Facile deposition of environmentally benign organic-inorganic flame retardant coatings to protect flammable foam

The combination of clay and intumescent, also termed hybrid organic−inorganic coating is an attractive strategy to improve the flame retardancy of polyurethane foam (PUF). However, the fabrication of such flame retardants remains challenging as it requires the deposition of many layers to achieve the desired level of the intumescing effect. Herein, we describe a facile route to fabricate a hybrid clay−intumescent coating comprising a OnePot−deposited chitosan (CH)−phytic acid (PA) polyelectrolyte complex (PEC) intumescent stacked on top of a layer-by−layer self−assembled clay trilayer (TL) of poly−D −lysine, CH, and alginate-stabilized montmorillonite. Combustibility tests using cone calorimetry revealed that a PUF coating of CH−PA PEC intumescent on a 5 TL clay nanobrick wall (CH−PA@5 TL@PUF) can reduce the peak heat release rate (a critical flammability metric), peak rate of smoke release, and peak CO₂ production rate of neat PUF by 73%, 33%, and 65%, respectively. Additionally, this hybrid coating imparted UL−94 horizontal burning rating by avoiding melt dripping and flashover, while the neat foam was completely consumed during the UL−94 flammabilty test. The proposed method is adaptable for the facile construction of other multifunctional surfaces in various application fields.