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.
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