A brick-wall-like epoxy resin composite material based on the recycling and reuse of waste epoxy resin, its preparation method and application

Abstract

This invention discloses a brick-wall structure epoxy resin composite material based on the recycling and reuse of waste epoxy resin, its preparation method, and its application. The brick-wall structure epoxy resin composite material of this invention comprises surface-modified boron nitride tightly encapsulated waste epoxy resin microspheres and an epoxy resin matrix. A brick-wall-like thermally conductive network structure is constructed within the composite material using densely packed boron nitride-epoxy resin microspheres of different particle sizes. The brick-wall structure epoxy resin composite material of this invention achieves high thermal conductivity while also possessing high mechanical strength and high breakdown strength. It broadens the application of epoxy resin recycling strategies and provides a promising direction for novel environmentally friendly thermal management materials. Furthermore, the process is more operable and suitable for industrial application.

Description

Technical Field

[0001] This invention relates to the field of high thermal conductivity epoxy resin composite materials, specifically to a brick-wall-like structure epoxy resin composite material based on the recycling and reuse of waste epoxy resin, its preparation method, and its application. Background Technology

[0002] Thermosetting epoxy resins and their composites play an irreplaceable role in electrical equipment and electronic packaging due to their excellent mechanical and insulating properties. However, with the aging and large-scale decommissioning of old equipment, recycling waste thermosetting epoxy resins and their composites has become an increasingly urgent challenge. Traditional landfill and incineration methods are gradually being abandoned due to resource waste and environmental pollution. Researchers are actively exploring new and efficient strategies for recycling epoxy resins and their composites. Physical recycling and chemical recycling have emerged as two more effective methods for recycling waste epoxy resins to prepare new multifunctional materials in recent years. Chemical recycling methods use dissolution or bond breaking to obtain high-value fiber materials, oligomers, and small molecules, but they are costly and complex, and current research is limited to the laboratory scale, making them unsuitable for industrial application. Physical recycling methods, on the other hand, use shearing, impact, or other forms of mechanical force to decompose waste epoxy resins without destroying their chemical structure. This process is simple and does not produce secondary pollution, making it a promising method for the industrial recycling of waste epoxy resins. However, traditional physical recycling methods are only used to prepare low-value inorganic inert fillers after crushing or cutting. Exploring new strategies to endow waste epoxy resins with high value and transform them into high-performance, high-value-added functional materials is a significant need. Therefore, the physical recycling and reuse of waste thermosetting resins to prepare epoxy composites with high thermal conductivity not only broadens new strategies for thermal management material design but also provides a promising direction for novel environmentally friendly electrical materials.

[0003] Previous epoxy recycling and reuse solutions based on physical crushing, such as those disclosed in patents CN113321201A and CN112829123A, have been problematic. CN113321201A utilizes high-temperature processing, resulting in high energy consumption, and the porous carbon material produced needs to be composited with electrode materials, making the process cumbersome and impractical for engineering implementation. CN112829123A focuses on physical crushing methods and maintaining mechanical properties, without expanding into other properties or directions of epoxy, and the prepared filler can only be used as a low-value filler.

[0004] In summary, developing a novel composite material based on the physical recycling and reuse of waste thermosetting resins is of great significance for promoting the industrialization of thermal management materials. Summary of the Invention

[0005] The purpose of this invention is to provide a brick-wall-type epoxy resin composite material based on the recycling and reuse of waste epoxy resin, its preparation method, and its application.

[0006] The technical solution adopted in this invention is:

[0007] A brick-wall-like epoxy resin composite material based on the recycling and reuse of waste epoxy resin, comprising an epoxy resin matrix and boron nitride-epoxy resin microspheres (WEM@BN). The boron nitride-epoxy resin microspheres consist of waste epoxy microspheres modified internally with a dilute bisphenol A epoxy resin solution and boron nitride nanosheets cured and adhered to the outer surface.

[0008] Boron nitride-epoxy resin microspheres are prepared by the following method:

[0009] 1) Waste epoxy resin is mechanically crushed into epoxy microspheres of 50-900μm using a physical crusher, and then separated into three different particle size ranges of waste epoxy resin microspheres of 100-200μm, 300-400μm and 500-600μm using a sieving method.

