Tribological properties of polyalphaolefin oil containing POSS-based ionic liquids under atmospheric and atomic oxygen conditions for space tribosystems

This study aims to synthesize oil additives tailored for harsh space conditions, particularly atomic oxygen (AO) exposure, to enhance the lubrication performance of aerospace systems. To achieve this, polyhedral oligomeric silsesquioxane (POSS)-based ionic liquid (IL) with varying alkyl chain lengths (n = 8,16) were synthesized through nucleophilic substitution reactions, using octyl-functionalized polyhedral oligomers and halogenated hydrocarbons as precursors. The tribological and resistance AO irradiation properties of POSS-based IL additives (POSS-8-DOSS and POSS-16-DOSS) into PAO10 base oil were systematically investigated in atmospheric and vacuum environments. The properties of the formulated oil revealed that adding 1 wt% POSS-8-DOSS resulted in improved thermal stability compared to POSS-16-DOSS. Conversely, POSS-16-DOSS exhibited better performance in terms of corrosion resistance. Notably, the formulated oil containing POSS-based IL additives reduced the friction coefficient by 39.67–40.38 % in the atmospheric environment and by 65.94–79.89 % in the atomic oxygen radiation environment. Furthermore, the antiwear properties improved by 77.50–90.14 % in the atmospheric environment. Eventually, the results of this study provide valuable insights for advancing the field of aerospace lubrication.