Steel structures in buildings are currently coated with a fire-retardant layer to shield the bare metal from damage by fire, and to provide a standard of two hours protection from fire, in order to give the occupants sufficient time to evacuate the building. The intumescent coatings used for this purpose are thick, expensive and laborious to apply.
Now, scientists from Nanyang Technological University have worked with industrial developer JTC to develop a coating called FiroShield that can be applied to bare steel without the need for sandblasting to prepare the surface. This reduces the coating time by half, while still protecting the steel underneath against fire for two hours without falling off.
The FiroShield coating is cheaper and easier to apply, and can function aesthetically like normal paint. It has also been tested on other construction materials, such as reinforced concrete and laminated timber, showing the same performance.
The research team was led by Assistant Professor Aravind Dasari from the School of Materials Science and Engineering and Professor Tan Kang Hai from the School of Civil and Environmental Engineering.
They combined their knowledge obtained over the years of research on the different aspects of polymers and combustion, with civil and structural engineering experience to help streamline their approach.
The strength of their coating comes from a balanced mix of additives, which work well together to give off simultaneous chemical reactions when faced with extremely high temperatures.
“In a fire, our coating forms a compact charred layer that acts as a protective barrier against the heat,” said Professor Dasari.
“While typical fire coatings will also form a charred layer, those are thick and foam-like, which can fall off easily and leave the steel exposed to the fire. What we aimed at was an innovative coat that works differently from conventional intumescent coatings and can stick to the steel surface for as long as possible under high temperatures, and yet has durability and weather resistance under normal conditions without a need for a top coat of paint.”
The base material of the new coating is made of synthetic resins, which are polymers commonly used to make paints. The fire and corrosion resistant properties are conferred by a combination of common chemicals, including one that is endothermic, which absorbs the heat from the fire to start a chemical reaction that causes the coating to adhere firmly to the steel.
To achieve a two-hour fire rating, FiroShield requires five layers of coating, compared to conventional coatings, which require up to 15 layers or more. It is thus two times faster to apply and is cheaper by about 50 percent due to its lower materials cost and manpower requirements.
In addition to its fire-resistant properties and easy application, FiroShield can also protect the steel surface from corrosion, and is expected to last longer when exposed to weathering elements such as moisture and UV rays.
[Image: (From left) NTU research fellow Dr Indraneel S Zope; NTU Assistant Professor Aravind Dasari; and NTU PhD student Ng Yan Hao; standing behind the rows of FiroShield-coated steel plates used in their research and development.]