Preparation method of microwave-cured aramid paper high-performance insulating composite material

Abstract

The invention relates to the technical field of composite materials, in particular to a preparation method of a microwave curing aramid paper high-performance insulating composite material. The high-performance insulating composite material prepared by the method comprises a modified insulating film framework layer, wherein an adhesive layer and a modified aramid paper layer are sequentially arranged on the two sides of the modified insulating film framework layer outwards; wherein the modified aramid paper is subjected to low-temperature plasma treatment and grafting modification with a silane coupling agent, and the modified insulating film framework layer is coated with slurry containing KH-550 modified nano silicon dioxide. The high-performance insulating composite material prepared by the invention not only has the high temperature resistance and puncture resistance of aramid paper, but also has the characteristics of high strength, large stiffness and good insulation of an insulating film, can be widely applied to motor stator insulation of a new energy automobile, and is an indispensable key material for the new energy automobile.

Description

Technical Field

[0001] This invention relates to the field of composite material technology, and in particular to a method for preparing a microwave-cured aramid paper high-performance insulating composite material. Background Technology

[0002] Nomex insulating paper possesses excellent mechanical strength, electrical properties, thermal stability, and chemical compatibility, making it widely used in Class F and Class C motors. With the advancement of science and technology, fields such as aerospace and high-speed trains are placing higher demands on motor capacity, and electrical equipment is trending towards miniaturization and larger capacity. This also places higher demands on the high-temperature resistance, strength, and insulation performance of insulating materials.

[0003] The core problem with existing aramid paper-insulating film skeleton composite systems lies in the weak interfacial bonding performance of the substrates. The surface of aramid paper has an inert benzene ring structure with extremely low content of active groups, and it only relies on physical adsorption to bond with adhesives, resulting in insufficient interlaminar shear strength. The surface of the insulating film skeleton is smooth and lacks an effective physical anchoring structure. Under long-term vibration, high temperature, or oil immersion environments, interfacial delamination is prone to occur, leading to a sharp drop in insulation performance. This interfacial defect directly limits the overall mechanical and insulation reliability of the composite material.

[0004] Traditional curing processes further exacerbate performance bottlenecks. Current mainstream thermosetting methods employ an "external heat, internal cold" heating mode, resulting in slow and uneven internal heating of the composite material. This necessitates increasing the curing temperature or extending the curing time to ensure adhesive cross-linking. However, high temperatures can easily lead to thermal deformation and embrittlement, as well as damage to the fiber structure, ultimately reducing the overall performance of the material. Microwave heating, on the other hand, is an internal heating method with advantages such as rapid heating speed, uniform temperature, and no hysteresis effect, thus accelerating the curing process. The effects of microwaves on chemical reactions are highly complex and cannot be described solely by microwave heating. In addition to thermal effects, microwaves also exhibit non-thermal effects not caused by temperature. Organic reactions under microwave influence alter reaction kinetics and lower the activation energy, representing a rapid, deep curing technology.

[0005] Furthermore, existing composite materials lack sufficient environmental adaptability. Under conditions such as motor oil immersion and high-temperature aging, the interface between the unmodified substrate and adhesive is susceptible to the effects of insulating oil penetration and high-temperature molecular chain degradation, resulting in problems such as delamination, discoloration, and decreased tensile strength retention, which cannot meet the requirements for long-term stable operation of equipment. Summary of the Invention

[0006] The purpose of this invention is to overcome the shortcomings of the existing technology and propose a method for preparing microwave-cured aramid paper high-performance insulating composite material.

[0007] To achieve the above objectives, this invention provides a method for preparing microwave-cured aramid paper high-performance insulating composite material, comprising the following steps:

[0008] (1) Place the aramid paper in a low-temperature plasma treatment instrument, introduce high-purity argon gas, set the power to 80-120W, and the treatment time to 3-5min. Then add it to the ethanol / water mixed solution, add γ-glycidyl etheroxypropyltrimethoxysilane under shaking, adjust the pH to 4-5 with dilute hydrochloric acid, raise the temperature to 60-70℃, and react for 3-5h. After the reaction is completed, take out the aramid paper, wash it, and dry it to obtain the modified aramid paper.

