Self-assembly of zinc hydroxystannate on polyethyleneimine supported boron nitride to improve the flame protection properties of waterborne epoxy coatings

Abstract

Herein, polyethyleneimine (PEI) was loaded on the surface of BN nanosheets to impart them a positive charge. Then, negatively charged zinc hydroxystannate (ZHS) nanoparticles were adsorbed on the surface of BN/PEI composites through electrostatic self-assembly to obtain a novel BN/PEI@ZHS nanoadditive (BP@ZHS). The contribution of BP@ZHS hybrids to the flame retardant properties of epoxy coatings (EP) was characterized by fire performance tests. The thermal insulation performance test results showed that the backside temperature of the BP@ZHS based epoxy (BP@ZHS/EP) fireproof coating remained the lowest value (172.1 ℃) after 60 min of burning. The BP@ZHS/EP sample exhibited the most excellent expansion characteristics (expansion height is 21.5 mm, expansion rate is 16.54) after calcination in a muffle furnace. The TGA experiments illustrated that BP@ZHS/EP had the largest amount (30.8%) of carbon residue due to its catalytic carbonization. Moreover, the smoke density rating (SDR, 46.8%) of BP@ZHS/EP was significantly lower than other samples due to the synergistic effect of BN and ZHS. The carbon residue analysis showed that zinc stannate and BN remained in the carbon framework, thereby improving the strength and thermal insulation effect of the char layer. The excellent fire resistance of BP@ZHS/EP can be mainly attributed to the high barrier effect of BN nanosheets and the multifunctional flame retardant effect of ZHS.