Sciencemadness Discussion Board

Tetranitomethane/toluene explosive mixture myth

Dany - 4-1-2014 at 19:52

Over the last years, i came across science forums and threads that discuss the tetranitrometane (TNM)/Toluene mixture. The dominant idea on this mixture is that at zero oxygen balance (OB), the TNM/toluene can detonate at a rate of 9300 m/s and generate heat up to 10000°C. here's are some of the thread and pages on TNM/toluene mixture:

http://www.sciencemadness.org/talk/viewthread.php?tid=1181

http://www.desertwar.net/explosive-material.html

http://web.mit.edu/semenko/Public/Military%20Manuals/RogueSc...

So to test these claims, i decided to calculate theoretically the detonation performance of this mixture (TNM/toluene) at zero oxygen balance. To perform the calculation i used the FORTRAN BKW thermochemical code. As i explained in previous thread, the FORTRAN BKW is a code written in 1967 by Dr. Charles MADER and other at the Los Alamos National Laboratory. FORTRAN BKW uses the Becker-Kistiakowsky-Wilson equation of state (BKW EOS) for gaseous detonation product and the Cowan Equation of State for solid detonation products. The parameter used are those of RDX (best fit). the RDX parameter used are:

beta= 0.16
kappa= 10.91
alpha= 0.5
theta= 400

there is another possibility of parameter set called TNT parameter which is used in explosive that generate too many mole of carbon in there detonation products (e.g., TNT, DATB...). for more information see [1].

First, i performed the calculation on zero oxygen balance (relative to CO2) because it is expected that this mixture will yield the highest explosive energy over all possible mixture of TNM/toluene. the zero OB mixture is composed of 77.05% TNM and 22.95% toluene (on a volume basis) or 86,4% TNM and 13.6% toluene (on weight basis). To calculate the detonation performance in FORTRAN BKW code you need the chemical formula, the density of the mixture and the heat of formation (at 0°K).

The atomic composition of zero OB mixture (based on 100g of the mixture) of TNM/toluene is :

C1.474H1.181N1.763O3.526

The density of the mixture is :

ρmixture=1.46 g/cm3 (based on ρTNM= 1.637 g/cm3 and ρtoluene= 0.865 g/cm3 from Aldrich chemical)

the heat of formation taken from NIST:

HOFTNM= +9.08 kcal/mol (@ 298°K)

HOFtoluene= +2.87 kcal/mol (@ 298°K)

the HOFmixture= +4.42 kcal/100g (@ 298°K)

however, the heat of formation needed in FORTRAN BKW should be at 0°K and not 298°K. With the help of data from NIST-JANNAF thermochemical tables, the HOFmixture at 0°K is:

HOFmixture= +11.48 kcal/100g

with these data, the detonation performance of TNM/toluene using FORTRAN BKW is:

Dcj= 7300 m/s
Pcj= 213 kbar
Tcj= 4506°K (4233°C)
Vcj= 0.498 cm3/g

It become obvious after these calculations that the TNM/toluene mixture at zero OB has a moderate detonation performance (close to TNT) and the temperature is far below 10000°C.

another explosive performance is the Gurney velocity or Gurney constant. For each explosive there is a Gurney constant associated which indicate the acceleration ability of metal for a given explosive/explosive mixture. I calculate this constant using the method of Keshavarz [2]. the Gurney constant of TNM/toluene is 2.64 km/s which is in the same order of that of composition A-3 (2.63 km/s). The Gurney velocity of HMX is 2.97 km/s and that of PETN is 2.93 km/s, values taken form [3].

the worst part of this explosive mixture is that TNM/Toluene is a very sensitive explosive according to an old patent [4]. This patent state that the TNM/toluene may explode from a slight jar.

To conclude:

the TNM/toluene mixture at zero OB, is a moderate explosive with high sensitivity. the detonation temperature is 4233°C which is far below 10000°C. these moderate detonation performance are expected since one of the explosive material parameter (density) is small (1.46 g/cm3).

Reference

[1] Charles L. Mader, Numerical Modeling of Explosives and Propellants, Third Edition, 2008
[2] M.H.Keshavarz, New Method for Prediction of the Gurney Energy of High Explosives, Propellants, Explosives, Pyrotechnics, 33, No. 4, 2008
[3] B. Dobratz, LLNL Explosives Handbook-Properties of Chemical Explosives and explosive simulants (rev.2-1985)
[4] US Patent 2560439, Liquid explosive consisting of a nitroparaffin and n-dodecane.

