Large-thickness ultra-low-density high-toughness silicone rubber heat-proof coating as well as preparation method and application thereof

Abstract

The invention relates to a large-thickness ultra-low-density high-toughness silicone rubber heat-proof coating as well as a preparation method and application thereof, and belongs to the technical field of heat-proof coatings. The formula of the coating is optimally designed, and purified methyl diphenyl silicone rubber and large, medium and small hollow microspheres with different density sizes in a specific ratio are adopted, so that the high-toughness silicone rubber heat-proof coating is prepared. The silicon rubber heat-proof coating prepared from the silicon rubber, the reinforcing filler, the cork powder, the high-temperature-resistant antioxidant filler, the glass fiber, the tetraalkoxysilane, the polysilazane and the like is high in lightweight degree, good in toughness, capable of being sprayed in a large-thickness mode and good in ablation resistance, and the silicon rubber heat-proof coating passes ablation tests of a quartz lamp with the highest heat flux of 90 KW / m < 2 > in the CO2 atmosphere and a wind tunnel. Compared with the prior art, the high-strength and high-toughness coating has the advantages that the high-strength and high-toughness coating is low in density and better in toughness, the density is as low as 0.24-0.28 g / cm < 3 >, the elongation at break is as high as 15%-25%, and the high-strength and high-toughness coating can be sprayed in a large-thickness manner, is good in environmental adaptability and

Description

Technical Field

[0001] The invention relates to a room temperature curing large thickness ultra-low density high toughness silicone rubber heat protection coating and a preparation method and application thereof, which can be applied to the heat protection of the outer surface of the back cover structure of a space probe, and belongs to the technical field of heat protection coatings. Background Art

[0002] The entry cabin structure of a planetary probe lander is generally divided into a back cover structure and a large bottom structure, which mainly protects the lander during flight, orbiting, and landing. When a planetary lander enters the planetary atmosphere, the flight speed can reach more than 10 Ma, and the probe surface is severely aerodynamically heated. The maximum heat flux of a typical back cover structure during flight is 90kw / m 2 Therefore, a heat-resistant structure must be used to ensure the flight safety of the probe. The heat-resistant coating has the advantages of low density, simple construction process, and high heat-resistant efficiency. It is the preferred material solution for the low heat flow part of the probe. Due to the limited carrying capacity of the rocket, the lightweight requirements of the probe are very stringent. The density of the heat-resistant coating needs to be controlled at 0.3g / cm 3 It has the characteristics of high toughness, large thickness spraying, and resistance to high and low temperature changes. Summary of the invention

[0003] The purpose of the present invention is to overcome the above-mentioned deficiencies of the prior art and to provide a thick, ultra-low-density, high-toughness silicone rubber thermal protection coating and its preparation method and application, which can meet the thermal protection requirements of aerodynamic scouring during planetary re-entry and has excellent resistance to space environment, thereby solving the problems of high density and poor lightweight of existing thermal protection coatings.

[0004] The above-mentioned purpose of the present invention is mainly achieved through the following technical solutions:

[0005] A thick, ultra-low-density, high-toughness silicone rubber heat-resistant coating, the raw materials of the coating include component A and component B, wherein:

[0006] The component A comprises the following components in parts by weight:

[0007]

[0008] The B component includes the following components in parts by weight:

[0009] 3-6 parts of tetraalkoxysilane

[0010] 3-6 parts of polysilazane

[0011] Dibutyltin dilaurate 0.6~1 part

[0012] The density of large-sized low-density hollow microspheres is 0.10-0.15 g / cm 3 , average particle size ≧50μm;

[0013] The density of medium-sized medium-density hollow microspheres is 0.2-0.3 g / cm 3 , the average particle size is 20-50 μm;

[0014] Small size high density hollow microspheres with a density of 0.3-0.4 g / cm 3 , the average particle size is ≦20μm.

