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Petn1933
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sad.gif posted on 18-10-2020 at 07:13
lead azide trouble


hello my firends

i recently synthesized batch of dextrined lead azide.

Despite my expectations. Lead azide does not explode on direct contact with a flame and burns as fast as hmtd or NHN.
Of course, it explodes violently due to indirect heat and shock.
I'm a little confused.
Is this normal for dextrined lead azide?
If used in blasting cap at the amount of 150-200 mg, will it still burn or detonate?

thank you.
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greenlight
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[*] posted on 18-10-2020 at 09:30


That is not normal.

Lead azide should easily DDT transfer even in very small amounts. I have detonated single figure milligram quantities with direct flame.

I understand that this rapid transition is because for every N3- group that
decomposes, the stable N2 gas is formed but the third spare nitrogen atom is expelled which goes on to react with another N3 group where the process repeats again releasing another extra nitrogen atom creating a rapid chain detonation reaction even in small quantities. There could be any amount of N3- groups decomposing at the same time too.

I believe this explains why metal primary explosive azides behave the way they do in that a small number of molecules of azide decomposing can cause a large enough neighbouring amount to decompose too leading to rapid detonation of the whole pile with seemingly no deflagration stage apparent.


Maybe some impurity in your batch? What was your source of your sodium azide and reaction conditions?



[Edited on 18-10-2020 by greenlight]




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Petn1933
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[*] posted on 18-10-2020 at 10:04


Quote: Originally posted by greenlight  
That is not normal.

Maybe some impurity in your batch? What was your source of your sodium azide and reaction conditions?



[Edited on 18-10-2020 by greenlight]


It's weird for me too.
from 2.3g sodium azide obtained 5.1g lead azide at 65c
i used lab grade sodium azide.

Does dextrin moisturize lead azide?

[Edited on 18-10-2020 by Petn1933]

[Edited on 18-10-2020 by Petn1933]
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Herr Haber
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[*] posted on 18-10-2020 at 22:13


No but it can probably pick a tiny bit of moisture. I cant imagine this being a problem anyway.
How much dextrin did you use ?




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Petn1933
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[*] posted on 19-10-2020 at 02:51


Quote: Originally posted by Herr Haber  
No but it can probably pick a tiny bit of moisture. I cant imagine this being a problem anyway.
How much dextrin did you use ?


I used the method NeonPulse mentioned

http://www.sciencemadness.org/talk/viewthread.php?tid=24078&...

0.35 grams of dextrin.
Interestingly, the same problem was there.
Of course, if there is no problem in the main work, not being sensitive to the flame is not a bad thing!


[Edited on 19-10-2020 by Petn1933]
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njl
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[*] posted on 19-10-2020 at 05:55


You say you used lab grade NaN3. What about dextrin? Being a natural product it might have some impactful impurities.
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Petn1933
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[*] posted on 19-10-2020 at 07:36


Quote: Originally posted by njl  
You say you used lab grade NaN3. What about dextrin? Being a natural product it might have some impactful impurities.


I tried to use pure dextrin as much as I could.
I wish I could find out if such a thing happened to anyone.
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[*] posted on 19-10-2020 at 09:30


What about the lead salt source? Was that pure?



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Petn1933
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[*] posted on 19-10-2020 at 10:05


Quote: Originally posted by greenlight  
What about the lead salt source? Was that pure?

Yes, lab grade and pure.
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[*] posted on 19-10-2020 at 17:43


coated lead azides seem to be less sensitive to flame, but when pressed and ignited detonate with vengeance when full y dried.

I used the PVA method my self for its pressing qualities and natural resistance to moisture
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[*] posted on 20-10-2020 at 09:30


Could there be some low density issue with the powder affecting DDT transformation (density》= VOD》).

I only use the PVA coated lead azide for all detonators too.




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[*] posted on 31-10-2020 at 02:23


On the contrary, DDT accelerates with decreasing of density.
Your problem is a high content of the dextrin or impurities.
My dextrinated LA detonate from 5..20 mg depending on the concentration of dextrin. It syntes is very moody. Take polyvinyl alcohol better.

Did you filter the dextrin solution before synthesis? This is a required operation.
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Petn1933
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[*] posted on 1-11-2020 at 03:57


I synthesized lead azide again but this time i used pva and unlike dextrinated LA, it explodes violently even at very small sizes.
Thank you all for your comments.
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[*] posted on 1-11-2020 at 13:50


I personally like the PVA for it's handling and keeping properties. my sample has held up for a a couple years with no real degradation, I used some yesterday to make a fire cracker.
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[*] posted on 1-11-2020 at 21:29


Quote: Originally posted by XeonTheMGPony  
I personally like the PVA for it's handling and keeping properties. my sample has held up for a a couple years with no real degradation, I used some yesterday to make a fire cracker.


lead azide firecracker!;)
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