High-stability corona-resistant anti-corona paint resistant to electric conductivity drift and preparation method thereof

Abstract

The application relates to a high-stability corona-resistant anti-corona paint against electric conductivity drift and a preparation method thereof. The application aims to solve the problems that the existing anti-corona system material has electric conductivity drift, unstable non-linear coefficient, weak anti-corona corrosion capacity, and further influences the service life of a line rod insulation and long-term stable operation of a unit under high voltage grade. The anti-corona paint is prepared from hydrogenated bisphenol A type epoxy resin, a solvent, non-linear fillers, conductive fillers, a curing agent, a silane coupling agent, a defoaming agent and organic montmorillonite. The method comprises the following steps: I. weighing; II. drying; and III. mixing. The application is used for the high-stability corona-resistant anti-corona paint against electric conductivity drift and a preparation method thereof.

Description

Technical Field

[0001] This invention relates to an anti-dizziness paint and its preparation method. Background Technology

[0002] With the deepening of my country's energy structure adjustment and the accelerated implementation of the new power system construction, large generators are continuously developing towards higher voltage and larger capacity, with single-unit capacity and rated voltage levels constantly increasing, placing higher demands on the safety and reliability of generator insulation systems. In large generators, the stator bars are a key component for energy conversion. During long-term operation, they are simultaneously subjected to stresses from multiple factors, including electric fields, temperature, mechanical forces, and environmental factors. The end regions, in particular, are vulnerable to partial discharge (especially corona discharge) due to their complex structure, large potential gradient, and uneven electric field distribution. While traditional anti-corona systems can achieve voltage equalization and suppress end corona to some extent, they suffer from conductivity drift, unstable nonlinear coefficients, and weak resistance to corona corrosion at high voltage levels, thus affecting the insulation life of the bars and the long-term stable operation of the unit. Although anti-corona materials based on silicon carbide possess nonlinear resistance characteristics and a certain degree of anti-corona capability, the problem of overheating and burning at the stator bar ends is becoming increasingly prominent under high voltage conditions, becoming a significant factor restricting further increases in the voltage level and capacity of large generators. Summary of the Invention

[0003] This invention aims to address the problems of conductivity drift, unstable nonlinear coefficients, and weak resistance to corona corrosion in existing anti-corona system materials at high voltage levels, which affect the insulation life of the coil and the long-term stable operation of the unit. Therefore, this invention provides a highly stable corona-resistant anti-corona paint with resistance to conductivity drift and its preparation method.

[0004] A highly stable, anti-corona paint with resistance to electrical conductivity drift is prepared by means of 100 parts by weight of hydrogenated bisphenol A type epoxy resin, 15 to 20 parts by weight of solvent, 90 to 100 parts by weight of nonlinear filler, 3 to 5 parts by weight of conductive filler, 16.5 to 18.5 parts by weight of curing agent, 10 to 12 parts by weight of silane coupling agent, 1 to 2 parts by weight of defoamer and 1 to 11 parts by weight of organo-modified montmorillonite.

[0005] The structural formula of the hydrogenated bisphenol A type epoxy resin is as follows: .

[0006] A method for preparing a highly stable, corona-resistant, and anti-corona paint that resists electrical conductivity drift, comprising the following steps:

[0007] 1. Weigh out 100 parts by weight of hydrogenated bisphenol A type epoxy resin, 15 to 20 parts of solvent, 90 to 100 parts of nonlinear filler, 3 to 5 parts of conductive filler, 16.5 to 18.5 parts of curing agent, 10 to 12 parts of silane coupling agent, 1 to 2 parts of defoamer, and 1 to 11 parts of organo-modified montmorillonite;

[0008] 2. The weighed nonlinear filler, conductive filler and organic montmorillonite are dried to obtain dried nonlinear filler, dried conductive filler and dried organic montmorillonite.

[0009] 3. Under conditions of 60℃~80℃, soften the weighed hydrogenated bisphenol A type epoxy resin for 5min~10min. Under conditions of 60℃~80℃ and a stirring speed of 300r / min~350r / min, add the weighed solvent, silane coupling agent and defoamer to the softened hydrogenated bisphenol A type epoxy resin and stir for 5min~10min. Then, under conditions of 25℃~30℃ and a stirring speed of 300r / min~350r / min, add the dried nonlinear filler, dried conductive filler and dried organic montmorillonite in multiple batches and stir for 45min~60min. Then degas under vacuum. Finally, under conditions of 25℃~30℃ and a stirring speed of 300r / min~350r / min, add the curing agent and stir for 3min~5min to obtain a highly stable anti-corona paint with resistance to electrical conductivity drift.

[0010] The beneficial effects of this invention are:

[0011] After 120 hours of long-term corona aging test, at the upper limit of the test field strength of 1.0 kV / mm, the conductivity of the anti-corona paint with 1 wt% OMMT doping remained stable at 10. -11 S~10 -10 Within the effective operating range of the S-order, the conductivity change rate is only 104.761%. With 2wt% OMMT doping, the conductivity remains at 10. -12 The signal was on the order of S, and no forced shutdown due to surface discharge occurred throughout the entire process, meeting the parameter stability requirements under long-term operating conditions.

