Epoxy resin composition with high dielectric constant

Abstract

The invention discloses an epoxy resin composition with a high dielectric constant. The epoxy resin composition comprises the following components in parts by weight: 100 parts of an epoxy resin matrix, 15-30 parts of modified nano barium titanate, 5-10 parts of a polar solubilizer, 80-90 parts of a curing agent and 0.5-1 part of an accelerant, through component compounding and nano barium titanate modification, the problem of dielectric property degradation caused by interface defects and polarization mismatch of the nano barium titanate filled epoxy resin composite material is solved.

Description

Technical Field

[0001] This invention relates to the field of dielectric materials technology, and more particularly to a high dielectric constant epoxy resin composition. Background Technology

[0002] As electronic devices become increasingly higher frequency and miniaturized, the demand for high dielectric constant polymer-based composite materials in fields such as embedded capacitors and high-voltage insulation is growing. Epoxy resin is the preferred matrix material due to its excellent mechanical properties and heat resistance, but its intrinsic dielectric constant is relatively low, making it difficult to meet the requirements of high energy storage.

[0003] Traditional methods utilize ferroelectric ceramics such as barium titanate (BaTiO3) to improve dielectric constant, but this approach faces numerous challenges in practical applications. The high specific surface area of ​​nano-barium titanate easily leads to agglomeration, forming interfacial defects, increasing leakage current, and reducing breakdown strength. Simultaneously, the non-polar properties of epoxy resins are mismatched with the strong polarity of barium titanate, weakening the interfacial polarization effect and limiting the improvement in dielectric constant. Furthermore, high filler content exacerbates system viscosity, affecting processing flowability, and inducing microcracks due to thermal stress during curing, compromising the long-term stability of the material. While existing technologies attempt to improve dispersibility through coupling agent modification or compatibilizers, they have failed to effectively address the issues of polarization matching and process compatibility, making it difficult to synergistically optimize dielectric properties.

[0004] Therefore, a solution is needed to address the problem of dielectric property degradation in nano-barium titanate-filled epoxy resin composites caused by interfacial defects and polarization mismatch. Summary of the Invention

[0005] In view of this, this application provides a high dielectric constant epoxy resin composition to solve the problem of dielectric property degradation caused by interfacial defects and polarization mismatch in nano-barium titanate filled epoxy resin composites.

[0006] To achieve the above technical objectives, this application adopts the following technical solution:

[0007] This application provides a high dielectric constant epoxy resin composition comprising, by weight: 100 parts epoxy resin matrix, 15-30 parts modified nano barium titanate, 5-10 parts polar solubilizer, 80-90 parts curing agent, and 0.5-1 parts accelerator.

[0008] Preferably, the modified nano-barium titanate is prepared as follows: nano-barium titanate is dispersed in a solvent, a titanate coupling agent is added, and pretreated at 60-80°C for 1-2 hours to obtain an intermediate; an epoxy-containing silane coupling agent is added to the intermediate, and reacted at 80-100°C for 2-3 hours to obtain surface-grafted core-shell structured particles, which are the modified nano-barium titanate.

[0009] Preferably, the titanate coupling agent is isopropyltris(dioctylpyrophosphate) titanate; the epoxy-containing silane coupling agent is γ-glycidoxypropyltrimethoxysilane.

[0010] Preferably, the polar compatibilizer is one or more of cyanate ester resin and polyetherimide.

[0011] Preferably, the epoxy resin matrix is ​​a bisphenol A type epoxy resin with an epoxy equivalent of 180-200 g / eq.

[0012] Preferably, the weight ratio of the modified nano barium titanate to the polar compatibilizer is (3-5):1.

[0013] Preferably, the curing agent is one or more of methylhexahydrophthalic anhydride and methyltetrahydrophthalic anhydride.

[0014] Preferably, the accelerator is one or more of 2-ethyl-4-methylimidazole and 1-benzyl-2-methylimidazole.

[0015] Preferably, the amount of the titanate coupling agent is 1.5-3.0% of the weight of the nano barium titanate.

