Development of an epoxy-based self-intumescent fire protective coating containing an appropriate mass ratio of APP and Cu2O

A novel epoxy-based self-intumescent fire protective coating has been developed by formulating a combination of ammonium polyphosphate (APP) and copper (I) oxide (Cu₂O) in epoxy resin (EP). The effects of various combinations on fire protective performance for steel plate were evaluated using a lab-scale simulated big panel test. Formulations with different mass ratios of APP to Cu₂O ranging from 10:0 to 2:8 exhibit good fire protective performance for steel plate. While the final equilibrium backside temperature of un-protected steel plate reached 529 °C, it did not exceed 282 °C for the protected plates with 2 mm thick coatings, which is much lower than the failure temperature of steel (ca. 500 °C). The lowest final equilibrium backside temperature of coated steel plate was 234.5 °C for the optimal formulation (EP/24APP/16Cu₂O) with an APP/Cu₂O mass ratio of 6/4 in EP.

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Interestingly, the limiting oxygen index (LOI) value (46.8%) for the optimized formulation (EP/24APP/16Cu₂O) is not the highest, being lower than those of (EP/40APP/0Cu₂O) and (EP/32APP/8Cu₂O) formulations. The fire behavior of the optimized formulation (EP/24APP/16Cu₂O) and control EP was compared using the cone calorimetry. The main fire hazard parameters such as peak heat release rate, total smoke production and peak CO production for EP/24APP/16Cu₂O are reduced by 80.0%, 59.5% and 75.0%, respectively, relative to those for EP. This indicates that the EP/24APP/16Cu₂O formulation provides significantly better fire safety than does control EP alone. A possible mode of action for the combination of APP/Cu₂O in terms of the expansion ratio and heat insulation degree of the formed intumescent char layer may be proposed. Thus, this work contributed a reference for developing intumescent fire protective coating with high fire safety.

Journal of Coatings Technology and Research, Volume 21, pages 547–558, (2024)