High temperature resistant polyimide generator stator end insulation

Abstract

The present application relates to the technical field of generator stator end insulation, and specifically discloses a high-temperature-resistant polyimide generator stator end insulation piece. The insulation piece comprises, by weight fraction, 55-75 parts of polyimide prepolymer, 5-15 parts of diamine monomer containing a benzimidazole structure, 20-35 parts of inorganic-organic composite filler, 2-6 parts of high-temperature-resistant curing agent, and 1-3 parts of interface coupling agent; the inorganic-organic composite filler is made of flaky boron nitride, surface-modified silicon dioxide nanoparticles and short-cut aramid fiber in a mass ratio of (2-4):(3-5):(1-3). The insulation piece of the present application can still maintain excellent insulation performance and mechanical strength at a high temperature of 280 DEG C, and the volume resistivity can reach 10 14 Ω·cm or above, the dielectric strength is ≥20 kV / mm, and the tensile strength is ≥120 MPa, so that the long-term insulation requirement of the end of the stator of a large generator under extreme working conditions can be met, and the operation reliability and service life of the generator can be significantly improved.

Description

Technical Field

[0001] This invention relates to the technical field of generator stator end insulation components, specifically to a high-temperature resistant polyimide generator stator end insulation component. Background Technology

[0002] With the rapid development of the power industry, large generators are evolving towards higher voltage, larger capacity, and higher parameters, leading to increasingly harsh operating environments. As the core component of the generator, the reliability of its insulation system directly determines the generator's service life and operational safety. The stator ends, being the areas with the highest concentration of electric, thermal, and mechanical stresses, place extremely high demands on the insulation materials. They must not only possess excellent electrical insulation performance but also withstand long-term high-temperature operating environments (typically above 150℃, and in extreme conditions above 250℃), mechanical vibration, and multiple stresses from thermal cycling.

[0003] Currently, commonly used insulation materials for generator stators mainly include epoxy resin-based composites, mica tape, and traditional polyimide materials. However, these materials have significant shortcomings in high-temperature performance: epoxy resin-based materials undergo a glass transition above 180℃, leading to a significant decrease in mechanical strength and insulation performance; while traditional polyimide materials have a certain degree of high-temperature resistance, their dielectric properties gradually deteriorate when used for extended periods above 200℃, with volume resistivity decreasing by more than an order of magnitude, reducing the partial discharge initiation voltage, and easily causing insulation failures. Furthermore, existing insulation component manufacturing processes often employ single-temperature curing, leading to stress concentration within the material and susceptibility to cracking under thermal cycling conditions, severely impacting the reliability of the insulation system.

[0004] In the prior art, CN109245373A discloses a motor stator insulation structure that uses interphase insulating paper and guide slots for insulation, but it suffers from complex assembly and easy loosening. CN217545708U proposes an interphase insulating component with folded edges, which improves the fixing effect, but the insulation performance at high temperatures is still not ideal. In terms of material modification, existing technologies mostly use single filler modification or simple blending methods, failing to achieve synergistic effects between inorganic and organic fillers. Furthermore, the curing process lacks gradient control, making it difficult for the material properties to meet the stringent requirements of the stator ends of large generators. Therefore, developing a stator end insulation component that combines excellent high-temperature resistance, electrical insulation, and mechanical properties with a stable and reliable manufacturing process is of great significance for improving the operational reliability and extending the service life of large generators. Summary of the Invention

[0005] The purpose of this invention is to provide a high-temperature resistant polyimide generator stator end insulation component to solve the problems mentioned in the background art.

[0006] To achieve the above objectives, the present invention provides a high-temperature resistant polyimide generator stator end insulation component, comprising, by weight, 55-75 parts of polyimide prepolymer, 5-15 parts of diamine monomer containing benzimidazole structure, 20-35 parts of inorganic-organic composite filler, 2-6 parts of high-temperature resistant curing agent, and 1-3 parts of interface coupling agent. The inorganic-organic composite filler is made of sheet-like boron nitride, surface-modified silica nanoparticles and chopped aramid fibers in a mass ratio of (2-4):(3-5):(1-3).

[0007] Preferably, the curing agent is a mixture of 2,5-bis(4-aminophenyl)-1,3,4-oxadiazole and tris(2-carboxyethyl)isocyanurate, with a molar ratio of (1-3):(1-2).

[0008] Preferably, the interface coupling agent is γ-glycidoxypropyltrimethoxysilane or N-β-(aminoethyl)-γ-aminopropyltrimethoxysilane.

