Abstract: A novel intumescent flame retardant (IFR) was composed by ammonium polyphosphate (APP) and novel charring agent (CNCH-DA), and the influence of CNCH-DA on the flame retardancy of PE-LD was investigated by limited oxygen index, vertical test, microscale combustion colorimeter, thermogravimetric analysis and scanning electron microscopy. It was found that the limited oxygen index of the PE-LD composites was 27.5 % with UL 94 V-0 rating when the mass ratio of APP to CNCH-DA was 5:1. The heat release rate and total heat release measured by MCC decreased remarkably. The composites decomposed at higher temperature when APP and CNCH-DA were composed together. An intumescent and compact char layer was formed for PE-LD/IFR composite with excellent flame retardant properties, while lots of small balls were formed for PE-LD/CNCH-DA with poor barrier properties.

Key words: low density polyethylene, novel charring agent, intumescent flame retardant, synergism