Flame-retardant behavior of bi-group molecule derived from phosphaphenanthrene and triazine groups on polylactic acid

Abstract

The flame-retardant polylactic acid (PLA) has been prepared via mixing the flame retardant TGIC-DOPO derived from phosphaphenanthrene and triazine groups into matrix. The flame retardancy of TGIC-DOPO/PLA composites was characterized using the limiting oxygen index (LOI), vertical burning test (UL94), and cone calorimeter test. Results reveal that the 10%TGIC-DOPO/PLA composite obtained 26.1% of LOI and passed UL94 V-0 rating. The flame-retardant mechanism of PLA composites was characterized via thermogravimetric analysis (TGA), pyrolysis gas chromatography/mass spectroscopy, and TGA-Fourier transform infrared. It discloses that TGIC-DOPO promoted PLA decomposing and dripping early, and it also released the fragments with quenching and dilution effects. These actions of TGIC-DOPO contribute to reducing the burning intensity and extinguishing the fire on droplets, thus imposing better flame retardancy to PLA. When TGIC-DOPO was partly replaced by melamine cyanuric with dilution effect and hexa-phenoxy-cyclotriphosphazene with quenching effect in composites respectively, the results confirm that TGIC-DOPO utilize well-combination in dilution effect and quenching effect to flame retard PLA.