Abstract: In this paper, a flame retardant system consisting of P-N intumescent flame retardant (IFR), ammonium polyphosphate (APP) and zinc oxide (ZnO) was applied to low-density polyethylene (PE-LD). SEM was used to analyze the structure of the carbon layer after burning. The components of carbon layer of the sample, obtained from different thermal treatment had been analyzed using Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy and the flame mechanism of the PE-LD/IFR/APP/ZnO system was studied. The PE-LD/IFR/APP/ZnO system reached a limiting oxygen index value of 27.9 % and UL 94 V-0 level.

Key words: low-density polyethylene, P-N halogen-free intumescent flame retardant, flame retardancy mechanism