[0010] 2) Prepare a dilute epoxy resin solution by mixing epoxy resin, curing agent, accelerator and acetone in a mass ratio of 1:0.85:0.006:0.8-1:0.95:1 for 10-20 minutes. Add waste epoxy resin microspheres of different particle sizes into the dilute solution and mix thoroughly for 20-40 minutes for surface modification.

[0011] 3) The modified epoxy microspheres were extracted by vacuum filtration and mixed with sufficient BN to achieve a tight coating of BN on the surface of the epoxy microspheres. The microspheres were then cured in a heating oven to obtain WEM@BN microspheres.

[0012] Further, in step 2), an epoxy resin matrix mixture solution is prepared, wherein the epoxy resin is at least one of alicyclic epoxy resin and bisphenol A type epoxy resin; the curing agent is methylhexahydrophthalic anhydride; and the accelerator is 2-ethyl-4-methylimidazole.

[0013] Further, in step 3), the mass ratio of boron nitride to the modified epoxy microspheres is 3-6 wt%.

[0014] Furthermore, the reaction temperature in step 3) is 100-120℃, and the reaction time is 1-2.5h.

[0015] Furthermore, in step 3), the thickness of the outer BN layer of the obtained WEM@BN microspheres is 3.6-9.1 μm.

[0016] The method for preparing brick-wall-type epoxy resin composite material based on the recycling and reuse of waste epoxy resin includes the following steps: densely packing WEM@BN microspheres of different particle size ranges and impregnating them in a mixture of epoxy resin, curing agent and accelerator for degassing and high-temperature curing to obtain the corresponding composite material.

[0017] Furthermore, the high-temperature curing conditions are as follows: first, cure at 95℃-115℃ for 40-80 minutes, then cure at 115℃-125℃ for 100-150 minutes, and then cure at 135℃-145℃ for 30-60 minutes.

[0018] The brick-wall-like epoxy resin composite material prepared by this invention, based on the recycling and reuse of waste epoxy resin, has a BN volume fraction of 3.4-8.5 vol% and a waste epoxy microsphere particle size of 100-600 μm.

[0019] This invention relates to a brick-wall structure epoxy resin composite material based on the recycling and reuse of waste epoxy resin. The composite material comprises surface-modified boron nitride-coated waste epoxy resin microspheres and an epoxy resin matrix. A highly engineered physical crushing method is used to process the waste epoxy resin to obtain microspheres of different particle sizes. These microspheres are then surface-modified with a dilute epoxy solution to obtain a core-shell structure of waste epoxy resin-boron nitride microspheres coated with boron nitride. This densely packed boron nitride-epoxy resin microsphere structure of varying particle sizes constructs a brick-wall-like thermally conductive network within the composite material. This brick-wall structure epoxy resin composite material achieves high thermal conductivity while also possessing high mechanical strength and high breakdown strength. It broadens the application of epoxy resin recycling strategies and provides a promising direction for novel environmentally friendly thermal management materials. Furthermore, the process is more operable and suitable for industrial application. The material of this invention can be used to prepare thermal management materials for high-voltage electrical equipment.

[0020] Compared with the prior art, the advantages and beneficial effects of the present invention are:

[0021] (1) This invention directly uses waste epoxy resin as the matrix material for pseudo-surface modified microspheres, which reduces the amount of raw materials and costs while disposing of solid waste, and has good economic and environmental benefits.

[0022] (2) The brick wall structure epoxy resin composite material based on the recycling and reuse of waste epoxy resin of the present invention can prepare epoxy composite materials with large, medium and small particle sizes and multi-particle size waste epoxy microspheres on the basis of realizing the recycling and reuse of waste epoxy resin. It has obtained high breakdown strength, high mechanical properties and high thermal conductivity, and the process is easy to operate and suitable for large-scale industrial application.

[0023] (3) The present invention is based on the brick wall structure epoxy resin composite material of waste epoxy resin recycling and reuse. Waste epoxy microspheres are used as skeleton templates. The boron nitride coated on the surface of the microspheres is used as a thermally conductive network by a close-packed geometric method to construct a thermally conductive "highway". The thermal conductivity of the composite material is greatly improved with a boron nitride filling amount of less than 10 vol%.

