Multiple ion implantation effects on wear and wet ability of polyethylene based polymers

Polyethylene based polymers were ion implanted with multiple irradiations of different ions (N+, Ar+ and Kr+) at energies between 30 keV and 300 keV and doses ranging between 1013 and 1016 ions/ cm2. The ion implantation dehydrogenises the polyethylene inducing cross-link effects in the residual polymer carbons. At high doses the irradiated surface show properties similar to graphite surfaces. The depth of the modified layers depends on the ion range in polyethylene at the incident ion energy. The chemical modification depends on the implanted doses and on the specie of the incident ions. A “pin-on-disc” machine was employed to measure the polymer wear against AISI-316 L stainless steel. A “contact-angle-test” machine was employed to measure the wet ability of the polymer surface for 1 l pure water drop. Measurements demonstrate that the multiple ion implantation treatments decrease the surface wear and the surface wetting and produce a more resistant polymer surface. The properties of the treated surfaces improves the polymer functionality for many bio-medical applications, such a as those relative to the polyethylene friction discs employed in knee and hip prosthesis joints. The possibility to use multiply ion implantations of polymers with traditional ion implanters and with laser ion sources producing plasmas is investigated.