Epoxy composite insulating material with triple interpenetrating network and preparation method and application thereof

Abstract

The application belongs to the technical field of epoxy resins, and particularly relates to an epoxy composite insulating material with triple interpenetrating networks, a preparation method and application. The preparation method of the epoxy composite insulating material comprises the steps of pre-dissolving PVDF, preparing a prepolymer, mixing and defoaming, and synchronous polymerization and in-situ crystallization, and the epoxy composite insulating material with triple interpenetrating networks is constructed. The polyvinylidene fluoride nanocrystals in the triple interpenetrating networks refine the micron-level polydimethylsiloxane phase region on one hand, and on the other hand, when the epoxy composite insulating material is in an extremely low temperature condition, the impact resistance of the epoxy composite insulating material is improved, and the epoxy-based insulating material is excellent in comprehensive performance. Therefore, the technical problem of low comprehensive performance of the epoxy resin-based insulating material in the prior art is solved.

Description

Technical Field

[0001] This application belongs to the field of epoxy resin technology, and particularly relates to an epoxy composite insulating material with a triple interpenetrating network, its preparation method, and its application. Background Technology

[0002] Gas-insulated switchgear (GIS) is a core piece of equipment in ultra-high voltage power transmission systems. It has advantages such as small footprint, high insulation reliability, simple operation and maintenance, and strong resistance to harsh environments. It is widely used in substations and converter stations, undertaking the key functions of power transmission, distribution, and fault isolation. In GIS equipment, epoxy resin-based insulating components such as pot insulators, insulating rods, and post insulators are core components. They not only provide electrical insulation and mechanical support, but also have to withstand the SF6 gas pressure, operating thermal stress, and mechanical vibration inside the equipment for a long time. Their performance stability directly determines the operational safety and service life of GIS equipment.

[0003] As ultra-high-voltage transmission lines extend to high-altitude and cold regions with large diurnal temperature variations, epoxy resin-based insulation components of GIS and other electrical equipment face the challenge of extreme low-temperature conditions ranging from -40℃ to -60℃. Traditional bisphenol A type epoxy resins, after curing, have high cross-linking density, high molecular chain rigidity, and small free volume, making them prone to brittle fracture at low temperatures. When the ambient temperature drops below -20℃, the unnotched impact strength of pure epoxy resin drops sharply. Under the combined effects of thermal cycling stress generated by the start-up and shutdown of GIS equipment and SF6 gas pressure, microcracks are easily generated and rapidly propagate. Microcracks can lead to SF6 gas leakage, insulation breakdown, and even equipment explosions. The cracking failure rate of epoxy resin-based insulation components such as basin insulators is high in winter low temperatures, causing huge economic losses and potential safety hazards to the power grid. Therefore, developing epoxy resin materials with high cold resistance, high insulation, high heat resistance, and high mechanical strength has become a key technical problem that urgently needs to be solved in the development of ultra-high-voltage GIS equipment in cold regions.

[0004] To improve the low-temperature toughness of epoxy resin-based insulation components, in addition to using rubber elastomers or nanofillers for toughening modification, industry technicians also use interpenetrating polymer networks (IPNs) for toughening modification. The most representative of these is epoxy resin-polydimethylsiloxane (PDMS), which has a binary interpenetrating polymer network. However, on the one hand, the solubility parameters of PDMS and epoxy resin are very different, which makes macroscopic phase separation easy to occur. This results in lower overall performance and makes it difficult to meet the requirements of GIS equipment in cold regions. Therefore, it is necessary to develop new epoxy resin-based insulation components. Summary of the Invention

[0005] In view of this, this application provides an epoxy composite insulating material with a triple interpenetrating network, its preparation method, and its application, to solve the technical problem of low overall performance of epoxy resin-based insulating materials in the prior art.

[0006] The first aspect of this application provides a method for preparing an epoxy composite insulating material with a triple interpenetrating network, comprising the following steps: Pre-dissolution step of PVDF: Add polyvinylidene fluoride to epoxy resin at a mass ratio of 5~10:100 and stir to dissolve to obtain PVDF / EP mixed solution; Preparation steps of the prepolymer: Vinyl polydimethylsiloxane, free radical initiator and silane coupling agent are added to PVDF / EP mixed solution and stirred and mixed, and then vinyl polydimethylsiloxane pre-crosslinking reaction is carried out to obtain mixed viscous containing PDMS prepolymer; The mixing and degassing steps are as follows: epoxy resin curing agent, epoxy resin curing accelerator, and silane coupling agent modified nano-reinforcing filler are added to a mixed viscous liquid containing PDMS prepolymer, stirred and mixed, and then vacuum degassed to obtain an epoxy composite insulation material precursor. The steps of simultaneous polymerization and in-situ crystallization are as follows: the epoxy composite insulation material precursor is subjected to vinyl polydimethylsiloxane crosslinking reaction, epoxy resin pre-crosslinking reaction, epoxy resin crosslinking reaction and polyvinylidene fluoride in-situ crystallization in sequence to obtain epoxy composite insulation material with triple interpenetrating network.

