Degradable epoxy resin heat-conducting composite material as well as preparation method and recovery method thereof

Abstract

The invention discloses a degradable epoxy resin heat-conducting composite material as well as a preparation method and a recovery method thereof. Belongs to the technical field of dry-type electrical equipment insulating materials. The invention aims to solve the core problem that the service life of dry-type power equipment is short due to the fact that a heat-conducting insulating material of the dry-type power equipment is difficult to recycle and poor in heat-conducting property. The composite material comprises an epoxy resin raw material, a curing agent and an inorganic heat-conducting filler, the specific preparation process comprises the following steps: heating and uniformly mixing the components, degassing in a vacuum state, and then curing. The curing agent with simple synthesis process and excellent degradation performance and the composite material with excellent insulating property and high thermal conductivity can be dissolved in the degradation solvent under the heating condition, and then the inorganic thermal conductive filler is recycled by means of filtration separation. The preparation and recovery process is simple, can be used in the field of dry-type electrical equipment insulating materials, and has wide application prospects and environmental protection significance.

Description

Technical Field

[0001] This invention belongs to the technical field of insulation materials for dry-type power equipment, specifically relating to a biodegradable epoxy resin thermally conductive composite material and its preparation and recycling methods. It is applied to dry-type power equipment. Background Technology

[0002] Dry-type electrical equipment refers to electrical equipment that employs dry-type insulation technology, characterized by being oil-free, fire-resistant, and explosion-proof. Common dry-type electrical equipment includes dry-type bushings, dry-type transformers, and dry-type reactors. Traditional epoxy resin, as a thermosetting resin, is widely used as an insulating material in dry-type electrical equipment due to its excellent insulation properties. However, dry-type electrical equipment generates significant internal heat, and the accumulation of internal heat accelerates the aging of the insulation, causing cracking and breakdown, thus affecting its service life. Therefore, imparting excellent thermal conductivity to the insulating material can effectively prevent internal cracking. Furthermore, the highly cross-linked three-dimensional network structure of traditional epoxy resin makes it non-degradable and non-recyclable in the natural environment, severely limiting sustainable development and further restricting the maintenance and reuse of the equipment, thereby shortening the overall lifespan of dry-type electrical equipment such as dry-type transformers.

[0003] In recent years, the main raw materials for synthesizing biodegradable epoxy resins have included lignin, itaconic acid, and vegetable oils. Vanillin, a small molecule isolated from lignin, is a bio-based derivative that possesses both strong reactivity and a simple structure. Furthermore, it is the only sustainable bio-based derivative containing a benzene ring structure that can be mass-produced. Imine bonds, ester bonds, acetal bonds, and disulfide bonds are dynamic covalent bonds frequently used in recent years to construct covalent adaptive networks. Among them, imine bonds stand out in the development of biodegradable epoxy resins due to their simple synthesis process, high yield, and ability to undergo various reversible reactions such as hydrolysis and amine-imine substitution. However, existing technologies still suffer from insufficient dynamic exchange efficiency and difficulties in balancing the mechanical and thermal conductivity of cured epoxy resins, failing to meet the high-efficiency heat dissipation requirements of power equipment. Therefore, developing curing agents with simple synthesis processes and excellent degradation performance, as well as novel biodegradable epoxy resins and thermally conductive composite materials that combine biodegradability and high thermal conductivity, is crucial and has become an urgent technical problem to be solved in this field. Summary of the Invention

[0004] The purpose of this invention is to address the core problems of poor thermal conductivity and short lifespan of dry-type power equipment, which are caused by the difficulty in recycling thermally conductive and insulating materials. This invention provides a biodegradable epoxy resin thermally conductive composite material with a covalently adaptable network for dry-type power equipment, along with its preparation and recycling methods. By introducing dynamic imine bonds during the curing reaction, this invention significantly improves the heat resistance, mechanical properties, thermal conductivity, insulation properties, and chemical degradability of the biodegradable epoxy resin and the thermally conductive composite material.

[0005] To address the aforementioned technical problems, the present invention adopts the following technical solution: The purpose of this invention is to provide a vanillin-based curing agent containing imine bonds, characterized by the following structural formula: .

[0006] Another object of the present invention is to provide a method for synthesizing the above-mentioned curing agent, characterized by comprising the following steps: Vanillin and 3-aminophenol were weighed in a molar ratio of (0.8-1):(0.8-1), and a reaction solvent was added. The mixture was refluxed at 50-70°C under nitrogen protection and stirred for 3-5 hours. After the reaction was completed, the solvent was removed by heating and evaporation, and the mixture was dried to obtain a vanillin-based curing agent containing imine bonds.