[0024] (4) The thermal conductivity of the present invention reaches 3.71 W / m·K with low boron nitride filling amount, and the breakdown strength is as high as 30 kV / mm or more. Attached Figure Description

[0025] Figure 1 This is a schematic diagram of the preparation process of the brick wall-type epoxy resin composite material based on the recycling and reuse of waste epoxy resin according to the present invention.

[0026] Figure 2 SEM images of epoxy resin microspheres and WEM@BN microspheres with different particle sizes.

[0027] Figure 3 Infrared spectra of epoxy resin microspheres and WEM@BN microspheres with different particle sizes.

[0028] Figure 4 Thermogravimetric curves of epoxy resin microspheres and WEM@BN microspheres with different particle sizes are shown.

[0029] Figure 5 SEM images of four different particle size ratios of brick-wall-like epoxy resin composites.

[0030] Figure 6 The graph shows the thermal conductivity test results for four different particle size ratios of brick-wall-type epoxy resin composites, direct-filled BN composites, and pure epoxy resin materials.

[0031] Figure 7 Weibull distribution diagrams of breakdown field strength for four different particle size ratios of brick-wall-type epoxy resin composites, direct-filled BN composites, and pure epoxy resin materials.

[0032] Figure 8 The figures show the dynamic thermomechanical analysis results of four different particle size ratios of brick-wall-type epoxy resin composites, direct-filled BN composites, and pure epoxy resin materials.

[0033] Figure 9 The epoxy resin composites (i.e., EPM / BN) of Examples 1-4 L EPM / BN M EPM / BN S The thermal conductivity simulation model results of EPM / BN1. Detailed Implementation

[0034] The technical solution of the present invention will be further explained below with reference to specific embodiments and accompanying drawings.

[0035] Example 1

[0036] A brick-wall-like epoxy resin composite material based on the recycling and reuse of waste epoxy resin, the preparation method of which includes the following steps (preparation process as follows) Figure 1 As shown):

[0037] 1) Waste epoxy resin is put into a mechanical crusher for physical crushing. The obtained epoxy microspheres of 50-900μm are screened to obtain waste epoxy resin microspheres of three different particle size ranges: 100-200μm, 300-400μm, and 500-600μm.

[0038] 2) Take 20g of bisphenol A epoxy resin, 16g of methyltetrahydrophthalic anhydride, 0.12g of 2-ethyl-4-methylimidazolium and 22mL of acetone and mix them thoroughly for 10min to form a homogeneous mixed solution. Take 20g of large-particle-size (500-600μm) waste epoxy microspheres and add them to the solution. Stir and mix thoroughly for 30min to modify the viscosity of the waste epoxy microsphere surface.

[0039] 3) The modified waste epoxy microspheres were filtered using a Buchner funnel. The modified epoxy microspheres were then added to a beaker along with 15g of hexagonal boron nitride (h-BN) and stirred thoroughly to ensure that BN was fully coated on the outer layer of the epoxy microspheres. The mixed solid was then cured at 110℃ for 2h. After sieving away excess BN, large-particle-size WEM@BN microspheres were obtained.

[0040] 4) Alicyclic epoxy resin, methylhexahydrophthalic anhydride, and 2-ethyl-4-methylimidazole were mixed at a mass ratio of 1:1.2:0.006 and stirred for 20 minutes to prepare an epoxy resin mixture solution. 15g of the prepared large-particle-size WEM@BN microspheres were then impregnated with the epoxy resin mixture solution using a dense packing method. The mixture was then placed in a vacuum chamber at 50°C and vacuumed for 5 hours to achieve complete impregnation. Finally, it was placed in a heating chamber and cured at 110°C for 60 minutes, then at 125°C for 120 minutes, and then at 135°C for 60 minutes to obtain a brick-wall structure epoxy resin composite material based on the recycling and reuse of waste epoxy resin (denoted as EPM / BN). L The BN content was 3.4 vol%.

[0041] Example 2

[0042] A brick-wall-like epoxy resin composite material based on the recycling and reuse of waste epoxy resin, denoted as EPM / BN MThe preparation process is the same as in Example 1, except that in step 2), large-particle-size (500-600μm) waste epoxy microspheres are replaced with medium-particle-size (300-400μm) waste epoxy microspheres. The BN content is 7.4 vol%.

