A method for modifying quartz fiber and applications thereof

Abstract

A modification method and application of quartz fiber belong to the technical field of quartz fiber reinforced silicone resin composite material. The specific scheme comprises the following steps: step one, cleaning quartz fiber by oxygen plasma; step two, placing the cleaned quartz fiber in a tetramethylammonium hydroxide aqueous solution for amination reaction; step three, placing the aminated quartz fiber in anhydrous tetrahydrofuran and adding chlorosilane for reaction, adding alkoxy silane and deionized water to the reaction system after the reaction is completed, and heating for reaction to obtain modified quartz fiber. The modified quartz fiber is combined with silicone resin to prepare a modified quartz fiber reinforced silicone resin composite material by means of hot press tank molding. The preparation method is simple in operation, can improve the high-temperature mechanical properties of the quartz fiber reinforced silicone resin while maintaining the excellent high-temperature resistance of the quartz fiber reinforced silicone resin, and is conducive to large-scale production and use.

Description

Technical Field

[0001] This invention belongs to the technical field of quartz fiber reinforced silicone resin composite materials, specifically relating to a method for modifying quartz fibers and their application in high-temperature resistant silicone resin composite materials. Background Technology

[0002] Resin-based composite materials possess advantages such as high specific strength and specific modulus, relatively simple manufacturing processes, short production cycles, and low costs, making them the most widely used material for radomes. Resin-based radome composites consist of a resin matrix and reinforcing fibers. Resin matrices include epoxy resin, phenolic resin, cyanate ester resin, bismaleimide resin, and polyimide resin. However, due to the easy oxidation and decomposition of C-C bonds, the service temperature limit of these resin matrices is around 500℃, which is insufficient for requirements above 500℃. With the development of modern aerospace and space exploration, the flight speeds of rockets, missiles, and aircraft are constantly increasing, placing higher demands on the wave transmission performance, high-temperature resistance, and mechanical properties of radome materials.

[0003] The Si-O bond energy of the Si-O-Si framework structure of silicone resin is as high as 450 kJ / mol, which is higher than that of carbon-carbon bond energy (345.6 kJ / mol). It is not easy to break or decompose under high temperature and radiation environment. Due to this special structure, silicone resin has excellent thermal oxidation properties, which allows it to be used at 500-600℃ for a short time. As a high temperature resistant radome, it is increasingly widely used in the aerospace field.

[0004] Quartz fiber is one of the commonly used reinforcing fibers in high-temperature resistant resin-based radome composites. Quartz fiber has a SiO2 content greater than 99.95%, a tensile strength as high as 1700 MPa, a Young's modulus of 72.0 GPa, an elongation at break of 4.6%, a dielectric constant of 3.78, and a dielectric loss of 0.0002. Composites prepared by combining quartz fiber with high-temperature resistant resin exhibit good high-temperature resistance and wave transmission properties. However, to improve the interfacial bonding between quartz fiber and the resin matrix, commercially available quartz fibers use epoxy or epoxy K impregnating agents. These two impregnating agents have poor high-temperature resistance, beginning to decompose at around 300°C. The decomposition of the impregnating agent rapidly reduces the interfacial bonding between the composite material and the matrix resin, leading to a decrease in the high-temperature mechanical properties of the composite material. Summary of the Invention

[0005] In order to overcome the shortcomings of the prior art and improve the mechanical properties and high-temperature mechanical property retention rate of quartz fiber reinforced silicone resin composites, the present invention provides a method for modifying quartz fibers and its application.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] A method for modifying quartz fibers, comprising the following steps:

[0008] Step 1: Place the cut quartz fibers in an oxygen plasma machine and clean them with oxygen plasma to obtain cleaned quartz fibers.

[0009] Step 2: Arrange the cleaned quartz fibers in a tetramethylammonium hydroxide aqueous solution to carry out an ammoniation reaction. After the reaction is completed, wash and dry to obtain ammoniation quartz fibers.

