Cold Packs, also referred to as ice packs, are widely used in medical and food preservation industry. Compared to regular ice, they are more convenient, leak-free and easily contours as a liquid existence.
In the medical field, cold pack is an important element in first aid treatment for soft tissue injuries. It helps reduce pain and swelling. As set in the ANSI (American National Standards Institute) guidelines, cold packs with minimum sizes of 4″ * 5″ are required contents for workplace safety. Also, with increasing demand in cold therapies, they are designed with varied shapes and sizes targeting different parts of body.
In the food preservation field, ice packs have become more and more popular for personal and family use, in addition to commercial use for food transportation. For different applications, gel cold packs are designed in flexible cube mats or assorted shapes to wrap around bottles, cans and containers.
There are two types of ice packs on the market: disposable and reusable. Generally, disposable ones are based on heat-adsorbing reactions while reusable packs take advantage of the high heat capacity of water.
Instant Cold Packs
The most commonly used instant cold packs compose of ammonium nitrate and water. The two components are separated in two compartments. When activated, the two are mixed to adsorb heat from the environment and cause the temperature drop. Since ammonium nitrate is also used in agriculture as a fertilizer, it is not very harmful to health. However, it is an oxidizer so it is subject to transportation hazard material regulations. Also, it can be used to make explosives increasing its potential for misuse. Because of safety concerns and shipping restrictions, some manufacturers have avoided using ammonia nitrate to make cold packs. Calcium ammonia nitrate (CAN) is a safer alternative in terms of chemical stability.
Urea based cold packs become a popular alternative in recent years, which is accepted as safe and environmentally friendly. Because of its low ratings in reactivity and flammability, it is not subject to shipping restrictions. With a similar heat-adsorbing characteristics when combining with water, it demonstrates the ability for effective cooling by reaching the desired temperature in a short time and lasting for long.
Reusable Cold Packs
Unlike instant cold packs which can be activated within seconds, reusable cold packs need to be stored in refrigerator for several hours before using. Reusable packs are made with the main component of water. Water has a high heat capacity, which means it can adsorb much more heat than most materials within the same temperature change. The biggest problem associated with pure water is that it will solidify under 0 degrees Celsius. To achieve a lower freezing point, safe anti-freezers like glycerol or propylene glycol are added in water. This will ensure the liquid phase of the cold pack at low temperatures, making it easily wraps objects requiring cooling. In some reusable cold packs, non-toxic thickening agent like cellulose, polyacrylate or silica gel are added to make the liquid a slow-flowing gel, some of which also have the benefits of lowering mixture freezing point at the same time.
Since these cold packs are mainly used for food and drinks and once leaked, they might contaminate the food. Therefore, additives should be used with caution with assessment of toxicity. Some common anti-freezers for industrial application with potential hazards such as diethylene glycol and ethylene glycol are not suitable and banned in the use of cold packs.
For more experiments and facts about cold packs and how to use them, here are some you might find useful:
Dawn Breeze proudly offers safe cold pack products for global brands. All the products are made in manufacturing facilities with CE certification, FDA registration, BSCI audit and SGS test reports.