[0012] During the 120-hour aging process, the nonlinear coefficient of the 1wt% OMMT sample fluctuated slightly between 1.671 and 3.485; although the 2wt% sample showed a monotonic decay trend (reduced to 1.829 after aging), both remained within the effective nonlinear operating range, retaining the ability to adaptively control the surface electric field and reducing the generation of corona discharge.

[0013] The addition of 1 wt% and 2 wt% OMMT significantly improved the surface morphology retention of the material under long-term corona conditions. Attached Figure Description

[0014] Figure 1 The effects of OMMT doping concentration on the surface conductivity of anti-smudging paint in Examples 1 and 2 and Comparative Experiments 1 and 3 are shown. (a) is Comparative Experiment 1, (b) is Example 1, (c) is Example 2, (d) is Comparative Experiment 2, and (e) is Comparative Experiment 3.

[0015] Figure 2 The effect of OMMT doping concentration on the nonlinear coefficient of anti-halo paint in Examples 1 and 2 and Comparative Experiments 1 and 3;

[0016] Figure 3 Microscopic observations of the effect of corona aging on the surface morphology of the anti-corona paint in Example 1: (a) 0h, (b) 24h, (c) 72h, (d) 120h;

[0017] Figure 4 To show the effect of corona aging on the surface conductivity of anti-corona paint in comparative experiments four and five, (a) comparative experiment five, (b) comparative experiment four;

[0018] Figure 5 The effect of corona aging on the nonlinear coefficient of anti-corona paints in comparative experiments four and five;

[0019] Figure 6 Microscopic images showing the effect of corona aging on the surface morphology of the anti-corona paint of the comparative experiment: (a) 0h, (b) 24h, (c) 72h, (d) 120h.

[0020] Figure 7 Microscopic images showing the effect of corona aging on the surface morphology of the anti-corona paint: (a) 0h, (b) 24h, (c) 72h, (d) 120h.

[0021] Figure 8 This diagram shows the circuit and physical layout of the corona aging test device. Figure a shows the circuit schematic, T1 is the voltage regulator, T2 is the high-voltage test transformer, and R1 and R2 are protective resistors. L For the low-voltage arm resistor, R H denoted as the high-voltage arm resistor, G as the ball gap, C0 as the knife-plate electrode, and b as a photograph of the test electrode and the sample. Detailed Implementation

[0022] The technical solution of the present invention is not limited to the specific embodiments listed below, but also includes any combination of the specific embodiments.

[0023] Specific Implementation Method 1: This implementation method describes a highly stable, anti-corona paint that resists electrical conductivity drift. It is prepared by mass fractions of 100 parts hydrogenated bisphenol A type epoxy resin, 15 to 20 parts solvent, 90 to 100 parts nonlinear filler, 3 to 5 parts conductive filler, 16.5 to 18.5 parts curing agent, 10 to 12 parts silane coupling agent, 1 to 2 parts defoamer, and 1 to 11 parts organo-modified montmorillonite.

[0024] The structural formula of the hydrogenated bisphenol A type epoxy resin is as follows: .

[0025] Principle: Existing anti-corona paints mostly use bisphenol A type epoxy resin, which contains a benzene ring structure. In the strong oxidizing environment of corona discharge (ozone, ultraviolet light), it is extremely prone to chemical degradation and main chain breakage, leading to severe conductivity drift and surface flashover discharge. This specific embodiment uses hydrogenated bisphenol A type epoxy resin without benzene rings as the base. Its fully saturated alicyclic structure (CC and CH bonds) has extremely high chemical inertness to the strong oxidizing environment generated by corona discharge. The aging process changes from destructive chemical degradation to extremely slow physical sputtering, ensuring that it does not experience surface flashover even at field strengths as high as 1.0 kV / mm, significantly improving the anti-corona paint's resistance to corrosion and morphology retention.

[0026] This specific embodiment uses hydrogenated bisphenol A type epoxy resin without benzene ring structure as the base of anti-corona paint. During the corona aging process, it was clearly found that the corona erosion rate on its surface was slower than that of bisphenol A type, and the conductivity drift was significantly suppressed, but it still existed. The present invention adds a specific proportion of organo-modified montmorillonite (OMMT) to the matrix, and the nanosheets are dispersed in the matrix to form a continuous physical barrier network, which effectively prevents the extension of corona erosion into the deep layers of the material and completely suppresses conductivity drift, while enhancing its surface resistance to corona erosion.

[0027] The beneficial effects of this embodiment are:

[0028] After 120 hours of long-term corona aging test, at the upper limit of the test field strength of 1.0 kV / mm, the conductivity of the anti-corona paint with 1 wt% OMMT doping remained stable at 10. -11 S~10 -10 Within the effective operating range of the S-order, the conductivity change rate is only 104.761%. With 2wt% OMMT doping, the conductivity remains at 10. -12 The signal was on the order of S, and no forced shutdown due to surface discharge occurred throughout the entire process, meeting the parameter stability requirements under long-term operating conditions.

[0029] During the 120-hour aging process, the nonlinear coefficient of the 1wt% OMMT sample fluctuated slightly between 1.671 and 3.485; although the 2wt% sample showed a monotonic decay trend (reduced to 1.829 after aging), both remained within the effective nonlinear operating range, retaining the ability to adaptively control the surface electric field and reducing the generation of corona discharge.

