Delay composition
Encyclopedia
Delay composition, also called delay charge or delay train, is a pyrotechnic composition
, a sort of pyrotechnic initiator
, a mixture of oxidizer and fuel
that burns in a slow, constant rate that should not be significantly dependent on temperature and pressure. Delay compositions are used to introduce a delay into the firing train, e.g. to properly sequence firing of fireworks
, to delay firing of ejection charge
s in e.g. model rockets, or to introduce a few seconds of time between triggering a hand grenade
and its explosion
. Typical delay times range between several milliseconds and several seconds.
A popular delay charge is a tube of pressed black powder. The mechanical assembly prevents the outright detonation of the charge.
While delay compositions are principally similar to other fuel-oxidizer compositions, larger grain sizes and less aggressively reacting chemicals are used. Many of the compositions generate little or no gas during burning. Typical materials used are:
The burn rates are dependent on: http://www.allbusiness.com/north-america/canada/689991-1.html
Examples of some compositions are: http://www.freepyroinfo.com/Pyrotechnic/pyro_html/Explosives.htm
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...
, a sort of pyrotechnic initiator
Pyrotechnic initiator
A pyrotechnic initiator is a device containing a pyrotechnic composition used primarily to ignite other, more difficult-to-ignite materials, e.g. thermites, gas generators, and solid-fuel rockets...
, a mixture of oxidizer and fuel
Fuel
Fuel is any material that stores energy that can later be extracted to perform mechanical work in a controlled manner. Most fuels used by humans undergo combustion, a redox reaction in which a combustible substance releases energy after it ignites and reacts with the oxygen in the air...
that burns in a slow, constant rate that should not be significantly dependent on temperature and pressure. Delay compositions are used to introduce a delay into the firing train, e.g. to properly sequence firing of fireworks
Fireworks
Fireworks are a class of explosive pyrotechnic devices used for aesthetic and entertainment purposes. The most common use of a firework is as part of a fireworks display. A fireworks event is a display of the effects produced by firework devices...
, to delay firing of ejection charge
Ejection charge
Ejection charge, also called expelling charge, is a pyrotechnic composition, a type of a pyrotechnic gas generator designed to produce a small short-term amount of thrust to burst open a container and eject its content....
s in e.g. model rockets, or to introduce a few seconds of time between triggering a hand grenade
Hand grenade
A hand grenade is any small bomb that can be thrown by hand. Hand grenades are classified into three categories, explosive grenades, chemical and gas grenades. Explosive grenades are the most commonly used in modern warfare, and are designed to detonate after impact or after a set amount of time...
and its 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"...
. Typical delay times range between several milliseconds and several seconds.
A popular delay charge is a tube of pressed black powder. The mechanical assembly prevents the outright detonation of the charge.
While delay compositions are principally similar to other fuel-oxidizer compositions, larger grain sizes and less aggressively reacting chemicals are used. Many of the compositions generate little or no gas during burning. Typical materials used are:
- Fuels: siliconSiliconSilicon is a chemical element with the symbol Si and atomic number 14. A tetravalent metalloid, it is less reactive than its chemical analog carbon, the nonmetal directly above it in the periodic table, but more reactive than germanium, the metalloid directly below it in the table...
, boronBoronBoron 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...
, manganeseManganeseManganese is a chemical element, designated by the symbol Mn. It has the atomic number 25. It is found as a free element in nature , and in many minerals...
, tungstenTungstenTungsten , also known as wolfram , is a chemical element with the chemical symbol W and atomic number 74.A hard, rare metal under standard conditions when uncombined, tungsten is found naturally on Earth only in chemical compounds. It was identified as a new element in 1781, and first isolated as...
, antimonyAntimonyAntimony is a toxic chemical element with the symbol Sb and an atomic number of 51. A lustrous grey metalloid, it is found in nature mainly as the sulfide mineral stibnite...
, antimony trisulfide, zirconiumZirconiumZirconium 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...
, zirconiumZirconiumZirconium 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...
–nickelNickelNickel 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...
alloy, zincZincZinc , or spelter , is a metallic chemical element; it has the symbol Zn and atomic number 30. It is the first element in group 12 of the periodic table. Zinc is, in some respects, chemically similar to magnesium, because its ion is of similar size and its only common oxidation state is +2...
, magnesiumMagnesiumMagnesium is a chemical element with the symbol Mg, atomic number 12, and common oxidation number +2. It is an alkaline earth metal and the eighth most abundant element in the Earth's crust and ninth in the known universe as a whole...
, etc. - Oxidizers: lead oxideLead oxideLead oxide may refer to:* Lead oxide, PbO, litharge, massicot* Lead oxide, Pb3O4, minium, red lead* Lead dioxide , PbO2Less common lead oxides are:* Lead oxide, Pb2O3, lead sesquioxide...
s, iron oxideIron oxideIron oxides are chemical compounds composed of iron and oxygen. All together, there are sixteen known iron oxides and oxyhydroxides.Iron oxides and oxide-hydroxides are widespread in nature, play an important role in many geological and biological processes, and are widely utilized by humans, e.g.,...
s, barium chromateBarium chromateBarium chromate is a fine light yellow powder with the formula BaCrO4. The chromium occurs in the +6 oxidation state. It is an oxidizing agent, and produces a green flame when heated, the result of barium ions.-Reactions:...
, lead chromate, tin(IV) oxide, bismuth(III) oxide, barium sulfateBarium sulfateBarium sulfate is the inorganic compound with the chemical formula BaSO4. It is a white crystalline solid that is odorless and insoluble in water. It occurs as the mineral barite, which is the main commercial source of barium and materials prepared from it...
