Synergistic effect of different nanoparticles on flame retardant poly(lactic acid) with bridged DOPO derivative

This study aimed to examine synergistic effect of nanoparticles including nano silica (SiO₂), organic montmorillonite (OMMT) and zinc borate (ZnB) on flame retardant poly(lactic acid) (PLA) composites containing a phenethyl‐bridged 9,10‐dihydro‐9‐oxa‐10‐phosphaphenanthrene‐10‐oxide derivative (DiDOPO). 2% was the optimal addition content for these nanoparticles in PLA/DiDOPO composites, and nano SiO₂ showed higher limiting oxygen index value (27.0%) than OMMT (25.8%) and ZnB (26.5%) at the same content. When compared with that of PLA/DiDOPO, the peak heat release rate was decreased dramatically after introducing nanoparticles, and the smoke was significant suppressed by adding SiO₂. Among these nanoparticles, SiO₂ had an obvious enhancement in the thermal stabilities of PLA composites both under nitrogen and air conditions resulting from its barrier effect. Moreover, a compact char was formed after combustion for PLA/DiDOPO/SiO₂. In addition, high‐resolution electron microscope and rheology results showed that SiO₂ had a well dispersive quality in PLA/DiDOPO composites. Consequently, SiO₂ shows the best synergistic effect with DiDOPO toward improving the flame retardancy of PLA. POLYM. COMPOS., 40:1043–1052, 2019. © 2018 Society of Plastics Engineers