[0030] The addition of 1 wt% and 2 wt% OMMT significantly improved the surface morphology retention of the material under long-term corona conditions.

[0031] Specific Implementation Method Two: This implementation method differs from Specific Implementation Method One in that the solvent is one or a combination of N,N-dimethylformamide, toluene, and ethanol. Everything else is the same as in Specific Implementation Method One.

[0032] Specific Implementation Method Three: This implementation method differs from Specific Implementation Method One or Two in that the nonlinear filler is one or a combination of silicon carbide, zinc oxide, and titanium dioxide; the particle size of the nonlinear filler is 20μm~25μm. Everything else is the same as in Specific Implementation Method One or Two.

[0033] Specific Implementation Method Four: This implementation method differs from Specific Implementation Methods One to Three in that the conductive filler is one or a combination of graphite, graphene oxide, and carbon nanotubes; and the particle size of the conductive filler is 13μm to 15μm. Everything else is the same as in Specific Implementation Methods One to Three.

[0034] Specific Embodiment Five: This embodiment differs from Specific Embodiments One to Four in that the curing agent is one or a combination of several of the following: 1,3-bis(aminomethyl)cyclohexane, m-phenylenediamine, 4,4'-diaminodiphenylmethane, and 4,4'-diaminodiphenyl sulfone. Everything else is the same as in Specific Embodiments One to Four.

[0035] Specific Implementation Method Six: This implementation method differs from Specific Implementation Methods One to Five in that the silane coupling agent is one or a combination of KH550, KH560, and KH570. Everything else is the same as in Specific Implementation Methods One to Five.

[0036] Specific Implementation Method Seven: This implementation method differs from Specific Implementation Methods One to Six in that the defoamer is one or a combination of several of BYK-066N, BYK-088, Airex 900, and Airex 920. Everything else is the same as in Specific Implementation Methods One to Six.

[0037] Specific Embodiment Eight: This embodiment differs from Specific Embodiments One to Seven in that: the organomodified montmorillonite is one or a mixture of alkyl quaternary ammonium salt modified montmorillonite, aminated modified montmorillonite, polyetheramine modified montmorillonite, and hydroxylated modified montmorillonite; the particle size of the organomodified montmorillonite is 2nm~3nm. Everything else is the same as in Specific Embodiments One to Seven.

[0038] Specific Implementation Method Nine: This implementation method provides a method for preparing a highly stable, corona-resistant, and anti-corona paint that resists electrical conductivity drift. It is carried out according to the following steps:

[0039] 1. Weigh out 100 parts by weight of hydrogenated bisphenol A type epoxy resin, 15 to 20 parts of solvent, 90 to 100 parts of nonlinear filler, 3 to 5 parts of conductive filler, 16.5 to 18.5 parts of curing agent, 10 to 12 parts of silane coupling agent, 1 to 2 parts of defoamer, and 1 to 11 parts of organo-modified montmorillonite;

[0040] 2. The weighed nonlinear filler, conductive filler and organic montmorillonite are dried to obtain dried nonlinear filler, dried conductive filler and dried organic montmorillonite.

[0041] 3. Under conditions of 60℃~80℃, soften the weighed hydrogenated bisphenol A type epoxy resin for 5min~10min. Under conditions of 60℃~80℃ and a stirring speed of 300r / min~350r / min, add the weighed solvent, silane coupling agent and defoamer to the softened hydrogenated bisphenol A type epoxy resin and stir for 5min~10min. Then, under conditions of 25℃~30℃ and a stirring speed of 300r / min~350r / min, add the dried nonlinear filler, dried conductive filler and dried organic montmorillonite in multiple batches and stir for 45min~60min. Then degas under vacuum. Finally, under conditions of 25℃~30℃ and a stirring speed of 300r / min~350r / min, add the curing agent and stir for 3min~5min to obtain a highly stable anti-corona paint with resistance to electrical conductivity drift.

[0042] Specific Implementation Method Ten: This implementation method differs from Specific Implementation Method Nine in that: the drying described in step two is specifically carried out at a temperature of 80℃~100℃ for 12h~24h; the vacuum degassing described in step three is specifically carried out under a vacuum pressure of -0.095MPa~-0.01MPa for 10min~15min. Everything else is the same as in Specific Implementation Method Nine.

[0043] The beneficial effects of the present invention are verified using the following embodiments:

[0044] Example 1:

[0045] A highly stable, anti-corona paint with resistance to electrical conductivity drift is prepared by means of 100 parts by weight of hydrogenated bisphenol A type epoxy resin, 15 parts by weight of solvent, 100 parts by weight of nonlinear filler, 5 parts by weight of conductive filler, 16.5 parts by weight of curing agent, 10 parts by weight of silane coupling agent, 2 parts by weight of defoamer and 2.5 parts by weight of organo-modified montmorillonite (OMMT).

[0046] The structural formula of the hydrogenated bisphenol A type epoxy resin is as follows: The CAS number is 30583-72-3.

[0047] The solvent is N,N-dimethylformamide.

[0048] The nonlinear filler is silicon carbide; the particle size of the nonlinear filler is 20μm~25μm.

[0049] The conductive filler is graphite; the particle size of the conductive filler is 13μm~15μm.

[0050] The curing agent is 1,3-bis(aminomethyl)cyclohexane.

