Flame retardancy of microcapsulated caged-phosphate with ammonium polyphosphate in polypropylene

A novel microcapsulated caged-phosphate (ET) was compounded with ammonium polyphosphate (APP) to flame retard polypropylene (PP). The flame retardancy of the flame retardant PP were evaluated by limiting oxygen index (LOI) and UL 94 test, and the synergistic effect and flame retardant mechanism were studied by thermogravimetric (TG) analysis, scanning electron microscopy (SEM), Fourier transmission infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS). The results indicate that there is good synergistic effect between ET and APP. Moreover, the flame retardancy of ET/APP varies with their mass ratio. And the optimal flame retardancy can be obtained when the mass ratio of ET to APP is 1:2. When the mass content of ET/APP is 30%, LOI of the flame retardant PP reaches 29.7%, and UL 94 V-0 rating can be achieved.