On a planar thermal analysis of intumescent coatings

The paper discusses a complex model for a nonstationary planar thermal analysis of expandable intumescent coatings. Following the existing one‐dimensional models, we develop novel and improved equations for the two‐dimensional thermal analysis of intumescent coatings. A progressive expansion due to chemical reactions, phase changes, and the time and temperature‐dependent thermal properties of the coating are considered. In the heating process, the coating may locally experience virgin, intumesced, or charred phases, and their transition with time. The rate of the density loss due to the pyrolysis reaction is described with the Arrhenius equation. The thickness of the coating is assumed to increase enormously during the pyrolysis. Consequently, the energy and mass equilibrium equations are formulated with respect to both the deformed and undeformed configuration. Since most of material properties of commercial products are not given by manufacturers, an innovative procedure is proposed to determine the time‐dependent thermal conductivities and remaining fundamental properties of the coating from the set of measured temperatures. This, together with the two‐dimensional formulation of the thermal equations with respect to the undeformed configuration, makes the present model unique and appropriate for the thermal analyses of an arbitrary steel cross section protected with intumescent coatings.