Vinylphosphonic acid/methacrylamide system as a durable intumescent flame retardant for cotton fabric

A novel intumescent flame retardant treatment, consisting of vinylphosphonic acid (VPA) as the acid source and methacrylamide (MAA) as blowing agent, was designed and applied onto cotton fabrics. The grafting of reactive monomers onto cellulose chains was carried out using potassium persulfate as initiator of a radical polymerization technique. The thermal and fire behaviour of the treated fabrics was thoroughly investigated: in particular, the VPA/MAA coating was able to exert a protective action, giving rise to the formation of a stable swollen char on the surface of textile fibers upon heating, hence improving the flame retardancy of cotton. In addition, the treated fabric achieved self-extinction as assessed by horizontal flame spread tests. Finally, a remarkable weight loss was observed only after the first washing cycle, then the samples did not show any significant weight loss, hence confirming the durability of the self-extinguishing treatment, even after five laundering cycles.