[0009] (2) Add KH-550 modified nano silica to epoxy resin E-51, add ethyl acetate, stir under ultrasonication for 1-2 hours to obtain nano slurry, coat the nano slurry evenly on the surface of the insulating film skeleton layer, control the wet film thickness to make the dry film thickness 5-10μm, place it in a 120-130℃ forced air oven for 20-40min to pre-cur it to obtain the modified insulating film skeleton layer.

[0010] (3) Following the adhesive coating process, an adhesive layer and a modified aramid paper layer are sequentially applied to both sides of the modified insulating film skeleton layer outwards, and a high-performance insulating material is obtained after hot pressing.

[0011] (4) The high-performance insulating material after hot pressing is pre-dried in a drying tunnel air circulation system at 105℃ for 3-10 minutes, rolled into a roll with a radius of 50-100cm by a film rolling machine, and then baked in a microwave oven at 45-70℃ for 3-5 hours.

[0012] (5) Heat the microwave oven to 100-140℃ and continue curing for 1-5 hours. After curing, let it cool naturally to room temperature, cut and package the finished product to obtain a microwave-cured aramid paper high-performance insulating composite material.

[0013] Preferably, the aramid paper in (1) is composed of meta-aramid short-cut fibers and meta-aramid precipitated fibers or para-aramid short-cut fibers and para-aramid precipitated fibers.

[0014] More preferably, the aramid paper in (1) is composed of meta-aramid short-cut fibers and meta-aramid precipitated fibers.

[0015] Preferably, in (1), the aramid paper and γ-glycidyl etheroxypropyltrimethoxysilane are in a weight ratio of 1:0.1-0.2.

[0016] Preferably, the purity of the high-purity argon gas in (1) is ≥99.99%, and the flow rate is 10-15 ml / min.

[0017] Preferably, the volume ratio of ethanol to water in the ethanol / water mixed solution in (1) is 9:1.

[0018] Preferably, the concentration of dilute hydrochloric acid in (1) is 3 mol / L.

[0019] Preferably, in (2), the KH-550 modified nano silica, epoxy resin E-51 and ethyl acetate are in a weight ratio of 0.05-0.1:1:0.2-0.3.

[0020] Preferably, the insulating film skeleton layer in (2) is one of PET film, PI film, PP film, and PPS film.

[0021] More preferably, the insulating film skeleton layer in (2) is a PI film.

[0022] Preferably, the adhesive in the adhesive layer of (3) is prepared according to the preparation method described in patent CN118879250B. This adhesive has a long activation period, good insulation performance, and is especially suitable for continuous operation.

[0023] Preferably, the thickness of the adhesive layer after curing in (3) is 3-8 μm.

[0024] More preferably, the thickness of the adhesive layer after curing in (3) is 5 μm.

[0025] Preferably, the hot pressing conditions in (3) are a temperature of 80-100℃, a pressure of 0.3-0.6MPa, and a time of 2-5min.

[0026] Preferably, in step (4), the film rolling machine rolls the film into a roll with a radius of 50cm and then bakes it in a microwave oven at 60°C for 5 hours.

[0027] Preferably, the output power P of the microwave oven in (4) is 10-100kW, and the microwave output frequency F is 2450±50MHz.

[0028] More preferably, in (4), the microwave oven has an output power P of 50kW and a microwave output frequency F of 2450MHz.

[0029] Preferably, in step (5), the microwave oven is heated to 120°C and cured for another 3 hours.

[0030] Furthermore, the present invention also provides a microwave-cured aramid paper high-performance insulating composite material, which is prepared by the above-described method.

[0031] The beneficial effects of this invention are:

[0032] 1. This invention introduces a large number of active epoxy groups into the surface of aramid paper through low-temperature plasma treatment and silane coupling agent grafting modification. Simultaneously, the insulating film skeleton is modified with a nano-silica coating to construct a roughened and dielectrically modulated interface. The synergistic effect of these two substrate modification processes significantly enhances the chemical crosslinking and physical anchoring effects with specialized adhesives, effectively solving the problems of weak interfacial bonding and easy peeling in traditional composite systems. This ensures that the composite material maintains excellent interlayer integrity even under long-term vibration and high-temperature environments.

[0033] 2. The microwave curing technology used in this invention utilizes the "internal heating" characteristic of microwaves to simultaneously raise the temperature of the interior and surface of the composite material, enabling rapid curing at a relatively low temperature of 100-140℃. Compared with traditional thermal curing, this significantly shortens the time and reduces energy consumption. Simultaneously, the low-temperature curing process avoids thermal damage to the aramid paper fibers and insulating film skeleton caused by high temperatures, maximizing the preservation of the original mechanical and high-temperature resistance properties of the substrate, and resolving the contradiction of "low efficiency - substrate damage" in traditional curing.

