Effect of Bi₂O₃ on flame retardancy and properties of PP

The effect of Bi₂O₃ on flame retardant synergism of ammonium polyphodphate (APP)/D-pentaerythrito (DPER)/polypropylene (PP) intumescent flame retardant system was studied. Influence of Bi₂O₃ on intumescent flame retardancy PP was analyzed by limiting oxygen index, smoke density and thermogravimetry analysis. The result shows that Bi₂O₃ promotes APP residual quantities and increases the thermal stability of the system. Moreover, the law of the effect of Bi₂O₃ was also researched. The limiting oxygen index (LOI) values at first increase with amount of Bi₂O₃ until a maximum in LOI is reached. With further increase in the Bi₂O₃ concentration the LOI begins to decrease. The highest LOI value obtained in this experiment is 25.2 with amount of 0.1% Bi₂O₃.