Layer-by-layer (LbL) deposition is very useful for flame retarding a variety of substrates. Recently, we have developed successful flame retardant (FR) coating systems for polyurethane foam (Macromolecular Materials and Engineering 2016), polyester-cotton blend (Carbohydrate Polymers 2015), and a 3 mm thick polystyrene plate (Advanced Materials Interfaces 2015). One of the most prominent features of LbL FR coatings is the prevention of melt dripping of all thermoplastic-based materials. Clay and other nanoparticle-based coatings act as thermally insulating barriers on the surface of these substrates, protecting the underlying material from further degradation. The image below shows how a “nanobrick wall” of clay and chitosan, both natural resources, form a protective barrier on the outer portion of polyurethane foam, shielding the interior from damage. By adding an intumescing multilayer coating on top of the clay, we can completely stop flame spread on foam (Journal of Materials Science 2015), as shown below.
