Sciencemadness Discussion Board

Why did TNT become so universal?

Delta-R - 21-12-2020 at 21:01

So like the title says, of all the high explosives known back before WWI/II, why did so many countries choose TNT as the de facto standard military high explosive, and how did it stick around so long? It requires a fairly intensive multi step synthesis that demands highly pure, expensive reagents like oleum and white fuming nitric acid, leaves tons of toxic waste, and isn’t really that spectacular as an explosive (leaves a bunch of carbon soot residue, isn’t all that powerful, less than .75 the RE factor of nitroglycerin, etc), at least compared to the difficulty, cost, and wastefulness of its production.

PETN, RDX, nitroglycerin, EGDN, nitrourea... all were invented in the late 1800’s, all have a higher RE factor, all are much easier to produce, and while all were also used in the world wars, TNT was much more widely used either by itself or in a mixture from what I can tell, with only RDX production beginning to come close towards the end of the WWII.

Was it purely a result of it’s insensitivity and ability to be melt cast? I feel like there must be some other factor I’m missing that outweighs the downsides, considering all the other excellent options they had available.

And really, the same question could be asked for HMX too - considering the performance of HMX is practically identical to RDX, why would any military take on the added difficulty and cost of production compared to RDX for such an insignificant benefit?

Twospoons - 21-12-2020 at 21:15

Quote: Originally posted by Delta-R  

Was it purely a result of it’s insensitivity and ability to be melt cast?


Those seem like pretty major advantages if you are making millions of shells - low risk of accidents and easy handling in manufacture. The insensitivity is probably a bonus in the field too - who wants to ride around in a truck full of touchy munitions?

Fulmen - 22-12-2020 at 00:23

Don't forget long term stability.

Johnny Cappone - 22-12-2020 at 00:46

As already mentioned, stability and sensitivity were certainly key factors. Well, at least it was what caused the replacement of picric acid by TNT even when the availability of toluene was less than that of phenol, and even though TNT was a little less powerful.

Herr Haber - 22-12-2020 at 03:34

1906 or somewhere around there.

Germany uses TNT, UK uses picric acid.
UK shells detonate on impact with armour, German shells penetrate than detonate.
World learns a lesson.

Delta-R - 22-12-2020 at 11:56

Ok well let’s take TNT vs RDX. TNT was discovered as an explosive in 1891, RDX 1898. RDX is by far the better explosive by any metric, yet TNT was put into service by everyone almost immediately, or at least before 1910 whereas RDX didn’t really start to be used until the 1920’s and didn’t really take off until the late 1930’s.

The only quality I really see where TNT comes out ahead is the ability to be melt cast. But let’s take filling shells - RDX is SO much more powerful, even a shell with low density RDX powder poured in would sill be more powerful. And iF there was a situation that absolutely required an insensitive casting, plasticizers and phlegmatizers had already been invented and in use and even a completely inert plasticizer would still yield a product with a higher RE, no?

I guess what I’m saying is I just can understand one or even several countries investing heavily in TNT but it was everyone- and it’s just beyond me why it took so long for better alternatives to really start taking hold and how TNT lasted so long

Fulmen - 22-12-2020 at 12:22

The fact that TNT is the preferred explosive should tell you that you're wrong.

First off, RDX is also SO much more sensitive than TNT. Filling artillery shells with powdered RDX? Powders are a total PITA to handle, and even if you could do that, the shell will experience something in the order of 10'000g acceleration. Setback is a real danger even with TNT. Phlegmatized RDX might work, but it would still be a major drawback during loading.

And what about cost? IIRC the direct nitration process available for RDX back then was inefficient, partly because it was hard to recycle spent acid.

unionised - 23-12-2020 at 08:03

Quote: Originally posted by Delta-R  


The only quality I really see where TNT comes out ahead is the ability to be melt cast

Did you consider cost?

roXefeller - 27-12-2020 at 16:18

A better reason for the switch from picric acid to TNT was its lack of acidity. Munitions people didn't need to worry about dangerous salts.

I don't know much about the driving factor between HMX and RDX beyond solid propellants, but that cast-ability of TNT is major. Like mentioned above charging powders is a PITA, they can aggregate loose and ask for pinch points. Amorphous TNT is really sleepy. Detonation requires a heterogenous mix to decrease critical diameters, they are the sites of microheating. Waxy TNT doesn't have that but crystalline RDX does.