[0051] The silane coupling agent is KH550.

[0052] The defoamer mentioned is BYK-066N.

[0053] The organomodified montmorillonite is alkyl quaternary ammonium salt modified montmorillonite; the D50 particle size of the organomodified montmorillonite is 2.6 nm.

[0054] The preparation method of the above-mentioned highly stable anti-corona paint with anti-conductivity drift is carried out according to the following steps:

[0055] 1. Weigh out 100 parts by weight of hydrogenated bisphenol A type epoxy resin, 15 parts of solvent, 100 parts of nonlinear filler, 5 parts of conductive filler, 16.5 parts of curing agent, 10 parts of silane coupling agent, 2 parts of defoamer and 2.5 parts of organo-modified montmorillonite;

[0056] 2. Under the condition of 80℃, the weighed nonlinear filler, conductive filler and organo-modified montmorillonite were dried for 24 hours to obtain the dried nonlinear filler, the dried conductive filler and the dried organo-modified montmorillonite.

[0057] 3. At a temperature of 60℃, the weighed hydrogenated bisphenol A epoxy resin is softened for 5 minutes. At a temperature of 60℃ and a stirring speed of 300 r / min, the weighed solvent, silane coupling agent, and defoamer are added to the softened hydrogenated bisphenol A epoxy resin and stirred for 5 minutes. Then, at a temperature of 30℃ and a stirring speed of 300 r / min, the dried nonlinear filler, the dried conductive filler, and the dried organo-montmorillonite are added in 5 portions and stirred for 30 minutes. Then, the mixture is vacuum degassed for 10 minutes at -0.095 MPa. Finally, at a temperature of 30℃ and a stirring speed of 300 r / min, the curing agent is added and stirred for 3 minutes to obtain a highly stable anti-corona paint with resistance to electrical conductivity drift.

[0058] Example 2: This example differs from Example 1 in that the amount of organo-modified montmorillonite is 5.1 parts. Everything else is the same as in Example 1.

[0059] Comparative Experiment 1: The difference between this example and Example 1 is that the proportion of organo-modified montmorillonite is 1.3 parts. Everything else is the same as in Example 1.

[0060] Comparative Experiment 2: The difference between this example and Example 1 is that the proportion of organo-modified montmorillonite is 7.7 parts. Everything else is the same as in Example 1.

[0061] Comparative Experiment 3: The difference between this example and Example 1 is that the proportion of organo-modified montmorillonite is 10.4 parts. Everything else is the same as in Example 1.

[0062] Comparative Experiment 4: This example differs from Example 1 in that the addition of organo-modified montmorillonite is omitted. Everything else is the same as in Example 1.

[0063] Comparative Experiment 5: This comparative experiment differs from Example 1 in that the addition of organo-modified montmorillonite is omitted, and hydrogenated bisphenol A epoxy resin is replaced with bisphenol A epoxy resin; the CAS number of the bisphenol A epoxy resin is 1675-54-3. Everything else is the same as in Example 1.

[0064] The hydrogenated bisphenol A epoxy resin in Example 1 is named D0H4; the bisphenol A epoxy resin in Comparative Experiment 5 is named D4H0; the mass percentages of OMMT in the total (hydrogenated bisphenol A epoxy resin, solvent, nonlinear filler, conductive filler, curing agent, silane coupling agent, defoamer, and organo-modified montmorillonite) in Examples 1-2 and Comparative Experiments 1-3 are 1%, 2%, 0.5%, 3%, and 4%, respectively, i.e., the doping concentrations of OMMT are 1%, 2%, 0.5%, 3%, and 4%, respectively. Therefore, the anti-splatter paints prepared in Examples 1-2 and Comparative Experiments 1-3 are named P0H4 with an OMMT content of 1 wt%. OMMT POH4 with an OMMT content of 2wt%OMMT 0.5wt% OMMT content of P0H4 OMMT POH4 with OMMT content of 3wt% OMMT POH4 with 4wt% OMMT content OMMT The anti-dizziness paint prepared in the fourth comparative experiment was named P0H4; the anti-dizziness paint prepared in the fifth comparative experiment was named P4H0.

[0065] The anti-splatter paint prepared in the examples and comparative experiments was uniformly applied to the surface of a mica board (80mm × 135mm), and finally placed in an oven at 80℃ for 3 hours for curing. The cured samples were then subjected to the following tests:

[0066] The electrical conductivity of anti-scintillation materials can usually be expressed as:

[0067] ;

[0068] In the formula, σ0 is the intrinsic conductivity at room temperature and zero field (unit: S), β is the nonlinear coefficient (describing the sensitivity of conductivity to field strength), and θ is the temperature coefficient of conductivity (unit: ℃). -1 (Describes the sensitivity of electrical conductivity to temperature).

