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Semtex

Semtex

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Encyclopedia
Semtex is a general-purpose plastic explosive
Plastic explosive
Plastic explosive is a specialised form of explosive material. It is a soft and hand moldable solid material. Plastic explosives are properly known as putty explosives within the field of explosives engineering....

 containing RDX
RDX
RDX, an initialism for Research Department Explosive, is an explosive nitroamine widely used in military and industrial applications. It was developed as an explosive which was more powerful than TNT, and it saw wide use in WWII. RDX is also known as cyclonite, hexogen , and T4...

 and PETN. It is used in commercial blasting, demolition
Demolition
Demolition is the tearing-down of buildings and other structures, the opposite of construction. Demolition contrasts with deconstruction, which involves taking a building apart while carefully preserving valuable elements for re-use....

, and in certain military
Military
A military is an organization authorized by its greater society to use lethal force, usually including use of weapons, in defending its country by combating actual or perceived threats. The military may have additional functions of use to its greater society, such as advancing a political agenda e.g...

 applications. Semtex became notoriously popular with terrorists
Terrorism
Terrorism is the systematic use of terror, especially as a means of coercion. In the international community, however, terrorism has no universally agreed, legally binding, criminal law definition...

 because it was, until recently, extremely difficult to detect, as in the case of Pan Am Flight 103
Pan Am Flight 103
Pan Am Flight 103 was Pan American World Airways' third daily scheduled transatlantic flight from London Heathrow Airport to New York's John F. Kennedy International Airport...

.

For its original military use it was manufactured under the name B 1. It has been manufactured under its current name since 1964, labeled as SEMTEX 1A, since 1967 as SEMTEX H and since 1987 as SEMTEX 10.

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
Explosive booster
An explosive booster acts as a bridge between a low energy explosive and a low sensitivity explosive such as TNT. It increases the explosive shockwave from an initiating explosive to the degree sufficient to detonate the secondary charge.Unlike C4 plastic explosive, not all explosives can be...

; a special assembly of PETN and wax inside the charge assures high reliability for detonating cord
Detonating cord
Detonating cord is a thin, flexible plastic tube filled with PETN . With the PETN exploding at a rate of approximately 4 miles per second, any common length of det cord appears to explode instantaneously...

 or detonator
Detonator
A detonator is a device used to trigger an explosive device. Detonators can be chemically, mechanically, or electrically initiated, the latter two being the most common....

. The H (or SE) variant is intended for explosion hardening
Hardening (metallurgy)
Hardening is a metallurgical and metalworking process used to increase the hardness of a metal. The hardness of a metal is directly proportional to the uniaxial yield stress at the location of the imposed strain...

.
|+ Composition of Semtex
! compound >
Semtex 1A Semtex H >-
| PETN
PETN
Pentaerythritol tetranitrate , also known as PENT, PENTA, TEN, corpent, penthrite , is the nitrate ester of pentaerythritol. Penta refers to the five carbon atoms of the neopentane skeleton.PETN is most well known as an explosive...

 
76% 40.9% >-
| RDX
RDX
RDX, an initialism for Research Department Explosive, is an explosive nitroamine widely used in military and industrial applications. It was developed as an explosive which was more powerful than TNT, and it saw wide use in WWII. RDX is also known as cyclonite, hexogen , and T4...

 
4.6% 41.2% >-
| binder
Binder (material)
-See also:*Adhesive or Glue*Cement*Paint...

 styrene-butadiene
Styrene-butadiene
Styrene-Butadiene or Styrene-Butadiene-Rubber is a synthetic rubber copolymer consisting of styrene and butadiene. It has good abrasion resistance and good aging stability when protected by additives, and is widely used in car tires, where it may be blended with natural rubber...

 
9.4% 9% >-
| plasticizer
Plasticizer
Plasticizers or dispersants are additives that increase the plasticity or fluidity of the material to which they are added; these include plastics, cement, concrete, wallboard, and clay. Although the same compounds are often used for both plastics and concretes the desired effects and results are...

 n-octyl phthalate, tributyl citrate 
9% 7.9% >-
| antioxidant
Antioxidant
An antioxidant is a molecule capable of inhibiting the oxidation of other molecules. Oxidation is a chemical reaction that transfers electrons or hydrogen from a substance to an oxidizing agent. Oxidation reactions can produce free radicals. In turn, these radicals can start chain reactions. When...

