Low-dielectric-constant wave-transparent plate and manufacturing method thereof

Abstract

The invention discloses a low-dielectric-constant wave-transparent plate and a manufacturing method thereof, and belongs to the technical field of manufacturing of wave-transparent composite materials. Polyurea with excellent mechanical property and environmental stability is used as a base material, a low molecular polarization group is introduced in the synthesis process of the polyurea to reduce the dielectric constant of the polyurea base material, and the polyurea base material is compounded with low dielectric glass fibers to obtain the wave-transparent plate with lower dielectric constant. The dielectric constant is an important influencing factor of the wave transmission performance, the dielectric constant of the polyurea base material is reduced by adopting a method of combining molecular structure design and composite modification, the wave transmission rate of the plate is further improved, and good application prospects are shown in the field of low electromagnetic scattering structure materials.

Description

Technical Field

[0001] The invention relates to a low dielectric constant wave-transmitting plate material and a manufacturing method thereof, belonging to the technical field of low dielectric constant wave-transmitting composite materials. Background Art

[0002] The rapid development of modern aircraft has brought unprecedented opportunities and challenges to the manufacture of advanced composite materials with integrated functional structures. As an important component, wave-transmitting materials have put forward higher requirements for their comprehensive properties such as mechanical properties and dielectric properties to adapt to the flight environment under complex climatic conditions. Traditional ceramic-based wave-transmitting materials can no longer meet application requirements due to factors such as heavy weight and difficulty in special-shaped processing. Low-dielectric materials play an important role in reducing surface reflection and energy loss of electromagnetic waves. Therefore, reducing the dielectric constant of the material is an important way to achieve low scattering and high wave transmittance. Organic polymers have a low dielectric constant and good processing properties, and have received increasing attention in the field of wave-transmitting materials.

[0003] The dielectric properties of wave-transmitting materials are related to their degree of polarization, and the response strongly depends on the frequency of the electric field. There are two main methods to reduce the dielectric constant of polymer-based wave-transmitting materials: one is to reduce the polarity of the molecule by introducing weakly polar chemical groups into the polymer chain structure; the other is to blend the polymer with a low dielectric filler to achieve the effect of reducing the dielectric constant of the composite material. As the main auxiliary material with low dielectric constant, cage-type silsesquioxane has a unique reactive organic group and usually has a high porosity after being compounded with a polymer, making it an ideal choice for low dielectric wave-transmitting materials. Glass fiber has excellent dielectric properties and dimensional stability. Introducing it into a polymer matrix can significantly enhance the mechanical properties of the composite material. With polyurea as the polymer matrix, cage-type silsesquioxane is grafted into the polyurea chain segment to obtain a modified polyurea with a low dielectric constant, and then low dielectric glass fiber is introduced to further reduce the dielectric constant of the composite material while enhancing the mechanical properties. There has been no public report on obtaining a polyurea sheet with a high wave-transmitting effect. Summary of the invention

[0004] The present invention relates to a low dielectric constant wave-transparent sheet material and a manufacturing method thereof. The dielectric constant of the polyurea sheet material is reduced by introducing cage-type silsesquioxane into a polyurea molecular chain to weaken its molecular polarity. Meanwhile, low dielectric glass fiber is blended with the polyurea slurry to obtain a fiber-reinforced polyurea sheet material having both good mechanical properties and wave-transparent properties. The fiber-reinforced polyurea sheet material has important practical significance in the application of low electromagnetic scattering bearing structures.

[0005] The present invention is achieved through the following technical solutions.

