A high-strength temperature-stable composite dielectric material, its preparation method and application

Abstract

The present invention provides a high-strength temperature-stable composite dielectric material, a preparation method thereof and an application. The preparation method of the composite dielectric material is as follows: a preform woven from fibers is compounded and formed with a ceramic-modified resin mixed solution to obtain the high-strength temperature-stable composite dielectric material; wherein, the structure of the preform is a flat stacked fabric structure, a three-dimensional orthogonal structure or a three-dimensional angle interlock structure. By compounding and forming fibers, ceramics and polymers, and combining the excellent mechanical properties of fiber-reinforced composite materials with the excellent dielectric properties of ceramic materials, the present invention realizes the regulation of the temperature coefficient of the resonance frequency of the composite material, thereby obtaining a high-strength temperature-stable composite dielectric material, which not only has a low dielectric constant, but also has excellent mechanical properties and stable dielectric properties. It can be used as a substrate material for microwave devices such as resonators, antennas, and filters, and is widely used in the military, national defense, transportation, and power electronics industries.

Description

Technical Field

[0001] The present invention relates to the technical field of microwave dielectric materials, and in particular to a high-strength, temperature-stable composite dielectric material and a preparation method and application thereof. Background Art

[0002] With the rapid development of communication technology, microwave dielectric materials are increasingly used in fields such as filters, resonators and microwave substrates, which puts higher requirements on the performance of microwave dielectric materials. Especially in the field of high-frequency and high-speed communications, microwave dielectric materials need to have both low dielectric constant ( ) to increase the signal transmission rate, and the resonant frequency temperature coefficient close to zero ( ) to ensure the stability of the device frequency. However, while achieving a low dielectric constant and a near-zero resonant frequency temperature coefficient, it is also necessary to take into account the mechanical strength and processing performance of the material, which poses a great challenge to material design and preparation technology.

[0003] At present, traditional microwave dielectric materials mainly use ceramic materials, which are widely used in the preparation of resonators and substrates due to their excellent dielectric properties and high-temperature stability. However, ceramic materials often have a high dielectric constant, which is not conducive to high-speed signal transmission. In addition, their high brittleness, low dielectric breakdown strength, and harsh processing conditions limit their extensive application and adaptability. Low dielectric constant polymer-based composites have broad application prospects in wireless communication systems. By combining microwave dielectric ceramics with low dielectric constant polymers, the dielectric properties of the composites can be regulated to a certain extent. So far, a significant increase in the resonant frequency temperature coefficient of polymer composites can only be obtained under high ceramic loads, which results in high dielectric constants and low mechanical properties of polymer composites. To achieve high-strength, low dielectric constant and low-loss polymer composites, solving the problem of poor mechanical properties and dielectric properties has always been a long-term challenge. Therefore, a new process is needed to prepare high-performance composite dielectric materials with high strength, low dielectric constant, and resonant frequency temperature coefficient close to zero. Summary of the invention

[0004] In view of the deficiencies in the prior art, the present invention provides a high-strength, temperature-stable composite dielectric material and a preparation method and application thereof. A preform having a flat stacked fabric structure, a three-dimensional orthogonal structure or a three-dimensional angular interlocking structure is composited with a ceramic-filled modified polymer resin solution. Ceramic particles are used to regulate the dielectric properties of the composite material to ensure a low dielectric constant and a resonant frequency temperature coefficient. The high-performance fiber and resin composite ensure the mechanical properties of the material, thereby solving the problems raised in the above-mentioned background technology.

[0005] To achieve the above objectives, the present invention is implemented through the following technical solutions:

[0006] According to the first aspect of the present invention, a method for preparing a high-strength temperature-stable composite dielectric material is provided. A preform woven from fibers is compounded with a ceramic-modified resin mixed solution to obtain the high-strength temperature-stable composite dielectric material. Among them, the structure of the preform is a flat stacked fabric structure, a three-dimensional orthogonal structure or a three-dimensional angle interlock structure.

