Kulim Kht Washburn Method

Washburn Method
This method is chosen when the solid sample to be tested contains a porous architecture which leads to
absorption of the wetting liquid. The solid is brought into contact with the testing liquid and the mass of
liquid absorbed into the solid is measured as a function of time. The amount absorbed is a function of the
viscosity, density and surface tension of the liquid, the material constant of the solid , and the contact angle
of the interaction. If the viscosity, density and surface tension of the liquid are known the material constant
and contact angle can be solved for. KSV instruments produces two instruments capable of finding contact
angles via the Washburn technique, the Sigma 70 and LPR 902. See Application Note #104 for details.

Utilization of Contact Angle Data:
The primary focus of contact angle studies is in assessing the wetting characteristics of solid/liquid
interactions. Contact angle is commonly used as the most direct measure of wetting. Other experimental
parameters may be derived directly from contact angle and surface tension results. Some examples are:
Work of Adhesion: defined as the work required to separate the liquid
and solid phases, or the negative free energy associated with the
adhesion of the solid and liquid phases. Used to express the strength
of the interaction between the two phases. It is given by the Young
-Dupre equation as:
Wa = (1+ cos )
Work of Cohesion: defined as the work required to separate a liquid into
two parts, it is a measure of the strength of molecular interactions
within the liquid. It is given by;
Wc = 2
Work of Spreading: the negative free energy associated with spreading
liquid over solid surface. Also referred to as Spreading Coefficient
it is given as:
Ws = (cos - 1)
Wetting Tension: a measurement of force/length defined as:
= Fw / P = lv cos