Epoxy resin curing agent, insulating epoxy resin and preparation method therefor
By introducing curing agents and alumina fillers with specific structures into epoxy resin, the problem of decreased electrical performance of epoxy resin insulation materials at high temperatures has been solved, achieving insulation effects with high thermal stability and high electrical performance.
Patent Information
- Authority / Receiving Office
- WO · WO
- Patent Type
- Applications
- Current Assignee / Owner
- XI AN JIAOTONG UNIV
- Filing Date
- 2025-02-25
- Publication Date
- 2026-07-09
Smart Images
Figure CN2025078998_09072026_PF_FP_ABST
Abstract
Description
An epoxy resin curing agent, an insulating epoxy resin, and a method for preparing the same. Technical Field
[0001] This application pertains to a curing agent structure, specifically relating to an epoxy resin curing agent, an insulating epoxy resin, and a method for preparing the same. Background Technology
[0002] With the increasing focus on carbon emissions and the rapid development of the renewable energy industry, large-scale energy transmission and utilization are becoming increasingly important. High-voltage direct current (HVDC) transmission technology is of great significance for the development of large-scale energy transmission and utilization. Currently, thermosetting polymer-based insulation materials, especially epoxy resin-based materials, are widely used as electrical insulation materials in DC gas-insulated transmission lines and switches (GILs, Gas Insulated Transmission Lines / GIS), bushings, solid-state transformers (SSTs), rectifiers, and other power equipment and electronic devices due to their excellent mechanical properties, corrosion resistance, and electrical properties.
[0003] However, with increasing voltage levels and power densities, the resistive losses in conductors and heat dissipation within the insulation will lead to an increase in the operating temperature of the insulating material. This necessitates that the insulating material maintain excellent electrical properties at high temperatures. Furthermore, under direct current, the electric field exhibits a resistive distribution, and the resistivity of epoxy resin is extremely sensitive to temperature changes. Under high temperature and large electric field conditions, it is prone to electric field distortion and reduced insulation strength. Traditional anhydride-cured epoxy resins have a glass transition temperature of only around 120°C. When the ambient temperature approaches this temperature, their electrical and mechanical properties deteriorate significantly. Therefore, developing epoxy resin insulating materials that retain excellent electrical properties at high temperatures is of great significance for future energy networks.
[0004] Currently, the main methods for improving the electrical properties of polymer materials at high temperatures include nanodoping and molecular design. Although nanodoping technology has great potential, it cannot guarantee the uniform dispersion of nanoparticles within the material. Excessive doping concentration can lead to particle agglomeration, hindering its practical application. Furthermore, molecular design is also an effective method for optimizing high-performance polymers; however, this method is still in the experimental stage in designing epoxy resins with high thermal stability and high electrical properties. Current methods mainly focus on directly improving the electrical insulation properties of polymers. While introducing deep traps can increase the energy required to excite electrons at high temperatures, the dominant factor in the degradation of epoxy resin performance is still the molecular thermal motion caused by high temperatures. Therefore, finding a method to improve the thermal stability and electrical properties of epoxy resin insulation materials is urgently needed. Technical issues
[0005] This application addresses the technical problems of current methods for improving the electrical properties of polymer materials at high temperatures, such as easy agglomeration of nanoparticles, uneven dispersion, and unclear improvement in electrical properties at high temperatures. It provides an epoxy resin curing agent, an insulating epoxy resin, and a method for preparing the same. Technical solutions
[0006] To achieve the above objectives, this application adopts the following technical solution:
[0007] In a first aspect, this application provides an epoxy resin curing agent, comprising:
[0008] At least two benzene ring structures or at least two non-coplanar rigid alicyclic structures;
[0009] Two adjacent benzene ring structures or non-coplanar rigid alicyclic structures are connected by methylene groups to form an integral structure;
[0010] The overall structure has an amino functional group on each side, and an electron-withdrawing substituent group or several sterically hindered substituent groups are arranged adjacent to the amino functional group.
[0011] Furthermore, the electron-withdrawing substituent is -Cl;
[0012] The sterically hindered substituent group is -CH3 or -C2H5.
