Influence of the method of mixing of pigments with a polymer on the structure and properties of polyurethane compositions

The effect of the nature of pigments and the method of their addition on the properties of polyurethanes based on diphenylmethane diisocyanate and polyester is studied. Technical carbon black and titanium dioxide, which are added to a polyurethane composition in the presence of surfactants, are used as pigments. It is established that, upon the addition of pigments, the viscosity changes nonmonotonically, maximal values of viscosity being observed at a 20% concentration of technical carbon black. Optimal concentration of surface-active substances is found whose magnitude for technical carbon black is 0.25–0.5%. With an increase in surfactant concentration, they act as plasticizers abruptly lowering the intermolecular interaction. The effect of different surfactants on the rheological properties of polyurethane compositions is studied. It is shown that the addition of pigments makes it possible to enhance mechanical properties and to decrease internal stresses in films.