Mechanical stress resistant mof modified epoxy resin insulating material, its preparation method and application

Abstract

The application discloses an anti-mechanical stress MOF modified epoxy resin insulating material and a preparation method and application thereof, and belongs to the technical field of modern power equipment and advanced polymer composite insulating materials, and comprises an epoxy resin matrix, a curing agent, an accelerator and an amino-containing metal organic framework doped reinforcing agent, the mass ratio of the epoxy resin matrix, the curing agent and the accelerator is 100:82:0.25, and the mass of the amino-containing metal organic framework doped reinforcing agent accounts for 0.1%-0.7% of the total mass of the epoxy resin matrix, the curing agent and the accelerator. The application realizes the synergistic improvement of crosslinking density, mechanical toughness and insulating strength by constructing a metal organic framework-epoxy-curing agent ternary crosslinking system, combining the molecular-level elastic extension energy storage mechanism of the metal organic framework and the charge capture function of the central metal node, and provides an insulating base material guarantee for large-scale power equipment which can bear the synergistic action of multiple physical fields for a long time.

Description

Technical Field

[0001] This invention relates to the field of modern power equipment and advanced polymer composite insulation materials, and in particular to a mechanical stress-resistant MOF (metal-organic framework) modified epoxy resin insulation material, its preparation method, and its application. Background Technology

[0002] Electromagnetic coils are core components of power equipment such as transformers, reactors, and superconducting magnets. Their insulation systems must withstand the combined effects of strong electric fields and huge mechanical stresses (such as short-circuit electromagnetic forces and thermal expansion and contraction stress), posing extremely demanding challenges to the macroscopic comprehensive performance of insulation materials.

[0003] Epoxy resin is the preferred insulating substrate for the aforementioned equipment due to its excellent insulation properties and processability. However, after curing, epoxy resin forms a highly cross-linked, rigid three-dimensional network, which is brittle, has poor impact resistance, and low fracture toughness. When subjected to mechanical stress or long-term fatigue, microcracks are easily generated within it. Under a strong electric field, these microcracks can induce electric field distortion and partial discharge, ultimately leading to insulation breakdown and equipment damage.

[0004] To overcome the brittleness of epoxy resins, existing technologies are mainly divided into two categories: The first type is physical toughening, which involves doping the resin with a flexible second-phase material (such as rubber or inorganic nanoparticles). However, this method has two major problems: first, nanoparticles are prone to agglomeration, forming micron-sized aggregates that cause electric field distortion and partial discharge; second, the physical interface bonding is weak, and under stress, it is easy to debond and form air gaps, which reduces the insulation strength.

[0005] The second type is chemical toughening, which improves ductility by introducing flexible molecular chain segments or reducing crosslinking density. However, reducing crosslinking density increases the free volume inside the material, facilitating the migration of high-energy charge carriers, thereby sacrificing dielectric strength and breakdown performance.

[0006] Therefore, existing technologies struggle to overcome the paradox that toughening inevitably reduces insulation. How to simultaneously improve mechanical toughness and insulation breakdown field strength without reducing or even increasing the degree of crosslinking is a pressing technical challenge in this field. Summary of the Invention

[0007] The purpose of this invention is to provide a mechanically stress-resistant MOF modified epoxy resin insulating material, its preparation method, and its application, in order to break the paradox that toughening inevitably reduces insulation.

[0008] To achieve the above objectives, the present invention provides a mechanical stress-resistant MOF-modified epoxy resin insulating material, comprising an epoxy resin matrix, a curing agent, an accelerator, and an amino-containing MOF-doped reinforcing agent. The mass ratio of the epoxy resin matrix, curing agent, and accelerator is 100:82:0.25, and the mass of the amino-containing MOF-doped reinforcing agent is 0.1%-0.7% of the total mass of the epoxy resin matrix, curing agent, and accelerator.

[0009] Preferably, the amino-containing MOF doping enhancer includes UiO-66(Zr)-NH2, MIL-53(Al)-NH2 or MIL-101(Cr)-NH2, with a particle size of 100 nm.

[0010] Preferably, the epoxy resin matrix is ​​bisphenol F type epoxy resin.

[0011] Preferably, the curing agent is an anhydride-based curing agent, including methyltetrahydrophthalic anhydride.

[0012] Preferably, the accelerator is type DY073-1 accelerator.

[0013] This invention also provides a method for preparing a mechanically stress-resistant MOF-modified epoxy resin insulating material, comprising the following steps: S1. Vacuum dry the epoxy resin matrix, curing agent, accelerator, and amino MOF doped reinforcing agent, mix, stir, ultrasonically disperse, and degas to obtain a mixture; S2. The mixture is cured at high temperature, cooled to 25°C, and demolded to obtain a mechanical stress-resistant MOF modified epoxy resin insulation material.

