Mechanical and tribological properties of acrylonitrile-butadiene rubber filled with graphite and carbon black

In this work, acrylonitrile-butadiene rubber (NBR)/expanded graphite (EG)/carbon black (CB) micro- and nanocomposites were prepared by two different methods, and the resulting mechanical and tribological properties were compared with those of NBR/CB composites. Meanwhile, the effects of graphite dispersion and loading content, as well as the applied load and sliding velocity on the tribological behavior of the above composites under dry friction condition were also evaluated. The worn surfaces were analyzed by scanning electron microscopy (SEM) to disclose wear mechanism. As expected, the better the dispersion of graphite, the more remarkable enhancement on tensile and dynamic mechanical properties, and the greater reduction in the coefficient of friction (COF) and specific wear rate (W_s). It was found that a small amount of EG could effectively decrease COF and W_s of NBR/CB composites because of the formation of graphite lubricant films. The COF and W_s of NBR/CB/EG composites show a decreasing trend with a rise in applied load and sliding velocity. NBR/CB/EG nanocomposite always shows a stable wearing process with relatively low COF and W_s. It is thought that well-dispersed graphite nano-sheets were beneficial to the formation of a fine and durable lubricant film.