Zinc hydroxystannate anchored PAP-activated carbon spheres for enhancing flame protection of aqueous epoxy coatings

Abstract

Here, carbon spheres (CS), a carbonaceous spherical material with a wide source and easy preparation, were used as enhanced nano-fillers to reinforce the flame retardancy of aqueous epoxy intumescent coatings. To overcome the defects of CS themselves during combustion, polydopamine (PDA) was co-deposited with adenosine triphosphate (ATP) on its surface to obtain activated carbon spheres with C-N-P structure (CS/PAP), which can contribute to the formation of intumescent char layer. Meanwhile, zinc hydroxystannate (ZHS), as a non-halogen, environmentally friendly, and efficient flame retardant, was introduced to the surface of carbon phosphide spheres to obtain a composite functional hybrid reinforcement (CS/PAP@ZHS). Adiabatic performance tests indicated that the backside temperature of the CS/PAP@ZHS filler-reinforced EP expansion specimen was maintained at the minimum fig. (168.8 °C), confirming its highest resistance to heat penetration. Compared to the CS-based EP, the CS/PAP-loaded EP showed reduced smoke emission, indicating the effectiveness of the PAP intumescent phosphate modification for smoke suppression. By comparison, the CS/PAP@ZHS-based EP showed the largest char residue (29.1 % in N2, 12 % in air), expansion height (23.1 mm), and minimal smoke density grade (40.7 %). Additionally, compared with pure EP, the peak heat release rate (PHRR), total heat release rate (THR), peak smoke production rate (PSPR), and total smoke production (TSP) of CS/PAP@ZHS/EP are reduced by 33.3 %, 28.2 %, 37.4 %, and 23.6 % respectively, demonstrating its best fire and smoke suppression properties.