Don't get wrapped up on single metrics of detonation. RDX is known for brisance, but not all applications demand that. Airblast and lift are also important aspects. If more brisance and sensitivity were asked for, they blended RDX into TNT.

I second the motion of asking about cost. Given the procedures to recycle acids from third stage nitration back to second and first stage nitration (which RDX doesn't have from its instability to survive linear polynitramine decomposition), has relative cost been computed? Include yield percentages in that.

One thing to detract from TNT that you didn't mention was the liver toxicity from chronic handling.

Fyndium - 31-12-2020 at 03:04

Industrial scale dedicated production is not that sensitive on multi-step synthesis, especially if stuff can be recycled.

Previous posts indicate many good points of TNT. Melt-casting eases up mass production of shells to huge extent, and it also increases RE by higher density compared to powders. Safety is a major factor too, as war equipment tends to get manhandled and shot at and it would be silly to get blown up by some stray bullets. Toxicity has never been such of a concern for industry, as it lays on the workers and once they walk out the plant, it's their problem, and everything that is liquid, can be pumped down the river, and solids can be dumped away from sight. Nowadays at least some occupational and environmental laws exist.

Also I've understood that TNT was rarely used as sole, but it was mixed with various compositions, and the TNT can act more as a binder, like bitumen in asphalt, creating a processable mass that can be easily handled, transferred, pumped, filled and packed and it has high efficiency.

https://en.wikipedia.org/wiki/TNT#Applications

I could not imagine using energetic powders in mass filling of artillery shells. Actually handling any sort of powder that is more reactive than flour(except, don't forget about flour explosions) is pita, as it gets everywhere, is difficult to fill and pack and is hard to mix homogenously. Amateurs generally lack the concept of mass production because they only need to make a pinch of stuff for experiments and many people believe that stuff is made and handled by people handling them, while in reality most everything has been automatic packing lines since the beginning of century. They made hundreds of millions of munitions during the wars.

Hey Buddy - 31-12-2020 at 12:54

Impact and thermal insensitivity along with melt cast made it suitable for efficient mass production and standardization. All the world war nations tooled up for it and developed batch methods. When Fischer-Tropsch method came out of the bag and everybody figured out you could make hydrocarbon fuels from coal and biomass/syngas, obviously now toluene could be produced as a branched off product after torrefaction solids or liquid fuels which were produced necessarily.

Fantasma4500 - 1-1-2021 at 08:11

because its easy to handle, and easy by handle also includes stable to store- doesnt break down to become dangerous like NG would
essentially, the incompetence of the many defines the use of materials. very sad to think about

Fyndium - 1-1-2021 at 16:16

Quote: Originally posted by Antiswat  
essentially, the incompetence of the many defines the use of materials. very sad to think about


Applies to society and law universally. Even more sad to think. They should ban stupid people instead.

stamasd - 5-1-2021 at 04:22

TNT is cheap to manufacture from plentiful ingredients. In war, that plays a huge role in making a decision for or against ordnance.

It does not help if you've got the universe's best explosive, if you don't have the ingredients to make it from in sufficient quantities.

[Edited on 5-1-2021 by stamasd]

roXefeller - 5-1-2021 at 15:28

Quote: Originally posted by Johnny Cappone  
As already mentioned, stability and sensitivity were certainly key factors. Well, at least it was what caused the replacement of picric acid by TNT even when the availability of toluene was less than that of phenol, and even though TNT was a little less powerful.


As Don Cappone mentioned, availability of precursors probably wasn't weighing heavily on their decision to adopt the safest molecule.


Quote: Originally posted by Hey Buddy  
When Fischer-Tropsch method came out of the bag and everybody figured out you could make hydrocarbon fuels from coal and biomass/syngas, obviously now toluene could be produced as a branched off product after torrefaction solids or liquid fuels which were produced necessarily.


And necessity is the mother of invention.

Mush - 30-1-2021 at 10:57

Bit off topic , yet still relevant .

TNT is important because it can be melt-cast and forms melt cast matrix with other explosives. However alternative compounds are being researched.

