Low-temperature adaptive MOF modified epoxy resin insulating material and preparation method and application thereof

Abstract

The application discloses a low-temperature adaptive MOF modified epoxy resin insulating material and a preparation method and application thereof, and belongs to the technical field of superconducting power equipment and advanced high-voltage solid insulation materials, wherein the MOF modified epoxy resin insulating material comprises an epoxy resin matrix, a curing agent, an accelerator and a MOF dopant; the MOF dopant comprises ZIF-8, ZIF-8-Cl, ZIF-65 or ZIF-90; the particle size of the MOF dopant is 30 nm; and the mass of the MOF dopant is 0.1% to 0.7% of the total mass of the epoxy resin matrix, the curing agent and the accelerator. The application adopts the above low-temperature adaptive MOF modified epoxy resin insulating material and the preparation method thereof, constructs a deep electric charge trap and a sacrificial bond protection dual mechanism through MOF doping, and realizes efficient carrier migration inhibition, anti-breakdown performance improvement and dielectric loss reduction of the epoxy resin insulating material under low-temperature working conditions in combination with molecular-level compatibility design.

Description

Technical Field

[0001] This invention relates to the field of superconducting power equipment and advanced high-voltage solid insulating materials, and in particular to a low-temperature adaptable MOF (metal-organic framework) modified epoxy resin insulating material, its preparation method, and its application. Background Technology

[0002] Superconducting power equipment is the core of advanced scientific devices and large-capacity power transmission and distribution systems. Its components, such as superconducting magnet coils, need to operate in extremely low-temperature environments such as liquid nitrogen or even liquid helium for extended periods. Once a "superconductor failure" occurs, it will generate high transient induced voltages and thermal stress, placing stringent requirements on the insulation system. Epoxy resin has become the mainstream material for insulation in superconducting equipment due to its excellent mechanical, processing, and insulation properties, but its insulation strength determines the electrical performance and service life of the equipment.

[0003] Current research on epoxy resin insulation largely focuses on room temperature conditions. However, at extremely low temperatures, the internal carrier transport and dipole polarization relaxation characteristics undergo fundamental changes, rendering room temperature optimization schemes ineffective and potentially leading to insulation degradation. In traditional modification techniques, inorganic nanoparticle doping easily leads to particle aggregation due to polarity differences, causing electric field distortion and reduced breakdown strength. While organic small molecule doping improves compatibility, it results in fewer charge trapping sites and shallower trap energy levels, easily forming carrier migration channels and increasing conductivity. Neither approach can solve the technical challenge of cryogenic insulation for superconducting equipment. Therefore, there is an urgent need to develop an epoxy resin insulation material that is suitable for cryogenic conditions, has excellent compatibility, and can efficiently suppress carrier migration. Summary of the Invention

[0004] The purpose of this invention is to provide a low-temperature adaptable MOF modified epoxy resin insulating material, its preparation method, and its application, so as to solve the problems existing in the prior art.

[0005] To achieve the above objectives, the present invention provides a low-temperature adaptable MOF-modified epoxy resin insulating material, comprising an epoxy resin matrix, a curing agent, an accelerator, and a metal-organic framework (MOF) dopant; the MOF dopant includes zeolite imidazole ester framework material-8 (ZIF-8), chlorozeolite imidazole ester framework material-8 (ZIF-8-Cl), zeolite imidazole ester framework material-65 (ZIF-65), or zeolite imidazole ester framework material-90 (ZIF-90), the particle size of the MOF dopant is 30 nm, and the mass of the MOF dopant is 0.1%-0.7% of the total mass of the epoxy resin matrix, curing agent, and accelerator.

[0006] Preferably, the mass ratio of epoxy resin matrix, curing agent, and accelerator is 100:82:0.25.

[0007] Preferably, the epoxy resin matrix is ​​bisphenol F type epoxy resin.

[0008] Preferably, the curing agent is an anhydride-based curing agent, including methyltetrahydrophthalic anhydride.

[0009] Preferably, the accelerator is type DY073-1 accelerator.

