Preparation method of benzocyclobutene modified cyanate ester composite material

Abstract

The invention belongs to the field of aviation composite material manufacturing, and particularly relates to a preparation method of a benzocyclobutene modified cyanate ester composite material. Common high-temperature-resistant resin cannot have the characteristics of low dielectric, low loss, high temperature resistance and thermal oxidative aging resistance at the same time. The preparation method comprises the following steps: adding chloroplatinic acid with the mass fraction of 1%-5% into a benzocyclobutene monomer, and carrying out prepolymerization to obtain a benzocyclobutene prepolymer with the viscosity of 500-1000 mpas; the preparation method comprises the following steps: carrying out copolymerization on a benzocyclobutene prepolymer and cyanate ester according to a molar ratio of (1: 9)-(1: 1) to obtain a benzocyclobutene modified cyanate ester copolymer with the viscosity of 5000mpas-20000mpas; coating the release paper with the modified cyanate ester copolymer by using a hot melting method prepreg machine, wherein the coating temperature is 50-100 DEG C; then the benzocyclobutene modified phenolic aldehyde type cyanate ester prepreg is obtained through compounding with a fiber fabric, the compounding temperature is 50-100 DEG C, and the glue content of the prepreg is 33%-43%; and laminating and curing a certain number of layers of prepreg according to the thickness. The high temperature resistance and thermo-oxidative aging resistance of the cyanate ester resin can be improved, and the characteristics of low dielectric constant and low loss of the cyanate ester resin are maintained. The requirements of the high-temperature-resistant thermo-oxidative-aging-resistant wave-transparent resin-based composite material for the radome are met.

Description

Technical Field

[0001] This invention belongs to the field of aerospace composite material manufacturing, specifically relating to a method for preparing benzocyclobutene-modified cyanate ester composite materials. Background Technology

[0002] With the development of aircraft radar technology and the continuous increase in radar power, the requirements for composite materials used in radomes are becoming increasingly stringent. Not only are composite materials for radomes required to possess excellent mechanical properties such as low dielectric constant and low loss, but they also need to have high-temperature resistance and resistance to thermo-oxidative aging.

[0003] Currently used high-temperature resistant resins cannot simultaneously possess both low dielectric strength and low loss, as well as high-temperature resistance and resistance to thermo-oxidative aging. For example, phenolic cyanate esters have low dielectric strength and low loss, but their mechanical properties deteriorate significantly after long-term high-temperature aging. Benzocyclobutene is a large class of functional polymer materials that possess both low dielectric strength and low loss, as well as high-temperature resistance, but when used directly as composite materials, its strength and modulus are relatively low, failing to meet the requirements for radome composite materials. Other thermosetting resins, such as cyano resins, have poor dielectric properties and high curing temperatures, limiting their use in radomes. Although silyl acetylenic resins have excellent high-temperature aging resistance, their low interlayer bonding strength with fibers also fails to meet the application requirements. Summary of the Invention

[0004] The main technical problem solved by this invention is to provide a method for preparing benzocyclobutene-modified cyanate ester composite materials.

[0005] This invention proposes a method for preparing benzocyclobutene-modified cyanate ester composite materials, the method comprising the following steps: S1. Add 1% to 5% chloroplatinic acid by mass to benzocyclobutene monomer, and prepolymerize to obtain benzocyclobutene prepolymer with a viscosity of 500 to 1000 mpa•s; S2. Benzocyclobutene prepolymer and cyanate ester are copolymerized in a molar ratio of 1:9 to 1:1 to obtain a benzocyclobutene modified cyanate ester copolymer with a viscosity of 5000 mpa•s to 20000 mpa•s. S3. Apply a hot-melt prepreg-modified cyanate copolymer coating to the release paper at a temperature of 50–100°C. S4, then compounded with fiber fabric to obtain benzocyclobutene modified phenolic cyanate prepreg, the compounding temperature is 50-100℃, and the sizing content of the prepreg is 33%-43%; S5. Based on the thickness, a certain number of prepreg layers are first cured at 100℃~150℃ and curing pressure of 0.1~1MPa for 1h~2h, and then cured at 150℃~300℃ and curing pressure of 0.1~1MPa for 6~10h to obtain benzocyclobutene modified cyanate ester composite material.

[0006] Advantageously, the prepolymerization temperature is 150–200°C and the prepolymerization time is 1–5 h.

[0007] Advantageously, the benzocyclobutene includes fluorinated bisbenzocyclobutene or ether-based bisbenzocyclobutene.

[0008] Advantageously, the copolymerization temperature is 100°C to 200°C, and the time is 1 hour to 5 hours.

[0009] Advantageously, the cyanate ester is any one of phenolic cyanate ester, bisphenol A cyanate ester, or bisphenol AF cyanate ester.

