Epoxy resin composite material with high strength and low dielectric loss and preparation method thereof

Abstract

The invention relates to the technical field of rubber materials, in particular to a high-strength and low-dielectric-loss epoxy resin composite material and a preparation method thereof. The epoxy resin composite material is prepared from the following raw materials in parts by weight: 100 parts of modified epoxy resin, 12 to 18 parts of cyanate ester resin, 40 to 50 parts of aramid fiber, 10 to 15 parts of filler, 15 to 25 parts of flexibilizer, 1 to 6 parts of first curing agent and 1 to 2 parts of accelerant. The epoxy resin composite material with high strength and low dielectric loss has the advantages of high strength, good impact resistance, high breakdown strength, low dielectric constant and low dielectric loss. The requirements of high-voltage power transmission equipment insulation parts, high-frequency circuit substrates, spacecraft lightweight structural members and the like on the fields with strict requirements on mechanical strength and dielectric properties can be met; and the preparation method is simple and controllable, the production cost is relatively low, and large-scale production can be realized.

Description

Technical Field

[0001] The present invention relates to the technical field of rubber materials, and particularly relates to a high-strength and low-dielectric-loss epoxy resin composite material and a preparation method thereof. Background Art

[0002] As a high-performance thermosetting resin, epoxy resin has excellent insulation performance, mechanical properties, thermal stability, strong adhesion, corrosion resistance and easy processability due to the close connection of its internal molecular structure, and is widely used in packaging materials for printed circuit boards and electronic devices. With the development of electronic devices, motors, etc. towards miniaturization and high power, higher requirements for low dielectric loss of insulation packaging materials have been put forward. The dielectric properties of epoxy resin (the dielectric constant and dielectric loss value are about 4.0 and 0.018 respectively) cannot meet the needs of current electronic products. Chinese Patent with application number 202410999896.2 discloses a preparation method and application of a medium-temperature-curing high-temperature-resistant low-dielectric epoxy resin. This preparation method uses an alicyclic diluent and cyanate resin to prepare a cyanate oligomer, further reacts a multi-functional epoxy resin with the cyanate oligomer, and then carries out a copolymerization reaction in the presence of an activator to prepare a soluble cyanate-modified multi-functional epoxy resin, and then compound it with a latent curing agent and a promoter to obtain a high-temperature-resistant low-dielectric epoxy resin; however, the mechanical strength of this type of low-dielectric epoxy resin is relatively low and will be limited due to insufficient mechanical strength in actual applications.

[0003] Therefore, how to improve the mechanical properties and breakdown strength while maintaining low dielectric of the composite material is an important issue for the preparation of epoxy resin composite materials. Summary of the Invention

[0004] The purpose of the present invention is to provide a high-strength and low-dielectric-loss epoxy resin composite material and a preparation method thereof to solve the above-mentioned deficiencies of the prior art. The epoxy resin composite material has high strength, good impact resistance, and at the same time has high breakdown strength, low dielectric constant and low dielectric loss, and can meet the requirements of fields such as insulation components of high-voltage transmission equipment, high-frequency circuit boards, and lightweight structural components of spacecraft that have harsh requirements for mechanical strength and dielectric properties, greatly ensuring the safety of electronic products.

[0005] The purpose of the present invention is achieved by the following technical solutions: A high-strength and low-dielectric-loss epoxy resin composite material, the epoxy resin composite material comprises the following raw materials in parts by weight: 100 parts of modified epoxy resin, 12 - 18 parts of cyanate resin, 40 - 50 parts of aramid fiber, 10 - 15 parts of filler, 15 - 25 parts of toughening agent, 1 - 6 parts of first curing agent and 1 - 2 parts of accelerator.

[0006] The present invention prepares an epoxy resin composite material with high strength and good impact resistance by adding cyanate ester resin, aramid fiber, filler, toughening agent and other components to the modified epoxy resin. At the same time, it has a high breakdown strength, low dielectric constant and low dielectric loss. The addition of cyanate ester resin reduces the polarity of the system through co-curing reaction with the modified epoxy resin, and reduces the dipole polarization loss; aramid fiber has excellent mechanical properties and good dielectric properties, which improve the mechanical and dielectric properties of the epoxy resin composite material; the use of filler can reduce the dielectric loss of the epoxy resin composite material; the addition of toughening agent improves the mechanical properties of the epoxy resin composite material, and at the same time, the compatibility between the components is good.

