technical or scientific terms used in this invention shall have the ordinary meaning as understood by one of ordinary skill in the art to which this invention pertains.

[0029] like Figure 1 As shown, in this invention, all embodiments involve a process of blending an epoxy resin matrix, mixing the resin matrix, curing agent, and accelerator, vacuum degassing, multi-stage gradient curing, and natural cooling for demolding.

[0030] Example 1: A low conductivity temperature-dependent DC epoxy resin, the formulation of which, by mass parts, comprises: 95 parts of bisphenol A type epoxy resin, 5 parts of 9,9-bis[(2,3-epoxypropoxy)phenyl]fluorene type epoxy resin, 90 parts of methylhexahydrophthalic anhydride, and 0.06 parts of accelerator N,N-dimethylbenzylamine.

[0031] Its preparation method is as follows: First, add bisphenol A type epoxy resin and 9,9-bis[(2,3-epoxypropoxy)phenyl]fluorene type epoxy resin into a mixing container, and mechanically stir for 20 minutes under oil bath heating at 140℃ to ensure that the two resins are fully and uniformly mixed to obtain an epoxy resin blend.

[0032] Then, add the appropriate mass fraction of methyl hexahydrophthalic anhydride and accelerator to the epoxy resin blend, and continue stirring for 15 minutes under oil bath heating at 80°C to ensure that the epoxy resin, curing agent and accelerator are uniformly dispersed in the system.

[0033] After thorough mixing, the resulting system is subjected to constant temperature vacuum degassing at 80℃ to remove as many residual bubbles as possible.

[0034] After degassing, the composition was placed in a preheated mold and cured using a gradient heating method. The gradient heating was: 90℃ for 2 hours, 130℃ for 2 hours, and 200℃ for 10 hours. After curing, the mixture was allowed to cool naturally to room temperature to obtain the cured sample.

[0035] Example 2: A low conductivity temperature-dependent DC epoxy resin, the formulation of which, by mass parts, comprises: 90 parts of bisphenol A type epoxy resin, 10 parts of 9,9-bis[(2,3-epoxypropoxy)phenyl]fluorene type epoxy resin, 90 parts of methylhexahydrophthalic anhydride, and 0.03 parts of accelerator N,N-dimethylbenzylamine.

[0036] The preparation method in this embodiment is the same as that in Example 1.

[0037] Example 3: A low conductivity temperature-dependent DC epoxy resin, the formulation of which, by mass parts, comprises: 85 parts of bisphenol A type epoxy resin, 15 parts of 9,9-bis[(2,3-epoxypropoxy)phenyl]fluorene type epoxy resin, 90 parts of methyl hexahydrophthalic anhydride, and 0.06 parts of accelerator N,N-dimethylbenzylamine.

[0038] The preparation method in this embodiment is the same as that in Example 1.

[0039] Example 4: A low conductivity temperature-dependent DC epoxy resin, the formulation of which, by mass parts, comprises: 80 parts of bisphenol A type epoxy resin, 20 parts of 9,9-bis[(2,3-epoxypropoxy)phenyl]fluorene type epoxy resin, 90 parts of methyl hexahydrophthalic anhydride, and 0.03 parts of accelerator N,N-dimethylbenzylamine.

[0040] The preparation process in this embodiment is the same as that in Example 1.

[0041] Comparative example: A conventional bisphenol A type epoxy resin system, the formulation of which, by weight parts, includes: 100 parts of bisphenol A type epoxy resin, 90 parts of methyl hexahydrophthalic anhydride, and 0.06 parts of accelerator N,N-dimethylbenzylamine.

[0042] The preparation process of this comparative example is basically the same as that of Example 1. After the bisphenol A epoxy resin, curing agent and accelerator are mixed evenly, vacuum degassing is performed and curing treatment is carried out. A three-stage curing process is adopted: curing at 90 degrees for 2 hours, then increasing the temperature to 130 degrees for 2 hours, and finally curing at 150 degrees for 10 hours.

