Study of Stretched Polyurethanes Microstructure and Local Mechanical Properties

Elastic polyurethane is a synthetic elastomer consisting of hard and soft blocks forming inhomogeneous supramolecular structures in the material. In this work, the microstructure and stiffness of two polyurethanes differing in the density of supramolecular stiff fibrillar mesh woven into a softer matrix have been investigated by atomic force microscopy. The evolution of local properties under uniaxial tension, including the ultimate tensile state, is shown. The indentation of a stretched elastic polymer was modeled by the finite element method; the dependence of stiffness on the elongation ratio was obtained. This result was used for comparison with experimental data and estimation of local elongation of the stretched polyurethane. The obtained results explain and expand the macroscopic mechanical properties of the polymers.