[0006] According to a first aspect of the present invention, a method for manufacturing a low dielectric constant wave-transmitting plate material is provided, comprising the following steps:

[0007] (1) reacting an amino cage silsesquioxane with a diisocyanate at a mass ratio of 0.8 to 1.2 at room temperature to synthesize an isocyanate-terminated cage silsesquioxane as a capping monomer;

[0008] (2) mixing polyetheramine, diisocyanate and polymethylene polyphenyl polyisocyanate in a functional group ratio of 1:0.8 to 1.2:0.2, adding 5 to 10% by weight of a chain extender to react at room temperature for 1 to 2 hours, then adding 10 to 20% by weight of the end-capping monomer obtained in step (1) to continue reacting for 30 to 60 minutes, and then adding water to shear and disperse to obtain a polyurea slurry;

[0009] (3) The polyurea slurry obtained in step (2) is uniformly mixed with low dielectric glass fiber in a mass ratio of 3 to 5, and coated and dried at 80 to 100° C. by a flat plate coating method to obtain a low dielectric constant wave-transparent plate.

[0010] Preferably, the diisocyanate is one or any combination of diphenylmethane diisocyanate and isophorone diisocyanate.

[0011] Preferably, the chain extender is one or any combination of dimethylthiotoluene diamine, polyoxypropylene diamine, and 4,4-bis-sec-butylaminodiphenylmethane.

[0012] Furthermore, the molecular weight of the polyetheramine is 3000-5000; and the average functionality of the polymethylene polyphenyl polyisocyanate is 2.5-2.7.

[0013] Furthermore, main components of the low dielectric glass fiber include silicon dioxide, aluminum oxide, boron oxide, and magnesium oxide.

[0014] According to a second aspect of the present invention, a low dielectric constant wave-transparent plate material is provided, which is manufactured by using the above-mentioned method for manufacturing a low dielectric constant wave-transparent plate material.

[0015] Furthermore, the thickness of the plate is between 0.5 and 1.2 cm, the dielectric constant is lower than 2.8, and the X-band transmittance is higher than 85%.

[0016] The board achieves good wave transmission effect by reducing the dielectric constant of the polyurea substrate, and is suitable for application scenarios such as manufacturing of high-wave transmission and low electromagnetic scattering functional structures.

[0017] Beneficial effects of the present invention:

[0018] The present invention grafts caged silsesquioxane into polyurea chain segments, which significantly improves the wave transmittance of polyurea sheet. Although polyurea has excellent mechanical properties and environmental stability, its molecular chain contains a large number of carbamate groups, which makes polyurea show high polarity, seriously affecting its wave transmittance performance. Caged silsesquioxane is a silicon particle composed of an inorganic Si-O-Si cage "core" and an organic functional group "shell", and has a low molecular polarity. Its cage structure gives caged silsesquioxane a large free volume. Introducing it into the polyurea molecular chain can not only reduce the dipole polarization of the polyurea molecule, but also its high porosity and low molecular polarizability are conducive to reducing the dielectric constant. Therefore, the present invention introduces caged silsesquioxane into the polyurea chain segment, which significantly reduces the dielectric constant of polyurea and improves the wave transmittance of polyurea sheet, the dielectric constant is reduced from 3.6 to 3.2, and the wave transmittance in the X-band is increased from 75% to 86%.

[0019] The present invention adopts low dielectric glass fiber reinforced polyurea sheet material, and its mechanical properties are enhanced while further reducing the dielectric constant of the sheet material. Low dielectric glass fiber has good low dielectric loss and high temperature oxidation resistance, and has the advantages of excellent mechanical properties, high specific modulus and low density. Mixing low dielectric constant glass fiber with polyurea matrix can effectively combine the advantages of organic-inorganic materials, can not only keep the characteristics of light weight, good mechanical properties and excellent processing performance of polyurea matrix, but also have the characteristics of low dielectric properties, high dimensional stability and excellent enhanced mechanical properties of low dielectric glass fiber reinforcement, show good synergistic enhancement effect, achieve good mechanical properties and wave transmission performance of the sheet material, tensile strength is increased from 24MPa to 35MPa, and X-band wave transmission rate can reach up to 93%. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 This is a schematic diagram of the structure of the wave-transmitting composite plate obtained in Example 1.

