Abstract: This paper studied the synergism effect between IFR and metallic compounds.The flame retardancy, thermal stability and the char layer were analyzed by LOI, DSC-TG and SEM.The synergism effect mechanism of metallic compounds was discussed.The LOI results show that, when the composition contained 3%ZEO, 1% ZnO and 3% Al2O3, LOI of 29.6, 29.0 and 29.4 were achieved. It was higher 4.6, 4.0 and 4.4 than IFR separately.The DSC-TG and SEM results indicate that ZEO, ZnO and Al2O3 can help the PE-HD/IFR to accelerate the formation of charring layer and strengthen it.But there is little contribution to the quality of the charring layer.

Key words: HDPE, metallic compounds, intumescent flame retardant, synergism effect, mechanism