ENHANCEMENT OF MECHANICAL PROPERTIES OF UHMWPE POLYMER BY NITROGEN ION IMPLANTATION

The use of ion implantation as a surface treatment technology has been conquered by its applications to prevent wear and oxidation in metal alloys, even though some early works already pointed out that ion implantation could also be effective as a surface treatment for other materials, including polymers. Further research has shown that low dose implantation of energetic light ions could be very effective for improving properties such as wear resistance and hardness in many different polymers. Cross linking of polymeric chains due to ionization energy provided by the stopping process is the main mechanism to explain the changes in mechanical properties. According to this model the lighter the ion is, the stronger is the effect. This thesis presents the results obtained by nitrogen implantation in ultra-high molecular weight polyethylene (UHMWPE). N+ ions were implanted at 80 keV, 100 keV and 120 keV energy levels which are maintained at a fluencies or dose of 5×1015 ions/cm2 . Wear resistance was measured using pin-on-disc wear testing machine at a constant load of 18 kg or 177N with a sliding speed of 2 m/s for about 1000m sliding distance. The results clearly show a lower weight and volume loses for samples implanted with nitrogen, in comparison to those implanted with untreated samples. Hence from the results of weight and volume loses of the treated or implanted samples with nitrogen ion, gives very good wear resistance than untreated samples.