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					EXPLOSIVES
DEFINITION:
An explosive is a substance or a mixture,
which under the influence of thermal or
mechanical shock, decomposes rapidly and
spontaneously with the evolution of a great
amount of heat and large volume of gases.
EXPLOSION:
An explosive material is a material that
either is chemically or energetically unstable
& produces a sudden expansion of the
material usually accompanied by the
production of heat & gases and large
changes in pressure (and typically also loud
noise) upon initiation; this is called the
explosion.
CHARACTERISTICS OF AN
EXPLOSIVE
• Explosives must contain at least one weak chemical
  bond that can be easily broken.
• It should be cheap and stable under normal
  conditions.
• Its rate of decomposition should be fast to produce a
  large volume of gaseous products.
• It should possess high shattering power.
    Different properties are taken into consideration
    includes:
•   Test for sensitivity to impact and heat
•   Stability on storage
•   Shattering ability
•   Explosive strength per unit weight
•   Volatility
•   Density
•   Hygroscopicity
•   Toxicity
Classification Of Explosives:
Explosives are classified on the basis of velocity:

1.Detonating or high, explosives
• Primary or initiating explosives or
    detonators.
• Boosters and secondary explosives
2. Low explosives or deflagrating:
1.Primary or initiating explosives or
detonators
 They are highly sensitive explosives. They
explode on receiving a slight shock or by
ignition, and have to be very carefully handled.
Used in small quantities to start the explosion
of large quantities of less sensitive explosives.
They are usually inorganic salts.
Detonation
Examples:
Primary Explosives Include:

Mercury Fulminate
Lead Azide
Basic Lead Styphnate
Tetrazine
Diazodinitrophenol
 2.Low Explosives Or Deflagrating Or
 Propellants:
• These are classified into following two categories on
  the basis of their applications.
  1.Military explosives 2.Industrial explosives
Low explosives are compounds where the rate of
  decomposition proceeds through the material at less
  than the speed of sound.
• They only burn and do not explode, like high
  explosives.
Continue…..
• They action of low explosives is less
  shattering and evolve large volume of gas
  on combustion in a definite and controlled
  manner.
• A low explosive is usually a mixture of a
  combustible substance and an oxidant that
  decomposes rapidly (deflagration), however
  they burn slower than a high explosive
  which has an extremely fast burn rate.
Deflagration
     Difference between detonating and
        deflagrating explosive types
     Low Explosives /propellants/          High explosives/ detonating
       deflagrating explosives                       explosives
1.    Low explosives burn rapidly     1.    high explosives undergo
      (or deflagrate)                       detonations
2.    Low Explosives /propellants     2.    High explosives detonate at
      burn at lower rates i.e. 10-2         very high rates from 2 to 9
      m/s.                                  *103 m/s
3.    Reaction front is a flame       3.    Reaction front is a shock
4.    Low Explosives burn in layers         phenomena
      parallel to the surface         4.    Reaction front is moving
5.    Largely organic materials             actively throughout the
                                            material
                                      5.    Usually inorganic salts
Groups of high
explosives(HE)
 HE’s are divided into two
 sub groups:
 1. Primary Explosives
 2. Secondary Explosives
 3. Tertirary Explosives
Primary explosives
• A primary explosive is an explosive
  that is extremely sensitive to such as
  impact, friction, thermal sources of
  initiation.
• The best-known primary compound is
  nitroglycerine.
• primary explosives are sufficiently sensitive
  that they can be reliably initiated with a
  blow from a hammer
Primary Explosives
•   The characteristic of these materials as
    Primary Explosives, is that they are all
    easily initiated by one or more common
    sources such as:
   Heat
   Impact
   Shock
   Friction
 Primary explosives
Primary explosives include:
• Hexamethylene triperoxide diamine
• Lead azide
• Lead styphnate
• Mercury fulminate
• Nitrogen trichloride
• Nitrogen triiodide
• Silver azide
• Silver acetylide
• Silver fulminate
• Sodium azide
• Triacetone triperoxide
 Boosters high explosives:
• Boosters high explosives are the materials that are
  insensitive to both mechanical shock and flame.
• Decomposition proceed by means of detonation.
• An explosive booster acts as a bridge between a
  low energy explosive and a low sensitivity (but
  typically high energy) explosive such as TNT. It
  increases the explosive shockwave from an
  initiating explosive to the degree sufficient to
  detonate the secondary charge.
2- Secondary Explosives(SE)
• The common characteristics that
  differentiates SE from PE is that they are
  relatively difficult to initiate and require a
  shock wave donor, such as a Detonator in
  order to establish a sustainable
  Detonation.
Tertiary explosives
• Tertiary explosives, also called blasting agents,
  are so insensitive to shock that they cannot be
  reliably detonated by practical quantities of
  primary explosive, and instead require an
  intermediate explosive booster of secondary
  explosive. Examples include an Ammonium
  Nitrate/Fuel Oil mixture (ANFO) and slurry or
  'Wet Bag' explosives. These are primarily used in
  large-scale mining and construction operations.
• Ammonium nitrate is worlds mos twidely used
  explosive substance
Nitroglycerine & Dynamite:
Nitroglycerine & Dynamite:
 • Ist high explosive to be employed on a large
   scale
 • Nitration:
 Glycerol (99.9%) + [H2SO4(59.5%)
   +HNO3(40%) + H2O(0.5%)]
 60-90 minutes in agitated nitrators at temp <
   10°C
 Steel cooling coils…brine @ 5°C
Nitroglycerine & Dynamite:

