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Ice pack
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An ice pack or gel pack is a portable bag filled with water, refrigerant gel, or liquid, meant to provide cooling. They can be divided into the reusable type, which works as a thermal mass and requires freezing, or the instant type, which cools itself down using chemicals but can only be used once. The instant type is generally limited to medical use as a cold compress to alleviate the pain of minor injuries, while the reusable type is both used as a cold compress and to keep food cool in portable coolers or in insulated shipping containers to keep products cool during transport.[1]
Reusable packs
[edit]To be prepared for use, the pack is first placed in a freezer. Both ice and other non-toxic refrigerants (mostly water) can absorb a considerable amount of heat before they warm above 0 °C (32 °F).`
Ice packs are used in coolers to keep perishable foods (especially meats, dairy products, eggs, etc.) below the 5–75 °C (41–167 °F) danger zone when outside a refrigerator or freezer, and to keep drinks pleasantly cool. The amount of ice needed varies with the amount of food, its initial temperature, the thermal insulation of the cooler, and the ambient temperature and exposure to direct sunlight. Ice initially well below freezing temperature will last a little longer.
Water has a much higher latent heat of fusion than most substances, and a melting temperature which is convenient and easily attained with, for example, a household freezer. Additives to improve the properties of water are often used. For example, substances can be added to prevent bacterial growth in the pack, or to prevent the water from solidifying so it remains a thick gel throughout use.
Gel packs are often made of non-toxic materials that will remain a slow-flowing gel, and therefore will not spill easily or cause contamination if the container breaks. Gel packs may be made by adding hydroxyethyl cellulose,[2] sodium polyacrylate, superabsorbent polymer or vinyl-coated silica gel.
Hot-or-cold packs
[edit]Hot-or-cold packs are ice packs that are rated for high temperature use. They can be used as a normal reusable ice pack by storing in a freezer, but they can also be heated in water or a microwave oven to reach the desired temperature. The first hot and cold pack was introduced in 1948 with the name Hot-R-Cold-Pak and could be chilled in a refrigerator or heated in hot water.[3] The first reusable hot cold pack that could be heated in boiling water or a microwave oven was first patented[4] in 1973.
Instant ice packs
[edit]An instant cold pack is a single-use device that consists of two bags; one containing water, inside a bag containing ammonium nitrate, calcium ammonium nitrate or urea. When the inner bag of water is broken by squeezing the package, it dissolves the solid in an endothermic process. This process absorbs heat from the surroundings, quickly lowering the pack's temperature.[5]
Instant cold packs are a convenient replacement for crushed ice used as first aid on sport injuries or heat illness, and can be carried as first aid to remote or wilderness areas where ice is unavailable. However, they do not provide as much or as long-lasting cooling as ice.[6]
Safety concerns
[edit]
Gel packs have been made with diethylene glycol and ethylene glycol. Both can cause illness if ingested in large amounts,[7] making them unsuitable for use with food. The US Consumer Product Safety Commission recalled such packs.[7]
See also
[edit]
Wikimedia Commons has media related to Ice packs.
References
[edit]- ^ Singh, S P; Burgess, Singh (2008). "Performance Comparison of Thermal Insulated Packaging Boxes, Bags and Refrigerants for Single-parcel Shipments". Packaging Technology and Science. 21: 25–35. doi:10.1002/pts.773. S2CID 14036303. Retrieved 10 June 2024.
- ^ "Versa-Pac™ Reusable Heavy Duty Cold Pack" (PDF). Unipatch: Material Safety Data Sheet. Tyco. February 2004. Archived from the original (PDF) on December 30, 2006. Retrieved 2009-06-01.
- ^ "To Warm or Cool You." Popular Science, August 1948, p. 138.
- ^ Nortech Labs History - Patent of Reusable Hot Cold Pack, Dec. 25, 1973, Patent No. 3,780,537 [Nortech Labs History | http://www.nortechlabs.com/nortech-history.html]
- ^ Marshall Brain (29 November 2006). "Cold Packs". How Refrigerators Work. Howstuffworks.com.
- ^ Smith, Jason E. (2005). "Cooling methods used in the treatment of exertional heat illness". British Journal of Sports Medicine. 39 (8): 503–507. doi:10.1136/bjsm.2004.013466. PMC 1725271. PMID 16046331.