[0009] Preferably, the diamine monomer containing the benzimidazole structure is 2-(4-aminophenyl)-5-aminobenzimidazole. The benzimidazole ring in this monomer molecule forms a conjugated structure with the amino group, which can form a strong interaction with the imide group in the polyimide prepolymer, significantly improving the rigidity and thermal stability of the molecular chain.

[0010] Preferably, the surface-modified silica nanoparticles are silica modified with silane coupling agent KH-550, with a particle size of 20-50 nm. The amino groups in KH-550 can react with the hydroxyl groups on the surface of silica, while the organic functional groups at the other end can interact with the polyimide molecular chains, improving the interfacial compatibility between the inorganic particles and the organic matrix.

[0011] Preferably, the average particle size of the plate-like boron nitride is 10-20 μm, and the thickness is 0.5-2 μm. The plate-like structure of boron nitride exhibits excellent thermal conductivity and insulation properties, enabling the formation of thermally conductive pathways within the material while simultaneously improving the material's breakdown field strength.

[0012] Preferably, the length of the chopped aramid fibers is 50-200 μm. Aramid fibers are characterized by high strength, high modulus, and high temperature resistance, which can enhance the tensile and fatigue resistance of materials and reduce stress concentration during the curing process.

[0013] Preferably, the polyimide prepolymer is prepared by reacting pyromellitic dianhydride and 4,4'-diaminodiphenyl ether in an organic solvent, with a solid content of 15-25%. This prepolymer has good film-forming properties and reactivity, providing a fundamental guarantee for the performance of the final material.

[0014] Preferably, the organic solvent is N-methylpyrrolidone, N,N-dimethylacetamide, or a mixture thereof.

[0015] Preferably, the organic solvent is a mixture of N-methylpyrrolidone and N,N-dimethylacetamide in a mass ratio of 1:1. This mixed solvent has good solubility for the polyimide prepolymer and each monomer, ensuring the homogeneity of the reaction system.

[0016] The present invention also provides a method for preparing the above-mentioned high-temperature resistant polyimide generator stator end insulation component, comprising the following steps: (1) Raw material pretreatment: The boron nitride flakes were cleaned three times with anhydrous ethanol in an acoustic cleaner for 30 minutes each time, and then dried in a vacuum drying oven at 80°C for 2 hours; the chopped aramid fibers were dried at 120°C for 4 hours to remove moisture. (2) Preparation of composite filler: Weigh the sheet boron nitride, surface modified silica nanoparticles and short-cut aramid fibers according to the mass ratio, add them to a high-speed mixer, and mix for 15 min at a speed of 3000 r / min to obtain inorganic-organic composite filler; (3) Preparation of prepolymer: Under nitrogen protection, pyromellitic dianhydride and 4,4'-diaminodiphenyl ether are added to an organic solvent in an equimolar ratio and stirred at 25°C for 4 hours to obtain a polyimide prepolymer (polyamic acid solution) with a solid content of 15-25%. (4) Preparation of mixed slurry: Weigh the polyimide prepolymer according to the weight parts, add it to the reaction vessel, add the diamine monomer containing benzimidazole structure, the composite filler prepared in step (2), and the interface coupling agent in sequence. Stir at 50°C for 2 hours under nitrogen protection, then add the high temperature resistant curing agent and continue stirring for 1 hour to obtain a uniform mixed slurry. (5) Molding and curing: Pour the mixed slurry prepared in step (4) into a mold preheated to 80°C and cure it according to the “in-situ-gradient” curing process: pre-curing at 80-120°C and 5-15MPa pressure for 0.5-2h, then heating to 150-180°C and maintaining pressure for 1-3h, then heating to 200-240°C and maintaining pressure for 2-4h, and finally heating to 250-280°C and maintaining pressure for 1-2h; after curing, cool to room temperature with the furnace and demold to obtain the high-temperature resistant polyimide generator stator end insulation part.

[0017] The superior performance of the high-temperature resistant polyimide generator stator end insulation component of this invention stems from the combination of multi-component synergistic effects and advanced manufacturing processes. Its mechanism of action is as follows: At the molecular structure level, the diamine monomer containing the benzimidazole structure undergoes a copolymerization reaction with the polyimide prepolymer. The rigid benzimidazole heterocycle is introduced into the molecular chain, enhancing intermolecular forces through conjugation and hydrogen bonding, thus significantly improving the thermal and chemical stability of the material. Simultaneously, the strong polarity of the benzimidazole group can trap free charges and inhibit charge migration, thereby improving insulation performance at high temperatures.

