Pyrotechnic initiator
Encyclopedia
A pyrotechnic initiator is a device containing a pyrotechnic composition
used primarily to ignite other, more difficult-to-ignite materials, e.g. thermite
s, gas generator
s, and solid-fuel rockets. The name is often used also for the compositions themselves.
Pyrotechnic initiators are often controlled electrically (called electro-pyrotechnic initiators), e.g. using a heated bridgewire
or a bridge resistor. They are somewhat similar to blasting cap
s or other detonator
s, but they differ in that there is no intention to produce a shock wave. An example of such pyrotechnic initiator is an electric match
.
made of a fuel and oxidizer, where the fuel produces a significant amount of hot particles that cause/promote the ignition of the desired material.
Initiator compositions are similar to flash powder
s, but they differ in burning speed, as explosion
is not intended, and have intentionally high production of hot particles. They also tend to be easier to ignite than thermite
s, with whom they also share similarities.
Common oxidizers used are potassium perchlorate
and potassium nitrate
. Common fuels used are titanium
, titanium(II) hydride
, zirconium
, zirconium hydride
, and boron
. The size of the fuel particles is determined to produce hot particles with the required burning time.
More exotic materials can be used, e.g. carborane
s. http://www.patentopedia.us/baton/carborane-containing_airbag_inflator.html
For special applications, pyrophoric igniters can be used which burst into flame in contact with air. Triethylborane
was used as an igniter for the Lockheed SR-71 jet engines.
.
and 75% potassium nitrate
by weight. It is used e.g. by NASA
. It is thermally stable, stable in vacuum, and its burn rate is independent of pressure.
In comparison with black powder, BPN burns significantly hotter and leaves more of solid residues, therefore black powder is favored for multiple-use systems.
BPN's high temperature makes it suitable for uses where rapid and reproducible initiation is critical, e.g. for airbag
s, rocket engines, and decoy flares. It is however relatively expensive.
BPN can be also used as an ingredient of solid rocket propellants. http://msds.ihs.com/partinfo.aspx?partid=8864
BPN can be ignited by a laser. http://www.patentstorm.us/patents/4892037/description.html A semiconductor laser of at least 0.4 watts output can be used for ignition in vacuum. http://sciencelinks.jp/j-east/article/200704/000020070407A0071092.php
-potassium perchlorate
and titanium
-aluminium-potassium perchlorate. http://www.freepatentsonline.com/4391196.html
. They are generally safer to handle than the corresponding metal-oxidizer compositions. During burning they also release hydrogen
, which can act as a secondary fuel. Zirconium hydride, titanium hydride, and boron hydride are commonly used.
instead of pure zirconium. It is significantly safer to handle than ZPP. http://www.freepatentsonline.com/6117254.html
and potassium perchlorate. It is similar to ZHPP. Like ZHPP, it is safer to handle than titanium-potassium perchlorate. http://www.freepatentsonline.com/6117254.html
-boron
composition is one of the hottest pyrotechnic reactions in common usage. It is solid-state, gasless. It can be used as a pyrotechnic initiator or for heating confined gas to perform mechanical work. http://www.energystorm.us/Titanium_boron_Mixtures_As_Variable_Heat_Sources-r97826.html
-aluminium
laminate
s can be used as electrically initiated pyrotechnic initiators. NanoFoil
is such material, commercially available.
-clad aluminium
wires can be used as a fuse
wire, known as Pyrofuze. http://www.sigmundcohn.com/pdf/EN/pyrofuze.pdf The reaction is initiated by heat, typically supplied by electric current pulse. The reaction begins at 600 °C, the melting point of aluminium, and proceeds violently to temperature of 2200–2800 °C. The reaction does not need presence of oxygen, and the wire is consumed. http://library.lanl.gov/cgi-bin/getfile?00354289.pdf
Pyrofuze comes as a solid wire of different diameters (from 0.002" to 0.02"), braided wire, ribbon, foil, and granules. Palladium, platinum
, or palladium alloyed with 5% ruthenium
can be used together with aluminium. http://www.freepatentsonline.com/4208967.htmlhttp://www.freepatentsonline.com/5036769.html Pyrofuze bridgewire
s can be used in squib
s and electric match
es. Pyrofuze foils can be used for e.g. sealing of various dispensers or fire extinguishing systems. http://oai.dtic.mil/oai/oai?&verb=getRecord&metadataPrefix=html&identifier=ADD009057 Palladium-magnesium composition can also be used, but is not commercially available or not at least as common. http://xrint.com/patents/us/3889755
to detonation
transition in a relatively short distance, allowing its use in detonator
s. Its burning byproducts are of relatively little harm to environment. http://www.patentgenius.com/patent/6672215.html It can be ignited by a laser diode
.
