4. EXPLOSION & EXPLOSIVES
• EXPLOSION - Sudden release of energy
and an increase in volume – may
involve generation of high
temperatures and release of gas
• EXPLOSIVES – any chemical compound,
when heated, impacted, detonated or
initiated that will undergo change
evolving large amounts of gas
5. DEFLAGRATION VS DETONATION
• Deflagration
• Low explosives
• subsonic explosion driven by heat transfer
• “slow burning”
• Detonation
• High explosives
• Supersonic explosion – breaks the sound barrier
• Supersonic shock wave
7. OXIDANTS/OXIDIZERS
• A substance that removes electrons from another reactant in a REDOX chemical
reaction.
• Primary hazard of oxidants/oxidizers are their ability to combust or initiate
combustion.
• “The dangerous materials definition of an oxidizing agent is a substance that is not
necessarily combustible, but may, generally by yielding oxygen, cause or contribute
to the combustion of other material”.
8. OXIDIZER HAZARDS
• Incidents must be handled promptly
• Hazards of stored oxidizers:
Increase the burn rate of combustible materials
cause spontaneous ignition of combustible materials
can decompose rapidly
can liberate hazardous gases
can undergo self-sustained decomposition which can result in explosion!
can react explosively if mixed with incompatibles or in fire conditions
9. OXIDIZER CLASSES
• Class 1: An oxidizer that does not moderately increase the burning rate of the combustible
materials with which it comes into contact
• Class 2: An oxidizer that causes a moderate increase in the burning rate of combustible
materials with which it comes into contact
• Class 3: An oxidizer that causes a severe increase in the burning rate of combustible
materials with which it comes into contact
• Class 4: An oxidizer that can undergo an explosive reaction due to contamination or
exposure to thermal or physical shock and that causes a severe increase in the burning rate
of combustible materials with which it comes into contact
10. OXYGEN BALANCE
• Just how explosive is it?
• O.B. = -1600[(2x) + (y/2) + Met – z]
M.W.
Where:
X = # Carbons
Y = # Hydrogens
Z = # Oxygens
Met = # metals (if no metal present then “0”)
M.W. = Molecular Weight
• Compound must also contain a potentially reactive group
• Empirical formula is used to determine # of C, H, O, Met
11. IT’S A POTENTIALLY EXPLOSIVE
MOLECULE IF…
…it has enough oxygen to convert…
1) All of the carbon into carbon dioxide
2) All of the hydrogen into water
3) All of the metal into metal oxide
THEN it is said to have ZERO OXYGEN BALANCE
When MORE oxygen is present than is used it is said to have (+) oxygen balance.
When LESS oxygen is present than can be used it is said to have (-) oxygen balance.
12. SENSITIVITY, STRENGTH, BRISANCE
• SENSITIVITY - is the degree to which an explosive can be initiated by impact, heat,
or friction.
• STRENGTH - is the parameter determining the ability of the explosive to move the
surrounding material. It is related to the total gas yield of the reaction, and the
amount of heat produced.
• BRISANCE - is the shattering capability of a high explosive, determined mainly by its
detonation pressure.
13. OXBAL & BOOM-ABILITY
• SENSITIVITY, STRENGTH & BRISANCE
are ALL somewhat dependent upon Oxygen Balance (OxBal).
Compounds approach optimum explosivity (BOOM-ability) as the OxBal approaches ZERO
• Though OxBal can be calculate remember….
it is an ASSESSMENT tool only
it is used to gauge the POTENTIAL to explode NOT as a predictor of explosivity.
• OxBal %’s between -200 and +200
have a higher chance of explosive potential
the closer to “0” the “better” i.e. more explosive potential
14. ACETONE VS ACETONE DIPEROXIDE
Acetone Acetone diperoxide
C3H6O =
MW = 58.08g/mol
OxBal = -220.38
Has no metals or potentially reactive groups
C6H12O4 Empirical formula = C3H6O2
MW = 148.16g/mol
OxBal = -75.58
Has no metals but DOES have potentially
reactive groups. i.e. Peroxides
15. SPEAKING OF PEROXIDES
• Contain the O-O linkage which is inherently unstable
• Largest class of peroxides are the organic peroxides or hydroperoxides
R-O-O-R’ Organoperoxides R-O-O-H Hydroperoxides
• Prone to decompose violently from:
• Shock weak O-O bond ~ 207 kJ/mole
• Friction compared to C-C bond ~345 kJ/mole
• Heat Dissociation products are free radicals and
highly reactive
16. PEROXIDE USES
Making polymers – peroxides decompose and generate radicals that initiate
polymerization
• Very diluted peroxide initiators
• heat of decomposition is easily absorbed in the surrounding matrix (like a heat sink)
HOWEVER – in a pure, concentrated form, heat evolved from decomposition may not
dissipate efficiently
As TEMP REACTION RATE
SELF-ACCELERATING DECOMPOSITION
17. AUTOXIDATION – FREE RADICAL CHAIN
PROCESS
• 3 STAGES
• CHAIN INITIATION – some event initiates such as exposure to light or random
interaction with O2 or an impurity is introduced and radicals are formed
• PROPAGATION – the cycle continues as new radicals act as initiators and propagate
hydroperoxides
• TERMINATION – reactions occur where the free radicals collide and combine odd
electrons to form new bonds…..
