Abstract
Due to good wear resistance Ultrahigh Molecular Weight Polyethylene (UHMWPE) is the material of choice for the load bearing surfaces of total joint implants. In order to improve its performance polymer parts are often modified by the use of ionizing radiation. Here we report on the use of electron and ion beams and gamma-rays for the purpose. UHMWPE samples were irradiated with 600 keV and 1.5 MeV electron beam with doses ranging from 50 to 500 kGy and bombarded with 1-10 MeV He- and 9 MeV Cl-ions to fluences ranging from 10(12) to 5 x 10(16) ions/cm(2). Co-bomb was used for gamma-ray irradiation. Polymer radiolysis due to the irradiations was studied by means of nuclear reaction analysis (NRA) using the H-1(N-15, alpha gamma)C-12 reaction. Hydrogen release increases with the applied dose and was correlated to the linear energy transfer (LET). Irradiated polymers oxidize rapidly when exposed to the air. Oxygen uptake profiles were determined using RBS. Correlation between radiolysis and oxidation has been revealed. Enriched in oxygen region extends to the depth at which radiation induced hydrogen release took place. Once started oxidation proceeds until the saturation concentration of about 10 at.% was attained. (C) 2009 Elsevier Ltd. All rights reserved.