[0034] 3. The synergistic effect of substrate modification and microwave uniform curing in this invention endows the composite material with excellent high-temperature resistance and oil resistance. The modified aramid paper and insulating film skeleton can inhibit molecular chain degradation at high temperatures, and the special adhesive forms a dense adhesive film after microwave uniform cross-linking, which can block the penetration of insulating oil and avoid interface erosion. This composite material can withstand high temperatures below 220℃ and oil immersion environments at 120℃ for a long time without delamination, peeling or other deterioration, meeting the environmental resistance requirements for long-term stable operation of high-end electrical equipment.

[0035] 4. In this invention, the dielectric regulation effect of the nano-coating on the modified insulating film skeleton significantly improves the overall uniformity of the dielectric constant of the composite material, avoids local electric field concentration during microwave curing and long-term use, and greatly improves the breakdown voltage. At the same time, the strong bonding force between the modified substrate and the adhesive, combined with a reasonable hot pressing process, ensures that the composite material has excellent tensile strength, achieving a performance balance between high insulation and high mechanical strength, making it suitable for scenarios with stringent requirements for the comprehensive performance of insulating materials, such as new energy vehicle motors and aerospace equipment. Detailed Implementation

[0036] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to specific embodiments.

[0037] Example 1: A specific preparation method of a microwave-cured aramid paper high-performance insulating composite material, comprising the following steps:

[0038] (1) Place the new material Minshida meta-aramid paper YT510 in a low-temperature plasma treatment instrument, introduce high-purity argon gas with a purity ≥99.99%, flow rate 10ml / min, set power 80W, treatment time 3min, then add ethanol / water mixed solution (volume ratio of ethanol to water is 9:1), add γ-glycidyl etheroxypropyltrimethoxysilane with a mass of 10% of meta-aramid paper under shaking, adjust pH to 4-5 with 3mol / L dilute hydrochloric acid, heat to 60℃, react for 3h, remove aramid paper after the reaction, wash and dry to obtain modified aramid paper;

[0039] (2) Add 50g of KH-550 modified nano silica to 1kg of epoxy resin E-51, add 200g of ethyl acetate, stir under ultrasonication for 1h to obtain nano slurry, uniformly coat the nano slurry onto the surface of KAPTON PI film with a thickness of 0.05mm, control the wet film thickness to make the dry film thickness 5μm, place it in a 120℃ forced air oven for pre-curing for 20min to obtain the modified insulating film skeleton layer;

[0040] (3) According to the adhesive coating process, an adhesive layer (the adhesive is prepared according to the preparation method described in patent CN118879250B, and the thickness of the adhesive layer after curing is 5μm) and a modified aramid paper layer are sequentially applied to both sides of the modified insulating film skeleton layer outwards. After hot pressing at a temperature of 80℃, a pressure of 0.3MPa, and a time of 2min, a high-performance insulating material is obtained.

[0041] (4) The high-performance insulating material after hot pressing is pre-dried in the drying tunnel air circulation system at 105℃ for 3 minutes, rolled into a roll with a radius of 50cm by a film rolling machine, and transferred into a microwave oven at 60℃. The output power of the microwave oven is set to 50kW and the microwave output frequency is set to 2450MHz. The oven is baked for 5 hours.

[0042] (5) Heat the microwave oven to 120°C and continue curing for 3 hours. After curing, let it cool naturally to room temperature, cut and package the finished product to obtain a microwave-cured aramid paper high-performance insulating composite material.

