The Synergistic Effect of Transition Metal Nitrate in Polypropylene/Magnesium Hydroxide Flame Retarded Composite

Abstract

AbstractThe transition metal lanthanum nitrate is introduced to the surface of magnesium hydroxide (MH) through the incipient wetness impregnation method, and the modified MH particles are compounded with polypropylene (PP) to prepare PP/MH flame retarded (FR) composite. The results show that the introduced lanthanum nitrate shows a remarkably synergistic effect on MH in flame retardancy of PP. Compared with the unmodified MH‐filled PP FR system, the introduction of only 0.2 wt% La ions can remarkably enhance the limiting oxygen index value from 29.6 to 34.2 and the UL‐94 level from failure to V‐0, respectively. The cone calorimeter (CONE) parameter peak heat release rate is also obviously reduced from 187 to 155 kW m−2. The reason for the remarkable improvement in the flame retardancy is that the introduced lanthanum nitrate improves the thermal stability, the char yield, and particularly the quality of the condensed charred layers of the FR PP/MH material significantly. The involved synergistically flame‐retarding mechanism of lanthanum nitrate exists in its excellent catalytic carbonization effect on the PP macromolecular chains.