[0015] In the above-mentioned large thickness ultra-low density high toughness silicone rubber heat-resistant coating, the preparation method of the purified methyl diphenyl silicone rubber comprises:

[0016] Octamethylcyclotetrasiloxane D4 and octaphenylcyclotetrasiloxane D4 were mixed in a molar ratio of 100:5-15. Ph Add into the reaction kettle, and polymerize at 160-180°C for 6-12h to prepare dimethyl diphenyl mixed cyclosiloxane;

[0017] Raising the temperature to 240-260° C., adding 0.1-0.2% of ammonium hydroxide by total mass fraction, and reacting for 20-24 hours to prepare a crude methylbisphenyl silicone rubber product;

[0018] The methyl bisphenyl silicone rubber resin was prepared by vacuum distillation at 100-120°C for 6-8h;

[0019] The scraper distillation method was used to purify methyl bisphenyl silicone rubber. The flow rate of silicone rubber was set to 0.05-0.1 mL / s, the distance between the condenser plate and the liquid surface was set to 5-10 mm, and several scraper distillation temperatures were set. After distillation for 3-5 times at each temperature, purified methyl bisphenyl silicone rubber was prepared.

[0020] In the above-mentioned large-thickness ultra-low-density high-toughness silicone rubber heat-resistant coating, five scraper distillation temperatures are set, which are 150°C, 180°C, 210°C, 240°C and 270°C respectively.

[0021] In the above-mentioned thick ultra-low density high-toughness silicone rubber heat-resistant coating, the hollow microspheres are surface-modified, and the surface modification method includes:

[0022] (1) Mix alkoxysilane, anhydrous ethanol and deionized water in a volume ratio of 1:38-42:9-11;

[0023] (2) The mixed solution is fully mixed and hydrolyzed at 58-62° C. for 0.5-1 h to obtain a hydrolyzed solution;

[0024] (3) adding the hollow microspheres to the hydrolysis solution in a ratio of 1020 mL of the mixed solution to 150-200 g of the hollow microspheres, stirring at 78-82° C. for 0.5-1 h to obtain a hydroxyl-modified hollow microsphere suspension;

[0025] (4) Filter the suspension and wash it with deionized water to obtain modified hollow microspheres.

[0026] In the above-mentioned large-thickness, ultra-low-density and high-toughness silicone rubber heat-resistant coating, the alkoxysilane is tetraethoxysilane.

[0027] In the above-mentioned large-thickness, ultra-low-density, high-toughness silicone rubber heat-resistant coating, the reinforcing filler is fumed silica; the high-temperature resistant and antioxidant filler is one or more of iron oxide, cerium oxide, magnesium oxide, aluminum oxide or zirconium oxide; the average particle size of the cork powder is less than 80 mesh; the diluent is one or two of No. 120 solvent gasoline, xylene, ethyl acetate or butyl acetate.

[0028] In the above-mentioned thick ultra-low density high-toughness silicone rubber heat-resistant coating, the tetraalkoxysilane is tetraethoxysilane or n-propoxysilane; the viscosity of the polysilazane is 1000-1500cps.

[0029] In the above-mentioned large-thickness ultra-low-density high-toughness silicone rubber heat-resistant coating, the coating thickness is up to 15 mm, and the coating density is 0.24-0.28 g / cm 3 .

[0030] The preparation method of the above-mentioned large-thickness ultra-low-density high-toughness silicone rubber heat-resistant coating comprises:

[0031] (1) Mixing purified methyl diphenyl silicone rubber with reinforcing filler, cork powder, high temperature resistant antioxidant filler, and glass fiber according to a ratio, and dispersing them using a three-roll mill to obtain a reinforced mixture;

[0032] (2) mixing the reinforcing mixture, hollow microspheres and diluent according to a proportion, and dispersing them using a high-speed disperser to obtain a coating component A mixture;

[0033] (3) Mix components A and B of the coating, add a diluent to adjust the coating viscosity to 15-25s, and apply to the required thickness to obtain a thick, ultra-low-density, high-toughness silicone rubber heat-resistant coating.