3,5-difluoro-2,4,6-trinitroanisole: promising melt-cast insensitive explosives instead of TNT

ABSTRACT

Finding new melt-cast explosives with desired properties to replace 2,4,6-trinitrotoluene (TNT) has been intensely-pursued in recent decades. However, the contradiction among high energy, low mechanical sensitivity and low-melting makes the innovation of insensitive high-energy-density melt-cast explosives an enormous challenge, so the melt-cast explosives of comprehensive properties better than TNT has not been found. Here, we show a new way to design melt-cast insensitive energetic compound by the introduction of C-F into nitroaromatics. This as-synthesized energetic compound exhibits excellent performance with a high-measured density of 1.81 g cm−3, high thermal decomposition temperature (>300°C), high detonation velocity of 8.54 km s−1, appropriate melting point (82°C) and low viscosity(6200 mpa·S), and extremely low mechanical sensitivities (impact sensitivity, >60 J, and friction sensitivity, >360 N), superior to those of current melt-cast explosives, such as TNT and 2,4-dinitroanisole (DNAN).


Code:
https://www.tandfonline.com/doi/abs/10.1080/07370652.2020.1859645



Alkoholvergiftung - 30-1-2021 at 11:51

TNT was not only used because incompetent people handle it. It was detonation safty if the ammonition bunker was hit. I cant find it now but i know they wrote an artillery shell with picrid acid can be detonated with an charge 76cm away from it. It it is filled with TNT only 15cm or so.

Petn1933 - 1-2-2021 at 06:29

Quote: Originally posted by Mush  
Bit off topic , yet still relevant .

TNT is important because it can be melt-cast and forms melt cast matrix with other explosives. However alternative compounds are being researched.

3,5-difluoro-2,4,6-trinitroanisole: promising melt-cast insensitive explosives instead of TNT

ABSTRACT

Finding new melt-cast explosives with desired properties to replace 2,4,6-trinitrotoluene (TNT) has been intensely-pursued in recent decades. However, the contradiction among high energy, low mechanical sensitivity and low-melting makes the innovation of insensitive high-energy-density melt-cast explosives an enormous challenge, so the melt-cast explosives of comprehensive properties better than TNT has not been found. Here, we show a new way to design melt-cast insensitive energetic compound by the introduction of C-F into nitroaromatics. This as-synthesized energetic compound exhibits excellent performance with a high-measured density of 1.81 g cm−3, high thermal decomposition temperature (>300°C), high detonation velocity of 8.54 km s−1, appropriate melting point (82°C) and low viscosity(6200 mpa·S), and extremely low mechanical sensitivities (impact sensitivity, >60 J, and friction sensitivity, >360 N), superior to those of current melt-cast explosives, such as TNT and 2,4-dinitroanisole (DNAN).


Code:
https://www.tandfonline.com/doi/abs/10.1080/07370652.2020.1859645




Attachment: DF8726F9-DA19-4831-BC6D-CF67806994E7.pdf (1.9MB)
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Fulmen - 1-2-2021 at 13:18

Dude, that's some sweet specs. What about toxicity? Even though it's quite manageable with simple precautions and protective gear, the toxicity of TNT has always been a downside.


zed - 18-3-2021 at 02:22

Ummm. War materials. Price may sometimes be of little consequence.

Yet, I find myself thinking: "Good? Yes. But, how much does it cost?"

I've been pricing reagents derived from Phloroglucinol. 1,3,5-Tri-hydroxy-benzene

Not cheap. While Phloroglucinol is widespread in nature, and plants can prestidigitate it, out of H2O and thin air....

Mortal manufacturing processes, rely on cruder methods.

Yup! They make it from TNT.

The Ring structure of TNT has been so substituted, that the ring structure and substituents no longer react in what we consider normal ways. Well, I mean other than explosiveness. I'll go get a reference.

It may all be, old hat, to you guys. But, I'm not used to such stuff. TNT as a manufacturing intermediate.

I'll go fetch.

OK, I'm back.

First TNT is oxidized to Tri-nitro-benzoic acid.

http://orgsyn.org/demo.aspx?prep=CV1P0543

Then the Nitro-Benzoic acid, is reduced, hydrolysed, and decarboxylated.

http://orgsyn.org/demo.aspx?prep=CV1P0455

And, now of course, the irony. Innocent phloroglucinol, produced by plants and bacteria, can now be reverse engineered, into processes that produce TNT.

Attachment: WP-1582.pdf (15kB)
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[Edited on 18-3-2021 by zed]

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zed - 18-3-2021 at 03:36

Gotta admit. This is a better file.

Attachment: WP-1582-FR.pdf (1.7MB)
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God, how one thing leads to another.