[0043] Example 2: A specific preparation method of a microwave-cured aramid paper high-performance insulating composite material, comprising the following steps:

[0044] (1) Place the new material Minshida meta-aramid paper YT510 in a low-temperature plasma treatment instrument, introduce high-purity argon gas with a purity ≥99.99%, flow rate 12ml / min, power set 100W, treatment time 4min, then add ethanol / water mixed solution (ethanol and water volume ratio 9:1), add γ-glycidyl etheroxypropyltrimethoxysilane with a mass of 15% of meta-aramid paper under shaking, adjust pH to 4-5 with 3mol / L dilute hydrochloric acid, heat to 65℃, react for 4h, remove aramid paper after the reaction, wash and dry to obtain modified aramid paper;

[0045] (2) Add 80g of KH-550 modified nano silica to 1kg of epoxy resin E-51, add 250g of ethyl acetate, stir under ultrasonication for 1.5h to obtain nano slurry, uniformly coat the nano slurry onto the surface of KAPTON PI film with a thickness of 0.05mm, control the wet film thickness to make the dry film thickness 8μm, place it in a 125℃ forced air oven for pre-curing for 30min to obtain the modified insulating film skeleton layer;

[0046] (3) Following the adhesive coating process, adhesive layers (the adhesive is prepared according to the preparation method described in patent CN118879250B, and the thickness of the adhesive layer after curing is 5μm) and modified aramid paper layers are sequentially applied to both sides of the modified insulating film skeleton layer outwards. After hot pressing at a temperature of 90℃, a pressure of 0.45MPa, and a time of 3min, a high-performance insulating material is obtained.

[0047] (4) The high-performance insulating material after hot pressing is pre-dried in the drying tunnel air circulation system at 105℃ for 5 minutes, rolled into a roll with a radius of 50cm by a film rolling machine, and transferred into a microwave oven at 60℃. The output power of the microwave oven is set to 50kW and the microwave output frequency is set to 2450MHz. The oven is then baked for 5 hours.

[0048] (5) Heat the microwave oven to 120°C and continue curing for 3 hours. After curing, let it cool naturally to room temperature, cut and package the finished product to obtain a microwave-cured aramid paper high-performance insulating composite material.

[0049] Example 3: A specific preparation method of a microwave-cured aramid paper high-performance insulating composite material, comprising the following steps:

[0050] (1) Place the new material Minshida meta-aramid paper YT510 in a low-temperature plasma treatment instrument, introduce high-purity argon gas with a purity ≥99.99%, flow rate 15ml / min, set power 120W, treatment time 5min, then add ethanol / water mixed solution (volume ratio of ethanol to water is 9:1), add γ-glycidyl etheroxypropyltrimethoxysilane with a mass of 20% of meta-aramid paper under shaking, adjust pH to 4-5 with 3mol / L dilute hydrochloric acid, heat to 70℃, react for 5h, remove aramid paper after the reaction, wash and dry to obtain modified aramid paper;

[0051] (2) Add 100g of KH-550 modified nano silica to 1kg of epoxy resin E-51, add 300g of ethyl acetate, stir under ultrasonication for 2h to obtain nano slurry, uniformly coat the nano slurry onto the surface of KAPTON PI film with a thickness of 0.05mm, control the wet film thickness to make the dry film thickness 10μm, place it in a 130℃ forced air oven for pre-curing for 40min to obtain the modified insulating film skeleton layer;

[0052] (3) Following the adhesive coating process, an adhesive layer (the adhesive is prepared according to the preparation method described in patent CN118879250B, and the thickness of the adhesive layer after curing is 5μm) and a modified aramid paper layer are sequentially applied to both sides of the modified insulating film skeleton layer outwards. After hot pressing at a temperature of 100℃, a pressure of 0.6MPa, and a time of 5min, a high-performance insulating material is obtained.

[0053] (4) The high-performance insulating material after hot pressing is pre-dried in the drying tunnel air circulation system at 105℃ for 10 minutes, rolled into a roll with a radius of 50cm by a film rolling machine, and transferred into a microwave oven at 60℃. The output power of the microwave oven is set to 50kW and the microwave output frequency is set to 2450MHz. The oven is baked for 5 hours.

[0054] (5) Heat the microwave oven to 120°C and continue curing for 3 hours. After curing, let it cool naturally to room temperature, cut and package the finished product to obtain a microwave-cured aramid paper high-performance insulating composite material.

[0055] Comparative Example 1: The difference between Comparative Example 1 and Example 2 is that step (1) is omitted, and the modified aramid paper layer in step (3) is replaced with an aramid paper layer composed of the new material Minstar meta-aramid paper yt510.

[0056] Comparative Example 2: The difference between Comparative Example 2 and Example 2 is that step (2) is omitted, and the modified insulating film skeleton layer in step (3) is replaced with an insulating film skeleton layer composed of a 0.05 mm thick PI film of KAPTON.

