Cd. Volpe et S. Siboni, ANALYSIS OF DYNAMIC CONTACT-ANGLE ON DISCOIDAL SAMPLES MEASURED BY THE WILHELMY METHOD, Journal of adhesion science and technology, 12(2), 1998, pp. 197-224
Contact angle measurements have been performed using the Wilhelmy micr
obalance on disc-shaped samples of different thicknesses and these are
compared with the theoretical analysis proposed by Dryden and Andrade
(D-A). In disagreement with the original D-A results, our conclusion
is that not only are the force values well reproducible, but also the
determination of the contact angles, by inverting the force equations,
provides acceptable estimates. This conclusion is supported by the an
alysis of error propagation for the various physical and geometrical p
arameters of the model. By taking into account the thickness of the sa
mples a correction is introduced, the significance of which is analyse
d with respect to some of the experimental parameters. Moreover, a sec
ond method of analysis based on an iterative procedure is proposed; it
uses only the force data collected during the immersion of the diamet
er zone of the disc samples and can be applied to both discoidal (e.g.
lenses) and plane disc-shaped samples. Finally, an accurate analysis
of the meniscus shape during the immersion leads to a third method for
the estimation of contact angles on discs. It requires the detection
of the immersion level at which the lateral meniscus becomes perfectly
planar. Its use is restricted to the case of thick discs and the prec
ision achieved is not high.