[0018] At the microstructural level, the inorganic-organic composite filler forms a three-dimensional network structure: lamellar boron nitride is uniformly dispersed in the matrix through interfacial coupling agents, overlapping to form thermally conductive pathways, significantly improving the material's thermal conductivity and promoting rapid heat dissipation; surface-modified silica nanoparticles fill the matrix voids due to their small size effect and form a chemical bond with the matrix through silane coupling agents, reducing interfacial defects. Simultaneously, the nanoparticles can capture space charge, increasing the material's breakdown field strength; chopped aramid fibers form a mechanical support network within the material, absorbing impact energy through fiber pull-out and bridging, significantly improving the material's mechanical strength and fatigue resistance. The three fillers are blended in a specific ratio, achieving a synergistic improvement in thermal conductivity, insulation, and mechanical properties. At the curing reaction level, the composite curing agents play a synergistic role: 2,5-bis(4-aminophenyl)-1,3,4-oxadiazole provides high crosslinking density and thermal stability, while tris(2-carboxyethyl)isocyanurate introduces certain flexible segments to avoid increased brittleness caused by excessive crosslinking. The "in-situ-gradient" molding curing process gradually increases temperature and pressure, allowing the solvent to evaporate slowly and the reaction to proceed uniformly. Prepolymerization and preliminary crosslinking are first completed at a lower temperature, followed by full curing and imidization at a higher temperature. Finally, internal stress is eliminated in the post-curing stage, forming a uniform and dense structure, effectively avoiding stress cracking and bubble defects caused by sudden temperature changes in traditional curing processes. The addition of interfacial coupling agents is key to achieving good bonding between organic and inorganic phases. The two ends of the molecules react chemically with the surface of the inorganic filler and the organic matrix, respectively, to form a strong chemical bond, eliminate interfacial impedance, ensure the continuity of the thermal conductivity path, improve the mechanical strength at the interface, and avoid interfacial separation under stress. The beneficial effects of this invention are mainly reflected in the following aspects: (1) Excellent high temperature resistance: The heat distortion temperature exceeds 280℃, and it can be used for a long time at temperatures above 250℃, meeting the operating requirements of large generators under extreme conditions; (2) Excellent electrical insulation performance: It maintains a volume resistivity of ≥10 even at a high temperature of 250℃. 14 Ω·cm, dielectric strength ≥20kV / mm, high partial discharge initiation voltage, effectively preventing insulation breakdown accidents; (3) Excellent mechanical properties: tensile strength ≥120MPa, impact strength ≥18kJ / m², capable of withstanding mechanical vibration and thermal cycle stress during generator operation; (4) Good heat dissipation performance: The thermal conductivity reaches 0.85W / (m·K) or higher, which helps to dissipate heat at the stator end and avoid local overheating; (5) Ultra-long service life: The thermal aging life at 280℃ exceeds 1250h, which is far higher than that of traditional insulation materials, significantly reducing the maintenance cost of generators; (6) Stable preparation process: The "in-situ gradient" curing process has good repeatability, high product dimensional accuracy, and is suitable for mass production. Detailed Implementation

[0019] The following provides a detailed description of specific embodiments of the present invention. It should be understood that the specific embodiments described herein are for illustrative and explanatory purposes only and are not intended to limit the scope of the invention.

[0020] It should be noted that all reagents and raw materials used in this invention are commercially available, and the reagents are of analytical grade.

