Features of Thermodestruction of Secondary Polymeric Materials

Abstract

The analysis of modern chemical ideas about thermal destruction of secondary polymers (SP) as a source of valuable energy components, which are formed after their decomposition: gas component, synthesis oil and pyrocarbon has been carried out. It is shown that regardless of the composition of the secondary polymeric materials, thermal destruction takes place by the classical radical chain mechanism with the formation of a gas mixture of hydrocarbons, alkane-alkene mixture of different hydrocarbons (monomers and oligomers of SP) and pyrocarbon, which includes condensed aromatic structures. The dependence of the formation of monomers as products of thermal destruction of secondary polymers on their cohesion energy density (E_cog, kJ/mol) has been shown.

In a number of works the methods of thermal-oxidative and thermal destruction of polymers of different composition and structure have been considered, however, only a small number of works are devoted to the study of chemical transformations of secondary polymers, and even less to their mixtures. It is stated that the resistance of polymers (including secondary) to heat and the rate of their thermal decomposition depends on the chemical structure of the polymer or mixtures thereof. Completion of thermal processes of decomposition of secondary polymers takes place by recombination of formed radicals or their disproportionation with the formation of double bonds at the ends of macromolecules, as well as changes in fractional composition and formation of branched and spatial structures. It is stated that in the case of thermal destruction of secondary polymers that contain one (PVC) or several (PTFE) halogen atoms, there is almost quantitative release of hydrogen halides (HHal), which require additional disposal. Attention is also paid to the fact that the use of catalysts of different chemical nature in the thermal destruction of secondary polymers leads to a significant difference in the yield of gaseous and liquid products of radical-chain transformations.