[0013] Furthermore, the epoxy resin curing agent structure includes at least two non-coplanar rigid alicyclic structures;
[0014] The non-coplanar rigid alicyclic structure is C6H12.
[0015] Furthermore, the number of sterically hindered substituents is 1-2.
[0016] Secondly, this application proposes a method for preparing an insulating epoxy resin, comprising:
[0017] The above-mentioned epoxy resin curing agent is dispersed in bisphenol A epoxy resin to obtain a first mixture;
[0018] Alumina filler was added to the liquid mixture to obtain a second mixture;
[0019] The second mixture is heated to degas it under vacuum, and then poured into a mold for further degassing.
[0020] After curing and cooling, the insulating epoxy resin product is obtained.
[0021] Furthermore, the weight ratio of epoxy resin curing agent, bisphenol A epoxy resin and alumina filler is (10~35):(15~45):(35~65).
[0022] Furthermore, the curing conditions are as follows:
[0023] Raise the temperature to 120~140 ℃ and hold for 60~120 min; then raise the temperature to 160~180 ℃ and hold for 100~150 min; finally raise the temperature to 180~220 ℃ and hold for 60~120 min.
[0024] Further, the method for dispersing the epoxy resin curing agent in bisphenol A epoxy resin includes:
[0025] The epoxy resin curing agent is melted at 100~120 ℃, and then stirred and dispersed in bisphenol A epoxy resin at 100~120 ℃.
[0026] Furthermore, the second mixture is heated to a temperature of 100~140 °C to achieve vacuum degassing of the second mixture.
[0027] Thirdly, this application proposes an insulating epoxy resin, which is prepared using the above-mentioned insulating epoxy resin preparation method. Beneficial effects
[0028] Compared with the prior art, this application has the following beneficial effects:
[0029] This application proposes an epoxy resin curing agent that improves the thermal stability and glass transition temperature of epoxy resin by introducing a diaryldiamine curing agent, utilizing the rigidity and planar structure of the benzene ring. This allows the epoxy resin to maintain its original properties at higher temperatures. The electrical properties of the epoxy resin are enhanced by grafting different groups to the ortho positions of the amino functional groups. Specifically, by grafting high electron-withdrawing groups to the ortho positions of the amino functional groups, the π-electron density on the benzene ring is reduced, thereby decreasing the electrical conductivity of the epoxy resin. Alternatively, sterically hindered groups such as methane or ethane are grafted to the ortho positions of the amino functional groups, utilizing their steric hindrance effect and distorted conformation in the epoxy resin chain to block charge transfer between different molecules caused by the benzene ring conjugation effect, thus improving the electrical properties of the epoxy resin. Furthermore, a non-planar rigid alicyclic structure with saturated electrons is used instead of the benzene ring, utilizing its weak conjugation effect to reduce the concentration of nonlocal electrons, thereby improving the electrical properties of the epoxy resin. By modifying epoxy resin curing agents using the above methods, insulating epoxy resins with both high thermal stability and high electrical properties can be prepared, thereby solving the problem of insulation failure in high temperature gradient and large electric field environments.
[0030] This application also proposes a method for preparing insulating epoxy resin. By introducing benzene rings, the thermal stability of the prepared epoxy resin is enhanced. By introducing high electron-withdrawing groups and large steric hindrance groups, or by using non-coplanar alicyclic structures with saturated electrons to replace benzene rings, the volume resistivity of the epoxy resin at both room temperature and high temperature is significantly improved, and it can maintain good electrical performance in high temperature gradient and large electric field environments.
[0031] This application also proposes an insulating epoxy resin prepared using the above-described method, which possesses all the advantages of the epoxy resin curing agent and the insulating epoxy resin preparation method. Attached Figure Description
[0032] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of this application and should not be regarded as a limitation of the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.
[0033] Figure 1 shows the Fourier transform infrared spectra of bisphenol A epoxy resin (DGEBA), and the insulating epoxy resins obtained in Examples 1-6 of this application and the comparative examples.
[0034] Figure 2 shows the glass transition temperatures of the insulating epoxy resins obtained in Examples 1-6 and the comparative examples of this application.
