Intumescent

An intumescent is a substance that swells as a result of heat exposure, thus increasing in volume and decreasing in density. Intumescents are typically used in passive fire protection and require listing, approval and compliance in their installed configurations in order to comply with the national building codes and laws.

The details for individual building parts are specified in technical standards which are compiled and published by national or international standardization bodies like the British Standards Institute (BSI), the German Institute for Standardization (DIN), the American Society for Testing and Materials (ASTM) or the International Standardization Organization (ISO).

Intumescent Coatings for steel constructions must be approved in standardized fire tests. Some important fire test standards are listed below:

These intumescents produce a light char, which is a poor conductor of heat, thus retarding heat transfer. Typically the light char consist of microporous carbonaceous foam formed by a chemical reaction of three main components: Ammonium polyphosphate, Pentaerythritol and Melamine. The reaction takes place in a matrix formed by the molten binder which is typically based on vinyl acetate copolymers or styrene acrylates.

Ablative coatings contain a significant amount of hydrates. As the hydrates are spent, water vapour is released, which has a cooling effect. Once the water is spent, the insulation characteristics of the char that remains can slow down heat transfer from the exposed side to the unexposed side of an assembly.

Soft char producers are typically used in thin film intumescents for fireproofing structural steel as well as in firestop pillows. Typically, the expansion pressure that is created for these products is very low, because the soft carbonaceous char has little substance, which is beneficial if the aim is to produce a layer of insulation.

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