[0034] In the above-mentioned method for preparing a thick ultra-low density high-toughness silicone rubber heat-resistant coating, the coating method in step (3) includes spraying, brushing or scraping, and the coating thickness is up to 15 mm and the density is 0.24-0.28 g / cm 3 .

[0035] The above-mentioned large-thickness, ultra-low-density, high-toughness silicone rubber thermal protection coating is applied to the outer surface of the planetary probe back cover structure.

[0036] Compared with the prior art, the present invention has at least the following beneficial effects:

[0037] (1) In the embodiment of the present invention, the coating formula is optimized and designed, and a specific ratio of purified methyl diphenyl silicone rubber and hollow microspheres of large, medium and small densities, reinforcing fillers, cork powder, high temperature resistant and antioxidant fillers, glass fiber, tetraalkoxysilane, polysilazane, etc. are used to prepare a silicone rubber heat-resistant coating with high lightness, good toughness, large thickness spraying, good ablation resistance, and has passed the CO2 atmosphere with a maximum heat flux density of 90KW / m 2 Quartz lamp and wind tunnel ablation test assessment.

[0038] (2) The ultra-low density and high toughness silicone rubber heat-resistant coating of the embodiment of the present invention has low density and better toughness, and the density is as low as 0.24-0.28 g / cm 3 , while the elongation at break is as high as 15% to 25%, and can be sprayed in large thickness;

[0039] (3) The ultra-low density and high toughness silicone rubber heat-resistant coating of the embodiment of the present invention has good heat-resistant performance and the maximum heat flux density through CO2 atmosphere is 90KW / m 2 Quartz lamp and wind tunnel ablation test assessment;

[0040] (4) The ultra-low density and high toughness silicone rubber heat-resistant coating of the embodiment of the present invention uses siloxane and polysilazane as a curing agent and has good adhesion to the substrate;

[0041] (5) The ultra-low density and high toughness silicone rubber heat-resistant coating of the present invention has good environmental adaptability and does not crack after a total of 100 cycles of liquid nitrogen / 150°C. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] Figure 1 This is the appearance of the ultra-low density and high toughness silicone rubber heat-resistant coating in Example 1 of the present invention after 100 cycles of liquid nitrogen / 150°C;

[0043] Figure 2 This is a scanning electron microscope photo of the ultra-low density and high toughness silicone rubber heat-resistant coating in Example 1 of the present invention;

[0044] Figure 3 This is a photo of the ultra-low density and high toughness silicone rubber heat-resistant coating after the wind tunnel test in Example 1 of the present invention;

[0045] Figure 4 This is a photo of the ultra-low density and high toughness silicone rubber heat-resistant coating quartz lamp after the test in Example 1 of the present invention. DETAILED DESCRIPTION

[0046] The present invention is further described in detail below with reference to the accompanying drawings and specific embodiments:

[0047] The raw materials of the room temperature curing large thickness ultra-low density high toughness silicone rubber heat-resistant coating of the present invention include component A and component B, wherein component A includes the following components in parts by weight:

[0048]

[0049] Component B includes the following components by mass:

[0050] 3-6 parts of tetraalkoxysilane

[0051] 3-6 parts of polysilazane

[0052] Dibutyltin dilaurate 0.6~1 part

[0053] In an optional embodiment, the preparation method of purified methyl bisphenyl silicone rubber is as follows:

