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

The recent research proves that the optimal composition (EP/24APP/16Cu2O) with an APP/Cu2O mass ratio of 6/4 in EP leads to significantly better fire safety, as shown by the results of the laboratory scale simulation large field test and cone calorimetry. These findings provide an important reference for the development of intumescent fire protection coatings with high fire safety.

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.

The reserach has been published in Journal of Coatings Technology and Research Volume 21, pages 547–558, (2024).