Ultra High Molecular Weight Polyethylene (UHMWPE) has been used for the bearing materials in joint arthroplasty owing to its superior mechanical properties and high chemical resistance. However, effects of gamma-irradiation and accelerated aging on the mechanical properties has not been revealed. In addition, although the addition of Vitamin-E to the gamma-irradiated UHMWPE has reported to prevent the fatigue crack propagation, the prevention mechanism has not been clarified yet. In order to understand the influence of gamma-irradiation, accelerated aging and Vitamin-E (α-Tocopherol) on the mechanical properties of UHMWPE, we carried out tensile test and fatigue test of UHMWPE fiber and fatigue crack growth tests of UHMWPE plates. For tensile test of fibers, the displacement at failure decreased by accelerated aging, but the decrease of displacement at failure was revealed by adding Vitamin-E. For fatigue test of fibers, virgin specimen was fractured at lower stress than tensile strength influenced by cyclic loading. Furthermore, the fatigue strength was lower for accelerated aging specimen than virgin one. For the fatigue crack growth behavior, addition of Vitamin-E reduced the decrease of ΔK_<th> by gamma-irradiation and accelerated aging.
