Polymers, burning processing

The purpose of fire-retardant systems is to reduce the heat supplied to the polymer below the critical level for flame stability. This can be achieved by modifying (generally decreasing) the rate of chemical or physical processes taking place in one or more of the steps of the burning process. 

PP/CNT nanocomposite102 on the surface of the matrix polymer is the primary pathway by which the nanoadditives enhance the thermal and fire resistance of the matrix polymer, because such crack-free and networked nanoadditive char barriers can significantly shield the heat and oxygen from the matrix polymer and thus reduce the heat release rate, i.e., slow the burning process (Figure 11.36).116... 

Reich, L. and Stivala, S. S. Elements of Polymer Degradation. McGraw-Hill, New York 1971 Tkac, A. Radical processes in polymer burning and its retardation. I. ESR methods for studying the thermal decomposition of polymers in the preflame and flame zones. J. Polym. Sci. Polym. Chem. Ed., 19, 1475 (1981)... 

Reduction of heat of combustion. This type of flame-retardant decomposes via endothermic processes or their decomposition radicals react with those from the polymer in endothermic reactions. By means of these additives, the over-aU heat of combustion can be reduced to such an extent that the burning process ceases to be self-supporting. 

The flame-retardant compound must be stable enough to stand up to processing with the polymer, but not too stable to give up its halogen when the polymer burns. 

Fluorine is more effective as an inherent flame retardant in the basic polymer than as a reactive flame retardant or additive flame retardant employed in later stages of the product. As part of the basic polymer, it functions essentially in the condensed phase. It is effective in the stages of decomposition and ignition, and increases the possibility of arresting the burning process at an... 

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