 N-phenyl-2-naphthylamine 
0.5% 0.5% >-
| Dye
Dye
A dye is a colored substance that has an affinity to the substrate to which it is being applied. The dye is generally applied in an aqueous solution, and requires a mordant to improve the fastness of the dye on the fiber....

 
0.5% Sudan IV
Sudan IV
Sudan IV is a lysochrome diazo dye used for the staining of lipids, triglycerides and lipoproteins on frozen paraffin sections. It has the appearance of reddish brown crystals with melting point 199 °C and maximum absorption at 520 nm.Sudan IV is one of the dyes used for Sudan staining. Similar...

 (reddish brown to red)
0.5% Sudan I
Sudan I
Sudan I , is a lysochrome, a diazo-conjugate dye with the chemical formula of 1-phenylazo-2-naphthol. Sudan I is a powdered substance with an orange-red appearance. The additive is mainly used to colour waxes, oils, petrol, solvents and polishes...

 (red-orange to yellow)
(brown)

History


Semtex was invented in the late 1950s by Stanislav Brebera
Stanislav Brebera
Stanislav Brebera is a Czech chemist.Brebera spent his career in Czechoslovakian state-hold Research Institute for Chemical Industry, currently Explosia Pardubice. In 1966 he developed plastic explosive Semtex....

, a chemist at VCHZ Synthesia, Czechoslovakia. The explosive is named after Semtín, a suburb of Pardubice
Pardubice
Pardubice is the capital city of the Pardubice Region and lies on the river Elbe, 65 miles east of Prague. Pardubice has an antique centre square and old town, with many restaurants that stay open until late in the evening. There is an old Tower and a recently renovated Castle...

 in the Czech Republic
Czech Republic
The Czech Republic is a landlocked country in Central Europe. The country is bordered by Poland to the northeast, Slovakia to the east, Austria to the south, and Germany to the west and northwest....

 where the mixture was first manufactured starting in 1964. The plant was later renamed to become Explosia a.s.
Explosia a.s.
Explosia a.s. is an explosives manufacturer in Semtín, a suburb of Pardubice in the Czech Republic. The company was established in 1920. Its most famous product is the Semtex malleable explosive, the name is formed as a combination of the first letters of the Semtín village and the company name....

, a subsidiary of Synthesia.

Semtex was very similar to other plastic explosives, especially C-4
C-4 (explosive)
C4 or Composition C4 is a common variety of the plastic explosive known as Composition C.-Composition and manufacture:C4 is made up of explosives, plastic binder, plasticizer and usually marker or odorizing taggant chemicals such as 2,3-dimethyl-2,3-dinitrobutane to help detect the explosive and...

, 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
North Vietnam
The Democratic Republic of Vietnam , was a communist state that ruled the northern half of Vietnam from 1954 until 1976 following the Geneva Conference and laid claim to all of Vietnam from 1945 to 1954 during the First Indochina War, during which they controlled pockets of territory throughout...

, which received 14 tons during the Vietnam War
Vietnam War
The Vietnam War was a Cold War-era military conflict that occurred in Vietnam, Laos, and Cambodia from 1 November 1955 to the fall of Saigon on 30 April 1975. This war followed the First Indochina War and was fought between North Vietnam, supported by its communist allies, and the government of...

. However, the main consumer was Libya
Libya
Libya is an African country in the Maghreb region of North Africa bordered by the Mediterranean Sea to the north, Egypt to the east, Sudan to the southeast, Chad and Niger to the south, and Algeria and Tunisia to the west....

; about 700 tons of Semtex were exported to Libya between 1975 and 1981 by Omnipol
Omnipol
Omnipol is a company based in Prague, Czech Republic, specialising in the trading of defence and aerospace equipment.-International sales:Omnipol acts as the intermediary in government-to-government sales of defence equipment, meeting the needs of air and ground forces in more than 60 countries...