[0010] This invention also provides a method for preparing a low-temperature adaptable MOF-modified epoxy resin insulating material, comprising the following steps: S1. Preheat, mix, stir, ultrasonically disperse, and degas the epoxy resin matrix, curing agent, accelerator, and metal-organic framework dopant to obtain a mixture. S2. Crosslink and cure the mixture. After the crosslinking and curing is completed, cool it down to 25°C in the oven and demold to obtain a low-temperature adaptable metal-organic framework modified epoxy resin insulation material.

[0011] Preferably, in step S1, the preheating temperature is 80-90℃, the preheating time is 20-40 min, the stirring speed is 400-600 rpm, and the stirring time is 20-40 min. Preheating can significantly reduce the viscosity of each polymer component system, facilitating subsequent nanoscale dispersion and mixing.

[0012] Preferably, the ultrasonic dispersion power is 200-400W, the ultrasonic dispersion time is 10-30min, the degassing pressure is -0.09MPa, and the degassing time is 60min. Ultrasonic dispersion enables highly uniform molecular-level dispersion of 30nm MOF dopants in the resin system, completely avoiding the aggregation of nanoparticles; vacuum degassing can completely remove microbubbles entrained during stirring and ultrasonication, preventing physical porosity defects that induce partial discharge inside the insulator after curing.

[0013] Preferably, in S2, the cross-linking curing temperature is 130-140℃ and the cross-linking curing time is 25-30h.

[0014] The present invention also provides an application of a low-temperature adaptable MOF modified epoxy resin insulating material, wherein the above-mentioned low-temperature adaptable MOF modified epoxy resin insulating material is used in the insulating structural components of superconducting power equipment.

[0015] Therefore, the present invention, employing the aforementioned low-temperature adaptable MOF modified epoxy resin insulating material, its preparation method, and its application, has the following beneficial effects: (1) On the one hand, the present invention utilizes the high electron affinity of the central metal site of MOF dopant to construct a deep charge trap of 1.51-2.15eV in the system, which effectively captures high-energy carriers and significantly reduces the DC conductivity of the material at room temperature and liquid nitrogen temperature, thereby suppressing the degradation caused by carrier migration from the root. On the other hand, ZIF-90 / ZIF-65 with aldehyde / nitro groups is preferred. Its unsaturated functional groups undergo sacrificial bond breaking first under strong electric field, forming a protective layer for the epoxy resin matrix, increasing the AC breakdown field strength of the material at room temperature and under liquid nitrogen conditions, and significantly enhancing its resistance to electrical aging and breakdown.

[0016] (2) The three-dimensional organic ligand network of the MOF material of the present invention achieves molecular-level compatibility with the organic macromolecules of epoxy resin. Combined with the precise process of magnetic stirring and ultrasonic dispersion, the aggregation phenomenon of traditional inorganic nanoparticles is completely avoided, eliminating the micron-level electric field distortion and partial discharge initiation point caused by aggregation, and ensuring the stability of the macroscopic insulation performance of the material.

[0017] (3) Although the MOF doping at room temperature will slightly increase the dielectric loss due to the increase of polarization units, the thermal motion of dipoles inside the material is suppressed and the polarization relaxation process is frozen in the extremely low temperature environment of liquid nitrogen, resulting in a significant decrease in dielectric loss. The combination of the carrier fixation effect of deep traps and the extremely low dielectric loss enables the material to exhibit insulation stability and ultra-long service life far exceeding the room temperature design in the liquid nitrogen temperature range.

[0018] (4) The present invention determines a fixed mass ratio of epoxy resin matrix, curing agent and accelerator 100:82:0.25, and optimizes the MOF doping amount according to the application conditions: 0.3wt% is optimal for room temperature conditions to balance the contradiction between the introduction of deep traps and the increase of dielectric loss; 0.5wt% is optimal for liquid nitrogen and lower cryogenic conditions to enhance charge trapping ability by utilizing the characteristics of cryogenic freezing polarization, so as to achieve the optimal performance solution at different temperatures.

[0019] (5) This invention achieves molecular-level uniform dispersion of MOF dopants through a series of standardized processes such as preheating to reduce viscosity, vacuum degassing, and cross-linking curing at 135℃ for 28 hours. It completely removes air bubbles inside the material and ensures that epoxy resin and curing agent complete three-dimensional cross-linking curing. The resulting product has high density, stable performance and good repeatability, and is suitable for industrial production applications.