[0007] Further, the cyanate ester resin is selected from bisphenol A type cyanate ester resin.

[0008] Further, the filler is boron nitride flakes, wherein the particle size of the boron nitride flakes is 50 - 100 nm. The layered structure of the boron nitride flakes can inhibit charge migration and reduce dielectric loss.

[0009] Further, the preparation method of the modified epoxy resin comprises the following steps:

[0010] A1. Dissolve magnesium chloride and aluminum chloride in deionized water, and stir until completely dissolved to obtain a pretreatment solution;

[0011] A2. Pre-dissolve sodium silicate in hot water at 40 - 50 °C, and then slowly add it to the pretreatment solution to obtain solution one;

[0012] A3. Mix epoxy resin and ethanol at a mass ratio of 1:1.8 - 2.2, and magnetically stir at a temperature of 55 - 65 °C for 1 - 2 h until completely dissolved to obtain solution two;

[0013] A4. Mix solution one and solution two and stir evenly, then add ammonia water to adjust the pH to 9 - 11 to obtain a mixed solution;

[0014] A5. Transfer the mixed solution to a high-pressure reaction kettle with a polytetrafluoroethylene liner, and react at a temperature of 200 - 300 °C and a reaction pressure of 2 - 10 Mpa for 12 - 48 h. After the reaction is completed, cool it naturally to room temperature, centrifuge to separate the precipitate, and wash and dry to obtain the modified epoxy resin.

[0015] In the present invention, by adding sodium silicate, magnesium chloride and aluminum chloride to the epoxy resin, Mg2Al4Si5O is in-situ generated in the epoxy resin matrix through hydrothermal / solvothermal method 18 to obtain the modified epoxy resin, avoiding the pore structure collapse caused by traditional mechanical mixing, and at the same time realizing the uniform composite of the gel and the resin. At the same time, the addition of Mg2Al4Si5O 18 makes the epoxy resin composite material have good dielectric properties.

[0016] Further, in step A3, the epoxy resin is selected from epoxy resin E-51.

[0017] Further, the molar ratio of magnesium chloride, aluminum chloride and sodium silicate is 1-3:3-5:4-6; the total addition amount of magnesium chloride, aluminum chloride and sodium silicate accounts for 10-15% of the mass of the epoxy resin.

[0018] Further, the toughening agent is polyurethane / epoxy core-shell microspheres. Among them, the preparation method of the polyurethane / epoxy core-shell microspheres includes the following steps:

[0019] B1. Place polyethylene glycol under the protection of a protective gas, dehydrate it at 105-115°C for 1-3 h, cool it to 75-85°C, add hexamethylene diisocyanate and an organotin catalyst, react for 2-3 h, and then add acetone for emulsification to obtain a diluted polyurethane prepolymer.

[0020] B2. Dissolve the emulsifier in deionized water to prepare an aqueous solution with a concentration of 1-3 wt%.

[0021] B3. Slowly add the diluted polyurethane prepolymer into the aqueous solution, while emulsifying at high speed for 10-20 min, then add a chain extender, continue to stir at 55-65°C for 2-3 h, centrifuge to separate the precipitate, wash it clean to obtain polyurethane microspheres.

[0022] B4. Mix epoxy resin and acetone according to a mass ratio of 0.8-1.2:1, add an emulsifier, and ultrasonically disperse for 30-40 min to obtain an epoxy emulsion.

[0023] B5. Disperse the polyurethane microspheres in deionized water to obtain an aqueous solution of polyurethane microspheres with a solid content of 8-12 wt%.

[0024] B6. Slowly add the epoxy emulsion to the aqueous solution of polyurethane microspheres and stir evenly, then add a second curing agent, continue to stir at 60-70°C for 2-3 h, so that the epoxy resin crosslinks and cures on the surface of the polyurethane microspheres, centrifuge to separate the precipitate, wash it clean and dry to obtain polyurethane / epoxy core-shell microspheres.

