Surface cross-linked UHMWPE using peroxides.

Crosslinking of ultra-high molecular weight polyethylene (UHMWPE) has been successfully used to improve its wear performance. Wear is a surface phenomenon and limiting crosslinking to a layer only on the surface is desirable, as crosslinking of the bulk of the implant reduces its mechanical strength and toughness. We present a novel technique to surface crosslink consolidated UHMWPE/vitamin-E blends by diffusing an organic peroxide into the polymer at moderate temperatures, followed by heating to above the peroxide decomposition temperature to cause crosslinking on the surface. We characterized the surface crosslink density and wear rate of surface crosslinked UHMWPE/vitamin-E blends with two different types of peroxides. Both peroxides resulted in surface crosslinking with an increase in wear resistance comparable to the state-of-the-art highly crosslinked UHMWPE used for orthopedic implants. The addition of the antioxidant vitamin-E led to higher oxidation resistance.