[0054] Octamethylcyclotetrasiloxane (D4) and octaphenylcyclotetrasiloxane (D4) were first mixed in a molar ratio of 100:5-15. Ph ) is added into a reactor, and a polymerization reaction is carried out at 160-180°C for 6-12h to prepare dimethyldiphenyl mixed cyclosiloxane; the temperature is increased to 240-260°C, and ammonium hydroxide with a total mass fraction of 0.1-0.2% is added, and the reaction is carried out for 20-24h to prepare a crude methyl diphenyl silicone rubber product; vacuum distillation is carried out at 100-120°C for 6-8h to prepare a methyl diphenyl silicone rubber resin; the methyl diphenyl silicone rubber is purified by scraper distillation, the silicone rubber flow rate is set to 0.05-0.1mL / s, the distance between the condensation plate and the liquid surface is 5-10mm, and the scraper distillation temperatures are preferably set to 150°C, 180°C, 210°C, 240°C and 270°C, respectively, and purified methyl diphenyl silicone rubber is prepared after distillation at the five temperatures for 3-5 times.

[0055] In an optional embodiment, the reinforcing filler is fumed silica.

[0056] In an optional embodiment, the density of the large-sized low-density hollow microspheres is 0.10-0.15 g / cm 3 , average particle size ≧50μm; medium-sized medium-density hollow microspheres with a density of 0.2-0.3g / cm 3 The average particle size is 20-50 μm; the density of small-sized high-density hollow microspheres is 0.3-0.4 g / cm 3 The average particle size is ≦20μm; the mass ratio of large-sized low-density hollow microspheres to medium-sized medium-density hollow microspheres is 1:1 to 2:1.

[0057] In an optional embodiment, the hollow microspheres used have better effects after surface modification, and the modification method includes:

[0058] (1) Alkoxysilane, anhydrous ethanol and deionized water are uniformly mixed in a volume ratio of 1:38-42:9-11, wherein the alkoxysilane is preferably tetraethoxysilane.

[0059] (2) The mixed solution is fully mixed and hydrolyzed at 60°C ± 2 for 0.5 to 1 h to obtain a hydrolyzed solution;

[0060] (3) Weighing 150-200 g of hollow microspheres, adding them to the hydrolysis solution, stirring at 80±2° C. for 0.5-1 h, and obtaining a hydroxyl-modified hollow microsphere suspension;

[0061] (4) Filter the suspension and wash it with deionized water to obtain modified hollow microspheres.

[0062] In an optional embodiment, the average particle size of the cork powder is less than 80 mesh.

[0063] In an optional embodiment, the high temperature resistant and oxidation resistant filler is preferably one or more of iron oxide, cerium oxide, magnesium oxide, aluminum oxide, and zirconium oxide.

[0064] In an optional embodiment, the diluent is preferably one or two of No. 120 solvent gasoline, xylene, ethyl acetate or butyl acetate.

[0065] In an optional embodiment, the tetraalkoxysilane is preferably tetraethoxysilane or n-propoxysilane, and the viscosity of the polysilazane in component B is preferably 1000-1500 cps.

[0066] The method for preparing the coating of the ultra-low density high-toughness silicone rubber heat-resistant coating in the embodiment of the present invention is as follows:

[0067] (1) mixing purified methyl diphenyl silicone rubber with reinforcing filler, cork powder, high temperature resistant antioxidant filler, and glass fiber according to a ratio, and dispersing them using a three-roll mill to obtain a reinforced mixture;

[0068] (2) mixing the reinforcement mixture, hollow microspheres or modified hollow microspheres, and a diluent according to a ratio, and dispersing them using a high-speed disperser to obtain a coating component A mixture;

[0069] (3) Mix components A and B of the coating, add a diluent to adjust the coating viscosity to 15-25s, and apply to a specified thickness to obtain an ultra-low density and high-toughness silicone rubber heat-resistant coating.

[0070] The coating methods include spraying, brushing or scraping, with a maximum coating thickness of 15 mm and a density of 0.24 to 0.28 g / cm3 After the coating is applied to the surface of steel, aluminum, and carbon epoxy substrates, it can be placed in liquid nitrogen for not less than 5 minutes, and then placed at 150°C for not less than 5 minutes, for a total of 100 cycles without cracking.

[0071] In the embodiment of the present invention, the ultra-low density and high-toughness silicone rubber heat-resistant coating is applied to the outer surface of the back cover structure of the planetary probe.

