Ice pack
Anice packorgel packis a portable bag filled with water, refrigerantgel,or liquid, meant to provide cooling. They can be divided into the reusable type, which works as athermal massand 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 acold compressto alleviate the pain of minor injuries, while the reusable type is both used as a cold compress and to keep food cool in portablecoolersor ininsulated shipping containersto keep products cool during transport.[1]
Reusable packs
[edit]To be prepared for use, the pack is first placed in a freezer. Bothiceand othernon-toxicrefrigerants (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 zonewhen 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, thethermal insulationof 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 addinghydroxyethyl cellulose,[2]sodium polyacrylate,superabsorbent polymeror vinyl-coatedsilica 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 nameHot-R-Cold-Pakand 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 amicrowave ovenwas first patented[4]in 1973.
Instant ice packs
[edit]Aninstant cold packis a single-use device that consists of two bags; one containingwater,inside a bag containingammonium nitrate,calcium ammonium nitrateorurea.When the inner bag of water is broken by squeezing the package, it dissolves the solid in anendothermic process.This process absorbs heat from the surroundings, quickly lowering the pack's temperature.[5]
Instant cold packs are a convenient replacement for crushediceused asfirst aidonsport injuriesorheat 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
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Gel packs have been made withdiethylene glycolandethylene glycol.Both can cause illness if ingested in large amounts,[7]making them unsuitable for use with food. The USConsumer Product Safety Commissionrecalledsuch packs.[7]
See also
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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.S2CID14036303.Retrieved10 June2024.
- ^"Versa-Pac™ Reusable Heavy Duty Cold Pack"(PDF).Unipatch: Material Safety Data Sheet.Tyco. February 2004. Archived fromthe original(PDF)on December 30, 2006.Retrieved2009-06-01.
- ^"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:// nortechlabs /nortech-history.html]
- ^Marshall Brain (29 November 2006)."Cold Packs".How Refrigerators Work.Howstuffworks.
- ^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.PMC1725271.PMID16046331.
- ^ab"California Innovations Expands Recall of Freezer Gel Packs Due to Ingestion Hazard".CPSC.gov.Retrieved2014-08-06.