Bioinspired Lamellar Barriers for Significantly Improving the Flame-Retardant Properties of Nanocellulose Composites

The traditional addition of phosphorus-containing flame retardants could improve the flame retardance of polymeric materials, but it usually deteriorates the mechanical strength and thermal stability. Herein, we report an interlayer-confined synthesis of multilayer zirconium phosphate-reduced graphene oxide (ZrP-RGO) nanoplates, which were incorporated into cellulose nanofibers to fabricate the hierarchical nanocellulose composites through a structural inspiration of nacre. The lamellar barriers consisting of highly aligned ZrP-RGO nanoplates along a planar orientation contribute to suppressing heat and mass transfer between the flame zone and underlying matrix, which gives rise to 75.1%, 71.4%, and 54.6% reductions in the peak heat release rate, peak smoke release rate, and peak CO production rate of nanocellulose composites, respectively. Moreover, the hierarchical nanocellulose composites simultaneously achieve better thermal stability, mechanical strength, and toughness compared to pure cellulose nanofibers. The formation of bioinspired lamellar barriers provides an innovative idea to significantly improve the flame retardance of nanocellulose composites, as well as thermal stability and mechanical properties.