In this work, based on the results of dynamic mechanical studies, the damping efficiency of two-layer polyurethane (PU) composites designed by gluing two films of synthesized PU with different glass transition temperatures (Tg) was estimated. The damping efficiency was estimated by the parameters of the mechanical losses (tanδ) peak. To vary Tg, three types of PU with different chemical nature and structure were synthesized. The effect of an increase in the difference between the Tg of the initial PU (ΔTg) on the damping efficiency of the two-layer PU composites formed from them is analyzed. The effective damping temperature range (ΔT) was estimated as the temperature range under conditions tanδ ≥ 0,3 and tanδ ≥ 0,6. It was shown that at ΔТg = 7 °С a two-layer PU composite has one relaxation maximum, and its temperature range of damping efficiency expands in comparison with ΔТ for individual PU. Under the conditions ΔТg = 23 °С and ΔТg = 30 °С, two-layer PU composites exhibit damping efficiency in two temperature regions at tanδ ≥ 0,3, which provides an additional temperature range of effective damping. The essential role of the PU structure of each of the layers in the formation of a two-layer composite by gluing has been determined. Easier penetration of residues of the adhesive organic solvent into the surface of the PU film with a linear structure leads to plasticization of the corresponding layer in the composite and reduces Tg. It is shown that a two-layer structure can be used to solve specific problems related to the adjustment or broadening the effective damping temperature range.
Role of Electronic Excitations in Ground-State-Forbidden Inelastic Collisions Between Ultracold Atoms and Ions