[0007] Preferably, in the PVDF pre-dissolution step, the polyvinylidene fluoride has a number average molecular weight of 50,000 to 80,000 and a crystallinity of ≥50%.

[0008] Preferably, in the PVDF pre-dissolution step, the epoxy resin is selected from bisphenol A type epoxy resin, bisphenol F type epoxy resin, and alicyclic epoxy resin, such as bisphenol A type epoxy resin E-51.

[0009] Preferably, in the PVDF pre-dissolution step, the stirring and dissolution temperature is 110~130℃, the rotation speed is 400~600r / min, and the time is 2~6h.

[0010] Preferably, in the PVDF pre-dissolution step, the stirring and dissolution process is as follows: polyvinylidene fluoride is added in 3 to 10 batches at intervals of 10 to 20 minutes.

[0011] Preferably, in the prepolymer preparation step, the vinyl polydimethylsiloxane is selected from terminal vinyl polydimethylsiloxane and / or side vinyl polydimethylsiloxane; The free radical initiator is selected from inorganic peroxide initiators or organic peroxide initiators, such as benzoyl peroxide (BPO) and 2,5-dimethyl-2,5-di-tert-butylperoxide (commonly known as bis(2,5-di-5)). The silane coupling agent is selected from γ-glycidoxypropyltrimethoxysilane (KH-560).

[0012] Preferably, in the preparation step of the prepolymer, the mass ratio of the vinyl polydimethylsiloxane, the free radical initiator, and the silane coupling agent is 15~25:0.3~0.8:1~3.

[0013] Preferably, in the preparation step of the prepolymer, the temperature of the vinyl polydimethylsiloxane pre-crosslinking reaction is 75~85℃ and the time is 0.5~1.5h.

[0014] Preferably, in the mixing and degassing steps, the epoxy resin curing agent is selected from anhydride curing agents, such as methylhexahydrophthalic anhydride (MeHHPA). The epoxy resin curing accelerator is selected from tertiary amine curing accelerators, such as 2,4,6-tris(dimethylaminomethyl)phenol (DMP-30). The silane coupling agent modified nano-reinforcing filler is selected from at least one of silane coupling agent modified nano-silica, silane coupling agent modified nano-calcium carbonate, and silane coupling agent modified alumina.

[0015] Preferably, in the mixing and degassing steps, the mass ratio of the epoxy resin curing agent, epoxy resin curing accelerator, and silane coupling agent modified nano-reinforcing filler is 80~90:0.5~1:3~5.

[0016] Preferably, in the mixing and degassing steps, the stirring speed is 600~1000 r / min, the time is 20~60 min, and the temperature is 55~65℃.

[0017] The vacuum degassing process involves a vacuum degree of -0.06 to -0.12 MPa, a time of 10 to 30 minutes, and a temperature of 55 to 65°C.

[0018] Preferably, in the steps of simultaneous polymerization and in-situ crystallization, the temperature of the vinyl polydimethylsiloxane crosslinking reaction is 75~85°C and the time is 1.5~3h; The epoxy resin pre-crosslinking reaction is carried out at a temperature of 90~110℃ for 2.5~5h. The temperature for the epoxy resin crosslinking reaction and the in-situ crystallization of polyvinylidene fluoride are 120~140℃, and the time is 1.5~3h.

[0019] Preferably, in the steps of simultaneous polymerization and in-situ crystallization, the step of sequentially subjecting the epoxy composite insulating material precursor to a vinyl polydimethylsiloxane crosslinking reaction, an epoxy resin pre-crosslinking reaction, an epoxy resin crosslinking reaction, and polyvinylidene fluoride in-situ crystallization specifically involves: casting the epoxy composite insulating material precursor into an insulating mold, and sequentially performing a vinyl polydimethylsiloxane crosslinking reaction, the epoxy resin pre-crosslinking reaction, the epoxy resin crosslinking reaction, and polyvinylidene fluoride in-situ crystallization.

[0020] Preferably, after the epoxy resin crosslinking reaction and the in-situ crystallization of polyvinylidene fluoride, a post-curing process is also included; the post-curing temperature is 140~160℃ and the time is 0.5~1.5h.

[0021] Preferably, the post-curing process further includes a demolding process; the demolding process includes: naturally cooling to room temperature and removing the epoxy composite insulation material with a triple interpenetrating network.

[0022] Preferably, after demolding, the process further includes curing the epoxy composite insulation material with a triple interpenetrating network at 110~130℃ for 3~5 hours.

[0023] Preferably, the insulating component mold is selected from the internal insulating component mold of electrical equipment or the external insulating component mold of electrical equipment.

[0024] Preferably, the insulating component mold is selected from at least one of the following: basin insulator mold, insulating tie rod mold, post insulator mold, and outgoing bushing mold.