[0025] The polyurethane / epoxy core-shell microspheres of the present invention are a core-shell structure toughening agent. Its core layer is flexible polyurethane and the shell layer is epoxy resin. It can be evenly dispersed in the epoxy resin matrix, absorb energy through the plastic deformation of the core layer, significantly improve the toughness of the composite material. At the same time, the shell layer has good compatibility with the epoxy resin matrix, ensuring the interfacial bonding strength, so that the epoxy resin composite material has good mechanical properties without affecting the dielectric properties.

[0026] Further, in step B1, the mass ratio of acetone to polyurethane prepolymer is 0.8 - 1.2:1.

[0027] Further, in step B4, the epoxy resin is selected from epoxy resin E - 51.

[0028] Further, the molar ratio of polyethylene glycol to hexamethylene diisocyanate is 1.8 - 2.2:1, and the addition amount of the organotin catalyst is 0.1 - 0.3% of the total mass of the chain extender, polyethylene glycol and hexamethylene diisocyanate. Among them, the polyethylene glycol used is polyethylene glycol 2000.

[0029] Further, in steps B2 and B4, the emulsifier is Tween - 80. Among them, in step B2, the dosage of the emulsifier is 1 - 3% of the polyurethane prepolymer; in step B4, the dosage of the emulsifier is 0.8 - 1.2% of the mass of the epoxy resin.

[0030] Further, the chain extender is BDO, and the dosage of the chain extender is 4 - 6% of the mass of the polyurethane prepolymer.

[0031] Further, in step B6, the addition amount of the second curing agent is 8 - 12% of the mass of the epoxy resin. The second curing agent is selected from DETA.

[0032] Further, the first curing agent is at least one of methylhexahydrophthalic anhydride and MHHPA, to avoid the agglomeration of fillers caused by high temperature.

[0033] Further, the accelerator is 1 - ethyl - 3 - methylimidazolium tetrafluoroborate, which can accelerate curing and improve the dispersibility of fillers.

[0034] The present invention also provides a preparation method of a high - strength and low - dielectric - loss epoxy resin composite material, comprising the following steps:

[0035] S1. Treat the aramid fiber with oxygen plasma for 7 - 8 min, then immerse it in a 0.5 - 0.8 mol / L KH - 550 ethanol solution for 20 - 30 min, dry it to obtain pretreated aramid fiber, weave the pretreated aramid fiber into a fiber preform by three - dimensional braiding technology, and place the fiber preform in a mold;

[0036] S2. Add boron nitride sheets to a 0.5 - 0.8 mol / L KH - 570 ethanol solution and perform ultrasonic treatment for 1 - 3 h to obtain pretreated boron nitride sheets;

[0037] S3. Stir the modified epoxy resin, cyanate resin, pretreated boron nitride flakes, toughening agent, curing agent and accelerator evenly, then inject them into the fiber preform, evacuate to -0.1 to -0.2 MPa for defoaming for 30 - 40 min to obtain a mixture;

[0038] S4. Hot press the mixture. Among them, the pressure is 5 - 8 MPa. First, heat the mold temperature to 70 - 90 °C and keep it for 1 - 2 h, then heat it to 110 - 130 °C and keep it for 1 - 3 h, and then heat it to 140 - 160 °C and keep it for 2 - 4 h. Gradually release the internal stress, and finally anneal at 170 - 190 °C for 1 - 3 h to eliminate the residual stress, obtaining an epoxy resin composite material.

[0039] Further, in step S1, the power of the oxygen plasma treatment is 150 - 250 W.

[0040] The preparation method of the present invention is simple to operate and convenient to control. The epoxy resin composite material prepared by the above method has high strength, good impact resistance, and at the same time has high breakdown strength, low dielectric constant and low dielectric loss. Among them, the aramid fiber is treated by oxygen plasma, and hydroxyl groups are introduced on the surface to enhance the chemical bonding with the resin. The aramid fiber adopts a three-dimensional braided structure to avoid the fiber conductive path, synergistically improving the mechanical and dielectric properties.

