The dynamic thermal and mechanical behavior of Polypropylene/Mica composites-with improved properties induced by the presence of succinil-fluoresceine groups onto atactic polypropylene with different grafting levels-is the subject of this article. A further correlation of these with the macroscopic mechanical performance of the composite materials is also discovered. The atactic polypropylenes containing succinil-fluoresceine grafted groups were previously obtained in our laboratories by chemical modification of a byproduct of industrial polymerization reactors. The interfacial modifications induced by replacing a little amount of polymer matrix in the composite material by the grafted atactic polypropylene is clearly concluded either from a microscopic or a macroscopic point of view.