[0069] Corona aging: Based on the IEEE Std 1799-2012 standard, a 15-channel parallel blade-plate electrode corona aging test system was designed and built. Its circuit principle and physical components are as follows: Figure 8 As shown; Figure 8 This diagram shows the circuit and physical layout of the corona aging test device. Figure a shows the circuit schematic, T1 is the voltage regulator, T2 is the high-voltage test transformer, and R1 and R2 are protective resistors. L For the low-voltage arm resistor, R H G represents the high-voltage arm resistance, C0 represents the spherical gap, and b represents the blade-plate electrode. The device is equipped with 15 independent blade electrodes, supporting simultaneous corona aging tests on 15 samples. To avoid mutual interference between adjacent discharge units, the electrode spacing is designed to be no less than 50 mm. The test employs a gap discharge mode, with high-voltage excitation provided by an AC high-voltage test transformer, generating corona discharge through the blade-plate electrode system. The high-voltage electrodes are copper blade-shaped, and the vertical distance between each blade electrode and the sample surface is set to 2 mm and is precisely adjustable.

[0070] Figure 1 The effects of OMMT doping concentration on the surface conductivity of anti-smudging paint in Examples 1 and 2 and Comparative Experiments 1 and 3 are shown. (a) is Comparative Experiment 1, (b) is Example 1, (c) is Example 2, (d) is Comparative Experiment 2, and (e) is Comparative Experiment 3. Figure 2 The effect of OMMT doping concentration on the nonlinear coefficient of anti-halo paint in Examples 1 and 2 and Comparative Experiments 1 and 3;

[0071] As can be seen from the figure, Figure 1 (a) and Figure 2 As shown, the OMMT content of P0H4 is 0.5 wt%. OMMT The conductivity curve of the sample after 0 hours of aging extends completely to the upper limit of the test field strength (1.0 kV / mm), and the initial conductivity at 1.0 kV / mm is approximately 7.67 × 10⁻⁶. -11 S. However, after 24 hours of corona aging, the conductivity curve at 0.5 kV / mm (the conductivity had increased to 1.07 × 10⁻⁶) showed a decrease. -9 S) Due to premature triggering of surface discharge, the field strength was forced to stop, preventing further pressure application to the upper limit. As aging time increased, the cutoff field strength gradually shifted later (to 0.6 kV / mm at 48h, 0.7 kV / mm at 72h, 0.8 kV / mm at 96h, and 0.9 kV / mm at 120h), but the conductivity at each stage increased significantly compared to the initial value. Simultaneously, the nonlinear coefficient surged from 3.444 before aging to 7.973 at 24h and 8.752 at 48h. Although it subsequently decreased, it remained as high as 5.103 at 120h, with a total fluctuation of 5.308. These phenomena indicate that a doping concentration of 0.5 wt% is insufficient to form an effective continuous physical barrier network for the OMMT nanosheets in the matrix. Under continuous corona erosion, local defects rapidly accumulate, leading to rapid deterioration of the surface insulation performance.

[0072] like Figure 1 (b) and Figure 2 As shown, P0H4 with an OMMT content of 1 wt% OMMT The conductivity curves of the sample from 0h to 120h all extended smoothly to 1.0kV / mm, without any forced cutoff due to surface discharge triggering. At 1.0kV / mm, the conductivity values ​​at each aging stage were as follows: 1.43×10 at 0h. -10 S, 24h time 1.33×10 -10 S, 48h time 1.77×10 -11 S, 72h time 4.67×10 -11 S, 96h time 1.07×10 -10 S, 120h 7.0×10 -11 S, the value of which remains at 10 throughout all stages. -11 ~10 - 10 The conductivity change rate was only 104.761%, the lowest among all doping concentrations, indicating that the material maintained highly stable conductivity characteristics during a 120-hour corona aging process. The OMMT content was 1 wt% P0H4. OMMTThe nonlinear coefficients of the samples throughout the aging process were 3.485, 2.259, 1.671, 2.797, 2.327, and 2.596, with a maximum deviation of approximately 1.814. Although there were some fluctuations, the coefficients remained within the effective nonlinear operating range, indicating that the anti-corona material's adaptive field-averaging ability to the surface electric field was consistently preserved. When the OMMT content was 1 wt%, the OMMT sheets were uniformly dispersed in the matrix, and the physical barrier formed was sufficient to effectively suppress the corona erosion of the epoxy matrix without significantly interfering with the conductive pathways between SiC particles. A good balance was achieved between conductivity and nonlinear stability.

[0073] like Figure 1 (c) and Figure 2 As shown, P0H4 with an OMMT content of 2wt% OMMT The aging curves of the sample at each stage can also be fully extended to the upper limit of the electric field. At 1.0 kV / mm, the conductivity at each stage is 2.3 × 10⁻⁶. -11 S(0h), 9.33×10 -12 S(24h), 2.57×10 -11 S(48h), 3.33×10 -12 S(72h), 1.8×10 -12 S(96h) and 4.67×10 -12 In S(120h), the conductivity did not show excessive dispersion at each aging stage, demonstrating high conductivity stability. Regarding the nonlinear coefficient, the value gradually decreased from 2.760 before aging to 1.829 at 120h. Although the coefficient fluctuated somewhat, it remained within the effective nonlinear range, meeting the requirements for homogenizing the surface electric field. This indicates that as the OMMT doping concentration increased to 2wt%, the interference effect of the OMMT layers on the conductive pathways between SiC particles became apparent, and the nonlinear characteristics of the material began to weaken.

