Layer-by-Layer Assembly of TiO₂ Nanoparticle/Poly(acrylic acid)/Montmorillonite Trilayer Composite Films as Flame-Retardant Coatings

Abstract

In order to create green nanocoatings with high fire resistance, titanium dioxide (TiO 2 ), montmorillonite (MMT), and poly(acrylic acid) (PAA) are used as the flame-retardant (FR) system that is prepared by the layer-by-layer self-assembly technique. The thermal behaviors and FR performance of the coated fabrics and polyurethane foam (PUF) are determined by thermal gravimetric analysis, vertical/ horizontal flame tests, and a cone calorimeter. The effect of layering polymers between metallic nanoparticles (NPs) and clay sheets on growth behavior and flame retardancy is investigated. The assembly of a TiO 2 /PAA/MMT trilayer (TL) system, incorporating a polyelectrolyte layer between the inorganic layers, results in a significantly thicker and heavier coating. This could be attributed to the infiltration of PAA chains into the interstitial spaces of the clay sheets and TiO 2 NPs, which also introduce additional interactive sites. The addition of polymers in the multilayered composites greatly improves FR properties. Cone calorimeter analysis demonstrates that a 10 TL TiO 2 /PAA/MMT nanocomposite, approximately 160 nm in thickness, applied to PUF, completely suppresses the second peak heat release rate and enhances other fire-retardant properties relative to the TiO 2 /MMT system. The markedly enhanced flame retardancy observed in the TiO 2 /PAA/MMT system is attributed to the increased char yield facilitated by the incorporation of PAA. The addition of polymer layers promotes the deposition of a greater quantity of clay and TiO 2 NPs while maintaining a tightly packed nanobrick wall structure.