Explosives

1. RECENT TRENDS IN EXPLOSIVES AND EXPLOSION RESIDUEANALYSIS Dr. T. R.Baggi, Dir. (Retd.)CFSL Hyd. & Acad. Coordinator (FS) Osmania Univ., Hyd. trbaggi@hotmail.com09246212364

2. Explosives • Explosives are substances that undergo a rapid oxidation reaction with the production of large quantities of gases. • It is the sudden buildup of gas pressure that constitutes the nature of explosion. • The speed at which explosives decompose permit their classification as high or low explosives.

3. Explosives • Explosives are solid or liquid substances, alone or mixed with one another, which are in a metastable state and are capable, for this reason, of undergoing a rapid chemical reaction with out the participation of external reactants such as atmospheric oxygen.

4. Explosives • The reaction can be initiated by mechanical means (impact / friction), by the action of heat (sparks / open flame / red hot or white hot objects) or by detonating shock (blasting cap with or without a booster charge)

5. Explosives • The resistance of the metastable state to heat is known as stability. The ease with which the chemical reaction can be initiated is known as sensitivity. • The reaction products are predominantly gaseous.

6. Explosion • Chemical Explosion is a chemical reaction in which: • Gas is released • Energy is released • 1 & 2 are released very rapidly

7. Explosion • Chemical reaction or change of state effected in an exceedingly short period of time with the generation of a high temperature and generally a large quantity of gas. An explosion produces a shock wave in the surrounding medium.

8. Explosion • A detonation is a confined explosion, occurring eg. In a closed chamber where volume is constant. An unconfined explosion is an explosion occuring in the open air where the (atmospheric) pressure is constant.

9. Explosions • The most widely used explosives in low explosive group are black powder and smokeless powder. • Black powder is a mixture of potassium or sodium nitrate, charcoal and sulphur. • Smokeless powder consists of nitrocellulose (SB) or nitrocellulose and nitroglycerine (DB)

10. Explosions • Among the high explosives, primary explosives are ultrasensitive to heat, shock, or friction and provide the major ingredients found in blasting caps or primers used to detonate other explosives.

11. Explosions • Secondary explosives are relatively insensitive to heat, shock, or friction and will normally burn rather than detonate if ignited in small quantities in the open air. • This group comprises the majority of commercial and military blasting, such as dynamite, TNT, PETN, and RDX.

12. Explosives • By the definition of explosion we can describe an explosive which is: • Capable of producing gas • Capable of producing energy • 1 & 2 must occur rapidly • 1, 2 & 3 self sustaining

13. Classification of explosives • Explosives: • Physical: Mechanical such as gas cylinder burst, compressor explosions etc. • Chemical: Explosive substances called as chemical explosives • Atomic: Fission

14. Classification contd. • Explosive substances: • Chemical explosives(including pyrotechnic compositions) 1. Primary Explosives: Lead azide, Mercury fulminate, Lead styphnate & Diazonitro- phenol 2. Secondary Explosives: a) Military Explosives:

15. Classification contd. TNT, RDX, PETN, Tetryl b) Commercial Explosives: Gelatines, powders, Permitted explosives, ANFO, Emulsions & Slurries 3. Propellants: a) Gun propellants: Black powder, Single base, double base and triple base powders b) Rocket propellants: Double base composite, Liquid fuels & oxidizers

16. Classification of explosives (contd.) • Explosives: • 1. CHEMICAL STRUCTURE: a) Organic nitro explosives: Nitro aromatics: 2,4, DNT, 2,4,6 TNT & picric acid b) Nitrate esters: EGDN, NG, PETN & NC c) Nitramines: RDX, HMX d) Organic peroxides:

17. Classification of explosives (contd.) TATP, HMTD e) Inorganic salts: Ammonium nitrate f) Mixtures of oxidizing & reducing substances: Black powder, Pot. Chlorate + sugar, Pot. Chlorate + Arsenic sulphide / Antimony sulphide / pot. Permanganate etc. g) Other compounds: Sensitizers, Desensitizers, Stabilizers (Diphenylamine, ethyl centralite), plastisizers (pthalate and sebaceate esters) & other compounds

18. Classification of explosives (Contd.,) • 2. USE: • Military explosives: TNT, PETN, RDX, Tetryl • Industrial explosives: Dynamites, AN, Emulsions • Improvised explosive devices: TATP, HMTD, Chlorate-sugar, chlorate-As. Sulphide mixtures

19. Classification of explosives (Contd.,) • 3. PLACE IN THE DETONATION CHAIN: • Primary explosives: Lead azide, Mercury fulminate, Lead styphnate, Diazonitrophenol • Boosters: PETN • Main charge: TNT, RDX

20. Classification of explosives (Contd.,) • 4. EXPLOSIVE PROPERTIES: a) High explosives: PETN,RDX b) Low explosives(Propellants): Black powder, Smokeless powders

21. Deflagration • Explosive materials often decompose at a rate much below the sonic velocity of the material with out requiring any introduction of atmospheric oxygen. This type of reaction is known as deflagration. It is propagated by the heat of reaction.

