Static Contact Angle

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Definition - What does Static Contact Angle mean?

A static contact angle is the contact angle formed when the three phase boundary is not moving, and the droplet is standing on the surface. In a pure liquid in the saturated vapor phase on an ideal surface, the static and dynamic contact angle would be equal. In reality and ambient conditions, the contact angle varies as a function of time and location.

The static contact angle is determined by the properties of the solid material and the liquid it carries. The inter-molecular forces of cohesion and adhesion determine the contact angle created.

Trenchlesspedia explains Static Contact Angle

When the static contact angle is less, the adhesive forces are stronger and the liquid molecules interact more with the solid molecules than the liquid ones. When the static contact angle is large, the cohesive forces are stronger and the liquid molecules interact more among themselves than with the solid molecules.

A static contact angle can be measured using optical and force tensiometry, Sessile drop method, Wilhelmy plate method and capillary rise method. Contact angle also determines the wettability of a solid and is very important in sewer and water pipe manufacturing. Pipes that do not have the appropriate contact angle with the liquid they carry can be rehabilitated using trenchless methods such as cured-in-place pipe (CIPP), sliplining and pipe bursting.

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