Surface feature of ammonium polyphosphate is modified by cation exchange reaction with piperazine, and then reduced graphene oxide nanosheets are attached to the surface of modified flame retardant via hydrogen bonding interactions. Good dispersion of graphene in the polypropylene matrix is observed. The dispersion state of graphene has an abnormal effect on the flammability results under small flame and fire behavior under forced flaming condition of intumescent flame retardant (IFR) composites. The well-dispersed graphene results in significantly deteriorated limiting oxygen index and UL-94 rating. The graphene with good dispersion is adverse to flammability results, which is in contrary to the widely-acknowledged flame retardant mechanisms. Low content of well-dispersed graphene exhibits higher reduction effect on heat release than that of poorly-dispersed counterpart. Novel flame retardant mechanism and model are proposed and new understanding of the role of graphene in the combustion of IFR is provided.

通过与哌嗪的阳离子交换反应来修饰多磷酸铵的表面特征，然后通过氢键相互作用将还原的氧化石墨烯纳米片附着到改性阻燃剂的表面上。观察到石墨烯在聚丙烯基质中的良好分散。石墨烯的分散状态对在小火焰下的可燃性结果有异常影响，并且在膨胀型阻燃剂（IFR）复合材料的强制燃烧条件下具有着火行为。分散良好的石墨烯会导致极限氧指数和UL-94等级显着降低。具有良好分散性的石墨烯不利于可燃性结果，这与公认的阻燃机理相反。与分散较差的石墨烯相比，分散度低的石墨烯对放热的还原作用更高。提出了新型的阻燃机理和模型，并对石墨烯在IFR燃烧中的作用有了新的认识。