- ^ a b "California Innovations Expands Recall of Freezer Gel Packs Due to Ingestion Hazard". CPSC.gov. Retrieved 2014-08-06.
Ice pack
View on Grokipediafrom Grokipedia
Overview
Definition and Purpose
An ice pack is a compressible bag or pouch typically filled with ice, gel, or chemical agents, engineered to deliver localized cooling for therapeutic purposes. It functions by absorbing heat from the body through direct contact, thereby lowering tissue temperature in the applied area. This device is widely used in medical and home settings as a form of cryotherapy to address acute conditions without requiring specialized equipment.[10][11] The primary purposes of ice packs include providing temporary relief from inflammation, minor injuries such as sprains or bruises, fever reduction, and aiding post-surgical recovery. By inducing vasoconstriction—narrowing of blood vessels—the pack reduces blood flow to the site, which minimizes swelling and bleeding while numbing nerve endings to alleviate pain. Additionally, the cooling effect decreases the metabolic rate in affected tissues, limiting secondary tissue damage from inflammation and promoting faster initial recovery. This heat transfer occurs primarily via conduction, where thermal energy moves from the warmer body to the colder pack.[8][12][13] Ice packs offer several key benefits, including being non-invasive, portable for on-the-go use, and cost-effective relative to pharmaceutical or clinical interventions. Their physiological impacts, such as reduced inflammation and pain without systemic side effects, make them a first-line option for managing acute injuries. In design, ice packs often incorporate flexible materials like gel-filled vinyl or plastic that conform to body contours for even cooling distribution, and they are commonly paired with outer fabric covers to prevent direct skin contact and avoid risks like frostbite.[11][14][15]Historical Development
The use of cold therapy for treating injuries dates back to ancient civilizations. As early as 2500 BCE, ancient Egyptians applied natural ice or snow, often wrapped in cloth, to reduce inflammation and alleviate pain from wounds.[16] Similarly, ancient Greeks employed snow and ice for similar purposes, with the physician Hippocrates documenting in his texts around 400 BCE the application of cold compresses to control bleeding, reduce swelling, and numb injuries, recognizing its analgesic and anti-inflammatory effects.[3][17] In the 19th century, advancements in materials enabled more practical cold therapy devices. During the mid-1800s, rubber-based insulated bags emerged for medical cooling, allowing safer and more controlled application of ice compared to loose wrappings; these were notably used by surgeons like Friedrich von Esmarch, a German military physician, to treat battlefield injuries during conflicts such as the wars against Denmark and France.[18] In the United States, ice played a critical role in Civil War battlefield first aid from 1861 to 1865, where it was transported via rail and applied to wounds, fractures, and fevers to combat inflammation and infection, marking early commercial-scale distribution for medical use.[19] The 20th century brought significant innovations in portable and reusable designs. In 1948, the first hot-and-cold pack, known as Hot-R-Cold-Pak, was introduced; it could be chilled in a refrigerator or heated in water and was developed for versatile therapeutic applications, including by the U.S. military for injury management. Building on this, gel-based reusable packs gained prominence in the 1970s, with Jacob Spencer patenting the first versatile medical version in 1971, featuring a neutral gel in a sealed envelope for repeated freezing and safe skin contact.[4] Instant chemical packs also emerged around this time, with Albert A. Robbins securing a patent in 1959 for an early endothermic reaction-based design initially for food cooling, later adapted for medical use through Spencer's refinements.[20] In the post-2000 era, ice pack technology has focused on enhanced performance and sustainability. Phase-change materials (PCMs) were integrated into designs starting in the early 2000s to provide consistent temperature control over extended periods, improving efficacy for therapeutic and transport applications by maintaining a stable cooling phase without constant refreezing.[3] Concurrently, environmental concerns have driven the development of eco-friendly options, such as biodegradable gel packs using plant-based, non-toxic formulations that decompose without harmful residues, with commercial products like TerraTemp and Cryopak Eco Gel becoming widely available by the 2020s to reduce plastic waste in medical and shipping contexts.[21][22]Types of Ice Packs
Traditional Ice Packs
