explosives

Introduction
 An explosive material, also called explosive, is
a reactive substance that contains a great
amount of potential energy that can produce an
explosion if released suddenly, usually
accompanied by the production of light, heat,
sound, and pressure.
 This potential energy stored in an explosive
material may be chemical energy , pressurized
gas or nuclear energy.

Classification of Explosives :
Primary
Explosives
Low Explosives
High Explosives

Primary Explosives :
 Initiating Explosives or detonators.
 They are highly sensitive explosives , which
explode on receiving a slight shock or by
fire.
1. Lead azide :
2. Mercury Fulminate :
3. Tetracene :
4. Diazodinitro phenol :

Low Explosives
 They simply burn and do not explode
suddenly.
 The chemical reactions taking place in such
explosives are comparatively slow and their
burning proceeds from the surface inward in
layers at an approximate rate of 20 cm per
second.

Examples :
1. Black powder or gun-powder :
 It is a mixture of 75 % potassium nitrate,
15% charcol and 10% sulphur.
 Uses : for blasting, in shells, igniters for
propellants, practice bombs.

2. Smokeless powder (nitrocellulose) :
 It is prepared by treating cellulose with
nitric and sulphuric acids.
 It is called smokeless powder because it
produces carbon dioxide, carbon monoxide,
nitrogen, water vapour and almost no
smoke.

High Explosives
 They have higher energy content than
primary explosives.
 They are stable and quite insensitive to fire
and mechanical shocks.

Single compound explosives
Ammonium nitrate :
2:4:6 – trinitrotoluene (TNT):
Pentaerythritol tetranitrate :
Cylonite (RDX) :

Binary Explosives
 They consist of mixture of TNT with other
explosives.
 TNT is an important ingredient of these
binary explosives, because it has low
melting point.
 Ex : 1. Amatol: TNT + Ammonium nitrate.
2. pentolite : TNT + PETN, 50% each
3. Tropex : 40% RDX + 40% TNT +
20% Al powder.

Plastic Explosives
 Combination of explosives which are in
plastic state and can be hand moulded and
made into various shapes, without any
serious risk.

Dynamites
 They are containing of nitroglycerine(NG)
as a principal ingedient.
 NG is an oily-liquid, which detonates by
pressure, shock, or spontaneosly above 50%.
1. Straight-dynamites :
2. Blasting gelatin-dynamites :
3. Gelignite : 65% blasting gelatine + 35% of
absorbing powder. It can be used under
water.

PREPARATION &
APPLICATION OF
SOME IMPORTANT
EXPLOSSIVES

 It is prepared by reacting aqueous solutions of
sodium azide and lead nitrate with each other.
2NaN3 + Pb(NO3)2 = Pb(N3)2 + NaNO3
 During the preparation, the formation of large crystals must be
avoided, since the breakup of the crystalline needles may
produce an explosion.
 Accordingly, technical grade product is mostly manufactured
which contains 92–96% Pb(N3)2, and is precipitated in the
presence of dextrin, polyvinyl alcohol, or other substances
which interfere with crystal growth.

 It is used in detonators to initiate secondary explosives.
 In a commercially usable form, it is a white to buff powder.
 Lead azide is employed as an initiating explosive in
blasting caps.
 When used as a primary charge, it is effective in smaller
quantities than mercury fulminate, has a higher triggering
rate, and, unlike mercury fulminate, cannot be dead-pressed
by even relatively low pressures.
 In order to improve its flammability, an easily flammable
additive, such as lead trinitroresorcinate, is added.

 Mercury fulminate is prepared by dissolving mercury in
nitric acid, after which the solution is poured into 95%
ethanol.
 After a short time, vigorous gas evolution takes place and
crystals are formed.
 When the reaction is complete, the crystals are filtered by
suction and washed until neutral.
 The mercury fulminate product is obtained as small,
brown to grey pyramid-shaped crystals; the color is
caused by the presence of colloidal mercury.

 The thermal decomposition of mercury(II) fulminate can begin
at temperatures as low as 100 °C, though it proceeds at a much
higher rate with increasing temperature.
 A possible reaction for the decomposition of mercury(II)
fulminate yields carbon dioxide gas, nitrogen gas, and a
combination of relatively stable mercury salts.
Hg(CNO)2 → 2 CO + N2 + Hg
 It was used in compressed form in the manufacture of blasting
caps and percussion caps. The material, the shells, and the caps
are made of copper.

