What are Explosives?
Explosives are chemical compounds or mixture of compounds which are suitably initiated by heat, shock, friction or ignition will undergo a rapid chemical decomposition.
Explosion occurs with the evolution of heat, flash, loud sound and explosion of gases producing blast.
Types of Explosion
Normally There Are Three Types Of Explosives :
A nuclear explosive is an explosive device that derives its energy from nuclear reaction.
Almost all nuclear explosive devices that have been designed and produced are nuclear weapons intended for warfare.
Nuclear Explosive Are Of Two Types:
- Fission – Splitting of nucleus of atoms.
- Fusion – Joining together under great force the nuclei of atoms.
A mechanical explosive is one that depends on a physical reaction, such as overloading a container with compressed air.
A chemical explosive is a compound or mixture which, upon the application of heat or shock, decomposes or rearranges with extreme rapidity, yielding much gas and heat.
Categories Of Explosives
Explosives are classified as LOW or HIGH explosives according to their rates of burn.
Low Explosive Is usually a mixture of a combustible substance and an oxidant that decomposes rapidly however they burn slower than a high explosive which has an extremely fast burn rate as opposed to most high explosives which are compound.
Normally, low explosives undergo deflagration at rates that vary from a few cm/sec to approx 400 m/sec.
Low explosive are normally used as a propellants. Such as gun powder , flares and illumination devices.
High explosive compounds detonates at rates ranging from 3, 000 to 9,000 meters/sec.
High explosives are subdivide into two classes on the basis of sensitivity :-
Primary Explosives are extremely sensitive to mechanical shock, friction an heat to which they will respond by burning rapidly or detonating.
ex- mercury fulminate, lead styphnate and lead azide.
Secondary Explosive also known as base explosives. These types of explosive are extremely sensitive to shock, friction and heat.
They may burn when exposed to heat or flame in small, unconfined quantities, but detonation can occur.
Dynamite, TNT, RDX, PETN, HMX and others are examples of secondary explosives.
Composition of an Explosive
It may be composed of chemically pure compound. Such as nitroglycerine.
It may be mixture of oxidizer and a fuel, such as black powder.
-: Mixture Of An Oxidizer And A Fuel :-
- Black Powder – Potassium Nitrate(75%) + Charcoal (15%) + Sulphur(10%)
- Flash Powder – Fine Metal Powder (Usually Mg Or Aluminum). + Strong Oxidizer (Potassium Chlorate Or Perchlorate)
- Ammonal – Ammonium Nitrate + Aluminum Powder.
- Armstrong’s Mixture – Potassium Chlorate + Red Phosphorus (Sensitive Mix.) (Primary High Explosive).
- Sprengel Explosives– Strong Oxidizer + High Reactive Fuel (Chlorates + Nitroaromatics)
Chemically Pure Compound
- Nitroglycerine – A highly unstable and sensitive liquid.
- Acetone Peroxide – White Unstable Organic Peroxide.
- TNT – Yellow Insensitive crystals
- Nitrocellulose – A nitrated Polymer.
- RDX, PETN, HMX – Very powerful explosives (used in pure or in plastic explosive).
- C-4 – RDX Plastic Explosive.
What Is Chemical Explosive Reaction?
- A chemical explosive is a compound or mixture which, upon the application of heat or shock, decomposes or rearranges with extreme rapidity, yielding much gas and heat.
- For a chemical to be an explosive, it must exhibit all of the following:
- Rapid expansion (rapid production of gases or rapid heating of surroundings)
- Evolution of heat
- Rapidity of reaction
- Initiation of reaction.
Evolution Of Heat
The generation of heat in large quantities accompanies every explosive chemical reaction. Rapid liberation of heat that causes the gaseous products of reaction to expand and generate high pressures. This rapid generation of high pressures of the released gas constitutes the explosion.
Rapidity Of Reaction
Rapidity of reaction distinguishes the explosive reaction from an ordinary combustion reaction by the great speed with which it takes place.
Initiation of Reaction
This reaction occurred after being initiated by the application of shock or heat to a small portion of the mass of the explosive material.