[0010] Step 3: Place the ammonium-modified quartz fiber in anhydrous tetrahydrofuran and add chlorosilane to react. After the reaction is complete, add alkoxysilane and deionized water to the reaction system, heat the reaction, and wash and dry after the reaction to obtain modified quartz fiber.

[0011] An application of the modified quartz fiber includes the following steps:

[0012] A prepreg was prepared by combining modified quartz fiber and silicone resin, and the prepreg was then molded in an autoclave to obtain a modified quartz fiber reinforced silicone resin composite material.

[0013] Furthermore, the preparation steps of the prepreg are as follows: First, dissolve the silicone resin in xylene, place the modified quartz fiber on the release paper, evenly coat the silicone resin on the modified quartz fiber, and finally place it in a fume hood to evaporate the organic solvent at room temperature for 4 to 8 hours.

[0014] Compared with the prior art, the beneficial effects of the present invention are:

[0015] This invention employs oxygen plasma to remove the wetting agent from the surface of quartz fibers, thereby etching the surface of the quartz fibers. Subsequently, tetramethylammonium hydroxide aqueous solution reacts with silica on the surface of the quartz fibers to generate tetramethylammonium silicate, obtaining a modified quartz fiber cloth containing tetramethylammonium silicate on the surface. The ammonium-modified quartz fiber cloth is then modified with chlorosilanes and alkoxysilanes to obtain modified quartz fibers, improving the bonding force with the silicone resin matrix and thus improving the mechanical properties of the composite material.

[0016] This invention uses an autoclave molding method to composite modified quartz fiber cloth with a silicone resin matrix. The operation is simple and facilitates the bonding between the modified quartz fiber cloth and the silicone resin matrix, thereby obtaining a modified quartz fiber silicone resin composite material with excellent mechanical properties and heat resistance.

[0017] The preparation method of the present invention is simple to operate and can improve the high-temperature mechanical properties of quartz fiber reinforced silicone resin while maintaining its excellent high-temperature resistance, which is conducive to its promotion and large-scale production and use. Attached Figure Description

[0018] Figure 1This is a flowchart of the preparation process for modified quartz fiber reinforced silicone resin composite materials;

[0019] Figure 2 This is a schematic diagram illustrating the modification principle of quartz fiber. Detailed Implementation

[0020] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings and embodiments. Obviously, the described embodiments are only some embodiments of the invention, not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0021] Example 1:

[0022] ① A method for modifying quartz fibers, including the following steps:

[0023] Quartz fiber cloth with a thickness of 0.1 mm was cut into 22 squares of 20×20 cm each, weighing 94.16 g. These were then placed in an oxygen plasma cleaner to remove the epoxy sizing agent from the surface of the quartz fiber cloth. The cleaned quartz fiber was then placed in 150 g of a 0.02 mol / L tetramethylammonium hydroxide aqueous solution and subjected to an ammoniation reaction at 50 °C. The ammoniation-treated quartz fiber cloth was then placed in 500 g of anhydrous tetrahydrofuran and 1 g of methyltrichlorosilane, 0.5% dimethyldichlorosilane, and 0.5% methylphenyldichlorosilane were added. The mixture was reacted at 30 °C for 4 h. After the reaction, a mixture of 10 g of methyltriethoxysilane and 5 g of dimethyldiethoxysilane and 15 g of deionized water was added to the system. The mixture was heated and reacted at 50 °C for 12 h. The resulting product was washed and dried to obtain modified quartz fiber.

[0024] ② Prepreg preparation

[0025] Modified quartz fibers were laid flat on release paper. 62.77 g of methylphenyl silicone resin was weighed, with a mass ratio of modified quartz fiber to silicone resin of 40:60. The silicone resin was added to 62.77 g of xylene and stirred until dissolved. After the silicone resin dissolved, it was evenly coated onto the surface of the modified quartz fibers. The coated modified quartz fibers were then placed in a fume hood to evaporate the solvent for 4 hours. After solvent evaporation, modified quartz fiber / silicone resin prepreg was obtained.

