Maya Ellison
Plastic explosives are soft and hand-mouldable solid forms of explosive material. They are commonly used for explosive demolition and shock-hardening high manganese percentage steel. Plastic explosives cannot be detonated by a gunshot or by dropping them onto a hard surface. They do not explode when set on fire or exposed to microwaves. They can only be detonated by a shockwave, such as when a detonator inserted into it is fired. C-4 is a common variety of plastic explosives and is used in terrorist attacks all over the world.
| Characteristics | Values |
|---|---|
| Detonation | Only by a shockwave from a detonator or blasting cap |
| Detonator | A small explosive that's relatively easy to set off |
| Detonator example | Electrical detonator, which uses a brief charge to set off a small amount of explosive material |
| Detonation process | The explosion applies a powerful shock that triggers the C-4 explosive material |
| Chemical reaction | C-4 decomposes to release nitrogen, water, carbon oxides, and other gases |
| Expansion rate | 26,400 feet per second (8,050 meters per second) |
| Other methods | C-4 cannot be detonated by a gunshot or by dropping it onto a hard surface. It does not explode when set on fire or exposed to microwaves |
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What You'll Learn
Detonation by shockwave
Plastic explosives are soft and hand-mouldable solid forms of explosive material. They are commonly used for explosive demolition and shock-hardening high manganese percentage steel. Plastic explosives are not usually used for ordinary blasting as they are more expensive than other materials with similar performance.
C-4, or Composition C-4, is a common variety of plastic explosive. It is composed of explosives, plastic binder, plasticizer (to make it malleable), and usually a marker or odorizing taggant chemical. C-4 has a texture similar to modelling clay and can be moulded into any desired shape. It is very stable and insensitive to most physical shocks. It cannot be detonated by a gunshot or by dropping it onto a hard surface. It does not explode when set on fire or exposed to microwaves.
C-4 can only be detonated by a shockwave from a detonator or blasting cap. When the detonator is fired, the explosive is converted into compressed gas. The detonation proceeds at an explosive velocity of 8,092 m/s (26,550 ft/s). The minimum initiating charge required is 0.2 grams of lead azide or 0.1 grams of tetryl.
C-4 produced for use by the U.S. military and commercial C-4 are blended with different oils and have unique properties. The oil and plasticizer must be separated from the C-4 sample, typically by using a non-polar organic solvent such as pentane followed by solid-phase extraction of the plasticizer on silica.
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Detonators and blasting caps
Commonly used primary explosives include lead azide, lead styphnate, tetryl, and DDNP (diazo dinitro phenol). In military applications, a small amount of TNT or tetryl is often used, while commercial detonators may use PETN. The first blasting cap or detonator was demonstrated in 1745 by British physician William Watson, who showed that an electric spark could ignite black powder. Later, in 1832, a hot wire detonator was produced by American chemist Robert Hare. This used a fine wire that became incandescent and ignited gunpowder when a strong current was passed through it.
The first generally modern blasting caps were developed in 1875 by Henry Julius Smith and Perry G. Gardner. These combined a hot wire detonator with mercury fulminate explosive. Electric match caps were later developed in Germany in the early 1900s and spread to the US in the 1950s. Non-electric detonators were also invented in the 1960s and 1970s by the Swedish company Nitro Nobel. These use a hollow plastic tube to deliver the firing impulse to the detonator, rather than electric wires, making them safer.
Blasting caps and detonators are subject to strict safety regulations, particularly during transport and storage. For example, smoking and open flames are prohibited within 50 feet of explosives and detonator storage magazines. When blasting, special precautions must be taken in congested areas or near structures to control the throw of fragments and prevent injury.
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C-4's chemical reaction
C-4, or Composition C-4, is a plastic explosive manufactured by combining explosive chemicals with a plastic binder material. The binder coats the explosive material, reducing its sensitivity to shock and heat. C-4 is composed of explosives, a plastic binder, a plasticizer to increase plasticity, and usually a marker or odorizing taggant chemical. The final material is a solid with a dirty white to light brown colour, a putty-like texture similar to modelling clay, and a distinct smell of motor oil.
