Flame-retardant-wrapped carbon nanotubes for simultaneously improving the flame retardancy and mechanical properties of polypropylene

Covalently functionalized carbon nanotubes (CNTs) wrapped in intumescent flame retardant were successfully fabricated and characterized. By adjusting the ratio of CNTs and flame retardant, the diameter of the functionalized CNTs was effectively controlled to 20-90 nm. Compared with pristine CNTs, the functionalized CNTs are better dispersed in polypropylene (PP) due to the in situ compatibilization reaction between the active groups of the intumescent flame retardant on the CNT surface and the maleic anhydride groups in the compatibilizer, maleic anhydride-grafted polypropylene (PPMA). Incorporating the functionalized CNTs could confer outstanding flame retardancy on PP/PPMA, and considerably enhance the mechanical properties of the polymeric materials due to the improved interfacial adhesion and stress transfer. Therefore, use of intumescent flame-retardantwrapped carbon nanotubes and in situ compatibilization are promising strategies for simultaneously improving the flame retardancy and mechanical properties of polymeric materials.