How is Plasma Treatment Measured?
Posted by Kevin Smith on Wed, Jul 07, 2010 @ 08:51 AM
The effects of plasma surface modifications are most often expressed in terms of wettability. The hydrophobicity or hydrophilicity of a surface is often an accurate measure of the effectiveness of plasma modifications.
The wettability of a surface is measured by contact angle using an instrument called a Contact Angle Goniometer. The contact angle is the measure of the tangent of a drop of a liquid in relation to the surface and expressed in degrees. A high contact angle (i.e.: 90') indicates a non-wettable surface, while a low contact angle (i.e.: 20') indicates a highly wettable surface. An analogy would be a freshly waxed automobile versus an unwaxed one. The former, when wet, beads up (a high contact angle) and the latter is wetted uniformly with no breaks in the water (a low contact angle).
Distilled water is the liquid most often used for measuring contact angle. It was chosen because it is high in purity, has no electrical charge, and does not interact with most surfaces.
It is standard procedure to record contact angles of materials and/or devices before and after plasma treatments to determine the change in the surface and to monitor polymer changes from batch to batch. Often, faults and contamination problems in the untreated polymer are detected by a variation in the normal contact angle of a substrate. Our engineers are able to assist a customer in the identification and correction of a polymer compound problem which has been discovered via contact angle measurement.
If you have any questions or comments, please share them with us.