Ignition, initiation and thermal

Ignition, Initiation and Thermal Decomposition Heat generated or lost... 

The sustained decomposition of a substance without introduction of any other apparent ignition source besides thermal energy and without air or other oxidants present. Autodecomposition is the result of a thermal self-decomposition reaction for given initial conditions (temperature, pressure, volume) at which the rate of heat evolution exceeds the rate of heat loss from the reacting system, thus resulting in an increasing reaction temperature and reaction rate. 

Relationships existing between structure, stability and thermal, photochemical and explosive decomposition (sometimes spontaneous) of the inorganic azides has been extensively investigated and reviewed [1,2]. The ignition characterisitcs of explosive inorganic azides, with or without added impurities under initiation by heat or light have been discussed [3],... 

Equations (13.7)-(13.13) are used to evaluate the ignition processes of energetic materials with appropriate initial and boundary conditions. In general, the conditions in the thermal field for ignition are given by... 

Refs 1) W.A. Taylor A. Weale, PrRoySoc 138A, 92-116(1932) (Mechanism of initiation and propagation of detonation in solid explosives) la) E. Burlot, CR 197, 1223-25 (1933) CA 28, 2538 (]934) (Ignition of explosives in vacuo) lb) A.F. Belyaev, DoklAkadN 18, 267 (1938) (Origination of detonation in explosives under the action of a thermal impulse) 2) A.F. Belyaev et al, KhimReferatZh 1940, No 10-11 CA 37, 1270(1943) (Investigation of initiation of small quantities of expls by heat with an impulse lasting for 10 3-10 secs, showed that the more volatile the expl, the harder... 

The results described above, in particular the relation between ignition energy and temperature, suggest a thermal mechanism for the initiation. The light will not be absorbed in a uniform manner in the surface layers. However, a rough estimate of the thickness of the surface layer which is heated to the ignition temperature may be obtained by assuming that the whole of the surface layer is heated to a uniform temperature. If d is the thickness of this surface layer, then... 

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. 

Andreev (Ref 154) published a book on the thermal decompn and expln of substs which includes a discussion on azides. Recent exptl work on azide research has been reviewed in a symposium on the initiation and growth of explosions in solids [Proc Roy Soc 246A, pp 145-297 (1958)]. Wyatt (Ref 160) discussed ignition by elec discharge, Bowden (Ref 162) ignition by neutrons, a-particles and fission products, Kaufman (Ref 163)... 

Energetic materials can be initiated using thermal, mechanical or electrostatic ignition sources and do not need atmospheric oxygen to maintain the exothermic reaction. 

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