Dany.



[Edited on 5-1-2014 by Dany]

Davin - 4-1-2014 at 20:48

Lets see how you do against explo 5.04.

You use a 9.08 kcal/mol heat of formation for TNM. Converted to energy of formation that is +269.8 kJ/kg. (explo database has 272.1) close enough. I used your heat of formation for toluene, converted to energy of formation, +238 kJ/kg.

Giving
5390 K
7543 m/s
228 kbar.

This uses the 86.4/13.6 ratio you used.

Just for fun, 80/20 ratio, using same density as above because I was too lazy to recalc. OB =-23%
4956K
224 kbar
7452 m/s

Pure TNM at TMD (1.64 g/cm3). Lets see if the addition of toluene as fuel is more important to performance than the loss of density from addition.

Indeed it is!
2786 K
148 kbar
6179 m/s

Dany - 4-1-2014 at 21:29

Davin, i'm glad to see you here after a long absence...

thanks for your calculation using the the EXPLO 5 code. As your calculation shows, there is a good agreement between FORTRAN BKW and EXPLO 5 for Dcj and Pcj. However, for the Tcj i'm inclined to believe your value (5390°K instead of 4506°K), because in a previous study [1] Dr. Suceska (the creator of EXPLO 5) demonstrate that EXPLO 5 yielded Tcj values that are closer to experimental one than the FORTRAN BKW does. a difference of approx. 900°K (between the two codes) seems very high but one should bear in mind that Tcj is the most difficult detonation parameter to measure. A difference as high as 1000°K is seen in the experimentally published Tcj for a given explosive. The most important part is that the value of Tcj for this mixture is far below 10000°C.

Reference

[1] M.Suceska, EXPLO5-Computer program for calculation of detonation parameters (in International Conference of ICT Held in Karlsruhe, Federal Republic of Germany on July 3-6, 2001. Energetic Materials: Ignition, Combustion and Detonation)

Dany.

Ral123 - 5-1-2014 at 02:14

Thanks Dany, I've always thought TNM/Toluene should be similar in energy density with NMNA or TNT/NA.

DubaiAmateurRocketry - 5-1-2014 at 04:43

Nice, where can I find how to use FORTRAN 's equation for calculating VoD ?

Wow Davin, do you have EXPLO5 program ?

Also as for 10,000°C I dont think anything could even reach that ? Wont it enter a plasma phase and then give huge amount of gas L/Kg ?

Also, I would like to find a paper on gas volume of detonation per Kg, often seen as L/Kg such as for TKX-50 it generates 846 L / Kg, at a density of 1.87 at room temperature, is the one of the very high ones ive seen.

[Edited on 5-1-2014 by DubaiAmateurRocketry]

Zyklon-A - 5-1-2014 at 07:07

Yea, I think 10 000C is a bit to high, for sure that's plasma.

Dornier 335A - 6-1-2014 at 07:27

Great opportunity for me to compare my newly calibrated equilibrium program to two other thermochemical codes.

For the stoichiometric TNM/toluene mixture:
Pcj= 219 kbar
Tcj= 5232 K

The 80/20 mix:
Pcj= 227 kbar
Tcj= 4854 K

So nice agreement with the EXPLO 5 code.

10000°C wouldn't even be reached if the only products were CO2, H2O and N2. The closest I've ever got when calculating the equilibrium composition is 7962 K. That was for a homogeneous mixture of liquid ozone and solid dicyanoacetylene in a 4.2:3 molar ratio.
ρmixture: 1.11 g/cm3
∆Hmixture: +4719 kJ/kg (at -112°C)
Composition of 1 kg of the mixture:
C27.922N13.961O29.319

PHILOU Zrealone - 8-1-2014 at 07:45

What about mixture of MNT, DNT or TNT with TNM?
The use of toluen is very detrimental to the density...

Also Hexanitroethane would be a better choice since it has a better density and a higher VOD than TNM!

Dornier 335A - 8-1-2014 at 12:25

A liquid fuel is probably the best choice. The brisance will most likely suffer if the mixture isn't completely homogeneous.

Yes, mixtures of hexanitroethane and energetics like TNT or tetryl have extremely high performance. Here is an old thread about the subject.

