Semtex
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Semtex is a general-purpose plastic explosive.
First made by the Semtín East Bohemian Chemical Works (then called VCHZ Synthesia, now called Explosia [1]) in Semtín (a suburb of Pardubice) in the Czech Republic), it is used in commercial blasting, demolition, and in certain military applications. Semtex became notoriously popular with terrorists because it was, until recently, extremely difficult to detect .[2], as in the case of Pan Am Flight 103.
[edit] Composition, manufacture and use
There are two common varieties, A for blasting and H (or SE) for hardening:
| Semtex H | Semtex A | |
| PETN | 49.8 % | 94.3 % |
| RDX | 50.2 % | 5.7 % |
| Dye | Sudan I (red-orange) | Sudan IV (reddish brown) |
| Antioxidant | N-phenyl-2-naphthylamine | 1% |
| Plasticizer | di-n-octyl phthalate, tri-n-butyl citrate | 9% |
| Binder | styrene-butadiene rubber | 9,4% |
A variant called Semtex 10SE is sold in the form of a thin sheet usually 2mm thick which is sandwiched between two plastic sheets and rolled onto a spool, 10SE is bright white with an almost translucent appearance. Its intended use is for hardening of mangenese steel.
The explosive is named after Semtín, a suburb of Pardubice Czech Republic where the mixture was first manufactured. It was invented in 1966 by Stanislav Brebera, a chemist at VCHZ Synthesia. It was like other plastic explosives, especially C-4, in that it was easily malleable; but it was usable over a greater temperature range than other types. There are also visual differences: whereas C-4 is off-white in colour, Semtex is brick-orange.
The new explosive was widely exported, notably to the government of North Vietnam, which received 14 tonnes during the Vietnam War. However, the main consumer was Libya; about 700 tonnes 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 republican paramilitaries such as the Provisional Irish Republican Army (IRA) and Irish National Liberation Army in Northern Ireland.
Exports fell after the name became closely associated with terrorist blasts. As of 2001, approximately only 10 tonnes of Semtex were produced annually, almost all for domestic use. Export of Semtex was progressively tightened and since 2002 all of Explosia's sales were controlled by a government ministry.
Also in response to international pressure, Semtex has ethylene glycol dinitrate added as a detection taggant to produce a distinctive vapor signature to aid detection. Efforts have also been made to reduce the shelf life of Semtex from its current 20 years to three or even less but have proved difficult, and all new supplies contain an identifying metallic code.
On May 25, 1997 Bohumil Sole, 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. Sole, 63, was being treated there for depression. Twenty other people were hurt in the explosion, while six were seriously injured. It should be noted, however, that the manufacturer, Explosia, states that he was not a member of the team that developed the explosive.
Semtex is now manufactured by the Czech company Explosia a.s. [3] (about 10 tonnes per year).