[0007] In this application, fibers, ceramics, and polymers are compounded and molded. At the same time, the excellent mechanical properties of fiber-reinforced composites are combined with the excellent dielectric properties of ceramic materials to obtain a high-strength temperature-stable composite dielectric material. Fabrics with a flat stacked structure, a three-dimensional orthogonal structure or a three-dimensional angle interlock structure act as reinforcements in the composite material, greatly enhancing the mechanical properties of the material along the fiber direction. The polymer resin wraps and fixes the fibers, enabling the load between different fibers to be transmitted through the resin, optimizing the load transmission path, and further enhancing the overall strength of the material. Moreover, this combination effectively prevents the agglomeration of ceramic particles, ensuring the uniformity and stability of the dielectric properties of the composite dielectric material. Ceramic particles have a large temperature coefficient of resonant frequency. Incorporating ceramic particles into the resin matrix of fiber-reinforced composites endows the composites with the intrinsic dielectric response of ceramics, thereby regulating the stability of the dielectric properties of the composites, and finally preparing a high-strength temperature-stable composite dielectric material.

[0008] Preferably, the ceramic material is selected from at least one of strontium titanate, barium titanate, and calcium titanate.

[0009] Preferably, the polymer resin is selected from thermosetting resins or thermoplastic resins.

[0010] Preferably, the polymer resin is selected from at least one of epoxy resin, polyimide resin, phenolic resin, polytetrafluoroethylene resin, vinyl resin, and polypropylene resin.

[0011] Preferably, in the mixed solution containing the ceramic material and the resin, the ceramic material accounts for 20-30 wt% of the mixed solution.

[0012] Preferably, the fibers of the preform are selected from at least one of glass fiber, aramid fiber, polyethylene fiber, basalt fiber, polyphenylene sulfide fiber, and polytetrafluoroethylene fiber.

[0013] Preferably, the process of the composite molding is selected from any one of hand lay-up molding, spray molding, resin transfer molding, vacuum-assisted resin transfer molding, hot pressing molding, and autoclave molding.

[0014] According to the second aspect of the present invention, there is provided a high-strength temperature-stable composite dielectric material obtained by the above preparation method. The temperature coefficient of resonant frequency of the composite dielectric material is -30 ppm / °C to +30 ppm / °C.

[0015] The tensile strength of the composite dielectric material is 400 to 1100 MPa.

[0016] Preferably, the dielectric constant of the composite dielectric material is 3.85 to 4.5, and the dielectric loss is ≤0.02.

[0017] According to the third aspect of the present invention, there is provided an application of a high-strength temperature-stable composite dielectric material in filters, resonators, and microwave dielectric substrates.

[0018] The present invention provides a high-strength temperature-stable composite dielectric material, its preparation method, and application. It has the following beneficial effects:

[0019] (1) In the preparation method of a high-strength temperature-stable composite dielectric material provided by this solution, the combination of the preform fiber and the ceramic-resin mixed solution optimizes the mechanical properties and dielectric properties of the material by using a flat stacked fabric structure, a three-dimensional woven orthogonal structure, or a three-dimensional angle interlock structure. It not only significantly improves the strength and impact resistance of the composite material, but also reduces the dielectric constant, realizes the stability of the temperature coefficient of resonant frequency close to zero, and at the same time improves the thermal stability and processing performance of the material.

[0020] (2) The high-strength temperature-stable composite dielectric material provided by this solution can simultaneously meet the requirements of high strength, low dielectric constant, low dielectric loss, and a temperature coefficient of resonant frequency close to zero, and can improve the performance of filters, resonators, and microwave dielectric substrates. Specific Embodiments

[0021] Next, the technical solutions of the present invention will be clearly and completely described in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0022] The present invention provides a preparation method of a high-strength temperature-stable composite dielectric material. Through high-speed mechanical stirring treatment, ceramic materials are uniformly mixed into polymer resins to obtain a mixed solution. A preform woven from fibers is compounded with the mixed solution containing ceramic materials and resins to obtain the high-strength temperature-stable composite dielectric material; wherein, the structure of the preform is a flat stacked fabric structure, a three-dimensional orthogonal structure, or a three-dimensional angle interlock structure.

