C-4 (explosive)

C-4

Inserting blasting caps into blocks of C-4 explosive
Type High-yield chemical explosive
Place of origin United Kingdom
Service history
Used by United States
Wars Vietnam War
War on Terror
Production history
Designed 1956
Produced 1956–current
Variants PE-4, M112
Specifications (M112)
Weight 1.25 lb (0.57 kg)
Length 11 in (28 cm)
Width 2 in (5.1 cm)
Height 1.5 in (3.8 cm)
Filling RDX
Filling weight 91%
Detonation
mechanism
 PETN-based detonating cord
Blast yield High

C-4 or Composition C-4 is a common variety of the plastic explosive family known as Composition C. The British version of the explosive is known as PE-4 (Plastic Explosive). C-4 is composed of explosives, plastic binder, plasticizer to make it malleable, and usually a marker or odorizing taggant chemical.

C-4 has a texture similar to modeling clay and can be molded into any desired shape. C-4 is stable and an explosion can only be initiated by the combination of extreme heat and shock wave from a detonator.

Characteristics and uses

Composition

The Composition C-4 used by the United States Armed Forces contains 91% RDX ("Research Department Explosive", an explosive nitroamine), 5.3% dioctyl sebacate (DOS) or dioctyl adipate (DOA) as the plasticizer (to increase the plasticity of the explosive), 2.1% polyisobutylene (PIB, a synthetic rubber) as the binder, and 1.6% of a mineral oil often called "process oil." Instead of "process oil," low-viscosity motor oil is used in the manufacture of C-4 for civilian use.[1]

Technical data according to the Department of the Army follows.[2]

Theoretical maximum density of the mixture, grams per cubic centimeter 1.75
Nominal density, grams per cubic centimeter 1.72658
Heat of formation, calories per gram −32.9 to −33.33
Max heat of detonation with liquid water, kilocalories per gram 1.59 (6.7 MJ/kg)
Max heat of detonation with gaseous water, kilocalories per gram 1.40
Remains plastic with no exudation, Celsius −57 to +77
Detonation pressure with density of 1.58 grams per cubic centimeter, kilobars 275

Manufacture

C-4 is manufactured by combining the above ingredients with binder dissolved in a solvent. Once the ingredients have been mixed, the solvent is extracted through drying and filtering. The final material is a solid with a dirty white to light brown color, a putty-like texture similar to modeling clay, and a distinct smell of motor oil.[2][3][4]

Depending on its intended usage and on the manufacturer, there are differences in the composition of C-4. For example, a 1990 U.S. Army technical manual stipulated that Class IV composition C-4 consists of 89.9±1% RDX, 10±1% polyisobutylene, and 0.2±0.02% dye that is itself made up of 90% lead chromate and 10% lamp black.[2] RDX classes A, B, E, and H are all suitable for use in C-4. Classes are measured by granulation.[5]

The substitution of ethylene glycol (found in anti-freeze as used in automotive cooling systems) in place of the plastic binder prevents its freezing and the composition remains pliable under all environmental conditions.

The manufacturing process for Composition C-4 specifies that wet RDX and plastic binder are added in a stainless steel mixing kettle. This is called the aqueous slurry-coating process.[6] The kettle is tumbled to obtain a homogeneous mixture. This mixture is wet and must be dried after transfer to drying trays. Drying with forced air for 16 hours at 50 °C to 60 °C is recommended to eliminate excess moisture.[2]:198

Detonation

A detonation within a blast resistant trash receptacle using a large C-4 explosive charge.

C-4 is very stable and insensitive to most physical shocks. C-4 cannot be detonated by a gunshot or by dropping it onto a hard surface. It does not explode when set on fire or exposed to microwave radiation.[7] Detonation can only be initiated by a combination of extreme heat and a shockwave, such as when a detonator inserted into it is fired.[3] When detonated, C-4 rapidly decomposes to release nitrogen and carbon oxides as well as other gasses.[3] The gasses expand at an explosive velocity of 8,092 m/s (26,550 ft/s).[8] After the initial explosion, gasses rush back toward the center of the explosion causing a second, inward wave of energy.[3]

A major advantage of C-4 is that it can easily be moulded into any desired shape to change the direction of the resulting explosion.[3][9]

Form

C-4 packaged as standard size M112 demolition charges. Sometimes 16 blocks of M112 are used to create a M183 demolition charge assembly.

