For friction components served in the deep sea, the application of polymer composites is one of the most effective methods for lubrication failures. In this study, surface-treated SiO₂ aerogel nanoparticles were incorporated into the poly(butylene terephthalate) (PBT) matrix. The tribological properties together with mechanical and thermal properties, seawater wettability and absorption of binary nanocomposites were investigated. The results show that SiO₂ aerogel nanoparticles enhance the wear-resistance of composites by improving transfer behavior owing to their surface functional groups, small size and porous structure. However, the seawater pressure impedes the transfer of nanocomposites by degrading the adhesion between frictional interfaces, decreasing the cover area, 
continuity and thickness of transfer film.