A functional topcoat for maintaining the aerodynamic shape of a ceramic heat shield and a method of making the same

Abstract

The application belongs to the technical field of special coating materials, and particularly relates to a functional finish for maintaining the aerodynamic shape of a ceramicized heat-resistant coating and a preparation method thereof. The functional finish comprises component A and component B. The component A comprises 75-80% of a base and 20-25% of a pigment based on the total weight of the component A. The base comprises 50-60 parts of organic silicon resin, 5-10 parts of a reinforcing agent and 3-5 parts of a matting agent. The component B comprises a cross-linking agent and a catalyst in a mass ratio of 10:1. The functional finish has the characteristics of easily forming uniform micro-cracks in a high-temperature flight environment. The finish cracks extend to the surface of the heat-resistant coating, so that the surface of the heat-resistant coating forms uniform micro-cracks. Therefore, the gas generated by pyrolysis in the coating can be released through the cracks, and the phenomenon that the ceramicized ablation surface layer is separated from the original layer due to poor emission of pyrolysis gas is avoided.

Description

Technical Field

[0001] This invention belongs to the field of special coating materials technology, specifically relating to a functional topcoat that maintains the aerodynamic shape of a ceramicized heat-resistant coating and its preparation method. Background Technology

[0002] With the development of aerospace technology, the thermal environment of spacecraft is becoming increasingly demanding, and thermal protection materials are constantly evolving. To meet the increasingly stringent thermal requirements of spacecraft, the base material for the thermal protection coating of rocket engine combustion chamber shells is gradually shifting from silicone rubber systems to silicone resin systems. This is because silicone rubber undergoes cyclization degradation at high temperatures, forming powdered silica. This powdered silica is then lost to the environment under airflow, meaning that topcoats using silicone rubber as the base material do not provide any auxiliary effect to the thermal protection function of the thermal protection coating.

[0003] However, it is also important to note that the silicone resin coating will pyrolyze and generate gas under high temperature conditions. The dense ceramicized ablation surface layer is not conducive to the emission of gas inside the coating, which leads to the phenomenon that the ceramicized ablation surface layer separates from the original layer under the action of internal gas, which damages the aerodynamic shape of the aircraft and affects the flight accuracy of the aircraft.

[0004] Based on this, the technical solution of the present invention is proposed. Summary of the Invention

[0005] To address the problems existing in the prior art, the present invention provides a functional topcoat that maintains the aerodynamic shape of a ceramicized heat-resistant coating, characterized in that it comprises component A and component B; wherein:

[0006] Component A comprises a base material accounting for 75-80% of the total weight of Component A and a pigment accounting for 20-25% of the total weight of Component A; the base material comprises the following raw materials in parts by weight: 50-60 parts of silicone resin, 5-10 parts of reinforcing agent and 3-5 parts of matting agent;

[0007] Component B includes a crosslinking agent and a catalyst in a mass ratio of (8-10):(1-2).

[0008] Preferably, the weight ratio of component A to component B is (91-99):(9-1).

[0009] Preferably, the silicone resin is a room temperature curing condensation type silicone resin or a room temperature curing addition type silicone resin, specifically: one or more of methyl silicone resin, methyl phenyl silicone resin, vinyl silicone resin, and phenylene silicone resin.

[0010] The viscosity of the organosilicon resin is 0.5 to 50 Pa·s; more preferably 10 Pa·s.

[0011] Preferably, the reinforcing agent is one or a combination of two or more of carbon black, silica, kaolin, and calcium carbonate; more preferably, the reinforcing agent is a mixture of fumed silica and precipitated silica; even more preferably, it is a mixture of fumed silica and precipitated silica in a mass ratio of 1.5 to 2.2:1.

[0012] And / or, the matting agent is one of pure polyester matting resin RB608, pure polyester matting agent RB3329, or an organic matting agent.

[0013] Preferably, the base material further includes the following raw materials in parts by weight: 30-40 parts of filler and / or 0.5-1 part of antifungal agent.

[0014] Preferably, the filler is one of the following: kaolin, diatomaceous earth, talc, graphite, calcium carbonate, alumina powder, glass powder, asbestos powder, mica powder, quartz powder, carbon fiber, powdered cork, and corundum.

[0015] And / or, the antifungal agent is one of phenols, chlorophenols, organic mercury salts, organic copper salts, organic tin salts, copper sulfate, mercuric chloride, and sodium fluoride.

[0016] Preferably, the crosslinking agent is one of polyethylene silicate, tetraethyl orthosilicate, and propyl orthosilicate.

[0017] Preferably, the catalyst is one of organotin catalysts, inorganic tin catalysts, and chloroplatinic acid;

[0018] The organotin catalyst is one of butyltin, octyltin, dibutyltin, and dimethyltin.

[0019] The inorganic tin catalyst is one of stannous chloride, stannous tetrachloride, and stannous oxide.