[0043] Example 3

[0044] A brick-wall-like epoxy resin composite material based on the recycling and reuse of waste epoxy resin, denoted as EPM / BN S The preparation process is the same as in Example 1, except that in step 2), large-particle-size (500-600 μm) waste epoxy microspheres are replaced with small-particle-size (100-200 μm) waste epoxy microspheres. The BN content is 6.5 vol%.

[0045] Example 4

[0046] A brick-wall-like epoxy resin composite material based on the recycling and reuse of waste epoxy resin, denoted as EPM / BN1, is prepared by modifying and curing three different particle sizes of waste epoxy microspheres to prepare corresponding WEM@BN microspheres of different particle sizes, based on step 1) of Example 1. A mixed ratio of large, medium, and small WEM@BN microspheres was prepared at a mass ratio of 0.4:0.37:0.23. 6g of large-particle-size WEM@BN microspheres, 5.55g of medium-particle-size WEM@BN microspheres, and 3.45g of small-particle-size WEM@BN microspheres were used. Simultaneously, alicyclic epoxy resin, methylhexahydrophthalic anhydride, and 2-ethyl-4-methylimidazolium were mixed at a mass ratio of 1:1.2:0.006 and stirred for 20 minutes to prepare an epoxy resin mixed solution. Different... WEM@BN microspheres with mixed particle size ratios were impregnated with a mixed epoxy resin solution in a densely packed manner. Then, they were placed in a vacuum chamber at 50°C and vacuumed for 5 hours to achieve complete impregnation. After that, they were placed in a heating chamber and cured at 110°C for 60 minutes, then at 125°C for 120 minutes, and then at 135°C for 60 minutes to obtain a brick wall-like structure epoxy resin composite material (denoted as EPM / BN1) based on the recycling and reuse of waste epoxy resin, with a BN content of 8.5 vol%.

[0047] Comparative Example 1

[0048] A pure epoxy resin material, the preparation method of which includes the following steps:

[0049] 10g of alicyclic epoxy resin, 12g of methylhexahydrophthalic anhydride, and 0.06g of 2-ethyl-4-methylimidazolium were mixed and stirred for 20 minutes to form a homogeneous epoxy resin solution. The solution was then degassed in a vacuum chamber for 1 hour. The solution was then uniformly poured into a stainless steel mold and placed in a heating chamber. The mold was cured at 110°C for 60 minutes, then at 125°C for 120 minutes, and then at 135°C for 60 minutes to obtain pure epoxy resin material (denoted as EP).

[0050] Comparative Example 2

[0051] An epoxy composite material directly filled with boron (BN) is prepared by the following steps:

[0052] 3.9 g of hexagonal boron nitride (h-BN) filler was added to 100 mL of acetone and ultrasonically dispersed for 45 min. Then, 10 g of alicyclic epoxy resin was added and stirred at 65 °C until the acetone was completely evaporated. Next, 12 g of methylhexahydrophthalic anhydride and 0.06 g of 2-ethyl-4-methylimidazole were added and stirred for 20 min to form a homogeneous solution. The solution was then vacuum-soaked in a vacuum chamber for 1 h. After that, it was placed in a heating chamber and cured at 110 °C for 60 min, then at 125 °C for 120 min, and then at 135 °C for 60 min to obtain the epoxy resin composite material directly filled with BN (denoted as EP / BN1) with a boron nitride content of 8.5 vol.

[0053] Performance testing

[0054] 1. SEM images of the epoxy resin microspheres and WEM@BN microspheres prepared in Examples 1-3 are shown below. Figure 2 As shown, the infrared spectrum is as follows Figure 3 As shown, the thermogravimetric curve is as follows Figure 4 As shown.

[0055] Depend on Figure 2 As can be seen, the SEM images of the microspheres coated with h-BN show a completely encapsulated structural feature. In higher magnification SEM images, the layers of h-BN can be clearly seen overlapping and encapsulating the surface of the epoxy microspheres.

[0056] The infrared spectral results of WEM@BN microspheres are as follows: Figure 3 As shown, compared with the infrared results of pure bisphenol A epoxy resin microspheres EP, the infrared spectrum of WEM@BN microspheres at 800 cm⁻¹... -1 and 1380cm -1 A new spectral band was observed, and a comparison with the infrared spectrum of h-BN showed that the appearance of the new spectral band was attributed to the thick h-BN coating on the surface of WEM@BN.

