Abstract: Halogen-free flame-retarded PP composites were prepared by mixing polypropylene(PP) with melamine cyanurate(MCA) and ammonium polyphosphate（APP）. The flame-retarding property, thermo property, and mechanical property were characterized using limited oxygen index, thermo gravimetric analyzer, scanning electron microscope, and electronic tensile testing machine. The synergic flame-retarding effect of APP/MCA and its effect on the mechanical properties of PP were discussed. It was found that when the content of APP/MCA was 25 phr, the limited oxygen index and the mechanical properties of PP composites increased firstly and then decreased with increasing content of MCA. When the content of MCA in APP/MCA was 30 % , the limited oxygen index of the composite reached the highest value of 24.2 %, and its tensile strength increased 50 %, its breaking strength and yield strength also increased more than 10 %, compared with the composite flame-retarded by 25 phr APP.

Key words: melamine cyanuric, ammonium polyphosphate, polypropylene, reinforcement, fire-retarding