When analysing the results obtained, two main trends can be observed. The first one is visible within the limits of a given sample -with the next processing stage, the MFR value increases slightly. This is due to the fact that each of the processing steps (extrusion, injection) is inextricably linked to high thermomechanical stresses that cause polymer degradation. Numerous scientific studies show that the decrease in the molecular weight of the polymer is associated with a decrease in its viscosity, and thus an increase in the mass flow rate . This observation is consistent with the polymer molecular weight values shown in Table .