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 |
Antioxidant | N-phenyl-2-naphthalamine | same |
Plasticizer | n-octyl phthalate butyl citrate | same |
Binder | styrene-butadiene rubber | same |
The explosive is named after Semtin, a suburb of Pardubice in eastern Bohemia where the compound 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. The new explosive was widely exported, notably to the government of North Vietnam which received over 12 tonnes. However the main consumer was Libya, about 700 tonnes of Semtex were exported to Libya between 1975 and 1981 by Omnipol.
Exports fell after the name became closely associated with terrorist blasts and as of 2001 only around 10 tonnes of Semtex was produced annually, almost all for domestic use. Export of Semtex was progressively tightened and from 2002 all of Explosia's sales were controlled by a government ministry.
Also in response to international pressure, Semtex has ethylene glycol dinitrate added to produce a distinctive odour 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 a identifying metallic code.
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