[0021] Explanation of the numbers in the figure: 1. Polyurea matrix; 2. Cage silsesquioxane; 3. Low dielectric glass fiber. DETAILED DESCRIPTION

[0022] In order to have a clearer understanding of the technical features of the present invention, the technical solution of the present invention is now described in detail below, but it should not be understood as limiting the applicable scope of the present invention.

[0023] Example 1

[0024] (1) Aminated cage silsesquioxane and isophorone diisocyanate were reacted at a mass ratio of 0.8 at room temperature to synthesize isocyanate-terminated cage silsesquioxane as a capping monomer.

[0025]

[0026] (2) Polyetheramine, isophorone diisocyanate and polymethylene polyphenyl polyisocyanate are mixed in a functional group ratio of 1:1.2:0.2, 5% by mass of dimethylthiotoluene diamine is added and reacted at room temperature for 1 hour, then 10% by mass of a capping monomer is added and the reaction is continued for 30 minutes, and then water is added to shear and disperse to obtain a polyurea slurry.

[0027]

[0028] (3) The obtained polyurea slurry and low dielectric glass fiber are uniformly mixed in a mass ratio of 3, and coated and dried at 80° C. by a flat plate coating method to obtain a low dielectric constant wave-transparent sheet.

[0029] Example 2

[0030] (1) Aminated cage silsesquioxane and diphenylmethane diisocyanate were reacted at a mass ratio of 1.0 at room temperature to synthesize isocyanate-terminated cage silsesquioxane as a capping monomer.

[0031] (2) Polyetheramine, diphenylmethane diisocyanate and polymethylene polyphenyl polyisocyanate are mixed in a functional group ratio of 1:1:0.2, and 8% by mass of polyoxypropylene diamine is added to react at room temperature for 1.5 hours. Then, 15% by mass of the end-capping monomer is added to continue the reaction for 50 minutes, and then water is added for shear dispersion to obtain a polyurea slurry.

[0032] (3) The obtained polyurea slurry and low dielectric glass fiber are uniformly mixed in a mass ratio of 4, and coated and dried at 90° C. by a flat plate coating method to obtain a low dielectric constant wave-transparent sheet.

[0033] Example 3

[0034] (1) Aminated cage silsesquioxane and isophorone diisocyanate were reacted at a mass ratio of 1.2 at room temperature to synthesize isocyanate-terminated cage silsesquioxane as a capping monomer.

[0035] (2) Polyetheramine, isophorone diisocyanate and polymethylene polyphenyl polyisocyanate are mixed in a functional group ratio of 1:0.8:0.2, 10% by mass of 4,4-bis-sec-butylaminodiphenylmethane is added and reacted at room temperature for 2 hours, then 20% by mass of a capping monomer is added and the reaction is continued for 60 minutes, and then water is added to shear and disperse to obtain a polyurea slurry.

[0036] (3) The obtained polyurea slurry and low dielectric glass fiber are uniformly mixed at a mass ratio of 5, and coated and dried at 100° C. by a flat plate coating method to obtain a low dielectric constant wave-transparent sheet.

[0037] Comparative Example 1

[0038] (1) Aminated cage silsesquioxane and isophorone diisocyanate were reacted at a mass ratio of 1.0 at room temperature to synthesize isocyanate-terminated cage silsesquioxane as a capping monomer.

[0039] (2) Polyetheramine, isophorone diisocyanate and polymethylene polyphenyl polyisocyanate are mixed in a functional group ratio of 1:1:0.2, 8% by mass of polyoxypropylene diamine is added and reacted at room temperature for 1.5 hours, then 15% by mass of end-capping monomer is added and the reaction is continued for 50 minutes, and then water is added for shear dispersion to obtain a polyurea slurry.

[0040] (3) The obtained polyurea slurry is coated and dried at 90° C. by a flat plate coating method to obtain a cage-type silsesquioxane grafted polyurea sheet.

[0041] Comparative Example 2

[0042] (1) Hexamethylenediamine and isophorone diisocyanate were reacted at a mass ratio of 0.8 at room temperature to synthesize isocyanate-terminated cage-type silsesquioxane as a capping monomer.

