Flame Retardancy of Rigid Polyurethane Foam According to Particle Size and Expansion Rate of Expandable Graphite

In order to improve the flame retardancy of the rigid polyurethane foam, expandable graphite having different particle sizes and expansion rates was added to synthesize a rigid polyurethane foam. Urethane and isocyanurate ring was confirmed using fourier transform infrared spectroscopy (FTIR), and the heat resistance of the foam was analyzed using thermogravimetric analysis (TGA). The effect of expandable graphite on the mechanical properties of polyurethane foam was confirmed by measuring the compressive strength. The flame retardancy was analyzed through the UL94 V test, limited oxygen index (LOI), and measurement of the weight loss due to combustion. Although expandable graphite did not affect the compressive strength and heat resistance of polyurethane foam, in the flame retardant test, it was confirmed that the volume of char produced increased as the particle size and expansion rate of expandable graphite increased. Thus the flame retardant performance was improved.