Tetranitrocarbazol

[Bellifortis]

In the beginning of WW2 the military had great problems with especially pyrotechnic cartridges. Too many duds because of percussioncap failures. Investigation revealed that these were caused by ingress of moisture which caused a chemical reaction between Magnesium that produced, in combination with the sulphur of the Black Powder propellant and igniter comp hydrogensulphide gas that attacked the leadcompounds of the percussion caps. When this was realised Tetranitrocarbazol was exchanged for black Powder in many items, even in bombfuze igniters. After WW2 one does not hear about this any more and as a worldwide industry standard Black Powder again is used in these applications. Does anybody here have any explanation for this ?
Bellifortis.

 

[BMG50]

I know the biggest failure rate for German S mine 35 was the use of black powder between ignter and the dets. After the 4.5 second fuse was ignited (black powder) then the propellant charge (black powder) then the three .5 second fuses to set of the det tubes (black powder). It was said that the S mines became unreliable and erratic after being 3 months in the ground (desert), some bounding above normal and not going off, some not going off at all. This is why the S mine 44 was developed as it relied on a mechanical mechanism, pull wire and pull igniter to the main charge, the propellant sealed in a celluloid tube.
The 2" mortar smoke, star shells and para illum also had moisture problems to start as their initiating charges failed to ignite the main filling. You can see the different tail adaptor changes to sort this out.

 

[TimG]

It would appear the UK had identified these problems at a very early stage. Almost all UK pyrotechnic compositions contaning magnessium powder (there are a lot), the powder is first treated by adding one of the following: Boiled Linseed Oil, Lithographic Varnish or Beeswax.

The sulphur problem was known about and utilisation of sulphurless gunpowders avoided the issue. But charcoal presents the problem of being hydroscopic.

T.N.C. which acts as a fuel, is a good substitute for charcoal in 'gunpowder' when mixed with potassiun nitrate. However, it can be difficult to ignite as the T.N.C. melts prior to ignition.

T.N.C. was used in SR. 112, unfortunately I don't have any details as to its function or composition. Furthermore, it would appear T.N.C. found favour in the early 60s when slow burning pyrotechnic delays were being developed.

TimG

 

[Bellifortis]

Thank you Tim for that interesting answer. I wondered, because everybody should have had these problems. I got to think about this problem again, when the empty "Emergency Flare Tin" was shown in another thread. These tins were soldered airtight and were never to be opened but in an emergency. They had that small wire-key, like in old sardine tins, fastened to the top. These were specially packed emergency pyro-items for long term storage. US research in WW2 showed, that the only watertight packing is a soldered tincan even for simple pyro items like matches. The Mg treatments you mention will all lower the illuminating-, colour- and burning-efficiency. So i would expect these will not be used in modern high-efficiency pyro-items.
Regards,
Bellifortis.

 

[Bellifortis]

It would appear the UK had identified these problems at a very early stage. Almost all UK pyrotechnic compositions contaning magnessium powder (there are a lot), the powder is first treated by adding one of the following: Boiled Linseed Oil, Lithographic Varnish or Beeswax.

The sulphur problem was known about and utilisation of sulphurless gunpowders avoided the issue. But charcoal presents the problem of being hydroscopic.

T.N.C. which acts as a fuel, is a good substitute for charcoal in 'gunpowder' when mixed with potassiun nitrate. However, it can be difficult to ignite as the T.N.C. melts prior to ignition.

T.N.C. was used in SR. 112, unfortunately I don't have any details as to its function or composition. Furthermore, it would appear T.N.C. found favour in the early 60s when slow burning pyrotechnic delays were being developed.

TimG

Hi Tim,
yours is the first intimation I have that TNC comps had problems with ignition. Do you have any comparative test-literature you could recommend ? I have not seen the 2 CIOS reports 25-18 and 25-56 dated 1945. If anybody knows where this can be accessed I would be grateful.
Regards,
Bellifortis.

 

[TimG]

Bellifortis,
There was only a passing mention that igniting T.N.C. could be a problem as it melts. It has a melting point of about 285C.

It was found that in some compositions of magnesium and Lithographic varnish (which is essentially a refined Linseed oil) that the 'Specific Light Output' was increased by 33%.

Post war, when the U.S. were developing igniters for solid fuel rocket motors, they were using magnesium and Teflon. This developed into the 'MTV' compositions: magnesium, Teflon and Viton, the last being used as a binder. These compositions are used as 'IR' Decoy Flares.

TimG

 

[Bellifortis]

@TimG,
I had a conversation with a man whose grandfather was a producer of signaling cartridges in WW2. He told me that his grandfather was arrested for sabotage and high treason, with a death penality hovering over him if convicted. He was brought to Berlin to stand trial. Witha great effort cartridge-boxes were brought back from Russia. The grandfather could prove that he had manufactured all cartridges according to the specifications given and in the end he was released. Only in 1945 all producers had to press on all magnesium comps an intermediate comp. barrier of TNC-KNO3-Al, so that there was no Sulphur in contact with the Magnesium. The SR 112 is a british igniter comp that was developed after WW2 and contained 40% TNC and 60% KNO3. For many years pyrotechnists have been searching for a comp to replace Black Powder without BP's drawbacks. In his 1965 publication the well known british pyrotechnist Cackett wrote, that TNC was 1 of the 2 best replacement comps.
Happy Easter,
Bellifortis.