[0007] Furthermore, the reaction solvent is anhydrous ethanol.

[0008] Another objective of this invention is to provide a biodegradable epoxy resin thermally conductive composite material, comprising, by mass percentage, 50%-75% epoxy resin raw material, 10%-15% of the aforementioned curing agent, and 10%-40% inorganic thermally conductive filler.

[0009] Furthermore, the inorganic thermally conductive filler is specified as blocky calcium fluoride.

[0010] Another object of the present invention is to provide a method for preparing the above-mentioned biodegradable epoxy resin thermally conductive composite material.

[0011] A method for preparing a biodegradable epoxy resin thermally conductive composite material includes the following steps: The curing agent described in claim 1 is dispersed in a small amount of dispersion solvent, mixed with epoxy resin and inorganic thermally conductive filler, stirred at 50-70°C for 1-2 hours, and then dried in a vacuum oven at room temperature for 1-2 hours to remove air bubbles. The mixture is then poured into a mold and cured at 70-90°C for 5-7 hours to obtain a biodegradable epoxy resin thermally conductive composite material.

[0012] Another object of the present invention is to provide a method for preparing biodegradable epoxy resin.

[0013] A method for preparing a biodegradable epoxy resin includes the following steps: dispersing the above-mentioned curing agent in a small amount of dispersion solvent, mixing it with epoxy resin, stirring at 60°C for 1-2 hours, removing air bubbles in a vacuum oven at room temperature for 1-2 hours, pouring it into a mold, curing at 70-90°C for 5-7 hours, and then allowing it to cool naturally to obtain the biodegradable epoxy resin. Further specifying, the dispersing solvent is N,N-dimethylformamide.

[0014] Further specifying, the epoxy resin is E51 type epoxy resin.

[0015] Further specified, the mass ratio of the curing agent to the epoxy resin is 100:(20-60).

[0016] To further specify, the mold is a polytetrafluoroethylene mold.

[0017] Another objective of this invention is to provide a method for recovering inorganic thermally conductive fillers from the above-mentioned biodegradable epoxy resin thermally conductive composite material, comprising the following steps: pulverizing the above-mentioned composite material into powder, adding a chemical degradation solvent, condensing and refluxing under nitrogen protection at 90°C-160°C, filtering and separating, and recovering the inorganic thermally conductive fillers.

[0018] Further specifying, the chemical degradation solvent includes one or more of glacial acetic acid, ethylene glycol, ethylenediamine, and N,N-dimethylformamide.

[0019] Compared with the prior art, the present invention has the following beneficial effects: The imine-containing vanillin-based curing agent prepared by this invention has mild synthesis conditions and a simple process, requiring no high temperature or high pressure. The raw material, vanillin, is a bio-based derivative with both strong reactivity and a simple structure. Furthermore, it is the only sustainable bio-based derivative containing a benzene ring structure that can be mass-produced. The imine-containing vanillin-based curing agent is suitable for industrial production, and by introducing dynamic imine bonds, it can achieve efficient degradation in amine solutions.

[0020] The biodegradable epoxy resin thermally conductive composite material prepared by this invention has a covalently adaptable network.

[0021] The biodegradable epoxy resin prepared by this invention has excellent mechanical properties, heat resistance and insulation properties, with tensile strength > 47 MPa and breakdown field strength ≥ 22 kV / mm. It solves the core problem of the short lifespan of dry power equipment caused by the difficulty in recycling thermosetting epoxy resin insulation materials, effectively saving resources and having practical application value under the concept of sustainable development.

[0022] The biodegradable epoxy resin thermally conductive composite material prepared by this invention possesses excellent thermal conductivity and insulation properties by constructing a continuous thermally conductive pathway. The thermal conductivity can reach up to 1.094 W / (m*K), and the breakdown field strength is >35 kV / mm, reaching a maximum of 45.3 kV / mm, far exceeding that of traditional epoxy resins. Furthermore, its mechanical properties are stable, fully meeting the performance requirements for insulation materials in dry-type power equipment. Simultaneously, the preparation process of the biodegradable epoxy resin and thermally conductive composite material in this invention is simple, with low raw material costs, making it suitable for industrial production. The recycling method for the biodegradable epoxy resin and thermally conductive composite material is simple, with low operating pressure, and the inorganic thermally conductive powder separated by degradation can be recycled again, representing an economically feasible industrial production route. Compared with low-end treatment methods such as pyrolysis and pulverization, this invention ensures the material's excellent biodegradability, thereby enabling multiple recycling of the inorganic thermally conductive powder, achieving a balance between environmental protection and high performance, and possessing significant economic and environmental value.