[0025] The second aspect of this application provides an epoxy composite insulating material having a triple interpenetrating network, prepared by the preparation method described in the first aspect.

[0026] The third aspect of this application provides the application of an epoxy composite insulation material with a triple interpenetrating network, as described in the second aspect, in electrical equipment in cold and high-altitude regions.

[0027] Preferably, the electrical equipment for high-altitude and cold regions includes gas-insulated switchgear, transformers, converter valves, and other electrical equipment that operate in high-altitude and cold regions with large temperature differences between day and night.

[0028] The fourth aspect of this application provides an electrical device for use in cold regions, including an epoxy composite insulation material with a triple interpenetrating network as described in the second aspect.

[0029] Preferably, the electrical equipment is a gas-insulated switchgear, transformer, converter valve, or other electrical equipment.

[0030] Compared with the prior art, the method for preparing an epoxy composite insulating material with a triple interpenetrating network provided in this application has at least the following beneficial effects: 1. The preparation method provided in this application constructs a triple interpenetrating network through the synergistic mechanism of polyvinylidene fluoride pre-dissolution homogenization and interpenetrating network confined crystallization during the preparation of the epoxy composite insulating material. The polyvinylidene fluoride nanocrystals in the triple interpenetrating network refine the micron-sized polydimethylsiloxane phase region on the one hand, and on the other hand, improve the impact resistance of the epoxy composite insulating material when subjected to external impact under extreme low temperature conditions. It is an epoxy-based insulating material with excellent comprehensive performance.

[0031] 2. The preparation method provided in this application uses polyvinylidene fluoride (PVDF) with a specific dosage range and number average molecular weight. When a mass ratio of PVDF to bisphenol A epoxy resin E-51 of around 6:100 is selected, such as 5~10:100, it can avoid the defects of insufficient PVDF dosage, which would prevent the formation of a continuous nanocrystalline network and result in insignificant enhancement and refinement of the phase region. On the other hand, it can avoid the defects of excessive PVDF dosage, which would easily form large-sized spherulites and lead to a decrease in insulation performance. At the same time, selecting PVDF with a number average molecular weight of around 65,000, such as 50,000~80,000, can avoid the defects of low crystallinity and poor enhancement effect when the molecular weight is too low. On the other hand, it can avoid the defects of difficult dissolution and easy phase separation when the molecular weight is too high.

[0032] 3. The preparation method provided in this application uses two parts of γ-glycidyl etheroxypropyltrimethoxysilane. The second part of γ-glycidyl etheroxypropyltrimethoxysilane is used to modify nano-silica. The first part of γ-glycidyl etheroxypropyltrimethoxysilane is the core additive for constructing a stable triple interpenetrating network. It specifically acts on the two organic interfaces of polyvinylidene fluoride-epoxy resin and PDMS-epoxy resin. It connects the polyvinylidene fluoride nanocrystals and epoxy resin network through "covalent bond-hydrogen bond" composite action. It also acts as a molecular bridge to improve the compatibility of PDMS and epoxy resin and refine the PDMS phase region. Finally, the three networks are tightly combined into a whole. The second part of γ-glycidyl etheroxypropyltrimethoxysilane is added because PVDF has been completely dissolved and PDMS has not yet been cross-linked. KH-560 can be uniformly dispersed and fully reacted. Adding it in advance will affect the dissolution of PVDF. Adding it in a later manner will prevent it from playing its role due to the curing reaction being too fast. 4. The preparation method provided in this application uses vinyl-terminated polydimethylsiloxane with a specific dosage range and vinyl content. When a mass ratio of vinyl-terminated polydimethylsiloxane to bisphenol A type epoxy resin E-51 of around 20:100 is selected, for example, a mass ratio of 15~25, it avoids the defects of insufficient low-temperature toughening effect due to excessive dosage, which is not conducive to the impact strength at -60℃. On the other hand, it avoids the defects of excessive dosage, which leads to a significant decrease in modulus and heat resistance, and an excessively low glass transition temperature. When a vinyl content of around 0.8 mmol / g is selected, for example, 0.5~1.0 mmol / g, it can avoid the defects of insufficient crosslinking degree and easy precipitation of PDMS due to excessively low vinyl content. On the other hand, it can avoid the defects of increased rigidity of PDMS network and decreased toughening effect when the vinyl content is too high. Attached Figure Description

[0033] To more clearly illustrate the technical solutions in the specific embodiments of this application or the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this application. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0034] Figure 1 This is a schematic flowchart illustrating a method for preparing an epoxy composite insulating material with a triple interpenetrating network, as provided in Embodiment 1 of this application. Detailed Implementation

[0035] This application provides an epoxy composite insulating material with a triple interpenetrating network, its preparation method, and its application, which addresses the technical problem of low overall performance of epoxy resin-based insulating materials in the prior art.

