Green fabrication of an ionic liquid-activated lignocellulose flame-retardant composite

A flame-retardant lignocellulose composite was fabricated via ionic liquid activation assisted by hot-pressing. To obtain a dilated, isolated surface, lignocellulose was pretreated with an ionic liquid. After modification with an ionic liquid, micro/nanofibrils appeared on the surface of lignocellulose. Cross-linking between micro/nanofibrils was beneficial for the deposition of inorganic particles. Ammonium polyphosphate and aluminum hydroxide particles were deposited on the surface of lignocellulose via hydrogen bonding and van der Waals adsorption, forming a flame-retardant layer. The ionic liquid-activated flame-retardant lignocellulose composite exhibited better flame retardancy and higher mechanical strength than those of pure lignocellulose. Compared to those of pure lignocellulose, the heat release rate (HRR), total heat release (THR) and total smoke production (TSP) of lignocellulose-based ammonium polyphosphate/aluminum hydroxide (LPA) composites decreased by 78.5%, 35.71% and 88.24%, respectively. The LPA composites had a mechanical strength of 48.5 MPa, which was 33.99% higher than that of pure lignocellulose. This method provides a new approach for lignocellulose-based flame-retardant materials.