What are intumescent coatings?
Intumescent coatings provide an appearance similar to that of a paint finish. At ambient temperatures, they remain stable. However, in a fire situation, the increase in temperature causes a chemical reaction.
The intumescent coating expands to many times its original thickness. This provides an insulating foam-like coating or “char” which protects the substrate.
The intumescent coating is designed to insulate the steel, and prevent the temperature of the steel from rising to a critical point at which structural failure becomes possible.
Protecting timber structures
Timber structures are more susceptible to the surface spread of flame and heat propagation. intumescent’s are designed to reduce heat propagation, and reduce the spread of flame.
How do intumescent’s work?
- The expansion process is caused by the interaction of three precisely formulated components:
- Carbon supplier: polyols as starch, pentaerythritol
- Acid source: ammonium polyphosphate
- Expanding agent: melamine
NOTE: These components are bound in a solvent or water-borne polymeric binder. Other components are added to improve the paint properties, enable easy application, enhance build and achieve faster drying.
Typical intumescent process
- As heat is applied the chemical reaction begins:
- The heat begins to soften the polymeric binder
- It also causes an organic acid to be released from the Ammonia Polyphosphate
- Carbonisation of the polyols begins
- As the blowing agent (melamine) decomposes, gas is produced which swells the molten mixture
- Finally, the foamed char solidifies, through a cross-linking reaction, to maintain the insulation
In an ideal situation, intumescent can expand to around 100 times its original thickness. To achieve this requires careful selection of formulation components and precise matching of processes involved.