Military grade C-4 is commonly packaged as the M112 demolition block. The demolition charge M112 is a rectangular block of Composition C-4 approximately 2 inches by 1.5 inches and 11 inches long, weighing 1.25 lb (0.57 kg).[10][11] The M112 is wrapped in a sometimes olive color Mylar-film container with a pressure-sensitive adhesive tape on one surface.[12][13]

The M112 demolition blocks of C-4 are commonly manufactured into the M183 "demolition charge assembly",[11] which consists of 16 M112 block demolition charges and four priming assemblies packaged inside military Carrying Case M85. The M183 is used to breach obstacles or demolish large structures where larger satchel charges are required. Each priming assembly includes a five- or twenty-foot length of detonating cord assembled with detonating cord clips and capped at each end with a booster. When the charge is detonated, the explosive is converted into compressed gas. The gas exerts pressure in the form of a shock wave, which demolishes the target by cutting, breaching, or cratering.[10]

Other forms include the mine-clearing line charge (MICLIC) and M18A1 Claymore Mine.[6]

Safety

Composition C-4 exists in the US Army Hazardous Components Safety Data Sheet on sheet number 00077.[14]:323

Impact tests done by the US military indicate composition C-4 is less sensitive than composition C-3 and is fairly insensitive. The insensitivity is attributed to using a large amount of binder in its composition. A series of shots were fired at vials containing C-4 in a test referred to as "the rifle bullet test". Only 20 percent of the vials burned, and none exploded. While C-4 passed the Army's bullet impact and fragment impact tests at ambient temperature, it did in fact fail the shock stimulus, sympathetic detonation and shaped charge jet tests.[6]

Additional tests were done including the "pendulum friction test" which measured a five-second explosion temperature of 263 °C to 290 °C. The minimum initiating charge required is 0.2 grams of lead azide or 0.1 grams of tetryl.

The results of 100 °C heat test are: 0.13 percent loss in the first 48 hours, no loss in the second 48 hours, and no explosions in 100 hours. The vacuum stability test at 100 °C yields 0.2 cubic centimeters of gas in 40 hours. Composition C-4 is essentially nonhygroscopic.[2]

The shock sensitivity of C-4 can be further reduced by how fine the nitramine particles are. The finer they are the better they help to absorb and suppress shock. Using 3-nitrotriazol-5-one (NTO), or 1,3,5-triamino-2,4,6-trinitrobenzene (TATB) (available in two particle sizes (5 µm, 40 µm)), as a substitute for RDX, is also able to improve stability to thermal, shock, and impact/friction stimulus; however, TATB is not cost-effective, and NTO is more difficult to use in the manufacturing process.[6]

Sensitivity test values

Sensitivity test values reported by the US Army follow.[14]:311, 314

Impact test with 2 kilogram weight / PA APP (% TNT) >100
Impact test with 2 kilogram weight / BM APP (% TNT) NA
Pendulum friction test, percent explosions 0
Rifle bullet test, percent explosions 20
Explosion temperature test, Celsius 263 to 290
Minimum detonating charge, gram of lead azide 0.2
Brisance measured by Sand test (% TNT) 116
Brisance measured by plate dent test 115 to 130
Rate of detonation at density 1.59
Rate of detonation meters per second 8.040
Ballistic pendulum test percent 130

Source variation

C-4 produced for use by the U.S. military, commercial C-4 (also produced in the United States), and C-4 (otherwise known as PE-4) from England each have their own unique properties and are not identical. The analytical techniques of time-of-flight secondary ion mass spectrometry and X-ray photoelectron spectroscopy have been demonstrated to discriminate finite differences in different C-4 sources. Chemical, morphological structural differences, and variation in atomic concentrations are detectable and definable.[15]

