Layer by layer deposition of polyethylenimine and bio-based polyphosphate on ammonium polyphosphate: A novel hybrid for simultaneously improving the flame retardancy and toughness of polylactic acid

Abstract

In this study, a facile approach to fabricate a novel bio-based hybrid (BBH) with core/shell structure is presented by taking advantage of plant-derived resources. The BBH developed herein comprises of an inorganic core of ammonium polyphosphate (APP), covered with an organic shell that is constructed via layer-by-layer assembly of a novel bio-based polyelectrolyte (BPE) and polyethylenimine (PEI). BBH can simultaneously enhance the flame retardancy and toughness of polylactic acid (PLA) with very high efficiency. The flame retardant PLA composite can pass UL94 V0 rating at the BBH loading content of 10 wt%. The efficient flame retardant performance is due to its effectiveness in both gas and condensed phases. More importantly, the flame retardant PLA composite containing 10 wt% BBH exhibits ductile fracture with an elongation at break of 27.3%, which is much higher than that of neat PLA (8%). The debonding and plastic void deformation of the PLA matrix around the BBH are responsible for the enhanced toughness. This work provides important hints for devising highly efficient multifunctional flame retardant and broadening the application field of renewable resources.