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Name: Susilo
Status: Other
Age: 20s
Location: N/A
Country: N/A
Date: July 2004


Question:
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.



Replies:
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



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