Analysis

Toxicity

C-4 has toxic effects on humans when ingested. Within a few hours multiple generalized seizures, vomiting, and changes in mental activity occur.[16] A strong link to central nervous dysfunction is observed.[17] If ingested, patients may be administered a dose of active charcoal to absorb some of the toxins, and haloperidol intramuscularly and diazepam intravenously to help the patient control seizures until it has passed. RDX, the primary component of C-4, is known to be a possible human carcinogen.[18] However, ingesting small amounts of C-4 is not known to cause any long-term impediment.[19]

Investigation

Wrapping on packaged C-4 indicate that it has been tagged for easier detection. Even if no taggant is used, sophisticated forensic means can still be employed to identify the presence of C-4.

If C-4 is marked with a taggant, such as DMNB, it can be detected with an explosive vapor detector before it has been detonated.[20]

A variety of methods for explosive residue analysis may be used to identify C-4. These include optical microscope examination and scanning electron microscopy for unreacted explosive, chemical spot tests, thin-layer chromatography (TLC), X-ray crystallography, and infrared spectroscopy for products of the explosive chemical reaction. Small particles of C-4 may be easily identified by mixing with thymol crystals and a few drops of sulfuric acid. The mixture will become rose colored upon addition of a small quantity of ethyl alcohol.[21]

RDX has a high birefringence and the other components commonly found in C-4 are generally isotropic; this makes it possible for forensic science teams to detect trace residue on fingertips of individuals who may have recently been in contact with the compound. However, positive results are highly variable and the mass of RDX can range between 1.7 to 130 ng, each analysis must be individually handled using magnifying equipment. The cross polarized light images obtained from microscopic analysis of the fingerprint are analyzed with gray-scale thresholding[22] to improve contrast for the particles. The contrast is then inverted in order to show dark RDX particles against a light background. Relative numbers and positions of RDX particles have been measured from a series of 50 fingerprints left after a single contact impression.[23]

Military and commercial C-4 are blended with different oils. It is possible to distinguish these sources by analyzing this oil by high-temperature gas chromatography–mass spectrometry. The oil and plasticizer must be separated from the C-4 sample, typically by using a non-polar organic solvent such as pentane followed by solid phase extraction of the plasticizer on silica. This method of analysis is limited by manufacturing variation and methods of distribution.[1]

History

Development

C-4 is a member of the Composition C family of chemical explosives. Variants have different proportions and plasticisers and include composition C-2, composition C-3, and composition C-4.[24] The original material was developed by the British during World War II, and standardised as Composition C when introduced to US service. It was replaced by Composition C-2 around 1943, and later redeveloped around 1944 as Composition C-3. The toxicity of C-3 was reduced, the concentration of RDX was increased, it improved safety of usage and storage. Research on a replacement for C-3 was begun prior to 1950, but the new material, C-4, did not begin pilot production until 1956.[14]:125 C-4, was submitted for patent as "Solid Propellant and a Process for its Preparation" March 31, 1958 by the Phillips Petroleum Company.[25]

Vietnam War

American soldiers during the Vietnam War era would sometimes use small amounts of C-4 as a fuel for heating rations as it will deflagrate unless detonated with a primary explosive.[3] However, burning C-4 produces poisonous fumes and soldiers are warned of the dangers of personal injury when using the plastic explosive.[26]

Amongst field troops in Vietnam it became common knowledge that ingestion of a small amount of C-4 would produce a "high" similar to that of ethanol.[19] Others would ingest C-4, commonly obtained from a Claymore mine, to induce temporary illness in hopes of being sent on sick leave.[27]

Use in terrorism

Terrorist groups have used C-4 worldwide. C-4 has been used in terrorism and insurgency related to Middle Eastern crises, but also in domestic terrorism and state terrorism.

