An intumescent coating is a passive fire protection specialist paint that chemically reacts when heated in a fire. The coating expands in size to form a char, which protects the steelwork for a specified period of time from the heat of the fire. Check /firebarrierexperts.com/active-fire-protection-vs-passive-fire-protection-what-is-the-difference/.
Why do you need an intumescent coating? The purpose of passive fire protection and protecting structural steel is to give the building occupants time to leave the building. Steel is a very strong and versatile building material, but at temperatures of 550ºC it begins to loose its structural integrity.
Intumescent for steel protection is commonly thick and opaque and finished with a thin protective fire retardant coat, similar to a gloss. Intumescent coatings are normally applied by airless spray to provide a smooth decorative finish, which remains stable at ambient temperatures.. These coating compositions are based on organic resin binders, which are typically acrylated rubber or epoxy.
When dry, a passive fire protection intumescent coating is a reactive layer, so it is very important to achieve the correct thickness of dry film to obtain the required fire resistance. The film thickness is measured wet with a wet-film gauge, as a certain wet film thickness will dry to a specific dry film. Several coats may need to be applied to build up to a total dry coat thickness to give the required heat protection.
The resins are filled with active ingredients, that will react in a fire at temperatures around 250°C to form a thermally insulating carbonaceous char or foam. The char can swell up to 50 times the original coating thickness.
As described above the basic formulation of an passive fire protection intumescent comprises of an organic binder, a carbonific, usually a penta or dipentaerythritol, a spumific or blowing agent which could be melamine or a melamine formaldehyde derivative, a source of an acid catalyst such as ammonium polyphosphate and additionally a char reinforcing pigment.
As the temperature rises the binder begins to melt and the blowing agent liberates gases causing a controlled expansion. At the same time there is degradation of the carbon backbone and fusion of the inorganic reinforcing materials, resulting in char solidification.
In this age of steel and glass commercial buildings, exposed steelwork is sometimes an integral design feature. Intumescent coatings allow steel to be used as an design feature (where fire protection boards would not) while also conforming to building regulations.
Intumescent passive fire protection coatings provide steel structures with corrosion protection, fire protection and a visualdecorative element if required. Until the last 10years, the typical airless unit for applying intumescent coatings was a pneumatic pump having an air motor and capable of providing up to 4 – 5,000 psi at the pump. Such a unit requires a road compressor of about 150 cfm and is a heavy unit.
Improvements in passive fire protection intumescent formulation have reduced the weight of coatings and the need for high pressure application. Today, almost all intumescent coatings can be applied with a more compact self contained unit with either a petrol engine or an electric motor.