Epoxy resin encapsulating material with high dielectric constant and preparation method thereof

Abstract

The invention relates to the technical field of epoxy resin encapsulating materials and preparation, in particular to an epoxy resin encapsulating material with a high dielectric constant and a preparation method of the epoxy resin encapsulating material. The epoxy resin encapsulating material comprises the following raw materials in parts by weight: 90-100 parts of bisphenol A epoxy resin, 30-50 parts of dielectric filler, 1-3 parts of modified carbon nanotubes, 5-8 parts of ionic liquid, 25-30 parts of a curing agent, 1-3 parts of a flatting agent and 2-4 parts of an anti-settling agent. The epoxy resin encapsulating material prepared by taking the epoxy resin, the dielectric filler and the modified carbon nanotubes as main raw materials has high dielectric constant, low dielectric loss and good mechanical properties. The dielectric constant and compressive strength of the material can be improved through the barium titanate nanowires with the high length-diameter ratio, interface defects can be reduced through the reaction of the modified carbon nanotubes and the epoxy resin, the dielectric constant of the material is jointly improved, and meanwhile the dispersity of the material in matrix distribution is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of epoxy resin potting materials and their preparation, and particularly relates to a high-dielectric-constant epoxy resin potting material and a preparation method thereof. Background Art

[0002] Epoxy resin is widely used in the field of electronic packaging due to its excellent mechanical properties, thermal properties, corrosion resistance, and obvious price advantages. Epoxy resin enhances the integrity of the potted device, improves the ability to resist external impacts, and simultaneously plays the roles of insulation, waterproofing, and acid and alkali corrosion resistance, thereby ensuring the structural stability and use reliability of the packaged device. However, at present, electronic devices are advancing rapidly towards the direction of miniaturization, integration, and high frequency, and this trend also poses more stringent requirements on the performance of electronic packaging materials, especially in key indicators such as dielectric constant, high-voltage loss, and mechanical properties. Among them, for capacitors, sensors, etc., high-dielectric-constant packaging materials are required to achieve efficient electrical energy storage and signal transmission. However, the dielectric constant of ordinary epoxy resin is relatively low, generally around 3 - 4, which is difficult to meet the requirements of these components for high capacitance density and rapid response; and under the action of a high-voltage electric field, the phenomena of increased polarization loss and conductance loss are likely to occur. Therefore, in order to increase the dielectric constant of epoxy resin, it is usually achieved by adding high-dielectric-constant fillers, but this method often leads to an increase in the high-voltage loss of the material and also damages the mechanical properties of the material. This results in the difficulty for existing epoxy resin potting materials to achieve a good balance among dielectric constant, high-voltage loss, and mechanical properties, and thus they cannot meet the urgent needs of modern electronic devices for high-performance packaging materials.

[0003] Therefore, developing an epoxy resin potting material that can simultaneously possess high dielectric constant, low high-voltage loss, and excellent mechanical properties has great practical significance and broad application prospects. Summary of the Invention

[0004] The purpose of the present invention is to provide a high-dielectric-constant epoxy resin potting material and a preparation method thereof to solve the above-mentioned deficiencies of the prior art.

[0005] The purpose of the present invention is achieved by the following technical solutions: A high-dielectric-constant epoxy resin potting material, comprising the following raw materials in parts by weight: 90 - 100 parts of bisphenol A epoxy resin, 30 - 50 parts of dielectric filler, 1 - 3 parts of modified carbon nanotubes, 5 - 8 parts of ionic liquid, 25 - 30 parts of curing agent, 1 - 3 parts of leveling agent, and 2 - 4 parts of anti-settling agent.

[0006] Further, the dielectric filler is barium titanate nanowires, and the preparation method of the barium titanate nanowires comprises the following steps:

[0007] Step A1: Reflux mesoporous carbon CMK-3 in concentrated nitric acid for 5-6 h, wash and dry it for later use;

[0008] Step A2: Place tetrabutyl titanate in acetylacetone and mix well to obtain a titanium complex. Then, add barium hydroxide and polyacrylic acid to ethylene glycol and dissolve them fully. After adding the titanium complex, ultrasonically disperse them together and adjust the pH of the system to 12;

[0009] Step A3: Add the mesoporous carbon CMK-3 obtained in Step A1 to the solution obtained in Step A2, transfer it to a reaction kettle, react at 180-185 °C for 20-24 h, and apply a DC electric field of 1 kV / cm;

[0010] Step A4: React the reaction product in a hydrofluoric acid solution for 36-48 h, then centrifuge and wash it until neutral. After drying, anneal it at 600-650 °C for 1-2 h to obtain the barium titanate nanowires.