[0023] For a deeper understanding of the features and technical content of this invention, please refer to the accompanying detailed description and drawings. It should be noted that the drawings are provided for illustrative purposes only and are not intended to limit the scope of the invention. Attached Figure Description

[0024] Figure 1 This is a schematic diagram of the FT-IR spectrum of the vanillin-based curing agent containing imine bonds in this invention; Figure 2 This is a schematic diagram of the stress-strain curve of the biodegradable epoxy resin in this invention; Figure 3 This is a schematic diagram of the cross-sectional structure of the biodegradable epoxy resin thermally conductive composite material in this invention; Figure 4 This is a schematic diagram of the thermal conductivity of the biodegradable epoxy resin thermally conductive composite material in this invention; Figure 5 This is a schematic diagram of the insulation performance of the biodegradable epoxy resin thermally conductive composite material in this invention. Detailed Implementation

[0025] The present invention will be described in detail below with reference to specific embodiments. These embodiments will help those skilled in the art to further understand the present invention, but should not be considered as limiting the present invention. It should be noted that those skilled in the art can make several modifications and improvements without departing from the concept of the present invention. These all fall within the protection scope of the present invention.

[0026] Example 1 The development of biodegradable epoxy resin and thermally conductive composite materials with covalently adaptable networks for dry-type power equipment involves weighing out the following components by weight: 10.913 g 3-aminophenol, 150 ml anhydrous ethanol (reaction solvent), 15.215 g vanillin, 1 g vanillin-based curing agent containing imine bonds, 5 g epoxy resin E51, 4 ml N,N-dimethylformamide (dispersion solvent), 0.67 g blocky calcium fluoride (thermal filler), 20 ml ethanolamine (ETA), 20 ml ethylene glycol (EG), and 20 ml DMF (acetic acid) mixed solvent. v HAc: v DMF=1:4).

[0027] The development of biodegradable epoxy resins and thermally conductive composite materials with covalently adaptable networks for dry-type power equipment includes the following steps: Step S1: Synthesis of vanillin-based curing agent containing imine bonds. Vanillin and 3-aminophenol were weighed in a molar ratio of 1:1, added to the reaction solvent, and reacted under nitrogen protection at 60°C with stirring for 4 hours. After the reaction was completed, the solvent was removed by heating and evaporation, and the product was dried to obtain the vanillin-based curing agent containing imine bonds; its structural formula is as follows: .

[0028] Step S2, preparation of biodegradable epoxy resin: The above curing agent is dispersed in a small amount of dispersion solvent and mixed with epoxy resin at mass ratios of 100:20, 100:40 and 100:60. The mixture is stirred at 60°C for 1-2 hours, and after removing air bubbles in a vacuum oven at room temperature for 1-2 hours, it is poured into a mold and cured at 80°C for 6 hours. The biodegradable epoxy resin is obtained by natural cooling. Step S3, Preparation of biodegradable epoxy resin thermally conductive composite material: The above curing agent is dispersed in a small amount of dispersion solvent and mixed with epoxy resin at a mass ratio of 100:20 and 10%-40% of the total mass of thermally conductive filler block calcium fluoride. The mixture is stirred at 60°C for 1-2 hours, and after removing air bubbles in a vacuum oven at room temperature for 1-2 hours, it is poured into a mold and cured at 80°C for 6 hours. After natural cooling, the biodegradable epoxy resin thermally conductive composite material is obtained. Step S4, degradation experiment of biodegradable epoxy resin and thermally conductive composite material: After crushing the biodegradable epoxy resin thermally conductive composite material into powder, a certain amount of biodegradable epoxy resin thermally conductive composite material is weighed, a chemical degradation solvent is added, and the reaction is carried out under nitrogen protection at 90℃-160℃ for 1.5h under reflux. The resin degradation process is monitored by a camera.