[0020] (6) The material of the present invention is specifically used for core insulation structural components of superconducting power equipment. It can meet the usage requirements of various components such as interlayer insulation of superconducting magnet coils, insulation of superconducting transformer windings, and insulation components for extreme environments of tokamak devices. It effectively solves the problems of high-voltage insulation protection and anti-electric aging in the long-term operation of low-temperature superconducting equipment, and promotes the development process of superconducting engineering.

[0021] 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

[0022] Figure 1 The conductivity is that of the MOF-modified epoxy resin insulating materials (Examples 1-4 and Comparative Examples 1-13) with different particle sizes and contents according to the present invention. Figure 2 It is the breakdown field strength of the MOF-modified epoxy resin insulating materials with different contents of the present invention (Examples 1-16 and Comparative Example 1); Figure 3 These are molecular orbital characteristic diagrams of the modified epoxy resin insulating materials of Examples 3, 7, 11, 15 and Comparative Example 1 of the present invention; Figure 4 These are FTIR images of the MOF-modified epoxy resin insulating materials before and after electro-aging in Examples 11 and 15 of this invention. Detailed Implementation

[0023] The technical solution of the present invention will be further described below with reference to the accompanying drawings and embodiments.

[0024] 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.

[0025] In this invention, bisphenol F epoxy resin (DGEBF), also known as bisphenol F diglycidyl ether, was purchased from Huntsman Corporation as GY282; methyltetrahydrophthalic anhydride (MTHPA) was purchased from Huntsman Corporation as HY918; DY073-1 accelerator was purchased from Huntsman Corporation; and metal-organic framework (MOF) materials ZIF-8, ZIF-8-Cl, ZIF-65, and ZIF-90 were purchased from Jiangsu Xianfeng Nanomaterials Technology Co., Ltd., all with a purity ≥99%.

[0026] Example 1 A low-temperature adaptable MOF modified epoxy resin insulating material includes an epoxy resin matrix, a curing agent, an accelerator, and a metal-organic framework dopant. The mass ratio of the epoxy resin matrix, curing agent, and accelerator is 100:82:0.25. The metal-organic framework dopant is ZIF-8, and the mass of ZIF-8 is 0.1% of the total mass of the epoxy resin matrix, curing agent, and accelerator.

[0027] The preparation method of the above-mentioned low-temperature adaptable MOF modified epoxy resin insulating material includes the following steps: S1. Take 50g of bisphenol F type epoxy resin (epoxy resin matrix), 41g of methyltetrahydrophthalic anhydride (curing agent), 0.125g of DY073-1 type accelerator, and 0.091g of ZIF-8 (metal-organic framework dopant) with a particle size of 30nm. Place them separately in an 85℃ constant temperature oven for 30min to significantly reduce the viscosity of each polymer component system. Then mix them and place them on the table of a closed constant temperature magnetic stirrer. Stir at 500rpm for 30min. Then, immerse the container in the water bath of an industrial-grade ultrasonic cell disruptor and disperse it with a high-frequency micro-jet at a constant power of 300W for 20min. Utilize the ultrasonic cavitation effect to ensure that the 30nm MOF dopant particles are highly uniformly dispersed at the molecular level in the resin system, completely avoiding the aggregation of nanoparticles. Then transfer it to a vacuum drying oven at 85℃, evacuate to -0.09MPa, and degas for 1h until no bubbles overflow, to obtain a mixture. S2. Preheat a steel mold with dimensions of 100mm×10mm×2mm (compliant with ASTM D638 standard) in an oven at 85℃ for 1 hour. Slowly inject the mixture into the preheated mold, and then place the mold stably into a constant temperature oven set at 135℃. Maintain constant temperature heating for 28 hours. Under the action of the accelerator, the epoxy resin matrix and the curing agent fully complete the ring-opening crosslinking reaction to form a dense three-dimensional polymer insulation network structure. After the crosslinking and curing is completed, allow it to cool naturally to 25℃ in the oven. Gently tap the mold to demold, and you will obtain a low-temperature adaptable MOF modified epoxy resin insulation material.

