Abstract: The flame retardant modification of High Density Polyethylene（HDPE）was made by filling with ammonium polyphosphate（APP）,prepared in different APP content of composite materials. The flame retardant effects of APP on the prepared composite were studied by means of limiting oxygen index (LOI) and horizontal-vertical burning .The test methods of thermogravimetric analysis (TGA) and the overall stabilization effect (OSE) were applied to measure the thermal stability, analysed the relation between thermal stability and flame retardant . The results indicated that the measure of OSE can commendably measure the overall thermal stability of composite. And the addition of suitable content of APP not only improved the flame retardant of the composite, but also advanced the thermal stability. Enhancing the overall thermal stability of HDPE fire-retardant composite can improve its flame retardant.

Key words: ammonium polyphosphate, high density polyethylene, flame retardant, thermal stability