Composition
The composition of the two most common variants differ according to their use. The
1A (or
10) variant is used for
blasting, and is based mostly on crystalline
PETN. The version
1AP and
2P are formed as hexagonal
booster charges; a special assembly of PETN and wax inside the charge assures high reliability for
detonating cord or
detonator. The
H (or
SE) variant is intended for explosion
hardening.
[3]
[edit] History
Semtex was invented in the late 1950s by
Stanislav Brebera, a chemist at VCHZ Synthesia, Czechoslovakia. The explosive is named after Semtín, a suburb of
Pardubice in the
Czech Republic where the mixture was first manufactured starting in 1964.
[4] The plant was later renamed to become
Explosia a.s., a subsidiary of Synthesia.
[5]
Semtex was very similar to other plastic explosives, especially
C-4, in that it was easily
malleable; but it was usable over a greater temperature range than other plastic explosives, as it stays plastic between −40 and +60 °C; it is also waterproof. There are also visual differences: whereas C-4 is off-white in colour, Semtex is red or brick-orange.
The new explosive was widely exported, notably to the government of
North Vietnam, which received 14 tons during the
Vietnam War. However, the main consumer was
Libya; about 700 tons of Semtex were exported to Libya between 1975 and 1981 by
Omnipol. It has also been used by Islamic militants in the
Middle East and by the
Provisional Irish Republican Army (IRA) and the
Irish National Liberation Army in
Northern Ireland.
[6]
Exports fell after the name became closely associated with terrorist attacks. Export of Semtex was progressively tightened and since 2002 all of Explosia's sales have been controlled by a government ministry.
[7] As of 2001
[update], approximately only 10 tons of Semtex were produced annually, almost all for domestic use.
[4]
Also in response to international agreements, Semtex has a
detection taggant added to produce a distinctive vapor signature to aid detection. First,
ethylene glycol dinitrate was used, later switched to
2,3-dinitro-2,3-dimethylbutane (3,4-dinitrohexane, DMDNB) or
p-
mononitrotoluene, which is used currently. According to the manufacturer, the taggant agent was voluntarily being added by 1991, years before the protocol signed became compulsory.
[4] Batches of Semtex made before 1990, however, are untagged, though it is not known whether there are still major stocks of such old batches of Semtex. The
shelf life of Semtex was reduced from 10 years before the 1990s to five years now. Explosia states that there is no compulsory tagging allowing reliable post-detonation detection of a certain plastic explosive (such as incorporating a unique metallic code into the mass of the explosive), so Semtex is not tagged in this way.
[8]
On May 25, 1997,
Bohumil Šole, a scientist often said to have been involved with inventing Semtex, strapped the explosive to his body and committed
suicide in the
Priessnitz spa of
Jeseník.
[9] Šole, 63, was being treated there for
depression. Twenty other people were hurt in the explosion, while six were seriously injured. According to the manufacturer, Explosia, he was not a member of the team that developed the explosive.
Various sources state that production started in 1964 or 1966. Explosia's brief historical document states it was 1964,
[4] but most other credible sources state it was in 1966. Most of these also state that development was started at the same time, in response to a request from
Vietnam for a counterpart to the
US's construction of
C-4.