I've been using Cryopak Phase 22 panels all summer. From the
website:
Phase 22™ keeps product between 20-24 (C) degrees during shipment in hot or cold environments.
This phase change material is ideally suited for the shipment of blood products, tissues, pharmaceuticals, live animals and plants that must remain in the 20°C to 30°C range.
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There is a lot of information about PCM panels on dendroboards, and you can buy them singly from Josh's Frogs. Apparently frog breeders have been using these for several years. I bought a case of both the hard panels and the soft gel packs. I prefer the panels. I generally use two in a 6 x 9 x 12 box. My contact at TCP Reliable is Donna Swisher.
In one test I did I drove From FL to KY with a snake packed as it would be for shipping, with PCM panels, with temp probes on the snake and on the panel. I didn't use the AC and let the temp in my truck get up to 95 for hours. The temp in the shipping box stayed at 72 the entire time.
I used these a little bit last winter, but hadn't had them very long before summer shipping started. I have also done two-phase shipping going from hot Florida to medium Memphis to cold destination, where I would start with frozen PCM panels, as well as a 40 hour heat pack in a deli. The PCM panels would thaw gradually and end up at 72, and the heat pack would then keep the snake warm for the rest of the trip.
Prep for the panels is freezing them for hot weather shipping and heating them to about 90F for cold weather shipping.