[0035] Figure 3 shows the DC breakdown strength and shape parameters of the insulating epoxy resins obtained in Examples 1-6 and the comparative examples of this application at room temperature.
[0036] Figure 4 shows the volume resistivity results of the insulating epoxy resins obtained in Examples 1-6 and the comparative examples of this application at 80 °C. Embodiments of the present invention
[0037] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. The components of the embodiments of this application described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.
[0038] Therefore, the following detailed description of the embodiments of this application provided in the accompanying drawings is not intended to limit the scope of the claimed application, but merely to illustrate selected embodiments of the application. All other embodiments obtained by those skilled in the art based on the embodiments of this application without inventive effort are within the scope of protection of this application.
[0039] It should be noted that similar labels and letters in the following figures indicate similar items. Therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures.
[0040] In the description of the embodiments of this application, it should be noted that if terms such as "upper," "lower," "horizontal," or "inner" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship commonly used when the product of the invention is in use, they are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation on this application. In addition, terms such as "first" and "second" are only used to distinguish descriptions and should not be construed as indicating or implying relative importance.
[0041] Furthermore, the use of the term "horizontal" does not imply that the component must be absolutely horizontal, but rather that it can be slightly tilted. For example, "horizontal" simply means that its direction is more horizontal than "vertical," and does not mean that the structure must be completely horizontal, but can be slightly tilted.
[0042] In the description of the embodiments of this application, it should also be noted that, unless otherwise explicitly specified and limited, the terms "set," "install," "connect," and "link" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this application according to the specific circumstances.
[0043] With the continuous increase in voltage levels and power density, the resistive loss of conductors and the internal heat dissipation of insulation have become increasingly prominent, leading to a gradual increase in the operating temperature of insulating materials. This necessitates that insulating materials maintain excellent electrical properties even at high temperatures. However, under the influence of a DC electric field, the electric field exhibits a resistive distribution, and the resistivity of epoxy resin is extremely sensitive to temperature changes. High-temperature, high-electric-field environments easily cause electric field distortion and a decrease in insulation strength. The glass transition temperature of traditional anhydride-cured epoxy resin is only about 120°C; when the ambient temperature approaches this temperature, its electrical and mechanical properties will significantly decrease.
[0044] Based on the above, this application proposes an epoxy resin curing agent, an insulating epoxy resin, and a method for preparing the same. The following detailed description of this application is provided in conjunction with embodiments and accompanying drawings.
[0045] First, this application proposes an epoxy resin curing agent comprising two structures:
[0046] (1) At least two benzene ring structures, with adjacent benzene ring structures connected by a methylene group to form an integral structure, the methylene group being located at the 1,4 substitution position of the benzene ring structure. An amino functional group is provided on each side of the integral structure, and an electron-withdrawing substituent group or several sterically hindered substituent groups are provided at the adjacent positions of the amino functional groups.
[0047] The methylene groups connecting two adjacent benzene rings give the molecule a degree of flexibility while maintaining the rigidity of the benzene rings. An amino functional group is located on each side of the overall structure, serving as a key site for subsequent curing with epoxy resin. Electron-withdrawing substituents or several sterically hindered substituents are positioned ortho-positioned around the amino functional groups. These substituents affect the electron cloud density and steric hindrance of the amino functional groups, thus influencing their reactivity with epoxy resin and the properties of the cured product. Due to the presence of the benzene ring structure, this curing agent exhibits good heat and chemical resistance. Introducing highly electron-withdrawing groups can reduce the electron cloud density on the benzene ring by utilizing their strong electron adsorption, thereby increasing the resistivity of the material. Introducing sterically hindered groups can impede charge transfer between different molecules, thus increasing the resistivity of the final product.
[0048] (2) At least two non-coplanar rigid alicyclic structures, adjacent two non-coplanar rigid alicyclic structures are connected by methylene groups to form an integral structure, and an amino functional group is provided on each side of the integral structure. Electron-withdrawing substituents or several sterically hindered substituents are provided at the adjacent positions of the amino functional groups.
