Pentaerythritol tetranitrate decomposition

Exothermic oxidation—reduction reactions provide the energy released in both propellant burning and explosive detonation. The reactions are either internal oxidation—reductions, as in the decomposition of nitroglycerin and pentaerythritol tetranitrate, or reactions between discrete oxidizers and fuels in heterogeneous mixtures. 

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... 

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). 

A study of the kinetics of thermal decomposition reactions using pentaerythritol tetranitrate(PETN), a high explosive, as the model substance was first conducted by SC-DSC. In this study, information was obtained that was relative to the characteristics of the DSC technique. However, the question as to how the results of analyses of this type were useful for practical work arose, and studies in this area were stopped. Subsequently, studies have proceeded on the evaluation of hazards by collecting as much data on self-reactive substances as possible. 

The chemical stability of pentaerythritol tetranitrate is very high and exceeds that of all other nitric add esters. It withstands the heat test at 80°C for several hours. As heating continues decomposition is gradually perceptible at temperatures above the melting point, i.e. above 140°C. Aubertein and Rehling [21] have found that water is occluded in crystals of PETN purified by recrystallization from acetone-water. The presence of these occlusions has an adverse effect on the results obtained by examinii the stability of penthrite at 132°C. Removal by grinding and drying the crystals improves the result of the stability test. 

The exothermic decomposition reaction of hydrogen peroxide indicates the possibility to be used as explosive. In fact, lead block expansion value for 99.6 % concentration H2O2 is 75-80 cm. In a steel mbe of a diameter of 34-A-O mm, 94— 100 % of H2O2 can be fully detonated with 50 g pentaerythritol tetranitrates. However, for 92 % H2O2, the detonation can propagate 100 mm away from the detonator. 

---