Identification and quantification of irradiation in UHMWPE through trans-vinylene yield

trans-Vinylene unsaturations generated in ultrahigh-molecular-weight polyet hylene (UHMWPE) after radiation treatment scales linearly with the absorbed dose level, and can serve as an internal dosimeter for determining the rad iation dose level for sterilizing or crosslinking UHMWPE. We measured the t rans-vinylene concentration using infrared spectroscopy and generated calib ration curves for ultrahigh-molecular-weight polyethylene (ram-extruded GUR 1050) after cold e-beam, cold gamma, and warm e-beam irradiations. The tra ns-vinylene content increased linearly with the absorbed dose level in all cases except with cold gamma irradiation at dose levels higher than similar to 70 kGy. At that dose level the trans-vinylene content of the warm irrad iated samples was higher than those of the cold irradiated samples. Followi ng postirradiation melting, the trans-vinylene content of the gamma irradia ted samples increased. Such trans-vinylene quantification can be an interna l dosimeter for crosslinked UHMWPE when radiation is used for improving its wear resistance or sterilizing the device made thereof. It can also be uti lized to assess the spatial uniformity of the absorbed radiation dose level . (C) 2001 John Wiley & Sons, Inc.