[0049] The second structure uses a non-planar structure to replace the benzene ring. The weak conjugation effect of the non-planar structure reduces the local electron concentration, thereby increasing the resistivity of the final product.
[0050] As some embodiments of the above-mentioned epoxy resin curing agent, specifically:
[0051] 1. It consists of two benzene ring structures:
[0052] (1) Electron-withdrawing substituents are high electron-withdrawing groups. High electron-withdrawing groups are groups with a strong ability to attract electrons, which can significantly reduce the electron cloud density on the benzene ring. They usually have strong electronegativity and can attract electrons through inductive and conjugation effects. Common high electron-withdrawing groups can be nitro groups, tertiary amine cations, halogen atoms, etc.
[0053] For example, using halogen atoms:
[0054] .
[0055] (2) Steric hindrance substituents can be large steric hindrance substituents. Large steric hindrance substituents refer to substituents with a large volume in the molecule. Due to their large volume, they occupy a certain area in space, causing the molecule as a whole to exhibit a certain degree of distortion or deformation. This distortion or deformation will affect the spatial orientation, three-dimensional structure and chemical properties of the molecule.
[0056] For example, using -CH3:
[0057] .
[0058] Use two -CH3:
[0059] .
[0060] Using -C2H5:
[0061] .
[0062] Use two -C2H5:
[0063] .
[0064] 2. Includes two non-coplanar rigid alicyclic structures:
[0065] Non-coplanar rigid alicyclic structure using C6H 12 :
[0066] .
[0067] The above-mentioned curing agent structure enhances the thermal stability of the epoxy resin by introducing benzene rings. By introducing high electron-withdrawing groups and large steric hindrance groups or using non-coplanar alicyclic structures with saturated electrons to replace benzene rings, the volume resistivity of epoxy resin at room temperature and high temperature is significantly improved, enabling it to maintain good electrical properties in high temperature gradient and large electric field environments.
[0068] This application also proposes a method for preparing insulating epoxy resin using the above-mentioned curing agent, which may include:
[0069] S1, dispersing the epoxy resin curing agent of this application in bisphenol A epoxy resin to obtain a first mixture.
[0070] S2, Alumina filler is added to the liquid phase mixture to obtain a second mixture.
[0071] Alumina filler can increase the mechanical strength, heat resistance, and thermal conductivity of epoxy resin. At the same time, alumina also possesses good insulation properties and high-temperature stability.
[0072] S3, the second mixture is heated to degas under vacuum, and then poured into a mold for vacuum degassing.
[0073] Degassing under vacuum conditions removes air bubbles from the mixture, improving the density and insulation properties of the finished product. The degassed mixture is then poured into a pre-prepared mold and degassed under vacuum to further remove air bubbles and ensure uniform distribution of the mixture within the mold.
[0074] S4, after curing and cooling, yields the finished insulating epoxy resin product.
[0075] Temperature and time can be controlled during the curing process to ensure the epoxy resin is fully cured. After curing, the pre-finished product can be removed from the mold and cooled. After cooling, the finished insulating epoxy resin product is obtained.
[0076] The following are some examples:
[0077] Example 1:
[0078] 4,4'-methylenebis(2-chloroaniline) (MOCA), which has a two-benzene-ring structure and a strong electron-withdrawing group -Cl, is used as the epoxy resin curing agent, namely:
[0079]
[0080] The preparation method of insulating epoxy resin is as follows:
[0081] (1) The bisphenol A epoxy resin (DGEBA) was preheated at 60 °C for 8 h. 4,4'-methylenebis(2-chloroaniline) (MOCA) was melted at 100 °C and the MOCA was dispersed in the bisphenol A epoxy resin at high speed for 30 min at the same temperature to obtain the first mixture.
[0082] (2) Alumina filler was added to the first mixture of epoxy resin curing agent and bisphenol A epoxy resin to obtain a second mixture. The second mixture was heated and stirred, and then vacuum degassed at 120 °C for 30 min. The mold was sprayed with a release agent and preheated at 120 °C. Subsequently, the second mixture was poured into the preheated mold and then vacuum degassed at the same temperature for 10 min. The second mixture contained 10 parts of 4,4'-methylenebis(2-chloroaniline) (MOCA), 15 parts of bisphenol A epoxy resin (DGEBA), and 35 parts of Al2O3 micron-based filler.