[0011] Furthermore, the aspect ratio of the barium titanate nanowires is 100-300.

[0012] In the present invention, through the combined action of the mesoporous carbon hard template and the polyacrylic acid soft template, the barium titanate crystal grows along the pore axis due to confinement and promotes orientation connection, resulting in nanowires with a high aspect ratio. Under the action of an electric field, the nanowires are oriented, further enhancing its dielectric constant. On the other hand, the barium titanate nanowires with a high aspect ratio have a large contact area with the epoxy resin, and the interfacial polarization effect is more significant, which helps to improve the tensile strength and toughness of the epoxy resin material.

[0013] Furthermore, in order to improve the dispersibility of the barium titanate nanowires, they are pretreated before use. The specific steps are as follows: Place the barium titanate nanowires in an ethanol solution containing 3-aminopropyltriethoxysilane, ultrasonically treat them at 60-65 °C for 1-2 h, centrifuge and wash them, and then dry them for later use. In the present invention, by pretreating the barium titanate nanowires, the covalent bonding with the epoxy resin can be enhanced, and they can be uniformly dispersed in the epoxy resin matrix.

[0014] Further, the preparation method of the modified carbon nanotubes includes the following steps: Disperse a triblock copolymer of polyethylene oxide-polypropylene oxide-polyethylene oxide, urea, and trimethyl borate with a mass ratio of 3-3.5:1:1.8-2 in deionized water, and then transfer it to an oven to dry to obtain a precursor. Place the precursor in a tubular furnace under a nitrogen atmosphere, first calcine it at 750-800 °C for 0.5-1 h, and then calcine it at 800-900 °C for 0.5-2 h to obtain the modified carbon nanotubes.

[0015] Further, the preparation method of the modified carbon nanotubes further includes: placing the obtained modified carbon nanotubes in a sulfuric acid / nitric acid mixture and ultrasonically treating them for 1-3 h, centrifuging, washing, and drying them, then dispersing them in thionyl chloride, heating under reflux for 3-4 h, washing them multiple times with anhydrous dimethylformamide, dispersing the obtained product and ethylenediamine in dimethylformamide, and reacting them at 75-80 °C for 20-24 h, and finally washing them multiple times with ethanol and drying them to obtain amino-functionalized modified carbon nanotubes.

[0016] In the present invention, through the synergistic effect of boron and nitrogen doping, the charge distribution and electronic structure of carbon nanotubes can be adjusted, significantly improving the dielectric constant of the epoxy resin encapsulation material; furthermore, by subjecting its surface to amino-functionalization treatment, its dispersibility in the epoxy resin matrix is improved, reducing agglomeration, and at the same time reacting with the epoxy resin to enhance interfacial polarization. The obtained modified carbon nanotubes have an obvious dielectric constant enhancement effect and low loss.

[0017] Further, the ionic liquid is 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide.

[0018] Further, the curing agent is at least one of a modified amine curing agent, an alicyclic amine curing agent, and an imidazole curing agent. Preferably, the curing agent is triethylenetetramine in the present invention.

[0019] Further, the leveling agent is at least one of a polyether-modified silicone, a silane coupling agent, and an acrylate leveling agent. Preferably, the leveling agent is a polyether-modified silicone in the present invention.

[0020] Further, the anti-settling agent is hydrophobic fumed silica or bentonite.

[0021] The present invention provides a preparation method of the above-mentioned epoxy resin encapsulation material with high dielectric constant, including the following preparation steps:

[0022] Step S1: Pre-mix the modified carbon nanotubes and 1 / 3 of the formulated amount of the ionic liquid, and form a stable slurry by ball milling;

[0023] Step S2: Heat the bisphenol A epoxy resin to 50-55 °C, add the dielectric filler and the slurry obtained in step S1, and grind them evenly with a three-roll mill;

[0024] Step S3: Sequentially add the remaining ionic liquid, the leveling agent, and the anti-settling agent, and continue stirring for 20-30 min, then perform vacuum defoaming to obtain a mixed slurry;

[0025] Step S4: Inject the mixed slurry obtained in step S3 into a pre-prepared mold and perform gradient temperature curing to obtain the epoxy resin encapsulation material with high dielectric constant.

