Whether you are looking to keep groceries fresh during transit, ship frozen across the country or ensure temperature-sensitive pharmaceuticals remain in optimal condition, “shipping” ice packs are a ubiquitous solution. With the explosion of delivered meals and pharmaceuticals during the covid years, consumers receive and handle frozen gel packs (or ice packs) constantly. Three common questions are asked:
- What is in ice packs?
- What is the composition of the gel in ice packs?
- Is the gel inside an ice pack toxic?
Let’s take a comprehensive look at these temperature-maintaining marvels.
Note: this article does not cover “therapeutic” gel packs which are a different kind of gel pack meant to be applied to the body.
What is in Ice Packs?
Inside of ice packs you will find a gel like substance. This gel is what makes the ice pack effective, especially when shipping temperature sensitive goods.
What is the Composition of Gel in Ice Packs?
The main component often found in most common gel packs for shipping is a super-absorbent polymer called sodium polyacrylate that has been adapted to the use as a refrigerant. Known for its water-loving characteristics, this polymer can retain 100 to 1000 times its mass in water.
Beyond sodium polyacrylate, manufacturers sometimes use other synthetic super absorbent polymers, such as chemically-altered cellulose (Hydroxy-Ethyl Cellulose, Carboxy-Methyl Cellulose). In rare occasions gel packs are made with natural gelling agents like gums; this was the case for the first iteration of the Terra Ice gel pack launched by Pelton Shepherd Industries in 2022.
Is the Gel in Ice Packs Toxic?
Many consumers often wonder, “Is an ice gel pack toxic?” It’s a valid query, especially when we use these packs in proximity to our food and pharmaceuticals. The short answer is “no”, the gel in gel packs for shipping is not considered toxic but to be sure, gel pack customers or consumers can refer to the product’s Safety Data Sheet (or SDS). As explained in this article from the Occupational Safety and Health Administration (OSHA), the SDS includes information such as the properties of each chemical; the physical, health, and environmental health hazards; protective measures; and safety precautions for handling, storing, and transporting the chemical.
What happens if you eat ice pack gel? Although many gel formulations are non-toxic, ingestion is strongly discouraged. Consuming the gel could result in minor digestive issues, such as nausea or an upset stomach. In households, especially those with curious pets or children, storing these packs safely is imperative. If someone ingests a substantial amount, seeking medical advice is crucial.
So, is a gel ice pack toxic? When used as recommended, the answer is no. Be sure to avoid consumption of the gel, and safety will be on your side.
The Difference Between Gel Packs and Ice Packs
People like to refer to ice packs or gel packs and there is often confusion and questions as to how they differ. The answer may be disappointing: they are the same thing.
With a few exceptions, gel packs or ice packs are all made of a water-based gel enclosed in a robust, flexible pouch. From there a distinction should be made:
What Are Therapeutic Gel Packs
They are gel packs meant to cool (or warm) the body by local application. Even when brought to typical temperature inside a freezer, the gel in these packs stays flexible to conform to the application area. They are designed to be comfortable and not too cold as not to risk cold-burning the skin. These gel packs do not stay cold for very long. They are not the main topic of this article.
What Are Shipping Gel Packs
They are the main subject of this article. They are gel packs designed to “absorb” energy (in the form of ambient heat) from the surroundings for as long as possible and at a reduced cost. The main “battery of cold” in a shipping gel pack is water. In order to transition from its solid (ice) phase to its liquid phase, water consumes a lot of energy in the form of heat. This is why a frozen gel pack keeps “removing” heat from the inside of a shipping box as it transitions from solid to liquid.
To oversimplify gel packs for shipping are the most cost-effective way to leverage frozen water for shipping. But one cannot just use frozen water to ship temperature-sensitive items. For obvious reasons, the water has to be contained as it thaws. so gel packs use a robust and flexible plastic pouch. Now, the reason gel packs use a water gel is to prevent the water from completely flowing out of the container in case of a puncture of the pouch. In general, Pelton Shepherd gels are thicker than competitors’ to reduce the risk of spill in the case of an accidental damage of the containing pouch.
Are Gel Ice Packs Safer to Use than Dry Ice?
In cold chain shipping applications, both gel packs and dry ice (solid carbon dioxide or CO2) have specific applications, advantages, and disadvantages. Like water, dry ice consumes a lot of energy (in the form of heat) when it transitions away from its solid state but it has two important differences when compared to water.
The first is the temperature of phase change. In order to change from one phase (like solid) to another, materials like water or carbon dioxide must reach a certain temperature. To simplify, water transitions to solid when its temperature reaches 32F or (0 deg C) while Carbon Dioxide (CO2) becomes solid at -109F (or -78C).
The second is that solid CO2 transitions to a gas phase at atmospheric pressure. This is convenient but also dangerous. The next chapters address safety concerns one by one:
Contact Temperature
Dry Ice: It’s extremely cold, with a temperature of about -109°F. This extreme cold WILL cause freeze burns if it directly touches the skin. Special gloves are necessary when handling dry ice.
Gel Ice Packs: With a few exceptions (like Pelton Shepherd’s Enviro Ice -12C), frozen gel packs have a surface temperature close to 32F. Though not recommended, they can be handled without gloves for a short period of time without risk of injury. However we recommend using gloves when handling frozen gel packs.
