The mech. properties of ternary systems consisting of polypropylene (PP), EPDM and different types of inorg. fillers have been investigated. An optimization curve for impact resistance vs. storage modulus depending on the compn. is given. The dynamic mech. behavior of the composite can be described based on a three-phase van der Poel model. Solid-state NMR studies provide a first insight into the interactions on the mol. scale by observation of mol. mobilities.