A coating with low surface roughness and low infrared emissivity and preparation method thereof

Abstract

The present invention belongs to the technical field of surface functional materials and relates to a low-surface-roughness, low-infrared-emissivity coating and a preparation method thereof. The low-surface-roughness, low-infrared-emissivity coating is a one-component coating comprising a high-temperature-resistant resin system, coated aluminum powder, a filler, and a solvent; the weight percentages are as follows: the high-temperature-resistant resin system accounts for 50-60%, the coated aluminum powder accounts for 30-40%, the filler accounts for 2-5%, and the solvent accounts for 5-20%. The coating is used to prepare a low-surface-roughness, low-infrared-emissivity coating. The coating is resistant to high temperatures up to 400°C; has good leveling properties, with a surface roughness of ≤0.8μm; good hydrophobicity, with a water contact angle of ≥95°; high adhesion, with a pull-off adhesion of ≥15MPa; and low infrared emissivity, with an emissivity of ≤0.25.

Description

Technical Field

[0001] The invention belongs to the technical field of surface functional materials and relates to a coating with low surface roughness and low infrared emissivity and a preparation method thereof. Background Art

[0002] As the flight speed of aircraft continues to increase, the infrared characteristics of typical components are becoming more and more obvious. Coupled with the rapid development of infrared detection technology, aircraft are very vulnerable to attacks from infrared-guided weapons. Therefore, it is very important to reduce the infrared radiation characteristics of aircraft.

[0003] From the Stefan-Boltzmann law W=εσT 4 It can be seen that reducing infrared radiation energy requires reducing emissivity and temperature. Infrared low-emissivity coatings are currently the most widely used and most technically convenient way to reduce the infrared characteristics of aircraft. Infrared low-emissivity coatings are mainly used on aircraft surfaces, and surface roughness will affect the airflow field distribution on the aircraft surface during flight. As the surface roughness increases, airflow friction losses increase, reducing flight efficiency and increasing energy consumption. At the same time, airflow friction will cause the aircraft surface temperature to increase, increasing infrared radiation energy, reducing the effect of infrared low emissivity. Especially for engine components, surface roughness will directly affect their aerodynamic efficiency. Therefore, it is very important to reduce the infrared emissivity of the aircraft while reducing its surface roughness.

[0004] Infrared low-emissivity coatings mainly include metal micropowder coatings, metal films, and inorganic low-emissivity coatings. Inorganic low-emissivity coatings primarily utilize the electrical conductivity and negative temperature coefficient characteristics of metal oxides, but metal oxides have a high emissivity at room temperature. Metal films have very low infrared emissivity due to their high conductivity and low surface roughness, but their emissivity increases dramatically with oxidation, and they have high process requirements and poor compatibility with radar layers. Metal micropowder coatings have a simple process but are resistant to temperature differences. In addition, the coating has a high surface roughness, which affects aerodynamic characteristics and causes the accumulation of incomplete combustion products, forming a carbon deposit layer, which affects the low-emissivity characteristics. Given the characteristics of various current infrared coatings, we urgently need an infrared low-emissivity coating that is resistant to high temperatures and has a low surface roughness. Summary of the Invention

[0005] The problem that the present invention needs to solve is how to improve the temperature resistance of infrared low-emissivity coatings and how to achieve low surface roughness characteristics. The electrical conductivity of metals is the key to achieving low infrared emissivity. Energy absorption is achieved through electronic transitions of the metal, while the temperature resistance of the coating requires formula design to achieve. The currently used metal micropowder coatings mainly use flaky aluminum powder as a low-emissivity functional filler, and the flaky aluminum powder is suspended on the surface of the coating, which increases the surface roughness of the coating and forms carbon deposits during use. At the same time, the aluminum powder on the surface of the coating will oxidize at high temperatures, causing the infrared emissivity to increase sharply. In order to solve the above problems, the present invention prepares a high-temperature resistant, low-surface-roughness, low-infrared emissivity coating.

[0006] The technical solution of the present invention is a low-surface-roughness, low-infrared-emissivity coating, which is a one-component coating comprising a high-temperature-resistant resin system, coated aluminum powder, a filler, and a solvent; the weight percentages are as follows: the high-temperature-resistant resin system accounts for 50-60%, the coated aluminum powder accounts for 30-40%, the filler accounts for 2-5%, and the solvent accounts for 5-20%.

