Effect of cross-link density on the high pressure crystallization of UHMWPE.

Ultrahigh molecular weight polyethylene (UHMWPE) is a bearing surface material for total joint implants. It is radiation cross-linked for high wear resistance and is melted or treated with vitamin E for oxidative stability. We investigated high pressure crystallization (HPC) of irradiated UHMWPE as an alternative method to improve the mechanical strength while stabilizing the residual free radicals from radiation cross-linking.

Improved resistance to wear and fatigue fracture in high pressure crystallized vitamin E-containing ultra-high molecular weight polyethylene.

Higher crystallinity and extended chain morphology are induced in ultra-high molecular weight polyethylene (UHMWPE) in the hexagonal phase at temperatures and pressures above the triple point, resulting in improved mechanical properties. In this study, we report the effects of the presence of a plasticizing agent, namely vitamin E (alpha-tocopherol), in UHMWPE during high pressure crystallization. We found that this new vitamin E-blended and high pressure crystallized UHMWPE (VEHPE) has improved fatigue strength and wear resistance compared to virgin high pressure crystallized (HP) UHMWPE.

FREE RADICAL ELIMINATION IN IRRADIATED UHMWPE THROUGH CRYSTAL MOBILITY IN PHASE TRANSITION TO THE HEXAGONAL PHASE.

Ultra-high molecular weight polyethylene (UHMWPE) is radiation cross-linked to decrease wear in total joint applications. Irradiation decreases the strength of UHMWPE and introduces residual free radicals, which can cause oxidation in the long-term. We advanced a method eliminating the free radicals without a reduction in strength.

The effects of high dose irradiation on the cross-linking of vitamin E-blended ultrahigh molecular weight polyethylene.

Vitamin E-stabilized, highly cross-linked ultrahigh molecular weight polyethylene (UHMWPE) is a promising oxidation and wear resistant UHMWPE with improved mechanical strength in comparison with the first generation, irradiated and melted UHMWPE. One approach of incorporating vitamin E in UHMWPE is through blending of vitamin E in UHMWPE powder followed by consolidation and radiation cross-linking. However, radiation cross-linking efficiency of UHMWPE decreases in the presence of vitamin E.