Abstract: An intumescent flame-retardant was prepared by compounding 1,3,5-tri(5,5-dimethyl-1,3-dioxacyclophosphorinane phosphonate) benzene (FR), ammonium polyphosphate (APP), and nano-silica, and used in polypropylene(PP). Testing through limiting oxygen index, horizontal burning test, thermo gravimetric analysis (TG), and cone calorimeter showed that the compound flame-retardant increased the limiting oxygen index, horizontal burning rate, thermal stability, and residual char, and decreased the heat release rate. When the weight ratios of FR/APP/SiO2 were 15/7/3 and its content was 25 %, limiting oxygen index of 29.4 % and horizontal burning rate of FH-1 were obtained.

Key words: composites, polypropylene, intumescent flame retardant, nano-silca, flame retardancy