[0043] Test The volumetric conductivity of the cured samples obtained in Examples 1-4 and the comparative examples was tested using the three-electrode method. The DC conductivity of the cured samples under different temperature conditions was obtained. During the test, the cured samples were processed to a specified size, and silver-plated electrodes were applied to the surface to improve contact. A constant DC electric field was applied at different temperature points. After the current reached a steady state, the steady-state current value was recorded, and the DC conductivity of the material was calculated using the following formula: Where: σ is the volumetric conductivity, with units of S / m; I This is the steady-state current, measured in amperes (A). d The thickness of the sample is in meters (m). U The applied voltage is measured in volts (V). S The effective area of ​​the electrode is expressed in m². 2 .

[0044] Based on the DC conductivity measured at different temperatures, the Arrhenius relation was used to fit the data: in, σ DC conductivity, in units of S / m; σ 0 is a pre-exponential factor; E a The activation energy is the temperature of conductivity. k Boltzmann's constant; T Temperature is the thermodynamic temperature, measured in Kelvin (K).

[0045] Taking the logarithm of the above expression, we get: by lnσ For 1 / T Plot the graph, perform linear fitting, and calculate the activation energy of the conductivity temperature based on the fitting slope. The results are as follows: Figure 2 As shown, the lower the temperature activation energy of conductivity, the less sensitive the DC conductivity of the material is to temperature changes, which is more beneficial for improving the internal electric field distribution of high-voltage DC dry-type equipment under large temperature gradient conditions.

[0046] The breakdown strength, glass transition temperature and power frequency dielectric constant of the cured samples obtained in Examples 1-4 and the comparative examples were tested.

[0047] Breakdown strength: Tested in transformer oil using ball-to-ball electrodes, in accordance with national standard GB / T 1408.1.

[0048] Glass transition temperature: measured using differential scanning calorimetry.

[0049] Power frequency dielectric constant: obtained by measurement using a broadband dielectric spectrometer, in accordance with national standard GB / T 1410.

[0050] The test results are shown in Table 1.

[0051] From Table 1 and Figure 2As can be seen, the epoxy resin formulation system with low conductivity-temperature dependence can be prepared by the above steps in Examples 1 to 4. The DC conductivity temperature activation energy of the cured epoxy resin is <0.8eV, the glass transition temperature is 135~160℃, the high temperature power frequency dielectric loss at 100℃ is <0.005, and the breakdown strength is >40kV / mm. The glass transition temperature of the material generally increased after the introduction of 9,9-bis[(2,3-epoxypropoxy)phenyl]fluorene epoxy resin, indicating that the high-rigidity Cardo structure helps to improve the heat resistance and chain segment movement restriction ability of the cured system. As the amount of 9,9-bis[(2,3-epoxypropoxy)phenyl]fluorene epoxy resin increased from 5 parts to 20 parts, the sensitivity of the DC conductivity of the material to temperature changes gradually decreased, and the activation energy of conductivity temperature showed a decreasing trend, indicating that this type of modified resin can effectively regulate the internal charge transport mechanism of the material. The materials obtained in each embodiment maintained good electrical insulation properties. In the preferred case, the activation energy of DC conductivity temperature of the cured epoxy resin composition was 0.531 eV, the glass transition temperature was 151℃, the high-temperature power frequency dielectric loss at 100℃ was 0.00313, and the breakdown strength was >40 kV / mm. In high-voltage direct current (HVDC) equipment applications, this epoxy resin formulation, due to its low conductivity temperature dependence, can improve the internal electric field distribution of insulation under large temperature gradient conditions, reducing the risk of localized field strength concentration in critical areas. It not only maintains good conductivity stability under large temperature differences and wide temperature ranges, but also meets the comprehensive requirements of HVDC insulation components for thermal and dielectric properties, thereby improving the long-term operational stability and reliability of the equipment.

