Evaluation of Protective Silicone/Siloxane Coatings in Simulated Low-Earth-Orbit Environment

摘要

A protective silicone/siloxane hybrid coating was prepared using a polysiloxane binder and nanophase silicon-oxo clusters. Siloxane clusters were formed in situ from sol-gel precursors during the UV-curing process, which is accomplished through a cationic curing mechanism at ambient temperatures. The binder of the coating was a methyl-substituted silicone oligomer, and the siloxane/silicon-oxo phase was prepared from tetraethoxysilane (TEOS). Alkoxy silane groups were also grafted onto the silicone oligomer to couple with a chain, to couple with the silicon-oxo clusters. Scanning electron and atomic force microscopy, x-ray photoelectron spectroscopy, and UV absorbance/transmittance studies were used to observe the silicone/siloxane hybrids performance in low-Earth-orbit simulators. The results show that a protective oxide layer was formed, and at moderate fluence levels (2.22 x 10~(21) atoms/cm~2) the silicone/siloxane hybrid coating did not exhibit microcracking and had appreciable specular transmittance.