[0036] The technical solutions of this application will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this application. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0037] Example 1

[0038] This embodiment provides a method for preparing an epoxy composite insulating material with a triple interpenetrating network, the process flow diagram of which is shown below. Figure 1 As shown, the preparation method includes the following steps: raw material preparation, PVDF pre-dissolution, prepolymer preparation, mixing and degassing, simultaneous polymerization and in-situ crystallization, cooling and demolding, and post-treatment.

[0039] Raw material preparation steps: According to the mass ratio of 100:20:8:85:0.7:0.6:2:0.6:2, bisphenol A type epoxy resin E-51, vinyl-terminated polydimethylsiloxane (PDMS), polyvinylidene fluoride (PVDF), methylhexahydrophthalic anhydride (MeHHPA), 2,4,6-tris(dimethylaminomethyl)phenol (DMP-30), benzoyl peroxide (BPO), the first part of γ-glycidoxypropyltrimethoxysilane (KH-560), the second part of γ-glycidoxypropyltrimethoxysilane (KH-560), and fumed nano silica were weighed as raw materials for epoxy composite insulation material. The specifications of the raw materials for epoxy composite insulation materials include: bisphenol A type epoxy resin E-51 with an epoxy value of approximately 0.50 eq / 100g; vinyl-terminated polydimethylsiloxane (PDMS) with a vinyl content of approximately 0.8 mmol / g and a viscosity of approximately 3000 mPa. The polyvinylidene fluoride (PVDF) has a number-average molecular weight of approximately 65,000 and a crystallinity ≥50%; the methylhexahydrophthalic anhydride (MeHHPA) has an anhydride value of approximately 670 mg KOH / g; the 2,4,6-tris(dimethylaminomethyl)phenol (DMP-30) has a purity ≥99%; the benzoyl peroxide (BPO) has a purity ≥99%; the γ-glycidyl etheroxypropyltrimethoxysilane (KH-560) has a purity ≥98%; and the specific surface area of ​​fumed silica nanoparticles is 200 ± 20 m². 2 / g.

[0040] The PVDF pre-dissolution steps include: Polyvinylidene fluoride (PVDF) is pre-treated by drying it in a vacuum drying oven at 80°C and -0.09 MPa for 12 hours to remove moisture until the moisture content is ≤0.05%, thus obtaining pre-treated PVDF to avoid the generation of bubbles during subsequent processing. Weigh out bisphenol A type epoxy resin E-51 and add it to a three-necked flask equipped with a stirrer and heating mantle. Heat the flask to 120°C and stir at a speed of 500 r / min. Then add pre-treated polyvinylidene fluoride in four batches, with each batch consisting of two portions and an interval of 15 minutes, ensuring that the polyvinylidene fluoride is completely dissolved. Continue stirring for 2 hours to obtain a homogeneous and transparent polyvinylidene fluoride / epoxy resin mixed solution. Cool the solution to 60°C for later use.

[0041] Prepolymer preparation steps: To a polyvinylidene fluoride / epoxy resin mixed solution, add weighed terminal vinyl polydimethylsiloxane, benzoyl peroxide, and the first portion of γ-glycidyl etheroxypropyltrimethoxysilane. Adjust the stirring rate to 600 r / min, raise the temperature to 80℃, and carry out a pre-crosslinking reaction of vinyl polydimethylsiloxane for 1 hour to allow partial crosslinking of vinyl polydimethylsiloxane and form vinyl polydimethylsiloxane prepolymer. At this time, the system is a pale yellow viscous liquid containing PDMS prepolymer, with no obvious phase separation.

[0042] The mixing and degassing steps include: Weigh out fumed nano-silica and the second part of γ-glycidyl etheroxypropyltrimethoxysilane and add them to a high-speed mixer. Set the temperature to 80℃ and the stirring speed to 1000r / min and mix for 30 minutes. This allows the epoxy groups of γ-glycidyl etheroxypropyltrimethoxysilane to react with the hydroxyl groups on the surface of the nano-silica to form an organosilane layer. This yields silane coupling agent modified nano-silica, which improves the compatibility with epoxy resin. The temperature of a pale yellow viscous liquid containing PDMS prepolymer was lowered to 60°C. Weighed amounts of methylhexahydrophthalic anhydride, 2,4,6-tris(dimethylaminomethyl)phenol, and silane coupling agent-modified nano-silica were added sequentially. The mixture was stirred at 800 r / min for 30 minutes to ensure uniform mixing of all components, resulting in a mixture. The mixture was then transferred to a vacuum degassing chamber and degassed at 60°C and -0.09 MPa for 20 minutes to remove air bubbles introduced during stirring until no air bubbles overflowed from the surface of the mixture, thus obtaining the epoxy composite insulation material precursor.