[0057] Figure 4Thermogravimetric analysis (TGA) results of WEM@BN microspheres with different particle sizes and pure bisphenol A epoxy resin showed that, compared to the 4.73% residual mass of pure epoxy resin (EP), the WEM@BN microspheres of large, medium, and small particle sizes had residual masses of 20.72%, 28.97%, and 27.52%, respectively. This indicates that the surfaces of the waste epoxy microspheres of different particle sizes were coated with BN nanosheets of different masses. These three characterization results effectively confirm the successful h-BN encapsulation modification of the WEM surface.

[0058] 2. SEM images of epoxy composite materials with different particle size ratios obtained in Examples 1-4 are shown below. Figure 5 As shown.

[0059] For high thermal conductivity composite materials, constructing an effective thermal conductivity network is crucial. This invention utilizes large, medium, and small particle sizes, and references the closest packing method, to prepare composite materials by blending the three particle sizes in a mass ratio of 0.4:0.37:0.23. The cross-sectional morphology information of the resulting composite materials is shown below. Figure 5 As shown. By Figure 5 The SEM images clearly show that the waste epoxy microspheres provided a template for the formation of thermally conductive filler pathways in the composite material, and an effective high thermal conductivity filler network was built by WEM@BN microspheres of different particle sizes.

[0060] 3. Epoxy resin composite materials (i.e., EPM / BN) in Examples 1-4, Comparative Examples 1 and 2 L EPM / BN M EPM / BN S The thermal conductivity test results of EPM / BN1, EP and EP / BN1 are as follows: Figure 6 As shown.

[0061] Depend on Figure 6 It can be seen that EPM / BN L EPM / BN M EPM / BN SThe thermal conductivity of EPM / BN1, EP, and EP / BN1 are 1.91 W / m·K, 2.19 W / m·K, 2.23 W / m·K, 3.71 W / m·K, 0.2 W / m·K, and 1.51 W / m·K, respectively. This indicates that compared to pure epoxy resin and directly filled epoxy composites, the material structure designed in this invention significantly improves the thermal conductivity of the composite material. The composite materials prepared with large, medium, and small particle sizes and mixed multi-size composite microspheres show thermal conductivity improvements of 850%, 995%, 1015%, and 1755% compared to pure epoxy resin, respectively. These results show that the composite material using different particle sizes exhibits the best thermal conductivity, far exceeding that of pure epoxy resin and BN directly filled epoxy composites. The average BN coating thickness of EM@BN microspheres with three different particle sizes was calculated. The average coating thickness was obtained by combining the average particle size and average specific surface area of ​​the large, medium, and small microspheres with thermogravimetric analysis results and the density results of each composite material. The BN coating thicknesses of the large, medium, and small microspheres were 8.6 μm, 9.1 μm, and 3.6 μm, respectively. Based on this, and combined with... Figure 5 Comparison of SEM images of composite materials prepared directly using WEM@BN microspheres of three particle sizes reveals that, although large-diameter and medium-diameter microspheres maintain similar average coating thicknesses, and BN tightly wraps around WEM in the composite material, forming an effective thermally conductive network, the filler network inside the composite material prepared with large-diameter microspheres is too sparse compared to the medium-diameter WEM@BN epoxy composite material due to the excessively large particle size. Furthermore, the microspheres are less likely to form tight contact, resulting in larger voids and limited thermal conductivity improvement. On the other hand, comparative observation of the test results of small-diameter WEM@BN epoxy composite materials shows that, although small-diameter microspheres form a dense BN thermally conductive filler network within the composite material, compared to large-diameter and medium-diameter microspheres, they introduce more filler-filler and filler-matrix interface contacts, leading to more severe internal interfacial thermal resistance. Under the combined effect of these two factors, the improvement in thermal conductivity is not significant. Based on this, analysis of epoxy composites prepared by combining large, medium and small particle sizes of microspheres shows that the composite material achieves a closer contact effect and obtains a dense BN thermally conductive network by using microspheres of different sizes. At the same time, the interfacial thermal resistance introduced inside is also relatively small, and the thermal conductivity of the final composite material is optimally improved.

[0062] 4. Epoxy resin composite materials (i.e., EPM / BN) in Examples 1-4, Comparative Examples 1 and 2 L EPM / BN M EPM / BN S The breakdown field strength Weibull distributions of EPM / BN1, EP, and EP / BN1 are as follows: Figure 7 As shown.

