1. 界面科学測器の協和界面科学
  2. Kyowa Interface Science
  3. Interface Science
  4. What is Contact Angle?

What is Contact Angle?

What is Contact Angle?_1
What is Contact Angle?_2

θ/2 method

Measurement of the static contact angle_1
Measurement of the static contact angle_2

Tangent method

Tangent method

Curve fitting method

Sessile Drop method in time function

Extension/Contraction method

Extension/Contraction method

Sliding method – measurement on a slope

Sliding method – measurement on a slope

Wilhelmy method

Wilhelmy method_1
Wilhelmy method_2

F…Forces acting on the solid sample (measured)
γ…Liquid sample surface tension (must be known in the case of contact angle measurements)
L…Solid sample perimeter (must be known)
θ…The contact angle between the liquid sample and the solid
sample (assumes 0 ° when measuring the surface tension)
S…Cross-sectional area of the solid sample distance
h…Solid sample immersion distance
ρ…Liquid sample density
g…Gravitational acceleration

Wilhelmy method_3

Since buoyancy increases and the sample immersed in the liquid level is raised, F the force acting on the balance is reduced.
In addition, the buoyancy is reduced and when lowering the liquid surface, F increases. In this manner, the liquid level rises. The position of the liquid surface represents the relationship between the force acting on the balance and when lowered, is shown on the right.

Infiltration Rate method

Infiltration Rate method_1

l…Liquid Penetration Height
t…Time
r…Capillary radius of the filling powder
γ…Surface tension of the liquid
η…Viscosity of the liquid
θ…Contact angle

Infiltration Rate method_2

In actual measurement, a liquid sample is infiltrated into a column filled with powder, and the change in the weight W is tracked for the elapsed time t. Ideally, the linear relationship is obtained by plotting t for W2. The contact angle and infiltration rate is calculated from the slope of this line. In addition, in order to calculate the contact angle, for the powder-filled capillary radius value is required besides the values of liquid surface tension and viscosity. That capillary radius value is determined experimentally by measuring the sufficiently wet liquid for the powder and regarding the contact angle as 0°.

Infiltration Rate method_3
Infiltration Rate method_4

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