[0041] The beneficial effects of the present invention are as follows:

[0042] (1) By adding sodium silicate, magnesium chloride and aluminum chloride to the epoxy resin, Mg2Al4Si5O is in-situ generated in the epoxy resin matrix by hydrothermal / solvothermal method 18 to obtain a modified epoxy resin. At the same time, cyanate resin, aramid fiber, filler, toughening agent and other components are added to the modified epoxy resin. The prepared epoxy resin composite material has high strength, good impact resistance, and at the same time has high breakdown strength, low dielectric constant and low dielectric loss.

[0043] (2) The preparation method of the high-strength and low-dielectric-loss epoxy resin composite material of the present invention is simple to operate, convenient to control, has high production efficiency and low production cost. The prepared epoxy resin composite material has high strength, good impact resistance, and at the same time has high breakdown strength, low dielectric constant and low dielectric loss, and can be applied to fields with demanding mechanical strength and dielectric performance requirements such as insulation components of high-voltage transmission equipment, high-frequency circuit boards, and lightweight structural components of spacecraft. Detailed implementation mode

[0044] For the convenience of understanding by those skilled in the art, the present invention will be further described below with reference to embodiments. The content mentioned in the implementation mode does not limit the present invention.

[0045] Example 1

[0046] This embodiment provides an epoxy resin composite with high strength and low dielectric loss. The epoxy resin composite comprises the following raw materials in parts by weight: 100 parts of modified epoxy resin, 12 parts of cyanate resin, 40 parts of aramid fiber, 10 parts of filler, 15 parts of toughening agent, 2 parts of first curing agent, and 1.5 parts of accelerator.

[0047] Further, the cyanate resin is selected from bisphenol A type cyanate resin.

[0048] Further, the filler is boron nitride flakes, wherein the particle size of the boron nitride flakes is 70 nm.

[0049] Further, the preparation method of the modified epoxy resin comprises the following steps:

[0050] A1. Dissolve magnesium chloride and aluminum chloride in deionized water, and stir until completely dissolved to obtain a pretreatment solution;

[0051] A2. Pre-dissolve sodium silicate in hot water at 45 °C, and then slowly add it to the pretreatment solution to obtain solution one;

[0052] A3. Mix epoxy resin and ethanol at a mass ratio of 1:2, and magnetically stir at a temperature of 60 °C for 1.5 h until completely dissolved to obtain solution two;

[0053] A4. Mix solution one and solution two and stir evenly, and then add ammonia water to adjust the pH to 10 to obtain a mixed solution;

[0054] A5. Transfer the mixed solution to a high-pressure reaction kettle with a polytetrafluoroethylene inner liner, and react at a temperature of 250 °C and a reaction pressure of 6 Mpa for 32 h. After the reaction is completed, naturally cool to room temperature, centrifuge to separate the precipitate, and wash and dry to obtain the modified epoxy resin.

[0055] Further, in step A3, the epoxy resin is selected from epoxy resin E-51.

[0056] Further, the molar ratio of magnesium chloride, aluminum chloride, and sodium silicate is 2:4:5; the total addition amount of magnesium chloride, aluminum chloride, and sodium silicate accounts for 12% of the mass of the epoxy resin.

[0057] Further, the toughening agent is polyurethane / epoxy core-shell microspheres. Among them, the preparation method of the polyurethane / epoxy core-shell microspheres comprises the following steps:

[0058] B1. Place polyethylene glycol under the protection of a protective gas, dehydrate at 110 °C for 1-3 h, cool to 80 °C, add hexamethylene diisocyanate and an organotin catalyst, react for 2.5 h, and then add acetone for emulsification to obtain a diluted polyurethane prepolymer;

[0059] B2. Dissolve the emulsifier in deionized water to prepare an aqueous solution with a concentration of 2 wt%.

[0060] B3. Slowly add the diluted polyurethane prepolymer into the aqueous solution, and simultaneously emulsify it at high speed for 10 - 20 min. Then add the chain extender and continue stirring at 60 °C for 2.5 h. Centrifuge to separate the precipitate, wash it clean to obtain polyurethane microspheres.

[0061] B4. Mix epoxy resin and acetone in a mass ratio of 1:1, add the emulsifier and disperse it by ultrasonic for 35 min to obtain an epoxy emulsion.