[0026] Further, in step S4, the gradient temperature rise curing is specifically as follows: in the first stage, it is cured at 40 - 50 °C for 1 - 2 h, in the second stage, it is cured at 70 - 80 °C for 1 - 2 h, and in the third stage, it is cured at 110 - 120 °C for 1 - 3 h.

[0027] Further, the gradient temperature rise curing further includes a fourth stage of curing at 140 - 150 °C for 20 - 30 min.

[0028] Further, it also includes applying a 1 kV / mm DC electric field in the second stage of step S4, and making the barium titanate nanowires align along the electric field direction through the action of the electric field.

[0029] The beneficial effects of the present invention are as follows: The present invention provides a high - dielectric - constant epoxy resin potting material and its preparation method. The epoxy resin potting material prepared with epoxy resin, dielectric filler, and modified carbon nanotubes as the main raw materials has high dielectric constant, low dielectric loss, and good mechanical properties. Among them, the barium titanate nanowires with high aspect ratio can both improve the dielectric constant and compressive strength of the material, while the reaction between the modified carbon nanotubes and the epoxy resin can reduce the interfacial defects. The high aspect ratio and excellent electrical properties of the carbon nanotubes further enhance the polarization ability of the material. Acting synergistically with the barium titanate nanowires, they jointly improve the dielectric constant of the material, and at the same time improve the dispersion in the matrix, which also helps to improve the tensile strength and toughness of the material. Furthermore, using ionic liquid as a polarization enhancer helps to reduce the dielectric loss of the epoxy resin potting material; using a leveling agent and an anti - settling agent to improve the processing performance and storage stability of the material; and realizing medium - and low - temperature curing by adding a curing agent to improve the process stability. Specific Embodiments

[0030] For the convenience of understanding by those skilled in the art, the present invention will be further described below in conjunction with embodiments. The content mentioned in the embodiments does not limit the present invention.

[0031] Example 1

[0032] This example provides a high - dielectric - constant epoxy resin potting material, including the following raw materials in parts by weight: 90 parts of bisphenol A epoxy resin, 30 parts of dielectric filler, 1 part of modified carbon nanotubes, 5 parts of ionic liquid, 25 parts of curing agent, [X] parts of leveling agent, and 2 parts of anti - settling agent.

[0033] Further, the dielectric filler is barium titanate nanowires, and the preparation method of the barium titanate nanowires includes the following steps:

[0034] Step A1: Reflux 0.5 g of mesoporous carbon CMK - 3 in 65% concentrated nitric acid for 5 h, wash and dry it for later use;

[0035] Step A2: Tetrabutyl titanate was placed in acetylacetone and mixed thoroughly in a molar ratio of 1:2 to obtain a titanium complex. Then, 10 mmol of barium hydroxide and 0.1 g of polyacrylic acid were successively added to 60 mL of ethylene glycol and dissolved completely. After adding the titanium complex, the mixture was ultrasonically dispersed for 10 min, and the pH of the system was adjusted to 12.

[0036] Step A3: The mesoporous carbon CMK-3 obtained in Step A1 was added to the solution obtained in Step A2, transferred to a reaction kettle, and reacted at 180 °C for 24 h with an external electric field of 1 kV / cm.

[0037] Step A4: The reaction product was reacted in a 5% hydrofluoric acid solution for 36 h, then centrifuged and washed until neutral. After drying, it was annealed at 600 °C for 2 h to obtain the barium titanate nanowires.

[0038] Furthermore, in order to improve the dispersibility of the barium titanate nanowires, they were pretreated before use. The specific steps were as follows: The barium titanate nanowires were placed in a 2% ethanol solution containing 3-aminopropyltriethoxysilane at a solid-liquid ratio of 1:50, ultrasonically treated at 60 °C for 2 h, centrifuged, washed, and dried for standby.

[0039] Further, the preparation method of the modified carbon nanotubes includes the following steps: Polyethylene oxide-polypropylene oxide-polyethylene oxide triblock copolymer, urea, and trimethyl borate with a mass ratio of 3:1:1.8 were dispersed evenly in 50 mL of deionized water, and then transferred to an 80 °C oven to be dried to obtain a precursor. The precursor was placed in a tube furnace under a nitrogen atmosphere, first calcined at 750 °C for 1 h, and then calcined at 800 °C for 2 h to obtain the modified carbon nanotubes.