[0043] Steps for simultaneous polymerization and in-situ crystallization: The epoxy composite insulation material precursor was slowly poured into a mold preheated to 80°C. The mold was pre-coated with a release agent and then placed in a programmed temperature oven. First, it was held at 80°C for 2 hours to allow the vinyl-terminated polydimethylsiloxane to complete the cross-linking reaction, forming the PDMS second network. Then, it was held at 100°C for 3 hours to allow the epoxy resin to undergo a pre-cross-linking reaction and complete preliminary curing, forming the primary structure of the EP first network. Next, it was held at 130°C for 2 hours to allow the epoxy resin to fully cure. Simultaneously, PVDF crystallized in situ under the confinement of the interpenetrating network, forming a PVDF nanocrystalline network as the third network, thus forming an epoxy composite insulation material with a triple interpenetrating network of EP, PDMS, and PVDF. Finally, it was held at 150°C for 1 hour for post-curing to eliminate internal stress. In this embodiment, the reaction is carried out at around 80°C. At this temperature, the decomposition rate of the free radical initiator BPO is moderate, and the PDMS crosslinking reaction proceeds smoothly, avoiding phase separation caused by excessively rapid crosslinking. The ability of polyvinylidene fluoride (PVDF) to undergo in-situ crystallization and form a third network stems from the synergistic mechanism of pre-dissolution homogenization and interpenetrating network confined crystallization. First, PVDF is completely dissolved in epoxy resin at 120°C to form a homogeneous solution with molecular-level dispersion, providing a homogeneous nucleation basis for in-situ crystallization. Subsequently, in the first two stages of simultaneous polymerization, PDMS and epoxy resin crosslink sequentially to form an interpenetrating three-dimensional microporous framework, confining the PVDF molecular chains within a confined space of 50-200 nm. When the temperature rises to 130°C, within the optimal crystallization temperature range for PVDF, PVDF undergoes further crystallization. Under confinement, the sub-chains cannot aggregate over long distances and can only form nanocrystals with a particle size of around 100 nm. At the same time, KH-560 acts as a heterogeneous nucleation point to further induce nanoscale crystallization and avoid the formation of large-sized spherulites. The formed polyvinylidene fluoride nanocrystals are not isolated particles, but form a continuous physical network through molecular chain entanglement. Each polyvinylidene fluoride nanocrystal is composed of segments of multiple polyvinylidene fluoride molecular chains arranged in an orderly manner. The remaining part of the molecular chains extends into the amorphous region and entangles with other nanocrystals, making the polyvinylidene fluoride phase a continuous three-dimensional physical cross-linked network. This network forms chemical bonds with epoxy resin through KH-560, and forms van der Waals forces and dipole interactions with PDMS. Finally, it interpenetrates with the two polymer networks at the molecular scale to construct a true triple interpenetrating polymer network.

[0044] Cooling, demolding, and post-processing steps: After the temperature rise is complete, the oven heating device is turned off, and the material is allowed to cool naturally to room temperature at a rate of ≤1℃ / min to avoid the generation or accumulation of internal stress, which could lead to cracking of the GIS insulation components. Then, the mold is opened, and the epoxy composite insulation material with a triple interpenetrating network is removed. The epoxy composite insulation material with a triple interpenetrating network is then placed in a 120℃ oven and cured for 4 hours to further improve the crosslinking degree and performance stability, resulting in the final epoxy composite insulation material product with a triple interpenetrating network.

[0045] Comparative Example 1

[0046] To investigate the effect of introducing polyvinylidene fluoride nanocrystals to construct a triple interpenetrating network on the performance of epoxy composite insulation materials, this comparative example provides a method for preparing an epoxy composite insulation material with a binary interpenetrating network, including: raw material preparation steps, prepolymer preparation steps, mixing and degassing steps, polymerization steps, cooling demolding and post-treatment steps.

[0047] The steps for preparing raw materials include: According to the mass ratio of 100:20:85:0.7:0.6:0.6:2, bisphenol A type epoxy resin E-51, vinyl-terminated polydimethylsiloxane (PDMS), methylhexahydrophthalic anhydride (MeHHPA), 2,4,6-tris(dimethylaminomethyl)phenol (DMP-30), benzoyl peroxide (BPO), γ-glycidoxypropyltrimethoxysilane (KH-560) and fumed nano silica were weighed as raw materials for epoxy composite insulation material; The specifications of the raw materials for epoxy composite insulation materials include: bisphenol A type epoxy resin E-51 with an epoxy value of approximately 0.50 eq / 100g; vinyl-terminated polydimethylsiloxane (PDMS) with a vinyl content of approximately 0.8 mmol / g and a viscosity of approximately 3000 mPa. s; Methylhexahydrophthalic anhydride (MeHHPA) anhydride value is approximately 670 mg KOH / g; 2,4,6-tris(dimethylaminomethyl)phenol (DMP-30) purity ≥99%; Benzoyl peroxide (BPO) purity ≥99%; γ-glycidoxypropyltrimethoxysilane (KH-560) ≥98%; fumed silica specific surface area is 200±20 m² / g. 2 / g.

