Construction of multilayer coatings for flame retardancy of ramie fabric using layer-by-layer assembly

Complex multilayer coatings composed of -zirconium phosphate (ZrP), polyethylenimine (PEI), and ammonium polyphosphate (APP) were constructed via layer-by-layer assembly method for flame retardant ramie fabric. Bicomponent PEI/ZrP layers served as insulating barrier coating, and bicomponent PEI/APP layers served as intumescent coating. The flame retardancy of the coated ramie fabric was strongly dependent on the nature of the coatings and the layer-by-layer assembly patterns. The coated ramie fabric with inside PEI/ZrP layers and outside PEI/APP layers possessed the most uniform and consistent coating surface morphology, as well as the highest content of N and P elements, resulting in an excellent improvement in flame retardancy of ramie fabrics. When this kind of coated ramie fabric was heated, the inner PEI/ZrP layer effectively prevent oxygen and heat from penetrating into the substrate, and the outer PEI/APP layer exposed to air with good expansion during combustion. The synergistic effect was formed during the combustion process and could impart ramie fabrics with high flame retardancy. (c) 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017, 134, 45556.