Injection moulding of biodegradable implants.

In medical engineering, degradable polymers represent an attractive alternative for conventional materials to be used as implants in the body. They are used as drug deliveries or as plates and screws to fix broken bones. Since they are completely broken down by the human body, the second operation, which is generally required, can be avoided. A central problem is the processing of these polymers, because no stabilisers are allowed. This causes a partially relevant loss in molecular weight, which correlates directly with the mechanical properties. Tests carried out on an injection moulding machine and on a conical plate rheometer show the influence of temperature, shear, residence time and moisture on molecular weight reduction and mechanical properties.