Effect of Irradiation Treatment on Compressive Properties of Ultra-High-Molecular-Weight Polyethylene

Ultra-high-molecular-weight polyethylene (UHMWPE) is used as a bearing material in total joint prostheses. One of the criterion that determines the strength of medical UHMWPE is its tensile properties. However, its compressive properties, which play an important role in determining the durability of the contact surfaces of prostheses, have not yet been considered. In this study, we examined the effect of gamma and electron beam irradiation treatment on the compressive properties of medical UHMWPE. The compressive properties (Young's modulus and proof stress) of the gamma-irradiated specimens were higher than those of the nonirradiated specimens. The plastic flow pressure of the electron-beam-irradiated specimens was higher than that of the nonirradiated specimens. The inhibition of plastic deformation of the noncrystalline structure due to electron beam irradiation is considered to have increased the plastic flow pressure. The electron beam irradiation treatment was found to be effective for the surface enhancement of medical UHMWPE. An electron spin resonance signal was clearly observed in the irradiated UHMWPE specimen. These results indicated that dangling bonds were probably formed in the irradiated UHMWPE.