[0029] A degradation method for biodegradable epoxy resin and thermally conductive composite materials with covalently adaptable networks for dry-type power equipment, wherein, under sealed conditions, the biodegradable epoxy resin and thermally conductive composite material powder prepared by the above method are respectively immersed in a mixed solvent of 20 ml ethanolamine (ETA), 20 ml ethylene glycol (EG), and 20 ml glacial acetic acid DMF. v HAc: v The resin was reacted in a 1:4 mixture of DMF in three-necked flasks equipped with condensers at 160°C, 180°C, and 90°C for 1.5 h. The degradation process was monitored using a camera.

[0030] Example 2 The development of biodegradable epoxy resin and thermally conductive composite materials with covalently adaptable networks for dry-type power equipment involves weighing out the following components by weight: 10.913 g 3-aminophenol, 150 ml anhydrous ethanol (reaction solvent), 15.215 g vanillin, 1 g vanillin-based curing agent containing imine bonds, 5 g epoxy resin E51, 4 ml N,N-dimethylformamide (dispersion solvent), 1.5 g blocky calcium fluoride (thermal filler), 20 ml ethanolamine (ETA), 20 ml ethylene glycol (EG), and 20 ml DMF (acetic acid) mixed solvent. v HAc: v DMF=1:4).

[0031] The development of biodegradable epoxy resins and thermally conductive composite materials with covalently adaptable networks for dry-type power equipment includes the following steps: Step S1: Synthesis of vanillin-based curing agent containing imine bonds. Vanillin and 3-aminophenol were weighed in a molar ratio of 1:1, added to the reaction solvent, and reacted under nitrogen protection at 60°C with stirring for 4 hours. After the reaction was completed, the solvent was removed by heating and evaporation, and the product was dried to obtain the vanillin-based curing agent containing imine bonds. Step S2, preparation of biodegradable epoxy resin: The above curing agent is dispersed in a small amount of dispersion solvent and mixed with epoxy resin at mass ratios of 100:20, 100:40 and 100:60. The mixture is stirred at 60°C for 1-2 hours, and after removing air bubbles in a vacuum oven at room temperature for 1-2 hours, it is poured into a mold and cured at 80°C for 6 hours. The biodegradable epoxy resin is obtained by natural cooling. Step S3, Preparation of biodegradable epoxy resin thermally conductive composite material: The above curing agent is dispersed in a small amount of dispersion solvent and mixed with epoxy resin at a mass ratio of 100:20 and 10%-40% of the total mass of thermally conductive filler block calcium fluoride. The mixture is stirred at 60°C for 1-2 hours, and after removing air bubbles in a vacuum oven at room temperature for 1-2 hours, it is poured into a mold and cured at 80°C for 6 hours. After natural cooling, the biodegradable epoxy resin thermally conductive composite material is obtained. Step S4, degradation experiment of biodegradable epoxy resin and thermally conductive composite material: After crushing the biodegradable epoxy resin thermally conductive composite material into powder, a certain amount of biodegradable epoxy resin thermally conductive composite material is weighed, a chemical degradation solvent is added, and the reaction is carried out under nitrogen protection at 90℃-160℃ for 1.5h under reflux. The resin degradation process is monitored by a camera.

[0032] A degradation method for biodegradable epoxy resin and thermally conductive composite materials with covalently adaptable networks for dry-type power equipment, wherein, under sealed conditions, the biodegradable epoxy resin and thermally conductive composite material powder prepared by the above method are respectively immersed in a mixed solvent of 20 ml ethanolamine (ETA), 20 ml ethylene glycol (EG), and 20 ml glacial acetic acid DMF. v HAc: v The resin was reacted in a 1:4 mixture of DMF in three-necked flasks equipped with condensers at 160°C, 180°C, and 90°C for 1.5 h. The degradation process was monitored using a camera.

[0033] Example 3 The development of biodegradable epoxy resin and thermally conductive composite materials with covalently adaptable networks for dry-type power equipment involves weighing out the following components by weight: 10.913 g 3-aminophenol, 150 ml anhydrous ethanol (reaction solvent), 15.215 g vanillin, 1 g vanillin-based curing agent containing imine bonds, 5 g epoxy resin E51, 4 ml N,N-dimethylformamide (dispersion solvent), 2.57 g blocky calcium fluoride (thermal filler), 20 ml ethanolamine (ETA), 20 ml ethylene glycol (EG), and 20 ml glacial acetic acid DMF mixed solvent. v HAc: v DMF=1:4).