[0062] B5. Disperse the polyurethane microspheres in deionized water to obtain an aqueous solution of polyurethane microspheres with a solid content of 10 wt%.

[0063] B6. Slowly add the epoxy emulsion into the aqueous solution of polyurethane microspheres and stir evenly. Then add the second curing agent and continue stirring at 65 °C for 2.5 h to crosslink and cure the epoxy resin on the surface of the polyurethane microspheres. Centrifuge to separate the precipitate, wash it clean and dry to obtain polyurethane / epoxy core-shell microspheres.

[0064] Further, in step B1, the mass ratio of acetone to polyurethane prepolymer is 1:1.

[0065] Further, in step B4, the epoxy resin is selected from epoxy resin E-51.

[0066] Further, the molar ratio of polyethylene glycol to hexamethylene diisocyanate is 2:1, and the addition amount of the organotin catalyst is 0.2% of the total mass of the chain extender, polyethylene glycol and hexamethylene diisocyanate. Among them, the polyethylene glycol is selected as polyethylene glycol 2000.

[0067] Further, in steps B2 and B4, the emulsifier is Tween-80. Among them, in step B2, the addition amount of the emulsifier is 2% of the polyurethane prepolymer; in step B4, the addition amount of the emulsifier is 1% of the mass of the epoxy resin.

[0068] Further, the chain extender is BDO, and the addition amount of the chain extender is 5% of the mass of the polyurethane prepolymer.

[0069] Further, in step B6, the addition amount of the second curing agent is 10% of the mass of the epoxy resin. The second curing agent is selected as DETA.

[0070] Further, the first curing agent is methylhexahydrophthalic anhydride; the accelerator is 1-ethyl-3-methylimidazolium tetrafluoroborate.

[0071] This embodiment also provides a method for preparing an epoxy resin composite material with high strength and low dielectric loss, which includes the following steps:

[0072] S1. Treat the aramid fiber with oxygen plasma for 7 min, then immerse it in a 0.6 mol / L KH-550 ethanol solution for 25 min, and obtain the pretreated aramid fiber after drying. Weave the pretreated aramid fiber into a fiber preform by three-dimensional weaving technology, and place the fiber preform in a mold.

[0073] S2. Add boron nitride sheets to a 0.6 mol / L KH-570 ethanol solution and perform ultrasonic treatment for 2 h to obtain pretreated boron nitride sheets.

[0074] S3. Stir the modified epoxy resin, cyanate resin, pretreated boron nitride sheets, toughening agent, curing agent and accelerator evenly, then inject them into the fiber preform, evacuate to -0.1 MPa to remove bubbles for 35 min to obtain a mixture.

[0075] S4. Thermally press the mixture. Among them, the pressure is 6 MPa. The mold temperature is first raised to 80 °C and maintained for 1.5 h, then raised to 120 °C and maintained for 2 h, then raised to 150 °C and maintained for 3 h, and finally annealed at 180 °C for 2 h to obtain the epoxy resin composite material.

[0076] Further, in step S1, the power of the oxygen plasma treatment is 200 W.

[0077] Example 2

[0078] Different from Example 1, this embodiment provides an epoxy resin composite material with high strength and low dielectric loss. The epoxy resin composite material includes the following raw material components in parts by weight: 100 parts of modified epoxy resin, 16 parts of cyanate resin, 45 parts of aramid fiber, 12 parts of filler, 20 parts of toughening agent, 4 parts of first curing agent and 1.5 parts of accelerator.

[0079] This embodiment also provides a method for preparing an epoxy resin composite material with high strength and low dielectric loss, which includes the following steps:

[0080] S1. Treat the aramid fiber with oxygen plasma for 7 min, then immerse it in a 0.6 mol / L KH-550 ethanol solution for 25 min, and obtain the pretreated aramid fiber after drying. Weave the pretreated aramid fiber into a fiber preform by three-dimensional weaving technology, and place the fiber preform in a mold.

[0081] S2. Add boron nitride sheets to a 0.6 mol / L KH-570 ethanol solution and perform ultrasonic treatment for 2 h to obtain pretreated boron nitride sheets.

