|
|
| Line 1: |
Line 1: |
| '''Magnesium/Teflon/Viton''' ('''MTV''') is a [[pyrolant]]. Teflon and Viton are [[trademark]]s of DuPont for [[polytetrafluoroethylene]], (C<sub>2</sub>F<sub>4</sub>)<sub>''n''</sub>, and [[FKM|fluoroelastomer]], (CH<sub>2</sub>CF<sub>2</sub>)<sub>''n''</sub>(CF(CF<sub>3</sub>)CF<sub>2</sub>)<sub>''n''</sub>.
| | Greetings! I am Marvella and I really feel comfy when people use the complete title. To play baseball is the pastime he will by no means quit doing. Years ago we moved to Puerto Rico and my family members enjoys it. For years I've been operating as a payroll clerk.<br><br>Review my webpage :: [http://javly.com/?p=56362 http://javly.com/?p=56362] |
| | |
| ==History==
| |
| [[Thermite]]s based on magnesium/Teflon/Viton, aka MTV-compositions, have been in use since the 1950s as payloads in infrared [[decoy flare]] applications. See also [[Countermeasures]]. Derived from the [[acronym]] MTV is the expression "MTV-Flare" for pyrotechnic infrared decoy flares.
| |
| | |
| ==Chemistry==
| |
| Whereas in conventional visual pyrotechnic illuminants [[sodium nitrate]], NaNO<sub>3</sub>, is used as an [[oxidizer]], in MTV compositions the polytetrafluoroethylene, (C<sub>2</sub>F<sub>4</sub>)<sub>''n''</sub>, acts as fluorine source. The very high [[reaction enthalpy]], <math> \Delta_\mathrm{R}H </math>, upon combustion of magnesium with PTFE is based on the formation of magnesium fluoride, having a very high negative [[enthalpy of formation]] ( <math> \Delta_\mathrm{f}H^o</math> = −1124 kJ mol<sup>−1</sup>):
| |
| | |
| :<big>2''n'' Mg + (C<sub>2</sub>F<sub>4</sub>)<sub>''n''</sub> → 2''n'' MgF<sub>2''(s)''</sub> + 2''n'' C, <math>\Delta_\mathrm{R}H</math> = −1438 kJ mol<sup>−1</sup></big> (1)
| |
| | |
| As lots of carbon and much heat is released upon combustion of MTV the combustion flame can be described as a [[grey body]] of high [[emissivity]].<ref>{{cite journal|doi=10.1002/(SICI)1521-4087(200001)25:1<37::AID-PREP37>3.0.CO;2-#|title=IR Emission Behaviour of Magnesium/Teflon/Viton (MTV) Compositions|year=2000|last1=Koch|first1=Ernst-Christian|last2=Dochnahl|first2=Axel|journal=Propellants, Explosives, Pyrotechnics|volume=25|pages=37}}</ref>
| |
| | |
| Depending on [[stoichiometry]], MTV displays varying [[burn rate]]s and yields different reactions products. With constant Viton-content the burn rate rises exponentially with rising magnesium content.<ref>{{cite journal|doi=10.1002/1521-4087(200211)27:5<262::AID-PREP262>3.0.CO;2-8|title=Metal-Fluorocarbon-Pyrolants: III. Development and Application of Magnesium/Teflon/Viton (MTV)|year=2002|last1=Koch|first1=Ernst-Christian|journal=Propellants, Explosives, Pyrotechnics|volume=27|issue=5|pages=262}}</ref> Nevertheless the burn rate of MTV, as is the case with many metallized pyrotechnic compositions is strongly dependent on the specific surface area of the metal fuel, that are particle morphology and dimensions. Generally magnesium powder having a high specific surface area will exhibit a higher burn rate than those having a smaller specific area. The main reactions products for MTV at [[Magnesium|Mg]] contents between 30 and 65 wt% [[magnesium fluoride]], [[soot]] and vaporized magnesium.<ref>{{cite journal|doi=10.1002/prep.200290004|title=Metal-Fluorocarbon-Pyrolants IV: Thermochemical and Combustion Behaviour of Magnesium/Teflon/Viton (MTV)|year=2002|last1=Koch|first1=Ernst-Christian|journal=Propellants, Explosives, Pyrotechnics|volume=27|issue=6|pages=340}}</ref>