[0034] The development of biodegradable epoxy resins and thermally conductive composite materials with covalently adaptable networks for dry-type power equipment includes the following steps: Step S1: Synthesis of vanillin-based curing agent containing imine bonds. Vanillin and 3-aminophenol were weighed in a molar ratio of 1:1, added to the reaction solvent, and reacted under nitrogen protection at 60°C with stirring for 4 hours. After the reaction was completed, the solvent was removed by heating and evaporation, and the product was dried to obtain the vanillin-based curing agent containing imine bonds. Step S2, preparation of biodegradable epoxy resin: The above curing agent is dispersed in a small amount of dispersion solvent and mixed with epoxy resin at mass ratios of 100:20, 100:40 and 100:60. The mixture is stirred at 60°C for 1-2 hours, and after removing air bubbles in a vacuum oven at room temperature for 1-2 hours, it is poured into a mold and cured at 80°C for 6 hours. The biodegradable epoxy resin is obtained by natural cooling. Step S3, Preparation of biodegradable epoxy resin thermally conductive composite material: The above curing agent is dispersed in a small amount of dispersion solvent and mixed with epoxy resin at a mass ratio of 100:20 and 10%-40% of the total mass of thermally conductive filler block calcium fluoride. The mixture is stirred at 60°C for 1-2 hours, and after removing air bubbles in a vacuum oven at room temperature for 1-2 hours, it is poured into a mold and cured at 80°C for 6 hours. After natural cooling, the biodegradable epoxy resin thermally conductive composite material is obtained. Step S4, degradation experiment of biodegradable epoxy resin and thermally conductive composite material: After crushing the biodegradable epoxy resin thermally conductive composite material into powder, a certain amount of biodegradable epoxy resin thermally conductive composite material is weighed, a chemical degradation solvent is added, and the reaction is carried out under nitrogen protection at 90℃-160℃ for 1.5h under reflux. The resin degradation process is monitored by a camera.

[0035] A degradation method for biodegradable epoxy resin and thermally conductive composite materials with covalently adaptable networks for dry-type power equipment, wherein, under sealed conditions, the biodegradable epoxy resin and thermally conductive composite material powder prepared by the above method are respectively immersed in a mixed solvent of 20 ml ethanolamine (ETA), 20 ml ethylene glycol (EG), and 20 ml glacial acetic acid DMF. v HAc: v The resin was reacted in a 1:4 mixture of DMF in three-necked flasks equipped with condensers at 160°C, 180°C, and 90°C for 1.5 h. The degradation process was monitored using a camera.

[0036] Example 4 The development of biodegradable epoxy resin and thermally conductive composite materials with covalently adaptable networks for dry-type power equipment involves weighing out the following components by weight: 10.913 g 3-aminophenol, 150 ml anhydrous ethanol (reaction solvent), 15.215 g vanillin, 1 g vanillin-based curing agent containing imine bonds, 5 g epoxy resin E51, 4 ml N,N-dimethylformamide (dispersion solvent), 4 g block calcium fluoride (thermal filler), 20 ml ethanolamine (ETA), 20 ml ethylene glycol (EG), and 20 ml DMF (glacial acetic acid) mixed solvent. v HAc: v DMF=1:4).

[0037] The development of biodegradable epoxy resins and thermally conductive composite materials with covalently adaptable networks for dry-type power equipment includes the following steps: Step S1: Synthesis of vanillin-based curing agent containing imine bonds. Vanillin and 3-aminophenol were weighed in a molar ratio of 1:1, added to the reaction solvent, and reacted under nitrogen protection at 60°C with stirring for 4 hours. After the reaction was completed, the solvent was removed by heating and evaporation, and the product was dried to obtain the vanillin-based curing agent containing imine bonds. Step S2, preparation of biodegradable epoxy resin: The above curing agent is dispersed in a small amount of dispersion solvent and mixed with epoxy resin at mass ratios of 100:20, 100:40 and 100:60. The mixture is stirred at 60°C for 1-2 hours, and after removing air bubbles in a vacuum oven at room temperature for 1-2 hours, it is poured into a mold and cured at 80°C for 6 hours. The biodegradable epoxy resin is obtained by natural cooling. Step S3, Preparation of biodegradable epoxy resin thermally conductive composite material: The above curing agent is dispersed in a small amount of dispersion solvent and mixed with epoxy resin at a mass ratio of 100:20 and 10%-40% of the total mass of thermally conductive filler block calcium fluoride. The mixture is stirred at 60°C for 1-2 hours, and after removing air bubbles in a vacuum oven at room temperature for 1-2 hours, it is poured into a mold and cured at 80°C for 6 hours. After natural cooling, the biodegradable epoxy resin thermally conductive composite material is obtained. Step S4, degradation experiment of biodegradable epoxy resin and thermally conductive composite material: After crushing the biodegradable epoxy resin thermally conductive composite material into powder, a certain amount of biodegradable epoxy resin thermally conductive composite material is weighed, a chemical degradation solvent is added, and the reaction is carried out under nitrogen protection at 90℃-160℃ for 1.5h under reflux. The resin degradation process is monitored by a camera.

