PETN Decomposition

Gas Compositions of PETN Decomposition and Explosion (Water-free Basis in Mole % ... 

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... 

Cook (Ref 1), in describing thermal decomposition of some HE s conducted in the quartz spring apparatus (described in Ref 1, p 175 and shown there in Figs 8.1a 8.1b), stated that PETN, RDX, Tetryl and to a small extent TNT decomposed autocatalyti-cally. EDNA followed the first-order decomposition law only until about 5% of the explosive had decomposed and then the reaction stabilized. The term autostabilization was applied here on the supposition that one of the condensed decomposition products of EDNA which accumulated in the explosive apparently tended to stabilize the bulk of expl and thus slow down the decomposition. After about 10% of the expl had decompd, however, the "autocatalysis developed. 

No other expl examined by Cook et al (up to 1958) exhibited the "autostabilization effect, as did EDNA (Ref 1, pp 175-78). Fig 8.3, p 176 of Ref 1 shows the curves of first-order followed by autostabilization isothermal decomposition in EDNA at different temperatures and Fig 8.4, p 177 shows the curves autocatalyzed isothermal decomposition of PETN at different temperatures Refs 1) Cook (1958), 175-78 2) Dunkle s... 

The curves logw vs time are given on pp 176-77 for AN, EDNA PETN. This method is not applicable to expls in which.weight loss is the result solely of decomposition and not merely of vaporization or both vaporization and decomposition. It cannot be used for TNT because at the temperatures at which. it. could be applied vaporization and decomposition take place simultaneously... 

If decomposition proceeds at the same rate over entire range until practically no sample remains (like with(AN),it is said that the explosive exhibits (ideal) first-order decomposition, and that no autocatalyzation takes place as in the decompn of.PETN,Tetryl or RDX. EDNA followed the first-order decomposition law only until ca 5% of the expl had decomposed. This was followed by autostabilization, the term applied here on the supposition that one of the condensed decompn products of EDNA which accumulated in the sample apparently tended to stabilize it, thus slowing down the decompn. After ca 10% of the expl had decomposed, however, autocatalysis developed... 

Recently Lee et al (Ref 3) re-examined the behavior of PETN under 10 to 50 kbars of external pressure. They also find a reduction in decomposition rate with increasing applied pressure. HMX behaves similarly to PETN. TNT whose explosion products contain a high proportion of solid carbon, as expected from LeChatelier s Principle, shows little pressure effect on its thermal decomposition. Nitro-methane, however, appears to decompose more rapidly under an external pressure of 50 kbars than 10 kbars. This effect is not completely understood but Lee et al suggest that high pressure may favor the formation of the thermally less stable aci form of Nitromethane ... 

If all this Hugoniot energy (1/2 u ,) goes into heat (and it certainly does not) the max uniform temp rise of the PETN is only ca 36° which is clearly insufficient to even start slow decomposition in the PETN, to say nothing of producing a detonation in the observed shock initiation times Which are of the order of 1 microsec. Obviously the shock energy must he concentrated in hot spots... 

PETN and RDX in a special vacuum impact machine. Their.results showed that gases developed on impact approximate mote closely those developed on thermal decomposition chan those on deton. The results are in harmony with the hypothesis of a thermal origin of impact-initiated explns and with the slow initial burning velocities observed with the rotating drum camera... 

PETN (2.13), also known as pentaerythritol tetranitrate (C5H8N4012), is the most stable and the least reactive of the explosive nitric esters. It is insoluble in water, sparingly soluble in alcohol, ether and benzene, and soluble in acetone and methyl acetate. It shows no trace of decomposition when stored for a long time at 100 CC. It is relatively insensitive to friction but is very sensitive to initiation by a primary explosive. 

Due to its symmetrical structure, pentaerythritol tetranitrate is characterized by high resistance to many reagents. Thus PETN, differing from the majority of nitric esters, is not readily decomposed by sodium sulphide at 50°C. On the other hand, it is decomposed quite quickly by boiling in a ferrous chloride solution. Boiling with a 2.5% solution of sodium hydroxide causes very slow decomposition, whereas nitrocellulose rapidly decomposes under these conditions. 

It has been established experimentally (T. Urbanski, Kwiatkowski, Miladowski [22]) that the addition to pentaerythritol tetranitrate of such nitro compounds as nitrobenzene, nitrotoluene, dinitrobenzene, dinitrotoluene, trinitrobenzene, and trinitrotoluene, decreases its stability as determined by heating to 120-135°C. The degree of decomposition of PETN, heated alone or in mixtures, can be estimated in terms of the pH-values determining the acidity of the decomposition products (Table 32, Fig. 72). 

Pure PETN heated above its melting point explodes violently at 205-225°C. In. the primary stage of thermal decomposition, within the temperature range of 161-233°C, the activation energy E equals 47.0 kcal/mole, while logie B = 19.8, according to A. J. B. Robertson [26],... 

The following equation of decomposition, using a 1000 g sample of PETN, has been established by A. Schmidt [27] ... 

It has been found by Haid and Schmidt [28] that the equation of decomposition is practically independent on the loading density. The proportion of gaseous products resulting from the explosive decomposition of PETN under the influence of different stimuli, shown in Table 33, was determined by Bowden and Yoffe [29],... 

According to le Roux [53] tetramethylammonium nitrate has no explosive properties it did not detonate even when initiated by a strong charge of PETN. Attempts to provoke explosive decomposition by impact failed. Le Roux suggested that the compound might be used as an ingredient of explosive mixtures, for instance blended with cyclonite or incorporated in a fusible mixture with ammonium nitrate (see Vol. III). 

CA 43, 405 (1949) (Thermal decompn of PETN, NG, Ethylenediamine Dinitrate AN) l6)Ibid, TrFaradSoc 45, 85-93 (1949) CA 43, 5187 (1949) (Thermal decompn of RDX HMX) 17)A. J.B.Robertson, Third Symposium on Combustion and Flame and Explosion Phenomena , Williams Wilkins, Baltimore, Md (1949), 545 -51 (Thermal initiation of expln in liquid expls) I8)S. Livingston W.R.Tomlinson Jr, Fundamental Research on Explosives. Decomposition of Explosives at Elevated Temperatures , PAIR 1737 (1949) 19)Anon, Artillery Ammunition ,... 

Nitrocellulose, like all other nitric esters with the possible exception of PETN,.is intrinsically unstable, even at ordinary temperatures. Yet the decomposition of a thoroughly purified sample is remarkably slow. Koehler and Marqueyrol100 have made a careful study of the decomposition of nitrocellulose at various temperatures in the vacuum of a mercury pump. They found that it evolved gas at the rate of about 0.7 cc. per gram per day at 100°, 0.01 cc. per gram per day at 75°, and 0.0001 cc. per gram per day at 40°. 

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