deltaH
Dangerous source of unreferenced speculation
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Registered: 30-9-2013
Location: South Africa
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Cyanurate fire fighting plaster
I have this backyard chemistry project that I've been working on for a couple of months and wanted to get feedback on it, so am posting it here.
It's actually open innovation that I have decided to release into the public domain and it's an ongoing project, so we'll see how it evolves with
time. It's all being done from home for now, so any help is most welcome especially with those who have access to much more than I do!
Okay, so the idea is for a new kind of ceiling plaster designed to actively fight fires and not simply retard them like traditional gypsum based
plasters do.
Some background: Gypsum plaster retards the spread of fire early on because it contains a significant amount of crystal water (as calcium sulfate
dihydrate) that evaporates and so provides a cooling effect when a fire starts, however, this is only temporary and once exhausted, the fire can
quickly get out of control.
My idea was to use a mixture of calcium cyanurate and calcium carbonate to make a plaster that would first provide an equivalent cooling effect (from
hydrates of the cyanurate salt), but then if temperatures continued to climb, it would gradually start releasing carbon dioxide gas incrementally and
eventually a lot of it. This would actively fight the fire and not just retard it!
You make it thus: Boil down with constant stirring a mixture of one part (mole basis) slaked lime, two parts cyanuric acid and two parts calcium
carbonate powder (I used finely powdered purified white marble powder that was locally available cheaply) until you obtain a white free flowing
powder. It's like porridge, but you have to be careful that you don't heat it too fast and also stir properly constantly scrapping the bottom or it
will splatter scolding hot plaster on you that can give seriously nasty burns!
The white product presumably consists predominantly of anhydrous monocalcium dicyanurate intimately mixed with/on calcium carbonate fine powder.
Now when you add water, the monocalcium dicyanurate hydrates quickly (to an octahydrate?) and causes the plaster to set firm in several minutes,
though it's still somewhat soft at this stage, it hardens more over 24h, then hardens a lot over a couple of weeks.
Now when you heat it to around 100C, you lose crystal water just like gypsum plaster does, but then if you continue heating, you can switch over to
producing carbon dioxide gas, probably starting from about 250C.
How? From the literature (see attached) monocalcium cyanurate decomposes to isocyanic acid and tricalcium cyanurate starting at about 240C. This is a
really useful property as you generate a volatile acidic gas in situ and so in theory can make a solid state neutralisation reaction proceed
easily where others would required prolonged milling together as they could only react on touching solid surfaces.
What's more, it doesn't stop there, raise temperatures further and you end up decomposing tricalcium cyanurate and calcium cyanate into calcium
cyanamide and much more CO2.
All in all, theoretically, you can end up producing up to 175 standard liters of CO2 per kilo of set plaster if you follow through with all the
reactions!
I have more technical information about this idea can be found at:
http://ideashack.org/category/smart-materials/fire-fighting-plaster-smart-materials/
Including all the chemical equations here:
http://ideashack.org/2013/08/30/how-does-cyanurate-fire-fighting-plaster-work/
I've entered this idea into a local innovation competition, hoping that works out...
Attached is an excellent paper about cyanurates that I have seen do its rounds right here on sciencemadness.org!
Here you can read all about the decomposition behavior of calcium cyanate salts and such.
See a picture of a casting of my plaster here:
http://ideashack.org/2013/10/01/pic-of-fire-fighting-plaster-casting/
Thanks!
Attachment: Cyanuric Acid and Cyanurates .pdf (332kB)
This file has been downloaded 971 times
[Edited on 2-10-2013 by deltaH]
[Edited on 2-10-2013 by deltaH]
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papaya
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Why fire won't self extinguish by the self generated CO2 from combustion ?
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deltaH
Dangerous source of unreferenced speculation
Posts: 1663
Registered: 30-9-2013
Location: South Africa
Member Is Offline
Mood: Heavily protonated
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Hi Papaya
| Quote: | | Why fire won't self extinguish by the self generated CO2 from combustion ? |
Depends on the availability of air in a burning building, it's a competition for air coming in and hot CO2 leaving fast enough, but add much more CO2
as well as heat absorbtion at the same time and you have the basic ingredients of a fire extinguisher 
I'm hoping to have this formally tested in a fire laboratory someday where they actually plaster a control room and set fire to furniture and such and
simulate a real fire. They would monitor with sensors all the temperatures with time. Then you can compare to the same situation with and without the
plaster and hopefully we would see a big difference in the two, but I'm far away from that for now.
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