High-temperature pyrolysis of polymers

Abstract

The experimental results on the pyrolysis of thermoplastic polymers under high-temperature heating and burning conditions are discussed. The reaction of polymer degradation in this case proceeds in the same way as in a low-temperature region.In this paper we discuss polymeric materials and their widespread application, in connection with the increase in their production. Attention is focused on their resistance to external exposure,and in particular to heating exposures of various intensities. Such exposure of a polymer surface results in heating of the polymer and leads to thermal degradation. The latter process is of paramount importance from different points of view.Questions concerning various aspects of the isothermal degradation of polymers and of theories of thermal degradation have been discussed in detail by a number of investigators; attempts have also been made to establish the dependence of the decomposition mechanisms of polymers on their structures. Comprehensive monographs on these subjects have been written by Jellinek [1], Grassie [2], Madorsky [3] and others [4,5].Extrapolation of the "isothermal" bulk degradation kinetics data to the range of pyrolysis rates usually encountered in surface pyrolysis and burning is considered invalid [6].The simplest case is the thermal degradation and pyrolysis of thermoplastics, i.e. when a polymer is gasified completely. In this connection, it becomes possible to study high-temperature degradation and pyrolysis under quasi-stationary conditions. In the case of polymers of the second and third types, a char residue accumulates on the condensed phase surface; this leads to a continuous change in the conditions of heat transfer in the interface between the gas and condensed phases. The present work is devoted to an analysis of experimental data on the pyrolyses of thermoplastic polymers.A number of techniques have been developed for study of the kinetic characteristics of pyrolysis. These cannot be studied by classical isothermal methods because the pyrolysis rates and temperatures are in ranges inaccessible to

Influence of Gas-Phase Reactions on the Product Yields Obtained in the Pyrolysis of Polyethylene

“…The literature on polymer thermal decomposition reports that the major products of the primary pyrolysis process are low or high molecular weight tars rather than gases (Sugimura and Tsuge, 1979;Hodgkin et al, 1982;Iida et al, 1975;Khalturinskii, 1987;Darivakis et al, 1990). The experimental data obtained in the FBR at low temperature (500 °C) these results.…”

“…On the other hand, there is still the need to study the product yields in the pyrolysis of plastic wastes and their dependency on the operating conditions. The studies present in the literature on the pyrolysis of polyethylene (PE), that is, the major com-ponent of plastic wastes, deal with the characterization of the weight loss rate during the primary thermal degradation (Darivakis et al, 1990;Jellinek, 1949;Madorsky, 1952;Oakes and Richards, 1949) and the primary product characterization (Hodgkin, 1982;Khalturinskii, 1987;Madorsky, 1965;Sugimura and Tsuge, 1979). Other papers refer to full-scale and pilot-scale pyrolysis or gasification plants (Kaminsky, 1992).…”

Durability of polymeric encapsulation materials for concentrating photovoltaic systems

“…Here, the initial behavior (at T 1 ) is attributed to the process of deacetylation, followed by breakdown of the remaining polyolefin chain (at T 2 ). The formation of char at the surface will limit heat transfer and the outward diffusion of product species . Certain additives may be used to promote char formation thereby reducing flammability .…”

Kinetic Study of Stabilizing Effect of Oxygen on Thermal Degradation of Poly(methyl methacrylate)

“…A number of workers ,,,,,,,, have reported the Arrhenius parameters for PMMA degradation (Table ). As we can see, the reported values of the activation energy vary almost by an order of magnitude.…”