Effect of electron-beam irradiation on structure of ultra high molecular weight polyethylene used in medical implants

Effect of electron beam irradiation with a dose equivalent to that used in practice during radiation sterilization of endoprostheses (26 kGy) or twice higher (2 (.) 26 kGy) on the change of UHMW-PE structure. UHMW-PE (trade name Chirulen 1120) is used for preparation of cups of hip endoprostheses. Structural changes of the polymer have been investigated using FT-IR method. Mainly the results of polymer oxidation (increase in the part of carbonyl groups of ketone, ester and perester types as well as of hydroxyl and vinyl groups) have been found. It was also found, using GPC method, that irradiation caused also partial degradation of macromolecules (reduction of molecular weight one order of magnitude) and crosslinking processes were favored by macroradicals formed (gel fraction part about 40 %, increase in melting temperature as well as in crystallinity degree).