Flame-Retardant Coatings on Polyurethane Foams Deposited by Layer-by-Layer Assembly Approach

Abstract

Polyurethane foams (PUFs) are the largest group of polyurethane products and can be classified into rigid and flexible foams. Rigid PUFs are mainly used for heat insulation in the refrigeration, construction, and automotive industries. Flexible PUFs are also widely used in the fabrication of car seats and furniture. In general, PUFs are highly flammable because of their porous structure, large surface area, and good air permeability. Flame retardants containing phosphorus, halogen, nitrogen, and silicone can partially reduce the flammability of PUFs. Also, the presence of thermally stable groups such as carbodiimide, isocyanurate, and nitrogen-containing heterocycles in the structure of PUFs 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 nanocoatings on the surfaces of polymeric foams. In this method, polymers, nanoparticles, and various compounds are deposited on the surface of polymeric foams in thin layers through secondary interactions such as electrostatic forces, hydrogen bonds, and van der Waals interactions. This chapter presents an overview of the combustion mechanism and flame retardancy of PUFs and introduces LbL assembly techniques, applications of this method in improving the fire resistance of PUFs, and the flame retardation mechanism of LbL coatings on the PUFs. Finally, some suggestions are discussed to improve the flame retardancy of LbL coatings. © 2021 American Chemical Society. All rights reserved.