An intumescent is a substance that swells as a result of

heat In thermodynamics, heat is defined as the form of energy crossing the boundary of a thermodynamic system by virtue of a temperature difference across the boundary. A thermodynamic system does not ''contain'' heat. Nevertheless, the term is ...

exposure, leading to an increase in

volume Volume is a measure of occupied three-dimensional space. It is often quantified numerically using SI derived units (such as the cubic metre and litre) or by various imperial or US customary units (such as the gallon, quart, cubic inch). ...

and decrease in density. Intumescent materials are typically used in

passive fire protection Passive fire protection (PFP) is components or systems of a building or structure that slows or impedes the spread of the effects of fire or smoke without system activation, and usually without movement. Examples of passive systems include floo ...

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.

Types

Soft char

These intumescent materials produce a light

char Char may refer to: People * Char Fontane, American actress * Char Margolis, American spiritualist * René Char (1907–1988), French poet *The Char family of Colombia: ** Fuad Char, Colombian senator ** Alejandro Char Chaljub, mayor of Barranquill ...

which is a poor conductor of

, 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 tetranitrate, 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 Acrylates (IUPAC: prop-2-enoates) are the salts, esters, and conjugate bases of acrylic acid. The acrylate ion is the anion C H2=CHC OO−. Often, acrylate refers to esters of acrylic acid, the most common member being methyl acrylate. These acry ...

. Ablative coatings contain a significant amount of hydrates. When the hydrates are heated, they decompose, and water vapour is released, which has a cooling effect. Once the water is spent, the insulation characteristics of the char that remains can retard heat transfer through the fire stop assembly. Soft char products are typically used in thin film intumescent materials for fireproofing

structural steel Structural steel is a category of steel used for making construction materials in a variety of shapes. Many structural steel shapes take the form of an elongated beam having a profile of a specific cross section. Structural steel shapes, si ...

as well as in firestop pillows.

Hard char

Harder char is produced with sodium silicates and

graphite Graphite () is a crystalline form of the element carbon. It consists of stacked layers of graphene. Graphite occurs naturally and is the most stable form of carbon under standard conditions. Synthetic and natural graphite are consumed on la ...

. These products are suitable for use in

plastic Plastics are a wide range of synthetic or semi-synthetic materials that use polymers as a main ingredient. Their plasticity makes it possible for plastics to be moulded, extruded or pressed into solid objects of various shapes. This adapta ...

pipe firestops in which applications it is necessary to exert expansion

pressure Pressure (symbol: ''p'' or ''P'') is the force applied perpendicular to the surface of an object per unit area over which that force is distributed. Gauge pressure (also spelled ''gage'' pressure)The preferred spelling varies by country a ...

to fill the gap left in the middle of the fires top assembly left by the melting plastic pipe.

Intumescent coatings

Intumescent coatings may be designed for protection of metals from fire, such as structural steel. They may be based on a number of resin binders including epoxy, and silicone. Melamine-formaldehyde resin systems have been used using layered double-hydroxide modified phosphate esters that improved the intumescent properties.

Problems

Some intumescent materials are susceptible to environmental influences such as humidity, which can reduce or negate their ability to function.

Gallery

File:Intumescent.jpg, Low pressure intumescent resin: This product is suitable for use in

in general, and in firestopping and interior fireproofing in particular. The small, orange chunk on the bottom right is capable of growing into the large black object above and to its left. File:Unitherm.jpg, Pipe covered with a thin-film intumescent spray fireproofing File:Unitherm2.jpg, In this picture, the flame has been removed after the thin-film intumescent spray fireproofing product has completely expanded. File:Intumescent door gasket.svg, Intumescent gasketing used in

, for fire door applications.

References

{{reflist

External links

"The proof is in the fire" Chemical Innovation Magazine, American Chemical Society
* ttps://web.archive.org/web/20100708234510/http://ahering.webs.com/dibt2.htm Translation of DIBt test procedure for reactive spray fireproofing materialsbr>American Chemical Society: Fire Retardancy of Polypropylene Composites Using Intumescent Coatings
Materials Firestops