The effect of gamma-irradiation on ultra-high molecular weight polyethylene recrystallized under different cooling conditions

The effect of gamma -irradiation on the thermal and mechanical properties o f ultra-high molecular weight polyethylene (UHMWPE) used in orthopedic impl ants was investigated. UHMWPE was recrystallized with different cooling con ditions for the purpose of enhancing the crosslinking extent of the polymer after gamma -irradiation. UHMWPE was irradiated with gamma -ray to a dosag e of 10-500 kGy in air and nitrogen atmosphere. Differential scanning calor imetry, tensile characterization, creep deformity and wear were examined to determine the mechanical properties of the irradiated UHMWPE specimens. Th e crystallinity of the irradiated samples was increased with irradiation do se. The irradiated UHMWPE after recrystallization in a quenching condition had a higher crosslinking extent compared with the irradiated UHMWPE after slowly cooling. The irradiated UHMWPE after quenching had a lower wear rate than the irradiated UHMWPE after recrystallization in a slowly cooling con dition, and the wear rate of UHMWPE decreased with irradiation dose up to 2 50 kGy, which was about 40% of the wear rate of nonirradiated UHMWPE. (C) 2 001 Elsevier Science Ltd. All rights reserved.