[0063] right Figure 7 A comprehensive analysis of (a) and (b) shows that, compared to pure epoxy resin, the breakdown field strength of the epoxy resin composite EP / BN1 directly filled with BN is slightly improved, reaching 26.67 kV / mm. BN, as an insulating filler with a breakdown strength as high as 40 kV / mm, effectively suppresses charge transport and blocks the development of electrical trees due to its two-dimensional planar structure; direct filling thus enhances the breakdown strength of epoxy. However, the significant improvement in its shape parameters also reveals the non-uniformity of dispersion within the composite material. The epoxy composites with different particle sizes in Examples 1-4 show even greater improvements in breakdown field strength compared to the directly filled BN epoxy composite. The breakdown strengths of the large, medium, and small particle size and multi-particle size composites reached 32.27 kV / mm, 33.24 kV / mm, 31.58 kV / mm, and 30.9 kV / mm, respectively. At low BN filling levels, by utilizing waste epoxy microspheres as a skeleton template, BN forms more effective connections within the epoxy composite material compared to direct BN filling. This results in a more significant and efficient suppression of charge transport and leakage current, leading to higher breakdown strength at similarly low filling levels. Furthermore, the shape parameter β demonstrates that the epoxy composite material (EPM / BN) based on the recycling of waste epoxy resin of this invention… L EPM / BN M EPM / BN S EPM / BN1) has fewer low-quality defects.

[0064] 5. Epoxy resin composite materials (i.e., EPM / BN) in Examples 1-4, Comparative Examples 1 and 2 L EPM / BN M EPM / BN S The dynamic thermomechanical analysis test results of EPM / BN1, EP and EP / BN1 are as follows: Figure 8 As shown.

[0065] Depend on Figure 8 It can be seen that: EPM / BN L EPM / BN M EPM / BN SThe storage moduli of EPM / BN1, EP, and EP / BN1 were 3411.07 MPa, 2855.12 MPa, 2769.078 MPa, 3982.73 MPa, 1983 MPa, and 2423.3 MPa, respectively. It can be observed that compared to pure epoxy resin and epoxy composites directly filled with BN, the epoxy composites of different particle sizes in Examples 1-4 exhibited higher storage moduli, with the storage moduli increasing sequentially from small to medium to large particle size to multi-particle size composites. Because alicyclic epoxy resin is introduced as the matrix into the composite material, on the one hand, its short-chain structure compared to bisphenol A epoxy resin gives the composite material higher overall stiffness; on the other hand, due to the infiltration of BN-encapsulated microspheres of different particle sizes within the alicyclic epoxy matrix, stronger entanglement between epoxy and BN occurs within the composite material space than in the case of direct filling, thus inhibiting the migration of epoxy molecules to some extent. These two factors together contributed to a significant increase in the energy storage modulus of composite materials prepared from multi-size microspheres.

[0066] 6. Epoxy resin composite materials (i.e., EPM / BN) from Examples 1-4 L EPM / BN M EPM / BN S The thermal conductivity simulation model results of EPM / BN1 are as follows: Figure 9 As shown.

[0067] Depend on Figure 9 It can be known that: Figure 9 The internal heat flux of the four composite materials shown in (a) indicates that microspheres of each particle size are densely packed in the composite material, and the heat flux can be rapidly transferred through the BN thermal conduction path between the epoxy matrix and the waste epoxy microspheres. Figure 9 The heat transfer simulation results of the four composite materials shown in Figure (b) demonstrate that the small-to-medium particle size models have denser heat transfer channels compared to the large-particle-size model. Due to their smaller particle size and smaller distance between fillers, they can form a good heat-conducting network, and the heat transfer efficiency is much higher than that of the large-particle-size model. However, due to the particle size, the small-particle-size model can accumulate a relatively large number of particles, which introduces excessive interfacial thermal resistance, ultimately resulting in less improvement in heat transfer performance compared to the medium-particle-size model. By composited with microspheres of three different particle sizes inside the composite material, the small-particle-size microspheres are distributed between the large and medium-particle-size particles, forming a bridging effect and constructing a more efficient heat-conducting network, exhibiting the best heat transfer efficiency compared to the single-particle-size model. Figure 9 Figure (c) shows a comparison between the simulated thermal conductivity and the measured value, verifying the trend consistent with the measured thermal conductivity. Figure 9 Figure (d) shows the heat transfer effect of the four composite materials. The simulation results further verify the thermal conductivity of the epoxy resin composite materials in Examples 1-4.

