Abstract: Hex (dodecylamino) cyclotriphosphazene (HDCP) and Hex (Octylamino) cyclotriphosphazene (HOCP) were synthesized by nucleophilic substitution reaction, then the two were introduced into polypropylene (PP), in which ammonium polyphosphate (APP) and pentaerythritol (PER) were also present. The flame retardancy of systems was measured bylimiting oxygen index (LOI), UL94, and cone calorimetry(CCT).The mechanical properties of flameretarded PP were studied including elongation at break,tensile and impact strengths.It showed that the LOI of flameretarded PP increased about 13 % when 2 % phosphazene derivative were introduced. With increasing HDCP and HOCP，the impact strength of flameretarded PP was improved, however, the elongation at break was decreased.

Key words: polypropylene, hexcyclotriphosphazene, nucleophilic substitution reaction, flame retardant, mechanical property