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). Th ...

and decrease in

density Density (volumetric mass density or specific mass) is the substance's mass per unit of volume. The symbol most often used for density is ''ρ'' (the lower case Greek letter rho), although the Latin letter ''D'' can also be used. Mathematicall ...

. 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 floor- ...

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 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 Ammonium polyphosphate is an inorganic salt of polyphosphoric acid and ammonia containing both chains and possibly branching. Its chemical formula is H4 PO3sub>n(OH)2 showing that each monomer consists of an orthophosphate radical of a phosp ...

pentaerythritol tetranitrate Pentaerythritol tetranitrate (PETN), also known as PENT, PENTA, (ПЕНТА, primarily in Russian) TEN, corpent, or penthrite (or, rarely and primarily in German, as nitropenta), is an explosive material. It is the nitrate ester of pentaerythri ...

, and

melamine Melamine is an organic compound with the formula C3H6N6. This white solid is a trimer of cyanamide, with a 1,3,5-triazine skeleton. Like cyanamide, it contains 67% nitrogen by mass, and its derivatives have fire retardant properties due t ...

. The reaction takes place in a matrix formed by the molten binder which is typically based on

vinyl acetate Vinyl acetate is an organic compound with the formula CH3CO2CH=CH2. This colorless liquid is the precursor to polyvinyl acetate and ethene-vinyl acetate copolymers, important industrial polymers. Production The worldwide production capacity of ...

copolymers or

styrene Styrene () is an organic compound with the chemical formula C6H5CH=CH2. This derivative of benzene is a colorless oily liquid, although aged samples can appear yellowish. The compound evaporates easily and has a sweet smell, although high concen ...

acrylates. 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 Fireproofing is rendering something ( structures, materials, etc.) resistant to fire, or incombustible; or material for use in making anything fire-proof. It is a passive fire protection measure. "Fireproof" or "fireproofing" can be used as a ...

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, siz ...

as well as in firestop pillows.

Hard char

Harder char is produced with

sodium silicate Sodium silicate is a generic name for chemical compounds with the formula or ·, such as sodium metasilicate , sodium orthosilicate , and sodium pyrosilicate . The anions are often polymeric. These compounds are generally colorless transpare ...

s 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 adaptab ...

pipe Pipe(s), PIPE(S) or piping may refer to: Objects * Pipe (fluid conveyance), a hollow cylinder following certain dimension rules ** Piping, the use of pipes in industry * Smoking pipe ** Tobacco pipe * Half-pipe and quarter pipe, semi-circul ...

firestop A firestop or fire-stopping is a form of passive fire protection that is used to seal around openings and between joints in a fire-resistance-rated wall or floor assembly. Firestops are designed to maintain the fire-resistance rating of a wal ...

s 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 Epoxy is the family of basic components or Curing (chemistry), cured end products of epoxy resins. Epoxy resins, also known as polyepoxides, are a class of reactive prepolymers and polymers which contain epoxide groups. The epoxide functional ...

, 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

ping 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 Pipe(s), PIPE(S) or piping may refer to: Objects * Pipe (fluid conveyance), a hollow cylinder following certain dimension rules ** Piping, the use of pipes in industry * Smoking pipe ** Tobacco pipe * Half-pipe and quarter pipe, semi-circul ...

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 A fire door is a door with a fire-resistance rating (sometimes referred to as a ''fire protection rating'' for closures) used as part of a passive fire protection system to reduce the spread of fire and smoke between separate compartment ...

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