[0014] Preferably, in S1, the stirring speed is 400-600 rpm, the stirring time is 20-40 min, the ultrasonic dispersion power is 200-400 W, the ultrasonic dispersion time is 10-30 min, the degassing pressure is -0.095 MPa, and the degassing time is 60 min.

[0015] Preferably, in S2, the high-temperature curing includes two stages: pre-gelling and high-temperature post-curing. The pre-gelling temperature is 80-100℃ and the pre-gelling time is 1.5-2.5h. The high-temperature post-curing temperature is 130-140℃ and the high-temperature post-curing time is 9-11h.

[0016] Preferably, in S2, the cooling rate is 0.5-1.5℃ / min.

[0017] This invention also provides an application of a mechanical stress-resistant MOF-modified epoxy resin insulating material, which is used in the insulating structural components of power equipment that are subjected to the combined effects of strong electric fields, large mechanical stresses, and alternating temperature thermal stresses over long periods of time.

[0018] This invention employs surface-covalently modified MOF materials containing amino groups (-NH2) to modify epoxy resin. During the polymer curing stage, the amino groups on the MOF surface act as strong nucleophiles, actively attacking and participating in the amine ring-opening curing reaction of the epoxy resin matrix, generating stable, high-bond-energy CN covalent crosslinks. This weaves the originally independent nanoparticles into the backbone network of the epoxy resin, constructing a fully crosslinked ternary system of "MOF-epoxy-curing agent" with no dead corners in its physical structure. Furthermore, this invention utilizes the molecular-level elastic extensibility endowed by the unique porous structure of the MOF material itself. The fully covalently anchored three-dimensional structure allows externally applied mechanical stress to be effectively transferred to the flexible MOF framework with a large internal space through strong chemical bonds, forcing the MOF itself to undergo reversible lattice deformation, thereby absorbing, sharing, and dissipating stress damage energy, forming a physical energy storage spring mechanism. Simultaneously, the central metal nodes of the MOF possess high electron affinity, which can capture and restrict the avalanche migration of high-energy electrons within the material, thereby increasing the breakdown field strength.

[0019] Therefore, the present invention employs the above-mentioned mechanical stress-resistant MOF modified epoxy resin insulating material and its preparation method, which has the following beneficial effects: (1) The epoxy resin of the present invention is an insulating material modified by MOF. The MOF is a material containing amino (-NH2) covalently modified on the surface. The amino group on its surface acts as a strong nucleophile and participates in the amine ring-opening curing reaction of the epoxy resin matrix to generate stable CN covalent crosslinking bonds with high bond energy, thus constructing a ternary fully crosslinked system of "MOF-epoxy-curing agent". Compared with unmodified ordinary MOF (which will cause steric hindrance, reduce the degree of crosslinking and leave micropores), amino-containing MOF provides abundant reaction crosslinking sites, so that the degree of crosslinking of the entire insulation system is stabilized at 100%.

[0020] (2) The mechanical toughness of the MOF-modified epoxy resin insulation material of the present invention is significantly improved. The amino-containing MOF is firmly anchored in the epoxy matrix through covalent bonds, which can effectively inhibit the initiation of microcracks and dendritic propagation under stress. At the same time, relying on the molecular-level elastic extension energy storage mechanism brought about by the porous structure of MOF itself, it can efficiently absorb, share and dissipate mechanical stress energy, significantly improve the fracture strength, fracture elongation and tensile fracture toughness of the material. It still maintains excellent mechanical stability after 30MPa high mechanical stress and 20,000 high-frequency mechanical fatigue cycles, fundamentally improving the problems of high brittleness and poor impact resistance of traditional epoxy resin.

[0021] (3) The MOF-modified epoxy resin insulating material of the present invention exhibits excellent performance in electrical insulation. Unlike conventional toughening methods, which are prone to interfacial debonding and forming air gaps under mechanical stress and tension, and thus causing partial discharge, the material of the present invention, under normal conditions without mechanical stress, can capture and restrict the avalanche migration of high-energy electrons by means of the high electron affinity of the MOF central metal node, thus significantly improving the AC breakdown field strength compared with pure epoxy. Under the extremely harsh short-term huge mechanical tensile stress of 30MPa, the breakdown strength of pure epoxy resin decreases significantly due to the generation of a large number of microcracks inside, while the material of the present invention, due to the dense covalent network, greatly suppresses the expansion of the initial microcracks inside, and its breakdown field strength increase not only does not decrease, but actually increases. In extreme tests simulating long-term vibration aging of transformers or reactors, after applying 30MPa stress and undergoing 20,000 high-frequency mechanical fatigue cycles, the breakdown field strength of ordinary MOF-modified epoxy drops directly to the scrap level due to the convergence and expansion of internal microcracks. However, the amino-containing MOF material of this invention utilizes its elastic dissipation energy storage mechanism to effectively reduce the initiation of microcracks and dendritic expansion, and its insulation breakdown field strength remains at a high level.

