Comp. B

[10fingers]

Composition: % by weight
RDX (MIL-R398) 60
TNT (MIL-T-248) 39.5
Wax (MIL-W-20553) 1.0

Properties:
Density 1.72 g/cm3
Heat of combustion 11.67 MJ/KG
Heat of detonation 5.28 MJ/KG
Detonation Velocity 7900 m/s
Detonation Pressure 29.5 Gpa
Sand test brisance,
(compared to TNT=100) 110
Min. charge of Lead Azide
to detonate sample. 0.22 gram

Preparation:
1. TNT is melted in a steam heated, jacketed kettle to a temperaute of 95*C.
2. The molten TNT is stirred to maintain a uniform temperature throughout the mix.
3. A water slurry of RDX is added slowly to the TNT.
4. After all RDX has been added, the heating and stirring of the kettle's contents is continued until most of the water is evaporated.
5. Wax mixture is added gradually and blended thoroughly into the mixture.
6. Final mixture is cooled to the desired fluidity for casting.

[cutefix]

Composition B is a binary explosive commonly used in filling mortar shells and smooth cased fragmentation grenades.
Many Land mines made in other countries aside from USA are using it for mine filling...

[Zambosan]

Hmm... is a composition like this really referred to as a binary explosive? Both TNT and RDX are detonable by themselves, and I don't believe either one has a sensitizing effect on the other. Not trying to nit-pick, just making sure my understanding of the terminology is correct for future reference.

[cutefix]

This particular cast binary composition was made in order to improve the strength of TNT and also to make RDX less sensitive to be more suited for ordnance application.In those times during the second world war, cast explosives containing TNT as the energetic plasticizer were already in existence;in fact many compositions were actually used with varying crystalline explosives in military application.
PETN and TNT resulted in Pentolite
Tetryl and TNT produced Tetrytol
Picric Acid and TNT yield Picratol,etc.,.
There are many other binary blends;and difinetly the reason is to make TNT more powerful as the addition of these crystalline explosives really improve its performance;but with the side effect that many of these blends resulted in increased impact sensitivity if compared to TNT itself.
BTW, comp B was developed in the later period of World war II as RDX was still not plentiful enough for many application,and its large scale synthesis is still considered expensive compared to other explosives then....

[Zambosan]

Okay, thanks. I was under the impression that a binary wasn't just any two-component explosive, it was specifically one whose individual components were not detonable in and of themselves and could therefore be handled, stored, and shipped without much care (e.g. ANNM).

[10fingers]

Comp. B is used a lot in shaped charge warheads. The first US bazooka, the 2.36 in., used pentolite which was 50/50 PETN/TNT, but this was changed in the 3.5 in. to comp. B because of it's higher penetration.
The current LAW, (light antitank weapon) uses octol which is a blend of HMX and TNT which gives a 20% increase in penetration over comp. B.

[cutefix]

I think the well known anti-tank weapon that really used octol was the Shillelagh anti-tank missile that was designed to be fired from the gun of the Sherman tank and other older tanks;that before the arrival of MBT Abrams which is not compatible to the operating system of the shillelagh missile..
But it was decommisioned even before it saw combat.. :(
BTW, this octol was reputedly used as filler in the HE shell in the latest 40 mm grenades.
Meanwhile comp. B was more powerful than pentolite because the common ratio of its formula was 60/40.If it was used as 50/50 RDX/TNT,I like pentolite(50/50PETN/TNT) could not have made much difference in penetration comparison…with the shaped charge jet.. <img border="0" title="" alt="[Wink]" src="wink.gif" />

[10fingers]

That's a good point and something I was wondering about. Could it be that pentolite is only 50% PETN because at higher levels it's too sensitive for military use? I have seen a reference to PETN/TNT mixtures that say it can be used in levels up to 65%.

[cutefix]

Yeah,I think it was the most practical for military purposes as PETN is rather sensitive…Increasing it by certain amount in cast explosives is not desirable,as preparing these composition is rather messy.. and the crystalline explosives had tendency to settle out also on storage in cast compostion,specially if the ratio of these explosives is more in favor of the crystalline material.
This distinct crystals of PETN that may separate may cause premature detonation during handling and increasing the level of this will also offset the resulting composition balance; and this will promote segregation and it will be detrimetal to stability on storage.
PETN behaves differently from RDX is melt-cast composition.You have more flexiblity with hexogen than with Penthrite.

<small>[ June 27, 2002, 05:04 AM: Message edited by: cutefix ]</small>