[0040] Furthermore, the preparation method of the modified carbon nanotubes also includes: 1 g of the obtained modified carbon nanotubes was placed in 40 mL of a sulfuric acid / nitric acid mixture (3:1) and ultrasonically treated for 1 h. After centrifugation, washing, and drying, it was dispersed in thionyl chloride, heated under reflux for 4 h, washed repeatedly with anhydrous dimethylformamide. The obtained product was dispersed in dimethylformamide with ethylenediamine and reacted at 75 °C for 24 h. After washing with ethanol and drying multiple times, the amino-functionalized modified carbon nanotubes were obtained.

[0041] Further, the ionic liquid is 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide.

[0042] Further, the curing agent is isophorone diamine.

[0043] Further, the leveling agent is silane coupling agent KH-560.

[0044] Further, the anti-settling agent is bentonite.

[0045] This embodiment provides a preparation method of the above-mentioned epoxy resin potting material with high dielectric constant, including the following preparation steps:

[0046] Step S1: Pre-mix the modified carbon nanotubes and 1 / 3 of the formulated amount of ionic liquid, and form a stable slurry through ball milling.

[0047] Step S2: Heat the bisphenol A epoxy resin to 50°C, add the dielectric filler and the slurry obtained in Step S1, and grind evenly with a three-roll mill.

[0048] Step S3: Sequentially add the remaining ionic liquid, leveling agent and anti-settling agent, continue stirring for 20 min, keep the vacuum degree below 0.1 MPa for vacuum degassing to obtain a mixed slurry.

[0049] Step S4: Inject the mixed slurry obtained in Step S3 into a pre-prepared mold for gradient temperature curing to obtain the epoxy resin potting material with high dielectric constant.

[0050] Furthermore, in Step S4, the gradient temperature curing is specifically as follows: the first stage cures at 40°C for 1 h, the second stage cures at 70°C for 2 h, and the third stage cures at 110°C for 3 h.

[0051] Example 2

[0052] This embodiment provides an epoxy resin potting material with high dielectric constant, including the following raw materials in parts by weight: 95 parts of bisphenol A epoxy resin, 40 parts of dielectric filler, 2 parts of modified carbon nanotubes, 6 parts of ionic liquid, 27 parts of curing agent, 3 parts of leveling agent, and 3 parts of anti-settling agent.

[0053] Further, the dielectric filler is barium titanate nanowires, and the preparation method of the barium titanate nanowires includes the following steps:

[0054] Step A1: Reflux 0.5 g of mesoporous carbon CMK-3 in 65% concentrated nitric acid for 6 h, wash and dry for later use.

[0055] Step A2: Place tetrabutyl titanate in acetylacetone in a molar ratio of 1:2 and mix well to obtain a titanium complex. Then, sequentially add 10 mmol of barium hydroxide and 0.1 g of polyacrylic acid to 60 mL of ethylene glycol and dissolve them fully. After adding the titanium complex, ultrasonically disperse them together for 10 min, and adjust the pH of the system to 12.

[0056] Step A3: Add the mesoporous carbon CMK-3 obtained in Step A1 to the solution obtained in Step A2, transfer it to a reaction kettle, react at 180°C for 24 h, and apply an external electric field of 1 kV / cm.

[0057] Step A4: React the reaction product in a 5% hydrofluoric acid solution for 48 h, then centrifuge and wash until neutral, and anneal at 600 °C for 2 h after drying to obtain the barium titanate nanowires.

[0058] Furthermore, in order to improve the dispersibility of the barium titanate nanowires, they are pretreated before use. The specific steps are as follows: Place the barium titanate nanowires in an ethanol solution containing 3-aminopropyltriethoxysilane at 3% according to a solid-liquid ratio of 1:50, and ultrasonically treat for 2 h at 60 °C. After centrifuging and washing, dry and reserve for use.

[0059] Further, the preparation method of the modified carbon nanotubes includes the following steps: Disperse a triblock copolymer of polyethylene oxide-polypropylene oxide-polyethylene oxide, urea, and trimethyl borate with a mass ratio of 3.5:1:2 in 50 mL of deionized water evenly, then transfer to an oven at 80 °C to dry to obtain a precursor. Place the precursor in a tube furnace under a nitrogen atmosphere, first calcine at 800 °C for 1 h, and then calcine at 850 °C for 1.5 h to obtain the modified carbon nanotubes.

