Modeling heat transfers across a silicone-based intumescent coating

Abstract

Silicone-based intumescent coatings (SIBC) containing expandable graphite (EG) have been designed and studied in our laboratory and good physical barrier properties have been reported for both cellulosic and hydrocarbon fire scenarios. The aim of this work is to develop a preliminary 2D numerical model of this coating behavior during a fire, which is, to the best of our knowledge, not reported yet in the literature for such coating.The fire performance of SIBC containing EG was evaluated in pure radiative heating conduction using a cone calorimeter heating element at 50kW/m2. The intumescent phenomenon of the SBIC containing EG was considered as a heat transfer problem with a moving boundary. Expansion was assumed to be homogenous and occurring in one dimension and a 2D numerical heat transfer model was developed, taking into account the moving boundary using the Arbitrary Langrangian-Eulerian Method (ALE) implemented in COMSOL Multiphysics V.5.3. A water cooled sample holder with a well-defined temperature condition was used to avoid the assumption of the adiabatic conduction at the backside of the sample. The model was consistent with experimental results and it was able to reasonably predict the temperature profiles. However, it did not capture the temperature increase at times higher than 450s because of cracking in the silicone-based intumescent coating.