[0021] Example 1 A high-temperature resistant polyimide generator stator end insulation component, comprising the following components by weight: 55 parts of polyimide prepolymer (20% solid content); 5 parts of 2-(4-aminophenyl)-5-aminobenzimidazole; Twenty parts of inorganic-organic composite filler were prepared by combining sheet-like boron nitride (average particle size 10 μm, thickness 0.5 μm), KH-550 modified silica (average particle size 20 nm), and chopped aramid fibers (length 50 μm) in a mass ratio of 2:3:1. Two parts of high-temperature resistant curing agent are a mixture of 2,5-bis(4-aminophenyl)-1,3,4-oxadiazole and tris(2-carboxyethyl) isocyanurate in a molar ratio of 1:1; 1 part of γ-glycidyl etheroxypropyltrimethoxysilane; Preparation method: (1) Raw material pretreatment: The boron nitride flakes were cleaned three times with anhydrous ethanol in an acoustic cleaner for 30 minutes each time, and then dried in a vacuum drying oven at 80°C for 2 hours; the chopped aramid fibers were dried at 120°C for 4 hours to remove moisture. (2) Preparation of composite filler: Weigh out sheet boron nitride, KH-550 modified silica and chopped aramid fiber according to the mass ratio, add them to a high-speed mixer, mix at 3000 r / min for 15 min to obtain inorganic-organic composite filler; (3) Preparation of polyimide prepolymer: Under nitrogen protection, pyromellitic dianhydride and 4,4'-diaminodiphenyl ether were added in equimolar ratio to a mixed organic solvent composed of N-methylpyrrolidone and N,N-dimethylacetamide in a mass ratio of 1:1. The mixture was stirred at 25°C for 4 hours to obtain a polyimide prepolymer with a solid content of 20%. (4) Preparation of mixed slurry: Weigh the polyimide prepolymer by weight and add it to the reactor. Then add 2-(4-aminophenyl)-5-aminobenzimidazole, the composite filler prepared in step (2), and γ-glycidyl etheroxypropyltrimethoxysilane in sequence. Stir at 50°C for 2 hours under nitrogen protection. Then add the mixture of 2,5-bis(4-aminophenyl)-1,3,4-oxadiazole and tris(2-carboxyethyl)isocyanurate and continue stirring for 1 hour to obtain a uniform mixed slurry. (5) Molding and curing: Pour the mixed slurry prepared in step (4) into a mold preheated to 80°C and cure it according to the “in-situ-gradient” curing process: pre-curing at 80°C and 15MPa pressure for 2 hours, then heating to 150°C and maintaining pressure for 3 hours, then heating to 200°C and maintaining pressure for 4 hours, and finally heating to 250°C and maintaining pressure for 2 hours; after curing, cool to room temperature with the furnace and demold to obtain the high-temperature resistant polyimide generator stator end insulation part.

[0022] Example 2 A high-temperature resistant polyimide generator stator end insulation component, comprising the following components by weight: 65 parts of polyimide prepolymer (25% solid content); 10 parts of 2-(4-aminophenyl)-5-aminobenzimidazole; 28 parts of inorganic-organic composite filler were prepared by lamellar boron nitride (average particle size 15μm, thickness 1μm), KH-550 modified silica (average particle size 30nm) and chopped aramid fiber (length 120μm) in a mass ratio of 3:4:2. Four parts of high-temperature resistant curing agent are a mixture of 2,5-bis(4-aminophenyl)-1,3,4-oxadiazole and tris(2-carboxyethyl) isocyanurate in a molar ratio of 2:1.5; 2 parts of γ-glycidyl etheroxypropyltrimethoxysilane; Preparation method: (1) Raw material pretreatment: The boron nitride flakes were cleaned three times with anhydrous ethanol in an acoustic cleaner for 30 minutes each time, and then dried in a vacuum drying oven at 80°C for 2 hours; the chopped aramid fibers were dried at 120°C for 4 hours to remove moisture. (2) Preparation of composite filler: Weigh out sheet boron nitride, KH-550 modified silica and chopped aramid fiber according to the mass ratio, add them to a high-speed mixer, mix at 3000 r / min for 15 min to obtain inorganic-organic composite filler; (3) Preparation of polyimide prepolymer: Under nitrogen protection, pyromellitic dianhydride and 4,4'-diaminodiphenyl ether were added in equimolar ratio to a mixed organic solvent composed of N-methylpyrrolidone and N,N-dimethylacetamide in a mass ratio of 1:1. The mixture was stirred at 25°C for 4 hours to obtain a polyimide prepolymer with a solid content of 25%. (4) Preparation of mixed slurry: Weigh the polyimide prepolymer by weight and add it to the reactor. Then add 2-(4-aminophenyl)-5-aminobenzimidazole, the composite filler prepared in step (2), and γ-glycidyl etheroxypropyltrimethoxysilane in sequence. Stir at 50°C for 2 hours under nitrogen protection. Then add the mixture of 2,5-bis(4-aminophenyl)-1,3,4-oxadiazole and tris(2-carboxyethyl)isocyanurate and continue stirring for 1 hour to obtain a uniform mixed slurry. (5) Molding and curing: Pour the mixed slurry prepared in step (4) into a mold preheated to 100°C and cure it according to the “in-situ-gradient” curing process: pre-curing at 100°C and 10MPa pressure for 1 hour, then heating to 165°C and maintaining pressure for 2 hours, then heating to 220°C and maintaining pressure for 3 hours, and finally heating to 265°C and maintaining pressure for 1.5 hours; after curing, cool to room temperature with the furnace and demold to obtain the high-temperature resistant polyimide generator stator end insulation part.

