Toward a new approach to synchronously improve the fire performance and toughness of polylactic acid by the incorporation of facilely synthesized ammonium polyphosphate derivatives

Abstract Polylactic acid (PLA) with eco-friendliness exhibits extensive potential applications. In order to enhance fire-resistance of PLA, this manuscript reports the preparation of boron-containing ammonium polyphosphate (B-APP) using 3-aminophenyl boronic acid and ammonium polyphosphate through ion exchange reaction, and incorporated into PLA matrix. The limiting oxygen index (LOI) of PLA-5% B-APP was increased from 19.2% to 29.4% and a UL-94 V-0 rating. In the cone calorimeter tests, PLA-5% B-APP presented a total heat release (THR) reduction from 81 MJ·m−2 to 67 MJ·m−2 and an improvement from 1.6% to 6.7% in char residue comparing with PLA. The mechanism of B-APP was mainly ascribed to the formation of glassy char layers to block the heat and oxygen transfer. For mechanical properties, it could be also found that the elongation at break and impact strength were improved at the presence of 5% B-APP.