[0060] Furthermore, the preparation method of the modified carbon nanotubes also includes: Place 1 g of the obtained modified carbon nanotubes in a sulfuric acid / nitric acid mixed solution (3:1) of 40 mL and ultrasonically treat for 2 h. After centrifuging, washing, and drying, disperse it in thionyl chloride, heat and reflux for 3.5 h, wash with anhydrous dimethylformamide multiple times. Disperse the obtained product and ethylenediamine in dimethylformamide and react at 80 °C for 24 h. After washing with ethanol multiple times and drying, obtain the amino-functionalized modified carbon nanotubes.

[0061] Further, the ionic liquid is 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide.

[0062] Further, the curing agent is triethylenetetramine.

[0063] Further, the leveling agent is polyether-modified silicone.

[0064] Further, the anti-settling agent is hydrophobic fumed silica.

[0065] This embodiment provides a preparation method of the above high-dielectric-constant epoxy resin potting material, including the following preparation steps:

[0066] Step S1: Pre-mix the modified carbon nanotubes and 1 / 3 of the formulated amount of the ionic liquid, and form a stable slurry by ball milling;

[0067] Step S2: Heat the bisphenol A epoxy resin to 55 °C, add the dielectric filler and the slurry obtained in Step S1, and grind evenly with a three-roll mill;

[0068] Step S3: Sequentially add the remaining ionic liquid, leveling agent, and anti-settling agent, and continue stirring for 30 min. Keep the vacuum degree below 0.1 MPa for vacuum defoaming to obtain a mixed slurry.

[0069] Step S4: Inject the mixed slurry obtained in Step S3 into a pre-prepared mold for gradient temperature curing to obtain the epoxy resin potting material with high dielectric constant.

[0070] Furthermore, in Step S4, the gradient temperature curing specifically is: curing at 45 °C for 1.5 h in the first stage, curing at 75 °C for 1 h in the second stage, and curing at 115 °C for 2 h in the third stage.

[0071] Furthermore, it also includes applying a 1 kV / mm DC electric field in the second stage of Step S4, and making the barium titanate nanowires align along the electric field direction through the action of the electric field.

[0072] Example 3

[0073] This example provides an epoxy resin potting material with high dielectric constant, which includes the following raw materials in parts by weight: 100 parts of bisphenol A epoxy resin, 45 parts of dielectric filler, 3 parts of modified carbon nanotubes, 8 parts of ionic liquid, 28 parts of curing agent, 3 parts of leveling agent, and 3 parts of anti-settling agent.

[0074] Further, the dielectric filler is barium titanate nanowires, and the preparation method of the barium titanate nanowires includes the following steps:

[0075] Step A1: Reflux 0.5 g of mesoporous carbon CMK-3 in 65% concentrated nitric acid for 5 h, wash and dry it for later use.

[0076] Step A2: Place tetrabutyl titanate in acetylacetone according to a molar ratio of 1:2 and mix well to obtain a titanium complex. Then, sequentially add 10 mmol of barium hydroxide and 0.1 g of polyacrylic acid to 60 mL of ethylene glycol and dissolve them fully. After adding the titanium complex, ultrasonically disperse them together for 10 min, and adjust the pH of the system to 12.

[0077] Step A3: Add the mesoporous carbon CMK-3 obtained in Step A1 to the solution obtained in Step A2, transfer it to a reaction kettle, react at 185 °C for 22 h, and apply an external electric field of 1 kV / cm.

[0078] Step A4: React the reaction product in a 5% hydrofluoric acid solution for 36 h, then centrifuge and wash it to neutral, dry it, and anneal it at 650 °C for 1.5 h to obtain the barium titanate nanowires.

[0079] Furthermore, in order to improve the dispersibility of barium titanate nanowires, they are pretreated before use. The specific steps are as follows: Place barium titanate nanowires in an ethanol solution containing 2% 3-aminopropyltriethoxysilane at a solid-liquid ratio of 1:50, ultrasonically treat for 2 h at 60 °C, centrifuge, wash, and then dry for standby.

