Layer double hydroxide and sodium montmorillonite multilayer coatings for the flammability reduction of flexible polyurethane foams

Flexible polyurethane foam (PUF) is coated by layer-by-layer (LbL) assembly using branched polyethyleneimine (BPEI), poly(acrylic acid) (PAA), and two different charged nanoparticles, such as sodium montmorillonite (Na-MMT) and layered double hydroxide (LDH). Three different deposition strategies, that is, bilayer, trilayer, and quadlayer, exhibit different coating growth, morphology, and flammability properties. Changing the nanosheet from LDH to MMT dramatically alter the coating mass for the same number of layers. A five bilayer PAA/BPEI+LDH coating reduced the peak heat release rate by 40% and the average heat release rate by 70%, which is two times more effective than commercial fire retardants (FRs) and other LbL-FR coatings for PUF. MMT and LDH mixed multilayers resulted in effective flame-retardant coatings with less coating mass by manipulating the deposition strategy. This study manifests the flexibility of LbL to fine-tune flammability reduction by switching the coating weight gains, which is significant to accelerate the development of other LbL coating regardless of the intended applications. (c) 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 41767.