Phase change materials (PCMs) are materials that absorb and release thermal energy during the process of melting and freezing. When a PCM melts, it absorbs the heat from the environment, yet its temperature stays at the melting point until totally liquid. Conversely, when a PCM freezes, it absorbs the cold from the environment, yet stays at its temperature until totally solid. This makes PCM an ideal, passive solution for a variety of applications that require temperature control. The most common PCM is water/ice. Ice is an excellent PCM for maintaining temperatures at 0°C. But water’s freezing point is fixed at 0°C (32°F), which makes it unsuitable for most temperature sensitive applications.
Cool Cube™ PCMs offer custom temperature holds based on their melting point. The PCM inside Series 4 panels has a melting point of 4.5°C/40.1°F. When panels are solid, contents within the Cool Cube™ stay cool (at fridge temps around 4.5°C) in hot conditions during an extended period of time. When panels have liquid inside, contents within the Cool Cube™ won’t freeze (again at fridge temps around 4.5°C) in extreme cold during an extended period of time.
When the panels have reached 4.5°C and are completely solid, they are ready to hold your product. To verify that they are solid simply shake the panel. If you shake the panel and it feels and sounds slushy, with some liquid and some solid it will hold your product at a cool temperature, but it won’t hold it as long as if the panel is completely solid. If you shake the panel and it feels and sounds completely liquid, put the panel back into the freezer/refrigerator and continue to condition until the panel has reached a solid state.
Shake a panel at various times to get to know your panels. For example, shake the panels when you know they are warm to hear and feel how they react when they are liquid.
Within this webpage are several methods for conditioning your PCM panels. The standard conditioning method is performed in the refrigerator. The advantage of the refrigerator is that your panels won’t get too cold. This method can take from 8-24 hours. Alternatively, if you need to use your panels sooner than 8-24 hours, they can be conditioned in a freezer.
PCM panels can be frozen too cold, but there is an easy solution when this occurs. When the panels are frozen to a point below 0°C/32°F, a short staging period is necessary to safely transport your product. If your panels have been stored in the freezer simply take the panels out of the freezer and lay them, individually (unstacked), on a flat surface at room temperature for roughly 30 minutes.
Hold times of the PCM panels vary depending on Cool Cube™ size and desired holding temperature. For example, when properly packed-out into the Cool Cube™ 08, the Series 4 PCM panels can hold the cooler at a temperature below 8°C and above 2°C for 76 hours.
With all pack-out procedures, be sure to use a temperature monitoring device to consistently and accurately monitor the temperature your payload for the entire time it is held in the Cool Cube™. Some regulatory bodies such as the CDC require the use of a certified data logger. VeriCor carries several types of thermometers and digital data loggers that meet the CDC recommended guidelines.