[0028] Example 2 A low-temperature adaptable MOF modified epoxy resin insulating material includes an epoxy resin matrix, a curing agent, an accelerator, and a metal-organic framework dopant. The mass ratio of the epoxy resin matrix, curing agent, and accelerator is 100:82:0.25. The metal-organic framework dopant is ZIF-8, and the mass of ZIF-8 is 0.3% of the total mass of the epoxy resin matrix, curing agent, and accelerator.

[0029] The preparation method of the above-mentioned low-temperature adaptable MOF modified epoxy resin insulating material is the same as that in Example 1, except that: in S1, the amount of ZIF-8 (metal-organic framework dopant) added is 0.273g, the stirring speed is 400rpm, the stirring time is 40min, the ultrasonic dispersion power is 400W, and the ultrasonic dispersion time is 10min.

[0030] Example 3 A low-temperature adaptable MOF modified epoxy resin insulating material includes an epoxy resin matrix, a curing agent, an accelerator, and a metal-organic framework dopant. The mass ratio of the epoxy resin matrix, curing agent, and accelerator is 100:82:0.25. The metal-organic framework dopant is ZIF-8, and the mass of ZIF-8 is 0.5% of the total mass of the epoxy resin matrix, curing agent, and accelerator.

[0031] The preparation method of the above-mentioned low-temperature adaptable MOF modified epoxy resin insulating material is the same as that in Example 1, except that: in S1, the amount of ZIF-8 (metal-organic framework dopant) added is 0.456g, the stirring speed is 600rpm, the stirring time is 20min, the ultrasonic dispersion power is 200W, and the ultrasonic dispersion time is 30min; in S2, the crosslinking curing temperature is 140℃, and the crosslinking curing time is 25h.

[0032] Example 4 A low-temperature adaptable MOF modified epoxy resin insulating material includes an epoxy resin matrix, a curing agent, an accelerator, and a metal-organic framework dopant. The mass ratio of the epoxy resin matrix, curing agent, and accelerator is 100:82:0.25. The metal-organic framework dopant is ZIF-8, and the mass of ZIF-8 is 0.7% of the total mass of the epoxy resin matrix, curing agent, and accelerator.

[0033] The preparation method of the above-mentioned low-temperature adaptable MOF modified epoxy resin insulating material is the same as that in Example 1, except that: in S1, the amount of ZIF-8 (metal-organic framework dopant) added is 0.638g; in S2, the crosslinking curing temperature is 130℃ and the crosslinking curing time is 30h.

[0034] Example 5 This embodiment is the same as Embodiment 1, except that the metal-organic framework dopant is ZIF-8-Cl, that is, ZIF-8 is not added in S1, but ZIF-8-Cl is added.

[0035] Example 6 This embodiment is the same as Embodiment 2, except that the metal-organic framework dopant is ZIF-8-Cl, that is, ZIF-8 is not added in S1, but ZIF-8-Cl is added.

[0036] Example 7 This embodiment is the same as embodiment 3, except that the metal-organic framework dopant is ZIF-8-Cl, that is, ZIF-8 is not added in S1, but ZIF-8-Cl is added.

[0037] Example 8 This embodiment is the same as embodiment 4, except that the metal-organic framework dopant is ZIF-8-Cl, that is, ZIF-8 is not added in S1, but ZIF-8-Cl is added.

[0038] Example 9 This embodiment is the same as Embodiment 1, except that the metal-organic framework dopant is ZIF-65, that is, ZIF-8 is not added in S1, but ZIF-65 is added.

[0039] Example 10 This embodiment is the same as embodiment 2, except that the metal-organic framework dopant is ZIF-65, that is, ZIF-8 is not added in S1, but ZIF-65 is added.

[0040] Example 11 This embodiment is the same as embodiment 3, except that the metal-organic framework dopant is ZIF-65, that is, ZIF-8 is not added in S1, but ZIF-65 is added.

