# Phase change gel- more info please



## mtolypetsupply (Dec 18, 2008)

I've read about the Phase change gel, and want to make absolutely sure I understand them.

If the ambient temp is above or below the temp the gel is designed for, then the gel either heats or cools appropriately, is that correct? How does it do that? Everything I've seen says they are reusable, for how long will they work? 

Where can I buy just a few?


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## pl259 (Feb 27, 2006)

That's not correct. They don't heat and/or cool. They have a predetermined amount of heat capacity. It's really about the mass. Gel packs and PCMs, of equal mass, can be compared. 

In a heating situation, where the pack is loosing heat energy to the outside world, gel packs give up their energy in a uniform manner. The temp in a shipping box with basic gel packs drops uniformly. PCMs of the same mass, in the same conditions, give up their heat energy differently. But the total amount of energy is the same. The temp in a shipping box with PCMs will stay flatter, as the materials go through their change of phase, but will then drop off sharply at the end. Similar to melting ice cubes in a glass of water, a cooling example, where ice is the PCM. 

PCMs will absorb or give up energy as the material changes phase, and it's temp will stay relative flat when it does. To a point. And that point is when the material has changed completely. One nice thing about them is that when used with a heat pack, they will absorb the heat energy from the pack and help prevent the temp from going too high. 

They are very reuseable. I don't think you'll wear them out. Check with some of our sponsors. I think some do sell them.


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## mtolypetsupply (Dec 18, 2008)

So how would one "recharge" a gel pack if they are reusable? If combined with a uniheat, they would absorb and release the heat from the UniHeat???

The duration of efficacy is dependent upon the heat loss? In the United States, for shipping overnight, will the gel pack last the duration?

Haven't found any suppliers that sell them. Anyone know exactly who to go to? We may have a buyer for a snake, and would love to be sure she's shipped safely. Uniheat works, but I worry about hot spots etc. She's a yearling, and isn't in brumation this year.


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## Baltimore Bryan (Sep 6, 2006)

You can buy them at JoshsFrogs. I just bought 4 of them.


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## Jason DeSantis (Feb 2, 2006)

Here is a link to the manufacturers website Phase 22? / 20-24° C
J


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## Dancing frogs (Feb 20, 2004)

Some good info here:
http://www.dendroboard.com/forum/parts-construction/16577-better-gel-shipping-tested.html
More common gels have a phase change buffering, but the phase change happens at 32F...hardly ideal.
Mass for mass, the phase 22 would keep the package in the ideal temp range much longer, but the less expensive gels would probably keep the package above the freezing point of water much longer.


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## pl259 (Feb 27, 2006)

mtolypetsupply said:


> So how would one "recharge" a gel pack if they are reusable? If combined with a uniheat, they would absorb and release the heat from the UniHeat???
> 
> The duration of efficacy is dependent upon the heat loss? In the United States, for shipping overnight, will the gel pack last the duration?
> 
> Haven't found any suppliers that sell them. Anyone know exactly who to go to? We may have a buyer for a snake, and would love to be sure she's shipped safely. Uniheat works, but I worry about hot spots etc. She's a yearling, and isn't in brumation this year.


In a heating situation, gel packs and PCMs are recharged the same way, they're heated. Typically they're soaked in a hot water bath. For PDFs, say to 80F. Snakes could be higher.
A UniHeat heat pad would be used outside the main shipping compartment. It limits or lowers the heat loss by reducing the temperature differential. The mass of a gel pack and the mass and materials of a PCM, would act to "buffer" any increase of the inside temps. 

Some people use heat pads inside the shipper. I've done this, but don't recommend it. 

The use of gel packs and PCMs are only one of several considerations when shipping live animals. Outside shipping temps, degree of insulation, shipping duration, and the animals temperature tolerance, are others that must be considered.

Typically, the most success is had by using shippers with all around 2" of foam insulation to limit the heat loss, using gel pack or PCMs to add heat capacity, and using a reliable overnight freight service that has "Hold for Pickup". Heat pads are usually added when the outside temps are very low. Given the above typicals, I'd use a heat pad(s) when the outside temps were 45F or lower. 

Better yet....don't ship in the winter.


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## Dancing frogs (Feb 20, 2004)

Also, if your snakes like it warmer than the low 70's, there is a PCM called exo-gel, which melts/freezes at a little warmer temp...to keep a package in the range of 24-30C, though I don't know of any place to buy a small amount...

Exo-Gel / 23-30°C


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## joshsfrogs (May 6, 2004)

A few comments...

The difference between heating up the PCMs to 80 degrees or 100 degrees+ in our experiments is negligible. The PCMs loose heat fast and then slow down greatly around 72 degrees. So, just get them liquid and you are fine. Putting them on your lights works great to "charge" them.

In our experiments, we found that they are best used when paired with a heat pack. Two phase change panels, a 40 hour heat pack, 1" foam in an 8X8X8 box and the temps are safe for 3 hours in a 0 degree freezer.

Also, keep in mind that your package will not see warmer temps than what it is outside (in both winter and summer).

An interesting aside...in our experiments, a fruit fly culture made a good substitute for a heat pack...


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## Boondoggle (Dec 9, 2007)

joshsfrogs said:


> An interesting aside...in our experiments, a fruit fly culture made a good substitute for a heat pack...


Whoah...that's interesting! How does that work?


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## pl259 (Feb 27, 2006)

FF cultures, and others, produce heat. The larve generate heat as they eat and grow. Waxworm cultures are another one that generate a lot of heat. They are very warm to the touch.


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