Explosives Final

Explosion

rapid reaction, violent expansion of gases, high temps and violent shocks

Mechanical explosion

gradual pressure buildup from heat and pressure, pressure overcomes structural integrity of container

Nuclear explosion

nuclear fusion or fission of atom

Chemical explosion

rapid conversion of reactants (typically solid or liquid) to products (typically gas)

Use of containers with chemical explosions

builds pressure (because gases take up more space) that creates a shockwave/ builds energy

Chemical explosives require what two ingredients?

Oxidizer and fuel

Oxidizer

provides O2, faster because don’t need to rely on air, -ates

Fuel

provides bonds to break and form to release energy

Deflagration

subsonic burn rate, needs to be in a container, lower explosives, particle to particle burning, pressure wave

Detonation

fuel and O2 source in same molecule, don’t need container, creates shockwave

Reaction rates

limited by how quickly fuel can come in contact with O2, effect of confinement and temp

subsonic

burn rate < 3300 ft/sec

supersonic

burn rate > 3300-30000 ft/sec

Pressure wave

air doesn’t act like a solid, wind, deflagration

Shockwave

compression of air to act like a solid, “solid air” acts like container, blows air and everything out to create a vacuum, lots of damage and blowback

Blast effects

fragmentation, pressure, thermal/ incendiary

Positive pressure phase

blowing out

Negative pressure phase

blowing inward because of vacuum

High order deflagration

complete burning or detonation at its max velocity

(only when all conditions are right, all reactant to product, no reactant left to analyze)

Low order deflagration

not a complete reaction, inadequate initiator, degraded explosive, poor contact, improper mixture of chemicals (analyze left behind unreacted reactants)

Most commonly seen elements in explosion reaction

carbon (ox#+4), hydrogen (+1 nonmetals), oxygen (-2), nitrogen (0), potassium (+1)

Compound with a net negative valence

oxidizing species

Compound with a net positive valence

fuel species

Oxidizing valences

reducing valences in a balanced equation for a net 0 (aka balancing equation based on compound valence numbers)

Maximum amount of energy comes from

oxygen balance equation

amount of energy released depends on

confinement, density, mode of initiation, fuel used, oxygen balanced combo of reactants

weight ratio equation for balanced eqt

total #grams reactant (account for #moles)/ total weight rea

Common sources of oxygen

Cl-O, N-O (-ates), highly electronegative atoms competing for electrons (very unstable)

What actually causes the release of energy

reactants decomposing to form more stable species (activation energy in to break, energy out to make more stable)

Sensitizer

catalyst, lowers activation energy and increases ease of initiation

Improvised explosives

combined chemicals or made device themself (e.g. pipe bomb)

Commercial explosives

high explosives used for mining, demolition, dynamite, fireworks

cost efficient, stable, hygroscopicity

Military explosives

high explosives, high rate and power of detonation, insensitive to impact and other triggers (for transport), use underwater, convenient creation

detonate by shock, need additional energy

Low explosives

particle to particle deflagration, mixtures, confine and ignite with flame, used as propellants to push not shatter

Low explosive examples

black powder (and substitutes), smokeless powder, pyrotechnics, flash powders

Black powder contents

15% carbon (charcoal), 10% sulfur, 75% nitrate (K or Na)

Black, irregular size/ shape, smaller size (FFFFg) burns faster

Black powder substitute contents

same as BP, also Ka Perchlorate, ascorbic acid, other additives

reduce sensitivity and increase efficiency with more energy

irregular and gray

(e.g. a lot of other brands like Pyrodex)

Smokeless powder

produce little ash and smoke, pressed into shapes, contains nitrocellulose for sure

Single base SP

only contains NC

Double base SP

NC and nitroglycerin

Triple base SP

NC, NG, nitroguanidine (flash suppressed, decreased burn temp)

SP additives

stabilizers, gelatinizing agents/ plasticizers, coating

Stabilizer

prevent decomposition of NC/NG via inc. activation energy

e.g. DPA

Gelatinizing agents/ plasticizers

prevents suspension of insoluble NC, reduces hygroscopicity, makes compressible

e.g. NG, phthalate plasticizer

Graphite coating affects

decreases static electricity to affect burn rate and dec. ignitability (more stable), improves flow, flash suppressant

e.g. graphite, zinc, vinsol

Flash powders

pyrotechnics, theatrical, fine metal particle (Al, Mg) and chlorate, perchlorate, nitrate (strong ox. agent)

very fast, bright flash

Pyrotechnic powders

oxidizer, fuel, regulator (affects rxn rate) (fine metals inc. brightness, cornmeal dec. rxn rate), binder (starch, organic), coloring agent (metal correlates to color given off when excited e relaxes)

Silver nitrate reacts with

chloride and carbonate (white ppt)

Ammonium hydroxide is used when?

added to silver nitrate

chloride dissolves

Barium chloride tests for

sulfate, nitrate and carbonate (white ppt)

Acetic acid is used when?

added to barium chloride

carbonate dissolves

DPA- yellow → blue

chlorate

DPA- blue (instant)

nitrate/ nitrite

What should carbonate do in MCT?

