The development of heterophasic PP-copolymers, which are necessary in many applications because of their specific property profile, requires large capacities in pilot plants (or at least in bench-scale reactors) for a systematic variation of the matrix and elastomer properties. A possible alternative are model compounds, where the different components are blended in am extruder The possibility to evaluate three main influence factors on mechanics of such systems, namely the viscosity ratio between matrix and elastomer phase, the phase compatibility and the composition of the elastomer phase, is demonstrated in a series of investigations. Morphology investigations based on transmission electron micrographs have proven to be an indispensable tool for obtaining systematic information about such blend systems, which can be further used for the development of reactor-based systems.