Intumescent
Encyclopedia
An intumescent is a substance which swells as a result of heat
exposure, thus increasing in volume
, and decreasing in density
. Intumescents are typically used in passive fire protection
and, in America, require listing and approval use and compliance in their installed configurations in order to comply with the law
.
, thus retarding heat transfer. Typically, these materials also contain a significant amount of hydrate
s. As the hydrates are spent, water vapour is released, which has a cooling effect. Once the water is spent, it is only the insulation characteristics of the char that was produced, which 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
of structural steel
as well as firestop pillow
s. 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.
s and graphite
. These products are suitable for use in plastic
pipe
firestop
s as well as exterior steel fireproofing. In those applications, it is necessary to produce a more substantial char, with a quantifiable expansion pressure
. In the case of the firestops, a melting, burning plastic pipe must be squeezed together and shut so that there will be no hole for fire to go through an opening in an otherwise fire-resistance rated
wall or floor assembly. In the case of the exterior fireproofing, a hydrocarbon fire must be held off with quite potentially more kinetic energy than a house fire. Intumescents that produce hard chars are not typically used for interior spray fireproofing as they are not suitable for that application.
against various environmental exposures. DIBt approved firestops and fireproofing
materials are available in Canada
and the U.S.
Heat
In physics and thermodynamics, heat is energy transferred from one body, region, or thermodynamic system to another due to thermal contact or thermal radiation when the systems are at different temperatures. It is often described as one of the fundamental processes of energy transfer between...
exposure, thus increasing in volume
Volume
Volume is the quantity of three-dimensional space enclosed by some closed boundary, for example, the space that a substance or shape occupies or contains....
, and decreasing in density
Density
The mass density or density of a material is defined as its mass per unit volume. The symbol most often used for density is ρ . In some cases , density is also defined as its weight per unit volume; although, this quantity is more properly called specific weight...
. Intumescents are typically used in passive fire protection
Passive fire protection
Passive fire protection is an integral component of the three components of structural fire protection and fire safety in a building. PFP attempts to contain fires or slow the spread, through use of fire-resistant walls, floors, and doors...
and, in America, require listing and approval use and compliance in their installed configurations in order to comply with the law
Law
Law is a system of rules and guidelines which are enforced through social institutions to govern behavior, wherever possible. It shapes politics, economics and society in numerous ways and serves as a social mediator of relations between people. Contract law regulates everything from buying a bus...
.
Soft char producers
These intumescents produce a light char, which is a poor conductor of heatHeat
In physics and thermodynamics, heat is energy transferred from one body, region, or thermodynamic system to another due to thermal contact or thermal radiation when the systems are at different temperatures. It is often described as one of the fundamental processes of energy transfer between...
, thus retarding heat transfer. Typically, these materials also contain a significant amount of hydrate
Hydrate
Hydrate is a term used in inorganic chemistry and organic chemistry to indicate that a substance contains water. The chemical state of the water varies widely between hydrates, some of which were so labeled before their chemical structure was understood....
s. As the hydrates are spent, water vapour is released, which has a cooling effect. Once the water is spent, it is only the insulation characteristics of the char that was produced, which 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
Fireproofing
Fireproofing, a passive fire protection measure, refers to the act of making materials or structures more resistant to fire, or to those materials themselves, or the act of applying such materials. Applying a certification listed fireproofing system to certain structures allows these to have a...
of structural steel
Structural steel
Structural steel is steel construction material, a profile, formed with a specific shape or cross section and certain standards of chemical composition and mechanical properties...
as well as firestop pillow
Firestop pillow
Firestop pillows are passive fire protection items, used for firestopping holes in wall or floor assemblies required to have a fire-resistance rating...
s. 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.
Hard expanding char producers
Harder chars are produced with sodium silicateSodium silicate
Sodium silicate is the common name for a compound sodium metasilicate, Na2SiO3, also known as water glass or liquid glass. It is available in aqueous solution and in solid form and is used in cements, passive fire protection, refractories, textile and lumber processing, and automobiles...
s and graphite
Graphite
The mineral graphite is one of the allotropes of carbon. It was named by Abraham Gottlob Werner in 1789 from the Ancient Greek γράφω , "to draw/write", for its use in pencils, where it is commonly called lead . Unlike diamond , graphite is an electrical conductor, a semimetal...
. These products are suitable for use in plastic
Plastic
A plastic material is any of a wide range of synthetic or semi-synthetic organic solids used in the manufacture of industrial products. Plastics are typically polymers of high molecular mass, and may contain other substances to improve performance and/or reduce production costs...
pipe
Pipe (material)
A pipe is a tubular section or hollow cylinder, usually but not necessarily of circular cross-section, used mainly to convey substances which can flow — liquids and gases , slurries, powders, masses of small solids...
firestop
Firestop
A firestop is a passive fire protection system of various components used to seal openings and joints in fire-resistance rated wall and/or floor assemblies, based on fire testing and certification listings....
s as well as exterior steel fireproofing. In those applications, it is necessary to produce a more substantial char, with a quantifiable expansion pressure
Pressure
Pressure is the force per unit area applied in a direction perpendicular to the surface of an object. Gauge pressure is the pressure relative to the local atmospheric or ambient pressure.- Definition :...
. In the case of the firestops, a melting, burning plastic pipe must be squeezed together and shut so that there will be no hole for fire to go through an opening in an otherwise fire-resistance rated
Fire-resistance rating
A fire-resistance rating typically means the duration for which a passive fire protection system can withstand a standard fire resistance test. This can be quantified simply as a measure of time, or it may entail a host of other criteria, involving other evidence of functionality or fitness for...
wall or floor assembly. In the case of the exterior fireproofing, a hydrocarbon fire must be held off with quite potentially more kinetic energy than a house fire. Intumescents that produce hard chars are not typically used for interior spray fireproofing as they are not suitable for that application.
Problems with intumescents
Some intumescents are susceptible to environmental influences such as humidity, which can reduce or negate their ability to function. DIBt approvals quantify the ability of intumescents to stand the test of timeTime
Time is a part of the measuring system used to sequence events, to compare the durations of events and the intervals between them, and to quantify rates of change such as the motions of objects....
against various environmental exposures. DIBt approved firestops and fireproofing
Fireproofing
Fireproofing, a passive fire protection measure, refers to the act of making materials or structures more resistant to fire, or to those materials themselves, or the act of applying such materials. Applying a certification listed fireproofing system to certain structures allows these to have a...
materials are available in Canada
Canada
Canada is a North American country consisting of ten provinces and three territories. Located in the northern part of the continent, it extends from the Atlantic Ocean in the east to the Pacific Ocean in the west, and northward into the Arctic Ocean...
and the U.S.
United States
The United States of America is a federal constitutional republic comprising fifty states and a federal district...
External links
- "The proof is in the fire" Chemical Innovation Magazine, American Chemical Society
- Article about intumescent materials
- Translation of DIBt test procedure for intumescent building products
- Translation of DIBt test procedure for reactive spray fireproofing materials
- American Chemical Society: Fire Retardancy of Polypropylene Composites Using Intumescent Coatings