Volume Change
Dry Ice: Frozen dry ice sublimates, turning from solid directly to carbon dioxide gas. This creates a large change of volume and this gas can build up and cause an explosion if stored in a sealed container. That is probably the biggest drawback as a refrigerant for shipping: the insulated container in which dry ice ships must be ventilated which reduces the efficiency of its insulation.
Gel Ice Packs: Contrary to dry ice, frozen gel packs use slightly less volume when they thaw. Therefore they are completely safe to use in sealed containers.
Ventilation
Dry Ice: As it sublimates , it releases carbon dioxide (CO2). In confined spaces, this can lead to a dangerous buildup of CO2, displacing oxygen and potentially leading to asphyxiation.
Gel Packs: They do not release any gasses, so there’s no risk of asphyxiation or the need for ventilation.
Shipping and Travel
Dry Ice: Many airlines have restrictions on the amount of dry ice allowed on board, which must be declared. Also, there are specific labeling and packaging requirements for shipping items with dry ice.
Gel Packs: Generally easier and more straightforward to ship or travel with. They don’t have the same stringent regulations as dry ice, though checking with individual carriers is always a good idea.
Applications
Dry Ice: Useful for items that must be kept at extremely low temperatures, such as certain medical supplies or frozen foods.
Gel Packs: Particularly suitable for items that need to be kept cool but not frozen solid, such as fresh foods or medicines. However, some gel pack formulations are designed to maintain frozen temperatures such as Pelton Shepherd’s Enviro Ice -12C.
In terms of safety for general use, gel packs often come out ahead due to their ease of handling and lack of risks associated with gas release. However, the choice between gel packs and dry ice should be based on the specific needs of the application.
What Makes Gel Ice Packs So Effective?
The standout performance of gel ice packs is no accident. It’s a result of the inherent properties of the gel.
The gel in gel packs is basically water (typically more than 99%). Water has a high latent heat of fusion, meaning it will absorb a large amount of heat to transition out of its solid form (from ice to liquid water).
Water also has a relatively high caloric capacity or specific heat capacity which means it resists changes of temperature. Note that the solid form of water (ice) has about half the specific heat capacity as water. Let’s take an example to understand the contribution of the Latent Heat of Fusion vs. the heat capacities:
|
Specific Heat Capacity Water
|
1
|
BTU/lb. F
|
|
Specific Heat Capacity Ice
|
0.5
|
BTU/lb. F
|
|
Latent Heat of Fusion Water
|
144
|
BTU/lb.
|
To transition from 0F to 60F, a frozen pound of ice will consume:
- First 0.5 x (32F-0F) = 16 BTU to change its temperature from 0F to 32F (at which point it will start transitioning from solid ice to liquid water.
- Then 144 BTU to change to water at 32F.
- Finally 1 x (60F – 32F) = 28 BTU to change its temperature as water from 32F to 60F.
Contribution Of: | BTU | Percentage |
|---|---|---|
Specific Heat Capacity of Water | 28 | 15% |
Specific Heat Capacity Ice | 16 | 7.5% |
Latent Heat of Fusion Water | 144 | 76.5% |
As you can see in this example the largest contribution of the water as a “battery of cold” almost always comes from its high latent heat of fusion.
Thanks to this unique thermodynamic property, water provides a steady, prolonged cooling effect. This attribute, paired with a high availability and low cost makes it ideal for shipping temperature-sensitive items when packaged as a gel inside a reliable pouch. Now that you understand what is in gel ice packs, it’s easy to see the value they add to an organization. Businesses can be confident that their products, be it medical supplies, perishables, or cosmetics, remain at a consistent temperature throughout transit.
Find Gel Ice Packs for Your Shipping Needs with Pelton Shepherd
In the expansive world of cold shipping solutions, Pelton Shepherd has proved a beacon of reliability. With decades of experience and a commitment to innovation, they’ve established themselves as industry leaders.
Pelton Shepherd’s gel ice packs for shipping are the culmination of research and customer feedback, resulting in a product that’s both efficient and safe. Their products are tailored to various needs, ensuring that businesses, regardless of size or sector, can find a solution that fits.
For businesses, partnering with Pelton Shepherd means entrusting their temperature-sensitive shipments to a tried and tested solution. The company’s dedication to quality, combined with the unparalleled benefits of gel ice packs, makes them an indispensable asset for any shipping need.
As our world becomes more interconnected and the demand for temperature-controlled shipping rises, gel ice packs, with their unique composition and benefits, stand tall as the optimal choice. And for those seeking the best in the business, Pelton Shepherd is a name to rely on.
Frequently Asked Questions
How long can I expect gel ice packs to retain their coldness?
The short answer is “days” but it obviously depends on the size of the gel packs and the temperature and environment they are exposed to.
Gel packs used for the shipping of food and pharmaceuticals in insulated containers will maintain a surface temperature close to 32F for several days depending on the conditions.
Are there specific guidelines for transporting temperature-sensitive products with gel ice packs?
Yes, there are guidelines and best practices for shipping temperature-sensitive items. Consult our team of experts or your packaging engineer to choose the right amount and type of gel packs for your shipping needs.
What's the recommended disposal method for Ice Cold Gel Packs?
Most gel packs can be safely disposed of in the trash bin. But Pelton Shepherd gel packs offer the industry’s most environmentally friendly disposal options. Consult our dedicated page on the subject.