[0052] Therefore, this invention employs the aforementioned low-conductivity temperature-dependent DC epoxy resin, its preparation method, and its application to achieve optimized control of the internal electric field distribution of high-voltage DC insulation under wide temperature range and large temperature difference conditions, thereby improving the reliability of equipment operation.

[0053] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the technical solutions of the present invention, and these modifications or equivalent substitutions cannot cause the modified technical solutions to deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. A low- conductivity temperature-dependent DC epoxy resin, characterized by, The following components are included by mass fraction: 100 parts of epoxy resin matrix blend; 40-110 parts of curing agent; Accelerator 0.001~0.1 parts; The epoxy resin matrix blends include: 80-97 parts of flexible segment epoxy resin are used as the matrix; 3-20 parts of Cardo structure fluorene epoxy resin with high rigidity and thermal stability are used as a modifier.

2. The low conductivity temperature-dependent DC epoxy resin according to claim 1, characterized in that: The flexible segment epoxy resin is a general-purpose aromatic epoxy resin or alicyclic epoxy resin with low steric hindrance and no biphenyl structure.

3. The low conductivity temperature-dependent DC epoxy resin according to claim 2, characterized in that: The flexible segment epoxy resin is one or more of the following: bisphenol A type epoxy resin, bisphenol F type epoxy resin, triglycidyl m-aminophenol, resorcinol diglycidyl ether, 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexylcarboxylate, and 4,4-diaminodiphenylmethane tetraglycidylamine.

4. The low conductivity temperature-dependent DC epoxy resin according to claim 1, characterized in that: The fluorene-type epoxy resin containing the highly rigid and thermally stable Cardo structure is selected from one or more of 9,9-bis[4-(2,3-epoxypropoxyethoxy)phenyl]fluorene, 9,9-bis[(2,3-epoxypropoxy)phenyl]fluorene, and 9,9-bis(6-glycidyloxy-2-naphthyl]fluorene.

5. The low conductivity temperature-dependent DC epoxy resin according to claim 1, characterized in that: The epoxy value of the epoxy resin matrix blend is 0.25~0.53 eq / 100g.

6. The low conductivity temperature-dependent DC epoxy resin according to claim 1, characterized in that: The curing agent is an acid anhydride curing agent, which is one or more of hexahydrophthalic anhydride, methylhexahydrophthalic anhydride, methyltetrahydrophthalic anhydride, tetrahydrophthalic anhydride, nadic anhydride, or methylnadic anhydride.

7. The low conductivity temperature-dependent DC epoxy resin according to claim 1, characterized in that: The accelerator is one or more of the following: tertiary amine accelerators, imidazole accelerators, boron halide amine complexes, and metal carboxylates.

8. A method for preparing a low-conductivity temperature-dependent DC epoxy resin as described in any one of claims 1 to 7, characterized in that, Includes the following steps: Step 1: Heat and melt-blend the epoxy resin matrix and the fluorene resin containing the high-rigidity Cardo structure to obtain the epoxy resin matrix blend; Step 2: Mix and stir the epoxy resin blend, curing agent and accelerator, and then degas under constant temperature vacuum to obtain epoxy resin composition; Step 3: Pour the epoxy resin composition obtained in Step 2 into a preheated mold and cure it under gradient temperature conditions. Step 4: After curing, the composition is allowed to cool naturally to room temperature to obtain the cured epoxy resin product.

9. The method for preparing a low-conductivity temperature-dependent DC epoxy resin according to claim 8, characterized in that, The temperature range for melt blending is 100~160℃; Specifically, under gradient temperature conditions: Multi-stage gradient curing is adopted, with gradient temperature conditions ranging from 90 to 200℃.

10. The application of a low conductivity temperature-dependent DC epoxy resin as described in any one of claims 1 to 7 in the preparation of insulating components for high voltage DC equipment.

Images