Nitrogen-Based Ecofriendly Flame Retardants for Polyurethane Foams

Neat or virgin polyurethane foams are highly flammable materials. Increasing fire safety regulations have raised the usage of flame retardants (FRs) in polymers. Halogenated FRs typically release toxic gases during combustion, which harms human health and the ecosystem. To avoid these harmful gases, nonhalogenated FRs became the focal point of research, and the need for efficient nonhalogenated FRs is growing at a faster rate. The future belongs to halogen-free FRs, which lead to low toxicity, high thermal stability, and low evaluation of smoke. As the dominating nonhalogenated FRs, nitrogen-based compounds have been considered promising. They are incorporated into polymeric materials either as additives or reactive FRs, which can enhance the physical and mechanical properties of polymers. As nitrogen-containing FRs display high decomposition temperatures, they can efficiently be incorporated into recyclable materials, such as thermoplastics. Nitrogen-based FRs show effective FR properties when incorporated into the materials. However, they offer better properties in synergistic systems, such as melamine phosphate, ammonium polyphosphate, and so forth. In this chapter, the working mechanism of nitrogen-based FRs as nonhalogenated FRs in polyurethane foams—and the synergism of nitrogen and phosphorus—are reviewed in detail.