[0072] Example 1

[0073] In the first step, 2960 g (10 mol) of octamethylcyclotetrasiloxane (D4) and 645 g (0.8 mol) of octaphenylcyclotetrasiloxane (D4) were mixed. Ph ) was added into a reactor, and polymerization reaction was carried out at 165°C for 8 hours to prepare dimethyldiphenyl mixed cyclosiloxane; the temperature was increased to 240°C, 4 g of ammonium hydroxide was added, and the reaction was carried out for 24 hours to prepare a crude methyl diphenyl silicone rubber product; vacuum distillation was carried out at 120°C for 8 hours to prepare a methyl diphenyl silicone rubber resin; the methyl diphenyl silicone rubber was purified by scraper distillation, the silicone rubber flow rate was set to 0.05 mL / s, the distance between the condenser plate and the liquid surface was set to 5 mm, the scraper distillation temperatures were set to 150°C, 180°C, 210°C, 240°C and 270°C, respectively, and distillation was performed 5 times at five temperatures to prepare purified methyl diphenyl silicone rubber.

[0074] In the second step, 40 mL of tetraethyl orthosilicate was added to a mixed solution of 1600 mL of anhydrous ethanol and 400 mL of deionized water; the mixed solution was fully mixed and hydrolyzed at 60°C for 0.5 h to obtain a hydrolyzed solution; 400 g of a density of 0.13 g / cm 3 The hollow microspheres are added into the hydrolysis solution and stirred at 80° C. for 0.5 h to obtain a hydroxyl-modified hollow microsphere suspension; the suspension is filtered and cleaned with deionized water to obtain modified hollow microspheres.

[0075] In the third step, 1 kg of purified methyl diphenyl silicone rubber was mixed with 300 g of fumed silica, 100 g of cork powder, 15 g of iron oxide, and 30 g of glass fiber, and dispersed and ground four times using a three-roll grinder to obtain a reinforced mixture; 350 g of the modified 0.13 g / cm 3 Hollow microspheres, 250g, density 0.22g / cm 3 Hollow microspheres, 50g density 0.38g / cm 3 The hollow microspheres were added with 1 kg of No. 120 solvent gasoline and dispersed using a high-speed disperser to obtain a coating component A mixture;

[0076] 50 g of tetraethoxysilane, 50 g of methylvinylpolysilazane with a viscosity of 1000 cps, and 1 g of dibutyltin dilaurate were mixed evenly to obtain a coating component B mixture;

[0077] The fourth step is to mix the coating components A and B, add No. 120 solvent gasoline to adjust the coating viscosity to 18s, spray the coating on the substrate to 9mm, and cure at room temperature for 3d to obtain a cured ultra-low density and high-toughness silicone rubber heat-resistant coating.

[0078] The performance parameters of the ultra-low density thermal protection coating are shown in Table 1 below.

[0079] like Figure 1 The figure shows the appearance of the ultra-low density and high toughness silicone rubber heat-resistant coating in Example 1 after 100 cycles of liquid nitrogen / 150°C; Figure 2 This is a scanning electron microscope photo of the ultra-low density and high toughness silicone rubber heat-resistant coating in Example 1; Figure 3 This is a photo of the ultra-low density and high toughness silicone rubber heat-resistant coating after the wind tunnel test in Example 1; Figure 4 This is a photo of the ultra-low density and high toughness silicone rubber heat-resistant coating after the quartz lamp test in Example 1. As can be seen from the figure, the ultra-low density coating prepared according to the present invention has good high and low temperature toughness, can withstand temperature changes during space flight without cracking; at the same time, it can be used for landing spacecraft on the surface of a planet with a CO2 atmosphere, and plays an effective heat-resistant role. At the same time, the coating material has low density, good processability and low cost.

