COMPARATIVE ANALYSIS OF THE COMPOSITION OF PETROLEUM POLYMER RESINS BY METHODS OF IR- AND NMR-SPECTROSCOPY

Petroleum polymer resins (PPR) are of great practical importance as modifying additives for improving the physical and mechanical properties and thermal stability of high-pressure polyethylene (LDPE) and ethylene-vinyl acetate copolymer (EVA), as well as enhancing the adhesive interaction of EVA with steel substrates. Based on the previously obtained results, it was assumed that the thermally stabilizing effect of PPR on the oxidation of polyolefins is associated with the presence of protons in the resins. However, the task of determining the types of protons that contribute to increasing the thermal stability of composite materials seems to be very difficult due to the fact that petroleum polymer resins do not have a stoichiometric formula. The most reliable results of assessing the composition of PPR can be obtained by combining spectroscopic methods, in particular, IR and NMR. In connection with the above, the study of the composition of resins by two complementary spectral methods (IR and NMR) seems to be an urgent task. It is shown that the NMR spectroscopy method does not allow for precise differentiation of the content of aromatic structures, providing only their total content according to the integral curve. Olefin protons (i.e. the content of double bonds) are determined by the chemical shift in the range of 4-6.2 ppm, but this does not take into account the protons at the base of norbornene bridges, the content of which is difficult to estimate, since their signal is superimposed on the signal of methyl and methylene protons in the α-position of the benzene ring. When using the IR ATR method, difficulties arise in interpreting signals due to oxidation of samples and adsorption of atmospheric impurities by their surface. Nevertheless, the combined use of both methods provides consistent and more detailed information on the composition of NPS. The combination of the two methods confirmed that all the studied resins contain protons that can participate in the processes of thermal stabilization of polyolefin composite materials.