C-4 is a high explosive, which means it undergoes a rapid chemical reaction when triggered by heat or shock energy from a detonator. This chemical reaction involves the decomposition of C-4 to release a variety of gases, notably nitrogen, water, and carbon oxides. The reactants, or original chemical compounds, have a lot of energy stored in the chemical bonds between different atoms. When the compound molecules break apart, the resulting gases may use some of this energy to form new bonds, but not all of it.
The decomposition reaction occurs very quickly, producing a lot of heat and gas in a short amount of time. The gases expand at an extremely high rate, generating a massive amount of pressure and applying a tremendous amount of force to the surrounding area. This rapid expansion inflicts most of the damage caused by the explosion. It also creates a very low-pressure area around the origin of the explosion as the rapid outward movement of gases creates a partial vacuum. After the initial outward blast, gases rush back into this vacuum, creating a second, less destructive inward energy wave.
C-4 is very stable and insensitive to most physical shocks. It cannot be detonated by a gunshot or by dropping it onto a hard surface. It also does not explode when set on fire or exposed to microwaves. Instead, detonation can only be initiated by a shockwave, such as the firing of a detonator inserted into the C-4.
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Burning C-4 produces poison
C-4, or Composition C-4, is a plastic explosive that is widely used in both military and civilian contexts. It is composed of explosives, a plastic binder, a plasticizer, and usually a marker or odorizing taggant chemical. C-4 has a putty-like texture and can be easily moulded into any desired shape, making it versatile for various applications.
The toxicity of C-4 is an important consideration, especially for those who work with or are exposed to this explosive. While C-4 is relatively stable and insensitive to most physical shocks, it is crucial to understand the potential risks associated with its use and misuse. Proper safety measures and handling procedures must be followed to minimize the risk of accidental exposure to its poisonous fumes.
The detection of C-4 can be achieved through various methods, including explosive vapor detectors, optical microscope examination, scanning electron microscopy, chemical spot tests, and thin-layer chromatography. These techniques help identify C-4 before detonation and trace residue after an explosion.
In summary, burning C-4 does produce poisonous fumes, and it is essential to approach this explosive with caution. The toxicity of C-4 has been a concern, especially during the Vietnam War when it was used as a heating fuel by soldiers. The detection and identification of C-4 are crucial aspects of ensuring safety and mitigating potential risks associated with its use.
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Detonation by gunshot
Plastic explosives are soft and hand-mouldable solid forms of explosive material. They are commonly used for explosive demolition and shock-hardening high-manganese percentage steel. Plastic explosives are not detonated by a gunshot or by dropping them onto a hard surface. They are also not detonated by fire or exposure to microwaves.
C-4, a common variety of plastic explosives, is manufactured by combining ingredients with binders dissolved in a solvent. The final material is a solid with a dirty white to light brown colour, a putty-like texture, and a distinct smell of motor oil. C-4 is relatively insensitive and can only be detonated by a shockwave, such as when a detonator inserted into it is fired.
Tests conducted by the U.S. military, referred to as "the rifle bullet test", confirmed that C-4 does not explode when shot at. In these tests, only 20% of the vials containing C-4 burned, and none exploded. While C-4 passed the Army's bullet impact and fragment impact tests at ambient temperature, it failed the shock stimulus, sympathetic detonation, and shaped charge jet tests.
To detonate C-4, a minimum initiating charge of 0.2 grams of lead azide or 0.1 grams of tetryl is required.
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Frequently asked questions
Plastic explosives are detonated using a smaller explosive, known as a detonator, which is relatively easy to trigger. This creates a shockwave that sets off the plastic explosive.
A detonator is a small amount of explosive material that is triggered by an electrical charge or a blasting cap.
No, C-4 is very stable and insensitive to most physical shocks. It cannot be detonated by a gunshot or by dropping it onto a hard surface.
When C-4 is detonated, it rapidly decomposes to release nitrogen, water, carbon oxides, and other gases. The gases expand at an explosive velocity of 8,092 m/s (26,550 ft/s), applying a huge amount of force to the surrounding area.
