Marvelous abilities for polyhedral oligomeric silsesquioxane to improve tribological properties of polyamide-imide/polytetrafluoroethylene coatings

POSS-doped organic–inorganic nanocomposites (POSS referring to polyhedral oligomeric silsesquioxane) as a new generation of high-performance materials are of special significance, since they simultaneously possess the high rigidity and stability of inorganic species as well as the desired flexibility, ductility and processability of polymer species. Thus, octa(3-amino propyl) POSS (amino-functionalized POSS, denoted as NH 2 -POSS) was incorporated into polyamide-imide (denoted as PAI) to obtain a series of NH 2 -POSS/PAI hybrid composites. The molecular structures of NH 2 -POSS and NH 2 -POSS/PAI hybrid composites were analyzed by Fourier transform infrared spectrometry and X-ray diffraction. The impact of NH 2 -POSS on the thermal stability and mechanical properties of PAI as well as the tribological properties of PAI/PTFE-based (PTFE referring to polytetrafluoroethylene) bonded solid lubricant coatings was investigated. Findings indicate that the introduction of a proper amount of NH 2 -POSS leads to an increase in the glass transition temperature ( T g ) as well as hydrophobicity and microhardness of PAI. Besides, NH 2 -POSS contributes to reducing the friction coefficient and wear rate of PAI/PTFE-bonded solid lubricant coatings. Particularly, the introduction of 7% (mass fraction) of NH 2 -POSS leads to a decrease in the wear rate of PAI/PTFE-bonded solid lubricant coating by about 50%. This could be attributed to the increase in the load-bearing capacity and decrease in the surface energy of the polymer matrix coatings upon the addition of NH 2 -POSS.