The Influence of the Molecular Structure of Polyurethane on Vibro– and Electroinsulation Properties of the Tramway Structures

Theoretical and experimental investigations of the influence of the molecular structure of polyurethane on its vibro- and electroinsulation properties have been carried out. It was established that the rheological model of polyurethane and rubber corresponds to the Kelvin resilient-&-elastic solid. However, due to the lateral electrostatic repulsion between the C = O groups polyurethane has a higher resilient component under compression and subsequent reverse deformation and a higher elastic constituent during the reset after the tension. It conditions the enhanced ability of polyurethane to absorb vibrations in comparison with rubber. Due to the energonegativity, the C = O groups provide a high electrical resistance for the polyurethanes. The experimental data show that polyurethane compositions provide a decrease in the vibration velocity of the rail seat plate in comparison with the track on rubber rail pads and an increase in the electrical resistance between the rail and the plate. The availability of the C = O groups in polyurethane compositions is confirmed by the analysis of the IR-spectra of absorption. When polyurethane is operated under insulation conditions the intensity of C = O lines is decreased with time and it is indicative of the rupture of double bonds, loss of those groups and the degradation of rheological and electric properties.