[0022] 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

[0023] Figure 1 This is a molecular structure diagram of UiO-66 (Zr), MIL-53 (Al), and MIL-101 (Cr) of the present invention; Figure 2 These are breakdown field strength diagrams of the modified epoxy resin insulating materials of Examples 1-12 and Comparative Examples 1-18 of the present invention; Figure 3 These are Young's modulus diagrams of MOF-modified epoxy resin insulating materials from Examples 3, 7, 11, 3, 7, and 11 of this invention. Figure 4 This is a scatter plot comparing the ultimate tensile strength and elongation at break of MOF-modified epoxy resin insulating materials in Examples 3, 7, 11, 3, 7, and 11 of the present invention. Figure 5 This is a comprehensive comparison chart of the tensile fracture toughness of MOF modified epoxy resin insulating materials in Examples 3, 7, 11, 3, 7, and 11 of the present invention. Figure 6 This is a distribution range diagram of the degree of crosslinking values ​​of different crosslinking systems in Examples 3, 7, 11 and Comparative Examples 3, 7, 11, 13 of the present invention. Detailed Implementation

[0024] The technical solution of the present invention will be further described below with reference to the accompanying drawings and embodiments.

[0025] 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.

[0026] In this invention, bisphenol F epoxy resin, also known as bisphenol F diglycidyl ether, CAS number 2095-03-6, was purchased from Huntsman Corporation as GY282 product; methyltetrahydrophthalic anhydride, CAS Registry numbers 11070-44-3 and 19438-64-3, was purchased from Huntsman Corporation as HY918 product; DY073-1 accelerator was purchased from Huntsman Corporation; UiO-66(Zr)-NH2, MIL-53(Al)-NH2, MIL-101(Cr)-NH2, UiO-66(Zr), MIL-53(Al), and MIL-101(Cr) were purchased from Beijing Huawi Ruike Chemical Technology Co., Ltd.

[0027] Example 1 A mechanical stress-resistant MOF-modified epoxy resin insulating material includes an epoxy resin matrix, a curing agent, an accelerator, and an amino-containing MOF-doped reinforcing agent. The mass ratio of the epoxy resin matrix, curing agent, and accelerator is 100:82:0.25, and the mass of the amino-containing MOF-doped reinforcing agent is 0.1% of the total mass of the epoxy resin matrix, curing agent, and accelerator.

[0028] The preparation method of the above-mentioned mechanical stress-resistant 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 UiO-66(Zr)-NH2 nanoparticles with a particle size of 100nm (containing amino MOF doped reinforcing agent). Place them separately in a vacuum drying oven at 60℃ and dry them. Then mix them and place them on the table of a closed constant temperature magnetic stirrer. Stir at 500rpm for 30min to allow the high viscosity epoxy resin to initially coat the powder. Subsequently, in order to completely disperse the strong van der Waals force agglomeration between 100nm particles, immerse the container in the water bath of an industrial-grade ultrasonic cell disruptor and disperse it with a high-frequency microjet at a constant power of 300W for 20min. After microscopic inspection to confirm that there are no micron-sized aggregates, transfer it to a vacuum drying oven, evacuate to -0.095MPa, and keep it for 1h to completely remove the bubbles generated by ultrasonic cavitation, and obtain a mixture. S2. Pour the mixture into a preheated steel mold with dimensions of 100mm×10mm×2mm (compliant with ASTM D638 standard), and place the mold into a programmable oven for multi-stage high-temperature curing: pre-gel at 90℃ for 2 hours, and then cure at 135℃ for 10 hours to ensure that the anhydride reaction and the MOF amino ring-opening reaction are completed simultaneously and completely; then cool down to 25℃ at a rate of 1℃ / min, and gently tap the mold to demold, to obtain a mechanical stress resistant MOF modified epoxy resin insulation material, denoted as EP / UiO-66(Zr)-NH2.

[0029] Example 2 A mechanical stress-resistant MOF-modified epoxy resin insulating material includes an epoxy resin matrix, a curing agent, an accelerator, and an amino-containing MOF-doped reinforcing agent. The mass ratio of the epoxy resin matrix, curing agent, and accelerator is 100:82:0.25, and the mass of the amino-containing MOF-doped reinforcing agent is 0.3% of the total mass of the epoxy resin matrix, curing agent, and accelerator.