[0080] Further, the preparation method of the modified carbon nanotubes includes the following steps: Disperse poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) triblock copolymer, urea, and trimethyl borate with a mass ratio of 3.5:1:1.9 in 50 mL of deionized water evenly, then transfer to an oven at 80 °C to dry and obtain a precursor. Place the precursor in a tube furnace under a nitrogen atmosphere, first calcine at 800 °C for 0.5 h, and then calcine at 900 °C for 2 h to obtain the modified carbon nanotubes.

[0081] Furthermore, the preparation method of the modified carbon nanotubes also includes: Place 1 g of the obtained modified carbon nanotubes in 40 mL of a sulfuric acid / nitric acid mixture (3:1), ultrasonically treat for 2 h, after centrifuging, washing, and drying, disperse them in thionyl chloride, heat and reflux for 3.5 h, wash with anhydrous dimethylformamide multiple times, disperse the obtained product and ethylenediamine in dimethylformamide, and react at 75 °C for 24 h. After washing with ethanol multiple times and drying, the amino-functionalized modified carbon nanotubes are obtained.

[0082] Further, the ionic liquid is 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide.

[0083] Further, the curing agent is 2-ethyl-4-methylimidazole.

[0084] Further, the leveling agent is polyether-modified silicone.

[0085] Further, the anti-settling agent is hydrophobic fumed silica.

[0086] The present invention provides a preparation method of the above-mentioned epoxy resin potting material with high dielectric constant, including the following preparation steps:

[0087] Step S1: Pre-mix the modified carbon nanotubes and 1 / 3 of the formulated amount of ionic liquid, and form a stable slurry by ball milling;

[0088] Step S2: Heat bisphenol A epoxy resin to 50 °C, add dielectric fillers and the slurry obtained in Step S1, and grind evenly with a three-roll mill;

[0089] Step S3: Sequentially add the remaining ionic liquid, leveling agent, and anti-settling agent, continue stirring for 30 min, keep the vacuum degree below 0.1 MPa for vacuum degassing to obtain a mixed slurry;

[0090] Step S4: Inject the mixed slurry obtained in Step S3 into a pre-prepared mold for gradient temperature curing to obtain the epoxy resin potting material with high dielectric constant.

[0091] Further, in Step S4, the gradient temperature curing specifically is: curing at 50°C for 1 h in the first stage, curing at 0°C for 2 h in the second stage, and curing at 120°C for 2 h in the third stage.

[0092] Further, it also includes applying a 1 kV / mm DC electric field in the second stage of Step S4, and making the barium titanate nanowires align along the electric field direction through the action of the electric field.

[0093] Comparative Example 1

[0094] The difference between this comparative example and Example 2 is that commercially available barium titanate (Shandong Guohua Chemical Co., Ltd.) is used to replace the barium titanate nanowires in Example 2.

[0095] Comparative Example 2

[0096] The difference between this comparative example and Example 2 is that commercially available carbon nanotubes (Jiangsu Xianfeng Nanomaterials Technology Co., Ltd.) are used to replace the amino-functionalized modified carbon nanotubes in Example 2.

[0097] Comparative Example 3

[0098] The difference between this comparative example and Example 2 is that the preparation method of the modified carbon nanotubes includes the following steps: Dispersing a triblock copolymer of polyethylene oxide - polypropylene oxide - polyethylene oxide, urea, and trimethyl borate with a mass ratio of 3 - 3.5:1:1.8 - 2 evenly in deionized water, then transferring it to an oven to dry to obtain a precursor, placing the precursor in a tube furnace under a nitrogen atmosphere, first roasting at 750 - 800°C for 0.5 - 1 h, and then roasting at 800 - 900°C for 0.5 - 2 h to obtain the modified carbon nanotubes.

[0099] Comparative Example 4

[0100] The difference between this comparative example and Example 2 is that this comparative example provides an epoxy resin potting material with high dielectric constant, including the following raw materials in parts by weight: 95 parts of bisphenol A epoxy resin, 40 parts of dielectric filler, 2 parts of modified carbon nanotubes, 6 parts of ionic liquid, 27 parts of curing agent, 3 parts of leveling agent, and 3 parts of anti-settling agent.

[0101] The present invention conducts performance tests on the epoxy resin potting materials prepared in Examples 1 - 3 and Comparative Examples 1 - 4. Among them, the dielectric constant and dielectric loss factor are tested according to ASTM D150, the breakdown strength is tested according to IEC 60243, the tensile strength is tested according to ASTM D638, and the flexural strength is tested according to ASTM D790. The specific test results are shown in the following table.