[0074] like Figure 1 (d), 1(e) and Figure 2 As shown, P0H4 OMMT The OMMT content in the samples was 3 wt% and 4 wt%. When doped at 3 wt%, the initial conductivity at 1.0 kV / mm was only 2.17 × 10⁻⁶. -12 S, although it rose to 1.3×10 at one point during 24 hours. -10 S, but then dropped rapidly, falling to 4.67×10 at 120h. -13 The conductivity response exhibits significant step shifts between different aging stages; the nonlinear coefficient oscillates wildly between 0.564 and 3.477, showing poor stability. With 4wt% doping, the initial conductivity at 1.0 kV / mm is only about 1.5 × 10⁻⁶. -13The conductivity S is far below the lower limit of conductivity required for the effective operation of the anti-corona layer, and the initial nonlinear coefficient is only 0.421, which continues to decrease to a minimum value of 0.124 as aging progresses, indicating that the nonlinear conductivity characteristics are basically lost. High-concentration OMMT sheets are extensively interspersed between SiC particles, physically blocking the carrier migration path while simultaneously reducing the overall conductivity of the material to a level where even field control is impossible. The anti-corona layer completely loses its ability to adaptively control the surface electric field, and no longer meets the basic functional requirements of anti-corona materials.

[0075] The above analysis shows that as the doping concentration of OMMT increases, the fluctuation trends of conductivity and nonlinear coefficient during long-term corona aging generally converge, and the stability of corona aging resistance gradually improves. However, at the same time, the overall conductivity of the material also decreases rapidly with increasing doping concentration. When the doping concentration reaches 3% or higher, the conductivity drops below the effective working range of the anti-corona material, and the material loses its function of uniformly controlling the electric field along the end face. Considering the evaluation of conductivity adaptability, conductivity and nonlinear coefficient stability, a 1% OMMT doping concentration achieves the optimal overall balance: its conductivity remains consistently around 10. -11 ~10 -10 Within the effective working range of the S-level, the conductivity change rate is the lowest (104.761%), and the nonlinear coefficient fluctuates little throughout the 120-hour aging process and remains within the effective range. This is the optimal modification concentration to meet the functional and long-term stability requirements of anti-sunshine materials.

[0076] Figure 3Microscopic observations of the effect of corona aging on the surface morphology of the anti-corona paint in Example 1 are shown in (a) 0h, (b) 24h, (c) 72h, and (d) 120h. The surface morphology changes of the samples at different corona aging times were observed using a PLM microscope. As shown in the figures, in the original state, the sample surface was very smooth and flat, with excellent physical continuity. The SiC filler was uniformly dispersed and tightly wrapped by the epoxy resin matrix, with no obvious defects. After 24h of corona aging, compared to the original state, the epoxy resin around some SiC particles began to show slight erosion and decomposition, exhibiting localized yellowing. This is because SiC has high thermal conductivity, and the localized temperature rise generated during corona aging preferentially conducts to the surface of the SiC particles, causing the tightly wrapped epoxy resin to undergo thermo-oxidative degradation first. After 72h of corona aging, the exposed area of ​​the SiC particles significantly increased, and the yellowing of the epoxy surface further intensified, indicating that the erosion range of the matrix continued to expand. After 120 hours of corona aging, the surface epoxy resin underwent large-scale decomposition or carbonization, indicating a significant degree of aging. However, it is noteworthy that the matrix epoxy resin and the SiC particles it encapsulates did not show any peeling. The interfacial bonding between the filler and the matrix remained intact, and the nonlinear conductive pathway remained complete. This indicates that the physical barrier effect of the 1% OMMT sheet effectively prevented the corona erosion from extending into the deeper layers of the material, thus confirming the excellent electrical conductivity stability of the material at this doping concentration from a microstructural perspective.

[0077] Figure 4 To illustrate the effect of corona aging on the surface conductivity of anti-corona paints in comparative experiments four and five, (a) comparative experiment five and (b) comparative experiment four are shown. As can be seen from the figures, both P4H0 and P0H4 maintain nonlinear conductivity characteristics at each aging stage, but their conductivity evolution patterns differ significantly. With increasing corona aging time, the conductivity curve of P4H0 shows a clear overall upward trend, indicating that under the same test electric field strength, the longer the aging time, the higher the surface conductivity of the material. At an electric field strength of 0.6 kV / mm, the conductivity increases from 2.062 × 10⁻⁶ kV / mm. -11 S rose to 9.048×10 -9 The conductivity of P0H4 increased by two orders of magnitude. When the electric field strength exceeded 0.65 kV / mm, the conductivity curves for each aging stage were interrupted, indicating that surface flashover discharge had occurred in the sample, and the surface insulation performance of the material was severely damaged. The conductivity of P0H4 also increased with increasing field strength; at an electric field strength of 0.6 kV / mm, the conductivity increased from 2.6667 × 10⁻⁶ to 2.6667 × 10⁻⁶. -12 S rises to 1.500×10 -11 S increased by an order of magnitude; compared with OMMT content of 1wt% and 2wt% P0H4 OMMTCompared to the other samples, both P0H4 and P4H0 showed significant conductivity drift throughout the aging cycle, with P4H0 even exhibiting surface discharge, indicating that the conductivity of P0H4 and P4H0 is not stable during the aging process.

