Halogen-Based Flame Retardants in Polyurethanes
Nycolle G. S. Silva, Noelle C. Zanini, Alana G. Souza, Rennan F. S. Barbosa, Derval dos Santos Rosa, Daniella R. Mulinari
Abstract
Polyurethanes are polymeric materials widely used in all consumer goods and industrial markets. However, their flammability is a serious problem that, associated with the various tragedies that occur annually involving fires, has highlighted the urgent need to reduce the material’s flammability. Flame retardants (FRs) are added to the polymers to improve their fire performance and can be divided into three main types: halogen-based FRs (HFRs), halogen-free FRs, and nano FRs. The HFR is the most common class and includes a broad range of structures, such as brominated FRs (BFRs), chlorinated FRs (CFRs), fluorine, and iodine, where the primary element inhibits fire propagation by substituting •OH and •H free radicals. BFRs and CFRs have broad industrial applications because of their low cost and high effectiveness. More than 75 different BFR compounds are commercially available, and the tetrabromobisphenol A and hexabromocyclododecanes are the most used materials. After thermal decomposition, these materials generate gaseous bromine forms (HBr, Br, and Br2) and char. The main CFRs are straight-chain paraffin, cycloaliphatic hydrocarbons, aromatic hydrocarbons, and organophosphate compounds, generating HCl and a cross-linked chlorinated residue. In this chapter, the HFR mechanisms in polyurethane foams are reviewed in detail, focusing on the main brominated and chlorinated compounds, and their benefits, harms, suppliers, future trends, and new technologies developed.