In the processing of plastic granules to the finished product, the plastic melt is exposed to high shear rates, high temperatures for a residence time. This leads to molecular degradation of the polymer chains, which can have a particularly negative effect on the mechanical and optical properties. Since a prediction of the expected molecular degradation is not possible within the scope of the current state of the art, a test bench for defined damage as well as measurement of the thermoplastic samples was developed. The setup is similar to a Searle rheometer, so that defined damage can be introduced into the plastic by means of a rotating as well as temperature-controlled rotor. Torque monitoring simultaneously allows calculation of the viscosity, which is used to quantify molecular degradation. First of all, the requirements for the test bench had to be defined and a test chamber geometry has to be derived, which would allow accurate and reproducible measurements. In the course of the preliminary investigations, a test procedure was developed that allows representative measurements, taking into account influencing and disturbance variables. Consequently, the test bench allows a defined damage and measurement of plastic samples, from which the degradation behavior of the investigated plastic can be derived.