The Science Behind How Ice Packs Keep Your Products Cold During Shipping

image source

Americans ship millions of packages daily, many of which need to stay cold during transit. Gel ice packs are a popular solution for keeping frozen food and pharmaceuticals safe during shipping.

Reusable ice packs usually contain a mixture of materials that keep them cold and flexible, like propylene glycol (an antifreeze chemical), hydroxyethyl cellulose, or vinyl-coated silica gel.

Temperature Reduction

Whether you’re sending food or biomedical supplies, these items must stay within a specific temperature range from start to finish. Our ice packs work to regulate and maintain that temperature so your products remain fresh from point A to point B.

Most ice packs contain a mixture of gel, water, and other refrigerant chemicals. The exact mix varies depending on the style of the ice pack and the manufacturing process.

For example, instant ice packs are usually made with two bags inside—one bag contains water, while the other holds a chemical reactor like calcium ammonium nitrate. When you squeeze the pack, the two ingredients mix and start a reaction that lowers the water’s temperature to almost freezing.

While the chemical reaction in an ice pack is safe, it can still be harmful if your child or pet accidentally ingests it. If that happens, always seek immediate medical attention.

To get the most out of your ice pack, choose a container that is the right size for your shipment. More space can reduce the cooling power of the product and increase the chance that your items will shift during transit. Please seal your shipment tightly with a tight-fitting lid and packing tape. This will minimize the risk of your cold packs moving or leaking during transit.


Despite their small size, ice packs can keep products cold for quite some time! They’re made of various materials that keep them rigid and flexible, though the exact composition can vary between brands. Reusable ice packs usually contain a mixture of propylene glycol (an antifreeze chemical), water, dye, hydroxyethyl cellulose, and vinyl-coated silica gel to create a thick liquid that’s cold and flexible. On the other hand, instant eco friendly ice packs for shipping are typically filled with water and ammonium nitrate. Once the water in the ice pack is popped (by applying pressure to the plastic packaging) and mixed with the ammonium nitrate, an endothermic reaction freezes the ice pack and keeps it cold.

Both types of ice packs are effective for insulated shipping and can maintain product temperatures within their designated ranges. However, if your products are highly susceptible to environmental fluctuations, reusable cold packs offer a safer, more convenient option. This is especially true for biopharmaceutical products, which must remain at a controlled room temperature to ensure patient safety.

Heat Capacity

When shipping perishables, your products must arrive in the best condition possible. This means that you need a high-quality insulated liner to keep the temperature of your foods or medical samples in the optimal range. Then, you’ll want to add ice packs or refrigerant gels to maintain the cold temperature.

Many ice pack styles are designed with specific applications in mind. For example, some are thin enough to fit easily into lunch boxes or coolers, while others are meant to remain cold for extended periods—like when used for long car trips or medical procedures. These ice packs usually contain liquid or a refrigerant gel formulated to last for hours, even in a freezer.

One of the main reasons ice packs can stay so cold is that they can absorb an extraordinary amount of heat through the latent heat of fusion. This process requires a lot of energy, but the result is a dramatic reduction in temperature.

Some ice packs are made with propylene glycol, an organic compound similar to antifreeze. It’s a viscous, colorless liquid with no odor and is miscible with various solvents.

Moisture Reduction

As a bonus, ice packs also help reduce extra moisture in your packages. This can help prevent the products from absorbing humidity and potentially becoming damaged in transit.

The simplest way to keep an ice pack cold is to store it in your freezer until you are ready to use it. You can also use hot water to warm it up if you want the pack to reach a warmer temperature. The first reusable ice pack that could be cold or warm was invented in 1948 and called the Hot-R-Cold-Pak.

Dry ice should be stored in a ventilated area and disposed of properly so it does not freeze any fixtures or cause damage to your packaging materials. Always use protective gloves and avoid skin contact with dry ice as it is freezing.

Gel packs are a good choice if you have sensitive hands or prefer not to handle dry ice. They freeze at a lower temperature than water and thaw at the same rate, so they will help to prolong the life of your frozen food in transit. The soft exterior of this gel pack allows you to bend and shape it to fit your package and cooler, and the leakproof design makes for a great option if your packages sit in the sun or a humid environment.

Leave a Reply

Your email address will not be published. Required fields are marked *

This site uses Akismet to reduce spam. Learn how your comment data is processed.

Fighting Free Radicals: How Antioxidants Protect Your Body

Fighting Free Radicals: How Antioxidants Protect Your Body

There are so many ways that the health industry and the media have tried to

5 Skin Care Techniques You Should Try for a Clear Complexion 

5 Skin Care Techniques You Should Try for a Clear Complexion 

  Ugh, that moment when the dreaded pimple appears

You May Also Like