Experimental study and numerical simulation of epoxy intumescent passive fire protection performance

Epoxy intumescent coatings are materials characterized by the swelling of some of their components when exposed to high temperatures. The swelling phenomenon retards the heat transmission to the protected surface. Thus, these materials may be used as a passive fire protector (PFP), delaying the temperature rise of metal surfaces exposed to fire and preventing the damage of metal structures. The behaviour of a commercial epoxy intumescent material exposed to temperatures up to 800ºC was analyzed using Thermogravimetric Analysis as well as Differential Scanning Calorimetry techniques with the purpose to characterize its behaviour. The results showed two main decomposition regions. The first region, until 250°C, corresponds probably to the boric acid dehydration, while at the second region, from 250°C to 600°C, the degradation of the epoxy resin and the ammonium polyphosphate (APP) take place. A constant amount of residue was found at the end of both degradations (35% of the initial weight). An apparent kinetic model was developed for both regions, making possible the prediction of the behaviour of the material exposed to fire conditions. The kinetic model was used to provide data for numerical simulations of real scale tanks engulfed by fire. A finite elements model (FEM) was employed and a simplified failure criterion, combining temperature and stress distribution, was used for the evaluation of the time to failure. The consequences of the thermal exposure of coated and uncoated tanks were compared and the performance of the coating as a passive fire protection was assessed, also using specific performance indicators.