The thermal characteristics of different intumescent coatings

Abstract

Intumescent coatings are among the most efficient ways of fire retarding flammable materials. The coatings swell under the influence of heat and form a thick porous charred layer. The latter perfectly insulates the substrate against an excessive increase of temperature and oxygen access. In order to make intumescent coatings effective, proper selection of the essential components, i.e. carbonizing, foam-producing and dehydrating materials, is necessary. The choice of components for an intumescent fire retardant composition has an essential effect on the rate of charred mass formation and its structure. The influence of different modifiers added to amino resins during the process of condensation on fire retardant and heat-insulating efficiency of intumescent coatings for wood is presented. The fireproofing efficiency was studied by determining the heat release rate, the effective heat of combustion, the mass loss rate and the specific extinction area during the combustion of samples was investigated. The most efficient coating, both from the point of view of fire retardancy and heat insulating properties, was found to be that based on amino resin prepared from urea, dicyandiamide and monoammonium phosphate and dextrin. The exposing of wood coated with urea-dicyandiamide-phosphate-formaldehyde resin supplemented by dextrin to a heat flux of 35 kW/m2 for 30 min did not result in ignition and no increase occured in heat release, mass loss rates or in effective heat of combustion. Copyright © 1999 John Wiley & Sons, Ltd.