What is the coldest freezer pack material that can stay soft?

[Mr_Orange]

Hello, I'm trying to create the coldest freezer pack that is still soft and pliable. (Or will at least soften up within 10 minutes). It should also ideally stay cold for as long as possible.

I've experimented with a few options so far and Water + Glycerin seems pretty good. If you add just a small percentage of glycerin, it's actually like a packed snow consistency. It can feel hard if you press on it softly, but when you apply more pressure, it crumbles easily.

What i want to improve on is it's ability to freeze even colder (ideally -30C which is my chest freezer temp) and stay cold for longer. Water seems to hold cold temperatures longer than most other liquids I've tested (i think it's called the heat of fusion right?), but then I tested this one coldpack from Walgreens called Cryomax. This seems to stay cold even longer than water (problem though is it's actually hard out of the freezer). Here's the cryomax: http://www.modularthermaltech.com/products/index.html.

So is there anything i can add to the water + glycerin concoction to make it freeze colder, stay cold longer, but still be soft and pliable right out of the freezer?. I've heard salt and starch might help and wrapping the pack in neoprene will too.

This cold pack is going to be integrated into a protective sports cooling vest design so that its why it needs to be somewhat soft and cushy. Also, it needs to be non toxic.

Any ideas?

 

[phinds]

I don't know anything about this stuff, but I would think oil would be a better bet than water and water with antifreeze in it might also be good. After all, your car doesn't freeze up in subfreezing temps.

 

[Mr_Orange]

Glycerin is pretty much a nontoxic antifreeze from what I've researched.

As far as oils go, I've tried coconut oil and it just goes rock solid very fast. Any other oil recommendations? This can't be easily flammable too,

I've tested some 'phase change packs' and they work pretty well actually. They don't get too cold but can stay cold for very long, and they don't cause condensation. The only problem is they're solid right out the freezer and stay solid for a long time. Eventually though, they do melt into a perfectly snow like consistency. Apparently some are made of oils, but i think it's probably a concoction of other ingredients as well.

Is it possible to make a soft pliable phase change pack?

Maybe antifreeze + phase change material?

I'm hesitant about mixing different chemicals together without asking first since this thing has to be non toxic and non flammmable.

 

[phinds]

NOW you tell me it has to be non-flamable

Nah, I'm drawing a blank under that constraint

 

[Mr_Orange]

I'm open to any ideas on oil and phase change materials you might have. I think technically a lot of the phase change materials being sold are flammable. Ideally, i'd prefer if they weren't.

The concept is to make protective sports padding (action sports, football, etc) that also doubles as cooling pads. You can stick them in the freezer before use. If the material leaks, it can't harm the athlete.

 

[Mr_Orange]

Btw, does anyone know a way to make a super cold freezer (below -80 C). All those types of freezers are very expensive. I want to experiment with this concept to see if i could extend the cooling period of these pads.

Maybe the coolant can be positioned on the pad in way so that it doesn't come in direct contact with the body. Maybe it just provides ambient cooling (if that's even possible).