22. Deflagration • Slower (than 1500 m/s) explosive reactions, which are propagated by thermal conduction and radiation are known as deflagration. • The direction of flow of the reaction products is opposite to that of decomposition propagation. The burning of the powder or of a rocket charge is a deflagration process.

23. Detonation • Detonation is a chemical reaction given by an explosive substance in which produces a shock wave. High temperature and pressure gradienta are generated in the wave front, so that the chemical reaction is initiated instantaneously. Detonation velocities lie in the approximate range of 1500 – 9000 m / s.

24. Explosive train • A train of combustible and explosive elements arranged in order of decreasing sensitivity. The explosive train accomplishes the controlled augmentation of a small impulse into one of suitable energy to actuate main charge.

25. Shock wave • Intense compression wave produced by detonation of explosive is called a shock wave.

26. Present Scenario • Explosives are basically manufactured for industrial, commercial and military purposes. At one time the, military power, industrial prosperity & development of a nation was measured in terms of the tonnage of explosives produced by it.

27. Present Scenario • The misuse and abuse of explosives for other than the above purposes for criminal and terrorist activity in the recent years killing large number of people and destroying properties has necessitated the development of sophisticated and sensitive analytical methodologies for law enforcement agencies and criminal justice system. These methods also look into preemptive and preventive measures to detect hidden explosives before the criminal acts.

28. Examination of Explosives • To confirm the identity of suspect explosive • To compare an explosive with the explosive with the suspect/s • To identify the material involved in explosion (accidental, criminal, intentional) • To reconstruct the Improvised Explosive Device

29. EXPLOSIVES INTACT: Recovery of stolen explosives Undercover purchase Disarmed live explosive Hoax device POST EXPLOSION RESIDUES: Debris of accidental explosion Debris of criminal bombing Debris of intentional detonation

30. TYPES OF EXPLOSIVES • Explosives are classified as high and low explosives based on their speed of decomposition. • In a low explosive, this speed is called the speed of deflageration (burning). Characterized by very rapid oxidation that produces heat, light and a substance pressure wave.

31. TYPES OF EXPLOSIVES In a high explosive, it is called the speed of detonation. Detonation refers to the creation of a supersonic shock wave within the explosive charge. This leads to the new instantaneous build up of heat and gases.

32. TYPES OF EXPLOSIVES • LOW EXPLOSIVES (Propellants) • 400 M/sec, 30,000 lbs/sq’’ Black powder (Pot. Nitrate, carbon & sulphur (75:15:10) Pyrodex (KNO3 replaced with KClO4) Smokeless powder (SB) – NC Smokeless powder (DB)–NC+NG ANFO (95:5) Improvised (ClO4 or ClO3+Sugar) Flash powder (KClO4, Al, S or Sb2S3) Pyrotechnics (Ba, Sr,Al, Mg)

33. HIGH EXPLOSIVES They detonate almost instantaneously at rate of 1000-8500M/sec & Million lbs/ sq”. Two groups: Primary and Secondary based on their sensitivity to heat shock or friction.

34. HIGH EXPLOSIVES Primary explosives are easily detonated by heat, shock and friction. Secondary explosives are relatively insensitive to heat, shock, or friction. PRIMARY EXPLOSIVES: Detonate violently They are used to detonate other explosives through a chain reaction and are often referred to as primers. The major ingredients of blasting caps and include lead azide, lead styphnate, mercury fulminate and diazonitrophenol. Rarely used in homemade / IEDs / country bombs.

