An Indentation Study of the Temperature-Dependent Properties of Modified Polyurethanes

Carbon nanoadditives are widely used as modifiers for various materials. An important issue is the effect of modification on the material properties, including the sensitivity to temperature changes. In this study, we performed fixed-temperature indentation of polyurethane samples produced by mortar technology with fullerenes and carbon nanotubes. It was found that the addition of modifiers not only changes the mechanical and rheological properties of the material, but also makes these properties more temperature dependent. Based on solving an axisymmetric contact problem of constant loading rate indentation of a viscoelastic half-space, a method was developed for determining material properties from experimental indentation curves obtained at different rates. The properties of the original and modified polyurethanes were determined at three fixed temperatures. The modifiers produced different effects: nanotubes increased stiffness, while fullerenes reduced it. The effect of ion plasma surface treatment, leading to the formation of a hard carbonized nanolayer, on the indentation results at different temperatures was also investigated.