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Present paper is devoted to a comprehensive interpretation of the correlation existing between the dynamic mechanical thermal parameters and the molecular motions taking place in the polymeric phase in heterogeneous materials based on polypropylene. Consequently, it deals with the influence of a polypropylene grafted succinic anhydride interfacial modifier (iPP-SA) on the ultimate behaviour of these materials. This work has been performed by using four different samples consisting in isotactic polypropylene (iPP) and a 75/25 iPP/talc composite; both of them with and without added the interfacial modifier. The study has been tackled by evaluating the five different temperature dependent relaxation phenomena occurring in the polymer matrix.  The proven capability of dynamic mechanical analysis (DMA) to follow transitions, structural, and morphological changes in polymer based materials has been used in the present work to determine the interfacial phenomena caused by the presence of an interfacial modifier. Samples studied here were obtained by compounding the materials followed by compression moulding. This moulding technique was used in order to minimize additional effects on the final properties of the sample apart from the interfacial ones. Additionally, some thermal properties obtained under dynamical conditions were measured and correlated to the reorganization possibilities of the material through the amorphous-crystal interphase in the polymer. The effect of the solely interfacial agent on the neat polymer matrix behaviour has been shown to be a very important item to be considered when designing composite materials (this is a fact too often dismissed in composite based studies). Otherwise, it has been proved that the presence of the interfacial agent in the composite can be detected (even at the very little concentration used here) not only by the changes in properties but also by the fact that exhibit their own a transition apart from that of the iPP matrix. 

talc, polypropylene, interface, interphase, grafted polypropylene, dynamic mechanical analysis (DMA).