[0041] Example 12 This embodiment is the same as embodiment 4, except that the metal-organic framework dopant is ZIF-65, that is, ZIF-8 is not added in S1, but ZIF-65 is added.

[0042] Example 13 This embodiment is the same as Embodiment 1, except that the metal-organic framework dopant is ZIF-90, that is, ZIF-8 is not added in S1, but ZIF-90 is added.

[0043] Example 14 This embodiment is the same as embodiment 2, except that the metal-organic framework dopant is ZIF-90, that is, ZIF-8 is not added in S1, but ZIF-90 is added.

[0044] Example 15 This embodiment is the same as embodiment 3, except that the metal-organic framework dopant is ZIF-90, that is, ZIF-8 is not added in S1, but ZIF-90 is added.

[0045] Example 16 This embodiment is the same as embodiment 4, except that the metal-organic framework dopant is ZIF-90, that is, ZIF-8 is not added in S1, but ZIF-90 is added.

[0046] Comparative Example 1 This comparative example is the same as Example 1, except that the low-temperature adaptable MOF modified epoxy resin insulating material does not include metal-organic framework dopants, that is, ZIF-8 is not added in S1.

[0047] Comparative Example 2 This comparative example is the same as Example 1, except that the particle size of ZIF-8 is 150 nm.

[0048] Comparative Example 3 This comparative example is the same as Example 2, except that the particle size of ZIF-8 is 150 nm.

[0049] Comparative Example 4 This comparative example is the same as Example 3, except that the particle size of ZIF-8 is 150 nm.

[0050] Comparative Example 5 This comparative example is the same as Example 4, except that the particle size of ZIF-8 is 150 nm.

[0051] Comparative Example 6 This comparative example is the same as Example 1, except that the particle size of ZIF-8 is 400 nm.

[0052] Comparative Example 7 This comparative example is the same as Example 2, except that the particle size of ZIF-8 is 400 nm.

[0053] Comparative Example 8 This comparative example is the same as Example 3, except that the particle size of ZIF-8 is 400 nm.

[0054] Comparative Example 9 This comparative example is the same as Example 4, except that the particle size of ZIF-8 is 400 nm.

[0055] Comparative Example 10 This comparative example is the same as Example 1, except that the particle size of ZIF-8 is 1000 nm.

[0056] Comparative Example 11 This comparative example is the same as Example 2, except that the particle size of ZIF-8 is 1000nm.

[0057] Comparative Example 12 This comparative example is the same as Example 3, except that the particle size of ZIF-8 is 1000nm.

[0058] Comparative Example 13 This comparative example is the same as Example 4, except that the particle size of ZIF-8 is 1000nm.

[0059] The conductivity of the modified epoxy resin insulating materials of Examples 1-4 and Comparative Examples 1-13 was tested using a three-electrode method in room temperature (25℃) and liquid nitrogen (-196℃) environments. The electric field strength was 50 kV / mm, and the test duration was 30 min. The results are as follows: Figure 1 As shown, where Figure 1 In the figure, (a) represents the electrical conductivity of modified epoxy resin insulation materials with different ZIF-8 contents at room temperature. Figure 1 (b) represents the conductivity of modified epoxy resin insulation materials with different ZIF-8 contents in a liquid nitrogen environment.

[0060] from Figure 1 As can be seen, regardless of room temperature or liquid nitrogen temperature, doping with smaller ZIF-8 particles can reduce the conductivity of epoxy resin to some extent, while doping with larger ZIF-8 particles significantly increases the conductivity. With increasing ZIF-8 particle size, the conductivity of modified epoxy resin insulation materials with the same doping content shows a monotonically increasing trend; furthermore, with increasing doping content, the effect of particle size increase on conductivity improvement is more significant. In Example 2, after doping with ZIF-8 (particle size of 30 nm, ZIF-8 mass of 0.3% of the total mass of epoxy resin matrix, curing agent, and accelerator), the room temperature conductivity of the modified epoxy resin insulation material decreased to 22.7% of that of pure epoxy resin; however, when using particle sizes of 150 nm and above, the dispersion of nanoparticles in the matrix deteriorates sharply, the effective interface area between the dopant and the matrix decreases significantly, the physical region for capturing charges is lost, and large particles cause severe electric field distortion. The doping of 1000nm large-particle-size ZIF-8, whether at room temperature or under liquid nitrogen, leads to a significant increase in the conductivity of the modified epoxy resin insulation material, completely eliminating its insulating and protective function.

