SHELF LIFE FAILURE PREDICTION CONSIDERATIONS FOR IRRADIATED POLYPROPYLENE MEDICAL DEVICES

摘要

In a standard method for assessing polypropylene syringe durability, the maximum bend angle before failure was used as a measure of the device ductility. Since the ductility of polypropylene is heavily dependent on deformation rate, choosing a realistic testing rate is critical to predict its shelf life accurately. In addition, irradiated polypropylenes undergo degradation when free radicals deposited by the radiation react with atmospheric oxygen to form a brittle surface layer. This brittle layer can create sharp notches and magnify the local strain rates causing the entire device to fail. Therefore, it is important to incorporate the effect of strain rate and degraded surface in the shelf life prediction of the polypropylene devices. For thin film applications, we found that oxidative induction time (OIT) test combined with oven testing can be used to predict its shelf life quite satisfactorily.