[0048] The preparation steps of the prepolymer include: Add weighed bisphenol A type epoxy resin E-51, along with weighed vinyl-terminated polydimethylsiloxane and benzoyl peroxide. Adjust the stirring speed to 600 r / min, raise the temperature to 80℃, and carry out a vinyl-terminated polydimethylsiloxane pre-crosslinking reaction for 1 hour to allow partial crosslinking of the vinyl-terminated polydimethylsiloxane and form a vinyl-terminated polydimethylsiloxane prepolymer. At this point, the system is a viscous liquid containing the PDMS prepolymer with no obvious phase separation.

[0049] The mixing and degassing steps include: Weigh out fumed nano-silica and γ-glycidyl etheroxypropyltrimethoxysilane and add them to a high-speed mixer. Set the temperature to 80℃ and the stirring speed to 1000 r / min and mix for 30 minutes. This allows the epoxy groups of γ-glycidyl etheroxypropyltrimethoxysilane to react with the hydroxyl groups on the surface of the nano-silica to form an organosilane layer. This yields silane coupling agent modified nano-silica, which improves the compatibility with epoxy resin. The temperature of the viscous liquid containing PDMS prepolymer was lowered to 60°C. Weighed amounts of methylhexahydrophthalic anhydride, 2,4,6-tris(dimethylaminomethyl)phenol, and silane coupling agent-modified nano-silica were added sequentially. The mixture was stirred at 800 r / min for 30 minutes to ensure uniform mixing of all components, resulting in a mixture. The mixture was then transferred to a vacuum degassing chamber and degassed at 60°C and -0.09 MPa for 20 minutes to remove air bubbles introduced during stirring until no air bubbles overflowed from the surface of the mixture, thus obtaining the epoxy composite insulation material precursor.

[0050] The aggregation steps include: The epoxy composite insulation material precursor is slowly poured into a mold preheated to 80°C. The mold is pre-coated with a release agent and then placed in a programmed temperature oven. First, it is kept at 80°C for 2 hours to allow the vinyl-terminated polydimethylsiloxane to complete the cross-linking reaction and form the PDMS second network. Then, it is kept at 100°C for 3 hours to allow the epoxy resin to undergo a pre-cross-linking reaction and complete the initial curing, forming the primary structure of the EP first network. Next, it is kept at 130°C for 2 hours to allow the epoxy resin to fully cure, forming an epoxy composite insulation material with a binary interpenetrating network of EP and PDMS. Finally, it is kept at 150°C for 1 hour for post-curing to eliminate internal stress.

[0051] The cooling, demolding, and post-processing steps include: After the heating process is complete, the oven heating device is turned off, and the material is allowed to cool naturally to room temperature at a rate of ≤1℃ / min to avoid the generation or accumulation of internal stress, which could lead to cracking of the GIS insulation components. Then, the mold is opened, and the epoxy composite insulation material with a binary interpenetrating network is removed. The epoxy composite insulation material with a binary interpenetrating network is then placed in a 120℃ oven and cured for 4 hours to further improve the degree of crosslinking and performance stability, resulting in the final epoxy composite insulation material product with a binary interpenetrating network.

[0052] Comparative Example 2

[0053] To investigate the effect of introducing a triple interpenetrating network constructed from polyvinylidene fluoride nanocrystals on the performance of epoxy composite insulation materials, this comparative example provides a method for preparing epoxy insulation materials, including: raw material preparation steps, mixing and degassing steps, polymerization steps, cooling demolding and post-treatment steps.

[0054] The steps for preparing raw materials include: According to the mass ratio of 100:85:0.7:0.6:2, bisphenol A type epoxy resin E-51, methyl hexahydrophthalic anhydride (MeHHPA), 2,4,6-tris(dimethylaminomethyl)phenol (DMP-30), γ-glycidyl etheroxypropyltrimethoxysilane (KH-560) and fumed nano silica were weighed as raw materials for epoxy insulation material. The specifications of the raw materials for epoxy insulation materials include: bisphenol A type epoxy resin E-51 with an epoxy value of approximately 0.50 eq / 100g; methyl hexahydrophthalic anhydride (MeHHPA) with an anhydride value of approximately 670 mg KOH / g; 2,4,6-tris(dimethylaminomethyl)phenol (DMP-30) with a purity ≥99%; γ-glycidyl etheroxypropyltrimethoxysilane (KH-560) with a purity ≥98%; and fumed silica with a specific surface area of ​​200±20 m². 2 / g.

[0055] The mixing and degassing steps include: Weigh out fumed nano-silica and γ-glycidyl etheroxypropyltrimethoxysilane and add them to a high-speed mixer. Set the temperature to 80℃ and the stirring speed to 1000 r / min and mix for 30 minutes. This allows the epoxy groups of γ-glycidyl etheroxypropyltrimethoxysilane to react with the hydroxyl groups on the surface of the nano-silica to form an organosilane layer. This yields silane coupling agent modified nano-silica, which improves the compatibility with epoxy resin. To a weighed bisphenol A type epoxy resin E-51, weighed methyl hexahydrophthalic anhydride, 2,4,6-tris(dimethylaminomethyl)phenol, and silane coupling agent modified nano-silica were added sequentially. The mixture was stirred at a speed of 800 r / min for 30 minutes to ensure that all components were uniformly mixed to obtain a mixture. The mixture was then transferred to a vacuum degassing chamber and degassed at 60℃ and -0.09 MPa for 20 minutes to remove air bubbles introduced during stirring until no air bubbles overflowed from the surface of the mixture, thus obtaining the epoxy insulation material precursor.

