The present work investigates the possibility to introduce new self-lubricating polymeric materials for dry sliding bearing applications. The proposed polymeric composites are consisting of high density polyethylene (HDPE), low density polyethylene (LDPE) and polystyrene (PS) filled by paraffin oil and reinforced by carbon nanotubes (CNTs). Experiments were carried to test the frictional properties of the proposed composites at dry sliding conditions. The experiments showed that filling HDPE, LDPE and PS by paraffin oil and reinforcing them by CNTs can decrease the friction coefficient and increase wear resistance significantly.This may be referred to the presence of oil in multipores inside the polymer matrix, where they work as reservoirs of oil from which it leaks up to the sliding surface and causes friction decrease, where the contact will be between partially polymer composites/steel and oil/steel due to the mixed lubrication regime offered by the oil film. Besides, oil film can isolate the contacting asperities of the sliding surfaces from excessive wear, where high shear tearing and transfer of polymer to the steel surface were diminished.The self-lubricating mechanism of CNTs during sliding depends on the rolling movement of the CNTs, where they change friction and shear stress into rolling. This mechanism can be achieved when the nanotubes can have the medium in which they can move freely. Presence of oil can provide this facility that decreases both friction and wear.
Eatemad et al. (Sun,) studied this question.