Effects of a phosphorus-nitrogen containing DOPO derivative on the flame retardancy and mechanical properties of polylactic acid foamed materials

• A DOPO-based phosphorus-nitrogen flame retardant was synthesized. • Flame retardancy and mechanical properties improved by DOPO-DABP and ammonium polyphosphate(APP). • Polylactic acid foamed materials were flame retardant modified by DOPO and APP. • Foamed material has dense cell structure after flame retardant modification. In this study, a phosphorus-nitrogen flame retardant (DOPO-DABP) was synthesized by 9,10-Dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO) and 4,4′-diaminobenzophenone (DABP). Then, polylactic acid (PLA), polybutylene adipate terephthalate (PBAT), ammonium polyphosphate (APP), DOPO-DABP, Joncryl ADR-4370F(ADR), azodicarbonamide (ADC) and nano-SiO 2 were used as raw materials to prepare flame-retardant modified PLA foamed materials by hot pressing. The synergistic effect of APP and DOPO-DABP not only effectively improves the flame retardancy of PLA foamed material, but also promotes their mechanical properties. The experimental results showed that when APP/DOPO-DABP=10/10, the vertical combustion grade (UL-94) of the material reached the V-0 level, the limiting oxygen index (LOI) was 34.4 %. The tensile strength of the material was 25.35 MPa, bending strength was 32.14 MPa. The cell diameter of the material was reduced to 46.72 μm, and the cell density of the material was 2.25×10 6 /cm 3 .