[0016] Preferably, it also includes 0.1-0.5 parts of DOPO derivative flame retardant.

[0017] The beneficial effects of this application are as follows:

[0018] This application significantly improves the dielectric properties of epoxy resin composites through optimized component design and interface control. A two-step modification process is used to surface-modify nano-barium titanate, constructing a stable core-shell structure that effectively suppresses filler agglomeration and improves its dispersibility in the resin matrix. This reduces interfacial defects and leakage current, thereby enhancing the material's insulation performance. The introduction of a polar compatibilizer further enhances the interfacial polarization effect; its strongly polar groups form a stable interaction with the barium titanate surface, significantly increasing the dielectric constant of the composite material while maintaining low dielectric loss.

[0019] In terms of process adaptability, by optimizing the composition of the curing system, the composite material maintains good fluidity during curing, reducing processing difficulty. Simultaneously, it effectively suppresses the accumulation of curing stress, avoids the generation of microcracks, and improves the material's mechanical stability and long-term reliability. The ratio of modified nano-barium titanate to the compatibilizer is rationally controlled to ensure sufficient coating of the filler surface, maintaining stable dielectric properties over a wide temperature range while possessing high breakdown strength. Furthermore, the addition of flame retardants not only endows the material with excellent flame retardant properties, but their polar structure also synergistically enhances the interfacial polarization effect, further improving dielectric properties without affecting dielectric loss, thus achieving a multifunctional integrated design. Detailed Implementation

[0020] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0021] This application provides a high dielectric constant epoxy resin composition comprising, by weight: 100 parts epoxy resin matrix, 15-30 parts modified nano barium titanate, 5-10 parts polar solubilizer, 80-90 parts curing agent, and 0.5-1 parts accelerator.

[0022] In this scheme, barium titanate nanoparticles were added to improve the dielectric constant of the epoxy resin matrix. However, the reason why filling the epoxy resin matrix with barium titanate nanoparticles to improve the dielectric constant is not effective is as follows: the high specific surface area of ​​nanoparticles leads to agglomeration and poor dispersion, forming interface defects, causing leakage current and reducing breakdown strength; the non-polar properties of the resin do not match the strong polarity of BaTiO3, weakening the interface polarization effect, resulting in low polarization efficiency and limiting the improvement of the dielectric constant; the high filler content increases the viscosity of the system, hinders processing fluidity, has poor process compatibility, and at the same time, the thermal stress during the curing process induces microcracks, which damages the stability of the dielectric material.

[0023] Therefore, the dielectric constant of the composition needs to be improved by enhancing the dispersibility of the components, increasing the polarization effect, and improving the adaptability of the process.

[0024] In this application, the perovskite crystal structure of modified nano-barium titanate spontaneously polarizes under an electric field, exhibiting a high dielectric constant. As a polarization source, it acts as a surface modification layer, eliminating energy barriers, resulting in a uniform electric field distribution and improved dispersion. However, when its dosage is below 15 parts, the percolation threshold is not reached, the polarization network is discontinuous, and the improvement in dielectric constant is limited. Above 30 parts, the viscosity increases dramatically, and the probability of interface defects rises exponentially, leading to a decrease in breakdown strength. The polar compatibilizer contains strongly polar groups (such as -C≡N of cyanate esters and the imide ring of polyether imides), whose electronegative atoms (N, O) react with the Ti of BaTiO3. 4+ The formation of ion-dipole interactions induces the displacement polarization and directional alignment of titanium ions, overcoming the polarization mismatch problem. However, when its dosage is less than 5 parts, it cannot completely cover the filler surface, resulting in insufficient interfacial polarization efficiency. When it is more than 10 parts, the excess compatibilizer self-aggregates to form an insulating barrier, hindering the transmission of polarization field. Meanwhile, the epoxy resin matrix is ​​used to construct a continuous phase network, maintain polarization stability at high frequencies, and, in conjunction with the low viscosity characteristics of the curing agent and the catalytic activity of the accelerator, maintain the fluidity of the system and suppress internal stress during the crosslinking process, thus improving the adaptability of the process.