[0038] A degradation method for biodegradable epoxy resin and thermally conductive composite materials with covalently adaptable networks for dry-type power equipment, wherein, under sealed conditions, the biodegradable epoxy resin and thermally conductive composite material powder prepared by the above method are respectively immersed in a mixed solvent of 20 ml ethanolamine (ETA), 20 ml ethylene glycol (EG), and 20 ml glacial acetic acid DMF. v HAc: v The resin was reacted in a 1:4 mixture of DMF in three-necked flasks equipped with condensers at 160°C, 180°C, and 90°C for 1.5 h. The degradation process was monitored using a camera.

[0039] Comparative Example 1 The development of biodegradable epoxy resin and thermally conductive composite materials with covalently adaptable networks for dry power equipment involves weighing 10.913g of 3-aminophenol, 150ml of anhydrous ethanol as the reaction solvent, 15.215g of vanillin, 1g of vanillin-based curing agent containing imine bonds, 5g of epoxy resin E51, 4ml of N,N-dimethylformamide as the dispersion solvent, and 20ml of ethanolamine (ETA).

[0040] The development of biodegradable epoxy resins and thermally conductive composite materials with covalently adaptable networks for dry-type power equipment includes the following steps: Step S1: Synthesis of vanillin-based curing agent containing imine bonds. Vanillin and 3-aminophenol were weighed in a molar ratio of 1:1, added to the reaction solvent, and reacted under nitrogen protection at 60°C with stirring for 4 hours. After the reaction was completed, the solvent was removed by heating and evaporation, and the product was dried to obtain the vanillin-based curing agent containing imine bonds. Step S2, preparation of biodegradable epoxy resin: The above curing agent is dispersed in a small amount of dispersion solvent and mixed with epoxy resin at mass ratios of 100:20, 100:40 and 100:60. The mixture is stirred at 60°C for 1-2 hours, and after removing air bubbles in a vacuum oven at room temperature for 1-2 hours, it is poured into a mold and cured at 80°C for 6 hours. The biodegradable epoxy resin is obtained by natural cooling. Step S3, Preparation of biodegradable epoxy resin thermally conductive composite material: The above curing agent is dispersed in a small amount of dispersion solvent and mixed with epoxy resin at a mass ratio of 100:20 and 10%-40% of the total mass of thermally conductive filler block calcium fluoride. The mixture is stirred at 60°C for 1-2 hours, and after removing air bubbles in a vacuum oven at room temperature for 1-2 hours, it is poured into a mold and cured at 80°C for 6 hours. After natural cooling, the biodegradable epoxy resin thermally conductive composite material is obtained. Step S4, degradation experiment of biodegradable epoxy resin and thermally conductive composite material: After crushing the biodegradable epoxy resin thermally conductive composite material into powder, a certain amount of biodegradable epoxy resin thermally conductive composite material is weighed, a chemical degradation solvent is added, and the reaction is carried out under nitrogen protection at 90℃-160℃ for 1.5h under reflux. The resin degradation process is monitored by a camera.

[0041] A degradation method for biodegradable epoxy resin and thermally conductive composite materials with covalently adaptable networks for dry-type power equipment is described. Under sealed conditions, the biodegradable epoxy resin powder prepared by the above method is immersed in 20 ml of ethanolamine (ETA) in a three-necked flask equipped with a condenser at 160°C for 1.5 h. The resin degradation process is monitored using a camera.

