Multi-walled carbon nanotube layer-by-layer coatings with a trilayer structure to reduce foam flammability

In order to improve the stability and growth speed of coating, a trilayer (TL) methodology was adapted and resulting film shows high thickness compared to the dimensions of the carbon nanotube. First, the multi-walled carbon nanotubes were functionalized via simple direct amination to be stabilized in the water with positive surface charge. Amine functionalized carbon nanotubes were deposited on polyurethane foam using layer-by-layer assembly with a TL approach. Additional polyethyleneimine layer promote the interaction between carbon nanotube and polymer layers resulting in uniform, durable and thick coating. The 440 ± 47 nm thick 4 TL coatings of polyacrylic acid, polyethyleneimine functionalized multi-walled carbon nanotubes, and polyethyleneimine completely covers the entire internal and external surfaces of the foam. Microscopic images confirm strong polymer/nanotube interaction due to additional polyethyleneimine layer and well dispersed carbon nanotube network on the polyurethane foam surface. The carbon nanotube network created by the layer-by-layer process significantly reduces the flammability of foam (e.g., 35 ± 3%) reduction in peak heat release rate and prevents pool fire by creating protective layer.