Composition C-4 is recommended in Al-Qaeda’s traditional curriculum of explosives training.[4] In October 2000, the group used C-4 to attack the USS Cole, killing 17 sailors.[28] In 1996, Saudi Hezbollah terrorists used C-4 to blow up the Khobar Towers, a U.S. military housing complex in Saudi Arabia.[29] Composition C-4 has also been used in improvised explosive devices by Iraqi insurgents.[4]

Homemade C-4 is a popular subject amongst domestic anarchist terrorists in the United States[30] and is the subject of a chapter in the original The Anarchist Cookbook which details how to separate RDX from Composition-4.[31] Ammonium nitrate is referenced as the anarchists "homemade C-4" and many do-it-yourself books list several explosive formulations derived from it with detailed instructions as to the proper grade of AN to purchase. Prepared by reacting ammonia and nitric acid, it is widely available to the public as a fertilizer. In 1986 over 11 billion pounds of ammonium nitrate were produced in the U.S.[32]

In 1987, North Korean agents used C-4 as part of their operation to bomb Korean Air Flight 858.[33]

See also

References

  1. 1 2 Reardon, Michelle R.; Bender, Edward C. (2005). "Differentiation of Composition C4 Based on the Analysis of the Process Oil". Journal of Forensic Sciences (Ammendale, MD: Bureau of Alcohol, Tobacco, Firearms, and Explosives, Forensic Science Laboratory) 50 (3): 1–7. doi:10.1520/JFS2004307. ISSN 0022-1198.
  2. 1 2 3 4 5 Headquarters, U.S. Department of the Army (25 Sep 1990), Department of the Army Technical Manual – Military Explosives (PDF).
  3. 1 2 3 4 5 6 Harris, Tom. "How C-4 Works". How Stuff Works. HowStuffWorks. Retrieved 14 July 2014.
  4. 1 2 3 "Introduction to Explosives" (PDF). C4: Characteristics, Properties, and Overview. U.S. Department of Homeland Security. pp. 4–5. Retrieved 18 July 2014.
  5. ↑ Headquarters, U.S. Department of the Army (25 Sep 1990), Department of the Army Technical Manual – Military Explosives (PDF), pp. 8–37–38 (124–125).
  6. 1 2 3 4 Owens, Jim. "Recent Developments in Composition C-4: Towards an Alternate Binder and Reduced Sensitivity" (PDF). Holston Army Ammunition Plant: BAE Systems OSI.
  7. ↑ Nagy, Brian. "Grosse Point Blank Microwave C4 Mercury Switch". Carnegie Mellon University. Retrieved 14 July 2014.
  8. ↑ "C4 product page". Ribbands Explosives.
  9. ↑ Nordin, John. "Explosives and Terrorists". The First Responder. AristaTek. Retrieved 14 July 2014.
  10. 1 2 Pike, J. "Explosives - Compositions". GlobalSecurity.org. Retrieved 14 July 2014.
  11. 1 2 Use of Mine, Antitank: HE, Heavy, M15 as a Substitute for Charge Assembly Demolition, M37 Or M183. Headquarters, Department of the Army. 1971.
  12. ↑ "M112" (PDF). American Ordnance. Retrieved 19 July 2014.
  13. ↑ "Military Explosives". ATF Law Enforcement Guide to Explosives Incident Reporting (PDF). Bureau of Alcohol, Tobacco, Firearms, and Explosives. Retrieved 15 July 2014.
  14. 1 2 3 Headquarters, U.S. Department of the Army (25 Sep 1990), Department of the Army Technical Manual – Military Explosives (PDF), pp. A–13 (323).
  15. ↑ Mahoney, Christine M.; Fahey, Albert J.; Steffens, Kristen L.; Benner, Bruce A.; Lareau, Richard T. "Characterization of Composition C4 Explosives using Time-of-Flight Secondary Ion Mass Spectrometry and X-ray Photoelectron Spectroscopy". Analytical Chemistry 82 (17): 7237–7248. doi:10.1021/ac101116r.