[0025] In some embodiments, the modified barium titanate nanoparticles are prepared as follows: barium titanate nanoparticles are dispersed in a solvent, a titanate coupling agent is added, and the mixture is pretreated at 60-80°C for 1-2 hours to obtain an intermediate; an epoxy-containing silane coupling agent is added to the intermediate, and the mixture is reacted at 80-100°C for 2-3 hours to obtain surface-grafted core-shell structured particles, which are the modified barium titanate nanoparticles.

[0026] In this embodiment, the titanate coupling agent first anchors the BaTiO3 surface to form a hydrophobic isolation layer; then, the silanol groups of the epoxy-containing silane coupling agent are entangled with the hydrophobic chain, and the epoxy groups provide reaction sites to the outside, forming an "inorganic core-organic transition layer-reactive shell" structure, which reduces the interfacial energy difference between the filler and the resin, thereby eliminating the agglomeration source; while the hydroxyl groups (-OH) on the surface of unmodified BaTiO3 easily adsorb water molecules to form conductive channels, and the interfacial energy mismatch with the epoxy resin leads to agglomeration.

[0027] In some embodiments, the titanate coupling agent is isopropyltris(dioctylpyrophosphate) titanate; the epoxy-containing silane coupling agent is γ-glycidoxypropyltrimethoxysilane.

[0028] In this embodiment, by limiting the combination of titanate coupling agent and epoxy-containing silane coupling agent, the bonding of phosphate ester and silanol is complementary, thereby maximizing shell density and improving leakage current suppression rate.

[0029] In some embodiments, the polar compatibilizer is one or more of cyanate ester resin and polyetherimide.

[0030] In this embodiment, the -C≡N group of the cyanate ester resin (CE) acts as a strong electron acceptor, forming a coordination bond with Ti⁴⁺ to enhance ion displacement polarization intensity; the imide ring conjugated structure of polyetherimide (PEI) captures free charges through π-electron delocalization, reducing leakage conduction loss. Although their mechanisms of action differ (CE enhances polarization / PEI suppresses loss), both improve interfacial polarization efficiency by forming a dielectric bridging network through molecular chains entangled with nanoparticles.

[0031] In some embodiments, the epoxy resin matrix is ​​a bisphenol A type epoxy resin with an epoxy equivalent of 180-200 g / eq.

[0032] In this embodiment, the bisphenol A type resin with an epoxy equivalent of 180-200 g / eq has a molecular chain length that balances crosslinking density and chain segment mobility.

[0033] In some embodiments, the weight ratio of the modified nano-barium titanate to the polar compatibilizer is (3-5):1.

[0034] In this embodiment, exceeding the defined range may result in incomplete coating or self-aggregation of the compatibilizer, leading to a decrease in interfacial polarization efficiency.

[0035] In some embodiments, the curing agent is one or more of methylhexahydrophthalic anhydride and methyltetrahydrophthalic anhydride.

[0036] In some embodiments, the promoter is one or more of 2-ethyl-4-methylimidazole and 1-benzyl-2-methylimidazole.

[0037] In some embodiments, the amount of the titanate coupling agent is 1.5-3.0% of the weight of the nano barium titanate.

[0038] In some embodiments, 0.1-0.5 parts of DOPO derivative flame retardant are also included.

[0039] In this embodiment, the DOPO derivative exhibits gas-solid synergistic flame retardancy during combustion, and its P=O bond dipoles can further assist in interface polarization, thereby increasing the dielectric constant without affecting losses.

[0040] The following specific embodiments further illustrate this solution.

[0041] Raw material source:

[0042] Epoxy resin, bisphenol A type (Nanya NPEL-128, epoxy equivalent 188g / eq);

[0043] Barium titanate nanoparticles, with an average particle size of 100 nm (Guangdong Pioneer Materials);

[0044] Titanate coupling agent, isopropyl tris(dioctylpyrophosphoryloxy)titanate NDZ-201 (Nanjing Nengde New Materials);

[0045] Silane coupling agent, γ-glycidyl etheroxypropyltrimethoxysilane, KH-560 (Wuhan University Organosilicon);

[0046] Polar compatibilizer, cyanate ester prepolymer PT-30 (Lonza);

[0047] Curing agent: Methylhexahydrophthalic anhydride (Jiaxing Alfa);

[0048] Accelerator, 2-ethyl-4-methylimidazole (Shanghai Dibai);

[0049] Flame retardant, DOPO derivative HCA-HQ (Jiangsu Kangtai).

