How can changes to a substrate surface be monitored?
The contact angle of a liquid (typically deionized water) on the surface of the substrate can be measured. Deionized water is used because it is Newtonian, has a low vapor pressure (minimal evaporation during testing), and has minimal interaction with most surfaces. Contact angle is inversely proportional to surface energy of the substrate. Therefore, a lower water contact angle signifies a relatively higher surface energy of the substrate, which typically correlates to higher adhesion between the adhesive and substrate. A higher water contact angle signifies a relatively lower surface energy of the substrate, which typically correlates to lower adhesion between the adhesive and substrate.
