Intumescent 1

IntumescentAn intumescent is a substance that swells as a result of heat exposure, thus increasing in volume and decreasing indensity. Intumescents are typically used in passive fire protection and, in the U.S., require listing and approval useand compliance in their installed configurations in order to comply with the law.Wikipedia:Citation needed

Types

Soft charThese intumescents produce a light char, which is a poor conductor of heat, thus retarding heat transfer. Typically,these materials contain a significant amount of hydrates. As the hydrates are spent, water vapour is released, whichhas a cooling effect. Once the water is spent, the insulation characteristics of the char that remains can slow downheat transfer from the exposed side to the unexposed side of an assembly. Soft char producers are typically used inthin film intumescents for fireproofing structural steel as well as in firestop pillows. Typically, the expansionpressure that is created for these products is very low, because the soft carbonaceous char has little substance, whichis beneficial if the aim is to produce a layer of insulation.

Hard charHarder chars are produced with sodium silicates and graphite. These products are suitable for use in plastic pipefirestops as well as exterior steel fireproofing. In those applications, it is necessary to produce a more substantialchar capable of exerting quantifiable expansion pressure. In the case of firestops, a melting, burning plastic pipemust be squeezed together and shut so that there will be no opening for fire to propagate to an otherwisefire-resistance rated wall or floor assembly. In the case of exterior fireproofing, a hydrocarbon fire must be held offwith quite potentially more kinetic energy than a house fire. Intumescents that produce hard chars are unsuitable forinterior spray fireproofing.

ApplicationsIntumescents are used to achieve passive fire protection for such applications as firestopping, fireproofing, gasketingand window casings. Such applications are relevant for buildings, offshore constructions, ships and aircraft.

ProblemsSome intumescents are susceptible to environmental influences, such as humidity, which can reduce or negate theirability to function. In Germany, the Deutsches Institut für Bautechnik, DIBt,[1] quantifies the ability of intumescentsto stand the test of time against various environmental exposures. DIBt-approved firestops and fireproofing materialsare available in Canada and the U.S.

Intumescent 2

Gallery

Low pressure intumescent resin:This product is suitable for use inpassive fire protection in general,and in firestopping and interiorfireproofing in particular. The

small, orange chunk on thebottom right is capable of

growing into the large blackobject above and to its left. Thistype of intumescent is typically

highly endothermic and containsa considerable amount of

chemically bound water inhydrates. As this is released, itcools adjacent materials. Such

intumescents are useful asingredients in firestop pillows

and in paints used forfireproofing purposes. They donot produce enough expansionforce to be used in plastic pipedevices, where the intumescent

must squeeze shut a meltingplastic pipe or conduit.

Pipe covered with athin-film intumescent

spray fireproofing productcalled unitherm. When

the flame from ablow-torch is applied, the

intumescent sodiumsilicate expands, forming

a layer of insulationwhich slows down heat

transfer to the pipeunderneath. Hydrates

within the coating give uptheir water content,

maintaining a temperaturenear the boiling point of

water, 100°C. The criticalsteel temperature is ca.

540°C. Once the water isspent and enough heat hasgone through the char, the

steel can reach andexceed its critical

temperature and then loseits strength. The time this

takes determines thefire-resistance rating.

In this picture, the flamehas been removed after

the thin-film intumescentspray fireproofing producthas completely expanded.

Some intumescentsundergo shrinkage shortly

after full expansion hastaken place.

Intumescent gasketing used inpassive fire protection, for

fire door applications.Typically, such gasketing is

needed to pass positivepressure furnace testing, a

recent requirement in NorthAmerica.

Intumescent 3

Intumescent putty,permanently pliable,

used in a cablepenetration firestop.

These putties aresimilar in

consistency to theplay-dough used as

children's toys.Putties of this naturealso lend themselves

to use as padscovering electricaloutlet boxes insidedrywall assembliesrequired to have a

fire-resistance rating.The endothermic andinsulative action of

the pads reducethermal transfer

through the metallicoutlet box to the

unexposed side ofthe rated drywall

assembly.

A passive fireprotection exampleof an intumescent

with strongexpansion pressure.This intumescent iscalled Palusol. It is

based onwaterproofed

sodium silicate.Another

high-expansionintumescent popular

for use in plasticpipe firestop devicesis graphite. Graphite

tends to be lessaffected byatmospheric

conditions thanmany water-bearing

intumescents.