[0010] Advantageously, the material of the fiber fabric is selected from quartz fiber, alkali-free glass fiber, PBO organic fiber or PI organic fiber.

[0011] Advantageously, the combined pressure in step S4 is 50N to 80N.

[0012] Advantageously, the heating rate between the two curing stages in step S5 is not less than 1 °C / min.

[0013] Beneficial effects: This invention not only improves the high-temperature resistance and thermo-oxidative aging resistance of cyanate ester resin, but also maintains its inherent low dielectric constant and low loss characteristics. It meets the demand for high-temperature resistant and thermo-oxidative aging resistant translucent resin-based composite materials for radar domes.

[0014] Meanwhile, this method is simple in process, has a low curing temperature, and is environmentally friendly by not producing waste gas. Detailed Implementation

[0015] Examples of the preparation method of the benzocyclobutene-modified cyanate ester composite material of the present invention are as follows: S1. Add 1% chloroplatinic acid by mass to benzocyclobutene monomer and prepolymerize at 150°C for 2 hours to prepare benzocyclobutene prepolymer with a viscosity of 1000 mpa·s. S2. Benzocyclobutene prepolymer and phenolic cyanate were copolymerized at a molar ratio of 1:5 at 150℃ for 2 hours to obtain a benzocyclobutene-modified cyanate copolymer. The viscosity at room temperature was measured to be 15000 mPa·s using a viscometer. S3. A modified cyanate copolymer for hot-melt prepreg is coated onto release paper, and then laminated with a 0.2 mm thick quartz fiber fabric. The coating and lamination temperatures are both 65℃, resulting in 50 meters of benzocyclobutene-modified phenolic cyanate prepreg. The adhesive content is 38%. S4. The 10 layers of prepreg were cured at 120°C and 0.3 MPa for 2 hours, and then cured at 270°C and 0.3 MPa for 8 hours to obtain a quartz fiber reinforced benzocyclobutene modified phenolic cyanate composite material.

[0016] The composite material was prepared by machining and its mechanical properties were tested. The test results are shown in Table 1 below. As can be seen from the data in Table 1, the composite material prepared by this method has high resistance to high temperature and thermo-oxidative aging.

[0017] Table 1 Mechanical properties of composite materials

Claims

1. A method for preparing a benzocyclobutene-modified cyanate ester composite material, characterized in that, The method includes the following steps: S1. Add 1% to 5% chloroplatinic acid by mass to benzocyclobutene monomer, and prepolymerize to obtain benzocyclobutene prepolymer with a viscosity of 500 to 1000 mpa•s; S2. Benzocyclobutene prepolymer and cyanate ester are copolymerized in a molar ratio of 1:9 to 1:1 to obtain a benzocyclobutene modified cyanate ester copolymer with a viscosity of 5000 mpa•s to 20000 mpa•s. S3. Apply a hot-melt prepreg-modified cyanate copolymer coating to the release paper at a temperature of 50–100°C. S4, then compounded with fiber fabric to obtain benzocyclobutene modified phenolic cyanate prepreg, the compounding temperature is 50-100℃, and the sizing content of the prepreg is 33%-43%; S5. Based on the thickness, a certain number of prepreg layers are first cured at 100℃~150℃ and curing pressure of 0.1~1MPa for 1h~2h, and then cured at 150℃~300℃ and curing pressure of 0.1~1MPa for 6~10h to obtain benzocyclobutene modified cyanate ester composite material.

2. The method for preparing benzocyclobutene-modified cyanate ester composite material according to claim 1, characterized in that: The prepolymerization temperature is 150–200℃, and the prepolymerization time is 1–5 h.

3. The method for preparing the benzocyclobutene-modified cyanate ester composite material according to claim 1, characterized in that: The benzocyclobutene includes fluorinated bisbenzocyclobutene or ether-based bisbenzocyclobutene.

4. The method for preparing the benzocyclobutene-modified cyanate ester composite material according to claim 1, characterized in that: The copolymerization temperature is 100℃~200℃, and the time is 1h~5h.

5. The method for preparing the benzocyclobutene-modified cyanate ester composite material according to claim 1, characterized in that: The cyanate ester is any one of phenolic cyanate ester, bisphenol A cyanate ester, or bisphenol AF cyanate ester.

6. The method for preparing the benzocyclobutene-modified cyanate ester composite material according to claim 1, characterized in that: The material of the fiber fabric is selected from quartz fiber, alkali-free glass fiber, PBO organic fiber or PI organic fiber.

7. The method for preparing the benzocyclobutene-modified cyanate ester composite material according to claim 1, characterized in that: In step S4, the combined pressure is 50N to 80N.

8. The method for preparing the benzocyclobutene-modified cyanate ester composite material according to claim 1, characterized in that: The heating rate between the two curing stages in step S5 is not less than 1℃ / min.

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