Influence of carbon nanoparticle geometry on the fire resistance and anti-aging properties of intumescent fire-retardant coatings

Three types of carbon nanoparticles, namely layered graphene (GN), tubular carbon nanotubes (CNTs), and spherical carbon black (CB), were applied in the intumescent fire-retardant coatings. The influence of carbon nanoparticle geometry on the fire-resistant and anti-aging properties of the intumescent coatings was investigated. The fire protection and smoke density tests show that both spherical CB and tubular CNTs can effectively improve the fire resistance and smoke suppression properties of the coatings, which is attributed to the fact that the addition of either CB or CNTs can promote the swelling process of coating and produce a positive effect on improving the compactness and thickness of char residues. Especially, the coating containing 0.1 wt% CB acquires the lowest flame spread rating (FSR) value of 6.5, smoke density rating (SDR) value of 17.6%, and equilibrium backside temperature of 169.2 degrees C at 900 seconds, showing superior fire resistance and smoke suppression performance. However, the layered GN shows a negative effect on the fire resistance and smoke suppression properties of the coating, which is ascribed to the fact that GN platelets inhibit the intumescent process of coating, resulting in the decrease of barrier effect. The results of accelerated aging test show that the incorporation of either CNTs or CB can weaken the blistering and powdering phenomenon, thus imparting superior durability of integrity and fire resistance to the intumescent coatings.