Fire-resistant and intumescent coatings

Fire retardant and intumescent coatings limit the spread of fire, heat and smokes from combustible or structural materials, which are present in places under fire prevention standards. These coatings are used in spaces where there is a large number of people, such as shopping centers, accommodation facilities, schools or cinemas. These places are required to issue the Fire Prevention Certificate (CPI in Italian) for combustible materials, such as furniture and structural elements (e.g. wooden, steel or concrete beams).

The difference between fire-resistant and intumescent coatings is the chemical composition. The first ones contain fire-resistant or flame-retardant additives (from the Latin ignis, fire, and fugo, “”which let escape””); the latter are composed of intumescent additives (from the Latin intumescens, present participle of intuměscere, or “”to swell””).

In case of temperatures between 200°C and 300°C the fire-retardant additives release substances, inhibiting oxygen: they develop carbon dioxide or create water vapor, effectively decreasing the temperature of the combustion. Between 300°C and 400°C the fire-resistant coatings start the crystallization process. Essentially, a non-flammable vitrified layer creates a barrier for the wood.

The intumescent additives react at a temperature of 200°C, by inflating the coating film. Thus, they create a protective and insulating barrier, delaying both combustion and raising of the temperature. Normally, the flame-retardant additives are used in systems, which are applied on furniture, while the most reactive intumescent additives, which are not very transparent, are used in coatings, which are used to paint load-bearing structures.
Therefore, a fire-resistant coating, certified in Class 1 of Reaction to Fire, will contain flame-retardant additives and will be more performing concerning chemical and abrasion resistance, while an intumescent coating, certified in Class of Resistance to Fire, will be more sensitive to humidity and stress.