Synthesis of a novel multi-structure synergistic POSS-GO-DOPO ternary graft flame retardant and its application in polypropylene

Through reaction of the active functional groups on framework of Graphene oxide (GO) with 9, 10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO) and cage octaminopropyl silsesquioxane (oapPOSS), a novel multi-structure synergistic graphene-based ternary graft flame retardant oapPOSS-graft-GO-graft-DOPO (P-G-D) was designed and synthesized successfully. The obtained P-G-D was then applied in PP flame retardation. Compared with pure PP, the peak heat release rate and total heat release of PP composite are reduced by 78.0% and 44.9% via adding 25 wt% P-G-D. These notable reductions in fire hazards are mainly due to the synergistic effects of graphene/nitrogen/phosphorus/silicon multi-structures: the graphene sheets enhance the barrier property of carbon layers to prevent heat and volatile transfer; the phosphorus-containing groups as catalyst accelerate and promote the char formation in condensed phase; the Si-O-Si structures improve the thermal oxidative stability; the nitrogen elements in P-G-D produce the inert gases at high temperature and play a major role in the gaseous phase.