Chitin based multi-layered coatings with flame retardancy an approach to mimic nacre: Synthesis, characterization and mechanical properties

Abstract

Nacre mimetic coatings are attractive candidates for food packaging, electronics, textiles, protective insulation, and flame retardant materials. Inspired by the hierarchical structure of nacre, we present an environmentally friendly strategy to construct robust and flame retardant films using chitin, which is an abundantly available biopolymer. Chitin was phosphorylated to make it water-soluble. Multilayered films were constructed by assembling poly (vinyl alcohol) (PVA), graphene oxide (GO) nanosheets, phosphorylated chitin (p. chitin), and laponite (LAP) via Layer-by-Layer (LbL) and vacuum-assisted filtration (VAF) assemblies. SEM micrographs revealed the nacre-like layered structure while photographic images showed a similar sheen to that of the mother of pearl. The fabricated coatings possess good mechanical properties with a reduced modulus of 25.53 GPa and hardness of 1.45 GPa. In addition, multilayered films exhibited iridescence and attractive flame retardancy. We believe that our strategy of embedding chitin offers cost-effective and environmentally friendly coatings for textiles, food packaging, barrier, and electronic materials.

Keywords: Chitin; Flame retardancy multi-layered; Laponite; Layer-by-layer assembly; Nacre; Nanoindentation testing.