[0023] Example 3 A high-temperature resistant polyimide generator stator end insulation component, comprising the following components by weight: 75 parts of polyimide prepolymer (15% solid content); 15 parts of 2-(4-aminophenyl)-5-aminobenzimidazole; 35 parts of inorganic-organic composite filler are made of sheet-like boron nitride (average particle size 20μm, thickness 2μm), KH-550 modified silica (average particle size 50nm) and short-cut aramid fiber (length 200μm) in a mass ratio of 4:5:3. Six parts of high-temperature resistant curing agent are a mixture of 2,5-bis(4-aminophenyl)-1,3,4-oxadiazole and tris(2-carboxyethyl) isocyanurate in a molar ratio of 3:2; 3 parts of N-β(aminoethyl)-γ-aminopropyltrimethoxysilane; Preparation method: (1) Raw material pretreatment: The boron nitride flakes were cleaned three times with anhydrous ethanol in an acoustic cleaner for 30 minutes each time, and then dried in a vacuum drying oven at 80°C for 2 hours; the chopped aramid fibers were dried at 120°C for 4 hours to remove moisture. (2) Preparation of composite filler: Weigh out sheet boron nitride, KH-550 modified silica and chopped aramid fiber according to the mass ratio, add them to a high-speed mixer, mix at 3000 r / min for 15 min to obtain inorganic-organic composite filler; (3) Preparation of polyimide prepolymer: Under nitrogen protection, pyromellitic dianhydride and 4,4'-diaminodiphenyl ether were added to N,N-dimethylacetamide organic solvent in an equimolar ratio and stirred at 25°C for 4 hours to obtain a polyimide prepolymer with a solid content of 15%. (4) Preparation of mixed slurry: Weigh the polyimide prepolymer by weight and add it to the reactor. Then add 2-(4-aminophenyl)-5-aminobenzimidazole, the composite filler prepared in step (2), and γ-glycidyl etheroxypropyltrimethoxysilane in sequence. Stir at 50°C for 2 hours under nitrogen protection. Then add the mixture of 2,5-bis(4-aminophenyl)-1,3,4-oxadiazole and tris(2-carboxyethyl)isocyanurate and continue stirring for 1 hour to obtain a uniform mixed slurry. (5) Molding and curing: Pour the mixed slurry prepared in step (4) into a mold preheated to 120°C and cure it according to the “in-situ-gradient” curing process: pre-curing at 120°C and 5MPa pressure for 0.5h, then heating to 180°C and maintaining pressure for 1h, then heating to 240°C and maintaining pressure for 2h, and finally heating to 280°C and maintaining pressure for 1h; after curing, cool to room temperature with the furnace and demold to obtain the high-temperature resistant polyimide generator stator end insulation part.

[0024] Example 4 A high-temperature resistant polyimide generator stator end insulation component, comprising the following components by weight: 60 parts of polyimide prepolymer (22% solid content); 8 parts of 2-(4-aminophenyl)-5-aminobenzimidazole; 25 parts of inorganic-organic composite filler were prepared by lamellar boron nitride (average particle size 12μm, thickness 1μm), KH-550 modified silica (average particle size 40nm) and short-cut aramid fiber (length 100μm) in a mass ratio of 2.5:3.5:1.5. Three parts of high-temperature resistant curing agent are a mixture of 2,5-bis(4-aminophenyl)-1,3,4-oxadiazole and tris(2-carboxyethyl) isocyanurate in a molar ratio of 1.5:1; 1.5 parts of N-β(aminoethyl)-γ-aminopropyltrimethoxysilane; Preparation method: (1) Raw material pretreatment: The boron nitride flakes were cleaned three times with anhydrous ethanol in an acoustic cleaner for 30 minutes each time, and then dried in a vacuum drying oven at 80°C for 2 hours; the chopped aramid fibers were dried at 120°C for 4 hours to remove moisture. (2) Preparation of composite filler: Weigh out sheet boron nitride, KH-550 modified silica and chopped aramid fiber according to the mass ratio, add them to a high-speed mixer, mix at 3000 r / min for 15 min to obtain inorganic-organic composite filler; (3) Preparation of polyimide prepolymer: Under nitrogen protection, pyromellitic dianhydride and 4,4'-diaminodiphenyl ether were added to N-methylpyrrolidone organic solvent in an equimolar ratio and stirred at 25°C for 4 hours to obtain a polyimide prepolymer with a solid content of 22%. (4) Preparation of mixed slurry: Weigh the polyimide prepolymer by weight and add it to the reactor. Then add 2-(4-aminophenyl)-5-aminobenzimidazole, the composite filler prepared in step (2), and γ-glycidyl etheroxypropyltrimethoxysilane in sequence. Stir at 50°C for 2 hours under nitrogen protection. Then add the mixture of 2,5-bis(4-aminophenyl)-1,3,4-oxadiazole and tris(2-carboxyethyl)isocyanurate and continue stirring for 1 hour to obtain a uniform mixed slurry. (5) Molding and curing: Pour the mixed slurry prepared in step (4) into a mold preheated to 90°C and cure it according to the “in-situ-gradient” curing process: pre-curing at 90°C and 12MPa pressure for 1.5h, then heating to 170°C and maintaining pressure for 2.5h, then heating to 210°C and maintaining pressure for 3.5h, and finally heating to 270°C and maintaining pressure for 1.2h; after curing, cool to room temperature with the furnace and demold to obtain the high-temperature resistant polyimide generator stator end insulation part.

