A study of the tribological behavior of nano-ZnO-filled polyurethane composite coatings

The two different morphologies of ZnO nanoparticles and ZnO whiskers were used as the friction modifiers to improve the tribological behavior of the polyurethane (PU) composite coating. The tribological behavior of the PU coatings filled with different morphologies nanometer ZnO was investigated using a ring-on-block wear tests under dry friction condition, and the worn surfaces and the transfer films formed on the surface of counterpart ring were, respectively, studied by scan electric microscope (SEM) and optical microscope (OM). It was found that the addition of the low inclusion of ZnO nanoparticles and ZnO whiskers can improve the reducing-friction and anti-wear abilities of the PU coatings and ZnO whiskers, as the filler was superior to ZnO nanoparticles in terms of the ability to decrease friction coefficient and wear rate of the PU coating. The investigations of the worn surfaces showed that the fillers of ZnO nanoparticles and ZnO whiskers were able to enhance the adhesion of the transfer films of the PU coating to the surface of counterpart ring, so they significantly reduced the wear rate of the PU coating.