[0061] The breakdown field strength of the modified epoxy resin insulating materials of Examples 1-16 and Comparative Example 1 was tested in a 50Hz AC electric field using a ball-plate electrode in environments of room temperature (25℃) and liquid nitrogen (-196℃). The breakdown field strength test was repeated at least fifteen times. The test data were statistically analyzed using Weibull probability distribution. The results are as follows: Figure 2 As shown, where Figure 2 In the figure, (a) represents the breakdown field strength of MOF-modified epoxy resin insulation materials with different contents in a room temperature environment. Figure 2 (b) represents the breakdown field strength of MOF-modified epoxy resin insulation materials with different contents in a liquid nitrogen environment.

[0062] from Figure 2As can be seen, the breakdown field strength of the epoxy resin insulation materials modified by the four MOF materials exhibits a trend of first increasing and then decreasing under room temperature and liquid nitrogen conditions, indicating the existence of an optimal doping amount: 0.3% at room temperature and 0.5% in liquid nitrogen. The higher optimal doping amount in liquid nitrogen can be attributed to the freezing of molecular thermal motion and the weakening of the interfacial polarization relaxation process at extremely low temperatures, thus allowing for the introduction of more MOF dopants without causing excessive polarization loss. Among the four MOF materials, ZIF-8, ZIF-8-Cl, and ZIF-65 show similar effects in improving the breakdown field strength, indicating that the contributions of the three functional groups—methyl (-CH3), chlorine (-Cl), and nitro (-NO2)—to the breakdown performance are roughly equal, mainly playing a role through the charge trapping mechanism of the central metal node. In contrast, ZIF-90 shows a significantly better improvement in the breakdown field strength than the other three, performing best under both room temperature and liquid nitrogen conditions. This is attributed to the additional sacrificial bond-breaking protection mechanism brought by its aldehyde (-CHO) unsaturated functional group. The breakdown field strength of the four MOF materials at their respective optimal doping contents is higher than that of pure epoxy resin, which confirms that MOF doping can effectively improve the AC breakdown field strength of epoxy resin, with ZIF-90 being the optimal choice.

[0063] Quantum chemical calculations were used to analyze the molecular orbital properties of the modified epoxy resin insulating materials from Examples 3, 7, 11, 15, and Comparative Example 1 to evaluate the ability of different MOF materials to construct deep charge traps within the epoxy resin matrix. The results are as follows: Figure 3 As shown, where Figure 3 (a) in the diagram shows the molecular orbital distribution and energy level diagram of the cross-linked structure of epoxy resin and curing agent in Comparative Example 1. Figure 3 (b) in the figure is a diagram showing the LUMO, HOMO orbitals and energy levels of the epoxy crosslinking products and MOF materials of Examples 3, 7, 11 and 15.

[0064] from Figure 3As can be seen, the LUMO energy level of the epoxy resin-curing agent crosslinking product is -1.96 eV, and the molecular orbitals near the LUMO orbital are mainly distributed in the MTHPA (methyltetrahydrophthalic anhydride, curing agent) region; the HOMO energy level is -5.71 eV, and the molecular orbitals near the HOMO orbital are mainly distributed in the DGEBF (bisphenol F type epoxy resin, epoxy resin matrix) region. Compared with the epoxy resin-curing agent crosslinking product, the LUMO and HOMO energy levels of the four MOF materials are lower than those of the epoxy crosslinking product, and their electron affinity is as high as about 12 eV, with a band gap of only 0.51 to 0.74 eV, which is much narrower than that of epoxy resin. Based on the above molecular orbital parameters, it can be calculated that the charge trap depth that the four MOF materials can provide inside the epoxy resin matrix ranges from 1.51 to 1.62 eV, among which ZIF-65 has the highest electron affinity and therefore has a deeper charge trapping capability. Figure 3 The quantum chemical perspective reveals the charge trapping mechanism of MOF-doped modified epoxy resin: MOF materials, with their extremely high electron affinity and extremely narrow band gap, can form a strong Coulomb force on electrons in the epoxy resin matrix, thereby effectively capturing high-energy charge carriers and suppressing their long-distance migration, providing a theoretical basis for improving the insulation performance of the material.