[0083] (3) The crosslinking reaction is carried out by gradually increasing the temperature. The curing environment temperature is raised to 120℃ and held for 60 min, then raised to 160℃ and held for 120 min, and finally raised to 180℃ and held for 120 min. After naturally cooling to room temperature, the insulating epoxy resin material with a thickness of about 0.3 mm is taken out from the mold and named EP-MOCA.
[0084] Example 2:
[0085] 4,4'-methylene-bis(2-methylaniline) (MBOT), which has a two-benzene-ring structure and a large sterically hindered group -CH3, is used as the epoxy resin curing agent, namely:
[0086]
[0087] The preparation method of insulating epoxy resin is as follows:
[0088] (1) The bisphenol A epoxy resin (DGEBA) was preheated at 80 °C for 6 h. 4,4'-methylene-bis(2-methylaniline) (MBOT) was melted at 110 °C, and MBOT was dispersed in the bisphenol A epoxy resin at the same temperature by high-speed stirring for 35 min to obtain the first mixture.
[0089] (2) Alumina filler was added to the first mixture of epoxy resin curing agent and bisphenol A epoxy resin to obtain a second mixture. The second mixture was heated and stirred, and then vacuum degassed at 100 °C for 50 min. The mold was sprayed with a release agent and preheated at 100 °C. Subsequently, the second mixture was poured into the preheated mold and then vacuum degassed at the same temperature for 20 min. The second mixture contained 35 parts of 4,4'-methylene-bis(2-methylaniline) (MBOT), 45 parts of bisphenol A epoxy resin (DGEBA), and 65 parts of Al2O3 micron-based filler.
[0090] (3) The crosslinking reaction is carried out by gradually increasing the temperature. The curing environment temperature is raised to 130℃ and held for 80 min, then raised to 170℃ and held for 100 min, and finally raised to 200℃ and held for 100 min. After naturally cooling to room temperature, the insulating epoxy resin material with a thickness of about 0.3 mm is taken out from the mold and named EP-MBOT.
[0091] Example 3:
[0092] 4,4-methylenebis(2,6-dimethylaniline) (MBMDA), which has a two-benzene-ring structure and a large sterically hindered group -CH3, is used as the epoxy resin curing agent, namely:
[0093]
[0094] The preparation method of insulating epoxy resin is as follows:
[0095] (1) The bisphenol A epoxy resin (DGEBA) was preheated at 75 °C for 6 h. 4,4-methylenebis(2,6-dimethylaniline) (MBMDA) was melted at 105 °C, and MBMDA was dispersed in the bisphenol A epoxy resin at the same temperature by high-speed stirring for 42 min to obtain the first mixture.
[0096] (2) Alumina filler was added to the first mixture of epoxy resin curing agent and bisphenol A epoxy resin to obtain a second mixture. The second mixture was heated and stirred, and then vacuum degassed at 140 °C for 45 min. The mold was sprayed with a release agent and preheated at 140 °C. Subsequently, the second mixture was poured into the preheated mold and then vacuum degassed at the same temperature for 15 min. The second mixture contained 20 parts of 4,4-methylenebis(2,6-dimethylaniline) (MBMDA), 30 parts of bisphenol A epoxy resin (DGEBA), and 50 parts of Al2O3 micron-based filler.
[0097] (3) The crosslinking reaction is carried out by gradually increasing the temperature. The curing environment temperature is raised to 120℃ and held for 70 min, then raised to 180℃ and held for 120 min, and finally raised to 220℃ and held for 60 min. After naturally cooling to room temperature, the insulating epoxy resin material with a thickness of about 0.3 mm is taken out from the mold and named EP-MBMDA.
[0098] Example 4:
[0099] 4,4'-methylenebis(2-ethylaniline) (MOEA), which has a two-benzene-ring structure and a large sterically hindered group -C2H5, is used as the epoxy resin curing agent, namely:
[0100]
[0101] The preparation method of insulating epoxy resin is as follows:
[0102] (1) The bisphenol A epoxy resin (DGEBA) was preheated at 80 °C for 7 h. 4,4'-methylenebis(2-ethylaniline) (MOEA) was melted at 115 °C and the MOEA was dispersed in the bisphenol A epoxy resin at the same temperature by high-speed stirring for 40 min to obtain the first mixture.