…Unless it EXPLODES!
19. PEROXIDE FORMERS
• Are compounds that themselves are not peroxides, however, through free-radical,
autoxidation, H-abstraction process involving molecular oxygen peroxides are
formed
• Initiated by light, a radical generator or a peroxide contaminant
• A cyclic process almost identical to peroxide decomposition autoxidation process
however converts a NON-peroxide into a peroxide.
• The most common are organic compounds but there are some inorganic
compounds.
22. TOP THREE PEROXIDE FORMING
MOIETIES
Ethers & Acetals
w/a-hydrogen
Hydrogen attached to an alpha
carbon is called an alpha-
hydrogen
Alkenes with allylic
hydrogen
Allylic hydrogen is a hydrogen
atom that is bonded to an allylic
carbon in an organic molecule
Chloroalkenes &
Fluoroalkenes
23. MORE MOIETIES
Vinyl alkynes (vinylacetylene)
with a- hydrogens
Alkylalkynes with a- hydrogens Alkylarenes with tertiary
a- hydrogens
Dienes (divinyls)
24. Alkanes and cycloalkanes with
tertiary hydrogen
Acrylates & methylacrylates Secondary alcohols
Ketones with a- hydrogens Aldehydes
Ureas, amides and tactams with a- hydrogens on a
carbon attached to a nitrogen.
29. PEROXIDE FORMER INHIBITER
BHT- Butylhydroxytoluene, also a food preservative. Follows the same general “path” as an you see in the autoxidation
of peroxide formers HOWEVER, after H-abstraction from the BHT to the radical the BHT radical ends the chain reaction
due to stearic hindrance.
31. EXAMINE FOR VISIBLE CRYSTALS
Crystals? DON’T TOUCH!
The crystals may cause an
explosion if subjected to
an impact or friction.
Never underestimate a peroxide formers ability to explode!
32. IS IT SAFE TO TEST FOR PEROXIDES?
Otherwise you may test if:
• Low peroxide hazard chemicals – previously opened container less than
2 years old or unopened less than 3 years old.
• Medium peroxide hazard chemicals – previously opened container less
than 1 year old or unopened less than 2 years old
• High peroxide hazard chemicals – previously opened container less than
6 months old or unopened less than 1 year old.
NOTE: If it’s not safe to test due to crystals or <10% volume this is a BOMB
SQUAD job.
If the contents have evaporated to
less than 10% of original
volume….DO NOT TEST!
33. TESTING FOR PEROXIDES
• Color-metric test strips
• Detect inorganic and organic
compounds that contain a peroxide or
hydroperoxide group
• Suitable for routine testing of simple
ethers such as Diethyl ether, THF, and p-
dioxane.
• Iodine Test
• Suitable for testing ay peroxide forming chemical
• Test Mixture: A 1:100 part solution of potassium
iodide and glacial acetic acid
• Test 1 ml of chemical with 1 ml of text mixture.
Pale yellow almost colorless ~ 0.001-0.005%
peroxides
Bright yellow or brown ~ 0.01% or greater
34. STABALIZING PEROXIDE FORMERS
• ~ 0.001-0.005% peroxides in solution
• May be moved for stabilization
• 1g of BHT (Butylated hydroxytoluene)
per liter of chemical.
• Date when stabilized on container
• ~ 0.01% or greater peroxides in
solution
• DO NOT MOVE! Stabilize before
moving.
• 1g of BHT per liter of chemical.
• Date when stabilized on container
35. Methods for destruction of peroxides for HAZARDOUS MATERIALS
personnel
*Which one you pick depends on knowing the chemical properties of the material and any possible incompatibilities with the
materials used to treat the peroxides. Either of these two methods would be a good choice for diethyl ether, for example.
Ferrous sulfate reduction
Add 6 g of ferrous sulfate, FeSO4, and 6 mL of concentrated sulfuric acid, H2SO4, to 110 mL of water. Shake or mix well.
Caution: always add acid to water, not vice-versa.
Shake approximately 1 liter of the peroxide-contaminated material in a bottle or separatory funnel with 5-10 mL of your ferrous
sulfate solution.
Remove and discard the aqueous layer. Wash/shake your solution with distilled water and discard the aqueous layer. Repeat
your peroxide test on your material. Repeat step 2 as necessary until the test is negative for peroxides.
Activated alumina adsorption
Pass your contaminated material through a standard chromatography column packed with activated alumina (Al2O3). Allow
approximately 80 g of alumina per 700 mL of material.
Test the purified material. Repeat step 1 as necessary until you get a negative peroxide test.
Caution: the peroxides will remain on the alumina in active form. Wash your alumina with the FeSO4 solution described in
method A above before disposing or reusing your alumina. Do not combine it with other wastes if you (foolishly) decide not to
treat the alumina before disposal.
Note that destruction of high level of peroxides is a procedure fraught with peril and risk of bodily
injury, including death.
