Abstract: An intumescent flame retardant was synthesized from phosphorus oxychloride, bisphenol A, and melamine via two steps. The suitable synthesis conditions were found as follows: in the first step, the molar ratio of phosphorus oxychloride/bisphenol A was 2.2, the reaction temperature was 70 ℃, and the reaction time was 5 h; in the second step, the molar ratio of intermediate product/melamine was 1/2，the reaction temperature was 100 ℃, and the reaction time was 3 h；the yield of the products reached 87.6 %. When 15 % intumescent flame retardant with 5 % ammonium polyphosphate were introduced into polypropylene, the obtained oxygen index was 33 %, and the vertical combustion performance reached V-0 level.

Key words: polypropylene, bisphend A, phosphorus oxychloride, melamine, synthesis, intumescent flame retardant, limiting oxygen index