Influence of sterilization procedures on thermoplastics, with special regard to modified surfaces

For materials intended for use in the medical setting their sterilizability is an indispensable prerequisite. In the case of most polymers the usual s terilization methods result in changes that even extend to cleavage of the polymer chains. A particular problem in this respect are the surfaces modif ied for improved biocompatibility investigated in the present study, which are characterised by enlarged contact areas For this reason, possible changes to three different thermoplastics commonl y used for medical applications (polyethylene, thermoplastic polyurethane, polycarbonate) were investigated. Steam, gas and radiation were used for st erilization. Tensile tests were employed to identify changes in mucosal characteristics caused by different sterilization techniques irrespective of the surface mo dification. Sterilization-related changes to the structure of the modified surfaces were investigated with the scanning electron microscope (SEM). Dif ferential thermo analysis (DTA) was used to determine changes in the therma l characteristics of the plastics. Clear tendencies with regard to the behaviour of the plastics after sterili zation with various techniques were found. A general statement about the compatibility of plastic materials with a spe cific sterilization method is not possible on the basis of this study. For every new polymeric product used for medical purposes, the characteristics required must first be defined and compliance with the permissible variatio ns of these characteristics investigated for each of the various sterilizat ion techniques available.