[0103] (2) Alumina filler was added to the first mixture of epoxy resin curing agent and bisphenol A epoxy resin to obtain a second mixture. The second mixture was heated and stirred, and then vacuum degassed at 130 °C for 50 min. The mold was sprayed with a release agent and preheated at 130 °C. Subsequently, the second mixture was poured into the preheated mold and then vacuum degassed at the same temperature for 25 min. The second mixture contained 20 parts of 4,4'-methylenebis(2-ethylaniline) (MOEA), 30 parts of bisphenol A epoxy resin (DGEBA), and 50 parts of Al2O3 micron-based filler.
[0104] (3) The crosslinking reaction is carried out by gradually increasing the temperature. The curing environment temperature is raised to 140℃ and held for 90 min, then raised to 170℃ and held for 100 min, and finally raised to 200℃ and held for 90 min. After naturally cooling to room temperature, the insulating epoxy resin material with a thickness of about 0.3 mm is taken out from the mold and named EP-MOEA.
[0105] Example 5:
[0106] 4,4'-methylenebis(2,6-diethylaniline) (MDEA), which has a two-benzene-ring structure and a large sterically hindered group -C2H5, is used as the epoxy resin curing agent, namely:
[0107]
[0108] The preparation method of insulating epoxy resin is as follows:
[0109] (1) The bisphenol A epoxy resin (DGEBA) was preheated at 80 °C for 8 h. 4,4'-methylenebis(2,6-diethylaniline) (MDEA) was melted at 120 °C and the MDEA was dispersed in the bisphenol A epoxy resin at the same temperature by high-speed stirring for 50 min to obtain the first mixture.
[0110] (2) Alumina filler was added to the first mixture of epoxy resin curing agent and bisphenol A epoxy resin to obtain a second mixture. The second mixture was heated and stirred, and then vacuum degassed at 140 °C for 50 min. The mold was sprayed with a release agent and preheated at 140 °C. Subsequently, the second mixture was poured into the preheated mold and then vacuum degassed at the same temperature for 30 min. The second mixture contained 20 parts of 4,4'-methylenebis(2,6-diethylaniline) (MDEA), 30 parts of bisphenol A epoxy resin (DGEBA), and 50 parts of Al2O3 micron-based filler.
[0111] (3) The crosslinking reaction is carried out by gradually increasing the temperature. The curing environment temperature is raised to 140℃ and held for 120 min, then raised to 180℃ and held for 150 min, and finally raised to 220℃ and held for 120 min. After naturally cooling to room temperature, the insulating epoxy resin material with a thickness of about 0.3 mm is taken out from the mold and named EP-MDEA.
[0112] Example 6:
[0113] C6H containing a non-coplanar saturated alicyclic structure 12 4,4'-Diaminodicyclohexylmethane (PACM) is used as an epoxy resin curing agent, namely:
[0114]
[0115] The preparation method of insulating epoxy resin is as follows:
[0116] (1) The bisphenol A epoxy resin (DGEBA) was preheated at 60 °C for 6 h. 4,4'-diaminodicyclohexylmethane (PACM) was melted at 100 °C and the PACM was dispersed in the bisphenol A epoxy resin at high speed for 30 min at the same temperature to obtain the first mixture.
[0117] (2) Alumina filler was added to the first mixture of epoxy resin curing agent and bisphenol A epoxy resin to obtain a second mixture. The second mixture was heated and stirred, and then vacuum degassed at 100 °C for 30 min. The mold was sprayed with a release agent and preheated at 100 °C. Subsequently, the second mixture was poured into the preheated mold and then vacuum degassed at the same temperature for 10 min. The second mixture contained 20 parts of 4,4'-diaminodicyclohexylmethane (PACM), 30 parts of bisphenol A epoxy resin (DGEBA), and 50 parts of Al2O3 micron-based filler.