[0023] In a specific embodiment, the ceramic material is selected from at least one of strontium titanate, barium titanate, and calcium titanate. Further preferably, the ceramic material is selected from strontium titanate. The strontium titanate ceramic material selected in this application has a low dielectric constant and a temperature coefficient of resonant frequency close to zero, and can have good dispersibility and bonding with the polymer resin and the fibers of the preform. It can be evenly distributed in the matrix, ensuring the structural stability and performance consistency of the composite material. Furthermore, the prepared composite dielectric material combines the characteristics of the preform and the ceramic material, and while enhancing the strength, it also has toughness and impact resistance.

[0024] In a specific embodiment, the particle size of the ceramic material is 1 - 5 μm. Optionally, the particle size of the ceramic material is selected from any value or the range value between any two values among 1 μm, 2 μm, 3 μm, 4 μm, and 5 μm. By limiting the particle size of the ceramic material, the ceramic material can be in full contact with the resin matrix and the reinforcing fibers, enhancing the interfacial bonding force and the mechanical properties and stability of the composite material. In addition, the particle size within this range helps to control the packing density and distribution mode between the ceramic materials, thereby reducing the dielectric constant of the composite dielectric material.

[0025] In a specific embodiment, the polymer resin is selected from thermosetting resins or thermoplastic resins. Specifically, the polymer resin is selected from at least one of epoxy resin, polyimide resin, phenolic resin, polytetrafluoroethylene resin, vinyl resin, and polypropylene resin. The polymer resin selected in this application has a low dielectric constant and dielectric loss, and has good insulation in high-frequency and high-speed signal transmission environments, which helps to reduce the overall dielectric constant of the composite dielectric material.

[0026] In a specific embodiment, in the mixed solution containing the ceramic material and the resin, the ceramic material accounts for 20 - 30 wt% of the mixed solution. Optionally, the ceramic material accounts for any value or the range value between any two values among 20 wt%, 25 wt%, and 30 wt% of the mixed solution. Within the range of 20 - 30 wt%, good interfacial bonding can be formed among the ceramic material, the resin matrix, and the fibers of the prepolymer. Too much or too little ceramic material will cause interfacial bonding failure. Moreover, when the addition amount of the ceramic material is within this range, it can also balance the relationship between the dielectric constant and the mechanical properties, avoiding problems such as too high dielectric constant and poor clamping functionality caused by too much ceramic material.

[0027] In a specific embodiment, the fibers of the prepolymer are selected from at least one of glass fiber, aramid fiber, polyethylene fiber, basalt fiber, polyphenylene sulfide fiber, and polytetrafluoroethylene fiber.

[0028] In a specific embodiment, the process of the composite molding is selected from any one of hand lay-up molding, spray molding, resin transfer molding, vacuum assisted resin transfer molding, hot pressing molding, and autoclave molding.

[0029] Hereinafter, a high-strength temperature-stable composite dielectric material and its preparation method and application according to the present application will be further described with reference to specific embodiments.

[0030] Example 1

[0031] (1) Lay up 6 layers of glass fiber woven grid cloth with a grammage of 400 g to obtain a glass fiber lay-up structure preform with a thickness of 2 mm;

[0032] (2) Mix strontium titanate ceramics with a particle size of 1 μm with epoxy resin and a curing agent, and fully stir them through a high-speed mixer to obtain a mixed solution in which strontium titanate ceramics account for 30 wt% of the total content;

[0033] (3) Fill the mixed solution into the glass fiber lay-up structure preform through the VARTM molding process, control the vacuum degree to be -0.1 MPa, pre-cure at 50 °C for 3 h, and cure at 70 °C for 7 h to obtain a lay-up structure ceramic-filled glass fiber / epoxy resin temperature-stable microwave composite dielectric material.

