Expandable graphite as intumescent flame retardant for polyurethane foams: Mini review and application guidelines

Polymeric foams are widely applied in various industry branches and are commonly present in everyday life. The most diverse group of polymeric cellular materials are polyurethane foams, which offer an extensive range of properties and applications. Nevertheless, they are inherently flammable, which poses a severe threat to human safety and the environment. The multiplicity of ingredients used in foam formulations, as well as their higher ignitability compared to solid plastics, underlines the need for analysis of flame retardancy. Overcoming this limitation would not only enable saving many victims of fires but also complement the current sustainable aspects of polyurethane foams, so it should be considered a vital mission for both researchers and the industry. Nevertheless, apart from the performance, economic aspects and legal regulations also have to be considered, which effectively inhibits broader applications of many promising solutions. Therefore, simplicity and availability should always be considered important factors for potential applications. One of the most important flame retardants that combines these aspects is expandable graphite. The presented work summarizes the literature reports related to its applications as an intumescent flame retardant for polyurethane foams, pointing to the most critical aspects and providing guidelines for the potential applications.