LIFE-SPAN-INDICATOR FOR RESTERILIZABLE PR ODUCTS MADE OF PLASTIC MATERIALS

Semi-disposable products in which only part of the product is disposab le while another part made of plastic is designed to be reusable, are an effective counter to the increasing masses of plastic waste generat ed by hospitals. The major problem with such products has been the fac t that the resterilizable parts could withstand only a limited number of resterilizations and the user had no means of seeing when this numb er had been reached. To resolve this problem, the Life-Span Indicator was developed in cooperation with Beiersdorf AG. This indicator change s colour from blue to orange after about 100 sterilizations. It is bas ed on an azo pigment diffused into a carrier polymer, POM. Repeated he ating of the pigment polymer results in the formation of acidic monome rs, which are responsible for the slow colour change of the pigment. N ot all the details of the mechanisms involved are clear, but the indic ator functions reliably and reproducibly. Since the pigment is inside the polymer, the colour-change reaction is not affected by mechanical pre-cleaning or disinfection. The user can thus readily see how long h e can use such products without risking malfunction. The number of res terilizations can be varied to suit the product, and the indicator can be shaped as required, for example as a nonseparable snap-in plug or a cable binder.