RDX

Cyclotrimethylenetrinitramine, also known as RDX, cyclonite, hexogen, and T4, is an explosive nitroamine widely used in military and industrial applications. Nomenclature variants include Cyclotrimethylene-trinitramine and Cyclotrimethylene Trinitramine.

In its pure, synthesized state RDX 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 one of 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 C4.

RDX is also used as a major component of many plastic bonded explosives used in nuclear weapons.

Properties
The velocity of detonation of RDX at a density of 1.76 grams/cm³ is 8,750 meters per second.

It is a colourless solid, of maximum theoretical density 1.82 g/cm³. It is obtained by reacting concentrated nitric acid with hexamine.


 * (CH2)6N4 + 4HNO3 → (CH2-N-NO2)3 + 3HCHO + NH4+ + NO3-

It is a heterocycle and has the molecular 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 temperature, it is very stable. It burns rather than explodes and detonates only with a detonator, being unaffected even by small arms fire. It is less sensitive than pentaerythritol tetranitrate (PETN). However, it is very sensitive when crystallized, below &minus;4°C.

Under normal conditions, RDX has a Figure of Insensitivity of exactly 80 (as this is the reference point).

RDX sublimates in vacuum, which limits its use in pyrotechnic fasteners for spacecraft.

History
The discovery of RDX dates from the 1890s when a German (Hans Henning) offered it as a medicine. Its explosive properties were not discovered until 1920 (Herz?). In the 1920s RDX was produced by the direct nitration of hexamine.

RDX was used by both sides in World War II. In the United Kingdom RDX was manufactured in pilot plants at the RGPF Waltham Abbey in 1938 and at the Research Department at the Royal Arsenal, Woolwich. In 1939 a twin-unit industrial-scale plant was designed to be installed at a new site, ROF Bridgwater, away from London; and production of RDX started at Bridgwater in 1941. The United Kingdom attempted to be self-sufficient in the early stages of the war, and at this time the USA was still a neutral country; Canada, a member of the British Commonwealth, was looked upon to supply ammunition and explosives, including RDX. A slightly different method of production, but still using hexamine, was found and used in Canada, possibly at the McGill University Department of Chemistry (Meissner?). Urbanski provides details of five methods of production. The American Bachmann process for RDX was found to be richer in HMX than the United Kingdom's RDX and there is a suggestion that this later led to a HMX plant being set up at ROF Bridgwater in 1955.

RDX was widely used during World War II, often in explosive mixtures with TNT such as Torpex. RDX was used in one of the first plastic explosives. RDX is believed to have been used in many bomb plots including terrorist plots. It was said to have been used in the Bombay (Mumbai) serial bomb blasts of March 8, 1993 in which more than 300 people were killed and about 1500 injured. Again, on July 11, 2006, a series of powerful explosions took place on seven suburban railway trains on Mumbai's Western Railway line killing 209 and injuring over 700. The use of RDX by the Islamic terrorist outfit Lashkar-e-Toiba in this incident was subsequently confirmed by India's state investigating agencies. Besides these two incidents, RDX has been used in several other terrorist related explosions in India over the years.

There are many interpretations of its acronym including (but not limited to) Royal Demolition eXplosive, Research Department (composition) X and Research Department eXplosive. Research Department composition X is most likely correct. In the United Kingdom, new military explosives were given an identification number preceded by the letters 'RD' indicating 'Research Department No.'. 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.

The first public reference in the United Kingdom to the name RDX, or R.D.X to use the official title, appears in 1948; its authors were the Managing Chemist, ROF Bridgwater, the Chemical Research and Development Department, Woolwich, and the Director of Royal Ordnance Factories, Explosives; it is referred to as simply RDX. Davis, writing in the USA in 1943, stated that it was generally known in the USA as cyclonite; the Germans called it Hexogen and the Italians T4.