The authors of the article studied the influence of inorganic flame retardants of aluminium hydroxides, magnesium, calcium, and natural mixture of hantite and hydromagnesite characterized by different decomposition temperatures on fire safety characteristics and thermal stability of PVC plastics. It has been determined that the joint use of magnesium hydroxide and aluminum hydroxide in a ratio of 1:1 increases the value of the OI and reduces the index «Maximum optical density of smoke». The use of aluminum and magnesium hydroxides, characterized by different decomposition temperatures during heating, makes it possible to extend the temperature range of flame retardants and to cool the combustion area more efficiently. The natural mixture of hantite and hydromagnesite improves the fire safety characteristics of PVC plastic only in combination with aluminum hydroxide. Its ability to improve the fire safety of polymeric materials results in endothermic degradation of the HCM over a wide temperature range, with the release of water and carbon dioxide. It is shown that zinc oxide and zinc borate used in the composition of fireproof PVC plastics significantly reduce its thermal stability. It has been established that the use of substances capable of neutralizing the adverse effects of the metals of variable valence – epoxidated vegetable oil, epoxy resin ED20, pentaerythrite, dipentaeriritrite and pentaerite ester blend, and mechanochemical stabilizers in highly filled compositions of PVC plastics allows reducing its combustibility, smokegenerating capacity and improve the technological properties, namely, thermal stability and flow rate of the melt. The most effective thermostabilizing agents are epoxy compounds. Additives are selected that contribute to improving the adsorption of fillers to the polymer matrix, as well as to a more uniform distribution of components in the PVC composition. Liquid mechanochemical stabilizers of glycerine monooleate and complex lubrication have effectively improved the technological and operational properties of PVC plastics. These additives reduce the surface tension of DOF and act as surfactants towards it. It is shown that improvement of interaction of fillers with polymer matrix allows obtaining a welldeveloped harness with smooth surface
