Fluorine, Water Tension, and Fabric

name         Nathan
status       other
grade        other
location     CO

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?
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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.

Vince Calder
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