Thin Films of Intumescent Flame Retardant-Polyacrylamide and Exfoliated Graphene Oxide Fabricated via Layer-by-Layer Assembly for Improving Flame Retardant Properties of Cotton Fabric

A novel intumescent flame retardant-polyacrylamide (IFR-PAM) was prepared by the copolymerization of N-1-(5,5-dimethyl-1,3,2-dioxaphosphinyl-2-yl)-acrylamide (DPAA) and acrylamide and was used to prepare various IFR-PAM/graphene oxide (GO) thin films via layer-by-layer (LbL) assembly as a flame retardant coating system for cotton fabric. Films assembled with IFR-PAM and GO nanosheets show linear growth as a function of the number of bilayer deposited. Higher hydrophobe DPAA content of IFR-PAM results in much thicker assemblies due to hydrophobic association. The results from X-ray diffraction (XRD), atomic force microscopy (AFM), and scanning electronic microscopy (SEM) indicate that the IFR-PAM/GO ultrathin films with high homogeneity and orientation are formed by LbL assembly driven by hydrogen interaction. The thermogravimetric analysis (TGA) results indicate that the IFR-PAM/GO coating improves the thermal stability of cotton fabric. Cone calorimeter testing shows that the IFR-PAM/GO-coated fabrics become less flammable with lower peak heat release rate (PHRR) and longer time to ignition (TTI). SEM images demonstrate that the surface of the IFR-PAM/GO-coated fabrics is covered by a layer of continuous and compact char after combustion.