[0025] Comparative Example 1 A high-temperature resistant polyimide generator stator end insulation component differs from Example 2 in that it does not contain a diamine monomer with a benzimidazole structure, while other components and preparation methods are the same as in Example 2.

[0026] Comparative Example 2 A high-temperature resistant polyimide generator stator end insulation component differs from Example 2 in that the curing agent is a single 2,5-bis(4-aminophenyl)-1,3,4-oxadiazole, while other components and preparation methods are the same as in Example 2.

[0027] Comparative Example 3 A high-temperature resistant polyimide generator stator end insulation component differs from Example 2 in that: the inorganic-organic composite filler design is cancelled, and only a single piece of boron nitride is used as the filler. Other components are the same as in Example 2. The preparation method step (1) does not include "drying the short-cut aramid fiber at 120°C for 4 hours", and step (2) is omitted. Other steps and parameters are the same as in Example 2.

[0028] Comparative Example 4 A high-temperature resistant polyimide generator stator end insulation component, which differs from Example 2 in that step (5) adopts a single temperature curing process: curing at 200℃ and 10MPa pressure for 6 hours, while other components and preparation steps are the same as in Example 2.

[0029] The insulation components of Examples 1-4 and Comparative Examples 1-4 were subjected to performance tests, and the test standards and methods are as follows: (1) Heat distortion temperature: The test was conducted in accordance with GB / T 1634.2-2021 "Determination of load distortion temperature of plastics - Part 2: Plastics, hard rubber and long fiber reinforced composites", with a load of 1.82 MPa; (2) Volume resistivity: Tested according to GB / T 1410-2006 "Test methods for volume resistivity and surface resistivity of solid insulating materials" at a test temperature of 250℃; (3) Dielectric strength: The test shall be conducted in accordance with GB / T 1408.1-2016 "Test methods for electrical strength of insulating materials - Part 1: Test at power frequency", using AC voltage and a step-up rate of 1kV / s; (4) Tensile strength: Tested in accordance with GB / T 1040.1-2018 "Determination of tensile properties of plastics - Part 1: General rules", with a tensile rate of 5 mm / min; (5) Impact strength: The impact strength was tested in accordance with GB / T 1043.1-2023 "Determination of impact properties of simply supported beams of plastics - Part 1: Non-instrumental impact test", using unnotched impact of simply supported beams; (6) Thermal conductivity: The thermal conductivity was tested according to GB / T 10297-2015 "Determination of thermal conductivity of non-metallic solid materials by hot wire method" using the hot wire method; (7) Partial discharge initiation voltage: Tested according to Appendix C of NB / T 31049-2021 "Insulation system of wind turbine generator set - Part 1: Requirements" at a test temperature of 250℃; (8) Thermal aging life: Accelerated aging test was conducted in a 280℃ thermal aging chamber according to GB / T 11026.1-2021 "Heat resistance of insulating materials - Part 1: Aging procedure and evaluation of test results". Volume resistivity was tested periodically. When the volume resistivity dropped to 1 / 10 of the initial value, the aging time was recorded. The test results are shown in Table 1.

[0030] Table 1 Performance Test Results

[0031] As can be seen from the test results in Table 1, the insulating components of Examples 1-4 of the present invention are superior to those of Comparative Examples 1-4 in all performance indicators. The specific analysis is as follows: (1) Thermal performance: The heat distortion temperatures of Examples 1-4 are all above 285℃, which is much higher than the 240℃ of Comparative Example 1. This is because the benzimidazole diamine monomer introduced in this invention forms a more rigid molecular chain structure with the polyimide, which improves the heat resistance of the material. Comparative Example 1, which did not add this monomer, showed a significant decrease in heat distortion temperature, verifying the key role of the benzimidazole group in improving thermal stability.

