FEATURES OF MANIFESTATION OF ANTIOXIDANT PROPERTIES OF HYDROLYSIS LIGNIN IN POLYETHYLENE FILMS, ANTAGONISM OF LIGNIN AND LICHEN EXTRACTS

The work experimentally studied the antioxidant properties of hydrolyzed lignin powder in the composition of polyethylene films, showing the possibility of increasing the antioxidant capacity of lignin powder in the polymer matrix due to the adsorption of compounds with antioxidant properties on its surface. Samples of polyethylene films with a lignin content of 1–7% wt. obtained by thermal pressing. Thermal-oxidative testing of polymer films was carried out at a temperature of 150 °C. Monitoring of the oxidation process was carried out by IR spectroscopy, using the absorption band at 1720 cm-1, which corresponds to carbonyl groups. Experiments on adsorption of ascorbic acid and resorcinol (weak antioxidants) on the surface of lignin particles were carried out. An increase in the antioxidant properties of modified lignin in the composition of polyethylene films was noted. Lignin modification with Evernia prunastri lichen extracts; Parmelia sulcata; Hypogymnia physodes led to antagonism (negative synergism) of antioxidant properties in the polymer composition: the thermal-oxidative stability of the experimental polymer films turned out to be extremely low. At the same time, the extracts of the lichens Evernia prunastri, Parmelia sulcata, Hypogymnia physodes themselves exhibit high antioxidant activity in the composition of polyethylene films. The ATR spectra of lignin powders and UV/VIS spectra of lichen extracts were studied before and after mutual contacting. Analysis of the spectra indicates a decrease in the number of oxygen-containing groups of lignin, which determine its antioxidant capacity.