[0102]

[0103]

[0104] As can be seen from the data in the above table, the epoxy resin potting materials prepared in Examples 1 - 3 of the present invention have a relatively high dielectric constant and extremely low dielectric loss, while maintaining good mechanical properties. Among them, by introducing barium titanate nanowires with a high aspect ratio and improving the oriented arrangement of the fillers under the action of an electric field, a complete three-dimensional dielectric network is constructed, and through synergistic action with amino-functionalized carbon nanotubes, low dielectric loss and high interfacial bonding force are achieved, while the mechanical properties of the epoxy resin potting material are not affected.

[0105] The above specific embodiments further illustrate the technical solutions and beneficial effects of the present invention, rather than limiting the implementation manners. For those skilled in the art, any obvious substitution without departing from the concept of the present invention is within the protection scope of the present invention.

Claims

1. An epoxy resin potting material with a high dielectric constant, characterized in that: It comprises the following raw materials in parts by weight: 90 - 100 parts of bisphenol A epoxy resin, 30 - 50 parts of dielectric filler, 1 - 3 parts of modified carbon nanotubes, 5 - 8 parts of ionic liquid, 25 - 30 parts of curing agent, 1 - 3 parts of leveling agent, and 2 - 4 parts of anti - settling agent.

2. The epoxy resin potting material with high dielectric constant according to claim 1, characterized in that: The dielectric filler is barium titanate nanowires.

3. The high-dielectric-constant epoxy resin potting material according to claim 2, characterized in that: The aspect ratio of the barium titanate nanowires is 100 - 300.

4. The high-dielectric-constant epoxy resin potting material according to claim 1, characterized in that: The preparation method of the modified carbon nanotubes comprises the following steps: Polyethylene oxide - polypropylene oxide - polyethylene oxide triblock copolymer, urea and trimethyl borate with a mass ratio of 3 - 3.5:1:1.8 - 2 are dispersed evenly in deionized water, and then transferred to an oven for drying to obtain a precursor. The precursor is placed in a tubular furnace under a nitrogen atmosphere, first calcined at 750 - 800 °C for 0.5 - 1 h, and then calcined at 800 - 900 °C for 0.5 - 2 h to obtain the modified carbon nanotubes.

5. The epoxy resin potting material with high dielectric constant according to claim 4, characterized in that: The preparation method of the modified carbon nanotubes further comprises: The obtained modified carbon nanotubes are ultrasonicated in a sulfuric acid / nitric acid mixture for 1 - 3 h, centrifuged, washed and dried, then dispersed in SOCl2, heated under reflux for 3 - 4 h, washed repeatedly with anhydrous DMF. The obtained product and ethylenediamine are dispersed in DMF and reacted at 75 - 80 °C for 20 - 24 h, and after being washed and dried with ethanol for many times, amino - modified carbon nanotubes are obtained.

6. The high-dielectric-constant epoxy resin potting material according to claim 1, wherein: The ionic liquid is 1 - ethyl - 3 - methylimidazolium bis(trifluoromethylsulfonyl)imide.

7. The high-dielectric-constant epoxy resin potting material according to claim 1, wherein: The curing agent is at least one of modified amine curing agent, alicyclic amine curing agent, and imidazole - type curing agent.

8. The epoxy resin potting material with high dielectric constant according to claim 1, characterized in that: The leveling agent is at least one of polyether - modified silicone, silane coupling agent, and acrylate - type leveling agent.

9. The high-dielectric-constant epoxy resin potting material according to claim 1, characterized in that: The anti - settling agent is hydrophobic fumed silica or bentonite.

10. The high-dielectric-constant epoxy resin potting material according to any one of claims 1-9, characterized in that: It comprises the following preparation steps: Step S1: The modified carbon nanotubes and 1 / 3 of the formulated amount of ionic liquid are pre - mixed and ball - milled to form a stable slurry. Step S2: The bisphenol A epoxy resin is heated to 50 - 55 °C, the dielectric filler and the slurry obtained in step S1 are added, and they are uniformly milled by a three - roll mill. Step S3: The remaining ionic liquid, leveling agent and anti - settling agent are added in sequence and stirred for 20 - 30 min, and then vacuum - degassed to obtain a mixed slurry. Step S4: The mixed slurry obtained in step S3 is injected into a pre - prepared mold and cured by gradient heating to obtain the high - dielectric - constant epoxy resin potting material.

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