Super Gas Barrier and Fire Resistance of Nanoplatelet/Nanofibril Multilayer Thin Films

Cellulose nanofibrils (CNF) are abundant in the fiber cell walls of many plants and are considered a nearly inexhaustible resource. With the goal of improving the flame resistance and gas barrier properties of cellulose-based films, cationic CNF are assembled with anionic vermiculite (VMT) clay using the layer-by-layer deposition process. The highly aligned VMT nanoplatelets, together with cellulose nanofibrils, form a nanobrick wall structure that exhibits high optical transparency, flame resistance, super oxygen barrier, and high modulus. A 20 CNF/VMT bilayer (BL) nanocoating, with a thickness of only 136 nm, exhibits an oxygen transmission rate of 0.013 cc (m(2) day atm)(-1). With only 2 BL of CNF/VMT, the melting of flexible polyurethane foam exposed to a butane torch is prevented. These nanocoatings also exhibit a high elastic modulus (20 GPa) and hardness (1 GPa). This study demonstrates a unique, renewable, cellulose-based nanocoating that could be used in a variety of packaging and protection applications.