Mussel inspired polydopamine@KH560-linked hexagonal boron nitride and CNTs nanoflame retardants improve fire performance of composite coatings

Herein, the excellent properties of one dimension (1D) and two dimension (2D) nanoparticles were fully combined to enhance the thermal stability and flame retardancy of waterborne epoxy intumescent fire retardant (IFR) coatings. Specifically, layered hexagonal boron nitride (h-BN) nanosheet-linked acidified carbon nanotubes (CNTs) hybrids (BP@Si/CNTs) were prepared using polydopamine (PDA) and γ-(2,3-epoxypropoxy)propytrimethoxysilane (KH560) as bridging agents. The results of the fire test, furnace test and thermogravimetric analysis indicated that the incorporation of 2 wt% of BP@Si/CNTs hybrids in the IFR coating significantly improved the thermal stability and flame retardancy of the char layer. The backside temperature of the BP@Si/CNTs 2.0% /EP sample decreased by 89.3 °C, the expansion rate increased by 11.53, and the residual char increased by 11.05 wt% compared to the control EP. The potential flame retardant mechanism was investigated by residual char analysis. The mechanism investigations indicated that the improved fire resistance of the composite coatings is attributed to the enhancement of the char layer by the physical barrier effect of the h-BN nanosheets and the "skeletal framework" effect of the CNTs during the combustion process.