[0026] ③ Preparation of composite materials

[0027] The 22-layer prepreg prepared above was aligned and laid on a flat mold to prepare a vacuum bag. The bag was placed in an autoclave and vacuumed, with the vacuum level controlled to be ≤0.01MPa. The curing regime was as follows: pressurize to 50kPa at room temperature and heat to 150℃ at 1℃ / min, hold at 150℃ for 40min, pressurize to 200kPa at 15kPa / min and hold for 20min; pressurize to 1000kPa at 40kPa / min, then heat to 200℃ at 1℃ / min, hold at 1000kPa for 120min; heat to 250℃ at 1℃ / min, hold at 1000kPa for 120min; heat to 300℃ at 1℃ / min, hold at 1000kPa for 120min; after curing, cool to room temperature at 2℃ / min and demold to obtain the modified quartz fiber reinforced silicone resin composite material – Sample I.

[0028] Comparative Example 1

[0029] The difference between this comparative example and Example 1 is that: unmodified quartz fiber is used, and the preparation of prepreg and composite material is the same as in Example 1. Unmodified quartz fiber reinforced silicone resin composite material - Sample II is prepared.

[0030] Table 1 shows a comparison of the properties of the modified quartz fiber reinforced silicone resin composite sample I and the unmodified quartz fiber reinforced silicone resin composite sample II prepared using the methods described in Example 1 and Comparative Example 1. Compared with the unmodified quartz fiber reinforced silicone resin composite sample II prepared in Comparative Example 1, the modified quartz fiber reinforced silicone resin composite sample I prepared in Example 1 of this invention exhibits a 193.6% increase in flexural strength at 500℃ and a 304.4% increase in interlaminar shear strength.

[0031] Table 1

[0032]

[0033]

[0034] Example 2

[0035] ① A method for modifying quartz fibers, including the following steps:

[0036] Quartz fiber cloth with a thickness of 0.14 mm was cut into squares of 25×25 cm, with a total of 18 layers and a weight of 178.75 g. These were then placed in an oxygen plasma cleaner to remove the epoxy sizing agent from the surface of the quartz fiber cloth. The cleaned quartz fibers were then placed in 300 g of a 0.01 mol / L tetramethylammonium hydroxide aqueous solution at 60 °C for ammoniation. The ammoniation-treated quartz fiber cloth was then placed in 800 g of anhydrous tetrahydrofuran and 1.5 g of methyltrichlorosilane, 1.5 g of dimethyldichlorosilane, 1.2 g of methylphenyldichlorosilane, and 1.0 g of phenyltrichlorosilane were added. The reaction was carried out at 40 °C for 2 h. After the reaction, a mixture of 15 g of methyltriethoxysilane and 12 g of dimethyldiethoxysilane and 25 g of deionized water were added to the system. The mixture was heated to 60 °C for 8 h. The resulting product was washed and dried to obtain modified quartz fiber.

[0037] ② Prepreg preparation

[0038] Modified quartz fibers were laid flat on release paper. 96.25 g of methylphenyl silicone resin was weighed, with a mass ratio of modified quartz fiber to silicone resin of 35:65. The silicone resin was added to 96.25 g of xylene and stirred until dissolved. After the silicone resin dissolved, it was evenly coated onto the surface of the modified quartz fibers. The coated modified quartz fibers were then placed in a fume hood to evaporate the solvent for 6 hours. After solvent evaporation, modified quartz fiber / silicone resin prepreg was obtained.

[0039] ③ Preparation of composite materials

[0040] The 18 layers of prepreg prepared above were aligned and laid on a flat mold to prepare a vacuum bag. The bag was placed in an autoclave and vacuumed, with the vacuum level controlled to be ≤0.01MPa. The curing regime was as follows: pressurize to 80kPa at room temperature and heat to 150℃ at 1℃ / min, hold at 150℃ for 40min, pressurize to 200kPa at 15kPa / min and hold for 20min; pressurize to 1000kPa at 40kPa / min, then heat to 200℃ at 1℃ / min, hold at 1000kPa for 120min; heat to 250℃ at 1℃ / min, hold at 1000kPa for 120min; heat to 300℃ at 1℃ / min, hold at 1000kPa for 120min; after curing, cool to room temperature at 2℃ / min and demold to obtain the modified quartz fiber reinforced silicone resin composite material - Sample III.

