PETN—

PETN [pentaerythritol tetranitrate, C(CH20N02)4] is an extremely sensitive high explosive. When used as a booster explosive, a bursting charge, or a plastic demolition charge, it is desensitized by mixture with trinitrotoluene or by the addition of wax. 

PETN is made by the nitration of pentaerythritol with strong (96%) nitric acid at about 50°C. 

PETN is used in making detonating fuses and commercial blasting caps, and also has a medicinal use. 

After World War I, major research programmes were inaugurated to find new and more powerful explosive materials. From these programmes came cyclotrimethylenetrinitramine [(RDX) (C3H6N606)] also called Cyclonite or Hexogen, and pentaerythritol tetranitrate [(PETN) (C5H8N4012)]. 

PETN was first prepared in 1894 by nitration of pentaerythritol. Commercial production of PETN could not be achieved until formaldehyde and acetaldehyde required in the synthesis of pentaerythritol became readily available about a decade before World War II. During World War II, RDX was utilized more than PETN because PETN was more sensitive to impact and its chemical stability was poor. Explosive compositions containing 50% PETN and 50% TNT were developed and called Pentrolit or Pentolite . This composition was used for filling hand and anti-tank grenades, and detonators. 

or pentaerythritol tetranitrate, is considerably more difficult to make than the other explosives considered to this point. Its preparation is not recommended for the casual experimenter, or for those with a clumsy streak in them. Its power and sensitivity is comparable to the other explosives in this book. It is also a crystalline solid, so it offers the same difficulties as nitromannitol in getting it compacted to maximum density for maximum power. If it were not for an extremely powerful and versatile plastique which can be made by mixing PETN with nitroglycerin, it would not be covered in this book. 

Another bad point about the two-stage nature of this process is the great amount of time which is required to make 

Finally, the quality of nitric acid used to make PETN is crucial. This process is pretty fussy in that white fuming nitric acid must be used. This means that it can have no trace of the reddish gas NOj in it. A little bit of it in the mixture will in short order lead to runaway reactions and the formation of large clouds of NO, the dreaded red gas. This ruins the batch, and poses the danger of poisoning the experimenter, and of possible explosion. 

Now let s look more closely at the first stage of PETN manufacture, making pentaerythritol. This adventure in chemistry is custom made for those who like to handle large volumes of really revolting chemicals and do endless hours of labor to get a quantity of product measured in fractions of a pound. Look once again at the materials covered earlier in this book. 

Pentaerythritol is made by reacting formaldehyde with acetaldehyde, condensing them together with the help of calcium hydroxide. 

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The commercially important explosive pentaerythritol tetranitrate [78-11-5] (PETN), C HgN40 2>... 

Only relatively few compounds can act as primary explosives and still meet the restrictive military and industrial requirements for reflabiUty, ease of manufacture, low cost, compatibiUty, and long-term storage stabiUty under adverse environmental conditions. Most initiator explosives are dense, metaHoorganic compounds. In the United States, the most commonly used explosives for detonators include lead azide, PETN, and HMX. 2,4,6-Triamino-l,3,5-triuitrobenzene (TATB) is also used in electric detonators specially designed for use where stabiUty at elevated temperatures is essential. 

Lead Azide. The azides belong to a class of very few useflil explosive compounds that do not contain oxygen. Lead azide is the primary explosive used in military detonators in the United States, and has been intensively studied (see also Lead compounds). However, lead azide is being phased out as an ignition compound in commercial detonators by substances such as diazodinitrophenol (DDNP) or PETN-based mixtures because of health concerns over the lead content in the fumes and the explosion risks and environmental impact of the manufacturing process. 

Pentaeiythritol Tetranitrate. Specification-grade pentaerythritol tetranitrate (PETN) can be stored up to 18 months at 65°C without significant deterioration. However, many materials have been found to be incompatible with PETN and the presence of as Htfle as 0.01% occluded acid or alkah greatly accelerates decomposition. The decomposition of PETN is autocatalytic with reported kinetic constants oi E = 196.6 kJ/mol (47 kcal/mol) and Z = 6.31 x 10 . The decomposition products of PETN at 210°C in wt % are 47.7 NO, 21.0 CO, 11.8 NO2, 9.5 N2O, 6.3 CO2, 2.0 H2, and 1.6... 

N2. The vapor pressure, P, of PETN in Pascals as a function of temperature is... 

Pentaerythritol may be nitrated by a batch process at 15.25°C using concentrated nitric acid in a stainless steel vessel equipped with an agitator and cooling coils to keep the reaction temperature at 15—25°C. The PETN is precipitated in a jacketed diluter by adding sufficient water to the solution to reduce the acid concentration to about 30%. The crystals are vacuum filtered and washed with water followed by washes with water containing a small amount of sodium carbonate and then cold water. The water-wet PETN is dissolved in acetone containing a small amount of sodium carbonate at 50°C and reprecipitated with water the yield is about 95%. Impurities include pentaerythritol trinitrate, dipentaerythritol hexanitrate, and tripentaerythritol acetonitrate. Pentaerythritol tetranitrate is shipped wet in water—alcohol in packing similar to that used for primary explosives. 

The Biazzi continuous process is also used. The reactants are continuously fed to a series of nitrators at 15—20°C followed by separation of the PETN, water washing, solution in acetone at 50°C, neutralization with gaseous ammonia, and precipitation by dilution with water. The overall yield is more than 95%. The acetone and the spent acid are readily recovered. 

Pentaerythritol tetranitrate is a high energy explosive that is used as a pressed base charge in blasting caps and detonators, as the core explosive in commercial detonating cord, and as the main explosive ingredient in sheet explosives. It is also mixed in various proportions with TNT to form the less sensitive pentoHtes, eg, PETN 50/TNT 50. PETN is easily initiated, its responses are reproducible, and it is readily available (144—146). 

Both RDX and HMX are stable, crystalline soHds, somewhat less sensitive to impact than PETN. Both may be handled with no physiological effect if appropriate precautions are taken to assure cleanliness of operations. Both RDX and HMX detonate to form mostiy gaseous, low molecular weight products and some intermediate formation of soHd carbons. The calculated molar detonation products of RDX are 3.00 H2O, 3.00 N2, 1.49 CO2, and 0.02 CO. RDX has been stored for as long as 10 months at 85°C without perceptible deterioration. 

D. M. Coleman and R. N. Rogers, "Pentaerythritol Tetranitrate (PETN) StabiHty and CompatibiHty," in Proceedings of Conference on Compatibility of... 

Pentaeythritol Tetranitrate (PETN), U. S. Spec. MIL-P-00387B, USGPO, Washington, D.C., 1967. 

Peroxyacetic acid, >43% and with >6% hydrogen peroxide PETN (dry)... 

Composition and Analysis of Heavy Petn leum Fractions, Klaus H. AItgelt and Mieczyslaw M. Boduszynski... 

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