  16. ↑ Stone, William J.; Paletta, Theodore L.; Heiman, Elliott M.; Bruce, John I.; Knepshield, James H. (December 1969). "Toxic Effects Following Ingestion of C4 Plastic Explosive". Arch Intern Med 124 (6): 726–730. doi:10.1001/archinte.1969.00300220078015.
  17. ↑ Woody, Robert C.; Kearns, Gregory L.; Brewster, Marge A.; Turley, Charles P.; Sharp, Gregory B.; Lake, Robert S. (1986). "The Neurotoxicity of Cyclotrimethylenetrinitramine (RDX) in a Child: A Clinical and Pharmacokinetic Evaluation". Clinical Toxicology 24 (4): 305–319. doi:10.3109/15563658608992595.
  18. ↑ http://cira.ornl.gov/documents/RDX.pdf
  19. 1 2 K Fichtner, MD (May 2002). "A plastic explosive by mouth". Journal of the Royal Society of Medicine (U.S. Army Hospital, Camp Bondsteel, Kosovo) 95 (5): 251–252. doi:10.1258/jrsm.95.5.251. C4 contains 90% cyclotrimethylenetrinitramine (RDX)
  20. ↑ Committee on Marking, Rendering Inert, and Licensing of Explosive Materials; National Research Council; Division on Engineering and Physical Sciences; Commission on Physical Sciences, Mathematics, and Applications (27 May 1998). Containing the Threat from Illegal Bombings:: An Integrated National Strategy for Marking, Tagging, Rendering Inert, and Licensing Explosives and Their Precursors. National Academies Press. p. 46. ISBN 978-0-309-06126-1.
  21. ↑ Allman, Jr., Robert. "Explosives". http://chemstone.net. Retrieved 19 July 2014. External link in |website= (help)
  22. ↑ Brown, Lew. "Thresholding in Imaging Particle Analysis (A four part series)" (PDF). http://www.particleimaging.com. ParticleImaging.com. Retrieved 19 July 2014. External link in |website= (help)
  23. ↑ Verkouteren, Jennifer R.; Coleman, Jessica L.; Cho, Inho. "Automated Mapping of Explosives Particles in Composition C-4 Fingerprints" (PDF). Journal of Forensic Sciences 55 (2): 334–340. doi:10.1111/j.1556-4029.2009.01272.x.
  24. ↑ Rudolf Meyer, Josef Köhler, Axel Homburg (Sep 2007). Explosives. Wiley-VCH. p. 63. ISBN 978-3-527-31656-4.
  25. ↑ D, G.E. "US Patent 3,018,203". Google Patents. Retrieved 15 July 2014.
  26. ↑ "Chapter 1: Military Explosives". FM 3-34.214 (FM 5-250) Explosives and Demolitions (PDF). Washington, DC: U.S. Department of the Army. 27 August 2008. p. 6. Composition C4 explosive is poisonous and dangerous if chewed or ingested; its detonation or burning produces poisonous fumes.
  27. ↑ Herr, Michael (1977). Dispatches. Knopf. ISBN 9780679735250.
  28. ↑ Whitaker, Brian (21 August 2003). "Bomb type and tactics point to al-Qaida". The Guardian (London: Guardian Media Group). Retrieved July 11, 2009.
  29. ↑ Ashcroft, John (21 June 2001). "Attorney General, on Khobar Towers Indictment" (Press release).
  30. ↑ "4 anarchists sentenced in Cleveland bridge bomb plot". Dec 6, 2012. Retrieved 16 July 2014.
  31. ↑ Bergman, William Powell. With a prefatory note on anarchism today by P. M. (2002). "137 Reclamation of RDX from C-4 Explosives". The Anarchist Cookbook. El Dorado, Ariz.: Ozark Press. ISBN 0-9623032-0-8.
  32. ↑ Oxley, Jimmie C. NON-TRADITIONAL EXPLOSIVES: POTENTIAL DETECTION PROBLEMS (PDF). Kingston, RI: Department of Chemistry, University of Rhode Island. pp. 6–7. Retrieved 18 July 2014.
  33. ↑ McBeth, John (March 12, 2014). "Asia's long history of carnage in the air". Asia Times Online. Retrieved July 20, 2014.

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