[0030] The preparation method of the above-mentioned mechanical stress resistant MOF modified epoxy resin insulating material is the same as that in Example 1, except that: in S1, the amount of UiO-66(Zr)-NH2 nanopowder (containing amino MOF doped reinforcing agent) 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.

[0031] Example 3 A mechanical stress-resistant MOF-modified epoxy resin insulating material includes an epoxy resin matrix, a curing agent, an accelerator, and an amino-containing MOF-doped reinforcing agent. The mass ratio of the epoxy resin matrix, curing agent, and accelerator is 100:82:0.25, and the mass of the amino-containing MOF-doped reinforcing agent is 0.5% of the total mass of the epoxy resin matrix, curing agent, and accelerator.

[0032] The preparation method of the above-mentioned mechanical stress resistant MOF modified epoxy resin insulating material is the same as that in Example 1, except that: in S1, the amount of UiO-66(Zr)-NH2 nanopowder (containing amino MOF doped reinforcing agent) 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 pregeling temperature is 80℃, the pregeling time is 2.5h, the high-temperature curing temperature is 140℃, and the high-temperature curing time is 9h.

[0033] Example 4 A mechanical stress-resistant MOF-modified epoxy resin insulating material includes an epoxy resin matrix, a curing agent, an accelerator, and an amino-containing MOF-doped reinforcing agent. The mass ratio of the epoxy resin matrix, curing agent, and accelerator is 100:82:0.25, and the mass of the amino-containing MOF-doped reinforcing agent is 0.7% of the total mass of the epoxy resin matrix, curing agent, and accelerator.

[0034] The preparation method of the above-mentioned mechanical stress resistant MOF modified epoxy resin insulating material is the same as that in Example 1, except that: in S1, the amount of UiO-66(Zr)-NH2 nanopowder (containing amino MOF doped reinforcing agent) added is 0.638g; in S2, the pregeling temperature is 100℃, the pregeling time is 1.5h, the high-temperature curing temperature is 130℃, and the high-temperature curing time is 11h.

[0035] Example 5 This embodiment is the same as Embodiment 1, except that the amino-containing MOF doping reinforcing agent is MIL-53(Al)-NH2, that is, UiO-66(Zr)-NH2 is not added in S1, but MIL-53(Al)-NH2 nanopowder is added, and mechanical stress resistant MOF modified epoxy resin insulating material is obtained in S2, denoted as EP / MIL-53(Al)-NH2.

[0036] Example 6 This embodiment is the same as Embodiment 2, except that the amino-containing MOF doping reinforcing agent is MIL-53(Al)-NH2, that is, UiO-66(Zr)-NH2 is not added in S1, but MIL-53(Al)-NH2 nanopowder is added, and mechanical stress resistant MOF modified epoxy resin insulating material is obtained in S2, denoted as EP / MIL-53(Al)-NH2.

[0037] Example 7 This embodiment is the same as Example 3, except that the amino-containing MOF doping reinforcing agent is MIL-53(Al)-NH2, that is, UiO-66(Zr)-NH2 is not added in S1, but MIL-53(Al)-NH2 nanopowder is added, and mechanical stress resistant MOF modified epoxy resin insulating material is obtained in S2, which is denoted as EP / MIL-53(Al)-NH2.

[0038] Example 8 This embodiment is the same as Example 4, except that the amino-containing MOF doping reinforcing agent is MIL-53(Al)-NH2, that is, UiO-66(Zr)-NH2 is not added in S1, but MIL-53(Al)-NH2 nanopowder is added, and mechanical stress resistant MOF modified epoxy resin insulating material is obtained in S2, which is denoted as EP / MIL-53(Al)-NH2.

[0039] Example 9 This embodiment is the same as Example 1, except that the amino-containing MOF doping reinforcing agent is MIL-101(Cr)-NH2, that is, UiO-66(Zr)-NH2 is not added in S1, but MIL-101(Cr)-NH2 nanopowder is added, and mechanical stress resistant MOF modified epoxy resin insulating material is obtained in S2, which is denoted as EP / MIL-101(Cr)-NH2.

[0040] Example 10 This embodiment is the same as Embodiment 2, except that the amino-containing MOF doping reinforcing agent is MIL-101(Cr)-NH2, that is, UiO-66(Zr)-NH2 is not added in S1, but MIL-101(Cr)-NH2 nanopowder is added, and mechanical stress resistant MOF modified epoxy resin insulating material is obtained in S2, denoted as EP / MIL-101(Cr)-NH2.

[0041] Example 11 This embodiment is the same as Embodiment 3, except that the amino-containing MOF doping reinforcing agent is MIL-101(Cr)-NH2, that is, UiO-66(Zr)-NH2 is not added in S1, but MIL-101(Cr)-NH2 nanopowder is added, and mechanical stress resistant MOF modified epoxy resin insulating material is obtained in S2, denoted as EP / MIL-101(Cr)-NH2.