[0007] The high temperature resistant resin includes methylphenylsiloxane, cyanobenzoxazine, tetrahydrofuran, toluene, and phenol; the weight percentages are (10-12): (10-12): (1-2): (8-10): (8-10)

[0008] The preparation method of the high-temperature resistant resin comprises the following steps: weighing 20 g to 30 g of methylphenylsiloxane, 20 g to 30 g of cyanobenzoxazine, 2 g to 5 g of phenol, 18 ml to 25 ml of tetrahydrofuran and 18 ml to 25 ml of toluene, mixing the mixture and performing rotary evaporation at 80° C. to 90° C. for 24 h to 30 h to obtain the high-temperature resistant resin.

[0009] The aluminum powder is in the shape of a gold ingot or an ellipsoid, with a particle size of 8-10 μm, and is coated with silane phosphate.

[0010] The silane phosphate coating treatment method comprises weighing 50 g of aluminum powder, 8 ml to 10 ml of silane phosphate and 50 ml to 80 ml of acetone, mixing the mixture and stirring at 40° C. to 50° C. for 2 h to 4 h, and drying the mixture in an oven at 70° C. to 80° C. for 2 h to 3 h to obtain coated aluminum powder.

[0011] The filler is one or more compositions of boron nitride, silicon dioxide and titanium dioxide.

[0012] The solvent is a mixture of toluene, acetone, cyclohexanone and n-butanol, and the mass percentages thereof are (3-5):(1-2):(2-3):(2-3)

[0013] A method for preparing a low-surface-roughness and low-infrared-emissivity coating comprises mixing a high-temperature-resistant resin, coated aluminum powder, a filler, and a solvent in the above proportions, and stirring the mixture at 500 rpm for 30 minutes to obtain the low-infrared-emissivity coating.

[0014] A method for preparing a coating with low surface roughness and low infrared emissivity is disclosed. The method comprises the following steps: applying the coating by air spraying, keeping the coating at 200°C for 2 hours and then keeping the coating at 300°C for 2 hours to obtain the coating with low surface roughness and low infrared emissivity.

[0015] Compared with other methods, the present invention has the following beneficial technical effects:

[0016] 1. High temperature resistance, temperature resistance up to 400℃

[0017] 2. Good leveling properties, surface roughness ≤ 0.8μm

[0018] 3. Good hydrophobicity, water contact angle ≥95°

[0019] 4. High adhesion, adhesion by pull-off method ≥15MPa

[0020] 5. Low infrared emissivity, emissivity ≤ 0.25 DETAILED DESCRIPTION

[0021] The present invention will be further described below in conjunction with the embodiments:

[0022] A low-surface-roughness, low-infrared-emissivity coating is a one-component coating comprising a high-temperature-resistant resin system, coated aluminum powder, a filler, and a solvent; the weight percentages are as follows: the high-temperature-resistant resin system accounts for 50-60%, the coated aluminum powder accounts for 30-40%, the filler accounts for 2-5%, and the solvent accounts for 5-20%.

[0023] The high temperature resistant resin includes methylphenylsiloxane, cyanobenzoxazine, tetrahydrofuran, toluene, and phenol; the weight percentages are (10-12): (10-12): (1-2): (8-10): (8-10)

[0024] The preparation method of the high-temperature resistant resin comprises the following steps: weighing 20 g to 30 g of methylphenylsiloxane, 20 g to 30 g of cyanobenzoxazine, 2 g to 5 g of phenol, 18 ml to 25 ml of tetrahydrofuran and 18 ml to 25 ml of toluene, mixing the mixture and performing rotary evaporation at 80° C. to 90° C. for 24 h to 30 h to obtain the high-temperature resistant resin.

[0025] The aluminum powder is in the shape of a gold ingot or an ellipsoid, with a particle size of 8-10 μm, and is coated with silane phosphate.

[0026] The silane phosphate coating treatment method comprises weighing 50 g of aluminum powder, 8 ml to 10 ml of silane phosphate and 50 ml to 80 ml of acetone, mixing the mixture and stirring at 40° C. to 50° C. for 2 h to 4 h, and drying the mixture in an oven at 70° C. to 80° C. for 2 h to 3 h to obtain coated aluminum powder.

[0027] The filler is one or more compositions of boron nitride, silicon dioxide and titanium dioxide.

