AbstractIn an effort to develop a more environmentally benign flame retardant for polyurethane foam (PUF), layers of halloysite clay nanotubes (HNT) stabilized by branched polyethylenimine (BPEI) or poly(acrylic acid) (PAA) are deposited from aqueous suspensions to create multilayered nanocomposite coatings. PUF is very flammable and widely used in upholstered furniture throughout the world. Foam treated with five BPEIHNT/PAAHNT bilayers, deposited using layerbylayer assembly, is rendered selfextinguishing in open flame testing. Cone calorimetry reveals that this coating reduces the peak heat release rate (pkHRR) by 62%. Due to the tubular morphology of HNT, small volatile gasses given off during combustion are trapped, so total smoke release (TSR) is reduced by 60%. Infrared spectroscopy suggests this multilayer film survives during combustion, forming an HNTrich barrier that prevents mass and energy transfer during open flame testing and calorimetry. The significant reductions in pkHRR and TSR, along with the selfextinguishing behavior, indicate that these halloysitebased multilayer films have the potential to greatly improve PUF fire safety. The low cost and natural abundance of HNT makes this technology especially amenable to widespread use.
