Study of hydrogen annealing of ultrahigh molecular weight polyethylene irradiated with high-energy protons

Abstract

Ultrahigh molecular weight polyethylene, an important biomaterial for orthopedic implants, was irradiated with 2.6- and 3-MeV H+ ions at low doses from 5.7 × 1011 to 2.3 × 1014 ions/cm2. Fourier transform infrared spectroscopy showed that irradiation resulted in increased free radicals, carbon double bonds, and increased methyl and vinyl end groups. The free radicals resulted in poor polymer oxidative stability, as measured by increased carbonyl concentration. Hydrogen annealing after ion irradiation reacted with the free radicals generated during proton irradiation resulted in a 40–50% decrease in infrared absorption associated with carbonyl and prevented further oxidation.