[0032] (2) Electrical insulation performance: The volume resistivity (250°C) of all embodiments remained at 10 Ω·cm. 14 The resistivity is above Ω·cm, the dielectric strength exceeds 20 kV / mm, and the partial discharge initiation voltage (250℃) is above 6.5 kV. In contrast, the volume resistivity of Comparative Example 1 is only 5.6 × 10⁻⁶. 12 The dielectric strength is 16.7 kV / mm, and the partial discharge initiation voltage is 4.1 kV, showing a significant performance difference. Comparative Example 3 has a volume resistivity of only 6.3 × 10⁻⁶ Ω·cm. 13 The dielectric strength is 16.2 kV / mm and the partial discharge initiation voltage is 3.9 kV. This is because the introduction of the benzimidazole group reduces the polarity of the molecular chain. At the same time, although a single plate boron nitride can form a partial thermal conduction path, it lacks the "space charge trapping effect" of KH-550 modified silica nanoparticles. Nanoscale silica can fill the matrix voids and inhibit charge migration, while the micron-sized plate boron nitride cannot cover microscopic defects, resulting in easy charge accumulation and a significantly increased risk of breakdown at high temperatures.

[0033] (3) Mechanical properties: The tensile strength of all examples exceeded 120 MPa, and the impact strength was above 18.5 kJ / m². Comparative Example 1, lacking the reinforcing effect of benzimidazole monomer, had a tensile strength of only 96 MPa, and Comparative Example 3 had a tensile strength of only 88 MPa and an impact strength of only 10.2 kJ / m². 2 A single sheet of boron nitride can only provide limited rigid support and lacks the "fiber bridging and pull-out effect" of chopped aramid fibers. Aramid fibers can absorb impact energy through mechanical meshing and interfacial bonding, while sheet boron nitride has no fibrous structure and cannot resist tensile stress and vibration impact, which directly leads to increased material brittleness and deterioration of fatigue resistance.

[0034] (4) Thermal conductivity: The thermal conductivity of the examples is between 0.85 and 0.92 W / (m·K), which is significantly higher than that of Comparative Example 1 (0.52 W / (m·K). This is due to the fact that the benzimidazole monomer improves the compatibility of the matrix-boron nitride interface, so that the plate-like boron nitride is uniformly dispersed and forms a continuous thermal conduction path, avoiding thermal failure caused by filler agglomeration.

[0035] (5) Thermal aging life: The thermal aging life of all examples at 280℃ exceeded 1250h, with Example 2 reaching 1580h, which is much higher than the 650h of Comparative Example 1 and the 720h of Comparative Example 3. This is attributed to the excellent thermal stability and anti-aging properties of the material of the present invention, as well as the uniform structure formed by the gradient curing process, which reduces the generation of defects during the aging process. In the composite filler, the chemical bonding between the modified silica and the matrix (through KH-550 coupling agent) can inhibit the degradation of molecular chains at high temperatures, while the interfacial bonding force between the single sheet-like boron nitride and the matrix is ​​weak, and interfacial peeling is prone to occur after long-term thermal aging, which accelerates the degradation of material performance.

[0036] (6) Effect of different curing processes: Comparative Example 4, which uses a single-temperature curing process, has lower performance in all aspects than Example 2, which uses an "in-situ-gradient" curing process, especially in volume resistivity and impact strength. This indicates that gradient temperature curing helps reduce internal stress and bubbles in the material, improves structural density, and thus improves overall performance.

[0037] (7) Effect of curing agent type: Comparative Example 2 uses a single curing agent, and its performance is lower than that of Example 2 which uses a composite curing agent. This shows that the synergistic effect of 2,5-bis(4-aminophenyl)-1,3,4-oxadiazole and tris(2-carboxyethyl)isocyanurate can optimize the crosslinking structure and take into account both the rigidity and toughness of the material.

[0038] In summary, this invention, through reasonable formula design and advanced manufacturing process, successfully produces generator stator end insulation components that combine high heat resistance, excellent insulation performance, and good mechanical properties. These components can meet the long-term operating requirements of large generators under extreme conditions and have significant engineering application value and market prospects.

