Ammonium polyphosphate was prepared and used as flame retardant materials for polypropylene nanocomposites. Then, kaolin was incorporated with ammonium polyphosphate nanoparticles as synergistic flame retardant system for polypropylene. This is in addition to modification of kaolin with sulfuric acid then incorporated with polyphosphate nanoparticles as good flame retardant materials for polyproplylene. Flammability properties of polymer developed polymer nanocomposites were improved achieving 26.4 and 10.2 % reduction in peak heat release rate (PHRR) compared to virgin polymer and polymer composite with ammonium polyphosphate nanoparticles alone. The synergistic effect of modified kaolin and nanoparticles was evaluated. The dispersion of ammonium polyphosphate and kaolin in polymer matrix were studied using microscopic techniques.