Combination Intumescent and Kaolin-Filled Multilayer Nanocoatings that Reduce Polyurethane Flammability

Chitosan (CH), ammonium polyphosphate (APP), CH and poly(acrylic acid) (PAA)-stabilized kaolin (KAO) clay are deposited as quadlayers onto the surface of flexible polyurethane foam (PUF) via layer-by-layer assembly in order to improve the fire resistance of the foam. The effectiveness of this nanocoating on flame suppression is compared to control films without KAO and bilayer coatings. PUF coated with only five CH/APP/CH/PAA-KAO quadlayers (around 184 nm thick) maintains its open porous structure and self-extinguishes upon exposure to a butane torch flame for 10 s. Cone calorimetry reveals that this coating reduces the peak heat release rate and total smoke release by 66.8% and 59.3%, respectively, compared with uncoated foam. Thermogravimetric analysis under nitrogen indicates the combination of intumescent components and clay promotes char formation and improves the thermal stability of the polyurethane substrate. This multilayer coating has the potential to improve the fire safety for PUF, commonly used in home furnishings, and a variety of other polymeric substrates.