There are many everyday situations, in the home or at work, where a liquid will come in contact with a solid surface. When it does, what you don’t want is for the liquid not to stick to the surface of a solid when it should or vice-versa. How well a solid forms a connection between the surface and the liquid describes its wettability. To find the wettability of a solid involves measuring its contact angle value. Understanding what the contact value means, it’s necessary to define what it is, why it’s important, and how you measure it.
What is Contact Angle Measurement?
The contact angle is a way of measuring how well a liquid wets a solid. Such a measurement indicates how a product will perform or show how successful a process is likely to be. It defines the angle between the boundary formed by the solid, a liquid and the gas phase.
If you place a liquid on a solid surface and it runs evenly then complete wetting is present. In this situation, the contact angle is 0 degrees. If the surface can be wetted, then the contact angle falls between 0 and 90 degrees. Such a surface is hydrophilic.
On the other hand, if it falls between 90 and 180 degrees, it’s not wettable and is a hydrophobic surface. Where the surface completely repels a liquid, the contact angle is close to 180 degrees. The difficulty of getting such a surface wet makes it an ultrahydrophobic surface.
Why is it important?
Being able to measure the contact angle and how it might apply to your situation is vital. The reason is that if you require paints, coolants and varnishes you want to know how well they wet a surface. What you don’t want, for example, is for the paint to run off a wall and not stick to it. That’s why knowing the contact angle helps in everyday situations.
The contact angle provides a means for assessing the suitability of various liquids on different materials. Finding the contact angle of a liquid on a surface makes sure that the interaction between the two is at its best level.
Making sure that a solid can handle a liquid (its wettability) will require technology. To understand the importance of the contact angle, find out about technology for surface measurement.
Measuring techniques
When a solid and a liquid come into contact, it’s helpful to know how well the liquid wets the surface. Will the liquid run completely off the solid, will it form droplets or will it pool on the surface? To find the answer to these questions means measuring the contact angle between the liquid and the solid. There are several ways of measuring the contact angle. These include:
- Drop shape analysis
- Wilhelmy plate method
- Top-view distance method
- Washburn’s equation
Being able to measure how a liquid spreads on a surface means knowing the contact angle measurement. It offers a way of working out how suitable a solid will be in everyday situations when in contact with a liquid. With the right technology for measuring the angle, you can avoid situations where a product that is supposed to be water repellent, becomes soaked because it retains the liquid.