. It has also been used by Islamic militants in the Middle East
Middle East
The Middle East is a region that encompasses Western Asia and Northern Africa. It is often used as a synonym for Near East, in opposition to Far East...

 and by the Provisional Irish Republican Army
Provisional Irish Republican Army
The Provisional Irish Republican Army is an Irish republican paramilitary organisation whose aim was to remove Northern Ireland from the United Kingdom and bring about a socialist republic within a united Ireland by force of arms and political persuasion...

 (IRA) and the Irish National Liberation Army
Irish National Liberation Army
The Irish National Liberation Army or INLA is an Irish republican socialist paramilitary group that was formed on 8 December 1974. Its goal is to remove Northern Ireland from the United Kingdom and create a socialist united Ireland....

 in Northern Ireland
Northern Ireland
Northern Ireland is one of the four countries of the United Kingdom. Situated in the north-east of the island of Ireland, it shares a border with the Republic of Ireland to the south and west...

.

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. , approximately only 10 tons of Semtex were produced annually, almost all for domestic use.

Also in response to international agreements, Semtex has a detection taggant
Taggant
A taggant can mean a radio frequency microchip used in automated identification and data capture . In such cases, electronic devices use radio waves to track and identify items, such as pharmaceutical products, by assigning individual serial numbers to the containers holding each product...

 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
DMDNB
DMDNB, or also DMNB, chemically 2,3-dimethyl-2,3-dinitrobutane, is a volatile organic compound used as a detection taggant for explosives, mostly in the United States where it is virtually the only such taggant in use. Dogs are very sensitive to it and can detect as little as 0.5 parts per billion...

 (3,4-dinitrohexane, DMDNB) or p-mononitrotoluene
Mononitrotoluene
Mononitrotoluene, or methylnitrobenzene or nitrotoluene , is a group of 3 organic compounds, a nitro derivative of toluene...

, which is used currently. According to the manufacturer, the taggant agent was voluntarily being added by 1991, years before the protocol signed became compulsory. 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
Shelf life
Shelf life is the length of time that food, drink, medicine, chemicals, and many other perishable items are given before they are considered unsuitable for sale, use, or consumption...

 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.

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
Suicide
Suicide is the act of intentionally causing one's own death. Suicide is often committed out of despair or attributed to some underlying mental disorder, such as depression, bipolar disorder, schizophrenia, alcoholism, or drug abuse...

 in the Priessnitz spa
Destination spa
A destination spa is a short term residential/lodging facility with the primary purpose of providing individual services for spa-goers to develop healthy habits. Historically many such spas were developed at the location of natural hot springs or sources of mineral waters...

 of Jeseník
Jeseník
Jeseník , Frývaldov until 1948 is a city and a district in the Olomouc Region of the Czech Republic.- Districts :* Bukovice * Dětřichov * Jeseník * Lázně Jeseník - History :...

. Šole, 63, was being treated there for depression
Clinical depression
Major depressive disorder is a mental disorder characterized by an all-encompassing low mood accompanied by low self-esteem, and by loss of interest or pleasure in normally enjoyable activities...

. 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.

Note


Various sources state that production started in 1964 or 1966. Explosia's brief historical document states it was 1964, 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
Vietnam
Vietnam – sometimes spelled Viet Nam , officially the Socialist Republic of Vietnam – is the easternmost country on the Indochina Peninsula in Southeast Asia. It is bordered by China to the north, Laos to the northwest, Cambodia to the southwest, and the South China Sea –...

 for a counterpart to the US
United States
The United States of America is a federal constitutional republic comprising fifty states and a federal district...

's construction of C-4
C-4 (explosive)
C4 or Composition C4 is a common variety of the plastic explosive known as Composition C.-Composition and manufacture:C4 is made up of explosives, plastic binder, plasticizer and usually marker or odorizing taggant chemicals such as 2,3-dimethyl-2,3-dinitrobutane to help detect the explosive and...

.

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