High-energy UV photons are able to break up molecular organic bonds at and on surfaces.
The opened bonding sites strive to return to a chemically stable condition as quickly as possible.
Reaction partners may be atmospheric oxygen or ozone formed from ambient oxygen due to the UV radiation. The open bonds are saturated by the atoms and radicals formed from them and new compounds are created on the surface.
As a consequence of the UV treatment in normal ambient atmosphere, the formation of hydroxyl, carbonyl and/or carboxyl groups can be proven by means of ATR and XPS measurements. This gives the surfaces a higher polar character which has an effect on both the contact angle and the surface energy.