Thank you for your question.
A page from Tyco Healthcare on their reusable hot and cold packs show
the following as the composition of the gel:
Water, Table Salt 96%
Blue Coloring Dye (food grade)
Ucarcide (250 preservative) 0.05%
Their heavy duty reusable cold pack shows the following:
Non-Hazardous Ingredients > 99%
So, what we have is salt water, coloring and cellulose added to create
the "body" of the gel with a bit of preservatives.
Ucarcide is described as follows at Dow chemicals:
UCARCIDE 250 Preservative
UCARCIDE? 250 Preservative is a broad spectrum biocide, which is
highly effective against bacteria, fungi and yeast. It is effective
over a broad pH range and exhibits high efficacy at low
A page at the DiLorenzo Tricare Health Clinic describes a method for
home made gel packs:
"... It is also easy and inexpensive to make your own cold pack: mix
one-third cup of rubbing alcohol with two-thirds cup of water in a
reclosable plastic bag. Put the bag in the freezer until the mixture
forms a slush. The homemade pack is ready to use. It can be
refrozen and reused a number of times..."
There are a number of companies that claim proprietary formulas for
their gel packs that make claims of higher performance, lower
temaprtures, better flexibility and/or longer cold retention, but they
do not disclose their added ingredients online and a patent search is
a tad outside the scope of this question. Suffice to say, most
compositions of the gel will include salt, water, coloring, cellulose
and preservative as their main ingredients.
For example, Nortech Labs says about their gel:
"...Ice Brick Shipping Pack utilizes Nortech's proprietary lightweight
formula that freezes quicker and stays colder longer than standard gel
formulations. When compared to standard gel formulations, on a volume
basis, Nortech's proprietary lightweight formula is 3 to 5 % lighter
in weight without sacrificing cooling efficiency..."
Their formula remains a secret however.
You might also be interested to read this page on the science behind
chemical reactions to produce hot or cold:
Although this is slightly different than the packs we have been
discussing which can retain cold, these will actually generate it for
one time use.
"...Chemicals can store energy and release it in the form of heat. A
chemical reaction that releases heat is called an exothermic reaction.
But chemical reactions can also absorb heat from the environment and
get cold. These reactions are called endothermic reactions. When
chemicals are dissolved in water, sometimes heat is released, and
sometimes heat is absorbed.
Heat is given off as a result of a chemical reaction. Hot/cold packs
are used by athletes to minimize swelling of injuries such as muscle
and joint sprains. They are constructed of a large pouch containing a
dry chemical plus an inner pouch of water. The hot/cold pack is
activated by breaking the seal on the pouch of water and shaking the
pack vigorously. This action mixes the water with the chemical
starting the exothermic or endothermic reaction..."
A page on chemical reactions from Deakin University in Australia notes:
"...A good example of an endothermic reaction is the use of an instant
icepack. Instant ice packs may be used to treat minor burns as well as
sporting injuries such as sprains. A typical cold pack contains the
ionic compound ammonium nitrate sale (NH4NO3) which reacts with water.
In solution (the ionic solid has dissolved in water) the ionic bonds
are broken, freeing up ammonium ions (NH4+) and nitrate ions (NO3-).
During the reaction, energy is taken from the surrounding environment
(for example, the ankle) thus cooling it down. The equation for the
NH4NO3 Water NH4+ + NO3- ..."
And one more unique variation that is both an instant cooler AND a
resusable is made by Dual Ice:
"...DUAL-ICE? utilizes a unique combination of ammonium chloride, urea
and bufferring agents to create the chemical reaction. All of these
products are non-toxic, and the combination of them results in a
liquid that remains non-toxic and is no more acidic than an egg
...New DUAL-ICE? is the first completely Non-Toxic, Non-Caustic,
rugged Instant Cold Compress on the market. DUAL-ICE? cools instantly
upon activation to 24 degrees F and stay cold for up to 30 minutes
after activation. DUAL-ICE? was first developed for the U.S. Armed
Services to meet the requirement for a Non-Toxic, Non-Caustic, heavy
duty Instant Cold Compress. DUAL-ICE? has been deployed by the U.S.
Marine Corps and Special Operations forces. You can also view our
product writeup featured in the October 23-25 USA Weekend/USA Today!
What also makes DUAL-ICE? unique is that they are the first Instant
Cold Compresses that you can actually reuse! Not as an Instant Cold
Compress, of course (our technology hasn't gotten that far), but as a
refreezable Cold Pack. After it's initial use as an Instant Cold
Compress, don't throw the DUAL-ICE? away; you can place it in your
freezer and, after a few hours, the chemical content will reconstitute
into a flexible 16 degree F slurry (allowing it to conform to the
injured part of the body) which will stay cold for up to 30 minutes.
A perfect reusable cold pack that may be refrozen, basically, until
the tough 3-mil nylon/poly overwrap that encloses the chemicals wears
out! And, according to our laboratory testing, that takes a LONG
Interesting application and seems to be unique to this brand of cold pack.
"cold pack" +gel +properties OR composition OR chemical
"cold pack" +gel +ingredients
"cold pack" +gel +contains OR contents OR formula
I trust my research has provided you with information on cold pack gel
compostions. If a link above should fail to work or anything require
further explanation or research, please do post a Request for
Clarification prior to rating the answer and closing the question and
I will be pleased to assist further.