[0020] Based on the same technical concept, another aspect of the present invention is to provide a method for preparing a functional topcoat that maintains the aerodynamic shape of a ceramicized heat-resistant coating, the preparation method comprising the following steps:

[0021] (1) Mix all the raw materials of the base material, then add pigment and diluent (organic solvent, such as petroleum ether, etc.), stir evenly to obtain component A;

[0022] (2) Mix the crosslinking agent and catalyst evenly to obtain component B;

[0023] (3) Mix components A and B, stir and disperse them, spray evenly onto the surface of the substrate, and cure.

[0024] The beneficial effects of this invention are as follows:

[0025] The functional topcoat that maintains the aerodynamic shape of the ceramicized heat-resistant coating described in this invention has the characteristic of easily forming uniform microcracks in high-temperature flight environments. The cracks in the topcoat extend to the surface of the heat-resistant coating, forming uniform microcracks on the surface of the heat-resistant coating. This allows the gas generated inside the coating due to high-temperature pyrolysis to be released through the cracks, avoiding the separation of the ceramicized ablation surface layer from the original layer caused by poor pyrolysis gas emission.

[0026] Meanwhile, the color of the functional topcoat can be controlled by the added pigments.

[0027] In addition, the functional topcoat uses silicone resin as a base material and adds antifungal agents, thus having waterproof, antifungal, and dustproof effects.

[0028] The preparation method described in this invention is simple, easy to control, convenient to implement, and has good repeatability. Attached Figure Description

[0029] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0030] Figure 1 This is a diagram showing the sample preparation results of Example 1 after the electric arc wind tunnel test.

[0031] Figure 2 This is a diagram showing the sample preparation results of Comparative Example 1 after the electric arc wind tunnel test.

[0032] Figure 3 This is a diagram showing the sample preparation results of Comparative Example 3 after the electric arc wind tunnel test. Detailed Implementation

[0033] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be described in detail below. Obviously, the described embodiments are merely some embodiments of this invention, and not all embodiments. Based on the embodiments of this invention, all other implementation methods obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0034] In this embodiment, "part" refers to "unit weight," such as "100 parts" meaning "100 unit weights." The specific "unit weight" is determined by those skilled in the art based on the specific circumstances: for small-scale trials, each "unit weight" can be 1g; for pilot-scale trials, each "unit weight" can be 1kg.

[0035] Example 1

[0036] This embodiment provides a method for preparing a functional topcoat that maintains the aerodynamic shape of a ceramicized heat-resistant coating, comprising the following steps:

[0037] (1) First, add methyl silicone resin, fumed silica, precipitated silica and antifungal agent (copper sulfate) to the mixing tank in sequence, stir with a stirrer for 15 minutes to make the materials fully mixed and uniform, and obtain the first mixture. Then, pour the first mixture into a three-roll mill for grinding. During the grinding process, add calcium carbonate and matting powder (pure polyester matting resin RB608) to obtain the second mixture. Finally, pour the second mixture into the mixing tank, add white pigment, and add diluent (petroleum ether) and mix evenly. Seal and package for later use to obtain component A.

[0038] (2) Weigh the crosslinking agent and catalyst, mix them evenly, seal them in a package for later use, and obtain component B;

[0039] (3) Mix component A and component B according to the ratio and stir and disperse for 10 minutes. Spray evenly on the coating and cure.

[0040] The proportions of each raw material are shown in Table 1.

[0041] Table 1

[0042]

[0043] Example 2

[0044] This embodiment provides a method for preparing a functional topcoat that maintains the aerodynamic shape of a ceramicized heat-resistant coating, comprising the following steps:

[0045] (1) First, add methyl silicone resin, fumed silica, precipitated silica and antifungal agent (copper sulfate) to the mixing tank in sequence, stir with a stirrer for 15 minutes to make the materials fully mixed and uniform, and obtain the first mixture. Then, pour the first mixture into a three-roll mill for grinding. During the grinding process, add calcium carbonate and matting powder (pure polyester matting resin RB608) to obtain the second mixture. Finally, pour the second mixture into the mixing tank, add white pigment and green color paste, and add diluent (petroleum ether) and mix evenly. Seal and package for later use to obtain component A.

[0046] (2) Weigh the crosslinking agent and catalyst, mix them evenly, seal them in a package for later use, and obtain component B;

[0047] (3) Mix component A and component B according to the ratio and stir and disperse for 10 minutes. Spray evenly on the coating and cure.

[0048] The proportions of each raw material are shown in Table 2.

[0049] Table 2

[0050]

[0051] Comparative Example 1

[0052] This comparative example does not use topcoat.