[0056] The aggregation steps include: The epoxy insulation material precursor is slowly poured into a mold preheated to 80°C. The mold is pre-coated with a release agent and then placed in a programmed temperature oven. First, it is kept at 80°C for 2 hours, and then at 100°C for 3 hours to allow the epoxy resin to undergo a pre-crosslinking reaction and complete the initial curing, forming the primary structure of the EP network. Next, it is kept at 130°C for 2 hours to allow the epoxy resin to fully cure, forming an epoxy insulation material with an EP network. Finally, it is kept at 150°C for 1 hour for post-curing to eliminate internal stress.

[0057] The cooling, demolding, and post-processing steps include: After the temperature rise is complete, turn off the oven heating device and allow it to cool naturally to room temperature at a rate of ≤1℃ / min to avoid internal stress generation or even accumulation, which could lead to cracking of GIS insulation components. Then, open the mold and remove the epoxy insulation material. Place the epoxy insulation material in a 120℃ oven and cure for 4 hours to further improve the crosslinking degree and performance stability, thus obtaining the final epoxy insulation material product.

[0058] Experimental Example 1

[0059] This experiment tested the performance of the epoxy composite insulation material with triple interpenetrating network provided in Example 1, the epoxy composite insulation material provided in Comparative Example 1, and the epoxy insulation material provided in Comparative Example 2. The performance tests included extreme low-temperature impact resistance, heat resistance, mechanical properties, and insulation properties. The test standards and results are shown in Table 1.

[0060] Table 1: Test Standards and Results

[0061] As shown in Table 1, the epoxy insulation material provided in Comparative Example 2 is a bisphenol A type epoxy resin insulation material. Because its molecular chains use rigid benzene rings and epoxy groups as repeating units, it has a high crosslinking density, strong intermolecular forces, and a small free volume. This means that although this type of epoxy insulation material possesses certain heat resistance, mechanical properties, and insulation properties, its low degree of rotational freedom at low temperatures prevents it from absorbing impact energy through deformation, leading to brittle fracture. This is especially true at extreme low temperatures such as -40°C and -60°C, where the impact strength drops significantly from 6.2 kJ / m² at room temperature. 2 Attenuation to 1.8 kJ / m 2 and 0.9kJ / m 2 The epoxy composite insulation material provided in Comparative Example 1 has a PDMS / EP binary interpenetrating network, but the solubility parameters of the vinyl-terminated polydimethylsiloxane and epoxy resin differ greatly. There is a lack of effective interaction between the two polymer networks, which easily leads to macroscopic phase separation, forming micron-sized polydimethylsiloxane phase regions. This results in a decrease in the modulus of the epoxy resin. At the same time, charge accumulates at the phase separation interface, leading to increased dielectric loss, decreased insulation breakdown field strength, and deterioration of heat resistance. The heat distortion temperature and glass transition temperature are low, making it difficult to meet the heat resistance requirements of electrical equipment during high-power operation. Furthermore, it cannot adapt to extreme cold regions such as high altitudes, and it will still experience brittle fracture at -60℃, with insufficient impact strength. Therefore, the overall performance of this type of epoxy composite insulation material with a binary interpenetrating polymer network is low.

[0062] Compared to the epoxy composite insulation material with a PDMS / EP binary interpenetrating network provided in Comparative Example 1, the epoxy composite insulation material provided in Example 1 has a triple interpenetrating network. The polyvinylidene fluoride (PVDF) nanocrystals in the triple interpenetrating network refine the micron-sized polydimethylsiloxane phase region. Furthermore, the rigidity of the PVDF nanocrystals is higher than that of PDMS, and they act as physical crosslinking points to effectively suppress the deformation of the PDMS network, thereby increasing the modulus of the insulation material. Simultaneously, refining the polydimethylsiloxane phase region eliminates macroscopic phase separation interfaces and reduces space charge accumulation. Combined with the PVDF nanocrystals... It possesses excellent electrical insulation properties, improving the insulation performance of insulating materials. Furthermore, the nanocrystals, acting as physical cross-linking points, increase the overall cross-linking density of the polymer network in the insulating material, thus enhancing its heat resistance. On the other hand, when the epoxy composite insulating material provided in Example 1 is subjected to external impact at extreme low temperatures such as -40°C and -60°C, microcracks initiate at stress concentration points. At this time, the flexible PDMS polymer network undergoes large deformation first, absorbing some of the impact energy and slowing the crack propagation rate. When the crack propagates to the PVDF nanocrystals, the PVDF nanocrystals will… Crack deflection occurs, changing the crack propagation path from a straight line to a broken line, thus lengthening the crack propagation path. Simultaneously, PVDF nanocrystals act as bridges, connecting the matrix on both sides of the crack and preventing further crack propagation. Furthermore, the plastic deformation of the PVDF nanocrystals absorbs a significant amount of impact energy. When the crack propagates to the epoxy resin network, the fracture toughness of the epoxy resin network is greatly enhanced due to the reinforcement effect of the triple interpenetrating network constructed by the PVDF nanocrystals, preventing further crack propagation and ultimately terminating the crack. This process, through the mechanisms of microcrack initiation, crack propagation, and crack termination, effectively addresses these challenges. The phase plays a role in improving the impact resistance under extreme low temperature conditions such as -40 and -60℃, and also has excellent heat resistance, mechanical properties and insulation properties; in addition, PVDF nanocrystals can capture charge carriers, reduce the bombardment of charge carriers on epoxy resin molecular chains, and improve the corona resistance of epoxy composite insulation materials. This allows electrical equipment such as GIS that uses the epoxy composite insulation material provided in Example 1 as an insulation component to have excellent long-term operational stability. Therefore, the epoxy composite insulation material provided in Example 1 is an epoxy-based insulation material with excellent comprehensive performance.

