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SYNOPSISThe present paper analyzes the thermolysis gross-kinetics of polypropylene ( P P ) and a PP-based fire-resistant composition containing 10% of hexabrominecyclododecane ( HBCD ) as the fire-retardant additive. The kinetic parameters of thermolysis of an individual PP are calculated by the isoconversion method. The increasing dependence of the effective activation energy on the transformation degree has been established. This dependence is attributed to the competitive character of the processes of thermodestruction initiated by oxidation and to the PP pyrolysis. Thermolysis in the helium atmosphere leads to oxidation suppression and increases the effective activation energy at the initial stage of thermolysis. A similar effect can be attained by introducing HBCD into PP, which permits considering the ability of inhibiting the oxidation process proceeding in the condensed phase as one of the reasons of the fire-retardant activity of this additive. JTRODl CTlONThis paper is a sequel to our previous Since then, we have carried out investigations aimed at elucidating the methods of calculation that permit obtaining reliable values of the kinetic parameters ( K P ) of a process. In particular, it has been found3 that besides the method4 of invariant K P (IKP), reliable information about KP can also be obtained by other methods that do not use the discrimination of formal models in solving the inverse kinetic problem. In this case, the KP obtained by the nondiscrimination methods, like the parameters calculated by the IKP method, display the property of invariance with respect to the choice of the process model. This fact makes it possible to dissociate the concept "invariant KP" from a concrete method of calculation, thus giving it a broader sense, namely: parameters calculated without any assumptions about the concrete form of the process model.Besides, it has been found5 that the application of the IKP method is limited by the gross-single-* To whom correspondence should be addressed. stage processes (i.e., by processes whose kinetics can be described by one rate constant). To obtain information about complex processes, a special approach was proposed previ~usly,~ which is based on the analysis of the shape of the transformation-degree dependence of the effective activation energy calculated by the isoconversion method. The isoconversion methods permit finding the values of K P that are not associated with the choice of the process model or, in other words, display the property of being invariant. Therefore, in this paper, which aims to study the kinetic features of thermolysis of pure polypropylene (PP) and a PP-based fire-resistant composition containing hexabrominecyclododecane (HBCD ) , all the kinetic information has been obtained from the viewpoint of the above-mentioned approach relying on one of the isoconversion methods.6The urgency of our investigation is due to the necessity of elaborating theoretically substantiated approaches to the solution of the practically important problem of increasing the ...

Analyzing the transformation-degree dependence of the effective activation energy, we have studied the thermolysis gross kinetics of polypropylene ( PP ) -based fire-resisting composition and a synergetic mixture of fire-retardant additives: antimony oxide and hexabrominecyclododecane (HBCD). The addition to PP of individual HBCD and in a mixture with antimony oxide increases the activation energy at the initial stage of thermolysis, which is attributed to the ability of fire-retardant additives to impede destruction initiated by oxidation. The investigation of the process proceeding in PP prior to the onset of decomposition in the presence of fire-retardant additives has shown that these additives stimulated crosslinking of polymer chains. The addition to PP synergetic mixture gives the greatest-compared to its individual components-content of the crosslinked fraction ( 10% ) , whose presence is likely to inhibit the proceeding of thermolysis by the oxidation mechanism.

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