Deflagrating or Low Explosives

The chemical explosives are sub-divided into four main types (i) detonating or high explosives (ii) deflagrating or low explosives (iii) pyrotechnics and (iv) civil or commercial explosives. 

These explosives are characterized by very high rates of reaction and generation of high pressures on explosion. They are usually sub-divided into (i) primary or initiatory explosives, (ii) secondary explosives and (iii) tertiary explosives. 

A major difference between primary and secondary explosives arises from the fact that primary explosives are initiated to detonate by burning whereas secondary explosives are initiated to detonate by shock waves. Therefore, the most important property of a primary explosive is its ability to undergo a fast deflagration-to-detonation transition (DDT). Thus, fast DDT is the strength of primary explosives as well as their weakness. All other parameters being equal, the faster the DDT, the better the primary explosive. At the same time, 

Pyrotechnics may be considered as mixtures of materials capable of combustion when suitably initiated to produce a special effect. In most cases, pyrotechnic compositions consist of a fuel and an oxidizer together with a binder to give structural integrity and additives for imparting special effects. 

Civil explosives are also known as commercial or blasting explosives and are typically used for mining, quarrying, construction and tunnel building. They are chemical compositions, which detonate when initiated by high explosive primers or boosters or directly by detonators. They are relatively insensitive to shock, friction or impact 

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Explosives of this kind are known as deflagrating or low explosives. BkPdr and smoke- less propellants are examples. The simplest device for ignition is Bickford or miner s safety fuse, described in Ref 44, p B112-L. 

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