Phytic acid cross-linked copper ions anchored to BN surface to enhance the fire performance of waterborne epoxy intumescent coatings

It is obvious that boron nitride (BN) can provide excellent barrier to heat and flame due to its large lamellar structure and high thermal stability. Here, we combined the barrier effect of BN with the catalytic effect of transition metal ions to obtain a novel nanocomposite coating. Specifically, polyethyleneimine (PEI) molecules were loaded on the BN surface by Lewis acid-base action. Then, the phytic acid (PA) molecules were self-assembled on the PEI surface by electrostatic action. Finally, copper ions (Cu2+) were complexed in the PA molecules to obtain BN/PPA@Cu hybrids. The fire performance and smoke suppression effects of BN/PPA@Cu loaded epoxy resin (EP) composite coatings were discussed and analyzed by large plate experiments, thermal weight loss analysis, etc. In comparison, the backside temperature of the steel plate with BN/PPA@Cu/EP composite coating was stabilized at 167.8 °C, which was significantly lower than other samples, while its lowest smoke density rating (39.9) confirmed its excellent smoke suppression effect. The results of thermal weight loss analysis proved that BN/PPA@Cu/EP had the lowest Tmax (334.8 °C), which was a direct response to the catalytic effect of transition metal ions. Additionally, the highest char residue (31.1%) and the maximum expansion height (21.9 mm) of BN/PPA@Cu/EP conferred high fire resistance and smoke suppression to the composite coating. These findings are a good reference for obtaining high performance fireproof coatings.