[0034] Example 2

[0035] (1) Prepare a three-dimensional orthogonal structure fabric with a thickness of 2 mm as a preform by three-dimensional weaving technology using 300 tex glass fiber;

[0036] (2) Mix strontium titanate ceramics with a particle size of 1 μm with epoxy resin and a curing agent, and fully stir them through a high-speed mixer to obtain a mixed solution in which strontium titanate ceramics account for 30 wt% of the total content;

[0037] (3) Fill the mixed solution into the three-dimensional orthogonal structure glass fiber preform through the VARTM molding process, control the vacuum degree to be -0.1 MPa, pre-cure at 50 °C for 3 h, and cure at 70 °C for 7 h to obtain a three-dimensional orthogonal structure ceramic-filled glass fiber / epoxy resin temperature-stable microwave composite dielectric material.

[0038] Example 3

[0039] (1) Prepare a three-dimensional angle-interlocked structure aramid fabric with a thickness of 2 mm as a preform by three-dimensional weaving technology using 1500 denier aramid fiber;

[0040] (2) Mix barium titanate ceramics with a particle size of 1 μm with epoxy resin, and fully stir them through a high-speed mixer to obtain a mixed solution in which barium titanate ceramics account for 30 wt% of the total content;

[0041] (3) Fill the mixed solution into the three-dimensional angle-interlocked aramid fabric preform through the VARTM forming process, control the vacuum degree to be -0.1 MPa, pre-cure at 50 °C for 3 h, and cure at 70 °C for 7 h to obtain a temperature-stable microwave composite dielectric material of three-dimensional orthogonal structure ceramic-filled aramid fiber / epoxy resin.

[0042] Example 4

[0043] (1) Prepare a three-dimensional orthogonal fabric with a thickness of 2 mm as the reinforcing aramid fiber by three-dimensional weaving technology using 1500 denier aramid fiber;

[0044] (2) Mix strontium titanate ceramic with a particle size of 1 μm and polyimide resin, and fully stir them through a high-speed mixer to obtain a mixed solution with strontium titanate ceramic accounting for 30 wt% of the total content;

[0045] (3) Through the hand lay-up forming process, evenly coat the mixed solution on the surface of the reinforcing aramid fiber, make the mixed solution fully enter the fabric interior, pre-cure at 160 °C for 30 minutes, pre-cure at 260 °C for 40 minutes, and cure at 310 °C for 40 minutes. During the curing process, an imidization reaction occurs to obtain a three-dimensional orthogonal structure ceramic-filled aramid / polyimide composite dielectric material.

[0046] Example 5

[0047] The preparation method of this example is the same as that of Example 4, except that strontium titanate ceramic accounts for 20 wt% of the mixed solution.

[0048] Comparative Example 1

[0049] Mix 30 wt% of strontium titanate ceramic, 20 wt% of aramid fiber powder, and 50 wt% of polyimide through a high-speed mixer to obtain a mixed solution; place the mixed solution in a mold, pre-cure at 160 °C for 30 minutes, pre-cure at 260 °C for 40 minutes, and cure at 310 °C for 40 minutes to obtain a composite dielectric material plate.

[0050] Comparative Example 2

[0051] The preparation method of this comparative example is the same as that of Example 4, except that strontium titanate ceramic accounts for 0 wt% of the mixed solution.

[0052] Comparative Example 3

[0053] The preparation method of this comparative example is the same as that of Example 4, except that strontium titanate ceramic accounts for 10 wt% of the mixed solution.

[0054] Comparative Example 4

[0055] The preparation method of this comparative example is the same as that of Example 4, except that strontium titanate ceramics account for 35 wt% of the mixed solution.

[0056] The performance of the composite dielectric materials prepared in Examples 1 to 5 and Comparative Examples 1 to 4 was tested respectively, as shown in Table 1.