[0057] Comparative Example 3: The difference between Comparative Example 3 and Example 2 is that steps (1) and (2) are omitted, the modified aramid paper layer in step (3) is replaced with an aramid paper layer made of new material Minstar meta-aramid paper yt510, and the modified insulating film skeleton layer is replaced with an insulating film skeleton layer made of 0.05mm thick PI film of KAPTON.

[0058] Comparative Example 4: The difference between Comparative Example 4 and Example 2 is that the microwave oven is replaced with a regular oven.

[0059] Comparative Example 5: The difference between Comparative Example 4 and Example 2 is that the microwave oven in step (5) is heated to 180°C.

[0060] Comparative Example 6: The difference between Comparative Example 6 and Example 2 is that the microwave oven in step (5) is heated to 120°C and cured for 10 hours.

[0061] Performance testing:

[0062] The microwave-cured aramid paper high-performance insulating composite materials prepared in Examples 1-3 and Comparative Examples 1-5 were subjected to performance testing.

[0063] 1. Tensile strength: The test was conducted according to the requirements of GB / T 5591.2-2017, with a composite material thickness of 0.228 mm and an adhesive basis weight of 265.93 g / m³. 3 The prepared specimens were installed in the upper and lower clamping devices of the universal testing machine. The clamping distance was adjusted to 200 mm to ensure that the specimens did not shift or wrinkle during clamping. Then, the tensile speed of the testing machine was set to 100 mm / min. After starting the equipment, the testing machine applied axial tensile force to the specimens at a constant speed and recorded the tensile force change data in real time until the specimens broke. The maximum tensile force value at the moment of breakage was taken. Combined with the width and thickness parameters of the specimens, the tensile strength of each specimen was calculated according to the tensile strength calculation formula (tensile strength = maximum tensile force / (specimen width × specimen thickness)). The experimental results are shown in Table 1.

[0064] 2. Heat Resistance Test: Referring to GB / T 11021-2007, each group of samples was placed in a constant temperature aging chamber. Aging conditions were set for the two key grades commonly used in electrical insulation materials: H grade (rated long-term temperature resistance 180℃) and C grade (rated long-term temperature resistance 220℃). First, the aging chamber was heated to 180℃, maintaining a temperature fluctuation of ≤±2℃, and aging was continued for 1000 hours. After aging, the chamber was closed, and the samples were allowed to cool naturally to room temperature. After removal, the samples were first observed for signs of aging damage such as brittleness, cracking, delamination, and discoloration. Then, the tensile strength after aging was measured, and the tensile strength retention rate was calculated. If the sample showed no abnormalities in appearance after aging at 180℃ and the tensile strength retention rate was ≥80% (GB / T...), the test was considered successful. According to the core performance requirements of 11021-2017 for H-grade materials, the materials in this group are judged to have reached at least H grade. On this basis, unaged samples from the same group are placed in the aging chamber again, heated to 220℃, and aged for 1000h. The appearance inspection and tensile strength test are repeated. If the appearance is still normal and the tensile strength retention rate is ≥80%, the materials in this group are judged to have reached C grade. The experimental results are shown in Table 1.

[0065] 3. Oil resistance test: Referring to GB / T 17948.7-2016, prepare insulating oil that meets the standard requirements. Pour the insulating oil into a constant temperature oil bath, heat and stabilize the oil bath temperature to 120℃, and control the temperature fluctuation within ±1℃. Select composite material samples of the same size, and then completely immerse the samples in the constant temperature insulating oil to ensure that no air bubbles adhere to the samples and no parts are exposed. Record the soaking start time at the same time. After soaking for 100 hours, remove the samples with tweezers and immediately use clean lint-free filter paper to gently absorb the excess insulating oil on the sample surface to avoid damaging the sample surface structure. After 10 minutes, carefully observe the surface condition of the samples and check for phenomena such as peeling, wrinkling, discoloration, and swelling. The experimental results are shown in Table 1.

[0066] 4. Breakdown Voltage Test: Referring to GB / T 5591.2-2017, the test environment was controlled under standard atmospheric conditions of 23±2℃ and 50±5% relative humidity. The sample was laid flat on the lower electrode (circular metal electrode with a diameter conforming to the standard) of the withstand voltage tester, ensuring that the sample and electrode were completely in contact without wrinkles or impurities. Then, the upper electrode was lowered so that the upper and lower electrodes were parallel and applied uniformly to the sample surface, and the electrode pressure met the standard requirements. The withstand voltage tester was started, and a 50Hz AC voltage was applied to the electrode at a uniform voltage increase rate of 2kV / s. The voltage change was monitored in real time until the sample broke down (manifested as a sudden increase in current and a sudden drop in voltage). The voltage value at this time was recorded as the withstand breakdown voltage of the sample, in kV. Each experimental group was tested in parallel 5 times. After removing outliers, the average value was taken as the final withstand breakdown voltage result. The experimental results are shown in Table 1.

