Darkfire - 16-3-2003 at 10:32
Like most people i can tell you that this an explosive and this isnt, but i want to know why.
How do you tell if somethings explosive or if its harmless, or if its explosive but about as sensitive as a rock? I've looked through several
science books but all were to afraid to deal with Mad Science.
CTR
[Edited on 16-3-2003 by Darkfire]
vulture - 16-3-2003 at 13:01
The more energy is released when a bond is formed, the more stable that bond is.
The reason why peroxides are so unstable is because the bond formation is barely exothermic.
Another thing is that explosives pack reducers and oxidizers in one molecule.
For example, TNT's nitrogroups contain the oxygen necessary to oxidize the hydrogen and the carbon atoms.
One of the reasons why TNT is so stable because the nitrogroups actually stabilize the resonance inside the benzenering.
I would arrange the sensitivity by bond like this:
-O-O- highly unstable and very sensitive
-O-NO2 stable, but sensitive
-N-NO2 very stable, mediocre sensitivity
-C-NO2 very stable, low sensitivity
-C-O-ClO3 quite stable, but very high sensitivity
KABOOOM(pyrojustforfun) - 16-3-2003 at 19:51
but this is general. we say nitramines have medium sensitivity but RDX is so sensitive that can't be loaded without binder. nitroaromatics have
low sensitivity but HNB is quite sensitive.
<a href="http://www.cc.umanitoba.ca/campus/health_and_safety/explosives.html">this page identifies groups that make a compound
explosive</a>
Dany - 27-12-2013 at 16:52
A chemical explosive is a substance that contain an explosophoric group (e.g., nitro, nitrato, nitramine, azide, tetrazol...). An explosophoric group
make a substance a potential explosive just like a chromophore group which make molecule absorb electromagnetic radiation at certain wavelength.
Another important thing that an explosive substance must have is the rapid release of energy (on the scale of microseconds). The thermodynamics (in
term of energy content) alone is not sufficient . A substance with high energy content is not necessarily an explosive. The energy of an explosion can
be derived from the internal oxidation of the oxidizing moiety (e.g, NO2 ) and the reducing (or fuel) moiety (e.g., Carbon framework).
another way to get energy is only from positive enthalpy of formation like in the case of azides. The azide anion is highly endothermic and as the
product formed is N2 when azides undergoes a detonation the reaction is highly exothermic (N2 is one of the most stable molecule
in nature having a large negative heat of formation). In certain explosive the two mechanism cited above can be present at the same time.
Sensitivity of an explosive material is complex feature that depend on many factors (e.g., chemical, physical state, etc...). However we learned that
some careful chemical manipulation of explosive molecule can furnish insensitive materials, like alternating amino and nitro group like in the TATB
(1,3,5-triamino-2,4,6-trinitrobenzene) molecule which is highly insensitive. Alternating -NH2 and -NO2 group form an extensive
inter- and intramolecular hydrogen bonding leading not only to decrease in sensitivity but also an increase in crystal density which is crucial to
high detonation performance.
Porous explosive material are more sensitive than pressed or single crystal explosive. According to the hot spot theory, pores present in explosive
will act as a hot spot when it interact with a shock wave in the explosive material and detonation generally start at these site (hot spots). One
beautiful example is given by William C. DAVIS a former detonation physicist at Los Alamos National Laboratory. The explosive is PETN. An experiment
was performed on two sample of PETN at the same crystal density (100% TMD or Theoretical Maximum Density). The first sample was a single crystal PETN
(which is almost voidless) and the second sample is a powder form PETN. 11 GPa (or 110 kbar) was needed to initiate the single crystal PETN in 1
microsecond while 2.5 GPa (25 kbar) is enough to initiate the powder form PETN. the bondary between individual crystals in the second sample (which
are absent in the first sample) act as a hot spot site which once they meet the shock wave they will concentrate the shock energy into heat. the local
high heat in the explosive will start the decomposition and spreading of a reaction. the coordinating energy release of multiple hot spot site will
form the detonation wave in the explosive.
i strongly recommend everyone interested to engage seriously detonation science to read this easy but very important article by William C. Davis. The
article give a general idea of detonation science with examples.
Dany.
Attachment: Detonation.pdf (1.9MB)
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