, lead mononitro-resorcinates, lead dinitro-resorcinates, and lead trinitro-resorcinates. http://www.patentstorm.us/patents/5942717-description.html
Pyrotechnic composition
A pyrotechnic composition is a substance or mixture of substances designed to produce an effect by heat, light, sound, gas or smoke or a combination of these, as a result of non-detonative self-sustaining exothermic chemical reactions...
used primarily to ignite other, more difficult-to-ignite materials, e.g. thermite
Thermite
Thermite is a pyrotechnic composition of a metal powder and a metal oxide that produces an exothermic oxidation-reduction reaction known as a thermite reaction. If aluminium is the reducing agent it is called an aluminothermic reaction...
s, gas generator
Gas generator
A gas generator usually refers to a device, often similar to a solid rocket or a liquid rocket that burns to produce large volumes of relatively cool gas, instead of maximizing the temperature and specific impulse. The low temperature allows the gas to be put to use more easily in many...
s, and solid-fuel rockets. The name is often used also for the compositions themselves.
Pyrotechnic initiators are often controlled electrically (called electro-pyrotechnic initiators), e.g. using a heated bridgewire
Bridgewire
A bridgewire, bridge wire, or hot bridge wire is a relatively thin resistance wire used to set off a pyrotechnic composition serving as pyrotechnic initiator. By passing of electric current it is heated to a high temperature that starts the exothermic chemical reaction of the attached composition...
or a bridge resistor. They are somewhat similar to blasting cap
Blasting cap
A blasting cap is a small sensitive primary explosive device generally used to detonate a larger, more powerful and less sensitive secondary explosive such as TNT, dynamite, or plastic explosive....
s or other detonator
Detonator
A detonator is a device used to trigger an explosive device. Detonators can be chemically, mechanically, or electrically initiated, the latter two being the most common....
s, but they differ in that there is no intention to produce a shock wave. An example of such pyrotechnic initiator is an electric match
Electric match
An electric match is a device that uses an externally applied electric current to ignite a combustible compound.-Use:Electric matches can be used in any application where source of heat is needed at a precisely controlled point in time, typically to ignite a propellant or explosive...
.
Composition
The energetic material used, often called pyrogen, is usually a pyrotechnic compositionPyrotechnic composition
A pyrotechnic composition is a substance or mixture of substances designed to produce an effect by heat, light, sound, gas or smoke or a combination of these, as a result of non-detonative self-sustaining exothermic chemical reactions...
made of a fuel and oxidizer, where the fuel produces a significant amount of hot particles that cause/promote the ignition of the desired material.
Initiator compositions are similar to flash powder
Flash powder
Flash powder is a pyrotechnic composition, a mixture of oxidizer and metallic fuel, which burns quickly and if confined produces a loud report. It is widely used in theatrical pyrotechnics and fireworks and was once used for flashes in photography.Different varieties of flash powder are made from...
s, but they differ in burning speed, as explosion
Explosion
An explosion is a rapid increase in volume and release of energy in an extreme manner, usually with the generation of high temperatures and the release of gases. An explosion creates a shock wave. If the shock wave is a supersonic detonation, then the source of the blast is called a "high explosive"...
is not intended, and have intentionally high production of hot particles. They also tend to be easier to ignite than thermite
Thermite
Thermite is a pyrotechnic composition of a metal powder and a metal oxide that produces an exothermic oxidation-reduction reaction known as a thermite reaction. If aluminium is the reducing agent it is called an aluminothermic reaction...
s, with whom they also share similarities.
Common oxidizers used are potassium perchlorate
Potassium perchlorate
Potassium perchlorate is the inorganic salt with the chemical formula KClO4. Like other perchlorates, this salt is a strong oxidizer and potentially reacts with many organic substances...
and potassium nitrate
Potassium nitrate
Potassium nitrate is a chemical compound with the formula KNO3. It is an ionic salt of potassium ions K+ and nitrate ions NO3−.It occurs as a mineral niter and is a natural solid source of nitrogen. Its common names include saltpetre , from medieval Latin sal petræ: "stone salt" or possibly "Salt...
. Common fuels used are titanium
Titanium
Titanium is a chemical element with the symbol Ti and atomic number 22. It has a low density and is a strong, lustrous, corrosion-resistant transition metal with a silver color....