Claims

1. A brick-wall-type epoxy resin composite material based on the recycling and reuse of waste epoxy resin, characterized in that, The composite material comprises an epoxy resin matrix and filled boron nitride-epoxy resin microspheres; the boron nitride-epoxy resin microspheres WEM@BN comprise waste epoxy microspheres modified internally by a dilute bisphenol A epoxy resin solution and boron nitride nanosheets cured and adhered to the outer surface; the dilute bisphenol A epoxy resin solution is a homogeneous mixture formed by thoroughly mixing 20g of bisphenol A epoxy resin, 16g of methyltetrahydrophthalic anhydride, 0.12g of 2-ethyl-4-methylimidazolium, and 22mL of acetone for 10min; the curing is carried out at 100-120℃ for 1-2.5h.

2. The brick-wall-type epoxy resin composite material based on the recycling and reuse of waste epoxy resin according to claim 1, characterized in that, The volume fraction of boron nitride in the brick-wall structure epoxy resin composite material based on the recycling and reuse of waste epoxy resin is 3.4-8.5 vol%. The waste epoxy microspheres in the brick-wall structure epoxy resin composite material based on the recycling and reuse of waste epoxy resin are made of large, medium and small particle sizes or multi-particle size blends, and the particle size of the waste epoxy microspheres is in the range of 100-600 μm.

3. The brick-wall-type epoxy resin composite material based on the recycling and reuse of waste epoxy resin according to claim 1, characterized in that, WEM@BN microspheres were prepared by the following method: 1) Waste epoxy resin is mechanically crushed into particles of 50-900μm using a crusher, and then screened to obtain waste epoxy microspheres with different particle sizes of 100-600μm. 2) Surface modification of waste epoxy resin microspheres of different particle sizes after mechanical crushing and sieving was carried out using a dilute acetone solution of bisphenol A epoxy resin. 3) The modified epoxy microspheres and boron nitride were thoroughly mixed and mechanically stirred for 5-30 minutes, and then cured in a heating oven to obtain WEM@BN microspheres.

4. The brick-wall-type epoxy resin composite material based on the recycling and reuse of waste epoxy resin according to claim 3, characterized in that, In step 2), the waste epoxy microspheres must be thoroughly mixed and stirred in a dilute acetone solution of bisphenol A epoxy resin for 40-80 minutes, and then quickly filtered.

5. The brick-wall-type epoxy resin composite material based on the recycling and reuse of waste epoxy resin according to claim 3, characterized in that, In step 3), the mass ratio of boron nitride to the modified epoxy microspheres is 3-6 wt%.

6. The brick-wall-type epoxy resin composite material based on the recycling and reuse of waste epoxy resin according to claim 3, characterized in that, The thickness of the outer BN layer of the obtained WEM@BN microspheres was 3.6-9.1 μm.

7. The method for preparing a brick-wall-type epoxy resin composite material based on the recycling and reuse of waste epoxy resin as described in any one of claims 1-6, characterized in that, Includes the following steps: WEM@BN microspheres are densely packed in a mixture of epoxy resin, curing agent and accelerator, and then degassed and cured to obtain the corresponding composite material.

8. The preparation method according to claim 7, characterized in that, The epoxy resin is at least one of alicyclic epoxy resin and bisphenol A type epoxy resin; the curing agent is methylhexahydrophthalic anhydride; and the accelerator is 2-ethyl-4-methylimidazole.

9. The preparation method according to claim 7, characterized in that, The curing conditions are as follows: first, cure at 95℃-115℃ for 40-80 minutes, then cure at 115℃-125℃ for 100-150 minutes, and then cure at 135℃-145℃ for 30-60 minutes.

10. The application of a brick-wall-type epoxy resin composite material based on the recycling and reuse of waste epoxy resin as described in any one of claims 1-6, or a brick-wall-type epoxy resin composite material based on the recycling and reuse of waste epoxy resin obtained by the preparation method described in any one of claims 7-9, in the preparation of thermal management materials for high-voltage electrical equipment.

Images