A NEW SYNERGIST FOR INTUMESCENT FLAME RETARDANT POLYPROPYLENE

The synergistic effects of silicotungstic acid (SiW;) as a carelyst in the phosphorus-nitrogen compounds AM-based intumescent flame-retardant （IFR） polypropylene （PP） were studied using the limiting oxygen index（LOI）, the UL-94test, thermogravimetric analysis （TGA）, real time Fourier transform infrared （FTIR）, laser Raman spectroscopy （LRS）. TheLOI data show that SiW;added to PP/IFR systems has a synergistic FR effect with an IFR additive named AM. The TGAdata show that SiW;apparently increases the thermal stability of the PP/IFR systems at high temperature （T>500℃）. TheFTIR results provide the positive evidence that IFR can improve the thermal stability of PP and SiW;can induce a higherrate of formation of phosphoric acid and its derivatives. The LRS measurements provide useful information on thecarbonaceous microstructures. In short, a suitable amount of SiW;（1.5 wt%） exerts synergistic effects with the IFR byincreasing the LOI value and the thermal stability at high temperature and promoting the formation of charred structures onthe burning PP surface.