Abstract: A novel flame retardant （TDK） containing nitrogen， phosphorus， and silicon elemetns was synthesized by using 9，10-dihydro-9-oxa-10-phosphoxanthophosphor-10-oxide （DOPO）， 1，3，5-three glycidyl different melamine urea acid ester， and gamma-ammonia ethyl ammonium propyl silane as raw materails. The resultant TDK was blended with ammonium polyphosphate （APP） and melamine pyrophosphate （MPP） to prepare intumescent-flame-retardant polypropylene， and its performance was compared with the traditional intumescent-flame-retardant PP/APP/MPP/dipentaerythritol （Di-PE） composite. The structure and composition of TDK were verified by FTIR， 31P solid-state NMR， and elemental analysis. Thermogravimetric analysis indicated that PP began to degrade at 329.0 ℃ when 30 phr of IFR was added. On the other hand， the carbonization reaction of the PP/APP/MPP/TDK composite was earlier than that of PP matrix， and its decomposition temperature was 273.8 ℃. Moreover， the carbon residue rate of the PP/APP/MPP/TDK composite was 13.8 % higher than that of pure PP. In addition， the PP/APP/MPP/TDK composite presented a limiting oxygen index of 30.5 wt%， and its flame retardant classification reached V-0 level classification in the vertical combustion. Its heat release rate was reduced by 86 %， its smoke production rate was reduced by 78.8 %， and its mechanical properties were better than those of the PP/APP/MPP/Di-PE composite. The flame retardant performance and corresponding mechanism of the developed composite were further analyzed by using scanning electron microscopy， infrared spectroscopy， and energy dispersion spectroscopy. The results indicated that there was a synergistic effect of phosphorus， nitrogen and silicon on the flame retardancy of PP in the condensed phase.

Key words: polypropylene, intumescent flame retardant, synthesis, halogen-free, smoke suppression