wear resistance and oxidation resistance of bioimplantable polymeric parts is improved by packaging the parts within flexible , gas impermeable containers while subjecting the containers and the parts to a relatively high vacuum force . the containers are heat sealed while subjected to the vacuum force such that , upon sealing , hydrostatic pressure is exerted on the part . following sealing of the packages , the packages and their contents are irradiated to an extent sufficient to sterilize the parts and to promote crosslinking within the part . alternatively , the same property enhancements can be imparted to polymeric parts by packaging the part within rigid or flexible containers , minimizing the oxygen content within the containers , pressurizing the containers with an inert gas , or with a mixture of hydrogen and an inert gas , to greater than 1 . 5 atmospheres , and irradiating the part and the container .