Flame retardant properties of waterborne epoxy intumescent coatings reinforced by polydopamine@KH560/carbon nitride/graphene ternary system

Abstract Firstly, the bio-inspired polydopamine (PDA) was coated on the surface of carbon nitride (CN), then used it (CNP) as nano-dispersant to improve the dispersion of graphene (Gr) in water on the basis of π-π interaction. After that, the KH560 was further grafted on the CNPG surface to improve the compatibility between inorganic hybrids and epoxy resin. The results of large plate experiments showed that the backside temperature of composite IFR coating containing CNPG@Si hybrids was significantly lower than that of other samples. Meanwhile, its expansion height after furnace test reached the maximum value (17.8 mm), which was greatly improved compared with the pure epoxy coating. Further, the maximum thermal decomposition temperature and the amount of char residue for the CNPG@Si/EP sample were significantly enhanced through the TGA test result. Besides, CNPG@Si based sample showed the lowest smoke density rating (SDR) due to its excellent smoke suppression performance. From the analysis of the morphology and composition of the char layer for CNPG@Si based sample, it can be seen that the introduction of Gr and CN increased the compactness of the char layer, and silicon network structures remained in the char layer after combustion, which effectively increases its strength and heat insulation effect.