[0053] Comparative Example 2

[0054] This comparative example provides a method for preparing a functional topcoat that maintains the aerodynamic shape of the ceramicized heat-resistant coating, comprising the following steps:

[0055] (1) First, add methyl silicone rubber, fumed silica, precipitated silica and antifungal agent (copper sulfate) to the mixing tank in sequence, stir with a stirrer for 15 minutes to make the materials fully mixed and uniform, and obtain the first mixture. Then, pour the first mixture into a three-roll mill for grinding. During the grinding process, add calcium carbonate and matting powder (pure polyester matting resin RB608) to obtain the second mixture. Finally, pour the second mixture into the mixing tank, add white pigment, and add diluent (petroleum ether) and mix evenly. Seal and package for later use to obtain component A.

[0056] (2) Weigh the crosslinking agent and catalyst, mix them evenly, seal them in a package for later use, and obtain component B;

[0057] (3) Mix component A and component B according to the ratio and stir and disperse for 10 minutes. Spray evenly on the coating and cure.

[0058] The proportions of each raw material are shown in Table 3.

[0059] Table 3

[0060]

[0061] Verification Comparison

[0062] The sample preparation results of Examples 1-2 and Comparative Examples 1-2 are compared, as shown in Table 4.

[0063] Table 4

[0064]

[0065] More specifically:

[0066] In Example 1, the functional topcoat provided by the present invention has the characteristic of easily forming uniform microcracks in a high-temperature flight environment. The topcoat cracks extend to the surface of the heat-resistant coating, so that uniform microcracks are formed on the surface of the heat-resistant coating. This allows the gas generated inside the coating due to high-temperature pyrolysis to be released through the cracks, avoiding the separation of the ceramicized ablation surface layer from the original layer caused by poor pyrolysis gas emission. This effectively maintains the aerodynamic shape of the aircraft.

[0067] In Example 2, green pigment was added to obtain a green sample without affecting the ablation performance of the material. The color of the functional topcoat provided by the present invention can be controlled by the added pigment.

[0068] In Comparative Example 1, without the use of topcoat, the dense ceramicized ablation surface layer hindered the emission of pyrolysis gases inside the coating during the arc wind tunnel test. Under the pressure of the internal pyrolysis gases, the ceramicized ablation surface layer separated from the original layer, resulting in the peeling off of the ceramicized ablation surface layer, which damaged the aerodynamic shape and heat protection structure of the aircraft.

[0069] In Comparative Example 2, a traditional silicone rubber system topcoat was used. During the arc wind tunnel test, the topcoat degraded at high temperatures to form powdery silica and other products, which were washed away by the airflow. The topcoat with silicone rubber as the base material did not have an auxiliary effect on the thermal protection function of the heat-resistant coating. In the end, the ceramicized ablation surface layer separated from the original layer.

[0070] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A functional topcoat that maintains the aerodynamic shape of a ceramicized heat-resistant coating, characterized in that, The product comprises component A and component B, wherein the weight ratio of component A to component B is (91~99):(9~1); wherein: Component A comprises a base material accounting for 75-80% of the total weight of Component A and a pigment accounting for 20-25% of the total weight of Component A; the base material comprises the following raw materials in parts by weight: 50-60 parts of silicone resin, 5-10 parts of reinforcing agent and 3-5 parts of matting agent; The organosilicon resin is one or a combination of two or more of methyl silicone resin, methyl phenyl silicone resin, vinyl silicone resin, and phenylene silicone resin; the viscosity of the organosilicon resin is 0.5~50 Pa·s; The reinforcing agent is one or a combination of two or more of carbon black, silica, and clay. The matting agent is an organic matting agent; the organic matting agent is pure polyester matting resin RB608 or pure polyester matting agent RB3329; The base material also includes the following raw materials in parts by weight: 30-40 parts of filler and / or 0.5-1 part of antifungal agent; The filler is one of the following: kaolin, diatomaceous earth, talc, graphite, calcium carbonate, alumina powder, glass powder, asbestos powder, mica powder, quartz powder, carbon fiber, powdered cork, and corundum. The antifungal agent is one of the following: phenols, organic mercury salts, organic copper salts, organic tin salts, copper sulfate, mercuric chloride, and sodium fluoride; Component B includes a crosslinking agent and a catalyst in a mass ratio of (8~10):(1~2); The crosslinking agent is one of polyethyl silicate, tetraethyl orthosilicate, and propyl orthosilicate; The catalyst is one of organotin catalysts, inorganic tin catalysts, and chloroplatinic acid; The organotin catalyst is one of butyltin, octyltin, dibutyltin, and dimethyltin. The inorganic tin catalyst is one of stannous chloride, stannous tetrachloride, and stannous oxide.

2. The method for preparing the functional topcoat that maintains the aerodynamic shape of the ceramicized heat-resistant coating as described in claim 1, characterized in that, The preparation method includes the following steps: (1) Mix all the raw materials of the base material, then add pigment and diluent, and stir evenly to obtain component A; (2) Mix the crosslinking agent and catalyst evenly to obtain component B; (3) Mix component A and component B, stir and disperse them, spray evenly on the surface of the substrate, and cure.

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