[0065] Molecular energy level simulation results characterized the charge trapping properties constructed by MOFs within epoxy resin samples. Overall, samples with deeper traps exhibited lower DC conductivity. Under liquid nitrogen cryogenic conditions, ZIF-65 showed the best suppression ability for carrier migration; at room temperature, ZIF-8-Cl showed the best suppression effect on carrier migration. This phenomenon can be attributed to the higher polarizability and longer relaxation time of ZIF-65, and the more active polarization relaxation behavior of its dipoles at room temperature, resulting in a partial polarization current component in the current.

[0066] Despite ZIF-65's deeper charge traps and higher electron affinity, its improvement on epoxy resin breakdown performance at room temperature did not show a significant advantage. This is because ZIF-65 has a higher dielectric loss than other MOF materials, which significantly exacerbates the internal temperature rise of the epoxy resin under an alternating electric field, increasing the impact of hot electrons on the insulating matrix and thus prematurely causing insulation material degradation and breakdown failure. Considering the beneficial effects of ZIF-65's deep charge traps and the adverse effects of its high dielectric loss, its improvement on epoxy resin insulation performance at room temperature is similar to that of ZIF-8 and ZIF-8-Cl. In the cryogenic environment of liquid nitrogen, the molecular motion of ZIF-8-Cl and ZIF-65 is frozen, significantly reducing dielectric loss, and their breakdown field strength shows a certain advantage compared to ZIF-8.

[0067] ZIF-90 has significant research value. While its charge trap depth is shallower than other MOF materials, its effect on reducing system conductivity is weaker than that of ZIF-65 and ZIF-8-Cl. However, ZIF-90's inhibitory effect on epoxy resin breakdown is far superior to other MOFs. This phenomenon is mainly attributed to the unique unsaturated functional group—aldehyde—in its molecular structure. Under a strong electric field, the unsaturated bonds in -CHO are preferentially attacked and destroyed by high-energy electrons, preventing epoxy resin matrix breakdown through sacrificial protection, thereby effectively increasing the breakdown field strength of the epoxy resin.

[0068] The ZIF-90 modified epoxy resin insulating material (denoted as EP90) from Example 15 and the ZIF-65 modified epoxy resin insulating material (denoted as EP65) from Example 11 were subjected to electro-aging: pure epoxy resin (EP), EP90, and EP65 were placed between ball-plate electrodes, and an AC high voltage with a frequency of 50Hz and an electric field strength of 10kV / mm was applied at 25°C for 1000 hours to simulate the electro-aging and deterioration process of insulating materials under long-term AC strong electric field. The aged EP, EP90, and EP65 were designated as EPA, EP90A, and EP65A, respectively. The chemical structures of EP, EPA, EP90, EP90A, EP65, and EP65A were characterized by Fourier transform infrared spectroscopy (FTIR), and the results are as follows: Figure 4 As shown, where Figure 4 (a) in the figure is the FTIR plot of EP, EP90, and EP90A. Figure 4 (b) in the figure is the FTIR plot of EPA, EP65, and EP65A.

[0069] from Figure 4 As can be seen in (a), compared with pure epoxy resin, the addition of ZIF-90 can achieve a viscosity of 1690 cm⁻¹. -1 The aldehyde group -CHO was observed at 1170 cm⁻¹. -1 Characteristic peaks of the imidazole ring were observed nearby. After electro-aging, both the -CHO and imidazole ring characteristic peaks decreased. This indicates that the -CHO and imidazole rings underwent chain scission under a high electric field. Simultaneously, the -OH peak in the 3200-3400 MHz wideband showed a slight increase, indicating that -CHO was gradually converted to -CH2OH. This confirms that these unsaturated functional groups can protect the epoxy resin to some extent.

