Intumescent Coating for Fire Protection of Structures
As the incidence of timber railroad bridge fires increases, so has the need to develop protective measures to reduce the risk from accidental ignitions primarily caused by hot metal objects. Of the six barrier treatments evaluated in the laboratory for their ability to protect timbers from fires sourced with ignition from hot metal objects, only one intumescent coating provided adequate fire protection. The intumescent barrier treatment also met environmental, performance (e.g. bond durability), and application criteria set forth in this study. These criteria also dictated the development of a flammability test, called the hot metal test, which is compatible with the fire scenario specific to this study. The hot metal test evaluates protective materials on creosote-treated timber against ignition of gases generated by an 1100 degrees Centigrade (2012 degrees Fahrenheit) heat source. Forest Service scientists evaluated intumescent fire-retardant-treated (FRT) veneers adhered to the surface of foam core particleboard to provide adequate fire protection by means of cone calorimeter tests. The foam core particleboards were prepared with variations in surface layer treatment, adhesives, surface layer thicknesses, and processing conditions. Unprotected foam core panels generally had much higher heat release rates, somewhat higher heat of combustion, and much higher smoke production due to the polymeric foam component of tested panels, whereas time to ignition and total heat release were not pronounced from the veneer treated boards. Adding the fire retardant (intumescent cloth with veneer) to the surface particleboard provided a dramatic improvement to the measured flammability properties.