Decomposition, kinetics of thermal

All explosives undergo thermal decomposition at temperatures far below those at which explosions take place. These reactions are important in determining the stability and shelf life of the explosive, The reactions also provide useful information on the susceptibility of explosives to heat. The kinetic data are normally determined under isothermal condi- 

Equation 6.14 shows the relationship between the rate of decomposition and temperature, where V is the volume of gas evolved, T is the temperature in °C, k is the reaction rate constant, and C is a constant for the particular explosive. 

For every 10 °C increase in temperature, the rate of decomposition is approximately doubled, but may increase as much as 50 times if the explosive is in the molten state. The rates of decomposition depend on the condition of storage and the presence of impurities which may act as catalysts. For example, nitroglycerine and nitrocellulose decompose at an accelerated rate due to autocatalysis, whereas the decomposition rate of TNT, picric acid and tetryl can be reduced by removing the impurities which are usually less stable than the explosive itself. With many of the explosives the presence of moisture increases the rate of decomposition. 

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Diacyl peroxides undergo thermal and photochemical decomposition to give radical intermediates (for a recent review, see Hiatt, 1971). Mechanistically the reactions are well understood as a result of the many investigations of products and kinetics of thermal decomposition (reviewed by DeTar, 1967 Cubbon, 1970). Not surprisingly, therefore, one of the earliest reports of CIDNP concerned the thermal decomposition of benzoyl peroxide (Bargon et al., 1967 Bargon and Fischer, 1967) and peroxide decompositions have been used more widely than any other class of reaction in testing theories of the phenomenon. 

The effectiveness of incineration has most commonly been estimated from the heating value of the fuel, a parameter that has little to do with the rate or mechanism of destraction. Alternative ways to assess the effectiveness of incineration destraction of various constituents of a hazardous waste stream have been proposed, such as assessment methods based on the kinetics of thermal decomposition of the constituents or on the susceptibility of individual constituents to free-radical attack. Laboratory studies of waste incineration have demonstrated that no single ranking procedure is appropriate for all incinerator conditions. For example, acceptably low levels of some test compounds, such as methylene chloride, have proved difficult to achieve because these compounds are formed in the flame from other chemical species. 

The kinetics of thermal decomposition and depolymerisation of various polymers is discussed. The aim of the study was to find reaction conditions where different polymers can be separated from mixtures by decomposing them into their monomers or into pyrolysis products and where chlorine and/or nitrogen are eliminated from the polymers without forming toxic compounds. Data are given for PVC, PS, PE, and PR 13 refs. 

Materials for a batch of ammonium perchlorate castable propellant were charged into a mechanical mixer. A metal spatula was left in accidentally, and the contents ignited when the mixer was started, owing to local friction caused by the spatula. A tool-listing safety procedure was instituted [1]. The literature on the kinetics of thermal decomposition has been reviewed critically [2],... 

How the kinetics of thermal decomposition of a solid can be studied experimentally ... 

Gas chromatography (GC) and mass spectrometry (MS) can be coupled to the TGA instrument for online identification of the evolved gases during heating pyrolysis-GC/MS is a popular technique for the evaluation of the mechanism and the kinetics of thermal decomposition of polymers and rubbers. Moreover, it allows a reliable detection and (semi)quantitative analysis of volatile additives present in an unknown polymer sample. 

Explosives E Kcals/mole + 1°gl0B Shows Memory Effect MP(°C) Kinetics of Thermal Decomposition... 

Kinetics of thermal decomposition of explosives 3-amino-5-nitro-l,2,4-triazole (ANTA) and its derivatives [38], l,3-bis(l,2,4-triazol-3-amino)-2,4,6-trinitrobenzene [39] and transition metal salts of NTO [40]. 

In a nutshell, it may be concluded that DTA, DSC and TGA have been used mainly to determine the thermal properties of explosives like melting points, thermal stability, kinetics of thermal decomposition and temperatures of initiation and ignition etc. Further, the properties which can be calculated quantitatively from the experimentally obtained values are reaction rates, activation energies and heats of explosion. DTA data of some explosives are given [46] in Table 3.6. 

This has been followed by a similar study of the heat and kinetics of thermal decomposition of the complexes (NH4)2[U02L2X], where HL = cupferron and X = CO2- or C204-.115 The ligand dissociation reactions were found to be of zero order in these latter cases, compared with first in the former cases with monovalent chloro or fluoro substituents. 

Functional properties and stability of rubbery materials Chapters 1, 3, 4, 7, 12 and 13, give examples of applications of spectroscopic techniques for the characterisation of thermal stability and degradation, kinetics of thermal decomposition, ageing, oxidation and weathering, self-diffusion of small molecules in rubbery materials, adhesion of rubbers to metals, fluid adsorption and swelling. 

Bockhorn, H., Homung, A., and Homung, U. Mechanisms and kinetics of thermal decomposition of plastics from isothermal and dynamic measurements. Journal of Analytical and Applied Pyrolysis 1999 50 25. 

Nepochirenko, G.N. (1974) Kinetics of thermal decomposition of hydride compounds and compositions on their bases, Thesis of Doctor of Chemistry, Moscow, 470 p. 

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 kinetics of thermal decomposition of three of the modifications were studied by thermogravimetry, IR spectroscopy and optical and electron microscopy (Nedelko et al. 2000), with the conclusion that the rate increases in the series a > y > s. However, it was found that the results for a particular polymorph also depend upon the morphological features of the crystals as well as their size distribution and mean size. 

Kinetics of thermal decomposition of dialkyl peroxides in solution as well as the gas phase have been reviewed by Molyneux and Frost and Pearson . The decomposition of dialkyl peroxides is moderately free from induced decomposition, compared to other types of peroxides. As seen from Table 65, the first-order rate coefficient increases by about 16 % when the initial peroxide concentration is increased about 5 fold at reasonably high peroxide concentrations. The increase in the rate coefficient is attributed to an induced decomposition where hydrogen atom abstraction generates the radical (I). Further reaction of (I) produces isobutylene oxide and the f-butoxy radical, viz. 

The kinetics of thermal decomposition of (Me3Si)2Hg in solution may be interpreted in terms of a simple bimolecular reaction yielding Hg and MegSi2 via a Hg(I) intermediate ... 

Kinetics of Thermal Decomposition. In order to examine the kinetics of thermal decomposition reactions, relative changes in IR absorption Intensity at 2120, 1250 and 1160 cm (Fig. 1), corresponding to SiH, SlCHg and NH groups, respectively, were studied as a function of pyrolysis time. Absorption data were evaluated as the ratio of areas under the peaks, A/A A being the initial... 

Badzioch, S., and Hawsksley, P. G. W. "Kinetics of Thermal Decomposition of Pulverized Coal Particles." Industrial Engineering Chemistry Process Design and Development 9, no. 4 (1970) 521-30. 

The question of why dislocations affect the kinetics of thermal decomposition reactions is not easily answered. The temperature rise in the wake of moving dislocations [73] or the kinetic energy which is converted into thermal energy on coming to rest [74] appears to be too small to account for changes in reactivity. 

Studies have also been made of the effect of photodecomposition on subsequent heat treatment of Pb(N3)2. The rate of gas evolution is altered by prior irradiation, and the results are interpreted, at least for the initial stages of decomposition, in terms of the same type of disorder production by both types of stimuli [170]. The reader is referred to Chapter 6 for additional discussion. In contrast, the kinetics of thermal decomposition of AgNa are reported to be unchanged by prior UV exposure [98]. 

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