[0078] Figure 5 The effect of corona aging on the nonlinear coefficients of anti-corona paints in comparative experiments four and five is shown in the figure. As can be seen from the figure, before aging begins, the nonlinear coefficient of P4H0 is slightly larger than that of P0H4. With the increase of corona aging time, the nonlinear coefficients of both materials show a trend of first increasing and then decreasing. The change in the nonlinear coefficient of P4H0 is 3.404, and the change in the nonlinear coefficient of P0H4 is 2.101. This is compared with P0H4 containing 1wt% and 2wt% OMMT. OMMT Compared to the samples, P4H0 and P0H4 exhibit excessive fluctuations in nonlinear coefficients during the aging process, which can cause electric field distortion. This distortion can promote corona discharge, and long-term corona discharge can threaten the safe operation of the unit.

[0079] The above analysis shows that, during long-term corona aging, the conductivity stability and corona resistance of hydrogenated bisphenol A type epoxy resin-based anti-corona varnish (POH4) are significantly better than those of bisphenol A type anti-corona varnish (P4H0). However, under long-term corona aging conditions, the parameters of P4H0 and P0H4 are unstable and cannot meet the requirements for long-term safe and stable operation of the unit. Compared with P4H0 and P0H4, P0H4 with OMMT content of 1wt% and 2wt% is more suitable. OMMT The sample exhibited significant electrical conductivity stability and corona resistance throughout the entire aging cycle.

[0080] Figure 6 The images show the effects of corona aging on the surface morphology of the anti-corona paint. (a) is 0h, (b) is 24h, (c) is 72h, and (d) is 120h. The surface morphology changes of the samples at different aging times were observed using a PLM microscope. As can be seen from the figures, the P4H0 sample exhibits a typical accelerated oxidative degradation and physical ablation process of polymer under a strong corona field. After 24 hours of aging, the synergistic effect of high-energy particle bombardment and ozone oxidation caused the surface epoxy matrix to be eroded first, and the outline of inorganic filler was faintly revealed. The corrosion was still limited to the shallow surface. After 72 hours of aging, the matrix resin suffered large-scale loss and ablation, and dense holes and pits appeared on the surface. The inorganic filler was exposed over a large area, and the integrity of the conductive path was severely damaged. After 120 hours of aging, the anti-halo paint surface was covered with deep grooves, microcracks and holes. The epoxy matrix was almost completely peeled off or carbonized. This directly explains the phenomenon that the conductivity curves of the P4H0 sample at 96 hours and 120 hours were forced to stop due to surface discharge triggering at medium field strengths of 0.5 kV / mm to 0.6 kV / mm.

[0081] Figure 7Microscopic images showing the effect of corona aging on the surface morphology of the P0H4 anti-corona paint are shown. (a) is 0 h, (b) is 24 h, (c) is 72 h, and (d) is 120 h. The surface morphology changes of the samples at different aging times were observed using a PLM microscope. As shown in the figures, compared with P4H0, P0H4 exhibits significantly superior corrosion resistance and morphology retention. The original sample surface is smooth and dense, with the epoxy group perfectly coating the inorganic filler without obvious defects. After 24 hours of aging, only very slight changes in surface texture were observed, the matrix continuity was well maintained, and no filler was exposed. After 72 hours of aging, slight etching marks and fine graininess began to appear on the surface, and the outlines of some shallow fillers became faintly visible, but the deep pits and large-scale matrix loss observed in P4H0 at the same stage were never seen. After 120 hours of aging, although the surface roughness increased and a small amount of shallow peeling and micro-irritation appeared, the macroscopic framework and structural density of the anti-splatter coating were maintained, confirming that P0H4 could still withstand a high field strength of 1.0 kV / mm without surface discharge after 120 hours of aging. This is in contrast to P0H4 with OMMT contents of 1 wt% and 2 wt%. OMMT Compared to the samples, P4H0 and P0H4 showed significant morphological changes, with obvious yellowing, carbonization, and even peeling. Under long-term aging conditions, P0H4 with OMMT content of 1wt% and 2wt% showed better morphological changes than P4H0 and P0H4. OMMT The sample has a high ability to retain its surface morphology.

[0082] As can be seen from the above, the significant difference in corona erosion behavior between P0H4 and P4H0 stems from the fundamental difference in their matrix molecular structures. In the bisphenol A matrix, the π-electron cloud of the benzene ring is highly susceptible to ozone electrophilic attack and catalytic degradation by high-energy ultraviolet radiation, leading to severe chain breakage and oxidative decomposition of the polymer backbone, generating volatile small molecules that escape, thus leaving behind numerous voids and pits on a macroscopic scale. In contrast, the fully saturated alicyclic structure (CC and CH bonds) in the hydrogenated bisphenol A matrix exhibits extremely high chemical inertness to the strong oxidizing environment generated by corona discharge. Its aging process is mainly characterized by physical sputtering of high-energy particles, with a very slow chemical degradation rate, resulting in significantly less morphological damage. The matrix structures of P0H4 and P4H0 are directly exposed to air and the corona environment, making them highly susceptible to damage from ionized substances, high-energy rays, and particle bombardment generated by the corona. P0H4 with OMMT contents of 1wt% and 2wt% is particularly susceptible to these effects. OMMT Because of the introduction of the OMMT layer structure, it can significantly block corona damage and resist damage to the matrix material by high-energy ions, high-energy rays and ionized substances, showing remarkable resistance to corona damage.