[0080] Example 2

[0081] In the first step, 2960 g (10 mol) of octamethylcyclotetrasiloxane (D4) and 397 g (0.5 mol) of octaphenylcyclotetrasiloxane (D4) were mixed. Ph ) was added into a reactor, and polymerization reaction was carried out at 180°C for 6 hours to prepare dimethyldiphenyl mixed cyclosiloxane; the temperature was increased to 250°C, 4.5g of ammonium hydroxide was added, and the reaction was carried out for 24 hours to prepare a crude methyldiphenyl silicone rubber product; vacuum distillation was carried out at 100°C for 8 hours to prepare a methyldiphenyl silicone rubber resin; the methyldiphenyl silicone rubber was purified by scraper distillation, the silicone rubber flow rate was set to 0.1mL / s, the distance between the condenser plate and the liquid surface was set to 10mm, the scraper distillation temperatures were set to 150°C, 180°C, 210°C, 240°C and 270°C, respectively, and purified methyldiphenyl silicone rubber was prepared after distillation 3 times at five temperatures.

[0082] In the second step, 60 mL of tetraethyl orthosilicate was added to a mixed solution of 2400 mL of anhydrous ethanol and 600 mL of deionized water; the mixed solution was fully mixed and hydrolyzed at 60°C for 0.5 h to obtain a hydrolyzed solution; 450 g of a solution with a density of 0.23 g / cm 3The hollow microspheres are added into the hydrolysis solution and stirred at 80° C. for 0.5 h to obtain a hydroxyl-modified hollow microsphere suspension; the suspension is filtered and cleaned with deionized water to obtain modified hollow microspheres.

[0083] The third step is to mix 1 kg of purified methyl diphenyl silicone rubber with 100 g of fumed silica, 50 g of cork powder, 10 g of iron oxide, and 20 g of glass fiber, and grind them three times using a three-roll grinder to obtain a reinforced mixture; add 450 g of a 0.13 g / cm 3 Hollow microspheres, 200g modified density 0.23g / cm 3 The hollow microspheres were added with 0.6 kg of No. 120 solvent gasoline and 0.6 kg of ethyl acetate, and dispersed using a high-speed disperser to obtain a coating component A mixture;

[0084] 50 g of tetraethoxysilane, 50 g of methylvinylpolysilazane with a viscosity of 1500 cps, and 0.8 g of dibutyltin dilaurate were mixed evenly to obtain a coating component B mixture;

[0085] The fourth step is to mix the coating components A and B, add No. 120 solvent gasoline to adjust the coating viscosity to 25s, spray the coating on the substrate to 15mm, and cure at room temperature for 3 days to obtain a cured ultra-low density and high-toughness silicone rubber heat-resistant coating.

[0086] The performance parameters of the ultra-low density thermal protection coating are shown in Table 1 below.

[0087] Example 3

[0088] In the first step, 2960 g (10 mol) of octamethylcyclotetrasiloxane (D4) and 1190 g (1.5 mol) of octaphenylcyclotetrasiloxane (D4) were mixed. Ph ) was added into a reactor, and polymerization reaction was carried out at 160°C for 12 hours to prepare dimethyldiphenyl mixed cyclosiloxane; the temperature was increased to 260°C, 6 g of ammonium hydroxide was added, and the reaction was carried out for 24 hours to prepare a crude methyldiphenyl silicone rubber product; vacuum distillation was carried out at 120°C for 6 hours to prepare a methyldiphenyl silicone rubber resin; the methyldiphenyl silicone rubber was purified by scraper distillation, the silicone rubber flow rate was set to 0.08 mL / s, the distance between the condenser plate and the liquid surface was 5 mm, the scraper distillation temperatures were set to 150°C, 180°C, 210°C, 240°C and 270°C, respectively, and purified methyldiphenyl silicone rubber was prepared after distillation 4 times at five temperatures.