[0082] S3. Stir the modified epoxy resin, cyanate resin, pretreated boron nitride flakes, toughening agent, curing agent and accelerator evenly, then inject them into the fiber preform, evacuate to -0.1 MPa and defoam for 35 min to obtain a mixture;

[0083] S4. Hot press the mixture. Among them, the pressure is 6 MPa. The mold temperature is first raised to 80 °C and held for 1.5 h, then raised to 120 °C and held for 2 h, then raised to 150 °C and held for 3 h, and finally annealed at 180 °C for 2 h to obtain an epoxy resin composite material.

[0084] Example 3

[0085] This example provides an epoxy resin composite material with high strength and low dielectric loss. The epoxy resin composite material comprises the following raw materials in parts by weight: 100 parts of modified epoxy resin, 18 parts of cyanate resin, 50 parts of aramid fiber, 15 parts of filler, 25 parts of toughening agent, 6 parts of first curing agent and 1.5 parts of accelerator.

[0086] This example also provides a preparation method of an epoxy resin composite material with high strength and low dielectric loss, comprising the following steps:

[0087] S1. Treat the aramid fiber with oxygen plasma for 7 min, then immerse it in a 0.6 mol / L KH-550 ethanol solution for 25 min, dry it to obtain pretreated aramid fiber, weave the pretreated aramid fiber into a fiber preform by three-dimensional braiding technology, and place the fiber preform in a mold;

[0088] S2. Add boron nitride flakes to a 0.6 mol / L KH-570 ethanol solution and perform ultrasonic treatment for 2 h to obtain pretreated boron nitride flakes;

[0089] S3. Stir the modified epoxy resin, cyanate resin, pretreated boron nitride flakes, toughening agent, curing agent and accelerator evenly, then inject them into the fiber preform, evacuate to -0.1 MPa and defoam for 35 min to obtain a mixture;

[0090] S4. Hot press the mixture. Among them, the pressure is 6 MPa. The mold temperature is first raised to 80 °C and held for 1.5 h, then raised to 120 °C and held for 2 h, then raised to 150 °C and held for 3 h, and finally annealed at 180 °C for 2 h to obtain an epoxy resin composite material.

[0091] Comparative Example 1

[0092] The difference between this comparative example and Example 2 is as follows: This comparative example provides an epoxy resin composite with high strength and low dielectric loss. The epoxy resin composite comprises the following raw materials in parts by weight: 100 parts of epoxy resin, 8 parts of cyanate resin, 45 parts of aramid fiber, 12 parts of filler, 20 parts of toughening agent, 4 parts of first curing agent, and 1.5 parts of accelerator.

[0093] Further, the epoxy resin is selected from epoxy resin E-51.

[0094] This comparative example also provides a preparation method of an epoxy resin composite with high strength and low dielectric loss, comprising the following steps:

[0095] S1. Subject the aramid fiber to oxygen plasma treatment for 7 min, then immerse it in a 0.6 mol / L KH-550 ethanol solution for 25 min, and obtain pretreated aramid fiber after drying. Weave the pretreated aramid fiber into a fiber preform by three-dimensional braiding technology, and place the fiber preform in a mold.

[0096] S2. Add boron nitride sheets to a 0.6 mol / L KH-570 ethanol solution and perform ultrasonic treatment for 2 h to obtain pretreated boron nitride sheets.

[0097] S3. Stir the epoxy resin, cyanate resin, pretreated boron nitride sheets, toughening agent, curing agent, and accelerator evenly, then inject them into the fiber preform, evacuate to -0.1 MPa to remove bubbles for 35 min to obtain a mixture.

[0098] S4. Thermally press the mixture. Among them, the pressure is 6 MPa. First, raise the temperature of the mold to 80 °C and maintain it for 1.5 h, then raise the temperature to 120 °C and maintain it for 2 h, then raise the temperature to 150 °C and maintain it for 3 h, and finally anneal at 180 °C for 2 h to obtain the epoxy resin composite.

[0099] The remaining content of this comparative example is the same as that of Example 2 and will not be elaborated here.