[0067] Table 1 Performance Test Results

[0068]

[0069]

[0070] Performance Analysis:

[0071] As can be seen from the data in Table 1, the composite materials prepared by the preparation method of the present invention in Examples 1-4 have good adhesion, high electrical stability, and excellent long-term high temperature resistance and oil resistance. Among them, Example 2 has the best overall performance.

[0072] A comparison of the data from Example 2 and Comparative Example 1 shows that if both are cured at 120°C for 3 hours using microwave curing, and only the aramid paper modification step is omitted, the tensile strength, oil resistance, and breakdown voltage all decrease significantly. Although the heat resistance grade remains C, the stability is reduced. This is because the unmodified aramid paper has few surface active groups and only relies on physical adsorption to bond with the CN118879250B adhesive. The interlayer shear strength is low, and local interface peeling is likely to occur during oil immersion. Under the action of an electric field, the breakdown voltage is easily reduced due to interface defects.

[0073] A comparison of the data from Example 2 and Comparative Example 2 shows that if both are cured at 120°C for 3 hours using microwave curing, and only the modification step of the insulating film skeleton layer is omitted, the tensile strength is lower than that of Example 2, slight peeling occurs in the oil resistance test, and the breakdown voltage is also lower. This is because the surface of the unmodified PI film is smooth and has no nano-SiO2 coating, resulting in weak interfacial bonding with the adhesive. At the same time, the large difference in dielectric constant between the PI film and the adhesive during microwave heating leads to uneven local heating, reduced crosslinking uniformity of the adhesive, and affected interlayer integrity.

[0074] A comparison of the data from Example 2 and Comparative Example 3 shows that if both are cured at 120℃ for 3 hours using microwave curing, and the modification of aramid paper and insulating film skeleton layer is omitted, the tensile strength is reduced to the lowest level, the heat resistance grade drops from C to H, wrinkling and extensive peeling occur in the oil resistance test, and the breakdown voltage is also at a low level. This is because neither substrate is modified, and the interfacial bonding force with the adhesive is extremely poor. During high-temperature aging, complete interlayer peeling is likely to occur. Furthermore, the molecular chains of the PI film without nano-coating protection are easily degraded at high temperatures, resulting in a significant decline in overall heat resistance and environmental resistance.

[0075] The data comparison between Example 2 and Comparative Example 4 shows that if the curing temperature is the same (120℃) and the curing time is 3 hours, but the microwave oven is replaced with a regular oven, the tensile strength is significantly lower than that of Example 2, the heat resistance grade drops from C to H, the oil resistance test shows wrinkling and extensive peeling, and the breakdown voltage is also lower. This is because the regular oven uses an "external heat and internal cold" heating method, which results in slow internal heating of the composite material, uneven cross-linking of the adhesive, and a large number of residual bubbles between layers. Furthermore, the outer substrate is prone to aging due to prolonged high temperature, leading to a decline in overall performance.

[0076] A comparison of the data from Example 2 and Comparative Example 5 shows that if the curing equipment is replaced with a regular oven, and the curing temperature is increased from 120°C to 180°C while the curing time is maintained at 3 hours, the tensile strength is slightly higher than that of Comparative Example 4 but still lower than that of Example 2. The heat resistance grade rises back to Grade C, the oil resistance test becomes smooth but with a small amount of peeling, and the breakdown voltage is still lower than that of Example 2. This is because although the high temperature of 180°C can promote the cross-linking reaction of the adhesive in the regular oven and restore the heat resistance to some extent, the high temperature will cause the PI film to deform and become brittle, and the interfacial adhesion with the adhesive will decrease. There is still a small amount of interfacial peeling problem when immersed in oil.

