The influence of nano ZnO coated by phosphazene/triazine bi-group molecular on the flame retardant property and mechanical property of intumescent flame retardant poly (lactic acid) composites

Nano zinc oxide (nano ZnO) and phosphazene/triazine bi-group flame retardant in situ doping nano zinc oxide (A4-d-ZnO) were used as synergists in intumescent flame retardant poly (lactic acid) (PLA) composites, respectively. The results showed that nano ZnO endowed flame retardant PLA excellent flame retardant properties, such as the higher LOI value, the lower pk-HRR, av-HRR, THR, mass loss rate, TSR and more final mass than A4-d-ZnO. It was because that nano ZnO catalyzed PLA decomposed into low molecular segments, which acted as a char-forming agent. However, it destroyed the mechanical properties seriously. By contrast, although the flame retardant properties of PLA/IFR/A4-d-ZnO was not better than PLA/IFR/nano ZnO, owing to the weakened catalytic effect of A4-d-ZnO coated by the phosphazene/triazine bi-group flame retardant, A4-d-ZnO improved the flame retardant properties, the thermal stability and the mechanical properties at the same time, which was important and necessary for application.