[0041] Comparative Example 2

[0042] The difference between this comparative example and Example 2 is that: unmodified quartz fiber is used, and the preparation of prepreg and composite material is the same as in Example 2. Unmodified quartz fiber reinforced silicone resin composite material - Sample IV is prepared.

[0043] Table 2 shows a comparison of the properties of the modified quartz fiber reinforced silicone resin composite sample III and the unmodified quartz fiber reinforced silicone resin composite sample IV prepared using the methods described in Example 2 and Comparative Example 2. Compared with the unmodified quartz fiber reinforced silicone resin composite sample IV prepared in Comparative Example 2, the modified quartz fiber reinforced silicone resin composite sample III prepared in Example 2 of this invention exhibits a 180.9% increase in flexural strength at 500℃ and a 244.3% increase in interlaminar shear strength.

[0044] Table 2

[0045]

[0046] Example 3

[0047] ① A method for modifying quartz fibers, including the following steps:

[0048] Quartz fiber cloth with a thickness of 0.28 mm was cut into 30×30 cm squares, 10 layers in total, with a weight of 256.5 g. The cloth was placed in an oxygen plasma cleaner to remove the epoxy sizing agent from the surface of the quartz fiber cloth. The cleaned quartz fiber was then placed in 500 g of 0.05 mol / L tetramethylammonium hydroxide aqueous solution and reacted at 60 °C for ammoniation. The ammoniation-treated quartz fiber cloth was then placed in 1000 g of anhydrous tetrahydrofuran and 4 g of methyltrichlorosilane, 2 g of dimethyldichlorosilane, 2 g of methylphenyldichlorosilane, and 2 g of phenyltrichlorosilane were added. The mixture was reacted at 45 °C for 4 h. After the reaction, a mixture of 15 g of methyltriethoxysilane and 10 g of dimethyldiethoxysilane and 40 g of deionized water was added to the system. The mixture was heated to 65 °C for 12 h. The resulting product was washed and dried to obtain modified quartz fiber.

[0049] ② Prepreg preparation

[0050] Modified quartz fibers were laid flat on release paper. 171.0 g of methylphenyl silicone resin was weighed, with a mass ratio of modified quartz fiber to silicone resin of 40:60. The silicone resin was added to 171.0 g of xylene and stirred until dissolved. After the silicone resin dissolved, it was evenly coated onto the surface of the modified quartz fibers. The coated modified quartz fibers were then placed in a fume hood to evaporate the solvent for 8 hours. After solvent evaporation, modified quartz fiber / silicone resin prepreg was obtained.

[0051] ③ Preparation of composite materials

[0052] The 10 layers of prepreg prepared above were aligned and laid on a flat mold to prepare a vacuum bag. The bag was placed in an autoclave and vacuumed, with the vacuum level controlled to be ≤0.01MPa. The curing regime was as follows: pressurize to 40kPa at room temperature and increase the temperature by 1℃ / min to 150℃, hold at 150℃ for 40min, increase the pressure to 200kPa at 15kPa / min, and continue to hold for 20min; increase the pressure to 1000kPa at 40kPa / min, then increase the temperature to 200℃ at 1℃ / min, hold at 1000kPa, and hold for 120min; increase the temperature to 250℃ at 1℃ / min, hold at 1000kPa, and hold for 120min; increase the temperature to 300℃ at 1℃ / min, hold at 1000kPa, and hold for 120min; after curing, cool to room temperature at 2℃ / min and demold to obtain the modified quartz fiber reinforced silicone resin composite material - sample V.

[0053] Comparative Example 3

[0054] The difference between this comparative example and Example 3 is that: unmodified quartz fiber is used, and the preparation of prepreg and composite material is the same as in Example 3. Unmodified quartz fiber reinforced silicone resin composite material - Sample VI is prepared.