35. HIGH EXPLOSIVES SECONDARY EXPLOSIVES: Detonate when ignited in small quantities in open air. This group contains most high explosive used to commercial and military blasting. Examples: Dynamite, TNT, PETN, RDX, and tetryl. COMMERCIAL: Dynamites Water gels / emulsions Binaries (PE,Semtex,Detasheet)

36. HIGH EXPLOSIVES MILITARY: TNT RDX, HMX Combinations (Including PETN, Tetryl etc) IEDs (Triacetone peroxide, Chlorate - Nitrobenzene)

37. Dynamite • Swedish Chemist Alfred Nobel created “pulp” dynamite • Straight dynamites are used when a quick shattering action is desired. • Made with NG, pulp, sodium nitrate, and a small amount of stababilizer, such as calcium carbonate. • All straight dynamites are arated by strength; the strength rating is determined by the wt % of NG in the formula

38. Ammonium Nitrate Explosives: • Oxygen rich ammonium nitrate is mixed with fuel to form low cost and very stable explosive. • Water gels, emulsions, & ANFO explosives. They have consistency of jello or gel tooth paste. They are water resistant and are used for blasting under water in wet conditions.

39. Emulsions: Two phases – oil and water Contains microspheres of glass,resin, or ceramic and their size determines the explosive’s sensitivity and detonation velocity. ANFO: Ammonium nitrate soaked in fuel oil. Fertilizer grade ammonium nitrate is being used for home bombs.

40. TATP • Homemade explosive used by terrorists in many countries. • It consists of mixture of acetone, hydrogen peroxide and an acid. • Friction and impact sensitive explosive. • Extremely potent when confined (Pipe) • 2oo5 London bombings were TATP

41. Liquid explosives • Only about a dozen are liquid, most are solid. • Most are some form of peroxide explosive • Others are made from nitroglycerine and nitromethane (the fuel of drag race cars) • Research is going on to to detect liquid explosives rapidly and effeciently at airports.

42. Military High Explosives • RDX: • The most popular and powerful military explosive. • Often encountered in the form of a pliable plastic or dough like consistency known as composition- C4 or plastic explosive. • TNT: • It was produced and used in WWII. • It is used in shells, bombs, grenades, demolition explosives, & propellent compositions. • PETN: • Used as explosive core in detonating cord. • Used to connect a series & detonate simultaneously.

43. DETONATORS • In most cases detonators are blasting caps made of copper or aluminum cases filled with lead azide and PETN or RDX as a detonating charge. • IED’s or home made bombs camouflaged in packages, suitcases, etc. are usually initiated with an electrical blasting cap wired to a battery. • Clocks, mercury switches, and cars are also used as electrical source.

44. The Explosive Market • In recent years NG based dynamite is disappearing and is replaced by AN based explosives. (Water gels, emulsions and ANFO) • In many countries the accessibility of military HE to terrorist organizations make them very common constituents of IEDs. • RDX is the most popular and powerful of the military explosives, often encountered in the form of pliable plastic known as C-4

45. Collection and analysis • The entire bomb site must be systematically searched with great care given to recovering any trace or detonating mechanism or any other item foreign to explosion site. • Objects located at or near the norigin of the explosion must be collected for laboratory examination. • Often a crater is located at the origin and loose soil and other debris must be preserved from its interior for laboratory analysis. • One approach for screening objects for explosive residues in the field or laboratory is the ion mobility spectrometer (IMS)

46. Collection and Analysis • Preliminary identification of an explosive residue is made by IMS by noting the time it takes the explosive to move through a tube. A confirmatory test must follow. • All materials collected for the examination by the laboratory must be placed in a sealed airtight containers and labeled with all pertinent information. • Debris and articles collected from different areas are to be packaged in separate air-tight containers. • It may be noted that some explosives can diffuse through plastic and contaminate nearby containers.

47. Analytical Methods • Analysis of live intact explosives • Analysis of explosion residues

48. Analysis of live intact explosives Extraction Qualitative: Spot tests, TLC, IR / Raman Spec, GC,HPLC,MS, GC-MS, LC-MS, IMS,NMR, XRD Quantification for purity and origin: UV-Vis, fluorescence, HPTLC, HPLC, SCFC, CE, Profiling: UV-Visible Spec., GC, HPLC

49. UV-Visible Spectroscopy Useful to a limited extent Purification necessary Many explosives do not exhibit absorbance in the UV region. Nitro aromatics can be analyzed. Some visible spectroscopic methods developed. Generally useful in the quality control and process control in the industry Replaced by superior chromatographic methods

50. Infrared Spectroscopy • IR Spectrum 4000 – 250Cm-1 • As a whole molecule FP below 1300 Cm-1 • Specific functional groups above 1500Cm-1 • Purification & Microdevices necessary • Nitro aromatics: C-NO2 stretching of NO2 1590 -1510 Cm-1 & 1390 – 1320 Cm-1 Aromatic ring 1560 – 1520 Cm-1 & 1370 – 1340 Cm-1 Dinitro: 1552 -1539 & 1567 – 1554 Cm-1 TNT: Strong bands at 1534 & 1354 Cm-1