 In industry, TNT is produced in a three-step process. First,
toluene is nitrated with a mixture of sulfuric and nitric acid
to produce mononitrotoluene (MNT).
 The MNT is separated and then renitrated to dinitrotoluene
or DNT.
 In the final step, the DNT is nitrated to trinitrotoluene or
TNT using an anhydrous mixture of nitric acid and oleum.
 Nitric acid is consumed by the manufacturing process, but
the diluted sulfuric acid can be reconcentrated and reused

 TNT is one of the most commonly used explosives for
military, industrial, and mining applications.
 TNT has been used in conjunction with hydraulic
fracturing, a process used to recover oil and gas from shale
formations.
 The technique involves displacing and detonating
nitroglycerin in hydraulically induced fractures followed by
wellbore shots using pelletized TNT
 TNT neither absorbs nor dissolves in water, which allows it
to be used effectively in wet environments.
 Additionally, it is stable compared to other high explosives.
 In order to initiate an explosion, TNT must first be
detonated using a pressure wave from a more sensitive
explosive called an explosive booster.

 Gunpowder, also known as black powder, is a
chemical explosive—the earliest known. It is a mixture
of sulfur, charcoal, and potassium nitrate (saltpeter).
 The sulfur and charcoal act as fuels, and the saltpeter is
an oxidizer.
 Because of its burning properties and the amount of
heat and gas volume that it generates, gunpowder has
been widely used as a propellant in firearms and as
a pyrotechnic composition in fireworks.
 Gunpowder is classified as a low explosive because of
its relatively slow decomposition rate and consequently
low brisance.

 Gunpowder's burning rate increases with pressure, so it
bursts containers if contained but otherwise just burns
in the open.
 A simple, commonly cited, chemical equation for the
combustion of black powder is
10 KNO3 + 3 S + 8 C → 2 K2CO3 + 3K2SO4 + 6 CO2 + 5 N2.
 Because of its low brisance, black powder causes fewer
fractures and results in more usable stone compared to
other explosives, making black powder useful for
blasting monumental stone such as granite and marble.

 Black powder is well suited for blank rounds, signal
flares, burst charges, and rescue-line launches.
 Black powder is also used in fireworks for lifting
shells, in rockets as fuel, and in certain special effects.

 Nitroglycerine is prepared by running highly concentrated,
almost anhydrous, and nearly chemically pure glycerin
(dynamite glycerin) into a highly concentrated mixture of
nitric and sulfuric acids, with constantly efficient cooling and
stirring.
 At the end of the reaction the nitroglycerine acid mixture is
given to a separator, where the nitroglycerine separates by
gravity. Following washing processes with water and an
alkaline soda solution remove the diluted residual acid.

 Nitroglycerine is one of the most important and most
frequently used components of explosive materials;
together with nitroglycol, it is the major component of
gelatinous industrial explosives.
 In combination with nitrocellulose and stabilizers, it is the
principal component of powders, gun propellants and
smokeless solid rocket propellants.

 Picric acid is the chemical compound formally
called 2,4,6-trinitrophenol (TNP).
 This yellow crystalline solid is one of the most
acidic phenols.
 Its primary use, now outdated, is as an explosive.
 It has also been used in medicine (antiseptic, burn
treatments), dyes, and as a chemistry agent

 The aromatic ring of phenol is highly activated towards
electrophilic substitution reactions, and attempted
nitration of phenol, even with dilute nitric acid, results in
the formation of high molecular weight tars.
 In order to minimize these side reactions, anhydrous
phenol is sulfonated with fuming sulfuric acid, and the
resulting p-hydroxyphenylsulfonic acid is then nitrated
with concentrated nitric acid.
 During this reaction, nitro groups are introduced, and
the sulfonic acid group is displaced.
 The reaction is highly exothermic, and careful
temperature control is required.

 By far, the largest use has been in explosives.
 Explosive D aka Dunnite is the ammonium salt of
picric acid, more powerful but less stable than the
more common explosive TNT (which is produced in a
similar process to picric acid but with toluene )

PENTAERYTHRITOL
TETRANITRATE
(PETN)

 Production is by the reaction of pentaerythritol with
concentrated nitric acid to form a precipitate which
can be recrystallized from acetone to give processable
crystals.

 The most common use of PETN is as an explosive with high
brisance.
 It is more difficult to detonate than primary explosives, so
dropping or igniting it will typically not cause an explosion (at
atmospheric pressure it is difficult to ignite and burns relatively
slowly), but is more sensitive to shock and friction than other
secondary explosives such as TNT
 It is rarely used alone, but primarily used in booster and
bursting charges of small caliber ammunition, in upper charges
of detonators in some land mines and shells, and as the
explosive core of detonation cord.
 PETN is the least stable of the common military explosives, but
can be stored without significant deterioration for longer than
nitroglycerin or nitrocellulose.

RESEARCH DEPARTMENT
FORMULA X /
RDX /
CYCLONITE

CYCLOTRIMETHYLENE-
TRINITRAMINE

 It is a colourless solid, of crystal density 1.82 g/cm3.
 It is obtained by reacting white fuming nitric acid
(WFNA) with hexamine, producing dinitromethane
and ammonium nitrate as byproducts
(CH2)6N4 + 3HNO3 → (CH2-N-NO2)3 + NH3+ 3 H2O

 RDX was widely used during World War II, often in
explosive mixtures with TNT.
 RDX was used in one of the first plastic explosives.
 RDX is believed to have been used in many bomb plots
including terrorist plots.
 RDX forms the base for a number of common military
explosives.
 Outside military applications, RDX is also used in
controlled demolition to raze structures

A fuse is, a thin water
proof canvas length
of tube containing
gun powder(or TNT)
arranged to burn at a
given speed for
setting off charges of
explosives.

