CHEMICAL EXPLOSIVES
Explosives are defferentiated as low or high explosives according to their rates of burn: low explosives burn simuntaniously, while high explosives detonate.
Explosive may take years, days, hours, or a fraction of a second for the chemical decomposition. The slower processes of decomposition take place in storage. Of more interest deflagration and detonation are the two rapid forms of decomposition.
The latter term is used to describe an explosive phenomenon where the decomposition is initiated by the explosive shockwave igniting the explosive material. The front part of the shockwave is capable of passing through the high explosive material at great speeds,probably thousands of meters per second.
Explosives usually have less potential energy than petroleum fuels, but their high rate of energy release produces a great blast pressure. TNT(tri nitro toulene) has a detonation velocity of 6,940 m/s as per compared to 1,680 m/s for the detonation of a pentane-air mixture, and the 0.34-m/s stoichiometric flame speed of gasoline combustion in air.
Explosive force is released in a direction perpendicular to the surface of the explosive. If the surface is cut or shaped, the explosive forces can be focused to produce a greater local effect; this is known as a shaped charge.
In a low explosive (which deflagrates), the decomposition is propagated by a flame front which travels much more slowly through the explosive material.
© demonetisation.co.uk