What is Phase Change Material (PCM)?
When we’re talking about PCM, there are so many sets of different concepts to mention. Actually Phase Change Material (PCM) brings an advanced thermal protection when transporting a kind of temperature-sensitive products. When PCMs has been melt and frozen, or change phases of matter between solid and liquid, they will maintain a constant temperature which is equivalent to their melting/freezing point. 
They are especially formulated to change phases at specific temperatures to match the payload requirements.
The best way to demonstrate this effect is to think about it in terms of water, which is also used as a PCM. Of course water’s solid/liquid phase change point is 0°C. In order to keep a cold product in warmer weather, water must be cooled below its phase change temperature until it freezes and becomes ice. When the ice is placed in a package around the temperature-sensitive product, it forms a 0°C thermal barrier between the product and the outside environment’s temperature. The ice begins absorbing the surrounding heat and starts to melt. As the ice melts, it maintains that 0°C temperature barrier and continues to absorb the heat until it has exhausted its thermal capacity and completely liquefies. 
At this point, the temperature of the water begins to rise above 0°C rapidly until it reaches equilibrium with the ambient temperature.
A Phase Change Material will work the same way to protect the product, but the temperature that it maintains is its own innate melting/freezing point, which will be different than water. For example, a PCM with a phase change point of 5°C is more appropriate for a 2-8°C application because it will maintain a temperature within the application range, whereas water will not at 0°C.
One of the most important things to keep in mind when utilizing a phase change material is its optimal starting temperature condition. Certain applications might require you to condition your PCM as a solid prior to shipment, while others will require you to condition as a liquid. This is dependent on whether heat is overall being gained or lost by the package during shipment. (The PKI’s team can guide you to the proper conditioning method for your application.)
Whether a product needs to be kept frozen, refrigerated or at room temperature, PKI offers a variety of Phase Change Materials that are safe and effective thermal management solutions for products shipped within the cold chain.