JWBK121-FM October 11, 2006 21:10 Char Count= 0xxvi Background
primary explosives are poor initiators while others are powerful initiators and have found use
in detonators. Brisance is another term used in the science of explosives and refers to the
“shattering” power of an explosive. This has a direct relation to the detonation pressure or
detonation velocity.
Advances in technology mean that energetic materials are required for even more demand-
ing applications. Research in explosive technologies is now heavily focused on the design and
synthesis of explosives for specialized applications. Explosives of high thermal stability and
those with a low sensitivity to impact or friction are particularly desirable. Agrawal (Prog.
Energy Combust. Sci., 1998, 24 , 1) has proposed a different way of classifying explosives
while reviewing the recent developments in this field. This is based on a single most impor-
tant property of an explosive/high energy material, and accordingly, classifies the explosives
reported so far in the literature in the following manner.
- “Thermally Stable” or “heat-resistant” explosives
- High-performance explosives i.e. high density and high velocity of detonation (VOD) ex-
plosives
- Melt-castable explosives
- Insensitive high explosives (IHEs)
- Energetic plasticizers and binders for explosive and propellant compositions
- Energetic materials synthesized by using dinitrogen pentoxide (N 2 O 5 )
Oxygen balance (OB) is defined as the ratio of the oxygen content of a compound to the
total oxygen required for the complete oxidation of all carbon, hydrogen and other oxidisable
elements to CO 2 ,H 2 O, etc and is used to classify energetic materials as either oxygen deficient
or oxygen rich. Most energetic materials are oxygen deficient.
All the terms discussed so far try to classify an explosive from its physical or explosive
properties. The classification of explosives from a chemical viewpoint is of course more relevant
to this book. Explosives can be classified according to the functionality they contain, and in
particularly, the functional groups that impart explosive properties to a compound. Plets (Zh.
Obshch. Khim., 1953, 5 , 173) divided explosives into the following eight classes depending
on the groups they contained; each group is known as an “explosophore”.
- –NO 2 and –ONO 2 in both inorganic and organic substances
- –N=N– and –N=N=N– in inorganic and organic azides and diazo compounds.
- –NX 2 , where X=halogen
- –N=C in fulminates
- –OClO 2 and –OClO 3 in inorganic and organic chlorates and perchlorates respectively.
- –O–O– and –O–O–O– in inorganic and organic peroxides and ozonides respectively.
- –C≡C– in acetylene and metal acetylides.
- M–C metal bonded with carbon in some organometallic compounds.