Coating-substrate systems consisting of polypropylene coatings with thicknesses of 6 and 9.8 mu m on silicon are investigated by depth-sensing indentation measurements with end loads between 20 and 1000 mN. Different effective load rates were applied. The results are correlated to an energy- and volume-related interpretation of the deformation processes. The proposed model permits to proof constant material behaviour over extended penetration depths. The potential on the quantification of the viscoelastic character as well as on the compound strength must be further verified.