(for high-temperature compositions), potassium perchloratePotassium perchloratePotassium 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...
(usually used in small amount together with other oxidizers), etc. - Additives to cool down the flame and slow down the reaction can be employed; inert materials or coolants like titanium dioxideTitanium dioxideTitanium dioxide, also known as titanium oxide or titania, is the naturally occurring oxide of titanium, chemical formula . When used as a pigment, it is called titanium white, Pigment White 6, or CI 77891. Generally it comes in two different forms, rutile and anatase. It has a wide range of...
, ground glass, chalkChalkChalk is a soft, white, porous sedimentary rock, a form of limestone composed of the mineral calcite. Calcite is calcium carbonate or CaCO3. It forms under reasonably deep marine conditions from the gradual accumulation of minute calcite plates shed from micro-organisms called coccolithophores....
, sodium bicarbonateSodium bicarbonateSodium bicarbonate or sodium hydrogen carbonate is the chemical compound with the formula Na HCO3. Sodium bicarbonate is a white solid that is crystalline but often appears as a fine powder. It has a slightly salty, alkaline taste resembling that of washing soda . The natural mineral form is...
, etc. are common.
The burn rates are dependent on: http://www.allbusiness.com/north-america/canada/689991-1.html
- nature of fuel - fuels that release more heat burn faster
- nature of oxidizer - oxidizers that require less heat to decompose burn faster
- the composition ratio - stoichiometric mixtures burn the fastest, also slight excess of metallic fuel also increases burn rate, probably due to heat transfer
- particle sizes - smaller particles burn faster, but too small particles may lead to incomplete or interrupted burn due to too narrow heating zone
- mechanical assembly and housing - charge diameter and thermal conductivity of housing influence lateral heat losses
- ambient temperature - ideally this dependence is very low but extremely low or extremely high temperatures may have influence
Examples of some compositions are: http://www.freepyroinfo.com/Pyrotechnic/pyro_html/Explosives.htm
- black powder with addition of inert material, e.g. chalkChalkChalk is a soft, white, porous sedimentary rock, a form of limestone composed of the mineral calcite. Calcite is calcium carbonate or CaCO3. It forms under reasonably deep marine conditions from the gradual accumulation of minute calcite plates shed from micro-organisms called coccolithophores....
or sodium bicarbonateSodium bicarbonateSodium bicarbonate or sodium hydrogen carbonate is the chemical compound with the formula Na HCO3. Sodium bicarbonate is a white solid that is crystalline but often appears as a fine powder. It has a slightly salty, alkaline taste resembling that of washing soda . The natural mineral form is... - lead(II) oxideLead(II) oxideLead oxide is the inorganic compound with the formula PbO. Lead oxide occurs in two polymorphs, red, having a tetragonal crystal structure and yellow, having an orthorhombic crystal structure...
with siliconSiliconSilicon is a chemical element with the symbol Si and atomic number 14. A tetravalent metalloid, it is less reactive than its chemical analog carbon, the nonmetal directly above it in the periodic table, but more reactive than germanium, the metalloid directly below it in the table...
, burning at 1.5–2 cm/s - red leadRed leadLead tetroxide, also called minium, red lead or triplumbic tetroxide, is a bright red or orange crystalline or amorphous pigment. Chemically, red lead is lead tetroxide, Pb3O4, or 2PbO·PbO2....
with silicon, burning at intermediate rate - lead(IV) oxide with silicon, burning at 5–6 cm/s
- potassium permanganatePotassium permanganatePotassium permanganate is an inorganic chemical compound with the formula KMnO4. It is a salt consisting of K+ and MnO4− ions. Formerly known as permanganate of potash or Condy's crystals, it is a strong oxidizing agent. It dissolves in water to give intensely purple solutions, the...
with antimonyAntimonyAntimony is a toxic chemical element with the symbol Sb and an atomic number of 51. A lustrous grey metalloid, it is found in nature mainly as the sulfide mineral stibnite...
, very slow - manganeseManganeseManganese is a chemical element, designated by the symbol Mn. It has the atomic number 25. It is found as a free element in nature , and in many minerals...
with lead chromate and barium chromateBarium chromateBarium chromate is a fine light yellow powder with the formula BaCrO4. The chromium occurs in the +6 oxidation state. It is an oxidizing agent, and produces a green flame when heated, the result of barium ions.-Reactions:...
(lead chromate is the principal oxidizer, barium chromate acts as burning rate modifier, the more of it the slower the reaction) http://sciencelinks.jp/j-east/article/200109/000020010901A0317367.php - tungstenTungstenTungsten , also known as wolfram , is a chemical element with the chemical symbol W and atomic number 74.A hard, rare metal under standard conditions when uncombined, tungsten is found naturally on Earth only in chemical compounds. It was identified as a new element in 1781, and first isolated as...
with barium chromateBarium chromateBarium chromate is a fine light yellow powder with the formula BaCrO4. The chromium occurs in the +6 oxidation state. It is an oxidizing agent, and produces a green flame when heated, the result of barium ions.-Reactions:...
and potassium perchloratePotassium perchloratePotassium 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...
http://www.palmerpatent.com/patent_with_highlight.html?patent_num=4963204&q=additionally - boronBoronBoron 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...
with barium chromateBarium chromateBarium chromate is a fine light yellow powder with the formula BaCrO4. The chromium occurs in the +6 oxidation state. It is an oxidizing agent, and produces a green flame when heated, the result of barium ions.-Reactions:...
http://www.energetic-materials.org.cn/english/ennews.asp?newsid=10