SAFETY FUSE
 A major contributor to progress in the use of explosives was
William Bickford in 1831 he conceived the safety fuse: a core of
black powder tightly wrapped in textiles, one of the most
important of which was jute yarn.
 The present-day version is not very different from the original
model. The cord is coated with a waterproofing agent, such as
asphalt, and is covered with either textile or plastic.
 Once ignited, safety fuses will burn underwater, and have no
external flame that might ignite methane or other fuels such as
might be found in mines or other industrial environments.
 Safety fuses are manufactured with specified burn times per
30 cm, e.g. 60 seconds, which means that a length of fuse 30 cm
long will take 60 seconds to burn.

DETONATING FUSE
 It is a thin, flexible plastic tube usually filled with
pentaerythritol tetra nitrate (PETN).
 With the PETN exploding at a rate of approximately 4
miles per second, any common length of detonation cord
appears to explode instantaneously.
 It is a high-speed fuse which explodes, rather than burns,
and is suitable for detonating high explosives. The velocity
of detonation is sufficient to use it for synchronizing
multiple charges to detonate almost simultaneously even if
the charges are placed at different distances from the point
of initiation.
 It is used to reliably and inexpensively chain together
multiple explosive charges. Typical uses include mining,
drilling, demolitions, and warfare.

 Rocket propellant is a material used by a rocket as, or to produce
in a chemical reaction, the reaction mass (propulsive mass) that is
ejected, typically with very high speed, from a rocket engine to
produce thrust, and thus provide spacecraft propulsion.
 A chemical rocket propellant undergoes exothermic chemical
reactions to produce hot gas.
 There may be a single propellant, or multiple propellants; in the
latter case one can distinguish fuel and oxidizer.
 The gases produced expand and push on a nozzle, which
accelerates them until they rush out of the back of the rocket at
extremely high speed.
 For smaller attitude control thrusters, a compressed gas escapes
the spacecraft through a propelling nozzle.

CHARACTERISTICS
OF
GOOD PROPELLENTS

 should have high specific impulse that is the propellant
should produce greater thrust (downward force or push) per
second for 1 kg of the fuel burnt.
 should produce high temperatures on combustion.
 should produce low molecular weight products during
combustion and should not leave any solid residue after
ignition.
 should burn at a slow and steady rate (that is predictable
rate of combustion).
 should possess low ignition delay (that is it should burn as
soon as it is lighted up).
 should possess high density to minimize container space.

 should be stable at a wide range of temperatures.
 should be safe for handling and storage.
 should be readily ignitable at predictable burning rate.
 should leave no solid residue after ignition.
 should not be corrosive and hygroscopic(ability to attract
and hold water molecules).
 should not produce toxic gases or corrosive gases during
combustion.

What is propellants ???
A propellant is a chemical substance used in
the production of energy or pressurized
gas that is subsequently used to
create movement of a fluid or to
generate propulsion of vehicle, projectile, or
other object.
Technically, the word propellant is the
general name for chemicals used to create
thrust.

Classifications of propellants
We have main two types of propellants.
(1)Solid propellant
may be (a) Homogeneous
(b) Heterogeneous
(1) Liquid propellant
may be (a) monopropellant
(b) bipropellant

Homogeneous solid propellant
When solid propellant or a mixture of propellant is
thoroughly mixed in a colloidal state , its called
homogeneous solid propellant.
cv When a single propellant is employed , it is called a
single-base propellant .
Nitro-cellulose , also known as gun-cotton or smokeless powder.
A solid propellant which contains two materials , is
called double-base propellant .
Ballisite , containing nitrocellulose and nitroglycerin mixture is a
powerful double base propellant .

Heterogenus solid propellant
When an oxidising agent is dispersed in a fuel mass ,
the solid propellant is called heterogeneous or
composite .
Gun powder is the oldest composite propellant .
It gives a flame temperature of 800-1500 °c and the
volume of the gases Is about 400 times the volume of
the charge .

Liquid propellants
Liquid propellants possess many advantages over the solid
propellants.
Thus , liquid propellants are more versatile and the engine using
them can be checked and calibrated more easily .
Monopropellant :
A Monopropellant has fuel as well as oxidiser in thus
same molecule or in a solution containing both these .
A Monopropellant must be safe to store and at the same
time , it should burn smoothly .
Hydrogen peroxide , nitro methane are common
monopropellants .

Bipropellants :
Bipropellants are more widely used . In these , liquid
fuel plus oxidiser , kept separately , are injected in the
combustion chamber separately .
Liquid hydrogen , hydrazine ,ethyl alcohol are common
Bipropellant .

explosives

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explosives