, titanium(II) hydride
Titanium(II) hydride
Titanium hydride is a chemical compound of titanium and hydrogen, a hydride. It is highly reactive and needs to be kept away from heat and strong oxidizers....
, zirconium
Zirconium
Zirconium is a chemical element with the symbol Zr and atomic number 40. The name of zirconium is taken from the mineral zircon. Its atomic mass is 91.224. It is a lustrous, grey-white, strong transition metal that resembles titanium...
, zirconium hydride
Zirconium hydride
Zirconium hydride is an inorganic chemical compound, a hydride of zirconium with the formula ZrHx. Whereas x can be as large as 4, the most common values are between 1 and 2. Zirconium hydrides form upon reaction of zirconium metal with hydrogen gas. They behave as typical metals in terms of...
, and boron
Boron
Boron is the chemical element with atomic number 5 and the chemical symbol B. Boron is a metalloid. Because boron is not produced by stellar nucleosynthesis, it is a low-abundance element in both the solar system and the Earth's crust. However, boron is concentrated on Earth by the...
. The size of the fuel particles is determined to produce hot particles with the required burning time.
More exotic materials can be used, e.g. carborane
Carborane
A carborane is a cluster composed of boron and carbon atoms. Like many of the related boranes, these clusters are polyhedra and are similarly classified as closo-, nido-, arachno-, hypho-, etc...
s. http://www.patentopedia.us/baton/carborane-containing_airbag_inflator.html
For special applications, pyrophoric igniters can be used which burst into flame in contact with air. Triethylborane
Triethylborane
Triethylborane , also called triethylborine and triethylboron, is an organoborane , a near-colorless to yellowish transparent liquid with pungent ether-like odor. Its chemical formula can be written as C6H15B, or 3B, or 3B, or Et3B.Triethylborane is strongly pyrophoric, igniting spontaneously in...
was used as an igniter for the Lockheed SR-71 jet engines.
ZPP
One of the most common initiators is ZPP, or zirconium – potassium perchlorate – a mixture of metallic zirconium and potassium perchlorate. It is also known as NASA Standard Initiator. It yields rapid pressure rise, generates little gas, emits hot particles when ignited, is thermally stable, has long shelf life, and is stable under vacuum. It is sensitive to static electricityStatic electricity
Static electricity refers to the build-up of electric charge on the surface of objects. The static charges remain on an object until they either bleed off to ground or are quickly neutralized by a discharge. Static electricity can be contrasted with current electricity, which can be delivered...
.
BPN
Another common igniter formula is BPN, BKNO3, or boron – potassium nitrate, a mixture of 25% boronBoron
Boron is the chemical element with atomic number 5 and the chemical symbol B. Boron is a metalloid. Because boron is not produced by stellar nucleosynthesis, it is a low-abundance element in both the solar system and the Earth's crust. However, boron is concentrated on Earth by the...
and 75% potassium nitrate
Potassium nitrate
Potassium nitrate is a chemical compound with the formula KNO3. It is an ionic salt of potassium ions K+ and nitrate ions NO3−.It occurs as a mineral niter and is a natural solid source of nitrogen. Its common names include saltpetre , from medieval Latin sal petræ: "stone salt" or possibly "Salt...
by weight. It is used e.g. by NASA
NASA
The National Aeronautics and Space Administration is the agency of the United States government that is responsible for the nation's civilian space program and for aeronautics and aerospace research...
. It is thermally stable, stable in vacuum, and its burn rate is independent of pressure.
In comparison with black powder, BPN burns significantly hotter and leaves more of solid residues, therefore black powder is favored for multiple-use systems.
BPN's high temperature makes it suitable for uses where rapid and reproducible initiation is critical, e.g. for airbag
Airbag
An Airbag is a vehicle safety device. It is an occupant restraint consisting of a flexible envelope designed to inflate rapidly during an automobile collision, to prevent occupants from striking interior objects such as the steering wheel or a window...
s, rocket engines, and decoy flares. It is however relatively expensive.
BPN can be also used as an ingredient of solid rocket propellants. http://msds.ihs.com/partinfo.aspx?partid=8864
BPN can be ignited by a laser. http://www.patentstorm.us/patents/4892037/description.html A semiconductor laser of at least 0.4 watts output can be used for ignition in vacuum. http://sciencelinks.jp/j-east/article/200704/000020070407A0071092.php
Others
Other mixtures encountered are aluminiumAluminium
Aluminium or aluminum is a silvery white member of the boron group of chemical elements. It has the symbol Al, and its atomic number is 13. It is not soluble in water under normal circumstances....
