Ion beam modification of surface properties of polyethylene

Abstract

Improvement of polymer tribological properties is an essential issue for their application when used as parts of machines or artificial human joints. Ion implantation is a very promising technique in this respect. This paper presents the application of energetic He and Ar ions for this purpose. The materials studied were low-density (LDPE) and high-density (HDPE) polyethylene and their blends. Atomic force and scanning electron microscopes were used for studies of surface modifications. Tribological tests consisted of friction coefficient and nanohardness measurements. Our results have indicated clearly that ion bombardment produces important changes in the polymer surface morphology and its internal structure. The related micromechanical parameters strongly depend on polymer density. For the pristine samples, the friction coefficient increases with decreasing polymer density. For hardness, opposite tendency was observed. A significant increase of hardness and friction coefficient was observed for HDPE subjected to ion bombardment. In contrast, ion bombardment does not produce significant changes of tribological parameters in 50–50 blend and LDPE.