The mineral synergist, zirconium nitride, reduced smoke production by 40% and improved performance of a PIN APP-melamine epoxy intumescent fire coating for steel. The intumescent coating, typical of PIN formulations used to protect steel and other materials in fire, was composed of 20% epoxy, 26% APP, 12% pentaerythritol, 8% melamine, 10% titanium oxide (TiO2), with up to 4% zirconium nitride (ZrN) replacing TiO2. With 3% ZrN, the fire protection performance of the coating was improved (time for coated metal plate to reach 580°C increased by 33%), total heat release from the coating was reduced by more than 20% and smoke production rate was reduced by 40%. The zirconium nitride led to denser, more graphitised char, suggested to be the result of formation of poly-biphenols and zirconium-phosphate or titanium-zirconium-phosphate compounds.
“Suppression on heat and smoke diffusion by zirconium nitride (ZrN) in intumescent flame retardant epoxy coatings”, F. Weihua et al., Progress in Organic Coatings 146 (2020) 105714 https://doi.org/10.1016/j.porgcoat.2020.105714