[0042] Example 12 This embodiment is the same as Embodiment 4, except that the amino-containing MOF doping reinforcing agent is MIL-101(Cr)-NH2, that is, UiO-66(Zr)-NH2 is not added in S1, but MIL-101(Cr)-NH2 nanopowder is added, and mechanical stress resistant MOF modified epoxy resin insulating material is obtained in S2, denoted as EP / MIL-101(Cr)-NH2.

[0043] Comparative Example 1 This comparative example is the same as Example 1, except that the MOF doping enhancer does not contain amino groups, that is, UiO-66(Zr)-NH2 is not added in S1, but UiO-66(Zr) nanopowder is added. In S2, a mechanical stress-resistant MOF modified epoxy resin insulating material is obtained, denoted as EP / UiO-66(Zr).

[0044] Comparative Example 2 This comparative example is the same as Example 2, except that the MOF doping enhancer does not contain amino groups, that is, UiO-66(Zr)-NH2 is not added in S1, but UiO-66(Zr) nanopowder is added. In S2, a mechanical stress-resistant MOF modified epoxy resin insulating material is obtained, denoted as EP / UiO-66(Zr).

[0045] Comparative Example 3 This comparative example is the same as Example 3, except that the MOF doping enhancer does not contain amino groups, that is, UiO-66(Zr)-NH2 is not added in S1, but UiO-66(Zr) nanopowder is added. In S2, a mechanical stress-resistant MOF modified epoxy resin insulating material is obtained, denoted as EP / UiO-66(Zr).

[0046] Comparative Example 4 This comparative example is the same as Example 4, except that the MOF doping enhancer does not contain amino groups, that is, UiO-66(Zr)-NH2 is not added in S1, but UiO-66(Zr) nanopowder is added. In S2, a mechanical stress-resistant MOF modified epoxy resin insulating material is obtained, denoted as EP / UiO-66(Zr).

[0047] Comparative Example 5 This comparative example is the same as Example 5, except that the MOF doping enhancer does not contain amino groups, that is, MIL-53(Al)-NH2 is not added in S1, but MIL-53(Al) nanopowder is added. In S2, a mechanical stress-resistant MOF modified epoxy resin insulating material is obtained, denoted as EP / MIL-53(Al).

[0048] Comparative Example 6 This comparative example is the same as Example 6, except that the MOF doping enhancer does not contain amino groups, that is, MIL-53(Al)-NH2 is not added in S1, but MIL-53(Al) nanopowder is added. In S2, a mechanical stress-resistant MOF modified epoxy resin insulating material is obtained, denoted as EP / MIL-53(Al).

[0049] Comparative Example 7 This comparative example is the same as Example 7, except that the MOF doping enhancer does not contain amino groups, that is, MIL-53(Al)-NH2 is not added in S1, but MIL-53(Al) nanopowder is added. In S2, a mechanical stress-resistant MOF modified epoxy resin insulating material is obtained, denoted as EP / MIL-53(Al).

[0050] Comparative Example 8 This comparative example is the same as Example 8, except that the MOF doping enhancer does not contain amino groups, that is, MIL-53(Al)-NH2 is not added in S1, but MIL-53(Al) nanopowder is added. In S2, a mechanical stress-resistant MOF modified epoxy resin insulating material is obtained, denoted as EP / MIL-53(Al).

[0051] Comparative Example 9 This comparative example is the same as Example 9, except that the MOF doping enhancer does not contain amino groups, that is, MIL-101(Cr)-NH2 is not added in S1, but MIL-101(Cr) nanopowder is added. In S2, a mechanical stress-resistant MOF modified epoxy resin insulating material is obtained, denoted as EP / MIL-101(Cr).

[0052] Comparative Example 10 This comparative example is the same as Example 10, except that the MOF doping enhancer does not contain amino groups, that is, MIL-101(Cr)-NH2 is not added in S1, but MIL-101(Cr) nanopowder is added. In S2, a mechanical stress resistant MOF modified epoxy resin insulating material is obtained, denoted as EP / MIL-101(Cr).

[0053] Comparative Example 11 This comparative example is the same as Example 11, except that the MOF doping enhancer does not contain amino groups, that is, MIL-101(Cr)-NH2 is not added in S1, but MIL-101(Cr) nanopowder is added. In S2, a mechanical stress resistant MOF modified epoxy resin insulating material is obtained, denoted as EP / MIL-101(Cr).

