Intumescing multilayer thin film deposited on clay-based nanobrick wall to produce self-extinguishing flame retardant polyurethane

Significant loss of life and property results each year from fires fueled by polyurethane found in household furnishings. Established layer-by-layer flame retardant systems were combined to produce a stacked nanocoating for flame retarding polyurethane foam. A bilayer system of chitosan (CH) and vermiculite provides a nanobrick wall exoskeleton, protecting the polyurethane long enough for an intumescing system of CH and ammonium polyphosphate to activate and form a bubbled char layer. Stacking these two recipes allows the foam to self-extinguish when exposed to a butane torch without any flame spread or shrinking of the foam, two things commonly observed with either coating alone. Cone calorimetry revealed a significant peak heat release rate reduction of 66 % relative to the uncoated foam. This study demonstrates the ability to combine flame retardant mechanisms sequentially. This nanocoating acts as an environmentally benign template for flame retarding various complex substrates, especially those found in household furnishings.