[0050] Preparation method of modified nano-barium titanate: 100g of nano-BaTiO3 was dispersed in 500mL of anhydrous ethanol and sonicated for 30min. Then, 2.5g of isopropyltris(dioctylpyrophosphoryloxy)titanate was added and stirred at 80℃ for 2h. Then, 15g of γ-glycidyl etheroxypropyltrimethoxysilane was added and reacted at 90℃ for 3h. After centrifugation and washing, the mixture was vacuum dried at 80℃ for 12h, ground and sieved to obtain modified nano-barium titanate. The grafting rate of KH-560 was determined to be 90% by TGA weight loss method.

[0051] Example 1

[0052] A high dielectric constant epoxy resin composition comprises, by weight: 100 parts epoxy resin matrix, 20 parts modified nano barium titanate, 8 parts polar solubilizer cyanate ester resin, 85 parts curing agent methylhexahydrophthalic anhydride, 0.8 parts accelerator 2-ethyl-4-methylimidazole, and 0.3 parts DOPO derivative flame retardant; the above raw materials are mixed with a dispersant, then degassed under vacuum at 0.1 MPa for 30 min, poured into a mold, and cured to obtain the high dielectric constant epoxy resin composition.

[0053] Example 2

[0054] A high dielectric constant epoxy resin composition comprises, by weight: 100 parts epoxy resin matrix, 20 parts modified nano barium titanate, 5 parts polar solubilizer cyanate ester resin, 85 parts curing agent methylhexahydrophthalic anhydride, 0.8 parts accelerator 2-ethyl-4-methylimidazole, and 0.3 parts DOPO derivative flame retardant; the above raw materials are mixed with a dispersant, then degassed under vacuum at 0.1 MPa for 30 min, poured into a mold, and cured to obtain the high dielectric constant epoxy resin composition.

[0055] Example 3

[0056] A high dielectric constant epoxy resin composition comprises, by weight: 100 parts epoxy resin matrix, 20 parts modified nano barium titanate, 10 parts polar solubilizer cyanate ester resin, 85 parts curing agent methylhexahydrophthalic anhydride, 0.8 parts accelerator 2-ethyl-4-methylimidazole, and 0.3 parts DOPO derivative flame retardant; the above raw materials are mixed with a dispersant, then degassed under vacuum at 0.1 MPa for 30 min, poured into a mold, and cured to obtain the high dielectric constant epoxy resin composition.

[0057] Example 4

[0058] A high dielectric constant epoxy resin composition comprises, by weight: 100 parts epoxy resin matrix, 15 parts modified nano barium titanate, 8 parts polar solubilizer cyanate ester resin, 85 parts curing agent methylhexahydrophthalic anhydride, 0.8 parts accelerator 2-ethyl-4-methylimidazole, and 0.3 parts DOPO derivative flame retardant; the above raw materials are mixed with a dispersant, then degassed under vacuum at 0.1 MPa for 30 min, poured into a mold, and cured to obtain the high dielectric constant epoxy resin composition.

[0059] Example 5

[0060] A high dielectric constant epoxy resin composition comprises, by weight: 100 parts epoxy resin matrix, 30 parts modified nano barium titanate, 8 parts polar solubilizer cyanate ester resin, 85 parts curing agent methylhexahydrophthalic anhydride, 0.8 parts accelerator 2-ethyl-4-methylimidazole, and 0.3 parts DOPO derivative flame retardant; the above raw materials are mixed with a dispersant, then degassed under vacuum at 0.1 MPa for 30 min, poured into a mold, and cured to obtain the high dielectric constant epoxy resin composition.