Had an interest in 2,4,6-Trimethoxy-Allylbenzene. Exotic stuff.

Expensive precursors, not easy to find references.

So.... it's been a Long, roundabout trek, tracking down possibilities.

OCD can be a good source of entertainment, in a pandemic.

Its good to keep busy, and it is always good to learn.

But dammit! I'm ready to be vaccinated. I'm gettin' antsy.

https://www.youtube.com/watch?v=dIfQNB5WXmY

[Edited on 18-3-2021 by zed]

[Edited on 18-3-2021 by zed]

CycloKnight - 30-3-2021 at 12:58

A point not mentioned yet, is the wide availability of toluene. In times of full scale war (both world wars), nations strive to maximize toluene production for the manufacture of TNT.

zed - 11-7-2021 at 21:30

Well, it would appear that TNT is relatively non-corrosive, meaning stable.

It would also appear that Picric acid is easier to make, and Ammonium Picrate is decidedly insensitive, upon initial manufacture.

Problem? Yeah. As time goes on, Ammonium Picrate reacts with various metals present in munitions. to form extremely sensitive metallic salts.

Ammonium Picrate auto-creates its own "Blasting caps". Little areas of Metallic Picrates, that will be detonated by the slightest disturbance.

Both TNT and Picric Acid are pretty easily and cheaply made. And once upon a time, Picric Acd was the "right stuff". Too many unplanned explosions, caused TNT to replace it.

Hex - 18-5-2023 at 03:27

The critical point for TNT is that it melts low enough to be melted in hot-water fed vessels (picric acid need steams) but high enough not to melt in the field. Picric acid is only slightly more powerful, but more sensitive, more reactive and more prone to crack from shrinkage as it cooled (partly because it was cooling from a higher temperature than TNT). Melt-cast was really the only option for artillery back then, powder filling for anything with a high muzzle velocity isn't possible because of set-back and cast cure PBX had barely started development.

TNT (with a poor oxygen balance) was also a useful way to utilise cheap ammonium nitrate in military explosives like amatols. Some of the TNT-rich ones were still melt-castable and didn't lose much performance (50/50 amatol VoD 6400ms-1) relative to pure TNT, so you lost a little destructive power per munition, but cost-for-cost you got more bang overall.

Alkoholvergiftung - 18-5-2023 at 03:52

Bevore and during WW1 French used an mix of 25% Trinitrokresol and 75% Picrid acid the meltingpoint was around 80 C. Trinitrokresol was an concurrent for picrid acid in Austria and France. it is less acidic and lass sensitive. But also water soluble.The ammonium salt was in favour too but it was to water soluble.

MineMan - 18-5-2023 at 08:45

Unpopular answer… laziness. It’s a disgrace it’s still used. Everytime a warhead detonates with black smoke Nobel cries…

B(a)P - 18-5-2023 at 12:36

Quote: Originally posted by MineMan  
Unpopular answer… laziness. It’s a disgrace it’s still used. Everytime a warhead detonates with black smoke Nobel cries…


Totally agree with this. Firstly it takes a huge amount of time an effort to optimise a process for the synthesis of an energetic compound from both a safety and cost perspective. Once that is nailed it becomes very cost prohibitive to try something new. Even when you do come up with something new you have to convince everyone else it is safe including industry and regulators. On top of that, you have the same issue with the end use, all the calculations, processes and procedures are in place for the use of the material to maximise effectiveness and safety in use.

MineMan - 18-5-2023 at 15:42

Military companies still consider HNS experimental even though it flew to the moon. This is where China, with their advance at any cost (or rather modest cost compared to the west) has the advantage.

Herr Haber - 18-5-2023 at 16:02

Quote: Originally posted by Alkoholvergiftung  
Bevore and during WW1 French used an mix of 25% Trinitrokresol and 75% Picrid acid the meltingpoint was around 80 C. Trinitrokresol was an concurrent for picrid acid in Austria and France. it is less acidic and lass sensitive. But also water soluble.The ammonium salt was in favour too but it was to water soluble.


Japan used cresols too in WWII. You use what you get from the feedstock available.
Dinitro aromatics can help lower the melting point of a mixture quite a bit but then you get leaky ammo.

About the smoke, yes... the black carbon smoke is ugly. I enjoy looking for the little white puff on top made by whatever the EOD used :)