Large-Scale Continuous Immersion System for Layer-by-Layer Deposition of Flame Retardant and Conductive Nanocoatings on Fabric

A continuous immersion system has been developed to deposit multifunctional, multilayer thin films using layer-by-layer assembly. An initial demonstration of this device is presented here by coating cotton fabric, a complex three-dimensional substrate, with a flame-retardant recipe composed of chitosan (CH) and poly(sodium phosphate) (PSP) and a conductive recipe composed of poly(diallyldimethylammonium chloride) and multiwalled carbon nanotubes stabilized with sodium deoxycholate. Electron microscopy images reveal an unaltered weave structure for the conductive coating and the formation of a CH/PSP protective thermal barrier on fabric coated by the machine. Flame retardant and conductivity measurements of continuously coated fabric achieve properties comparable to handmade samples, and the large-scale coater showed a high level of consistency. This unique device provides an important proof-of-concept and lays the groundwork for scale-up to an industrial-scale system that could be used to produce these nanocoatings commercially.