[0063] The above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application.

Claims

1. A method for preparing an epoxy composite insulating material with a triple interpenetrating network, characterized in that, Includes the following steps: Polyvinylidene fluoride (PVDF) was added to epoxy resin and stirred to dissolve it, resulting in a PVDF / EP mixed solution. Vinyl polydimethylsiloxane, free radical initiator, and silane coupling agent were added to a PVDF / EP mixed solution and stirred. Then, a vinyl polydimethylsiloxane pre-crosslinking reaction was carried out to obtain a mixed viscous liquid containing PDMS prepolymer. The epoxy resin curing agent, epoxy resin curing accelerator, and silane coupling agent modified nano-reinforcing filler were added to a mixed viscous liquid containing PDMS prepolymer, stirred and mixed, and then degassed under vacuum to obtain an epoxy composite insulation material precursor. The epoxy composite insulation material precursor was subjected to a vinyl polydimethylsiloxane crosslinking reaction, an epoxy resin pre-crosslinking reaction, an epoxy resin crosslinking reaction, and in-situ crystallization of polyvinylidene fluoride in sequence to obtain an epoxy composite insulation material with a triple interpenetrating network.

2. The method for preparing an epoxy composite insulating material with a triple interpenetrating network according to claim 1, characterized in that, The polyvinylidene fluoride has a number average molecular weight of 50,000 to 80,000 and a crystallinity of ≥50%.

3. The method for preparing an epoxy composite insulating material with a triple interpenetrating network according to claim 1, characterized in that, The stirring and dissolving temperature is 110~130℃, the stirring speed is 400~600r / min, and the time is 2~6h.

4. The method for preparing an epoxy composite insulating material with a triple interpenetrating network according to claim 1, characterized in that, The temperature of the pre-crosslinking reaction of the vinyl polydimethylsiloxane is 75~85℃, and the time is 0.5~1.5h.

5. The method for preparing an epoxy composite insulating material with a triple interpenetrating network according to claim 1, characterized in that, The mass ratio of the vinyl polydimethylsiloxane, the free radical initiator, and the silane coupling agent is 15~25:0.3~0.8:1~3; The mass ratio of the epoxy resin curing agent, epoxy resin curing accelerator, and silane coupling agent modified nano-reinforcing filler is 80~90:0.5~1:3~5.

6. The method for preparing an epoxy composite insulating material with a triple interpenetrating network according to claim 1, characterized in that, The crosslinking reaction of the vinyl polydimethylsiloxane is carried out at a temperature of 75-85°C for 1.5-3 hours.

7. The method for preparing an epoxy composite insulating material with a triple interpenetrating network according to claim 1, characterized in that, The process of sequentially subjecting the epoxy composite insulation material precursor to a vinyl polydimethylsiloxane crosslinking reaction, an epoxy resin pre-crosslinking reaction, an epoxy resin crosslinking reaction, and in-situ crystallization of polyvinylidene fluoride specifically involves: casting the epoxy composite insulation material precursor into an insulation mold, and sequentially performing a vinyl polydimethylsiloxane crosslinking reaction, the epoxy resin pre-crosslinking reaction, the epoxy resin crosslinking reaction, and in-situ crystallization of polyvinylidene fluoride.

8. A method for preparing an epoxy composite insulating material with a triple interpenetrating network, characterized in that, It is prepared by the preparation method according to any one of claims 1-7.

9. The application of the epoxy composite insulation material with a triple interpenetrating network as described in claim 8 in electrical equipment in cold regions.

10. An electrical device for use in high-altitude and cold regions, characterized in that, This includes the epoxy composite insulating material with a triple interpenetrating network as described in claim 8.

Images