Could a time release polymer allow controlled endothermic reactions?

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Offline b2r1d

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I am a student at BYU and I was wondering if you could help me with some research I am doing:
Here's my idea so far:
As you know, I am trying to come up with the concept of an automatic ice pack in the form of a blanket.
However, I want to avoid using water, and I want it to look like a normal blanket.
I've decided that I'll need to find two powders that cause an endothermic reaction.
The two I came up with are:
1) barium hydroxide octahydrate and ammonium nitrate: [Ba(OH)2. 8H2O(s)   2 NH4NO3 (s) Ba(NO3)2(s)   2NH3(aq)   10H2O (1).]  crystal
2) thionyl chloride (SOCl2) and cobalt(II) sulfate heptahydrate.
I would put each (in its free flowing powder form) into little pocketsin a big cellophane sheet (like a quilt), alternating the powders (likea checkerboard).
Each pocket has small openings (or slots) on all four 'walls' of thepocket. This pocketed cellophane sheet would be sown into underneathblanket material (wool or cotton) so that it looks and has the textureof a normal blanket.
The blanket is folded carefully so the powders stay in their respective pockets.
However,when unfolded and wrapped around a person, the cellophane would bemoved so much that the powders would come out of the openings and mix,thus creating their endothermic reaction and turning the blanket intoan instant, giant ice pack.
So, the initial question I have is, for each reaction, how much of atemperature drop from room temperature could each of these reactionsgo, and how long would each reaction last?
I know that with the normal ammonium nitrate and water mixture, it goesdown to about 34 deg. F. and lasts about 15-30 mins before it goes backto room temp.
I have also decided to put a time-release mechanism so that thereactions would take a lot longer than normal. Because there are nobody fluids involved, I have to come up with some kind of medium.

The ideas I have so far are:
1) put a certain polymer/gum substance in all the openings between thepockets as a 'door-type barrier.) Then the powders from both sideswould stick against the polymer, or be absorbed, and slowly be combinedthrough the 'door' (time release polymer medium.)
2) put the powders in capsules that go through the slots between thepockets, but I would need to figure out how to get these to dissolvewithout water. The reason is, is that I want the blanket to be as lightas possible.
I know that most time release related things work with the ph in the body, but I wonder how it could work in this blanket?
What do you think, and do you have any alternate suggestions, especially regarding the time release mechanism? Thanks!
~Brooke Doud

Mod edit - formatted the subject as a question.  Please try to do this to help keep the forum tidy and easy to navigate - thanks!
« Last Edit: 31/07/2008 10:21:24 by BenV »