[0042] Performance testing: The biodegradable epoxy resins and thermally conductive composite materials prepared in Examples 1-4 and Comparative Example 1 were subjected to the following performance tests: Dynamic mechanical analysis (DMA) was performed to determine the glass transition temperature Tg of the cured resin; Thermal conductivity and breakdown performance tests were conducted to determine the thermal diffusivity α, thermal conductivity, and breakdown strength of biodegradable epoxy resin and thermally conductive composite materials. Table 1

[0043] Compared to Example 4, Comparative Example 1 did not add the thermally conductive filler block calcium fluoride. Data shows that the thermal conductivity decreased by 0.791 W / (m×K). This is because, with the increase of the inorganic thermally conductive filler CaF2 content, the powder particles come into contact and overlap, forming a continuous thermally conductive network. Heat can be rapidly transferred through the highly thermally conductive powder particles, and the continuity and integrity of the pathway increase with the increase of powder content, continuously improving heat transfer efficiency. The relative influence of interfacial thermal resistance is weakened. The high thermal conductivity inorganic powder CaF2 gradually replaces the low thermal conductivity epoxy resin matrix, allowing more heat to be transferred through the powder network and reducing inefficient heat conduction in the matrix.

[0044] Compared to Example 1, Comparative Example 1 did not add the thermally conductive filler block calcium fluoride. Data shows that the breakdown strength decreased by 16.1 kV / mm. This is because the inorganic thermally conductive filler CaF2 has excellent insulation properties and low dielectric loss. When added to the biodegradable epoxy resin, it acts as a physical barrier to inhibit the growth and extension of electrical trees, disperses locally concentrated electric fields, and captures charge carriers to reduce space charge accumulation, thereby improving the breakdown strength of the composite material.

[0045] The specific embodiments of the present invention have been described in detail above. It should be noted that the present invention is not limited to the specific embodiments described above. Various modifications or alterations can be made by those skilled in the art without departing from the scope of protection defined by the claims, and all such modifications or alterations fall within the scope of the present invention.

Claims

1. A vanillin-based curing agent containing an imine bond, characterized in that, Its structural formula is as follows: 。 2. The method for synthesizing the curing agent as described in claim 1, characterized in that, Includes the following steps: Weigh vanillin and 3-aminophenol at a molar ratio of (0.8-1): (0.8-1), add them to the reaction solvent, and reflux at 50-70°C for 3-5 hours under nitrogen protection. After the reaction is complete, heat and evaporate to remove the solvent, and dry to obtain a vanillin-based curing agent containing imine bonds.

3. The synthesis method according to claim 1, characterized in that, The reaction solvent is anhydrous ethanol.

4. A biodegradable epoxy resin thermally conductive composite material, characterized in that, By weight percentage, it comprises 50%-75% epoxy resin raw material, 10%-15% curing agent as described in claim 1, and 10%-40% inorganic thermally conductive filler.

5. The composite material according to claim 1, characterized in that, The inorganic thermally conductive filler is blocky calcium fluoride.

6. The method for preparing the composite material according to claim 4 or 5, characterized in that, Includes the following steps: The curing agent described in claim 1 is dispersed in a small amount of dispersion solvent, mixed with epoxy resin and inorganic thermally conductive filler, stirred at 50-70°C for 1-2 hours, and then dried in a vacuum oven at room temperature for 1-2 hours to remove air bubbles. The mixture is then poured into a mold and cured at 70-90°C for 5-7 hours to obtain a biodegradable epoxy resin thermally conductive composite material.

7. The method according to claim 6, characterized in that, The dispersing solvent is N,N-dimethylformamide, and the epoxy resin is E51 type epoxy resin; the mass ratio of the curing agent to the epoxy resin is 100 (20-60), and the mold is a polytetrafluoroethylene mold.

8. A method for preparing biodegradable epoxy resin, characterized in that, The process includes the following steps: dispersing the curing agent described in claim 1 in a small amount of dispersion solvent, mixing it with epoxy resin at a mass ratio of 100:(20-60), stirring at 60°C for 1-2 hours, removing air bubbles in a vacuum oven at room temperature for 1-2 hours, pouring it into a mold, curing at 70-90°C for 5-7 hours, and then allowing it to cool naturally to obtain a biodegradable epoxy resin.

9. The method for recycling the composite material according to claim 4 or 5, characterized in that, The process includes the following steps: pulverizing the composite material described in claim 4 or 5 into powder, adding a chemical degradation solvent, condensing and refluxing under nitrogen protection at 90°C-160°C, filtering and separating, and recovering the inorganic thermally conductive filler.

10. The recycling method according to claim 9, characterized in that, The chemical degradation solvent is one or more of glacial acetic acid, ethylene glycol, ethylenediamine, and N,N-dimethylformamide.

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