For well over 100 years, architects have been designing steel-framed buildings because steel, as a construction material, offers design flexibility and efficiency. Indeed, it was only when steel-framed construction had been mastered that the first skyscrapers were possible, and structural steel remains a popular choice in construction. But the use of structural steel does present a challenge: in a raging fire, steel can lose its strength, resulting a catastrophic failure, with the very real risk of serious damage and loss of life.
One way to control that risk is with special coatings called intumescent coatings. These paints react in the presence of intense heat to form an insulating layer that can extend structural integrity for up to 4 hours. AkzoNobel’s Protective Coatings business recently introduced Interchar® 1120, its first chlorine-free intumescent coating based on waterborne technology. With stricter regulations governing VOCs (volatile organic compounds) all across the globe, and builders and architects specifying healthier, and more environmentally friendly materials, Interchar® 1120 is a welcome alternative to solvent-borne intumescent coatings.
Most traditional methods of fireproofing are aesthetically unappealing and labor intensive to apply. In contrast, Interchar® 1120 can be applied easily on-site during construction and also provides an attractive finish that does not compromise intricate designs and shapes created from the steel. This allows maximum architectural expression for structures such as airports, stadiums, leisure facilities, hospitals and office buildings.
Neil Wheat, Technical Manager of Protective Coatings’ global Fire Protection Laboratory, explains: “Intumescent coatings work by undergoing a chemical reaction when heated to form an expanded, thermally insulating layer. This layer, which is predominantly a sponge-like carbonaceous char, remains adhered to the substrate and reduces the rate of temperature rise of the substrate during a fire. For the intumescent process to occur, the coating formulation includes an acid source – typically phosphorous-based, a carbon source and one or more blowing agents dispersed in a suitable resin system. At temperatures around 200°C the acid and carbon source react to form a carbonaceous melt which is then expanded by gases generated during the thermal decomposition of the blowing agents.”