Is there any way to simultaneously enhance both the flame retardancy and toughness of polylactic acid?

Nowadays, numerous works have been undertaken to improve the fire resistance of polylactic acid (PLA). However, the presence of flame retardant usually shows a great destruction on the mechanical properties of PLA matrix, especially the toughness. This paper presents a new approach to simultaneously enhance both the flame retardancy and toughness of PLA by incorporating polyurethane‐microencapsulated ammonium polyphosphate (MCAPP). The prepared MCAPP was blended with PLA by melt compounding to prepare PLA/MCAPP composites. The results indicated that the introduction of 15% MCAPP increased the limiting oxygen index of PLA composites from 19.3% to 28.3%, upgraded the UL‐94 rating from no rating to V‐0, and decreased the peak heat release rate from 464.2 to 332.2 kW/m². Even though the tensile strength of PLA composites was decreased to 53.8 MPa, the toughness was significantly improved, with elongation at break lengthened to 40.8% and notched impact strength increased to 2.95 kJ/m². The possible mechanisms for both flame retardancy and toughness were also discussed. POLYM. COMPOS., 40:932–941, 2019. © 2018 Society of Plastics Engineers