• Nitroglycerine + spent acid…separating &
  settling tanks
• Nitroglycerine…wash tank…twice washing
Warm water
Na2CO3 (2%)
• Product…glyceryltrinitrate
• Process esterification
Nitroglycerine & Dynamite:

• Nitroglycerine is a liquid similar in
  appearance to glycerol
• Sensitive to blows
• Freezes at 13C,when solid less sensitive
• To make nitroglycerine safer to handle,
  manufactured in to dynamite
• Dynamite was originally made by absorbing
  nitroglycerine into kieselguhr (clay)
Nitroglycerine & Dynamite:

• Modern Dynamites:
 Wood flour/ammonium nitrate/sodium nitrate
  …absorbed into nitroglycerine
 75% nitroglycerine + solid form
 Other Dynamites:
 Glycol dinitrate…lower freezing point of mixture
 Gelatin dynamite: nitrocellulose (gun
  cotton)…gelled by…nitroglycerine
Explosives for mine
use…Permissibles
  • Evolve less toxic gases
  • Produce flame of small size and of short
    duration
  • In coal mines to protect from ignition of
    coaldust and air and of fire damp (air +
    methane)
Propellants, Rockets and Missiles

 • Oldest propellant…black powder
 • Best igniter available
 • Finely divided form…useless material as
   burns speedily at once
 • Made in to a dense colloid in a heavy duty
   mixer.
Propellants for Rockets

• Rocket propellants are low explosives
• Propellant ingredients must give
High chamber temp and
  pressure…(resistance materials must not
  available)
Gases of low molecular weight
• The fuel should be one which provides the
  greatest amount of heat for the smallest
  amount of weight
Propellants for Rockets

• Specific Impulse:
  Pounds of thrust per pound of weight of
  propellant burned per second
      S.I = √T/ √M
  T= absolute temperature
  M = average molecular weight of the
  exhaust gases
Propellants for Rockets

• Liquid Propellants are those added to
  combustion chamber as liquid
• This includes all liquids used in a single
  propellant system, serving gas fuel oxidizer
  and catalyst
• Large high performance rockets now use
  LOX (Liquid oxygen) and LH2 propellants
  because of their high impulse and low cost
Propellants for Rockets

• Solid Propellants:
Simple in design
More easily stored ,handled, and serviced
Classified in to 2 groups
Heterogeneous or composite propellants:
  (ingredients present in two distinct phases)
Homogeneous or double based (single
  colloidal phase)
Smokeless powder

• Replaced black powder for
Its smokelessness
Superior power
Better storage characteristics
• Principally because it can be
  formed in to stable grains whose
  size and shape governs the
  burning characteristics
CELLULOSE NITRATE
NitroCellulose

  Nitration of Cellulose;
• C6H7O2(OH)3 + 3HONO2 +H2SO4   C6H7O2(ONO2)3 + 3H2O +
  H2SO4

• With the discovery of suitable stabilization
  methods to prolong its storage life,
  nitrocellulose soon put black powder out of
  use as a propellant
• Most nitrocellulose is now made from wood
  fibers rather than cotton.
Cellulose:

•   Complicated molecule
•   Molecular weight…300,000
•   Empirical formula… [C6H7O2(OH)3]n
•   Esterification with nitric acid
•   Nitrogen content…14% in nitrocellulose
CELLULOSE NITRATE

• Pyro Cotton:
• The cellulose produced in this manner
  contains about 12.6% nitrogen … pyro
  cotton.
• Cotton nitrated to contain 13.2% nitrogen or
  greater …Gun Cotton
Smokeless Powder

• Modern military smokeless powder contains about
  13.15% nitrogen and is made from a blend of
  pyro- and gun cotton.
• Dense colloidal nitrocellulose containing about
  with plasticizer nitroglycerine or nitroglycol
 1% diphenyl amine
 Dibutyl phthalate (small amount of plasticizer)
Chemical Cotton
Black Powder
Smokeless Powder
Military Explosives

• Cost is less vital in case of military explosives and
  accent is on performance and good storage life.
• More organic materials are used than in industrial
  work
• Ammonium nitrate is the major explosive
  substance
• Military ammunition varies in size from 30 to 17in
• A complete round of ammunition is necessary to
  fire a shot.
A complete round of ammunition
A complete round of ammunition

• Thin cartridge case holding
 Primer
 [KClO3 + Pb(CNS)2 +Sb2S3 + TNT + ground glass]
 Igniter
[black powder]
 Propellant charge
[smokeless powder-coarse grained]
 Fit smoothly in to gun preventing gases to go to
   rear

				
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