The friction and wear of high density polyethylene (HDPE) composites reinforced by unidirectional continuous copper wires of 0.4 mm diameter are discussed in the work. Heat treatment processes (annealing, tempering and hardening) were carried out to study their effect on the tribological properties of the tested specimens.
Based on the experimental observations, it was found that friction coefficient displayed by the scratch of HDPE reinforced by copper wires decreased with increasing number of wires up to 8 then it started to increase at 10 wires. It seems that the presence of copper wires decreased the hardness of the polymeric materials so that the material removal by the indenter was easier while at number of wires 10, friction became between the scratching tool and wires themselves due to narrow area between wires that caused the increase of the friction coefficient. The influence of heat treatment of test specimens on their friction and wear was investigated. By annealing at 90 °C and hardening at 120 °C, friction coefficient significantly increased with increasing normal load while it decreased by tempering at 110 °C. Tempered specimens displayed the lowest friction values, while specimens without heat treatment showed the highest values. Friction coefficient displayed by HDPE composites reinforced by unidirectional continuous copper wires recorded lower friction for tempered test specimens followed by hardened and annealed ones.
Wear scar width of the tested composites slightly decreased with increasing number of wires. The wear decrease of the tested composites can be explained on the basis that the presence of wire reinforcement can restrain the deformation of the polymer matrix. Besides, plastic deformation, grooving and smearing of surface can be decreased by the strengthening effect of the reinforcement as well as the retarding action of the copper wire against the motion of the indenter. By annealing at 90 °C and hardening 120 °C the wear scar width increased with increasing normal load while it decreased by tempering at 110 ° C. Annealed specimens displayed relatively higher wear scar width than hardened and tempered specimens. Tempered specimens showed the lowest wear scar width values.