[0083] Based on the test results of three indicators—conductivity stability, nonlinear coefficient, and surface morphology—P4H0 exhibited the greatest conductivity drift, drastic fluctuations in the nonlinear coefficient, and severe surface morphology degradation during long-term aging. Compared to P4H0, P0H4 showed a significant improvement in conductivity drift, although some drift still existed, with substantial nonlinear fluctuations. However, P0H4 demonstrated a significantly improved ability to maintain surface morphology, with surface yellowing occurring only in the final stage of aging. P0H4 with 1wt% and 2wt% OMMT content showed similar performance. OMMT Conductivity drift was completely suppressed, nonlinear coefficient fluctuations were minimized, the ability to satisfy a nonlinear uniform electric field was achieved, surface morphology was best maintained, and no yellowing occurred throughout the entire aging cycle. This indicates that OMMT has a significant ability to regulate the conductivity stability, nonlinear coefficient stability, and surface morphology maintenance of anti-corona materials.

Claims

1. A highly stable, corona-resistant, and anti-corona paint that resists electrical conductivity drift, characterized in that... It is prepared by mass fractions of 100 parts hydrogenated bisphenol A type epoxy resin, 15 to 20 parts solvent, 90 to 100 parts nonlinear filler, 3 to 5 parts conductive filler, 16.5 to 18.5 parts curing agent, 10 to 12 parts silane coupling agent, 1 to 2 parts defoamer and 1 to 11 parts organo-modified montmorillonite; The structural formula of the hydrogenated bisphenol A type epoxy resin is as follows: .

2. The high-stability, corona-resistant, and anti-corona paint with anti-conductivity drift as described in claim 1, characterized in that... The solvent is one or a combination of N,N-dimethylformamide, toluene, and ethanol.

3. The high-stability, corona-resistant, and anti-corona paint with anti-conductivity drift as described in claim 1, characterized in that... The nonlinear filler is one or a combination of silicon carbide, zinc oxide and titanium dioxide; the particle size of the nonlinear filler is 20μm~25μm.

4. The high-stability, corona-resistant, and anti-corona paint with anti-conductivity drift as described in claim 1, characterized in that... The conductive filler is one or a combination of graphite, graphene oxide and carbon nanotubes; the particle size of the conductive filler is 13μm~15μm.

5. The high-stability, corona-resistant, and anti-corona paint with anti-conductivity drift as described in claim 1, characterized in that... The curing agent is one or a combination of several of the following: 1,3-bis(aminomethyl)cyclohexane, m-phenylenediamine, 4,4'-diaminodiphenylmethane, and 4,4'-diaminodiphenyl sulfone.

6. The high-stability, corona-resistant, and anti-corona paint with anti-conductivity drift as described in claim 1, characterized in that... The silane coupling agent is one or a combination of several of KH550, KH560 and KH570.

7. The high-stability, corona-resistant, and anti-corona paint with anti-conductivity drift as described in claim 1, characterized in that... The defoamer is one or a combination of several of BYK-066N, BYK-088, Airex 900 and Airex 920.

8. The high-stability, corona-resistant, and anti-corona paint with anti-conductivity drift as described in claim 1, characterized in that... The organomodified montmorillonite is one or a mixture of alkyl quaternary ammonium salt modified montmorillonite, aminated modified montmorillonite, polyetheramine modified montmorillonite, and hydroxylated modified montmorillonite; the particle size of the organomodified montmorillonite is 2nm~3nm.

9. The preparation method of a highly stable, anti-corona paint with anti-conductivity drift as described in claim 1, characterized in that... It is done in the following steps:

1. Weigh out 100 parts by weight of hydrogenated bisphenol A type epoxy resin, 15 to 20 parts of solvent, 90 to 100 parts of nonlinear filler, 3 to 5 parts of conductive filler, 16.5 to 18.5 parts of curing agent, 10 to 12 parts of silane coupling agent, 1 to 2 parts of defoamer, and 1 to 11 parts of organo-modified montmorillonite; 2. The weighed nonlinear filler, conductive filler and organic montmorillonite are dried to obtain dried nonlinear filler, dried conductive filler and dried organic montmorillonite.

3. Under conditions of 60℃~80℃, soften the weighed hydrogenated bisphenol A type epoxy resin for 5min~10min. Under conditions of 60℃~80℃ and a stirring speed of 300r / min~350r / min, add the weighed solvent, silane coupling agent and defoamer to the softened hydrogenated bisphenol A type epoxy resin and stir for 5min~10min. Then, under conditions of 25℃~30℃ and a stirring speed of 300r / min~350r / min, add the dried nonlinear filler, dried conductive filler and dried organic montmorillonite in multiple batches and stir for 45min~60min. Then degas under vacuum. Finally, under conditions of 25℃~30℃ and a stirring speed of 300r / min~350r / min, add the curing agent and stir for 3min~5min to obtain a highly stable anti-corona paint with resistance to electrical conductivity drift.

10. The method for preparing a highly stable, corona-resistant, and anti-corona paint with anti-conductivity drift according to claim 9, characterized in that... The drying described in step two is specifically carried out at a temperature of 80℃~100℃ for 12h~24h; the vacuum degassing described in step three is specifically carried out at a pressure of -0.095MPa~-0.01MPa for 10min~15min.

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