Name: Nathan
Status: Other
Grade: Other
Location: CO
Country: USA
Date: July 2006
Question:
When fluorine is used to repel water on fabrics
such as DWR-Durable Water Repellency (a topical surface treatment
used on garments), is it increasing or decreasing the surface
tension on the fabric?
Replies:
Fluorine (the element) is not used to make fabrics water repellant.
Fluorine is a toxic, corrosive gas. What is used are compounds
formed between carbon fluorine and occasionally other elements,
generically referred to as "fluorocarbons". The fluorine atoms in
these compounds hold on to their electrons very tightly, so they are
not able to be attracted to other molecules such as water. As a
result the surface tension of the fabric coated with the
fluorocarbon is decreased. This causes the water molecules, which
already like to associate with one another, do so even more when in
contact with the fluorocarbon. The result is that the water "beads
up" and flows off the fabric rather than being attracted to the fibers.
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