Pyrolysis of Polyurethanes. Process Features and Composition of Reaction Products

An increase in the production and consumption of polyurethane products used in heavy and light industry, in the construction industry, automotive, medicine, furniture industry, in the manufacture of sports equipment, brings about the need for their processing and disposal. Incineration of polyurethane waste leads to the release of toxic gases (NOx, HCl, various freons, and fluorine-containing hydrocarbons) and the formation of polycyclic aromatic and heterocyclic compounds, polychlorinated dibenzodioxins and dibenzofurans, and other corrosive-aggressive chlorine-containing compounds. Thermal processing of polyurethanes in an inert atmosphere, i.e., pyrolysis, in contrast to the polymer decomposition in an oxidizing medium, results in the formation of a larger amount of oxygen-containing compounds, which raises the problem of studying the optimal conditions for the polyurethane waste pyrolysis. The formation of halogen- and phosphorus-containing organic compounds, due to the presence of chlorine, fluorine, phosphorus in flame retardant additives that improve the thermostable properties of polyurethanes, significantly reduces the quality of the resulting pyrolysis products, which affects their further use. The review describes the principles and mechanisms of polyurethane degradation. The influence of the polymer structure, the process temperature, the nature of the carrier gas, and the presence of a catalyst on the thermal polyurethane degradation and the formation of products in the gas and condensed phases is considered.