[0061] Comparative Example 1

[0062] A high dielectric constant epoxy resin composition comprises, by weight: 100 parts epoxy resin matrix, 20 parts modified nano barium titanate, 3 parts polar solubilizer cyanate ester resin, 85 parts curing agent methylhexahydrophthalic anhydride, 0.8 parts accelerator 2-ethyl-4-methylimidazole, and 0.3 parts DOPO derivative flame retardant; the above raw materials are mixed with a dispersant, then degassed under vacuum at 0.1 MPa for 30 min, poured into a mold, and cured to obtain the high dielectric constant epoxy resin composition.

[0063] Comparative Example 2

[0064] A high dielectric constant epoxy resin composition comprises, by weight: 100 parts epoxy resin matrix, 20 parts modified nano barium titanate, 12 parts polar solubilizer cyanate ester resin, 85 parts curing agent methylhexahydrophthalic anhydride, 0.8 parts accelerator 2-ethyl-4-methylimidazole, and 0.3 parts DOPO derivative flame retardant; the above raw materials are mixed with a dispersant, then degassed under vacuum at 0.1 MPa for 30 min, poured into a mold, and cured to obtain the high dielectric constant epoxy resin composition.

[0065] Comparative Example 3

[0066] A high dielectric constant epoxy resin composition comprises, by weight: 100 parts epoxy resin matrix, 10 parts modified nano barium titanate, 12 parts polar solubilizer cyanate ester resin, 85 parts curing agent methylhexahydrophthalic anhydride, 0.8 parts accelerator 2-ethyl-4-methylimidazole, and 0.3 parts DOPO derivative flame retardant; the above raw materials are mixed with a dispersant, then degassed under vacuum at 0.1 MPa for 30 min, poured into a mold, and cured to obtain the high dielectric constant epoxy resin composition.

[0067] Comparative Example 4

[0068] A high dielectric constant epoxy resin composition comprises, by weight: 100 parts epoxy resin matrix, 40 parts modified nano barium titanate, 12 parts polar solubilizer cyanate ester resin, 85 parts curing agent methylhexahydrophthalic anhydride, 0.8 parts accelerator 2-ethyl-4-methylimidazole, and 0.3 parts DOPO derivative flame retardant; the above raw materials are mixed with a dispersant, then degassed under vacuum at 0.1 MPa for 30 min, poured into a mold, and cured to obtain the high dielectric constant epoxy resin composition.

[0069] Comparative Example 5

[0070] A high dielectric constant epoxy resin composition comprises, by weight: 100 parts epoxy resin matrix, 20 parts unmodified nano barium titanate, 8 parts polar solubilizer cyanate ester resin, 85 parts curing agent methylhexahydrophthalic anhydride, 0.8 parts accelerator 2-ethyl-4-methylimidazole, and 0.3 parts DOPO derivative flame retardant; the above raw materials are mixed with a dispersant, then degassed under vacuum at 0.1 MPa for 30 min, poured into a mold, and cured to obtain the high dielectric constant epoxy resin composition.

[0071] Comparative Example 6

[0072] A high dielectric constant epoxy resin composition comprises, by weight: 100 parts epoxy resin matrix, 20 parts modified nano barium titanate, 8 parts polar solubilizer cyanate ester resin, 85.8 parts curing agent methylhexahydrophthalic anhydride, 0.8 parts accelerator 2-ethyl-4-methylimidazole, and 0.3 parts DOPO derivative flame retardant; the above raw materials are mixed with a dispersant, then degassed under vacuum at 0.1 MPa for 30 min, poured into a mold, and cured to obtain the high dielectric constant epoxy resin composition.

[0073] Comparative Example 7

[0074] A high dielectric constant epoxy resin composition comprises, by weight: 100 parts epoxy resin matrix, 20 parts modified nano barium titanate, 8 parts polar solubilizer cyanate ester resin, 85.8 parts accelerator 2-ethyl-4-methylimidazole, and 0.3 parts DOPO derivative flame retardant; the above raw materials are mixed with a dispersant, then degassed under vacuum at 0.1 MPa for 30 min, poured into a mold, and cured to obtain the high dielectric constant epoxy resin composition.

