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Fire retardants or Flame retardants are chemicals used to slow down or hinder the growth of fire and provide a sufficient amount of time to evacuate a building. Their application on construction materials is absolutely essential to meet the necessary fire safety standards and codes. Other than construction materials, fire retardants can be applied on furnishings (foam, upholstery, carpets), electronic and electrical devices and transportation products.
Fire retardants are available in various forms such as sprays, sealants, paints, powders and gels. Their application raises the threshold temperature at which a material catches fire, reduces the rate at which materials burn, and minimizes the spread of flames.
5 Effective Fire Retardants in Construction
Fire retardants are categorized on the basis of their chemical structure and properties. They are grouped based on whether they contain bromine, chlorine, phosphorus, nitrogen, metals, or boron.
Also Read: Fire Resistance Ratings of Concrete and Masonry Structural Elements
Here are some fire retardants you can use during construction :
1. Brominated Fire Retardants
They are the most efficient fire retardants in the industry. A small proportion of a BFR additive is often enough to cause a very significant effect on fire performance. The mechanism of action involves the conversion of very reactive free radicals into ones that are much less reactive. The concentration of Brominated fire retardants in products ranges from 5-30%.
Some widely used BFR products are Pentabromodiphenyl ether( in mattresses and upholstery), Decabromodiphenyl ether(electronic items, paints, PVC, rubber), Hexabromocyclododecane(all kind of building materials).
2. Chlorinated fire Retardants
CFRs are considered to be as effective as BFRs when used in synergy with other flame retardants. The mechanism of action of CFR is similar to brominated flame retardants i.e decomposition into the free radicals blocking the chain reaction, in the gaseous state.
However, CFRs also act in the solid state by changing the decomposition mechanism and the burning rate. Some examples of CFRs are the Diels-Alder diadduct of hexachlorocyclopentadiene and 1,5-cyclooctadiene.
3. Phosphorus-based Fire Retardants
Flame retardants containing phosphorus may exert different modes of action, depending on the material used and the polymer (substrate) used. They may act in the condensed phase by enhancing char (yielding intumescence) or in the gaseous phase by gas inhibition or as a combination of both.
Tricresyl phosphate(TCP), Cresyl diphenyl phosphate, and Polyols are some well known PFRs used in construction.
Alumina is a widely used flame retardant that is generally used as a hydrated material (aluminium hydroxide and magnesium hydroxide). Its mechanism of action involves the thermal decomposition to emit water, which then both cools and dilutes the vapor phase and makes combustion more difficult.
Its action is essentially physical and usually requires very large amounts to be effective. Alumina Trihydrate (ATH) is known to be a very effective alumina-based fire retardant additive in the world.
5. Intumescent systems
Intumescent flame retardant systems expand to produce foams. They are used as coatings not only to protect combustible materials such as plastics and wood but also steel structures in buildings. The mechanism of action of intumescent systems is the formation of a voluminous, insulating protective layer through carbonization and simultaneous foaming.
It must also be noted that some fire retardants are a better choice for the environment and human health compared to others. PBDEs (Polybrominated diphenyl ethers) and some other additives of Brominated class have been found to affect the human health and environment to a great degree and are at the verge of getting banned. FRS must be tailored to fit the environment, human safety and the fire safety needs.
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