Green vanillin coupled with P/N/Si flame retardant for poly (L-lactic acid)

To better solve the flammability of poly (l-lactic acid) (PLLA) and meet environmental concerns, developing bio-derived flame retardants for PLLA is an alternative method. A green flame retardant (VKD) was synthesized in the work. Vanillin was modified using 3-amino-propyl-triethoxysilane (KH550) prior to coupling with 9, 10-dihydro-9-oxa-10-phosphafi-10-oxide (DOPO). As the blend ratio of VKD to PLLA was 20 wt%, the limiting oxygen index (LOI) and UL-94 were 25.5% and V-0 rating, respectively; and the residual carbon rate reached 9.14% at 600 °C, which was 3.3 times higher than that of PLLA. In the cone calorimetry test, the peak heat release rate (pHRR) and total heat released (THR) reduced by 9.9% and 20.5%, respectively, and total smoke production (TSP) decreased by 26.8%, indicating that VKD/PLLA had good flame retardancy and smoke suppression properties. It was mainly attributed to initial condensation phase obstacle and following combination of gaseous phase quenching and carbon/silicon composite barrier. The VKD/PLLA maintained balanceable mechanical properties and good degradation. Then green VKD would broaden PLLA in the application of engineering such as electronic products and automotive interior materials.