Influence of ion bombardment on tribological properties of UHMWPE

Abstract

Medical grade UHMWPE-s: GUR 1020 and 1050, were subjected to ion bombardment with H 2 + , He + , Ar + or Ag + of different energy and various doses. The work presents changes to micromechanical profiles and surface morphology (AFM, SEM) of polyethylenes due to the treatment. Mechanisms behind the modification have been proposed owing to structural and chemical analyses by s-SIMS, FTIR-IRS, confocal Raman microscopy and ''nuclear depth profiling''. Studies revealed that hardness of the surface layer increases due to radiolysis, probably leading to cross-polymerization of polyethylene. The depth of modification is limited to the penetration of ion beam, being dependent on a dose and a kind of ions applied. The treatment results additionally in oxidation, which together with a development of the surface geometry is responsible for its hydrofilization and, in some cases bacteriostatic character. Friction and wear of polyethylenes under a high load, adequate to extreme conditions of exploitation of hip joints, can be reduced even by three times, due to a proper ion beam treatment.

Effect of nitrogen ion irradiation on the nano-tribological and surface mechanical properties of ultra-high molecular weight polyethylene

“…The polished face of the samples were irradiated with nitrogen (33 MeV) provided by the Buenos Aires Tandem Accelerator Tandar (20 MV) with a fluence of 1 × 10 12 Nano-tribological as well as nano-mechanical tests were carried out under nitrogen atmosphere.…”

“…Recent literature reports many data about the wear improvement of UHMWPE by using ion bombardment treatments such as ion implantation [11][12][13][14][15][16] and plasma immersion ion implantation [17][18][19][20]. The modified layer, which depends on the ion type and fluence (ions/cm 2 ), reaches depth values ranging from a few nanometers to one micrometer [12,16,21,22]. Swift heavy ion beams (SHI) irradiation is an alternatively good candidate for surface modification of UHMWPE [23][24][25].…”

“…Depth Sensing Indentation (DSI) techniques provide a wealth of valuable quantitative information regarding the surface mechanical behavior. They have been widely applied to characterize metals, ceramics, thin films and more recently polymeric materials including UHMWPE [12,13,15,[33][34][35][36][37][38].…”

On the comparison of changes induced in crystallinity and surface nanomechanical properties of ultra high molecular weight polyethylene by γ and swift heavy ion irradiations

“…It has been shown that ion beam implantation and plasma-based ion implantation techniques resulted in improved wear resistance of UHMWPE [11][12][13][14][15][16][17][18]. In these techniques, ions are implanted into the polymer substrate with energies in the order of keV and fluences ranging from 10 14 to 10 17 ions/cm 2 .…”

“…In these techniques, ions are implanted into the polymer substrate with energies in the order of keV and fluences ranging from 10 14 to 10 17 ions/cm 2 . The thickness of the affected layer varies from a few nanometers to 1 μm, depending on ion type and energy [11,12]. In polyethylene, the physico-chemical changes associated with ion implantation are chain scission, cross-linking, formation of double and triple bonds, dehydrogenation of the surface layers and creation of carbonaceous aggregates especially at high fluences [19,20].…”