Tribological behavior of fullerene-vinyl pyrrolidone copolymer nanoball

A novel water-soluble fullerene-vinyl pyrrolidone copolymer was synthesized. TEM analyzes show that it presents an ideal spherical shape in water with an average diameter of about 43 nm. Four-ball test shows that the addition of a certain concentration of the fullerene copolymer to base stock can effectively raise the load-carrying capacity (PB value) and antiwear ability, and reduce the coefficient of friction. The optimum concentration of the additive was 0.3%. Electron probe microanalysis indicated that the additive results in a reduce of wear scar diameter and the amount of crackle and pitting. Elements C and N were well-distributed in the wear scar, implying that the fullerene copolymer forms continuous film on the rubbing surface. The improvements in friction, wear and load-carrying capacity were probably due to the presence of the fullerene copolymer, which might act as nanoball bearings, led to microcosmic elastic rolling lubrication.