-potassium perchlorate
Potassium perchlorate
Potassium perchlorate is the inorganic salt with the chemical formula KClO4. Like other perchlorates, this salt is a strong oxidizer and potentially reacts with many organic substances...
and titanium
Titanium
Titanium is a chemical element with the symbol Ti and atomic number 22. It has a low density and is a strong, lustrous, corrosion-resistant transition metal with a silver color....
-aluminium-potassium perchlorate. http://www.freepatentsonline.com/4391196.html
Metal hydride-oxidizer
Metal hydride-oxidizer mixtures replace the metal with its corresponding hydrideHydride
In chemistry, a hydride is the anion of hydrogen, H−, or, more commonly, a compound in which one or more hydrogen centres have nucleophilic, reducing, or basic properties. In compounds that are regarded as hydrides, hydrogen is bonded to a more electropositive element or group...
. They are generally safer to handle than the corresponding metal-oxidizer compositions. During burning they also release hydrogen
Hydrogen
Hydrogen is the chemical element with atomic number 1. It is represented by the symbol H. With an average atomic weight of , hydrogen is the lightest and most abundant chemical element, constituting roughly 75% of the Universe's chemical elemental mass. Stars in the main sequence are mainly...
, which can act as a secondary fuel. Zirconium hydride, titanium hydride, and boron hydride are commonly used.
ZHPP
ZHPP (zirconium hydride – potassium perchlorate) is a variant of ZPP that uses zirconium hydrideZirconium hydride
Zirconium hydride is an inorganic chemical compound, a hydride of zirconium with the formula ZrHx. Whereas x can be as large as 4, the most common values are between 1 and 2. Zirconium hydrides form upon reaction of zirconium metal with hydrogen gas. They behave as typical metals in terms of...
instead of pure zirconium. It is significantly safer to handle than ZPP. http://www.freepatentsonline.com/6117254.html
THPP
THPP (titanium hydride potassium perchlorate) is a mixture of titanium(II) hydrideTitanium(II) hydride
Titanium hydride is a chemical compound of titanium and hydrogen, a hydride. It is highly reactive and needs to be kept away from heat and strong oxidizers....
and potassium perchlorate. It is similar to ZHPP. Like ZHPP, it is safer to handle than titanium-potassium perchlorate. http://www.freepatentsonline.com/6117254.html
Intermetallics
Formation of an intermetallic compound can be a strongly exothermic reaction, usable as an initiator.Titanium-boron
TitaniumTitanium
Titanium is a chemical element with the symbol Ti and atomic number 22. It has a low density and is a strong, lustrous, corrosion-resistant transition metal with a silver color....
-boron
Boron
Boron is the chemical element with atomic number 5 and the chemical symbol B. Boron is a metalloid. Because boron is not produced by stellar nucleosynthesis, it is a low-abundance element in both the solar system and the Earth's crust. However, boron is concentrated on Earth by the...
composition is one of the hottest pyrotechnic reactions in common usage. It is solid-state, gasless. It can be used as a pyrotechnic initiator or for heating confined gas to perform mechanical work. http://www.energystorm.us/Titanium_boron_Mixtures_As_Variable_Heat_Sources-r97826.html
Nickel-aluminium
NickelNickel
Nickel is a chemical element with the chemical symbol Ni and atomic number 28. It is a silvery-white lustrous metal with a slight golden tinge. Nickel belongs to the transition metals and is hard and ductile...
-aluminium
Aluminium
Aluminium or aluminum is a silvery white member of the boron group of chemical elements. It has the symbol Al, and its atomic number is 13. It is not soluble in water under normal circumstances....
laminate
Laminate
A laminate is a material that can be constructed by uniting two or more layers of material together. The process of creating a laminate is lamination, which in common parlance refers to the placing of something between layers of plastic and gluing them with heat and/or pressure, usually with an...
s can be used as electrically initiated pyrotechnic initiators. NanoFoil
NanoFoil
NanoFoil is the trademarked name for a reactive multi-layer foil material, sometimes referred to as a pyrotechnic initiator of two mutually reactive metals, aluminium and nickel, sputtered to form thin layers to create a laminated foil...
is such material, commercially available.
Palladium-aluminium
PalladiumPalladium
Palladium is a chemical element with the chemical symbol Pd and an atomic number of 46. It is a rare and lustrous silvery-white metal discovered in 1803 by William Hyde Wollaston. He named it after the asteroid Pallas, which was itself named after the epithet of the Greek goddess Athena, acquired...