[0100] Comparative Example 2

[0101] The difference between this comparative example and Example 2 is that an equal amount of modified epoxy resin is used to replace the toughening agent. That is, this comparative example provides an epoxy resin composite with high strength and low dielectric loss. The epoxy resin composite comprises the following raw materials in parts by weight: 120 parts of modified epoxy resin, 8 parts of cyanate resin, 45 parts of aramid fiber, 12 parts of filler, 4 parts of first curing agent, and 1.5 parts of accelerator.

[0102] The remaining content of this comparative example is the same as that of Example 2 and will not be elaborated here.

[0103] Comparative Example 3

[0104] The difference between this comparative example and Example 2 is that an equal amount of modified epoxy resin is used to replace the cyanate resin. That is, this comparative example provides an epoxy resin composite material with high strength and low dielectric loss. The epoxy resin composite material comprises the following raw materials in parts by weight: 116 parts of modified epoxy resin, 45 parts of aramid fiber, 12 parts of filler, 20 parts of toughening agent, 4 parts of first curing agent, and 1.5 parts of accelerator.

[0105] The rest of this comparative example is the same as that of Example 2 and will not be repeated here.

[0106] The present invention tests the properties of the high-strength and low-dielectric-loss epoxy resin composite materials prepared in the above Examples 1-3 and Comparative Examples 1-3, including the tensile strength, flexural strength, dielectric constant, dielectric loss, volume resistivity, and breakdown strength of the epoxy resin composite materials. Among them, the tensile strength is tested according to the ASTM D638 test standard; the flexural strength is tested according to the ASTM D790 test standard; the dielectric constant and dielectric loss are tested according to the ASTM D150 test standard; the volume resistivity is tested according to the ASTM D257 test standard and is measured at 25°C; the DC breakdown strength is tested according to the IEC 60243 test standard. The test results are shown in the following table.

[0107]

[0108] It can be seen from the above test data that the epoxy resin composite material of the present invention has high strength and good impact resistance, and at the same time has high breakdown strength, low dielectric constant, and low dielectric loss, and can be applied to fields with strict requirements for mechanical strength and dielectric properties, such as insulating components of high-voltage transmission equipment, high-frequency circuit boards, and lightweight structural components of spacecraft.

[0109] 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 replacement without departing from the concept of the present invention is within the protection scope of the present invention.

Claims

1. A high-strength and low-dielectric-loss epoxy resin composite, characterized in that: It comprises raw material components in the following parts by weight: 100 parts of modified epoxy resin, 12 - 18 parts of cyanate resin, 40 - 50 parts of aramid fiber, 10 - 15 parts of filler, 15 - 25 parts of toughening agent, 1 - 6 parts of first curing agent, and 1 - 2 parts of accelerator.

2. The high-strength and low-dielectric-loss epoxy resin composite material according to claim 1, wherein: The filler is boron nitride flakes, wherein the particle size of the boron nitride flakes is 50 - 100 nm.

3. A high-strength and low-dielectric-loss epoxy resin composite according to claim 1, characterized in that: The preparation method of the modified epoxy resin comprises the following steps: A1. Dissolve magnesium chloride and aluminum chloride in deionized water, and stir until completely dissolved to obtain a pretreatment solution; A2. Pre - dissolve sodium silicate in hot water at 40 - 50 °C, and then slowly add it to the pretreatment solution to obtain solution one; A3. Mix epoxy resin and ethanol at a mass ratio of 1:1.8 - 2.2, and magnetically stir at a temperature of 55 - 65 °C for 1 - 2 h until completely dissolved to obtain solution two; A4. Mix solution one and solution two and stir evenly, then add ammonia water to adjust the pH to 9 - 11 to obtain a mixed solution; A5. Transfer the mixed solution to a high - pressure reactor with a polytetrafluoroethylene liner, and react at a temperature of 200 - 300 °C and a reaction pressure of 2 - 10 Mpa for 12 - 48 h. After the reaction is completed, naturally cool to room temperature, centrifuge to separate the precipitate, and wash and dry to obtain the modified epoxy resin.

