<p>The increasing requirements for polymeric materials contribute to the expansion of the performance characteristics of products based on polymers. One of the ways to obtain new materials is the mixture of polymers in the presence of a compatibilizer, which contributes to the creation of nanostructure morphology and imparting high performance characteristics to the materials obtained. The study deals with the influence of the composition of the polymer blends of PVC / LLDPE and the type of compatibilizer on the thermo-oxidative destruction of the composition. It is shown that in compositions containing a compatibilizer, thermal decomposition occurs in several stages, the number of which increases in line with the concentrations of LLDPE in the blend. The graft copolymer formed by the reaction of radical recombination as PVC and LLDPE is responsible for the thermal stability of the composition in each stage of thermal decomposition. The role of the usage of chlorinated polyethylene as the compatibilizer, which contributes to the thermal stability of the composition has been demonstrated.</p>