Innovative Approach to Rapid Growth of Highly Clay-Filled Coatings on Porous Polyurethane Foam

An innovative twist to fabricating layer-by-layer coatings resulted in transparent, high-content clay coatings on porous polyurethane foam. The addition of an anionic poly(acrylic acid) (PAA) monolayer between anionic clay and cationic branched-polyethylenimine (PEI) monolayers resulted in a trilayer nanocomposite structure with an order of magnitude thicker coating using 40% less monolayers than the conventional bilayer approach. The eight trilayer system thoroughly coated all internal and external surfaces of the porous polyurethane foam, creating a clay brick wall barrier that reduced the foam flammability by as much as 17% of the peak heat release rate and 21% of the total burn time. Though the flammability reduction is comparable to common commercial fire retardant polyurethane foam, the clay is used at a 50% lower amount and may be a greener solution as many of the commercial fire retardants (e.g., halogen bases) have potential environmental and health concerns.