TABLE OF CONTENTS Radiation has long been recognised as a means of sterilisation since X-rays were first demonstrated in 1896 to inactivate micro-organisms [1]. However, its practical application followed use of ethylene oxide (EO) because of the continuous improvement of plastic materials and medical devices, and the availability of improved electron beam accelerators and radioactive materials.
Radiation sterilisation is a near panacea for industrial sterilisation because of its excellent penetration capabilities, its fast release of treated products and simplicity of routine operation as compared to EO. But understanding its effect on polymers is of utmost importance [2, 3].
Many polymers have a natural tolerance for sterilising radiation doses of up to and beyond 50 kGy, with the notable exceptions of acetal, polypropylene (PP) and Teflon.
Sterilisation doses are orders of magnitude lower than the nuclear reactor environment in terms of 30-year lifetime, radiation in space, or even outdoor UV irradiation seen in automobile finishes, garden furniture, trash cans, etc. Solar incident energy is approximately 1 kW/m 2.
Only a few medical plastics cannot be sterilised by radiation, such as those likely to fail, which include acetal, PP (natural unstabilised) and Teflon, i.e., PTFE (others will be discussed later). Avoid these three materials and you can generally expect good results, but not always. However, many more polymers cannot be reprocessed, limiting the use of radiation sterilisation mainly for disposables but not reuseables.
Polymers react to electron bombardment by crosslinking their molecular chains to become stronger and stiffer or by scissoring (breaking) the...
