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

trans-Vinylene unsaturations generated in ultrahigh-molecular-weight polyethylene (UHMWPE) after radiation treatment scales linearly with the absorbed dose level, and can serve as an internal dosimeter for determining the radiation dose level for sterilizing or crosslinking UHMWPE. We measured the trans-vinylene concentration using infrared spectroscopy and generated calibration curves for ultrahigh-molecular-weight polyethylene (ram-extruded GUR 1050) after cold e-beam, cold gamma, and warm e-beam irradiations. The trans-vinylene content increased linearly with the absorbed dose level in all cases except with cold gamma irradiation at dose levels higher than approximately 70 kGy. At that dose level the trans-vinylene content of the warm irradiated samples was higher than those of the cold irradiated samples. Following postirradiation melting, the trans-vinylene content of the gamma irradiated samples increased. Such trans-vinylene quantification can be an internal dosimeter for crosslinked UHMWPE when radiation is used for improving its wear resistance or sterilizing the device made thereof. It can also be utilized to assess the spatial uniformity of the absorbed radiation dose level.