[0089] In the second step, 40 mL of tetraethyl orthosilicate was added to a mixed solution of 1600 mL of anhydrous ethanol and 400 mL of deionized water; the mixed solution was fully mixed and hydrolyzed at 60°C for 0.5 h to obtain a hydrolyzed solution; 400 g of a density of 0.13 g / cm 3 The hollow microspheres were added into the hydrolysis solution and stirred at 80 °C for 0.5 h to obtain a hydroxyl-modified hollow microsphere suspension; the suspension was filtered and cleaned with deionized water to obtain a modified density of 0.13 g / cm 3 Hollow microspheres;

[0090] 40 mL of tetraethyl orthosilicate was added to a mixed solution of 1600 mL of anhydrous ethanol and 400 mL of deionized water; the mixed solution was fully mixed and hydrolyzed at 60°C for 0.5 h to obtain a hydrolyzed solution; 350 g of a solution with a density of 0.20 g / cm 3 The hollow microspheres were added into the hydrolysis solution and stirred at 80 °C for 0.5 h to obtain a hydroxyl-modified hollow microsphere suspension; the suspension was filtered and cleaned with deionized water to obtain a modified density of 0.23 g / cm 3 Hollow microspheres;

[0091] In the third step, 1 kg of purified methyl diphenyl silicone rubber was mixed with 350 g of fumed silica, 80 g of cork powder, 12 g of iron oxide, and 50 g of glass fiber, and dispersed and ground five times using a three-roll grinder to obtain a reinforced mixture; 400 g of the modified 0.13 g / cm 3 Hollow microspheres, 300g modified density 0.20g / cm 3 Hollow microspheres, 10g density 0.4g / cm 3 The hollow microspheres were added with 0.8 kg of No. 120 solvent gasoline and 0.3 kg of butyl acetate, and dispersed using a high-speed disperser to obtain a coating component A mixture;

[0092] 50 g of tetraethoxysilane, 50 g of methylvinylpolysilazane with a viscosity of 1000 cps, and 1 g of dibutyltin dilaurate were mixed evenly to obtain a coating component B mixture;

[0093] The fourth step is to mix the coating components A and B, add No. 120 solvent gasoline to adjust the coating viscosity to 20s, spray the coating on the substrate to 7mm, and cure at room temperature for 3d to obtain a cured ultra-low density and high-toughness silicone rubber heat-resistant coating.

[0094] The performance parameters of the ultra-low density thermal protection coating are shown in Table 1 below.

[0095] Table 1 Performance parameters of ultra-low density heat-resistant coating for space use in different embodiments

[0096]

[0097]

[0098] The above description is only the best specific implementation mode of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by any technician familiar with the technical field within the technical scope disclosed by the present invention should be covered within the protection scope of the present invention.

[0099] The contents not described in detail in the specification of the present invention belong to the common knowledge of the professionals in this field.

Claims

1. A thick, ultra-low-density, high-toughness silicone rubber heat-resistant coating, characterized in that: The raw materials of the coating include component A and component B, wherein: The component A comprises the following components in parts by weight: The B component includes the following components in parts by weight: 3-6 parts of tetraalkoxysilane 3-6 parts of polysilazane Dibutyltin dilaurate 0.6~1 part The density of large-sized low-density hollow microspheres is 0.10-0.15 g / cm 3 , average particle size ≧50μm; The density of medium-sized medium-density hollow microspheres is 0.2-0.3 g / cm 3 , the average particle size is 20 to 50 μm; Small size high density hollow microspheres with a density of 0.3-0.4 g / cm 3 , the average particle size is ≦20μm.

