Department of Energy Argonne National Laboratory Office of Science NEWTON's Homepage NEWTON's Homepage
NEWTON, Ask A Scientist!
NEWTON Home Page NEWTON Teachers Visit Our Archives Ask A Question How To Ask A Question Question of the Week Our Expert Scientists Volunteer at NEWTON! Frequently Asked Questions Referencing NEWTON About NEWTON About Ask A Scientist Education At Argonne Hydrogel For Cooling
Name: Susilo
Status: Other
Age: 20s
Location: N/A
Country: N/A
Date: July 2004

There is a new kind of plaster that has the so-called "hydrogel" to help children cool down their fever. The plaster is a piece of textile materials with the hydrogel on it and when used, it is put on the children's forehead. the cooling period of the hydrogel plaster can last for 2 hours. I want to know what possibly it is made of and whether this product is dangerous to the skin. As for country of origin of this product, it is either Japan of Taiwan.

The term "hydrogel" refers to a class of substances that absorb and retain a large amount of water. Chemically they can be insoluble polymers of hydroxyethyl acrylate, acrylamide, polyethylene oxide, and others. As a cooling aid they work by exposing the absorbed water to a large surface area. Since the heat of vaporization of water is about 0.6 kilocalories per gram (that is large) a cooling effect occurs. If the product is sold in the U.S. for medicinal purposes it (to be legal) must meet certain Food and Drug Administration (FDA) regulations as being safe and effective. That does not mean that an individual might not be allergic to the product. For example latex gloves and talc treated gloves are sold even though some people are very sensitive to those products. In that case the package is supposed to carry a warning label. Assuming the hydrogel meets the FDA regulations (regardless of the country of origin) it should be safe. Similar substances have been used in baby diapers for years.

Vince Calder

There are two kinds of hydrogels. Both start as water combined with a special polymer. The sheet hydrogels use crosslinked polymers to give them a definite shape. The amorphous category has no definite shape and is not crosslinked. The gel contains 70-95% water. The gel can be used to moisten an area, or to absorb some water. The cooling effect arises because the material is mostly water, and water has high heat capacity. Some hydrogels contain small amounts of other materials to boost their performance in a specific area. They are considered to be non-toxic. At least two dozen gels are marketed under various trade names.

Bob Erck

Click here to return to the Engineering Archives

NEWTON is an electronic community for Science, Math, and Computer Science K-12 Educators, sponsored and operated by Argonne National Laboratory's Educational Programs, Andrew Skipor, Ph.D., Head of Educational Programs.

For assistance with NEWTON contact a System Operator (, or at Argonne's Educational Programs

Educational Programs
Building 360
9700 S. Cass Ave.
Argonne, Illinois
60439-4845, USA
Update: June 2012
Weclome To Newton

Argonne National Laboratory