[0043] (2) Polyetheramine, isophorone diisocyanate and polymethylene polyphenyl polyisocyanate are mixed in a functional group ratio of 1:1:0.2, 8% by mass of polyoxypropylene diamine is added and reacted at room temperature for 1.5 hours, then 15% by mass of end-capping monomer is added and the reaction is continued for 50 minutes, and then water is added for shear dispersion to obtain a polyurea slurry.

[0044] (3) The obtained polyurea slurry is coated and dried at 90° C. using a flat plate coating method to obtain a polyurea sheet.

[0045] The dielectric constants of the plates obtained in Examples 1 to 3 and Comparative Examples 1 to 2 and their average transmittance parameters in the X-band are listed in Table 1. The results show that cage-type silsesquioxane grafted polyurea can significantly reduce the dielectric constant of the plate, and the introduction of low-dielectric glass fiber further reduces the dielectric constant of the plate. The lower the dielectric constant, the higher the transmittance. Cage-type silsesquioxane and low-dielectric glass fiber play a positive role in enhancing the transmittance of polyurea plates.

[0046] Table 1 Wave absorption performance parameters of the samples obtained in the embodiments and comparative examples

[0047] Example Example 1 Example 2 Example 3 Comparative Example 1 Comparative Example 2 Dielectric constant 3.1 2.8 3.0 3.2 3.6 Average wave transmittance (%) 85.1 88.7 85.4 86.2 75.1

Claims

1. A method for manufacturing a low dielectric constant wave-transmitting sheet material, comprising the following steps: (1) reacting an amino cage silsesquioxane with a diisocyanate at a mass ratio of 0.8 to 1.2 at room temperature to synthesize an isocyanate-terminated cage silsesquioxane as a capping monomer; (2) mixing polyetheramine, diisocyanate and polymethylene polyphenyl polyisocyanate in a functional group ratio of 1:0.8 to 1.2:0.2, adding 5 to 10% by weight of a chain extender to react at room temperature for 1 to 2 hours, then adding 10 to 20% by weight of the end-capping monomer obtained in step (1) to continue reacting for 30 to 60 minutes, and then adding water to shear and disperse to obtain a polyurea slurry; (3) The polyurea slurry obtained in step (2) is uniformly mixed with low dielectric glass fiber in a mass ratio of 3 to 5, and coated and dried at 80 to 100° C. by a flat plate coating method to obtain a low dielectric constant wave-transparent plate.

2. The method for manufacturing a low dielectric constant wave-transmitting plate material according to claim 1, characterized in that: The diisocyanate is one of diphenylmethane diisocyanate and isophorone diisocyanate or any combination thereof.

3. The method for manufacturing a low dielectric constant wave-transmitting plate material according to claim 1, characterized in that: The chain extender is one or any combination of dimethylthiotoluene diamine, polyoxypropylene diamine, and 4,4-bis-sec-butylamino diphenylmethane.

4. The method for manufacturing a low dielectric constant wave-transmitting plate material according to claim 1, characterized in that: The molecular weight of the polyetheramine is 3000-5000; the average functionality of the polymethylene polyphenyl polyisocyanate is 2.5-2.

7.

5. The low dielectric constant wave-transmitting plate material and the manufacturing method thereof according to claim 1, characterized in that: The low dielectric glass fiber comprises a combination of one or more of silicon dioxide, aluminum oxide, boron oxide and magnesium oxide.

6. A low dielectric constant wave-transmitting sheet material, characterized in that: The low dielectric constant wave-transparent plate material and the manufacturing method thereof are used to obtain the low dielectric constant wave-transparent plate material as described in any one of claims 1 to 5.

7. The low dielectric constant wave-transmitting plate material according to claim 6, characterized in that: The thickness of the plate is between 0.5 and 1.2 cm.

8. The low dielectric constant wave-transmitting plate material according to claim 6, characterized in that: The dielectric constant of the wave-transmitting sheet is lower than 2.8, and the X-band wave transmittance is higher than 85%.

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