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

LEAD AZIDE

Pb(N3)2

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 inblasting caps.

When used as a primary charge, it is effective in smallerquantities than mercury fulminate, has a higher triggeringrate, and, unlike mercury fulminate, cannot be dead-pressedby even relatively low pressures.

In order to improve its flammability, an easily flammableadditive, such as lead trinitroresorcinate, is added.

MERCURY FULMINATE

Hg(CNO)2

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.

TRINITROTOLUENE

(TNT)

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.

GUN POWDER

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.

NITROGLYCERIN

(NG)

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

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

BLASTING

FUSES

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 4miles per second, any common length of detonation cordappears to explode instantaneously.

It is a high-speed fuse which explodes, rather than burns,and is suitable for detonating high explosives. The velocityof detonation is sufficient to use it for synchronizingmultiple charges to detonate almost simultaneously even ifthe charges are placed at different distances from the pointof initiation.

It is used to reliably and inexpensively chain togethermultiple explosive charges. Typical uses include mining,drilling, demolitions, and warfare.

ROCKET

PROPELLENTS

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 propellantshould produce greater thrust (downward force or push) persecond for 1 kg of the fuel burnt.

should produce high temperatures on combustion.

should produce low molecular weight products duringcombustion and should not leave any solid residue afterignition.

should burn at a slow and steady rate (that is predictablerate of combustion).

should possess low ignition delay (that is it should burn assoon 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 .