Effect of TEOS on the Properties of Silicone Based High Temperature Resistant Thermal Control Coatings

The work aims to study the evolution of microstructure and spectral absorption/emission properties of different components of organosilicon-based thermal control coatings, and reveal the effect mechanism of coating components on coating properties. The organic/inorganic hybrid binder was prepared by sol-gel method with tetraethyl orthosilicate, methyl triethoxysilane, dimethyl diethoxysilane, 3- (isobutylloxy) propyl trimethoxysilane as raw materials. A high temperature resistant thermal control coating was prepared with TiO2 as pigment and mica as functional filler. At the same time, the coating without pigment filler was used as the control group to carry out comparative test. The experimental results showed that the low solar absorption ratio and high hemispherical emissivity of the coating were caused by the combination of the substrate and the pigment, and the pigment had a higher contribution to the solar absorption ratio of the coating, but less contribution to the hemispherical emissivity. However, the content of TEOS in the substrate also affected the variation trend of solar absorption ratio and hemispherical emissivity. The higher the content of TEOS, the lower the solar absorption ratio and the higher the hemispherical emissivity. This was because the increase of TEOS content reduced the refraction coefficient of the binder, resulting in the increase of the reflectivity of the coating, which led to the increase of the solar absorption ratio, while the increase of the hemispherical emissivity was because the increase of TEOS content led to the increase of the coating porosity, which was conducive to the absorption of the corresponding infrared wavelength, and the hemispherical emissivity increased. The phase, surface microstructure, optical property and thermal stability of the coating were studied by means of FTIR and SEM. The FTIR results showed that the synthetic material mainly contained Si—O—Si bonds, and small organic molecules were successfully grafted on the main chain. The binder was successfully prepared. SEM results showed that the surface of the coating cured at room temperature was smooth and intact. When the molar ratio of TEOS was 8, the coating had the lowest solar absorption ratio and the highest hemispherical emissivity, with values of 0.209 and 0.901, respectively. At 600 ℃, FTIR results showed that the organic components of the coatings decomposed. The SEM results showed that the coating surface with molar ratios of 5 and 6 was defective, while the coating surface with molar ratios of 7 and 8 was intact and did not fall off with the substrate. The thermal stability of the coating increased with the increase of TEOS content. When the molar ratio of TEOS was 8, the thermal stability of the coating was the highest. The solar absorption ratio and hemispherical emissivity of the coating after curing at room temperature are related to the content of TEOS. The solar absorption ratio decreases with the increase of TEOS content, and the hemispherical emissivity increases with the increase of TEOS content. The thermal stability of the coating increases with the increase of TEOS content. © 2024 Chongqing Wujiu Periodicals Press. All rights reserved.