[0075] Testing and Evaluation

[0076] Dielectric constant (ε) and loss factor (tanδ): According to ASTM D150, an Agilent 4294A impedance analyzer (electrode diameter 25mm) was used at a test frequency of 1kHz and a temperature of 25℃.

[0077] Breakdown strength: According to IEC 60243, the Huace HJC-50kV withstand voltage tester was used, with a DC voltage boost rate of 1kV / s, and the average value of 5 tests was taken.

[0078] Flame retardant properties (oxygen index LOI): According to ASTM D2863, an FTT oxygen index tester was used (sample size 100mm × 10mm × 3mm).

[0079] The test results are shown in Table 1.

[0080] Table 1 Test Results

[0081]

[0082] As can be seen from Examples 1-3 and Comparative Example 5, the core-shell structure of the modified filler eliminates the interfacial energy barrier, allowing the spontaneous polarization field of BaTiO3 to be uniformly transmitted to the resin matrix. In contrast, the unmodified filler forms a "dead zone" due to agglomeration, resulting in a significant decrease in the dielectric constant of Comparative Example 5. As can be seen from Examples 3 and Comparative Example 1, the compatibilizer can directionally induce dipole alignment and improve polarization efficiency. In Comparative Example 1, due to insufficient compatibilizer, only partially coating the filler surface resulted in a discontinuous polarization network and a decrease in dielectric constant.

[0083] As can be seen from Example 1 and Comparative Example 5, modified BaTiO3 is beneficial to reducing dielectric loss. As can be seen from Example 1 and Comparative Example 2, too much or too little solubilizer is detrimental to dielectric loss.

[0084] As can be seen from Example 1 and Comparative Example 3, too little or too little modified BaTiO3 will reduce the breakdown strength.

[0085] The above are merely preferred embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention.

Claims

1. A high dielectric constant epoxy resin composition, characterized in that, By weight, it includes: 100 parts epoxy resin matrix, 15-30 parts modified nano barium titanate, 5-10 parts polar solubilizer, 80-90 parts curing agent, and 0.5-1 parts accelerator.

2. The high dielectric constant epoxy resin composition according to claim 1, characterized in that, The modified nano barium titanate is prepared as follows: The nano-barium titanate was dispersed in a solvent, a titanate coupling agent was added, and the mixture was pretreated at 60-80℃ for 1-2 hours to obtain an intermediate. An epoxy-containing silane coupling agent is added to the intermediate, and the mixture is reacted at 80-100°C for 2-3 hours to obtain surface-grafted core-shell structured particles, which are the modified nano-barium titanate.

3. The high dielectric constant epoxy resin composition according to claim 1, characterized in that, The titanate coupling agent is isopropyltris(dioctylpyrophosphate) titanate; the epoxy-containing silane coupling agent is γ-glycidoxypropyltrimethoxysilane.

4. The high dielectric constant epoxy resin composition according to claim 1, characterized in that, The polar compatibilizer is one or more of cyanate ester resin and polyetherimide.

5. The high dielectric constant epoxy resin composition according to claim 1, characterized in that, The epoxy resin matrix is ​​bisphenol A type epoxy resin with an epoxy equivalent of 180-200 g / eq.

6. The high dielectric constant epoxy resin composition according to claim 1, characterized in that, The weight ratio of the modified nano-barium titanate to the polar compatibilizer is (3-5):

1.

7. The high dielectric constant epoxy resin composition according to claim 1, characterized in that, The curing agent is one or more of methylhexahydrophthalic anhydride and methyltetrahydrophthalic anhydride.

8. The high dielectric constant epoxy resin composition according to claim 1, characterized in that, The accelerator is one or more of 2-ethyl-4-methylimidazole and 1-benzyl-2-methylimidazole.

9. The high dielectric constant epoxy resin composition according to claim 1, characterized in that, The amount of the titanate coupling agent used is 1.5-3.0% of the weight of the nano barium titanate.

10. The high dielectric constant epoxy resin composition according to claim 1, characterized in that, It also includes 0.1-0.5 parts of DOPO derivative flame retardant.

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