Abstract: The effect of various phosphorus flame retardants on the flame-retarded performance, mechanical properties, and heat resistance of PPO/PS-HI alloy was investigated. It was found that red phosphorus was better than organic phosphate in flame retardancy. At the loading meet the flame-retarded grades（UL 94 V-0）, organic phosphate flame retardant would greatly reduce the heat resistance, and red phosphorus was harmful to the toughness.

Key words: poly(phenylene oxide), high impact polystyrene, phosphorus flame retardant, mechanical property, heat resistance, flame retardancy