The effect of surface roughness and sliding speed on the wear mode of low density polyethylene was studied with multipass experiments at the high sliding speeds by the use of a pin-on-disk wear machine. Surface roughness was found to be the major parameter in determining the wear mode of the polymer at two different speeds of sliding. The wear mode was shown to be abrasive on the rough surfaces and adhesive on the smooth surfaces. The high wear rates occurring on the rough surfaces was related to the production of the large amounts of loose debris. The effect of speed was found to be an increase in the temperature on the smooth surfaces. This temperature rise was used to explain the increasing wear rate and the decreasing coefficient of friction. No effect of speed was detected for sliding on the rough surfaces, where the frictional energy was dissipated by the formation of loose debris particles. / Master of Science