[0077] A comparison of the data from Example 2 and Comparative Example 6 shows that if both are cured by microwave at the same temperature of 120°C, but the curing time is extended from 3 hours to 10 hours, the tensile strength is lower than that of Example 2, the breakdown voltage is also lower, the heat resistance grade is still C, and the oil resistance test remains smooth without peeling. This is because excessively long microwave curing time will cause the adhesive to be over-crosslinked, generating internal stress and destroying the original bonding state between layers. At the same time, prolonged heating at 120°C will slightly affect the fiber structure integrity of the modified aramid paper, resulting in a decrease in tensile strength and breakdown voltage. However, since it does not exceed the heat resistance range of the substrate, the heat resistance and oil resistance performance do not show significant deterioration.

[0078] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A method for the preparation of a microwave-cured aramid paper high performance insulation composite, characterized in that, It comprises the following steps: (1) Put aramid paper into a low-temperature plasma treatment instrument, introduce high-purity argon, set the power to 80-120 W, and treat for 3-5 min, then add an ethanol / water mixed solution, add γ-glycidoxypropyltrimethoxysilane under oscillation, adjust the pH to 4-5 with dilute hydrochloric acid, heat to 60-70℃, and react for 3-5 h, then take out the aramid paper, wash and dry to obtain modified aramid paper; (2) Add KH-550 modified nano-silicon dioxide to epoxy resin E-51, add ethyl acetate, stir under ultrasonic for 1-2 h to obtain nano slurry, uniformly coat the nano slurry on the surface of the insulating film skeleton layer, control the wet film thickness to make the dry film thickness 5-10 μm, and place in a 120-130℃ air oven for pre-curing for 20-40 min to obtain a modified insulating film skeleton layer; (3) According to the gluing process, successively set adhesive layers and modified aramid paper layers on both sides of the modified insulating film skeleton layer, and hot-press to obtain a high-performance insulating material; (4) Pre-bake the hot-pressed high-performance insulating material in a 105℃ oven air circulation system for 3-10 min, roll into a roll with a radius of 50-100 cm by a film rolling machine, and transfer into a 45-70℃ microwave oven for baking for 3-5 h; (5) Continue to heat the microwave oven to 100-140℃ for 1-5 h for curing, naturally cool to room temperature, cut and package the product to obtain a microwave-cured aramid paper high-performance insulating composite material.

2. The method for preparing microwave-cured aramid paper high-performance insulating composite material according to claim 1, characterized in that, The aramid paper in (1) is composed of meta-aramid short-cut fibers and meta-aramid fibrids or para-aramid short-cut fibers and para-aramid fibrids.

3. The method for preparing microwave-cured aramid paper high-performance insulating composite material according to claim 1, characterized in that, The aramid paper in (1) and γ-glycidoxypropyltrimethoxysilane are in a weight ratio of 1:0.1-0.

2.

4. The method for preparing microwave-cured aramid paper high-performance insulating composite material according to claim 1, characterized in that, The high-purity argon in (1) has a purity of ≥99.99%, a flow rate of 10-15 ml / min, and the ethanol / water mixed solution has a volume ratio of ethanol to water of 9:1 and a dilute hydrochloric acid concentration of 3 mol / L.

5. The method for preparing microwave-cured aramid paper high-performance insulating composite material according to claim 1, characterized in that, The KH-550 modified nano-silicon dioxide, epoxy resin E-51 and ethyl acetate in (2) are in a weight ratio of 0.05-0.1:1:0.2-0.

3.

6. The method of claim 1, wherein the microwave cured aramid paper high performance insulation composite is prepared by the steps of: The insulating film skeleton layer in (2) is one of PET film, PI film, PP film and PPS film.

7. The method for preparing microwave-cured aramid paper high-performance insulating composite material according to claim 1, characterized in that, The adhesive in the adhesive layer in (3) is prepared according to the preparation method described in patent CN118879250B, and the thickness of the adhesive layer after curing is 3-8 μm.

8. The method for preparing microwave-cured aramid paper high-performance insulating composite material according to claim 1, characterized in that, The hot-pressing conditions in (3) are a temperature of 80-100℃, a pressure of 0.3-0.6 MPa, and a time of 2-5 min.

9. The method for preparing microwave-cured aramid paper high-performance insulating composite material according to claim 1, characterized in that, The microwave oven in (4) has an output power P of 10-100 kW and a microwave output frequency F of 2450±50 MHz.

10. A microwave-cured aramid paper high-performance insulating composite material prepared by the preparation method of any one of claims 1-9.

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