[0057] Table 1

[0058]

[0059] From the comparison between Examples 1-4 and Comparative Example 1, it can be seen that in the traditional method to improve the mechanical properties of ceramic-polymer materials, the microwave dielectric composite material prepared by adding short fibers to the ceramic-polymer resin can only reach a tensile strength of 75 MPa, but the improvement effect of short fibers on the mechanical properties of the composite material is not significant. In the experimental scheme of this project, a fabric made of high-performance long fibers is used as the reinforcement, and then combined with the ceramic-modified polymer resin. Compared with the ceramic-polymer matrix composite material prepared by the traditional method, the mechanical properties of the composite material are effectively improved. In addition, by using different fiber raw materials and structures, ceramic-modified fiber-reinforced composite materials with different properties can be realized. By selecting fibers and resins, the mechanical properties of the composite material can be further improved, and at the same time, high strength and low resonance frequency temperature coefficient can be achieved.

[0060] From the comparison between Examples 4-5 and Comparative Examples 2-4, it can be seen that by filling ceramic materials into the fiber-reinforced composite material, the dielectric properties of the overall composite material can be successfully regulated as physical modifiers. When the filling content of strontium titanate ceramic particles is 20 wt% - 30 wt%, a low resonance frequency temperature coefficient ( ), thus ensuring the dielectric property stability of the composite material at different temperatures. The resonance frequency temperature coefficient of the microwave dielectric material satisfies the mixing rule, so the overall resonance frequency temperature coefficient can be regulated by adding materials with different resonance frequency temperature coefficients. Strontium titanate ceramics (+1100 ppm / °C) have the opposite resonance frequency temperature coefficient to that of fibers and resins, so the temperature stability of the overall composite material can be effectively improved.

[0061] Although the embodiments of the present invention have been shown and described, for those of ordinary skill in the art, it can be understood that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principles and spirits of the present invention. The scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for preparing a high-strength and temperature-stable composite dielectric material, characterized in that: The ceramic material is uniformly mixed into the polymer resin by high-speed mechanical stirring to obtain a mixed solution, and the preform woven from the fibers is composite-molded with the mixed solution containing the ceramic material and the resin to obtain the high-strength and temperature-stable composite dielectric material; wherein the structure of the preform is a flat stacked fabric structure, a three-dimensional orthogonal structure, or a three-dimensional angle interlocking structure; The ceramic material is selected from strontium titanate; In the mixed solution containing ceramic material and resin, the ceramic material accounts for 20-30wt% of the mixed solution.

2. The method for preparing a high-strength and temperature-stable composite dielectric material according to claim 1, characterized in that: The polymer resin is selected from thermosetting resins or thermoplastic resins.

3. The method for preparing a high-strength and temperature-stable composite dielectric material according to claim 2, characterized in that: The polymer resin is selected from at least one of epoxy resin, polyimide resin, phenolic resin, polytetrafluoroethylene resin, vinyl resin and polypropylene resin.

4. The method for preparing a high-strength and temperature-stable composite dielectric material according to claim 1, characterized in that: The fiber of the preform is selected from at least one of glass fiber, aramid fiber, polyethylene fiber, basalt fiber, polyphenylene sulfide fiber and polytetrafluoroethylene fiber.

5. The method for preparing a high-strength and temperature-stable composite dielectric material according to claim 1, characterized in that: The composite molding process is selected from any one of hand lay-up molding, injection molding, resin transfer molding, vacuum assisted resin transfer molding, hot pressing molding, and autoclave molding.

6. A high-strength and temperature-stable composite dielectric material obtained by the preparation method according to any one of claims 1 to 5, characterized in that: The resonant frequency temperature coefficient of the composite dielectric material is -30ppm / °C~+30°Cppm / °C; the tensile strength of the composite dielectric material is 400~1100MPa.

7. A high-strength and temperature-stable composite dielectric material according to claim 6, characterized in that: The dielectric constant of the composite dielectric material is 3.85-4.5, and the dielectric loss is ≤0.

02.

8. Use of the high-strength and temperature-stable composite dielectric material according to claim 6 or 7 in filters, resonators and microwave dielectric substrates.

Images