Cyclotrimethylene trinitramine, also known as RDX, cyclonite, or hexogen, is an nitroamine and explosive material widely used by the military.

There are many interpretations of its acronym including (but not limited to) Royal Demolition eXplosive and Research Department Explosive. In fact the latter is nearest to the mark. New explosives were given an identification number preceded by the letters 'RD' indicating 'Research and Development'. For some reason, this explosive was unable to be given a number (the story goes that the department that issued the numbers had just blown itself up - but this may be apocryphal). Instead the letter 'X' was appended to indicate 'unknown' with the intention of adding the number later. Although a number was issued, the term 'RDX' stuck.

In its pure synthesised state it is a white crystalline solid. As an explosive it is usually used in mixtures with other explosives and plasticizers or desensitizers. It is stable in storage and is considered the most powerful and brisant of the military high explosives.

RDX forms the base for a number of common military explosives: Composition A (wax-coated, granular explosive consisting of RDX and plasticizing wax), composition A5 (mixed with 1.5% stearic acid), composition B (castable mixtures of RDX and TNT), composition C (a plastic demolition explosive consisting of RDX, other explosives, and plasticizers), composition D, HBX (castable mixtures of RDX, TNT, powdered aluminium, and D-2 wax with calcium chloride), H-6, Cyclotol and C-4.

Properties

It is a colourless solid, of density 1.82 g/cm³. It is obtained by reacting concentrated nitric acid on hexamine. It is a heterocycle and has the shape of a ring. It starts to decompose at about 170°C and melts at 204°C. Its structural formula is: hexahydro-1,3,5-trinitro-1,3,5-triazine or (CH₂-N-NO₂)₃

At room temperatures, it is a very stable product. It burns rather than explodes, and only detonates with a detonator, being unaffected even by small arms fire. It is less sensitive than pentaerythritol tetranitrate (PETN). However, it is very sensitive when crystalized, below −4°C.

Under normal conditions, RDX has a Figure of Insensitivity of 80.

The manufacture of RDX can easily pollute soil and groundwaters.

History

The discovery of RDX dates from the 1890s when a German (Hans Henning) offered it as a medicine. Its explosive properties were not recognized until 1920 (Herz?). In the 1920s RDX was produced by the direct nitration of hexamine. It was only in 1940 that an efficient production method was found, possibly at the McGill University Department of Chemistry (Meissner?). It was widely used during WW II, often in explosive mixtures with TNT such as Torpex (TNT (42%),RDX (40%) and aluminium (18%)). RDX was used in one of the first plastic explosives.

External links

Synthesis@wikibooks