Synergistic Flame Retardancy Enabled by Boehmite/Poly(Acrylic Acid)/Graphene Oxide Hybrid Multilayered Nanocomposites

Abstract

In this work, we report an environmentally benign and highly effective flame retardant (FR) nanocoating developed via layer-by-layer (LbL) assembly. The coating consists of alternating cationic boehmite (BMT) and anionic graphene oxide (GO) layers, applied to polymeric substrates such as cotton fabrics and polyurethane foams (PUF). By integrating a polyelectrolyte interlayer of poly(acrylic acid) (PAA) between the inorganic and organic components, the resulting BMT/PAA/GO LbL assemblies achieve substantially thicker and denser coatings. This enhancement in growth behavior arises from PAA chains occupying the interstitial layers within the clay/carbon nanoparticle matrix and generating additional interaction sites. Thermogravimetric analysis (TGA) reveals that BMT/PAA/GO coatings effectively modify the thermal decomposition pathway of cotton fabrics, promoting char formation and thereby improving flame resistance. Furthermore, cone calorimetry experiments demonstrate that these clay/ polymer/carbon nanocomposite layers considerably outperform FR performance of bilayer coatings (BMT/GO). PUF samples coated with a 10-trilayer BMT/PAA/GO system (~250 nm thick) exhibit effective suppression of the second peak heat release rate, indicating superior flame inhibition. The enhanced protection is attributed to the elevated char yield facilitated by PAA, which increases clay and carbon nanoparticle loading while preserving a densely packed BMT/GO architecture.

Keywords: layer-by-layer assembly, Flame retardants, Polymer Nanocomposites