Effervesce

What does methlyene blue test for by turning purple?

Perchlorate

High explosive

confinement not necessary (air becomes wall), shock initiated detonation, brissance, fuel/ oxidizer chemical compounds

brissance

to shatter and destroy

affected by: speed of reaction/ detonation, loading density, heat generated and gas yield

Organic explosive examples

PETN, NG, NC, TNT, RDX (nitro groups)

Primer

High explosive, sensitive to shock, friction, heat; for detonation and initiation

Primer examples

lead azide, TATP (peroxide-based)

Peroxide-based

O-O is highly unstable, sensitive, reactive, easy to produce

no residue, just gas released, no large amt of heat

TATP

Secondary explosive

high explosive, non-initiating, needs a strong shockwave, main charge

Secondary examples

dynamite, ANFO, TNT, PETN

Straight dynamite

NG, NaNO3, CaCO3, absorbant

Ammonia dynamite

NG, NaNO3, CaCO3, absorbant, NH3NO3

Permissible dynamite

NG, NaCO3, CaCO3, absorbant, NH3NO3, NaCl

lower temp

gelatin dynamite

NG and NC, absorbant fillers, H2O resistant

Military dynamite

RDX, TNT, plasticizer, No NG

C4, cyclotol, SEMTEX, Torpex

EGDN

antifreeze for dynamite, to avoid sweating

C4

RDX, plasticizer, motor oil, binder

military, malleable, plastic explosive

PBX/ Plastic-bonded explosives

high explosive, binder, plasticizer

Plastic explosive

high explosive, plasticizer, malleable, putty, no hardened binder

Slurries/ water gels

AN, NO3, H2O, gelling agent, Al, sensitizer (varies by manufacturing)

Nitroglycerin

very sensitive, pulled out by water

ANFO

Ammonium nitrate (goes off by self) and fuel oil (desensitizes)

Insensitive, needs booster

Emulsions

Mix immiscible liquids, oxidizer drops (AN) and fuel/ wax

light stuff like saw dust to decrease velocity

needs booster, insensitive, mining

Iremite

Binary explosives

two inert components, safe until mixed

Mix then set off with blasting cap

Blasting cap

primer, initiate booster or main charge

fuse → primary explosion → output

Lead azide

Booster

more sensitive, used to add enough shock to set off main charge

RDX, TNT, PETN

Explosive scene investigation

use objects close to explosion, condensation on cold surface and porous surfaces

How built/ function, what material, describe, compare

Order of explosive scene investigation

render safe → secure scene → work scene of blast and flight paths →ID ignition source, container(s), electronics, prints

Packaging volatile/ porous evidence

clean, airtight paint cans

Packaging whole powder

plastic film canister, ½ full

Packing clock/ wires

Plastic bag (paper bag/ box for prints)

Sources of chloride ions

degradation of perchlorate/ chlorate, NaCl, environment

Sources of sulfate ions

explosive residues, combustion product of sulfur

Sources of carbonate ions

minor component/ product, contaminant

Sources of nitrate

in explosives, fertilizer

Sources of chlorate

flash powders and matches

Sources perchlorate

BPS, flash powders

Sources of sugar

improvised source (fuel)

Analysis of unconsumed particles

WEIGH FIRST, physical properties, separate types, SEM, FTIR, extract, burn test in enough

Why burn test

see if it even goes off, relative rate of rxn, flame color for pyrotechnics, physical properties

Analysis of device/ debris

Weigh and measure, extraction of unconsumed explosive from thread, device, adhesive

Extraction solvent order

MeOH (for slurry or gel) → Ether/ DCM → Acetone → DI H2O → toluene

done to isolate specific components

MeOH extract

MMAN, slurry/ H2O

Ether/ DCM extract

NG for double-based SP

Acetone extract

NC and organics (polar organic)

DI H2O extract (warm)

inorganics

Toluene extract

sulfur (BP and some BPS)