The Embrittlement of Nitinol Medical Devices During Sterilization

Device fractures during sterilization have been reported. Two common factors in these device fractures are the presence of a constraining force and a polymer coating or package. This paper investigates the effects of eBeam sterilization on Nitinol. The goal of the study is to identify coatings and packaging materials that adversely affect the properties of Nitinol when subject to eBeam sterilization. Superelastic Nitinol wires with various commercially available polymer coatings were eBeam sterilized and tested. Testing included, Bend and Free Recovery (BFR), tensile, and Hydrogen testing. The dosing was consistent with levels commonly associated with the sterilization of medical devices.

Key Words: nitinol, ebeam, sterilization, packaging, coating, embrittlement, fluorine, hydrogen, gamma ray, beta particle, dose, radiation, irradiation, kGy, outgas