Ammonium polyphosphate wrapped carbon microspheres: a novel flame retardant with smoke suppression for poly (ethylene terephthalate)

A new type of three-in-one flame retardant (CA) was first constructed by using ammonium polyphosphate (APP) as a shell material wrapped on carbon microspheres (CMSs) for flame retardant poly (ethylene terephthalate) (PET). CA was further modified by 3-Methacryloxypropyltrimethoxysilane (γ-MPS) to improve the hygroscopicity of APP and improve its compatibility with the PET matrix. The results showed that, compared to PET, the thermal stability and flame retardancy of CA/PET composites were significantly improved. Similarly, the tensile strength of CA/PET composites were greatly improved compared to CMSs/PET and APP/PET composites. In the flammability test, when the ratio of CMSs to APP in CA was 1:2, the peak heat release rate (PHRR) and total smoke production (TSP) decreased by 71.4% and 18.8%, respectively. Meanwhile, the limiting oxygen index (LOI) of CA2/PET increased to 28.6%, and reached V-0 rating in the vertical burning test (UL-94). Overall, CA endowed CA/PET composites with efficient flame retardancy and smoke suppression, providing enough escape possibilities for people in the real fire.