4. A high-strength and low-dielectric-loss epoxy resin composite according to claim 3, characterized in that: The molar ratio of magnesium chloride, aluminum chloride, and sodium silicate is 1 - 3:3 - 5:4 - 6; the total addition amount of magnesium chloride, aluminum chloride, and sodium silicate accounts for 10 - 15% of the mass of epoxy resin.

5. A high-strength and low-dielectric-loss epoxy resin composite according to claim 1, characterized in that: The toughening agent is polyurethane / epoxy core - shell microspheres.

6. The high-strength and low-dielectric-loss epoxy resin composite material according to claim 5, characterized in that: The preparation method of the polyurethane / epoxy core - shell microspheres comprises the following steps: B1. Place polyethylene glycol under the protection of a protective gas, dehydrate at 105 - 115 °C for 1 - 3 h, cool to 75 - 85 °C, add hexamethylene diisocyanate and an organotin catalyst, react for 2 - 3 h, and then add acetone for emulsification to obtain a diluted polyurethane prepolymer; B2. Dissolve the emulsifier in deionized water to prepare an aqueous solution with a concentration of 1 - 3 wt%; B3. Slowly add the diluted polyurethane prepolymer to the aqueous solution, simultaneously perform high - speed emulsification for 10 - 20 min, then add a chain extender, and continue to stir at 55 - 65 °C for 2 - 3 h. Centrifuge to separate the precipitate, wash it clean to obtain polyurethane microspheres; B4. Mix epoxy resin and acetone at a mass ratio of 0.8 - 1.2:1, add an emulsifier and ultrasonically disperse for 30 - 40 min to obtain an epoxy emulsion; B5. Disperse the polyurethane microspheres in deionized water to obtain an aqueous solution of polyurethane microspheres with a solid content of 8 - 12 wt%; B6. Slowly add the epoxy emulsion to the aqueous solution of polyurethane microspheres and stir evenly, then add a second curing agent, and continue to stir at 60 - 70 °C for 2 - 3 h. Centrifuge to separate the precipitate, wash it clean and dry to obtain polyurethane / epoxy core - shell microspheres.

7. An epoxy resin composite material with high strength and low dielectric loss according to claim 6, characterized in that: The molar ratio of polyethylene glycol and hexamethylene diisocyanate is 1.8 - 2.2:1, and the addition amount of the organotin catalyst is 0.1 - 0.3% of the total mass of the chain extender, polyethylene glycol, and hexamethylene diisocyanate.

8. A high-strength and low-dielectric-loss epoxy resin composite according to claim 6, characterized in that: In step B6, the addition amount of the second curing agent is 8 - 12% of the mass of epoxy resin.

9. A high-strength and low-dielectric-loss epoxy resin composite according to claim 1, characterized in that: The first curing agent is at least one of methylhexahydrophthalic anhydride and MHHPA; the accelerator is 1-ethyl-3-methylimidazolium tetrafluoroborate.

10. The preparation method of the high-strength and low-dielectric-loss epoxy resin composite material according to any one of claims 1-9, characterized in that: It includes the following steps: S1. Subject the aramid fiber to oxygen plasma treatment for 7-8 min, then immerse it in a 0.5-0.8 mol / L KH-550 ethanol solution for 20-30 min. After drying, obtain the pretreated aramid fiber. Weave the pretreated aramid fiber into a fiber preform by three-dimensional braiding technology, and place the fiber preform in a mold. S2. Add boron nitride flakes to a 0.5-0.8 mol / L KH-570 ethanol solution and perform ultrasonic treatment for 1-3 h to obtain pretreated boron nitride flakes. S3. Stir the modified epoxy resin, cyanate resin, pretreated boron nitride flakes, toughening agent, curing agent and accelerator evenly, then inject them into the fiber preform, evacuate to -0.1 to -0.2 MPa to remove bubbles for 30-40 min to obtain a mixture. S4. Thermally press the mixture. Among them, the pressure is 5-8 MPa. The mold temperature is first raised to 70-90 °C and maintained for 1-2 h, then raised to 110-130 °C and maintained for 1-3 h, then raised to 140-160 °C and maintained for 2-4 h, and finally annealed at 170-190 °C for 1-3 h to obtain the epoxy resin composite material.

Images