Construction of a test sampleconsisting of a mock-up concrete

floor frame, complete with penetrants.The concrete frame measures

approximately 5’ x 9’ x 4" (ca. 1.5m x2.3m x 10 cm). It has a large hole in

the centre with many traversingmechanical and electrical services.

The penetrants extend 1’ (30cm) intothe furnace and 3’ (91cm) on the

unexposed side. A firestop mortar isbeing applied here. Notice the

intumescent wrap strip surroundingthe fibreglass pipe insulation. When

the fire starts, this embeddedintumescent swells to take the place

of the melting insulation. The test wasconducted in accordance with the

Canadian firestop test method ULC inScarborough, Ontario.

UNIQ-ref-0-f70ee2317a983f47-QINU

References[1] DIBt is a state-level authority concerned with technical matters related to construction (building regulations, design, testing, certification,

safety, building equipment, approvals, etc. See DIBt - Deutsches Institut für Bautechnik (http:/ / www. dibt. de/ ))

External links• "The proof is in the fire" Chemical Innovation Magazine, American Chemical Society (http:/ / pubs. acs. org/

subscribe/ archive/ ci/ 31/ i05/ html/ 05hering_new. html)• Article about intumescent materials (http:/ / ahering. webs. com/ intumescents. htm)• Translation of DIBt test procedure for intumescent building products (http:/ / ahering. webs. com/ dibt. htm)• Translation of DIBt test procedure for reactive spray fireproofing materials (http:/ / ahering. webs. com/ dibt2.

htm)• American Chemical Society: Fire Retardancy of Polypropylene Composites Using Intumescent Coatings (http:/ /

pubs. acs. org/ doi/ abs/ 10. 1021/ bk-2009-1013. ch012)• ASTM E 2786 - 2010 Standard Test Methods for Measuring Expansion of Intumescent Materials Used in Firestop

and Joint Systems (http:/ / www. astm. org/ Standards/ E2786. htm)

Article Sources and Contributors 4

Article Sources and ContributorsIntumescent  Source: http://en.wikipedia.org/w/index.php?oldid=607037467  Contributors: Ahering@cogeco.ca, Andrewman327, AnotherBrian, Blotwell, Capricorn42, Comatmebro, Dougher,EnBob08, Freederick, GS3, Giftlite, Herbert Blenstein, Hohum, Jusjih, Kilmer-san, LorenzoB, M-le-mot-dit, Macdaddy97, Materialscientist, Melchoir, MrBell, Old Moonraker, Pearle,Postlewaight, Remotelysensed, Rich Farmbrough, Satellizer, SchuminWeb, Seaphoto, Sevesteen, Sfan00 IMG, Shoefly, Sumitr1231, Surajit01, Teda13, Thabick, Thumperward, Woodshed,Woohookitty, 26 anonymous edits

Image Sources, Licenses and ContributorsImage:Intumescent.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:Intumescent.jpg  License: Creative Commons Attribution 3.0  Contributors: Achim HeringImage:Unitherm.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:Unitherm.jpg  License: Creative Commons Attribution-Sharealike 3.0  Contributors: Achim HeringImage:Unitherm2.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:Unitherm2.jpg  License: Creative Commons Attribution-Sharealike 3.0  Contributors: Achim HeringImage:Intumescent_door_gasket.svg  Source: http://en.wikipedia.org/w/index.php?title=File:Intumescent_door_gasket.svg  License: Creative Commons Attribution-Sharealike 3.0 Contributors: Int3.jpg: Achim Hering Intumescent_door_gasket.png: *Int3.jpg: Achim Hering derivative work: GS3 at en.wikipedia (Original text: self-made). derivative work: Malyszkz (talk)Image:Intfirestop.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:Intfirestop.jpg  License: Creative Commons Attribution-Sharealike 3.0  Contributors: Achim HeringImage:Palusolmanschette.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:Palusolmanschette.jpg  License: Creative Commons Attribution-Sharealike 3.0  Contributors: AchimHeringImage:Ulc_prueflingsaufbau.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:Ulc_prueflingsaufbau.jpg  License: Public Domain  Contributors: Achim Hering

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