Engineering Chemistry S Datta

EXPLOSIVES AND PROPELLANTS 341
(v) Cyclotrimethylene trinitroamine RDX or cylonite : This highly powerful explosive
has become important for military use as well as industrial use since World War II. Its
advantages are less toxicity but greater sensitivity than TNT.
(vi) Tetryl or tetranitromethylaniline. It is made by nitration of dimethylaniline and its
melting point is around 130°C. Tetryl has important use as commercial explosive as a base
charge for blasting caps. Because of its too much sensitivity, it is used as a booster charge
intermediate between ignition charge and bursting charge for military use but not used for
main shell firing.
2. Binary explosives. These are mixtures of TNT with other explosives. TNT is the most
important ingredient due to its lower melting point. Binary explosives are made by mixing,
heating to liquify and pouring into containers to solidify. The most important ones are:
(i) Amatol. It is an explosive mixture of TNT with ammonium nitrate. TNT is deficient
in oxygen so the combustion is incomplete. The detonation products can undergo
further combustion. But 80:20 mixture of ammonium nitrate and TNT is an evenly
balanced composition with respect to oxygen with resulting increased strength and
improved fumes. The disadvantage compared to TNT is its hygroscopicity. It is
used as blasting charges in large caliber shells.
(ii) Tetrytol. It is a mixture of 70% tetryl and 30% TNT.
(iii) Pentolite. It is a mixture of 1:1 TNT and PETN.
(iv) Tropex. It is a mixture of 40% RDX, 40% TNT and 20% Al powder.
(v) Titronal. It is a mixture of 80% TNT and 20% Al flakes.
All these mixtures have some advantages over TNT alone by having higher energy or by
being cheaper.
3. Plastic explosives. These are combinations of explosives having a plastic state with
many different shapes that can be produced without risk by hand moulding or press loading.
The combination includes a high explosive mixed with wax oil (that gives the plastic nature)
and lower sensitivity. They can be made into flexible sheets, which can finally be cut into
pieces, fixed to a metal with adhesives and made to special shapes. They are used for both
industrial and military applications.
4. Dynamites. The term dynamite has been limited to those commercial explosives, which
contain nitroglycerine as the principal ingredient. Nitroglycerine is an oily liquid, which
detonates by shock or pressure above 50°C. The invention of dynamite dates back to 1866, by
Alfred Nobel, who conceived the idea of mixing the nitroglycerine with highly absorbent
materials. In this way, he converted a liquid, which is dangerous to handle and transport, to a
solid which is relatively insensitive to ordinary shock but capable of detonating by a blasting
cap. The amount of absorbent added varies the relative strength of dynamite.
4C 3
H 5
(NO 3
) 3
⎯⎯→ 10H 2
O↑ + 6H 2
↑ + 12CO 2
↑ + O 2
↑
1 vol. 10,000 vol. of explosion
The various types of dynamites are:
(i) Straight dynamites. 15 to 60% nitroglycerine are absorbed in combustible materials
like wood pulp, starch and other low-density fibres. Sodium nitrate is added as an
oxidising agent that adds on good fume properties and good blasting execution.
Antacid material like CaCO 3
to neutralize the acidity of nitroglycerine is to be added
also. Important uses of this class are blasting of hard rocks, coal, minerals etc.
(ii) Gelatin dynamites. Gelatin dynamites are made by partly gelatinising the nitroglycerine
by nitrocotton. The strongest known industrial explosive is the ‘blasting gelatin’,