Evaluation of two new white silicone thermal control paints under atomic oxygen

The exterior optical surfaces of satellites are directly exposed to the harsh space environment. Thermal control paints are resistant to the conditions encountered at low earth orbit (LEO): vacuum, atomic oxygen, thermal cycling, and ultraviolet radiation. In this paper two white paints were prepared by ultrasonic dispersing method for application to space structures. The white paints include zinc-oxide-pigmented silicone elastomer SilGel 612 (U1) and a zinc-oxide-pigmented silicone elastomer RT604 (U2). These coatings are electrically non-conductive. We present the behavior of thermal control paints under atomic oxygen (AO). The effects of AO exposure were studied by the mass loss of paint specimens and complementary techniques including scanning electron microscopy (SEM) and atomic force microscopy (AFM). Also the optical degradation in the reflectance spectra, solar absorptance and thermal emittance for U1 and U2 samples before and after AO exposure were investigated. The paints have promising AO resistance properties that could be suitable for space applications.

► Silicones are used in protection of underlying oxidizable surface coatings. ► Two white silicone paints (U1, U2) formulated and their surfaces studied under AO. ► The optical degradation and thermal emittance for these paints were investigated. ► U2 had better thermo-optical properties and surface roughness lower than U1 after AO.