A study of long-lived free radicals in gamma-irradiated medical grade polyethylene


Ultra-high molecular weight polyethylene (UHMWPE), used in orthopaedic implants, was irradiated with gamma rays at room temperature (23°C) in air or vacuum, and it was then stored in the same environment for 2yr at 23°C, 37°C, or 75°C. ESR measurements showed decay as well as changes from alkyl to peroxy and polyenyl radicals in air due to reaction with oxygen. In vacuum, on the other hand, radicals (primarily allyl) decayed without any observable transformation from one type to another. The residual concentrations obtained after 2yr of post-sterilization storage at 23°C, 37°C, and 75°C were found to be 15-20%, 10-15%, and 2-10%, respectively. © 2001 Elsevier Science Ltd. All rights reserved.

Publication Title

Radiation Physics and Chemistry