Basic Mechanisms of Thermal Degradation of the Compositions of Synthetic Restoration Polymers With Metal Oxides

Abstract

Using the method of diffuse reflection spectroscopy, we studied thermal degradation of the compositions of white pigments with a number of synthetic polymers intended for restoration of paint layers of paintings. It has been established that, starting with ∼340 K, the heating of polymer compositions with TiO₂, regardless of the polymer type, induces absorption in the pigment at 2.88 and ∼2.50 eV, which can be referred to color centers (CC) fixed to oxygen vacancies. In the spectra of the compositions of fluorine-containing polymers with MgO and Al₂O₃, absorption bands in the blue region, which are induced when T > 315–320 K, can be ascribed to the hole color centers in oxides. The measurement of temperature dependences for the rate of increase in the absorption bands in programmed heating permitted determination of the activation energies of thermal degradation E _td. The dependence of E _td on the polymer type is attributed to the fact that reactions on the surface of pigments are limited by the activation of bonds in adsorbed macromolecules.