[0028] The solvent is a mixture of toluene, acetone, cyclohexanone and n-butanol, and the mass percentages thereof are (3-5):(1-2):(2-3):(2-3)

[0029] A method for preparing a low-surface-roughness and low-infrared-emissivity coating comprises mixing a high-temperature-resistant resin, coated aluminum powder, a filler, and a solvent in the above proportions, and stirring the mixture at 500 rpm for 30 minutes to obtain the low-infrared-emissivity coating.

[0030] A method for preparing a coating with low surface roughness and low infrared emissivity is disclosed. The method comprises the following steps: applying the coating by air spraying, keeping the coating at 200°C for 2 hours and then keeping the coating at 300°C for 2 hours to obtain the coating with low surface roughness and low infrared emissivity.

[0031] Example 1:

[0032] 50g of high-temperature-resistant resin, 40g of coated aluminum powder, 2g of titanium dioxide, and 18g of a mixed solvent were stirred at 500rpm for 30 minutes to produce a low-infrared emissivity coating. Application was performed using air spray and the coating was kept at 200°C for 2 hours and then at 300°C for another 2 hours to obtain a low-surface-roughness, low-infrared-emissivity coating.

[0033] The coating surface roughness is 0.6μm, the water contact angle is 98°, the adhesion is 16MPa, the infrared emissivity is 0.21, and the surface is intact without blistering or cracking after being kept at 400℃ for 10h.

[0034] Example 2:

[0035] 60g of high-temperature-resistant resin, 30g of coated aluminum powder, 3g of boron nitride, 0.5g of silica, and 6.5g of a mixed solvent were stirred at 500 rpm for 30 minutes to produce a low-infrared emissivity coating. Application was performed by air spray, followed by a 200°C temperature hold for 2 hours and then a 300°C temperature hold for 2 hours, resulting in a low-surface-roughness, low-infrared-emissivity coating.

[0036] The coating surface roughness is 0.5μm, the water contact angle is 102°, the adhesion is 18MPa, the infrared emissivity is 0.23, and the surface is intact without blistering or cracking after being kept at 400℃ for 10h.

Claims

1. A low surface roughness and low infrared emissivity coating, characterized in that: The low surface roughness and low infrared emissivity coating is a one-component coating, comprising a high-temperature resistant resin, coated aluminum powder, a filler, and a solvent; the weight percentages are as follows: the high-temperature resistant resin accounts for 50-60%, the coated aluminum powder accounts for 30-40%, the filler accounts for 2-5%, and the solvent accounts for 5-20%; The preparation method of the high-temperature resistant resin comprises weighing 20 g to 30 g of methylphenylsiloxane, 20 g to 30 g of cyanobenzoxazine, 2 g to 5 g of phenol, 18 ml to 25 ml of tetrahydrofuran and 18 ml to 25 ml of toluene, and performing rotary evaporation at 80° C. to 90° C. for 24 h to 30 h to obtain the high-temperature resistant resin; The aluminum powder is in the shape of a gold ingot or an ellipsoid, with a particle size of 8-10 μm, and is coated with silane phosphate.

2. The low surface roughness and low infrared emissivity coating according to claim 1, characterized in that: The silane phosphate coating treatment method comprises weighing 50 g of aluminum powder, 8 ml to 10 ml of silane phosphate and 50 ml to 80 ml of acetone, mixing the mixture and stirring at 40° C. to 50° C. for 2 h to 4 h, and drying the mixture in an oven at 70° C. to 80° C. for 2 h to 3 h to obtain coated aluminum powder.

3. The low surface roughness and low infrared emissivity coating according to claim 1, characterized in that: The filler is one or more compositions of boron nitride, silicon dioxide and titanium dioxide.

4. The low surface roughness and low infrared emissivity coating according to claim 1, characterized in that: The solvent is a mixture of toluene, acetone, cyclohexanone and n-butanol, and the mass percentages thereof are (3-5): (1-2): (2-3): (2-3).

5. The method for preparing the coating with low surface roughness and low infrared emissivity according to claim 1, wherein: The high-temperature resistant resin, coated aluminum powder, filler and solvent were mixed in the above proportions and stirred at 500 rpm for 30 minutes to obtain an infrared low-emissivity coating.

6. The method for preparing a coating from a coating having low surface roughness and low infrared emissivity according to claim 1, characterized in that: The coating with low surface roughness and low infrared emissivity can be obtained by air spraying and keeping the temperature at 200℃ for 2 hours and then at 300℃ for 2 hours.