At present the most widely used technique for determining contact angle (Ø) is by the direct measurement of angle from the drop profile using a goniometer.
The Young-Dupré equation relates the work of adhesion Wa, or bonding energy, directly to the surface tension of the liquid, γLV, and the contact angle, Ø, that the liquid makes with the solid.
Wa = γLV (1 + cos Ø) dynes/cm
Smithers Pira uses a PG-3 Pocket Goniometer not only to measure the static contact angle, but also the volume and spread of a drop of liquid on the surface over time. This dynamic absorption test (DAT) is applied to test the liquid absorbency of paper or board. DAT can be used to determine the degree of sizing or water hold out of paper with time.
Standards and Accreditation
The PG-3 Pocket Goniometer satisfies the requirements of international standards ASTM D5725 and TAPPI T558.