Traditional ice packs are constructed by placing crushed or cubed ice into a sealable plastic bag or directly into a cloth, towel, or sock, then wrapping the bundle in an additional thin layer of fabric to create a barrier against the skin.[1][23] These packs rely solely on frozen water as the cooling agent, without any chemical additives, making them a basic, non-engineered option for cold therapy. Crushed ice is preferred over cubes because it conforms more easily to body contours and remains in place during application.[1] Preparation involves either freezing water in a container to produce ice cubes or using pre-made ice from a freezer or ice machine, which can be done in households or outdoor settings with access to refrigeration. The pack typically provides cooling for 10 to 20 minutes before the ice begins to melt significantly, after which it may need refilling or replacement to maintain effectiveness.[1][24][23] These ice packs offer advantages such as low cost and high accessibility, as they can be assembled quickly using everyday items like ice trays, bags, and towels found in most homes or available from nearby sources.[1][24] They pose no risk of chemical leaks, providing a safe, natural alternative for basic cooling needs.[23] However, traditional ice packs have limitations, including the necessity of a freezer or ice source for preparation, which restricts their use in remote or non-refrigerated environments. They are susceptible to leakage as the ice melts, potentially causing mess, and may deliver uneven cooling if the ice shifts within the wrapping. Additionally, they lack portability for extended use without ongoing access to refrigeration.[1][24][23] Common variants include filling a clean sock with crushed ice and tying it closed for a flexible, moldable pack, or using a bag of frozen vegetables such as peas or corn as an improvised alternative that conforms well to irregular shapes. Frozen vegetables can be thawed and consumed afterward, adding to their practicality in household settings.[1][23] These options enhance accessibility when standard ice is unavailable.Reusable Gel Packs
Reusable gel packs typically contain a mixture that remains flexible when frozen, often based on propylene glycol, water, and gelling agents for a moldable cold therapy application. Earlier or some disreputable formulations used ethylene glycol for its superior freezing point depression, but this was discontinued due to severe toxicity risks if the pack leaks and the contents are ingested; multiple international recalls in the late 2000s and early 2010s addressed products containing ethylene or diethylene glycol.[25][26] In manufacturing, these packs are sealed within non-toxic, BPA-free materials to prevent leaks and ensure durability, with designs ranging from small sizes suitable for targeted areas like the eyes to larger formats for broader coverage such as the back.[27] Popular brands like FlexiKold feature double-seamed nylon exteriors that enhance longevity and flexibility.[28] Functionally, reusable gel packs freeze at approximately 0°C (32°F) due to the gel's composition, delivering consistent cooling for 20-40 minutes during therapy sessions.[29] Dual-use variants can be heated via microwave or immersion in hot water for heat therapy, providing versatility for both cold and warm applications without compromising the gel's integrity.[30] Key advantages include their moldability to conform to body contours for effective contact, reusability for hundreds of cycles, and ability to sustain a steady therapeutic temperature longer than traditional ice, reducing the need for frequent replacement.[31][32][33] For maintenance, clean the packs with mild soap and water after use, then air dry before storage in a freezer to preserve the gel's properties; with proper care, they typically last 1-3 years.[34][35]Instant Chemical Packs
Instant chemical packs, also known as instant cold packs, are single-use devices that provide immediate cooling through an endothermic chemical reaction without the need for pre-freezing or refrigeration. These packs typically consist of an outer plastic bag containing ammonium nitrate crystals and an inner pouch filled with water. When the inner pouch is ruptured by squeezing or striking the pack, the water mixes with the ammonium nitrate, initiating the dissolution process that absorbs heat from the surroundings.[36][37] The chemical reaction is the endothermic dissolution of ammonium nitrate in water, represented by the equation:
This process absorbs heat, causing the temperature of the pack to drop rapidly to between 20°F and 40°F (-7°C to 4°C) within seconds. Some formulations use urea instead of ammonium nitrate for similar endothermic effects. The cooling lasts for 15 to 30 minutes, after which the pack is disposed of as it cannot be reactivated.[38][39][40]
The invention of instant chemical packs traces back to the late 1950s, when Albert A. Robbins patented a chemical freezing package in 1959 (US Patent 2,898,744) primarily for cooling food and beverages. By the 1970s, adaptations for medical applications had emerged, leading to widespread inclusion in first aid kits by the 1980s. In the 2010s, eco-friendly variants using urea as an alternative to ammonium nitrate gained popularity due to reduced environmental and safety concerns associated with the latter.[41][42]
These packs are available in various sizes and forms, including small pouches suitable for treating localized injuries like sprains and larger bags designed for use in coolers or broader cooling needs.[43]