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Author: Subject: PTFE Magnesium thermite fun
Hazard to Others

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[*] posted on 7-11-2013 at 06:50

Quote: Originally posted by IndependentBoffin  
My thermochemistry is a bit rusty (last did the sums more than a decade ago) but here are the reaction calculations. Please feel free to correct me if you spot a mistake.

Overall equation: 2Mg + (C<sub>2</sub>F<sub>4</sub>;)<sub>n</sub> -> 2MgF<sub>2</sub> + 2C

Mg + F<sub>2</sub> -> MgF<sub>2</sub> ................................ ΔH<sub>f</sub> = -1124 kJ/mole

2C + 2F<sub>2</sub> -> -(C<sub>2</sub>F<sub>4</sub>;)<sub>n</sub>- ................................ ΔH<sub>f</sub> = -832.6kJ/mole

Heat of reaction = 832.6 - 2×1124 = -1416 kJ for 2 moles of Mg and 1 mole of (C<sub>2</sub>F<sub>4</sub>;)<sub>n</sub>.

Because I am an engineer and tend to think in terms of specific energy this gives 1416/(2×12 + 4×19 + 2×24.31)kJ/g or 9.526 kJ/g of reactants.

As you can see in the chart, regular flash powder ranks high with -10.59 kJ/g, but more importantly for munitions -27.38 kJ/cm3. To slow the reaction of flash powder, one can use dissolved nitrocellulose as a binder. This makes for a spectacular igniter.
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[*] posted on 26-2-2014 at 12:52

I know this has been dead for a while, but I here is a good read on the subject:

Attachment: (MTV-1) Magnesium-Teflon-Viton Pyrotechnic Compositions.pdf (1.8MB)
This file has been downloaded 709 times

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