Effect of surfactant on wear of polymer nanocomposites

In the last decade, many studies were reported on the wear damage in polymers filled with different nanoparticles based on titanium-, aluminium-, zinc-, iron-, silicon-compounds, carbon nanotubes, clay, etc. Based on these studies, it has been suggested that the presence of nanoparticles possesses many advantages over micron-sized particles if all the nanoparticles are dispersed uniformly in the matrix and with good bonding (either physical or chemical) to the matrix. But, in our previous study on the wear behaviour of polymer nanocomposites [1], we have observed that whilst the above-mentioned conditions are needed, they may not fully control the removal of material. Thus, it is not totally valid to assume that nano-fillers will irrevocably improve the friction and wear properties and that other conditions may also have significant effects on material removal like tribochemical reactions that may occur during the wearing process between the nanocomposite and the counterface leading to the formation of a thin, stable transfer film on the counterface resulting in an effective'polymer on polymer' contact instead of a'hard metal/ceramic on polymer' contact. Moreover, in most previous studies, the role of the surfactant (unbound or excessive) which is used to improve the dispersion of nanoparticles in the polymer matrix is unclear.