[0070] from Figure 4 As can be seen from (b) in the figure, at 1350cm -1 A characteristic peak of -NO2 appeared nearby, at 1600 cm⁻¹. -1Characteristic peaks of the imidazole ring appeared nearby. After electro-aging, both the -NO2 and imidazole ring characteristic peaks decreased. This indicates that the unsaturated bonds introduced by ZIF-65 can also play a role in bond breaking and protecting the epoxy group. Combined structural analysis of EP90A and EP65A suggests that ZIF-90 has a better effect on improving the insulation performance of epoxy resin, mainly due to its lower dielectric loss.

[0071] Therefore, this invention employs the aforementioned low-temperature adaptable MOF-modified epoxy resin insulating material, its preparation method, and its application. By constructing a dual mechanism of deep charge trapping and sacrificial bond breaking protection through MOF doping, combined with molecular-level compatibility design, it achieves efficient carrier migration suppression, improved breakdown performance, and reduced dielectric loss of epoxy resin insulating material under low-temperature conditions. It completely solves the problems of aggregation and electric field distortion in traditional nano-doping, adapts to multiple temperature conditions, and has stable finished product performance. It provides key insulation protection for low-temperature superconducting equipment and effectively overcomes the technical challenges of ultra-low temperature insulation failure and insufficient resistance to electrical aging in superconducting power equipment.

[0072] 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-temperature adaptable MOF-modified epoxy resin insulating material, characterized in that: It includes epoxy resin matrix, curing agent, accelerator and metal-organic framework dopant; Metal-organic framework dopants include zeolite imidazole ester framework material-8, chloro-zeolite imidazole ester framework material-8, zeolite imidazole ester framework material-65 or zeolite imidazole ester framework material-90. The particle size of the metal-organic framework dopant is 30 nm; the mass of the metal-organic framework dopant is 0.1%-0.7% of the total mass of the epoxy resin matrix, curing agent and accelerator.

2. The low-temperature adaptable MOF modified epoxy resin insulating material according to claim 1, characterized in that: The mass ratio of epoxy resin matrix, curing agent, and accelerator is 100:82:0.

25.

3. The low-temperature adaptable MOF modified epoxy resin insulating material according to claim 1, characterized in that: The epoxy resin matrix is ​​bisphenol F type epoxy resin.

4. The low-temperature adaptable MOF modified epoxy resin insulating material according to claim 1, characterized in that: The curing agent is an anhydride-based curing agent, including methyltetrahydrophthalic anhydride.

5. The low-temperature adaptable MOF modified epoxy resin insulating material according to claim 1, characterized in that: The accelerator is type DY073-1.

6. A method for preparing a low-temperature adaptable MOF-modified epoxy resin insulating material as described in any one of claims 1-5, characterized in that: Includes the following steps: S1. Preheat, mix, stir, ultrasonically disperse, and degas the epoxy resin matrix, curing agent, accelerator, and metal-organic framework dopant to obtain a mixture. S2. Crosslink and cure the mixture. After the crosslinking and curing is completed, cool it down to 25°C in the oven and demold to obtain a low-temperature adaptable metal-organic framework modified epoxy resin insulation material.

7. The method for preparing a low-temperature adaptable MOF modified epoxy resin insulating material according to claim 6, characterized in that: In S1, the preheating temperature is 80-90℃, the preheating time is 20-40 minutes, the stirring speed is 400-600 rpm, and the stirring time is 20-40 minutes.

8. The method for preparing a low-temperature adaptable MOF-modified epoxy resin insulating material according to claim 6, characterized in that: In S1, the ultrasonic dispersion power is 200-400W, the ultrasonic dispersion time is 10-30min, the degassing pressure is -0.09MPa, and the degassing time is 60min.

9. The method for preparing a low-temperature adaptable MOF-modified epoxy resin insulating material according to claim 6, characterized in that: In S2, the cross-linking curing temperature is 130-140℃, and the cross-linking curing time is 25-30h.

10. An application of a low-temperature adaptable MOF-modified epoxy resin insulating material, characterized in that: The low-temperature adaptable MOF modified epoxy resin insulating material according to any one of claims 1-5 is used in the insulating structural components of superconducting power equipment.

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