-clad aluminium
Aluminium
Aluminium or aluminum is a silvery white member of the boron group of chemical elements. It has the symbol Al, and its atomic number is 13. It is not soluble in water under normal circumstances....
wires can be used as a fuse
Fuse (explosives)
In an explosive, pyrotechnic device or military munition, a fuse is the part of the device that initiates function. In common usage, the word fuse is used indiscriminately...
wire, known as Pyrofuze. http://www.sigmundcohn.com/pdf/EN/pyrofuze.pdf The reaction is initiated by heat, typically supplied by electric current pulse. The reaction begins at 600 °C, the melting point of aluminium, and proceeds violently to temperature of 2200–2800 °C. The reaction does not need presence of oxygen, and the wire is consumed. http://library.lanl.gov/cgi-bin/getfile?00354289.pdf
Pyrofuze comes as a solid wire of different diameters (from 0.002" to 0.02"), braided wire, ribbon, foil, and granules. Palladium, platinum
Platinum
Platinum is a chemical element with the chemical symbol Pt and an atomic number of 78. Its name is derived from the Spanish term platina del Pinto, which is literally translated into "little silver of the Pinto River." It is a dense, malleable, ductile, precious, gray-white transition metal...
, or palladium alloyed with 5% ruthenium
Ruthenium
Ruthenium is a chemical element with symbol Ru and atomic number 44. It is a rare transition metal belonging to the platinum group of the periodic table. Like the other metals of the platinum group, ruthenium is inert to most chemicals. The Russian scientist Karl Ernst Claus discovered the element...
can be used together with aluminium. http://www.freepatentsonline.com/4208967.htmlhttp://www.freepatentsonline.com/5036769.html Pyrofuze bridgewire
Bridgewire
A bridgewire, bridge wire, or hot bridge wire is a relatively thin resistance wire used to set off a pyrotechnic composition serving as pyrotechnic initiator. By passing of electric current it is heated to a high temperature that starts the exothermic chemical reaction of the attached composition...
s can be used in squib
Squib (explosive)
A squib is a miniature explosive device used in a wide range of industries, from special effects to military applications. It resembles a tiny stick of dynamite, both in appearance and construction, although with considerably less explosive power...
s and electric match
Electric match
An electric match is a device that uses an externally applied electric current to ignite a combustible compound.-Use:Electric matches can be used in any application where source of heat is needed at a precisely controlled point in time, typically to ignite a propellant or explosive...
es. Pyrofuze foils can be used for e.g. sealing of various dispensers or fire extinguishing systems. http://oai.dtic.mil/oai/oai?&verb=getRecord&metadataPrefix=html&identifier=ADD009057 Palladium-magnesium composition can also be used, but is not commercially available or not at least as common. http://xrint.com/patents/us/3889755
BNCP
BNCP, (cis-bis-(5-nitrotetrazolato)tetraminecobalt(III) perchlorate) is another common initiator material. It is relatively insensitive. It undergoes deflagrationDeflagration
Deflagration is a term describing subsonic combustion that usually propagates through thermal conductivity; hot burning material heats the next layer of cold material and ignites it. Most "fire" found in daily life, from flames to explosions, is deflagration...
to detonation
Detonation
Detonation involves a supersonic exothermic front accelerating through a medium that eventually drives a shock front propagating directly in front of it. Detonations are observed in both conventional solid and liquid explosives, as well as in reactive gases...
transition in a relatively short distance, allowing its use in detonator
Detonator
A detonator is a device used to trigger an explosive device. Detonators can be chemically, mechanically, or electrically initiated, the latter two being the most common....
s. Its burning byproducts are of relatively little harm to environment. http://www.patentgenius.com/patent/6672215.html It can be ignited by a laser diode
Laser diode
The laser diode is a laser where the active medium is a semiconductor similar to that found in a light-emitting diode. The most common type of laser diode is formed from a p-n junction and powered by injected electric current...
.
Lead azide
Lead azide (Pb(N3)2, or PbN6) is occasionally used in pyrotechnic initiators.Others
Other materials sensitive to heat can be used as well, e.g. tetrazene explosiveTetrazene explosive
Tetrazene is an explosive material used for sensitization of the priming compositions. It is a derivative of the compound with the IUPAC name tetrazene....
, lead mononitro-resorcinates, lead dinitro-resorcinates, and lead trinitro-resorcinates. http://www.patentstorm.us/patents/5942717-description.html