[0054] Comparative Example 12 This comparative example is the same as Example 12, except that the MOF doping enhancer does not contain amino groups, that is, MIL-101(Cr)-NH2 is not added in S1, but MIL-101(Cr) nanopowder is added. In S2, a mechanical stress resistant MOF modified epoxy resin insulating material is obtained, denoted as EP / MIL-101(Cr).

[0055] Comparative Example 13 This comparative example is the same as Example 1, except that the modified epoxy resin insulating material does not include MOF, that is, UiO-66(Zr)-NH2 nanopowder is not added to S1.

[0056] The molecular structures of UiO-66 (Zr), MIL-53 (Al), and MIL-101 (Cr) are as follows: Figure 1 As shown, where Figure 1 (a) in the diagram is the molecular structure of MIL-53(Al). Figure 1(b) in the diagram is the molecular structure of UiO-66(Zr). Figure 1 (c) in the diagram is the molecular structure of MIL-101(Cr). From... Figure 1 As can be seen, MIL-53(Al) is formed by AlO4(OH)2 chains linked with terephthalic acid (BDC), forming a one-dimensional rhombic channel with extremely small pore size; UiO-66(Zr) is constructed by Zr6O4(OH)4 octanuclear clusters and BDC ligands, exhibiting a three-dimensional face-centered cubic (fcu) cage-like structure with pore size of 8-12 Å; MIL-101(Cr) is constructed by Cr3O clusters and BDC ligands, forming a huge cage-like channel (diameter 29-34 Å), connected by 12 Å and 16 Å pore windows.

[0057] The modified epoxy resin insulating materials of Examples 1-12 and Comparative Examples 1-18 were tested using a high-voltage DC power supply and ball-plate electrodes. (Comparative Examples 13 and 1-4 used EP / UiO-66(Zr)-NH2 with UiO-66(Zr)-NH2 content of 0, 0.1%, 0.3%, 0.5%, and 0.7% of the total mass of epoxy resin matrix, curing agent, and accelerator, respectively. Comparative Examples 13 and 5-8 used EP / MIL-53(Al)-NH2 with MIL-53(Al)-NH2 content of 0, 0.1%, 0.3%, 0.5%, and 0.7% of the total mass of epoxy resin matrix, curing agent, and accelerator, respectively. Comparative Examples 13 and 9-12 used MIL-101(Cr)-NH2 with MIL-101(Cr)-NH2 content of 0, 0.1%, 0.3%, and 0.7% of the total mass of epoxy resin matrix, curing agent, and accelerator, respectively.) The breakdown field strengths of EP / MIL-101(Cr)-NH2 obtained by adding 5% and 0.7% of epoxy resin matrix, curing agent, and accelerator were as follows: EP / UiO-66(Zr) obtained by adding UiO-66(Zr) at mass percentages of 0%, 0.1%, 0.3%, 0.5%, and 0.7% of epoxy resin matrix, curing agent, and accelerator in Comparative Examples 13 and 5-8; EP / MIL-53(Al) obtained by adding MIL-53(Al) at mass percentages of 0%, 0.1%, 0.3%, 0.5%, and 0.7% of epoxy resin matrix, curing agent, and accelerator in Comparative Examples 13 and 9-12; and EP / MIL-101(Cr) obtained by adding MIL-101(Cr) at mass percentages of 0%, 0.1%, 0.3%, 0.5%, and 0.7% of epoxy resin matrix, curing agent, and accelerator in Comparative Examples 13 and 9-12, respectively, were as follows: Figure 2 As shown, where Figure 2 In the figure, (a) represents the breakdown field strength of different modified epoxy resin insulating materials under no mechanical stress. Figure 2 (b) represents the breakdown field strength of different modified epoxy resin insulating materials under a tensile stress of 30 MPa. Figure 2(c) represents the breakdown field strength of different modified epoxy resin insulating materials after 20,000 cycles of fatigue treatment with a mechanical stress of 30 MPa (triangular wave, stress period of 1 s).

[0058] from Figure 2 As shown in (a), the breakdown field strength of epoxy resin increases after MOF modification, and the improvement effect of the breakdown field strength of epoxy resin modified with amino-containing MOF is significantly better than that of epoxy resin without amino-containing MOF modification. With the increase of doping content, the breakdown strength of epoxy resin modified with amino-containing MOF shows a trend of first increasing and then decreasing. UiO-66(Zr)-NH2 has the best effect on improving the breakdown field strength of epoxy resin, and its breakdown field strength is 121% of that of unmodified epoxy resin; for the same MOF, the doping content of 0.3wt%-0.5wt% is optimal.

