Advantages of flame retardants based on nitrogen compounds

Nitrogen compounds are a small but rapidly growing group of flame retardants (FR) which are in the focus of public interest concerning environmentally friendly flame retardants. Today their main applications are melamine for polyurethane flexible foams, melamine cyanurate in nylons, melamine phosphates in polyolefines, melamine and melamine phosphates or dicyandiamide in intumescent paints, guanidine phosphates for textiles and guanidine sulfamate for wallpapers. Their main common advantages are their low toxicity, their solid state and, in case of fire, the absence of dioxin and halogen acids as well as their low evolution of smoke. Their efficiency lies between that of halogen compounds and that of aluminum trihydrate and magnesium hydroxide. The metallic hydroxides split off water and are environmentally friendly, but their low activity requires high concentrations which change the mechanical properties of the matrix that they are applied to. In contrast to many halogen compounds, flame retardants based on nitrogen do not interfere with the set of stabilizers added to every plastic material. Recycleability has become important as many plastics are recycled. Flame retarded materials based on nitrogen compounds are suitable for recycling as the nitrogen flame retardants have high decomposition temperatures. In the field of cable jacketing they evolve less corrosive gases during combustion and do not damage the electrical installations. Flame retardants based on nitrogen are environmentally friendly because they do not add any new element to those already present in the polymers such as polyurethanes, nylons and ABS. In regard to waste disposal they are comparable with fertilizers as they possess the same elements of importance, namely nitrogen and phosphorous. In comparison with metallic hydroxides they are more efficient and deteriorate the mechanical properties of the plastic material less. The final and best argument is their moderate price. (C) 1996 Published by Elsevier Science Limited