Based on analysis of free torsion oscillations, we study mechanical dynamical properties of the original components (polycarbonate (PC), polyethylene terephthalate (PETF), functionalyzed polyethylene (FPE), thermoplastic polyurethane (TPU), blockcopolymer of polycarbonate and polydemethylsiloxane (PC-PDMS), as well as of the mixtures (PC/PETF, PC/PETF/PC-PDMS, and TPU/FPE). It is shown that the dependences of shear modulus on the content of mixtures can be described by the Davies equation obtained for materials with double-phase continuity. We establish a direct correlation between the temperature dependences of the shear modulus of mixtures and the Davies equation and the zG3 -criterion, which characterizes interactions of phases in mixtures. This is an evidence of a considerable influence of interphase interactions on mechanical properties of mixtures with double-phase continuity. It is shown that in an interval of the b-process of relaxation of the tested polyesters and mixtures on their base, a plateau of dynamical shear modulus can be observed. Molar energy of interaction in the interval of low temperature plateau is equal to cohesion energy by Bondy. A temperature variation of molecular interaction estimated by the zG3 -criterion takes place in accordance with the development of typical relaxational transitions of components; at that, its intensification takes place in the case of consistent molecular dynamics, and its relaxation takes place in the case of inconsistent dynamics.