On the Performance of Intumescents

This article, from a Problem Solving Forum series, addresses the performance of intumescent fire-resistant coatings. The author cautions against confusing these coatings with fire-retardant coatings, whose purpose is only to reduce the surface burning characteristics (flame spread and smoke development) of a substrate. Both water and solvent borne commercial intumescent fire-resistive coatings are now available for use in published fire-resistance assemblies rated up to 3 hours. The coating itself is not fire-resistant, rather it imparts an additional degree of fire resistance to the assembly of which it is a component. Intumescent fire-resistive coatings accomplish this by forming an intumescent char layer that insulates the structural steel from the heat of the fire. The author describes the roles of the resin components of the coating and considers how performance is evaluated. The second section of the article characterized three factors that influence the performance of intumescent fire protection: robustness through the installation phase (such as ease of application, number of coats require, drying, tolerance of temperature), durability and aesthetics during the material’s service life, and the ability of the material to provide the required fire resistance at the specified thickness. The authors conclude that, in addition to fire testing of these coatings, durability and aging tests should be carried out to ensure fitness for purpose in any specific working environment.