Improving the flammability and flame retardant properties of polyurethane foam by adding lignin

Currently, polyurethane foam is highly flammable. This research was aimed to improve the flammability and flame retardant properties of polyurethane foam by adding various amounts of lignin which was synthesized from para rubber wood using organosolv fractionization method. The polyurethane foam was mixed with 0, 5, 10 and 15% by volume of lignin and PU foam composites were formed by casting. From the flammability testing, it was found that polyurethane foam mixed with 10% lignin by volume showed good flammability properties. In addition, the thermal properties test by TGA technique showed that increasing the lignin content made the polyurethane foam more thermally stable. Therefore, the addition of lignin resulted in a slight increase in the maximum decomposition temperature of polyurethane foam. In addition, the fire-retardant test showed that the polyurethane foam without lignin addition was completely burned without ash, however droplets of molten polymer were observed. While 5, 10 and 15% of lignin addition to the polyurethane foam retained post-combustion ash and no droplet of molten polymer was observed. Hence, addition of lignin could enhance the flammability and flame retardant properties of polyurethane foam composite.