[0039] The preferred embodiments of the present invention have been described in detail above. However, the present invention is not limited to the specific details of the above embodiments. Within the scope of the technical concept of the present invention, various simple modifications can be made to the technical solutions of the present invention, and these simple modifications all fall within the protection scope of the present invention. Furthermore, it should be noted that the various specific technical features described in the above embodiments can be combined in any suitable manner without contradiction. To avoid unnecessary repetition, the present invention will not further describe the various possible combinations.

[0040] Furthermore, various different embodiments of the present invention can be combined in any way, as long as they do not violate the spirit of the present invention, they should also be regarded as the content disclosed by the present invention.

Claims

1. A high-temperature resistant polyimide generator stator end insulation component, characterized in that, By weight, it includes: 55-75 parts of polyimide prepolymer, 5-15 parts of diamine monomer containing benzimidazole structure, 20-35 parts of inorganic-organic composite filler, 2-6 parts of high temperature resistant curing agent and 1-3 parts of interface coupling agent. The inorganic-organic composite filler is made of sheet-like boron nitride, surface-modified silica nanoparticles and chopped aramid fibers in a mass ratio of (2-4):(3-5):(1-3); The high-temperature resistant curing agent is a mixture of 2,5-bis(4-aminophenyl)-1,3,4-oxadiazole and tris(2-carboxyethyl) isocyanurate in a molar ratio of (1-3):(1-2); The diamine monomer containing the benzimidazole structure is 2-(4-aminophenyl)-5-aminobenzimidazole; The polyimide prepolymer is prepared by reacting pyromellitic dianhydride and 4,4'-diaminodiphenyl ether in an organic solvent, with a solid content of 15-25%. The method for preparing the high-temperature resistant polyimide generator stator end insulation component includes the following steps: (1) Raw material pretreatment: The sheet boron nitride and the chopped aramid fibers are dried separately; (2) Preparation of composite filler: Weigh the dried sheet boron nitride, surface-modified silica nanoparticles and dried short-cut aramid fibers according to the mass ratio, add them to a high-speed mixer and mix to obtain inorganic-organic composite filler; (3) Preparation of prepolymer: Under nitrogen protection, pyromellitic dianhydride and 4,4'-diaminodiphenyl ether are added to an organic solvent in an equimolar ratio and stirred to react. After the reaction is completed, a polyimide prepolymer with a solid content of 15-25% is obtained. (4) Preparation of mixed slurry: Weigh the polyimide prepolymer by weight and add it to the reaction vessel. Then add the diamine monomer containing benzimidazole structure, the composite filler prepared in step (2), and the interface coupling agent in sequence. Under nitrogen protection, add the high temperature resistant curing agent, mix and stir to obtain a uniform mixed slurry. (5) Molding and curing: Pour the mixed slurry prepared in step (4) into the mold and cure it according to the in-situ gradient curing process: The in-situ gradient curing process includes: pre-curing at 80-120℃ and 5-15MPa pressure for 0.5-2 hours, then heating to 150-180℃ and maintaining pressure for a first curing of 1-3 hours, then heating to 200-240℃ and maintaining pressure for a second curing of 2-4 hours, and finally heating to 250-280℃ and maintaining pressure for a curing of 1-2 hours; after curing, cooling to room temperature in the furnace and demolding to obtain the high-temperature resistant polyimide generator stator end insulation component.

2. The high-temperature resistant polyimide generator stator end insulation component according to claim 1, characterized in that, The interface coupling agent is γ-glycidoxypropyltrimethoxysilane or N-β-(aminoethyl)-γ-aminopropyltrimethoxysilane.

3. The high-temperature resistant polyimide generator stator end insulation component according to claim 1, characterized in that, The surface-modified silica nanoparticles are silica modified with silane coupling agent KH-550, with a particle size of 20-50 nm.

4. The high-temperature resistant polyimide generator stator end insulation component according to claim 3, characterized in that: The average particle size of the plate-like boron nitride is 10-20 μm, and the thickness is 0.5-2 μm.

5. The high-temperature resistant polyimide generator stator end insulation component according to claim 4, characterized in that, The length of the chopped aramid fibers is 50-200 μm.

6. The high-temperature resistant polyimide generator stator end insulation component according to claim 1, characterized in that, The organic solvent is N-methylpyrrolidone, N,N-dimethylacetamide, or a mixture thereof.

7. The high-temperature resistant polyimide generator stator end insulation component according to claim 6, characterized in that, The organic solvent is a mixture of N-methylpyrrolidone and N,N-dimethylacetamide in a mass ratio of 1:1.

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