Abstract: Polyamide 6 was introduced into PP/MAPP system as a synergetic char agent. When MAPP/PA6(w/w）=25/3, the intumescent degree and char yield of were 180.23㎝3/g and 72.11％, respectively, which contracted to 78.6㎝3/g and 61.96％when MAPP was used alone. The thermal analysis indicated that at low temperature zone, the weight loss of PP/MAPP/PA6 decreased and char yield increased obviously. However, at high temperature zone, the char degradation was accelerated, more flammable substance were formed that release more heat through burning. So the loading of PA6 should be appropriate. When PP/MAPP/ EPP/PA6(w/w/w/w) =75/25/7/3, its oxygen index was 34.7, the self -extinguishing time was 16s in horizon test, and the mechanical strength was 28.89 MPa.

Key words: microencapsulation ammonium polyphosphate, polyamide 6, Char agent, Synergetic, flame-retardant polypropylene