عنوان مقاله [English]
Polyurethane foams (PUFs) are the largest group of polyurethane products and can be classified into rigid and flexible foams. Rigid polyurethane foams are mainly used for heat insulation in refrigeration, construction, and partly in automotive industry. Flexible polyurethane foams can be also used widely in fabrication of car seat and furniture industry. In general, polyurethane foams are highly flammable due to their porous structure, large surface area, and good air permeability. Flame retardants containing phosphorus, halogen, nitrogen and silicon can partially reduce the flammability of polyurethane foams. Also, the presence of thermally stable groups such as carbodiimide, isocyanurate, and nitrogen-containing heterocycles in the structure of polyurethane foams can increase their fire resistance. In the last two decades a new technique called layer-by-layer (LbL) assembly has been introduced for the preparation of flame retardant nanostructured coatings on the surfaces of polymeric foams. In this method, polymers, nanoparticles and various compounds are placed in thin layers through secondary interactions such as electrostatic forces, hydrogen bonds and van der Waals interactions on the surface of polymeric foam. This paper presents a brief overview of the combustion and flame retardancy of polyurethane foams, introduction of layer-by-layer assembly technique and application of this method in improving the fire resistance of polyurethane foams, flame retardation mechanism of LbL coatings and different types of these coatings. Finally, suggestions for improving the efficiency of layer-by-layer coatings are discussed.