Flame retardants for polypropylene based on lignin

Lignin has been investigated as flame retardant for isotactic polypropylene (PP) by means of thermogravimetric analysis in nitrogen and cone calorimetry with incident heat flux exposure at 25 kW/m 2. Lignin has been used in synergism with aluminium hydroxide, poly(vinyl alcohol), melamine phosphate, monoammonium phosphate and ammonium polyphosphate. These flame retardants, based on lignin, increase the thermal degradation temperature, the combustion time and the char yield of PP, and decrease the rate of heat release and the weight loss rate during combustion. Dynamic mechanical analysis shows that lignin addition does not reduce elastic modulus E′ of PP/lignin blends in the range from 30 to 100 °C in comparison with pure PP until 15% of lignin addition.