[0055] Table 3 shows a comparison of the properties of the modified quartz fiber reinforced silicone resin composite sample V prepared using the methods described in Example 3 and Comparative Example 3, and the unmodified quartz fiber reinforced silicone resin composite sample VI. Compared with the unmodified quartz fiber reinforced silicone resin composite sample VI prepared in Comparative Example 3, the modified quartz fiber reinforced silicone resin composite sample V prepared in Example 3 of this invention exhibits a 193.2% increase in flexural strength at 500℃ and a 127.7% increase in interlaminar shear strength.

[0056] Table 3

[0057]

[0058] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A method for modifying quartz fibers, characterized in that, Includes the following steps: Step 1: Clean the quartz fiber using oxygen plasma; Step 2: Place the cleaned quartz fiber in a tetramethylammonium hydroxide aqueous solution for ammoniation reaction; Step 3: Place the ammonium-modified quartz fiber in anhydrous tetrahydrofuran and add chlorosilane to react. After the reaction is complete, add alkoxysilane and deionized water to the reaction system and heat the reaction to obtain modified quartz fiber.

2. The method for modifying quartz fiber according to claim 1, characterized in that: In step two, the concentration of the tetramethylammonium hydroxide aqueous solution is 0.01 mol / L to 0.05 mol / L, the mass ratio of the tetramethylammonium hydroxide aqueous solution to the quartz fiber is 50 to 200:100, and the reaction temperature is 25 to 60°C.

3. The method for modifying quartz fiber according to claim 1, characterized in that: In step three, the mass ratio of chlorosilane to quartz fiber is 0.5 to 5:100, the reaction temperature of chlorosilane and quartz fiber is 25 to 45°C, and the reaction time is 2 to 4 hours.

4. The method for modifying quartz fiber according to claim 1, characterized in that: In step three, the chlorosilane includes a combination of multiple of methyltrichlorosilane, dimethyldichlorosilane, methylphenyldichlorosilane, and phenyltrichlorosilane mixed in any proportion.

5. The method for modifying quartz fiber according to claim 1, characterized in that: In step three, the mass ratio of alkoxysilane to quartz fiber is 1–20:100; the mass ratio of deionized water to alkoxysilane is 0.5–5:1; the reaction temperature is 50–65°C; and the reaction time is 4–12 hours.

6. The method for modifying quartz fiber according to claim 1, characterized in that: In step three, the alkoxysilane is a mixture of methyltriethoxysilane and dimethyldiethoxysilane in any proportion.

7. The method for modifying quartz fiber according to claim 1, characterized in that: In step three, the mass ratio of tetrahydrofuran to quartz fiber is 1 to 10:

1.

8. The application of a modified quartz fiber prepared by the modification method according to any one of claims 1-7, characterized in that: The modified quartz fiber is combined with silicone resin and then molded in an autoclave to obtain a modified quartz fiber reinforced silicone resin composite material.

9. The application according to claim 8, characterized in that: The silicone resin includes one of methyl silicone resin, phenyl silicone resin and methylphenyl silicone resin, and the mass ratio of silicone resin to modified quartz fiber is 30:70 to 40:

60.

10. The application according to claim 8, characterized in that: The autoclave curing process is as follows: pressurize at room temperature by 10-100 kPa and heat to 150°C at 1°C / min, hold at 150°C for 40 min, pressurize to 200 kPa at 15 kPa / min, and continue to hold at 150°C for 20 min. The pressure is increased to 1000 kPa at a rate of 40 kPa / min, then the temperature is increased to 200 °C at a rate of 1 °C / min, and the pressure is maintained at 1000 kPa. Hold at this temperature for 120 minutes; increase the temperature to 250℃ at a rate of 1℃ / min, hold at a pressure of 1000kPa, and hold for 120 minutes; then increase the temperature to 300℃ at a rate of 1℃ / min. Hold pressure at 1000 kPa and heat for 120 min; after curing, cool to room temperature at 2℃ / min and demold.

Images