[0118] (3) The crosslinking reaction is carried out by gradually increasing the temperature. The curing environment temperature is raised to 120℃ and held for 60 min, then raised to 160℃ and held for 100 min, and finally raised to 180℃ and held for 60 min. After naturally cooling to room temperature, the insulating epoxy resin material with a thickness of about 0.3 mm is taken out from the mold and named EP-PACM.
[0119] Comparative example:
[0120] Using 4,4'-diaminodiphenylmethane (DDM) as the epoxy resin curing agent, the preparation method of the insulating epoxy resin is as follows:
[0121] (1) The bisphenol A epoxy resin (DGEBA) was preheated at 70 °C for 7 h. 4,4'-diaminodiphenylmethane (DDM) was melted at 110 °C and dispersed in the bisphenol A epoxy resin at the same temperature by high-speed stirring for 40 min to obtain the first mixture.
[0122] (2) Alumina filler was added to the liquid-phase mixture of epoxy resin curing agent and bisphenol A epoxy resin to obtain a second mixture. The mixture was heated and stirred, and then vacuum degassed at 120 °C for 40 min. The mold was then sprayed with a release agent and preheated at 120 °C. Subsequently, the mixture was poured into the preheated mold and then vacuum degassed at the same temperature for 20 min. The second mixture contained 20 parts of 4,4'-diaminodiphenylmethane (DDM), 30 parts of epoxy resin E51, and 50 parts of Al2O3 micron-based filler.
[0123] (3) The crosslinking reaction is carried out by gradually increasing the temperature. The curing environment temperature is raised to 130 ℃ and held for 90 min, then raised to 170 ℃ and held for 125 min, and finally raised to 210 ℃ and held for 80 min. After naturally cooling to room temperature, the insulating epoxy resin material with a thickness of about 0.3 mm is taken out from the mold and named EP-DDM.
[0124] Figure 1 shows the Fourier transform infrared (FTIR) spectra of bisphenol A epoxy resin (DGEBA), insulating epoxy resins obtained in Examples 1-6 of this application, and comparative examples. As can be seen from Figure 1, at 915 cm⁻¹... -1 The disappearance of the absorption peak at 3300-3450 cm⁻¹ and the disappearance of the characteristic peaks associated with the epoxy group indicate that the addition reaction between the amine and the epoxy ring has been completed. -1 The disappearance of the NH stretching vibration absorption peak within the range also confirms the consumption of the -NH2 functional group in the curing agent.
[0125] Figure 2 shows the glass transition temperatures of the insulating epoxy resins obtained in Examples 1-6 and the comparative examples of this application. For the insulating epoxy resins prepared in Examples 1-6 and the comparative examples, their glass transition temperatures are all much higher than the glass transition temperature of traditional anhydride-cured epoxy resins (approximately 120 °C), and the glass transition temperature of EP-MBMDA reaches 200 °C. It can be seen that the introduction of the benzene ring leads to an increase in the glass transition temperature of the resin, and because cyclohexane also has a certain degree of rigidity, the glass transition temperature of EP-PACM is also relatively high.
[0126] Figure 3 shows the DC breakdown strength and shape parameters of the insulating epoxy resins obtained in Examples 1-6 and the comparative examples of this application at room temperature. The breakdown field strength is the Weibull breakdown strength. It can be seen that epoxy resin curing agents containing strong electron-withdrawing groups and large steric hindrance groups all exhibit high electrical properties at room temperature. Furthermore, for EP-MOEA and EP-MOCA, their breakdown strength exceeds 200 kV / mm, which is higher than the performance of traditional anhydride-cured epoxy resins.
[0127] Figure 4 shows the volume resistivity results of the insulating epoxy resins obtained in Examples 1-6 and the comparative examples of this application at 80 °C. It can be seen that the volume resistivity of both EP-MOCA and EP-PACM at 80 °C exceeds 2.5 × 10⁻⁶. 15 The volume resistivity of the epoxy resins prepared in the other examples, Ω·cm, is significantly higher than that of traditional anhydride-cured epoxy resins. Except for EP-MBOT, the volume resistivity of the insulating epoxy resins prepared in the other examples at 80 °C is higher than that of EP-DDM. This indicates that epoxy resin curing agents containing strong electron-withdrawing groups and large steric hindrance groups, as well as those using non-coplanar saturated alicyclic structures instead of benzene rings, can maintain a high volume resistivity of insulating epoxy resins at high temperatures.