Dany - 28-1-2014 at 06:34

An important study on the measurement of detonation temperature of PETN. The study, shows that the detonation front can compress and heat the gases in the pores of porous PETN. The temeprature of these gases can reach more than 10000°K. This effect, will lead to overestimate the value of real detonation temperature (the temperature of detonation products at the Chapman-Jouguet point) wich make experimental detonation temperature hard to measure.

Dany.

Attachment: detonation temperature.pdf (129kB)
This file has been downloaded 766 times

PHILOU Zrealone - 28-1-2014 at 11:39

Quote: Originally posted by Dany  
An important study on the measurement of detonation temperature of PETN. The study, shows that the detonation front can compress and heat the gases in the pores of porous PETN. The temeprature of these gases can reach more than 10000°K. This effect, will lead to overestimate the value of real detonation temperature (the temperature of detonation products at the Chapman-Jouguet point) wich make experimental detonation temperature hard to measure.

Dany.

The same effect is seen:
-in microballoons or emulsion slurries...kind of shaped charges on a micro scale (mm size).
-in sonochemistry and implosion of the cavitation bubbles
Those are adiabatic compression to near zero volume virtually without ability for heat escape...then the pressure and heat inside those cavities are very high and this explains the rare reactions that happens there.
Sonochemistry also happens without ultrasound Nickel horn, but simply with ultraturax mixing (kind of mixer for lab emulsion at >30000-70000 rpm).
In such reaction endothermic minor products can reach near theorical 50% yield.

Dany - 16-3-2014 at 04:23

The following PhD thesis is a good references for the studies of Hot spot and how these spot affect the ignition and growth of detonation:

The role of hot-spots in the ignition and growth of explosion

I suggest reading this thesis, because hot-spot is an important factor of heterogeneous explosives. by heterogeneous explosive i mean polycrystalline explosive, PBX's (Plastic Bonded Explosive) plastic explosive, aluminized explosives... A liquid explosive with microballoons in it is a heterogeneous explosive. One such solution is a mixture of nitromethane with glass microballoons (GMB). The microballoon are kept in suspension by adding a small amount (3%) of polymethyl methacrylate (PMMA). Single crystal and pure liquid explosive are essentially homogenous explosive. The mode of detonation in the two system (heterogenous and homogenous) is completely different. In homogenous explosive the shock wave heat the explosive and after a certain induction time (which is inversely proportional to shock amplitude) a thermal explosion begin at the explosive interface and a detonation wave start to move in the previously heated region by the first shock wave. So at the beginning the detonation wave is overdriven, than when the detonation front catch the leading front of the first shock wave the detonation return to the normal Chapman-Jouguet condition. In heterogenous explosive the detonation progress via hot-spots. A good reference on heterogenous and homogenous explosive and their detonation is the book of Anatoly DREMIN

Toward Detonation Theory

This is the link for the thesis cited above:

http://www54.zippyshare.com/v/94361573/file.html

Dany.

Marvin - 16-3-2014 at 05:58

....and the reason Mercury Fulminate dead presses.

Thanks for this Dany it looks good.

Dany - 16-3-2014 at 06:27

Marvin,

Read the attached study to know more on dead-pressing of Mercury fulminate. According to this study, the internal microstructure of the compact is of primary importance in determining dead-pressing properties of mercury fulminate. This study support an old study (see reference in the attached paper) that state that the lack of gas penetration into the bulk is a major factor in explaining the dread -pressing of Mercury Fulminate.

for informations, other explosive can be dead pressed. According to the book Primary Explosives published by Springer diazodinitrophenol (DDNP) become dead-pressed @ 1.3-1.4 g/cm3. Mercury fulminate @ 3.6 g/cm3. Silver fulminate when pressed above 33 MPa. Tetrazene, cyanuric triazide and 1,3,5-Triazido-2,4,6-trinitrobenzene (TATNB) are also known to become dead-pressed.

below is the experimental study which deal with dead-pressed mercury fulminate.

http://www16.zippyshare.com/v/47465242/file.html

Dany.

Dornier 335A - 17-3-2014 at 00:34

That was an interesting read. Is the low velocity detonation seen in insufficiently initiated NG the same thing as the compressive burning described in the thesis?

Dany - 28-3-2014 at 01:43

Quote: Originally posted by Dornier 335A  
That was an interesting read. Is the low velocity detonation seen in insufficiently initiated NG the same thing as the compressive burning described in the thesis?


For more informations on low velocity detonation (LVD) read this and reference therein:

http://www.sciencemadness.org/talk/viewthread.php?tid=20280&...

Dany.