2. The thick ultra-low density high-toughness silicone rubber heat-resistant coating according to claim 1 is characterized in that: The preparation method of the purified methyl diphenyl silicone rubber comprises: Octamethylcyclotetrasiloxane D4 and octaphenylcyclotetrasiloxane D4 were mixed in a molar ratio of 100:5-15. Ph Add into the reaction kettle, and polymerize at 160-180°C for 6-12h to prepare dimethyl diphenyl mixed cyclosiloxane; Raising the temperature to 240-260° C., adding 0.1-0.2% of ammonium hydroxide by total mass fraction, and reacting for 20-24 hours to prepare a crude methylbisphenyl silicone rubber product; The methyl bisphenyl silicone rubber resin was prepared by vacuum distillation at 100-120°C for 6-8h; The scraper distillation method was used to purify methyl bisphenyl silicone rubber. The flow rate of silicone rubber was set to 0.05-0.1 mL / s, the distance between the condenser plate and the liquid surface was set to 5-10 mm, and several scraper distillation temperatures were set. After distillation for 3-5 times at each temperature, purified methyl bisphenyl silicone rubber was prepared.

3. The thick ultra-low density high-toughness silicone rubber heat-resistant coating according to claim 2 is characterized in that: Five scraper distillation temperatures were set, namely 150°C, 180°C, 210°C, 240°C and 270°C.

4. The thick ultra-low density high-toughness silicone rubber heat-resistant coating according to claim 1 is characterized in that: The hollow microspheres are surface modified, and the surface modification method includes: (1) Mix alkoxysilane, anhydrous ethanol and deionized water in a volume ratio of 1:38-42:9-11; (2) The mixed solution is fully mixed and hydrolyzed at 58-62° C. for 0.5-1 h to obtain a hydrolyzed solution; (3) adding the hollow microspheres to the hydrolysis solution in a ratio of 1020 mL of the mixed solution to 150-200 g of the hollow microspheres, stirring at 78-82° C. for 0.5-1 h to obtain a hydroxyl-modified hollow microsphere suspension; (4) Filter the suspension and wash it with deionized water to obtain modified hollow microspheres.

5. The thick ultra-low density high-toughness silicone rubber heat-resistant coating according to claim 4 is characterized in that: The alkoxysilane is tetraethoxysilane.

6. The thick ultra-low density high-toughness silicone rubber heat-resistant coating according to claim 1, characterized in that: The reinforcing filler is fumed silica; The high temperature resistant and anti-oxidation filler is one or more of iron oxide, cerium oxide, magnesium oxide, aluminum oxide or zirconium oxide; The average particle size of the cork powder is less than 80 mesh; The diluent is one or two of No. 120 solvent gasoline, xylene, ethyl acetate or butyl acetate.

7. The thick ultra-low density high-toughness silicone rubber heat-resistant coating according to claim 1, characterized in that: The tetraalkoxysilane is tetraethoxysilane or n-propoxysilane; The viscosity of the polysilazane is 1000-1500 cps.

8. The thick ultra-low density high-toughness silicone rubber heat-resistant coating according to claim 1, characterized in that: The coating thickness is up to 15 mm and the coating density is 0.24-0.28 g / cm 3 .

9. The method for preparing the thick ultra-low density high-toughness silicone rubber heat-resistant coating according to any one of claims 1 to 8, characterized in that: include: (1) Mixing the purified methyl diphenyl silicone rubber with reinforcing filler, cork powder, high temperature resistant antioxidant filler, and glass fiber according to a ratio, and dispersing them using a three-roll mill to obtain a reinforced mixture; (2) mixing the reinforcing mixture, hollow microspheres and diluent according to a proportion, and dispersing them using a high-speed disperser to obtain a coating component A mixture; (3) Mix components A and B of the coating, add a diluent to adjust the coating viscosity to 15-25s, and apply to the required thickness to obtain a thick, ultra-low-density, high-toughness silicone rubber heat-resistant coating.

10. The method for preparing the thick ultra-low density high-toughness silicone rubber heat-resistant coating according to claim 9, characterized in that: The coating method in step (3) includes spraying, brushing or scraping, and the coating thickness is up to 15 mm and the density is 0.24-0.28 g / cm 3 .

11. Application of the thick, ultra-low-density, high-toughness silicone rubber heat-resistant coating according to any one of claims 1 to 8 to the outer surface of the back cover structure of a planetary probe.

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