[0059] from Figure 2 As shown in (b), for epoxy resin without MOF modification, tensile stress reduced the breakdown field strength by 4.4%. Unlike the stress-free condition, different MOFs had varying effects on the breakdown field strength of epoxy resin under tensile stress. Overall, doping with very small amounts of MIL-53(Al), UiO-66(Zr), and MIL-101(Cr) had a certain positive effect on improving the breakdown field strength of epoxy resin, but the effect was limited. When the doping amount increased, the breakdown field strength of the epoxy resin sample decreased significantly. In particular, for MIL-101(Cr), the breakdown field strength at 0.7wt% doping was 29.3% lower than that of unmodified epoxy resin. Conversely, MIL-53(Al)-NH2, UiO-66(Zr)-NH2, and MIL-101(Cr)-NH2 had a more significant and stable effect on improving the insulation performance of epoxy resin. For 0.3wt% MIL-53(Al)-NH2 and UiO-66(Zr)-NH2 doped epoxy resins, the breakdown field strength was increased by 23.9% and 25.4%, respectively.

[0060] from Figure 2As shown in (c), the breakdown field strength of the unmodified epoxy resin decreased by 3.1% compared to before fatigue treatment. However, the breakdown field strength of the MOF-modified epoxy resin showed significant differences after mechanical fatigue treatment. For the three amino-containing MOF-modified epoxy resins MIL-53(Al)-NH2, UiO-66(Zr)-NH2, and MIL-101(Cr)-NH2, their breakdown field strengths could still be maintained at a high level. Among them, the breakdown field strengths of the MIL-53(Al)-NH2 and UiO-66(Zr)-NH2 modified epoxy resins were almost the same as before fatigue treatment. The breakdown field strength of the three MOF-modified epoxy resins, MIL-53(Al), UiO-66(Zr), and MIL-101(Cr), decreased sharply after fatigue treatment. The performance degradation gradually increased with the increase of doping content. Among them, the breakdown field strength of EP / MIL-101(Cr) dropped to 50kV / mm, which is 34.7% of that of the unmodified epoxy resin.

[0061] The Young's modulus of the MOF-modified epoxy resin insulating materials of Examples 3, 7, 11, Comparative Examples 3, 7, and 11, as well as pure epoxy resin, was characterized based on ASTM D638 standard. The results are as follows: Figure 3 As shown. From Figure 3 As can be seen, the Young's modulus of epoxy resins decreased to varying degrees after the introduction of MOF. Under the same stress, the larger strain was mainly contributed by two factors. First, the deformation of the pore size within the doped MOF itself under tensile stress; second, the relative slip between the MOF and the matrix. In the MOF-modified epoxy resins of Comparative Examples 7, 3, and 11, as well as Examples 7, 3, and 11, the Young's modulus decreased with increasing MOF pore size. This is because larger pore sizes create greater stretching space within the molecule. MOFs without -NH2 reduced the Young's modulus of epoxy resins by 6.1-21.5%, while MOFs containing -NH2 reduced it by 2.0-11.0%. This is because the covalent structure formed by -NH2 and the epoxy resin restricts the slip between the MOF and the matrix, causing the stretchability of the MOF's pore structure itself to play a major role during the stretching process.

[0062] Mechanical fatigue treatment was performed on the MOF-modified epoxy resin insulating materials of Examples 3, 7, 11, Comparative Examples 3, 7, and 11, as well as pure epoxy resin, using a tensile testing machine. The mechanical stress used for fatigue treatment was set to a triangular wave, with a maximum stress of 30 MPa, a stress period of 1 second, and 20,000 fatigue cycles. Based on ASTM D638 standard, the results are as follows: Figure 4 As shown. From Figure 4As can be seen, doping with MIL-53(Al), UiO-66(Zr), and MIL-101(Cr) reduced the tensile strength of epoxy resin by 23.2-29.6% and the elongation at break by 19.0-38.0%. Doping with MIL-53(Al)-NH2, UiO-66(Zr)-NH2, and MIL-101(Cr)-NH2 increased the tensile strength of epoxy resin by 17.1-30.8% and the elongation at break by 9.0-26.0%. This indicates that MOF participates in the crosslinking reaction of epoxy resin, and the resulting epoxy-curing agent-MOF ternary system significantly improves the structural stability of epoxy resin. Simultaneously, the flexibility of MOF improves the ductility of epoxy resin.

[0063] Based on ASTM D638 standard, the mechanical tensile properties of MOF-modified epoxy resin insulation materials (Examples 3, 7, 11, Comparative Examples 3, 7, and 11) and pure epoxy resin were measured using an electronic universal testing machine to characterize their toughness. The results are as follows: Figure 5 As shown, toughness represents the total energy absorbed by a material during deformation and fracture under stress. From... Figure 5 As can be seen, MIL-53(Al), UiO-66(Zr), and MIL-101(Cr) have a significant negative effect on the toughness of epoxy resin. The toughness of all three MOFs decreased by more than 40%. However, the toughness of epoxy resins modified with MIL-53(Al)-NH2, UiO-66(Zr)-NH2, and MIL-101(Cr)-NH2 increased by 33.9-45.5%. This will help improve the insulation reliability of epoxy resin under long-term high mechanical stress.

