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Samples of semtex and other plastic explosives

Semtex is a general-purpose plastic explosive containing RDX and PETN.[1] It is used in commercial blasting, demolition, and in certain military applications.

Semtex was developed and manufactured in Czechoslovakia, originally under the name B 1 and then under "Semtex" designation since 1964,[note 1] labeled as SEMTEX 1A, since 1967 as SEMTEX H and since 1987 as SEMTEX 10.

Originally developed for Czechoslovak military use and export, Semtex eventually became popular with terrorists because it was, until recently, extremely difficult to detect,[3] as in the case of Pan Am Flight 103.


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.[4]

Composition of Semtex[citation needed]
Compound Semtex 1A Semtex H Semtex 2P
PETN 76% 40.9% 58.45%
RDX 4.6% 41.2% 22.9%
binder styrene-butadiene 9.4% 9% 9.2%
plasticizer n-octyl phthalate, tributyl citrate 9% 7.9% 8.45%
antioxidant N-phenyl-2-naphthylamine 0.5% 0.5% 0.5%
Dye 0.5% Sudan IV (reddish brown to red) 0.5% Sudan I (red-orange to yellow) (brown)


Semtex was invented in the late 1950s by Stanislav Brebera and Radim Fukátko, chemists at VCHZ Synthesia, Czechoslovakia (now Czech Republic). The explosive is named after Semtín, a suburb of Pardubice where the mixture was first manufactured starting in 1964.[2] 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 being highly malleable; but it is usable over a greater temperature range than other plastic explosives, since it stays plastic between −40 and +60 °C. It is also waterproof. There are visual differences between Semtex and other plastic explosives, too: while 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, only approximately 10 tons of Semtex were produced annually, almost all for domestic use.[2] On December 21, 1988, 12 ounces (340g) of Semtex brought down a Boeing 747 over Lockerbie, Scotland killing all 259 aboard the aircraft and many on the ground, some bodies were never recovered.

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-dimethyl-2,3-dinitrobutane (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.[2] 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. According to the manufacturer, even this untagged Semtex can now be detected.[8] The shelf life of Semtex was reduced from ten 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.[9]

On 25 May 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.[10] 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.


  1. ^ Various sources state that production started in 1964 or 1966. Explosia's brief historical document states it was 1964,[2] 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 United States construction of C-4.


  1. ^ Pike, John. "Explosives - Compounds". Retrieved 7 December 2017.
  2. ^ a b c d "Explosia". Retrieved 7 December 2017.
  3. ^ Schubert, Hiltmar. Detection of Explosives and Landmines: Methods and Field Experience. pp. 93–101 ISBN 1-4020-0692-6
  4. ^ "Semtex" (PDF). Explosives. Mondial Defence Systems. Retrieved 2012-11-26.
  5. ^ "Explosia". Retrieved 7 December 2017.
  6. ^ Brown, G. I. (1998). The Big Bang: A History of Explosives. Sutton Publishing. ISBN 0-7509-1878-0. p. 165.
  7. ^ Arie Farnam, "Czechs try to cap plastic explosives sales", Christian Science Monitor, 26 February 2002
  8. ^ "Explosia". Retrieved 7 December 2017.
  9. ^ "Explosia". Retrieved 7 December 2017.
  10. ^ Sieveking, Paul. Strange Deaths: More Than 375 Freakish Fatalities, Barnes & Noble, 2000, pg. 88. ISBN 0-7607-1947-0

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