ExplosivesErin Morris

Mining Engineering

OutlineWhat I doWhy I’m hereBasics of Explosives

DefinitionsClassificationsInitiation & Sensitivity

Insensitive MunitionsPolymers in Explosives

BindersPlasticizers

Special Uses

What I doMaster’s in Mining Engineering

Emphasis in Explosives

What is a Mining Engineer Doing Here?

ChemistryThermodynamicsFluid DynamicsAerodynamicsMechanics

MaterialsElectricity and

ElectronicsMeteorologyBiologyPhysiology

• Explosives Engineering is a combination of many other sciences and engineering technologies: (Cooper)

The BasicsExplosive:

“A substance which can be initiated by friction, impact, shock, spark, flame, heating or simple application of an energy pulse; and undergoes a rapid chemical reaction evolving a large amount of heat and exerting a high pressure on its surroundings.” (Agrawal and Hodgson)

An explosion will either produce a shock wave, throw fragments, or both

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DefinitionsDeflagration vs. Detonation

Deflagration is a thermal decomposition (burning)Detonation is thermal decomposition completed

at shock velocities (burning + shock)

Brisance:Speed at which reaction occursShattering potential of an explosiveDepends on explosive composition and degree of

confinement of the blast

ClassificationsLow Explosives

Slow reaction with a gradual, extended shock wave and low fragment velocities

Low brisance; releases a large amount of energy, but long duration allows energy to dissipate

Expansion of the gases used to move projectiles (Propellants)

ClassificationsHigh Explosives

Violent reaction with a short duration, high pressure shock wave and large fragment velocities

High brisance; used solely for destructive power

High Explosives

Trinitrotoluene (TNT) Cyclo-1,3,5-

trimethylene-2,4,6-trinitramine

(RDX)

Pentaerythritol tetranitrate (PETN)

Initiation & SensitivityPrimary Explosives

Very sensitive to heat, impact, friction or static electricity; easily detonated

Used in blasting caps to trigger larger secondary charges

Secondary ExplosivesLess sensitive; requires more energy (primary

explosive) to be detonated Used in large quantities, more powerful than

primary explosives

Insensitive MunitionsTwo goals in design of future explosives

Increase performanceDecrease hazards during transport and storage

Many ways to accomplish thisNew designsPackaging and mitigation devicesMake explosives less sensitive to accidental

initiation

Polymers in ExplosivesFunctions:

BindersPlasticizers

Products:Rocket PropellantsPlastic-Bonded Explosives (PBXs)Putties, Rubberized & Extrudable Explosives

Can be inert or energetic

BindersSome consider dynamite as the first use of

binders in explosivesAlfred Nobel absorbed nitroglycerin into a

porous medium (diatomaceous earth) to reduce its sensitivity and allow for safe handling

Modern dynamites use a variety of absorbents and additives

PBXsToday cross-linked polymers are used to provide a

matrix to bind explosives to other components

Plastic-Bonded Explosives (PBXs)Polymeric binder coats and suspends the crystals of a

powdered explosiveMixture cured to create a tough elastomer which can

absorb and dissipate energy from friction and shockCombined with plasticizers, allows PBXs to be

pressed and machined

Common PBXs

Binders in PBXs

PlasticizersPlasticizers are mixed with finely powdered

explosives to create puttiesPutties can be molded into almost any shape

by hand, and retains its shape unsupported after molding

The most common putty explosive in the United States is Composition C-4

Composition C-4

“Special” UsesRubberized Explosives

Mix of RDX or PETN with plasticizers and rubber-type polymers that can be rolled into thin sheets

Sheets can be cut to shape, bent, and glued to surfaces

DOE LX-02-1 Composition

“Special” UsesExtrudable Explosives

RDX or PETN mixed with Sylgard 182 silicone rubber and curing agent, forms a thick viscous material that can be extruded

After extrusion, temperature can be raised to polymerize and cure the Sylgard

Another version from North American Explosives is packaged in small tubes to fit a standard caulking gun

Key Point to RememberName the 2 functions of polymers used in

explosives and describe how they work in plastic-bonded explosives (PBXs).BinderPlasticizerIn plastic-bonded explosives (PBXs), a binder

coats and suspends the crystals of a powdered explosive. This mixture is cured to create a tough elastomer which can absorb and dissipate energy from friction and shock.

Questions?

ReferencesAgrawal, J.P., and Hodgson, R.D. 2007. Organic

Chemistry of Explosives. John Wiley & Sons, Ltd. Chichester, West Sussex, England.

Baird, J. 2010. Class notes, unknown author. Cooper, P. W. 1996. Explosives Engineering. Wiley-

VCH Inc. New York, NY, USA. Provatas, A. 2000. “Energetic Polymers and

Plasticisers for Explosive Formulations – A Review of Recent Advances.” DSTO, Aeronautical and Maritime Research Laboratory. Melbourne, Victoria, Australia.

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