[0128] For current polymer electrolyte materials, electrical properties and thermal stability are often mutually exclusive; increased temperature often leads to degradation of insulation performance. To develop epoxy resins with both high thermal stability and high electrical properties, this application proposes a modified epoxy resin curing agent, a method for preparing insulating epoxy resin, and an insulating epoxy resin prepared by the same method. The thermal stability of the epoxy resin is enhanced by introducing a benzene ring. High electron-withdrawing groups or sterically hindered groups are grafted to the ortho positions of the amino functional groups on the benzene ring to reduce the π-electron concentration on the benzene ring or to block charge transfer between different molecules due to the benzene ring conjugation effect, thereby improving the electrical properties of the epoxy resin. Furthermore, this application proposes using a non-planar rigid alicyclic structure with saturated electrons instead of the benzene ring, utilizing its weak conjugation effect to reduce the concentration of non-local electrons, thereby improving the electrical properties of the epoxy resin. The epoxy resin curing agent obtained by the above method is used to prepare high-resistivity insulating epoxy resin materials. The volume resistivity of the obtained insulating epoxy resin materials is significantly improved at both room temperature and high temperature, which is of great significance for solving the insulation failure problem in high temperature gradient and high field strength environments.
[0129] The above are merely preferred embodiments of this application and are not intended to limit this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.
Claims
1. An epoxy resin curing agent, characterized in that, include: At least two benzene ring structures or at least two non-coplanar rigid alicyclic structures; Two adjacent benzene ring structures or non-coplanar rigid alicyclic structures are connected by methylene groups to form an integral structure; The overall structure has an amino functional group on each side, and an electron-withdrawing substituent group or several sterically hindered substituent groups are arranged adjacent to the amino functional group.
2. The epoxy resin curing agent according to claim 1, characterized in that, The electron-withdrawing substituent is -Cl; The sterically hindered substituent group is -CH3 or -C2H5.
3. The epoxy resin curing agent according to claim 1, characterized in that, The epoxy resin curing agent structure includes at least two non-coplanar rigid alicyclic structures; The non-coplanar rigid alicyclic structure is C6H 12 .
4. The epoxy resin curing agent according to claim 1, characterized in that, The number of sterically hindered substituents is 1-2.
5. A method for preparing an insulating epoxy resin, characterized in that, include: Disperse the epoxy resin curing agent according to any one of claims 1 to 4 in bisphenol A epoxy resin to obtain a first mixture; Alumina filler was added to the liquid mixture to obtain a second mixture; The second mixture is heated to degas it under vacuum, and then poured into a mold for further degassing. After curing and cooling, the insulating epoxy resin product is obtained.
6. The method for preparing insulating epoxy resin according to claim 5, characterized in that, The weight ratio of epoxy resin curing agent, bisphenol A epoxy resin and alumina filler is (10~35):(15~45):(35~65).
7. The method for preparing insulating epoxy resin according to claim 5, characterized in that, The curing conditions are as follows: Raise the temperature to 120~140 ℃ and hold for 60~120 min; then raise the temperature to 160~180 ℃ and hold for 100~150 min; finally raise the temperature to 180~220 ℃ and hold for 60~120 min.
8. The method for preparing insulating epoxy resin according to claim 5, characterized in that, The method for dispersing the epoxy resin curing agent in bisphenol A epoxy resin includes: The epoxy resin curing agent is melted at 100~120 ℃, and then stirred and dispersed in bisphenol A epoxy resin at 100~120 ℃.
9. The method for preparing insulating epoxy resin according to claim 5, characterized in that, The second mixture is heated to a temperature of 100~140 °C to achieve vacuum degassing.
10. An insulating epoxy resin, characterized in that, It is prepared by any one of the insulating epoxy resin preparation methods described in claims 5-9.