| |
| | |
| For aerial decoy flares magnesium rich compositions are used with Mg contents between 55 and 65 wt%. At these stoichiometries only a part of the applied Mg reacts with the PTFE. The surplus Mg is vaporised and reacts with the atmospheric oxygen; likewise the thermally excited soot reacts with the atmospheric oxygen: | |
| | |
| :<big>''m'' Mg + (C<sub>2</sub>F<sub>4</sub>)<sub>''n''</sub> → 2''n'' MgF<sub>2''(s)''</sub> + (''m'' − 2''n'') Mg<sub>''(g)''</sub> + 2''n'' C, ''m'' ≥ 2''n'' </big> (2)
| |
| | |
| :<big>(''m'' − 2''n'') Mg<sub>''(g)''</sub> + 2''n'' C + ((1/2)''m'' + ''n'') O<sub>2''(g)''</sub> → (''m'' − 2''n'') MgO<sub>''(s)''</sub> + 2''n'' CO<sub>2''(g)''</sub></big> (3)
| |
| | |
| ==Safety==
| |
| Pyrotechnic compositions based on magnesium/polytetrafluoroethylene with stoichiometries from 25 wt% to 90 wt% magnesium are, according to German explosive legislation and the [[Koenen test]] ([[steel sleeve test]]) and [[BAM impact test]], explosive substances. Due to their sensitivity and their reaction behaviour these substances are categorized as group 1.1.2.<ref>''BGV B5 (VBG 55a) Explosivstoffe – Allgemeine Vorschrift'', Jedermann-Verlag, 69021 Heidelberg, '''2001'''.</ref> MTV compositions explode at minimum confinement (also self confinement) at relative low amounts. MTV compositions are sensitive toward thermal ignition.
| |
| In addition MTV compositions in loose and pressed state are extraordinarily sensitive towards [[electrostatic discharge]]s (ESD). Hence suitable measures have to be taken to avoid ESD while processing and handling of MTV.
| |
| | |
| ==Aerial decoy flare applications==
| |
| Since aircraft and helicopters could (and still can) counter surface-to-air and air-to-air missiles with the substance, MTV was a classified issue until the mid-1980s. It was not until 1997 that the U.S. government released a formerly classified invention, {{US patent|5679921}} (filing year 1957), that originally described the properties and applications of MTV.<ref>G.T. Hahn, P.G. Rivette, R. G. Weldon, ''Tracking Flare'', {{US patent|5679921}} '''1997''', The United States of America as represented by the Secretary of the Navy.</ref>
| |
| | |
| Although missile development has brought up seeker countermeasures against MTV flares there are still numerous missile systems fielded worldwide based on 1st Generation technology. Hence MTV flares are still not obsolete in fighting unknown threats. Together with advanced spectral flares (see [[countermeasures]]) they are part of the so-called "cocktail solution".<ref>S. I. Erwin, [http://www.nationaldefensemagazine.org/archive/2003/December/Pages/Smart_Flares3696.aspx "Smart" Flares Being Designed to Defeat Heat-Seeking Missiles], ''National Defense Magazine'', December '''2003''', 88, 14.</ref>
| |
| | |
| == Literature==
| |
| [http://onlinelibrary.wiley.com/book/10.1002/9783527644186 E.-C. Koch, ''Metal-Fluorocarbon Based Energetic Materials'', Wiley-VCH, '''2012''', 360 pages ]
| |
| | |
| ==References==
| |
| {{reflist}}
| |
| | |
| {{DEFAULTSORT:Magnesium Teflon Viton}}
| |
| [[Category:Military technology]]
| |
| [[Category:Pyrotechnic compositions]]
| |
Greetings! I am Marvella and I really feel comfy when people use the complete title. To play baseball is the pastime he will by no means quit doing. Years ago we moved to Puerto Rico and my family members enjoys it. For years I've been operating as a payroll clerk.
Review my webpage :: http://javly.com/?p=56362