[0064] Because the curing reaction process is greatly affected by the relative positions of the reactants at the initial unit cell establishment, the curing reaction processes of different systems were simulated multiple times. Based on high-performance molecular dynamics simulations, the distribution range of crosslinking degree values ​​for different crosslinking systems in Examples 3, 7, 11 and Comparative Examples 3, 7, 11, 13 was studied, and the results are as follows: Figure 6 As shown. From Figure 6As can be seen from the simulation, the crosslinking degree of the pure epoxy resin and curing agent system is around 96%. When MIL-53 (Al), UiO-66 (Zr), and MIL-101 (Cr) are doped, the average crosslinking degree decreases slightly, and the dispersion between simulation results is significant. This is because the introduction of these three MOFs without -NH2 ions occupies some space within the unit cell, hindering the effective contact between epoxy resin and curing agent molecules to some extent. However, in some cases, even with some space occupied, sufficient reaction space still exists. For epoxy resins doped with MOFs containing -NH2 ions, although the MOFs occupy space, they also provide abundant crosslinking sites, and a large number of amine curing reactions occur in the cured system, ensuring that the crosslinking degree remains at 100%.

[0065] Therefore, this invention employs the aforementioned mechanical stress-resistant MOF modified epoxy resin insulating material, its preparation method, and its application. By constructing a ternary fully cross-linked system of MOF-epoxy-curing agent, and combining the molecular-level elastic extension energy storage mechanism of MOF with the charge trapping function of the central metal node, the synergistic improvement of cross-linking degree, mechanical toughness, and insulation strength is achieved, providing an insulating substrate guarantee for large-scale power equipment that has been subjected to the synergistic effects of multiple physical fields for a long time.

[0066] 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 mechanically stress-resistant MOF-modified epoxy resin insulating material, characterized in that: It includes an epoxy resin matrix, a curing agent, an accelerator, and an amino-containing metal-organic framework doped reinforcing agent. The mass ratio of the epoxy resin matrix, curing agent, and accelerator is 100:82:0.25, and the mass of the amino-containing metal-organic framework doped reinforcing agent is 0.1%-0.7% of the total mass of the epoxy resin matrix, curing agent, and accelerator.

2. The mechanical stress-resistant MOF-modified epoxy resin insulating material according to claim 1, characterized in that: Amino-containing metal-organic framework doping enhancers include UiO-66(Zr)-NH2, MIL-53(Al)-NH2, or MIL-101(Cr)-NH2, with a particle size of 100 nm.

3. The mechanical stress-resistant 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 mechanical stress-resistant 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 mechanical stress-resistant 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 mechanically stress-resistant MOF-modified epoxy resin insulating material as described in any one of claims 1-5, characterized in that: Includes the following steps: S1. Vacuum dry, mix, stir, ultrasonically disperse, and degas the epoxy resin matrix, curing agent, accelerator, and amino-containing metal-organic framework doped reinforcing agent to obtain a mixture. S2. The mixture is cured at high temperature, cooled to 25°C, and demolded to obtain a mechanically stress-resistant metal-organic framework modified epoxy resin insulating material.

7. The method for preparing a mechanically stress-resistant MOF-modified epoxy resin insulating material according to claim 6, characterized in that: In S1, the stirring speed is 400-600 rpm, the stirring time is 20-40 min, the ultrasonic dispersion power is 200-400 W, the ultrasonic dispersion time is 10-30 min, the degassing pressure is -0.095 MPa, and the degassing time is 60 min.

8. The method for preparing a mechanically stress-resistant MOF-modified epoxy resin insulating material according to claim 6, characterized in that: In S2, high-temperature curing includes two stages: pre-gelling and high-temperature post-curing. The pre-gelling temperature is 80-100℃ and the pre-gelling time is 1.5-2.5h. The high-temperature post-curing temperature is 130-140℃ and the high-temperature post-curing time is 9-11h.

9. The method for preparing a mechanically stress-resistant MOF-modified epoxy resin insulating material according to claim 6, characterized in that: In S2, the cooling rate is 0.5-1.5℃ / min.

10. An application of a mechanically stress-resistant MOF-modified epoxy resin insulating material, characterized in that: The mechanical stress-resistant MOF modified epoxy resin insulating material according to any one of claims 1-5 is used in the insulating structural components of power equipment that are subjected to the combined effects of strong electric fields, large mechanical stress, and temperature alternating thermal stress for a long period of time.

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