Whether you need 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 increasing popularity of delivered meals and pharmaceuticals, consumers receive and handle frozen gel packs (or ice packs) frequently. Three common questions are asked:
- What is in ice packs?
- What is the composition of the gel in gel ice packs?
- Is the gel inside a gel 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 type of gel pack meant to be applied to the body.
What Is in Ice Packs?
Ice packs contain a gel-like substance. This gel makes the ice pack effective, especially when shipping temperature-sensitive goods.
What Is the Composition of Gel in Gel Ice Packs?
The gel in gel packs is typically composed of water and sodium polyacrylate, a super-absorbent polymer capable of holding significant amounts of water. Manufacturers may also utilize synthetic super-absorbent polymers like chemically altered cellulose. In the past, some hard-shell reusable ice packs used to contain hazardous substances like diethylene glycol or ethylene glycol, prompting recalls.
Is the Gel in Ice Packs Toxic?
Consumers often wonder if ice gel packs are toxic. It’s a valid query, especially when we use these packs in close proximity to our food and as refrigerants for 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 end users can refer to the product’s Safety Data Sheet (or SDS).
The SDS includes information such as:
- The properties of each chemical
- Potential physical, health and environmental health hazards
- Protective measures
- 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 of ice pack gel, seek medical advice immediately.
So, is a gel ice pack toxic? When used as recommended, the answer is no. Be sure to avoid consuming 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 about how they differ, but 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. There are, however, differences between therapeutic gel packs and gel packs for shipping.
What Are Therapeutic Gel Packs?
Therapeutic gel packs are intended 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 to avoid cold-burning 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?
Gel packs for shipping are designed to “absorb” energy in the form of ambient heat from the surroundings for as long as possible and at a reduced cost. Water is the main “battery of cold” in shipping gel packs. To transition from a solid (ice) phase to a liquid phase, water utilizes energy in the form of heat. That is why a frozen gel pack keeps ‘removing’ heat from the inside of a shipping box as it transitions from solid to liquid.
Gel packs for shipping are the most cost-effective way to leverage frozen water for shipping. However, 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 incorporate a robust and flexible plastic pouch. The reason gel packs use a water gel is to prevent liquid from flowing out of the container in case of a puncture. Pelton Shepherd gels are generally thicker than competitors’, and our pouches are puncture-resistant, reducing the risk of spills.
Are Gel Ice Packs Safer to Use Than Dry Ice?
In cold chain shipping applications, 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 compared to water.
- The temperature of phase change: 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 a solid when its temperature reaches 32°F (0°C) while carbon dioxide (CO2) becomes solid at -109°F (or -78°C).
- Solid CO2 transitions to a gas phase at atmospheric pressure: This property is convenient but also dangerous.
The following safety considerations highlight the differences between gel packs for shipping and dry ice:
1. Contact Temperature
Dry Ice: It is extremely cold, with a temperature of about -109°F. This extreme cold WILL cause cold burns or frostbite if it touches the skin. Special gloves are necessary when handling dry ice.
Gel Ice Packs: With a few exceptions, such as Pelton Shepherd’s Cryo Ice™, which maintains a temperature lower than 25°F, frozen gel packs have a surface temperature close to 32°F. These gel packs are much safer than dry ice and can be handled without gloves for a short period without risk of injury. However, we recommend using gloves when handling frozen gel packs.
2. Volume Change
Dry Ice: Frozen dry ice sublimates, turning from solid directly to carbon dioxide gas. This creates a large volume change, and gases can build up and cause explosions if stored in sealed containers. This is a significant drawback when it is used as a refrigerant for shipping, as the insulated containers in which dry ice ships must be ventilated, reducing the efficiency of the insulation.
Gel Ice Packs: Unlike dry ice, frozen gel packs require less additional volume as they thaw. They are therefore completely safe to use in insulated, sealed containers.
3. 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 gases, so there’s no risk of asphyxiation or the need for additional ventilation.
4. Shipping and Travel
Dry Ice: Many airlines restrict 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 use for shipping or traveling. Gel packs don’t have the same stringent regulations as dry ice, though checking with individual carriers is always a good idea.
5. Applications
Dry Ice: Useful for items that must be kept at extremely low temperatures, such as certain medical supplies or frozen foods.
Gel Packs: Suitable for multiple applications. By selecting the right gel pack, items such as fresh foods or medicines can be kept cool but not frozen, while products such as frozen meat or ice cream can be shipped at frozen temperatures.
In terms of safety for general use, gel packs have the advantage 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 each application’s requirements.
Dry ice remains a popular option to avoid temperature excursions when shipping frozen products. Supplementing it with Cryo Ice™ Gel Packs offers a dependable solution to achieve prolonged temperature control.
What Makes Gel Ice Packs So Effective?
The gel in gel packs is typically more than 99% water. Since water has a high latent heat of fusion, it absorbs a large amount of heat to transition out of its solid form (from ice to liquid water).
Water also has a relatively high caloric or specific heat capacity, which resists temperature changes. Note that ice has about half the specific heat capacity of liquid 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 0°F to 60°F, a frozen pound of ice will consume:
- First 0.5 x (32°F-0°F) = 16 BTU to change its temperature from 0°F to 32°F (at which point it will start transitioning from solid ice to liquid water).
- Then, 144 BTU is changed to water at 32°F.
- Finally, 1 x (60°F – 32°F) = 28 BTU to change the temperature of water from 32°F to 60°F.
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.
This unique thermodynamic property gives water a steady, prolonged cooling effect. This property, paired with 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 how they add value to shipping logistics. Businesses can be confident that their products, whether medical supplies, perishables or cosmetics, remain at a consistent temperature throughout transit.
Find Gel Ice Packs for Your Shipping Needs With Pelton Shepherd
With over seven decades of experience and a commitment to innovation, we continue to lead cold chain supply technology. Our gel ice packs for shipping are the culmination of research and customer feedback, resulting in efficient and safe products.
Partnering with Pelton Shepherd means entrusting your temperature-sensitive shipments to a tried and tested solution. Our dedication to quality and unparalleled gel ice pack technology makes us an indispensable resource you can rely on when you need precise temperature control in cold chain shipping.
As our world becomes more interconnected and the demand for temperature-controlled shipping rises, Pelton Shepherd gel packs for shipping are the optimal choice. Find out why we are the trusted cold chain shipping partner for premium brands, including Boehringer Ingelheim, CVS, Hungry Harvest, HelloFresh and Mighty Meals.
For more information about replacing dry ice in your cold chain shipping operations with safer gel pack alternatives, contact the experienced team at Pelton Shepherd!
Frequently Asked Questions
How Long Can I Expect Gel Packs to Retain Their coldness?
It depends on the size of the gel packs, the temperature and the environment in which they are being used.
Gel packs used for the shipping of food and pharmaceuticals in insulated containers can maintain a surface temperature close to 32°F for several days, if they are packaged correctly.
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 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. Pelton Shepherd gel packs offer the industry’s most environmentally friendly disposal options. Our Nutri Ice™ gel packs include pouches made from 30% recycled plastic, and the gel is safe as a plant food and drain safe, maximizing the chances of it being diverted from landfills.
