Devastating Power: Plastic Explosives' Potential

Plastic explosives are soft and hand-mouldable solid explosives. They are often used for explosive demolition and are well-suited to combat engineering tasks. The first plastic explosive was gelignite, invented by Alfred Nobel in 1875. Since then, a variety of plastic explosives have been developed, including C-4, Semtex, and Nobel 808. One of the most powerful plastic explosives is Semtex, which contains PETN, a highly energetic compound that has been used in numerous terrorist attacks. PETN is difficult to detect because it does not readily vaporize and has a low vapor pressure, making it hard for bomb-sniffing dogs to identify.

Pentaerythritol tetranitrate (PETN)

PETN is a secondary explosive, meaning it is relatively difficult to detonate. For example, dropping or igniting it will not typically cause an explosion. However, it is more sensitive to shock and friction than other secondary explosives such as TNT or tetryl. It is also very stable and has a low toxicity, making it safer to handle than other explosives.

PETN is manufactured as a powder or as thin plasticized sheets (e.g. Primasheet 1000 or Detasheet). It is often phlegmatized by adding wax or polymers, which make it suitable for use in cannon shells and rocket propellants. It can also be mixed with other explosives to form castable mixtures, as it cannot be cast on its own.

PETN residues are easily detectable in the hair of people handling it, even after washing. This makes it possible to identify those who have been in contact with the explosive. PETN is also detectable using chemical sensors, X-rays, infrared, microwaves, and terahertz technology.

In addition to its explosive properties, PETN is used medically as a vasodilator in the treatment of heart conditions. The heart medicine Lentonitrat is nearly pure PETN.

Semtex

Due to its association with terrorist attacks, sales of Semtex declined, and rules governing its export were tightened. In 2002, all of Explosia's trading (the plant where Semtex was manufactured, previously known as VCHZ Synthesia) began to be controlled by a government ministry, and only around 10 tons of Semtex were produced annually, almost entirely for domestic use. In response to international agreements, Semtex now has a detection taggant added to produce a distinctive vapour signature to aid detection.

C-4

The insensitivity of C-4 is due to the large amount of binder used in its composition. It passed the U.S. Army's bullet impact and fragment impact tests at ambient temperature but failed the shock stimulus, sympathetic detonation, and shaped charge jet tests. Impact tests showed that C-4 is less sensitive than Composition C-3, with only 20% of vials containing C-4 burning when shot at, and none exploding. C-4 has a five-second explosion temperature of 263°C to 290°C and the minimum initiating charge required is 0.2 grams of lead azide or 0.1 grams of tetryl.

Gelignite

Prior to World War I, British explosives chemist Oswald Silberrad obtained patents for a series of plastic explosives called "Nitrols", composed of nitrated aromatics, collodion, and oxidising inorganic salts. However, the term "plastique" was introduced to the US by the British in 1940, referring to the Nobel 808 explosive. This explosive had the appearance and texture of green plasticine and a distinctive almond smell.

Today, there are various types of plastic explosives, such as Semtex and C-4, which are commonly used for military and commercial purposes. These explosives have improved temperature stability and handling properties compared to earlier versions.

RDX-based explosives

RDX, or Research Department Explosive as it was originally known, was first manufactured in 1933 at the Royal Arsenal in Woolwich, London. It was widely used during World War II, often in explosive mixtures with TNT, and was a key component in the first plastic explosives. RDX is still used as the base for a number of common military explosives, including Composition A and Composition B.

The production of RDX peaked in the 1960s when it was ranked third in explosive production by volume in the United States. Today, production of RDX in the US is limited to military use at the Holston Army Ammunition Plant in Kingsport, Tennessee.

RDX is one of the main ingredients in plastic explosives and is relatively easy to detect. Its high frequencies and short T1s make it one of the easiest explosives to identify. THz-TDS spectroscopy, for example, can be used to identify the spectral features of RDX, specifically the absorption peak at 0.8 THz.

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