Abstract
In order to use polymers at low Earth orbit (LEO) environment, they must be protected against atomic oxygen (AO) erosion. A promising protection strategy is to incorporate polyhedral oligomeric silsesquioxane (POSS) molecules into the polymer backbone. In this study, the space durability of epoxy-POSS (EPOSS) nanocomposites was investigated. Two types of POSS molecules were incorporated separately—amine-based and epoxy-based. The outgassing properties of the EPOSS, in terms of total mass loss, collected volatile condensable material, and water vapor regain were measured as a function of POSS type and content. The AO durability was studied using a ground-based AO simulation system. Surface compositions of EPOSS were studied using high-resolution scanning electron microscopy and X-ray photoelectron spectroscopy. It was found that with respect to the outgassing properties, only some of the EPOSS compositions were suitable for the ultrahigh vacuum space environment, and that the POSS type and content had a strong effect on their outgassing properties. Regardless of the POSS type being used, the AO durability improved significantly. This improvement is attributed to the formation of a self-passivated AO durable SiO2 layer, and demonstrates the potential use of EPOSS as a qualified nanocomposite for space applications.
Highlights
The low Earth orbit (LEO) space environment ranges from an altitude of 200 km up to an altitude of 1000 km [1]
We studied the effect of incorporation of these two types of polyhedral oligomeric silsesquioxane (POSS)
It is evident that the pristine epoxy is not compatible with the ASTM E595-15 acceptance criteria due to a total mass loss (TML) value larger than
Summary
Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations. The low Earth orbit (LEO) space environment ranges from an altitude of 200 km up to an altitude of 1000 km [1]. It is characterized by extreme conditions such as hypervelocity micro-meteoroids, space debris, ionizing radiation, ultraviolet (UV) and vacuum. UV (VUV) radiation, electrostatic discharge, extreme thermal cycles, atomic oxygen (AO), and ultrahigh vacuum environment (UHV) [2,3,4,5]. The pressure at LEO depends on the altitude and solar activity; at 160 km it is about 10−6 Torr while at 800 km it is about
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